Skip to main content

Hypoxic exosomes orchestrate tumorigenesis: molecular mechanisms and therapeutic implications

Abstract

The solid tumor microenvironment possesses a hypoxic condition, which promotes aggressiveness and resistance to therapies. Hypoxic tumor cells undergo broadly metabolic and molecular adaptations and communicate with surrounding cells to provide conditions promising for their homeostasis and metastasis. Extracellular vesicles such as exosomes originating from the endosomal pathway carry different types of biomolecules such as nucleic acids, proteins, and lipids; participate in cell-to-cell communication. The exposure of cancer cells to hypoxic conditions, not only, increases exosomes biogenesis and secretion but also alters exosomes cargo. Under the hypoxic condition, different signaling pathways such as HIFs, Rab-GTPases, NF-κB, and tetraspanin are involved in the exosomes biogenesis. Hypoxic tumor cells release exosomes that induce tumorigenesis through promoting metastasis, angiogenesis, and modulating immune responses. Exosomes from hypoxic tumor cells hold great potential for clinical application and cancer diagnosis. Besides, targeting the biogenesis of these exosomes may be a therapeutic opportunity for reducing tumorigenesis. Exosomes can serve as a drug delivery system transferring therapeutic compounds to cancer cells. Understanding the detailed mechanisms involved in biogenesis and functions of exosomes under hypoxic conditions may help to develop effective therapies against cancer.

Background

Hypoxia, a condition of insufficient oxygen, is a common feature of numerous solid tumors, related to tumor development, therapy resistance, and mortality [1]. Tumor cells in the microenvironment encounter low oxygen levels because of insufficient oxygen flow and physiological anomalies in tumor vessels, resulting in normoxic, hypoxic, and also necrotic regions [2]. In most solid tumors, the average concentration of oxygen is near 10 mmHg, whereas in the other tissues it reaches 40 and 60 mmHg [3]. Tumor cells juxtaposed to the normal vessels are functional, whereas cells situated around 150 μm from the vasculature bed may undergo necrosis and atresia [4], however, cells are located between these two cell populations habituate to an insufficient oxygen environment, hypoxia. Generally, cells located in a diameter of approximately 1 mm undergo genetic, molecular, and metabolic changes. These cells could reorganize the microenvironment appropriate for growth, metastasis, and therapy resistance [5]. In this situation, by the production of pro-angiogenic factors, tumor cells can induce angiogenesis for supplying nutrients and oxygen and removing waste. Besides, increased angiogenesis in tumor mass provides a way for tumor cells to migrate and metastasize [6].

In response to a hypoxic condition, the transcription profile of tumor cells such as hypoxia-inducible factors (HIFs), the key factor involved in regulating hypoxic condition, are altered [7]. HIFs, the dimeric proteins, are composed of a constitutive subunit named HIF-1β and an oxygen-regulated α-subunit (HIF-1, 2, 3α) [8]. The activity of HIF-1α is dynamic and related to the availability of oxygen. In the presence of oxygen, HIF-1 α is degraded by the proteasome system; so that, HIF-1α is hydroxylated by prolyl hydroxylases (PHD), in keeping, von Hippel-Lindau (VHL) recognizes the hydroxylated HIF-1α. This event subsequently ubiquitinates HIF-1α for degradation by the 26S proteasome [9, 10]. PHDs are inactive in a hypoxic condition and allow HIF-1α to link to the HIF-1β subunit.

According to previous studies, HIFs are active in almost solid tumors. HIFs regulate different signaling pathways, which are implicated in the cell viability, proliferation, epithelial-to-mesenchymal transition (EMT), angiogenesis, metastasis, and therapy resistance [11]. However, other pathways including mammalian target of rapamycin (mTOR), phosphatidylinositol 3-kinases (PI3K)-Akt, Wnt/β-catenin, nuclear factor-κB (NF-κB), mitogen-activated protein kinases (MAPK), and NADPH oxidase (NOX) facilitate the adaption of tumor cells to hypoxia [1, 12, 13]. Besides, HIFs have been shown to facilitate exosomes biogenesis and secretion [14]. Exosomes a subfamily of extracellular vesicles (EVs) mediate intercellular communication by carrying different biological molecules among cells. These vesicles contain various biological molecules like proteins, RNAs (coding and non-coding RNAs), DNAs, and lipids, regulating activation of different signaling pathways in recipient cells located nearby or distant tissues [15, 16]. It has been shown that exosomes derived from tumor cells participate in modulating the tumor microenvironment and promoting tumorigenesis [17, 18]. Confirmed that, hypoxia induces exosomes biogenesis and secretion and thereby promotes tumor intercellular communication, representing the key role of exosomes in hypoxic tumors [14, 19]. The majority of experiments discussed in this review used 1% O2 as a hypoxic model that generally called the hypoxic condition, if not, we explained the condition. In the present review, we discuss exosomes biogenesis and loading and also possible underlying mechanisms under hypoxic. Also, we describe the key roles of hypoxic in tumorigenesis and tumor-therapy.

Tumor microenvironment

The tumor microenvironment is a dynamic environment around a tumor, containing the blood vessels, fibroblasts, immune cells, the extracellular matrix (ECM), and signaling molecules that support proliferation, growth, metastasis, and therapy resistance of tumor cells. Tumor cell proliferation, death, invasion, migration, angiogenesis, metabolic reprogramming, immune evasion, are all regulated by the complex interaction inside the tumor microenvironment. In this regard, autocrine, paracrine, and juxtacrine communication network orchestrate these biological functions. Paracrine-mediated communication plays pivotal roles in signal transduction between neighboring and distant cells [20,21,22].

Non-tumor cells including fibroblasts, endothelial cells (ECs), and immune cells contribute to tumor microenvironment interaction and are affected by tumor soluble factors, and their fate goes through tumor-like modifications, persistently accommodate to the tumor microenvironment and support tumor growth. In the tumor microenvironment, fibroblasts are motivated into cancer-associated fibroblasts (CAFs), these cells are the most resident stromal cells in the tumor microenvironment, producing an ECM that vary common ECM in inflexibility and arrangement properties that facilities migration and invasion of tumor cells [23]. In the tumor microenvironment, hypoxia induces tumor cells to produce angiogenic factors, which in turn affect ECs and up-regulate angiogenesis [24, 25]. In the tumor microenvironment, the resident immune cells demonstrate multiplicity and could suppress the immune responses. Also, anti-inflammatory molecules can inhibit the immune system, which is involved in the suppression of cancer cells [26, 27]. These factors and cells make the tumor microenvironment a complex system and resistant to different therapies [28, 29].

Biogenesis of EVs

The term EVs refers to nano-micro-sized heterogeneous vesicles released from cells via intrigue mechanisms [15]. EVs generally comprise three classes of vesicles including exosomes, ectosomes, and apoptotic bodies [30]. Exosomes are 30–150 nm vesicles that originated from multivesicular bodies (MVBs) located in the cytoplasm, and thus, secreted into the extracellular milieu following the fusion of MVBs with the plasma membrane [31] (Fig. 1). In general, MVBs have three possible fates [15, 32], including; (i) the fusion of MVBs with the plasma membrane and secretion of exosomes, (ii) fusion with lysosome and degradation of exosomes, and (iii) back-fusion with the plasma membrane and recycling the biomolecules to the plasma membrane. Upon secretion into the extracellular milieu, exosomes can deliver their cargo to target cells and affect their fate, function, and morphology [33, 34] (Fig. 1). Ectosomes are also known microvesicles (MVs), ranging from 100 to 1000 nm, shed directly from the plasma membrane [30] (Fig. 1). Similar to the exosomes loading process, proteins and lipids and of the membrane- are directed into sites of MVs budding. For example, the oligomeric cytoplasmic proteins are anchored to the plasma membrane lipids and also have a high affinity for lipid rafts, therefore these proteins can enter into MVs [35, 36]. MVs exhibit common markers such as Annexin V, Flotinin-2, CD40, CD62, and integrins.

Fig. 1
figure1

Biogenesis and secretion of exosomes. Exosomes originate from multivesicular body (MVB) and release into the extracellular matrix upon fusion of MVB with the plasma membrane. One secreted, exosomes can reach to target cells through three possible ways. Microvesicles shed directly from the plasma membrane. N: nucleus

Once EVs are secreted into the extracellular milieu, target cells can uptake these nano-sized particles. The entrance of EVs into the target cells causes phenotypic and functional changes, affecting normal and pathological states [30] (Fig. 1). According to previous studies, EVs can reach target cells by vesicle internalization, receptor-ligand interaction, and direct fusion with the target cell membrane [30, 33, 37] (Fig. 1). Vesicle internalization may comprise such different mechanisms as endocytosis, pinocytosis, and phagocytosis. In the receptor-ligand interaction way, molecules of EVs surface interact with corresponding molecules on the target cells' plasma membrane [38, 39]. In the direct fusion way, EVs membrane fuse with target cell membrane similar to conventional membrane fusion process by which EVs cargo discharged into the cytoplasm of target cells. Overall, EVs uptake is complex and possibly depends on the types of EVs and target cells, and they may be related to the downstream effects and signaling pathways mediated by EVs [37]. Furthermore, it is not clear that these ways synergically or independently are engaged by cells.

Hypoxia promotes exosomes biogenesis

Hypoxia has been shown to induce EVs biogenesis and secretion. Wang and co-workers, for example, declared that exposure of breast cancer cells to hypoxia conditions results in producing more MVs via HIF/RAB22A signaling [40]. Similarly, King et al. [41] confirmed that incubation of different breast cancer cell lines; such as MCF-7, SKBR-3, and MDA-MB-231 cells with fair (1% O2) and severe (0.1% O2) hypoxia increased exosomes biogenesis and secretion. They also confirmed the key role of HIF in inducing exosomes biogenesis. However, the detailed mechanisms by which HIF mediates exosomes biogenesis are not fully clear. Besides, hypoxia can change the type of cargo and function of exosomes. Kucharzewska et al. [42], for example, showed that glioma cells cultured under hypoxia condition produce exosomes containing various mRNAs and proteins such as IL-8, caveolin 1, matrix metalloproteinases (MMP), PDGFs, and lysyl oxidase, which are involved in angiogenesis. However, hypoxia can induce exosome biogenesis in non-cancerous cells. Zhang et al. [14] demonstrated that hypoxia increased exosome secretion from renal proximal tubular cells via HIF-1 signaling. Similarly, mesenchymal stem cells (MSCs) produce abundantly exosomes upon exposure to hypoxia [43, 44]. These facts show that hypoxic stress can induce biogenesis and alter exosomal cargo. The underlying molecular mechanisms regulating the exosome loading and secretion under the hypoxic condition are not fully understood yet. However, under hypoxia, few of the pivotal pathways may involve in exosomes biogenesis, which is explained in the next sections.

HIFs signaling

In hypoxia, HIF-α protein is increased in the cytoplasm and then moves to the nucleus. In the nucleus, it links to the HIF-β subunit and another expression regulators such as the co-activators p300/CBP. Then, this complex binds to the conserved hypoxia-responsive element (HRE) for the expression of genes [45]. HIFs both directly and indirectly mediate the formation of exosomes. Previous studies showed that HIF-1α is involved in MVs and exosome biogenesis in different cell lines such as tumor and non-tumor cells [16, 20, 22]. A mediator molecule that HIF-1 regulates exosome biogenesis under hypoxia is pyruvate kinase 2 (PKM2) enzyme [46], which facilities the progression of the final step within glycolysis, the dephosphorylation of phosphoenolpyruvate to pyruvate, and it participates in ATP production within the glycolytic cycle [47]. We know that the tumor environment represents a high level of lactate as a result of glycolysis. In this regard, there is evidence that PKM2 phosphorylates synaptosome-associated protein 23 (SNAP-23), a protein associated with the synaptosome/SNARE complex, and increases secretion of exosomes [48]. Blocking of glycolysis has been confirmed to diminish the number of exosomes while increasing glycolysis with TNF-α enhanced the number of exosomes [48]. Under hypoxia conditions due to higher glycolysis, the accumulation of lactate causes the acidic condition in the extracellular environment. The acidic pH increases exosome secretion while alkaline pH decreases exosome abscission. As matter of fact, the loading of protein and RNA into exosome is affected by the pH of the environment [49, 50].

Rab-GTPases signaling

Different Rab proteins regulate the intracellular trafficking of MVBs/exosomes [15]. Rab-GTPases belong to the Ras superfamily of small GTPases, which are associated with the vesicles and the inner side of the plasma membrane, participating in intracellular trafficking of vesicles [51]. The Rab proteins have two distinct forms as an active form (GTP-bound) and an inactive form (GDP-bound. Rab- GTP-bound form is active and associated with effector proteins, and mediate formation and movement of vesicles incorporation with actin and tubulin [52]. Dorayappan et al. [53] declared that hypoxia could up-regulate STAT3 in ovarian cancer cells. STAT3 regulates the expression of Rab27a and Rab7 molecules; thus increases exosomes biogenesis. Panigrahi et al. [54] showed that Rab5 protein was accumulated around the perinuclear region of prostate cancer cells upon exposure to the hypoxic condition. RAb5 mediates the movement of the endocytosis vesicles from the plasma membrane to early endosomes and also the fusion of early endosomes with each other, proposing a key role of Rab5 in MVBs development and, subsequently promoting exosome biogenesis [54]. Hypoxia can increase the expression of the RHO-associated protein kinase (ROCK) gene, a pivotal enzyme in remodeling actin and cytoskeleton components [55]. ROCK contributes to MVs biogenesis [56], however, it was demonstrated that RhoA can drive the ROCK signaling, which subsequently leads to an induces in exosome biogenesis in various tumor cells [56].

NF-κB signaling

The exact effect of hypoxia on NF-κB expression/induction is not clear yet. However, there is evidence that PHDs regulate the expression of NF-κB under a hypoxic condition. The direct effect of NF-κB signaling on exosome biogenesis is not fully discovered so far. Hypoxia can induce the NF-κB signaling pathway, which in turn impacts the exosome cargo loading process. For example, Yang et al. [57] declared that suppression of NF-κB could alter the content of the redox modulating enzymes in exosomes derived from sera of NF-κB knockout mice. Inhibition of NF-κB by aspirin leads to a significant decrease in exosomes biogenesis and secretion [57]. Other molecules may induce exosome biogenesis. Formation of the reactive oxygen species under hypoxic conditions can induce exosome release. Hedlund et al. [58], for example, indicated that under oxidative stress (H2O2 treatment) Jurkat cells and Raji cells abundantly secrete exosomes. Besides, the authors showed that the exosomes' secretion rate of both the cell lines was increased upon the incubation of cells with thermal stress conditions.

Tetraspanin signaling

Tetraspanin proteins including CD9, CD63, CD37, CD82, and CD81, which are widely used as markers for exosomes, have been shown to facilitate exosome formation during the hypoxic condition. A hypoxia-regulator factor is located in the upstream region of the mouse CD82 gene that is up-regulated by HIF under hypoxia [59]. By overexpressing CD9 and CD82 molecules in HEK 293T cells, Chairoungdua and co-workers confirmed that exosomes production significantly increase [60]. Other key molecules including NOX2 and PI3K/mTOR axis are enriched in hypoxic cells-derived exosomes [61, 62], however, the exact role of them in exosomes biogenesis remains unclear.

Hypoxia can change exosomes cargo

Hypoxia can alter exosomes cargo. For example, by in vitro and in vivo, Jung et al. [63] showed that exosomes derived from hypoxic mouse breast cancer cells contain abundantly miR-210 that is involved in regulating vascular remodeling-related genes, including PTP1B and Ephrin A3. Similarly, Ding et al. [64] reported that inducing hypoxic stress (1% O2) on SKOV3 ovarian cancer cells led to an increase in the exosomal miR-210 level. The authors concluded that miR-210 increased SKOV3 ovarian cancer cells' mobility and progression. HIF-1α interacts with HRE, which is located on the proximal end of miR-210 and directs it into exosomes [65]. Hypoxic colorectal cancer (CRC) cells release exosomes containing a higher level of Wnt4 that increase the normoxic (21% O2) CRC cell migration behavior and invasion rate via HIF-1α signaling [66]. Furthermore, exosomal Wnt4 increases β-catenin transposition to the nucleus in normoxic CRC cells. The activation of the β-catenin signaling pathway plays a pivotal role in the motility and invasion of normoxic CRC cells. In another study, human pancreatic cancer cells such as PCA LNCaP and PC3 were cultured under hypoxic (1% O2) or normoxic (21% O2) conditions, and their exosomes were isolated from conditioned media. Immunoblotting analysis showed that the protein levels of CD63, CD81, HSP90, HSP70, and Annexin II were increased in hypoxic exosomes as compared to normoxic ones [67]. Exosomes released from hypoxic U87MG glioblastoma cells contain an elevated level of some proteins like thrombospondin-1 (TSP1), VEGF, and protein-lysine 6-oxidase (LOX) that promote growth, metastasis, and angiogenesis of tumor [68]. Using hypoxia-resistant multiple myeloma (HR-MM) cells, Umezu and colleagues team found that these cells abundantly produce exosomes with distinct cargo following incubation with the chronic hypoxic condition. They showed that these exosomes are enriched with miR-135b as compared to those of normoxic cells [69]. The impact of hypoxia on exosomes cargo derived from different cancer cells has been studied, and we summarized a list of the altered cargo of exosomes under hypoxic condition in Table 1.

Table 1 Altered cargo of exosomes under hypoxic condition

Role of hypoxic exosomes in tumor cell metastasis

Metastasis, relocation of tumor cells from the origin site to a secondary location, is an essential factor for cancer growth [70]. Tumor cells release exosomes with aggressive properties that can promote tumorigenesis via increasing metastasis upon reach to recipient cells [71]. The induction of epithelial-mesenchymal transition (EMT) in tumor cells is a critical event in the initiation of metastasis [72].

During the EMT process, the tumor cells reorganize their cytoskeleton and acquire a mesenchymal-like phenotype, which enables them for migration and invasion to the new locations [73]. In this scenario, the E-cadherin molecules are down-regulated, which is pivotal for the loss of epithelial phenotype [74]. Thus, loss of E-cadherin is associated with the reduction of cell-to-cell contact, the disruption of catenin/ E-cadherin interaction, abnormal β-catenin signaling, and finally cytoskeleton reorganization. Collectively, these events cause losing epithelial shape and acquiring a migratory phenotype in tumor cells [75].

A growing body of evidence showed that hypoxic tumor cells secrete exosomes promoting the migration ability and invasion rate of different tumor cells. For example, it was reported that exosomes collected from conditioned media of hypoxic prostate cancer cell contain several proteins that down-regulated adherents molecules in naïve LNCaP and PC3 prostate cancer cells, which, in turn increased the migration and invasiveness of cells, thus prompting metastasis in vitro [67]. The authors also showed that these exosomes down-regulated E-cadherin coincided with the up-regulation of nuclear and cytoplasmic β-catenin in prostate cancer cells, indicating an increase in the invasiveness, and stemness of prostate cancer cells. Xue et al. [76] found that hypoxia increased the loading of lncRNA-UCA1 into exosomes of bladder cancer cells. These exosomes promoted the growth and migration of bladder tumor cells both in vitro and animal models. Besides, they showed that the expression levels of lncRNA-UCA1 in blood exosomes of patients with bladder cancers were higher in comparison with the healthy ones. Similarly, Li and co-workers showed that exosomes isolated from hypoxic oral squamous cell carcinoma could induce metastasis in normoxic cells. Further scrutiny revealed that these exosomes abundantly contain miR-21, which was responsible for tumorigenesis via regulating the expression of E-cadherin, snail, and vimentin in target cells [77]. Besides, exosomes derived from hypoxic-treated hepatocellular cancer cells are enriched with linc-RoR that promote migration and metastasis of tumor cells via a miR-145/HIF-1α signaling pathway in vitro [78]. LMP1-positive exosomes derived from nasopharyngeal carcinoma cells can increase metastasis in recipient nasopharyngeal cells via transporting HIF1α and inducing EMT phenotype [79]. The authors demonstrated that HIF1α altered the expression of E- and N-cadherins which is associated with EMT and led to increased migration of cells in vitro. The results obtained from Wang et al. [80] study showed that hypoxic exosomes derived from metastatic small cell lung cancer cells (NCI-H1688) induced migration of tumor cells through TGF-β and IL-10 in vitro. Several experiments have been carried out to investigate the effect of hypoxic exosomes on tumor invasiveness and metastasis (Table 2).

Table 2 Roles of exosomes derived from hypoxic tumor cells in cancer

Role of hypoxic exosomes in modulating immune responses

Modulating immune responses is vital for the invasion and formation of a new niche for the progress of metastasis [81]. Exosomes from different tumor cells have been shown to modulate the immune system via different ways such as suppression of NK cells activity, inducing T-cell apoptosis, down-regulating IFN-γ-inducible class II expression of macrophages, and regulating the differentiation of monocytes into the myeloid-derived suppressor cells (MSDCs), which collectively leads to immunosuppressive function and the cancer development [82, 83] (Fig. 2). Exosomes from hypoxic nasopharyngeal carcinoma (NPC) cells contain miR-24-3p that inhibit T-cell proliferation, Th17, and Th1 differentiation; and promote the differentiation of regulatory T-cells (Tregs) [84]. Exosomes derived from breast cancer cells directly inhibited the T-cell survival and the NK cell function, consequently, the immune response was inhibited against tumor cells in pre-metastatic organs [85]. Exosomes from lung cancer cells transfer miRs that inhibit the genes related to the Toll-like receptor (TLR) family in macrophages. This event induces the production of proinflammatory cytokines that supports enhanced tumor dissemination [86]. Tumor-derived exosomes from plasma of head and neck squamous cell carcinoma patients contain CD73 and CD39 molecules, which participate in the production of adenosine from ATP. Adenosine is involved in suppressing the activity of activated B cells by converting the motivated B-cells into regulatory B-cells [87]. Also, Liu et al. [88] demonstrated that exosomes from mouse breast and melanoma tumor cells induced the differentiation of myeloid precursor cells towards MSDCs. This phenomenon promotes tumor exosome-mediated expansions of MDSCs and tumor metastasis. Incubation of epithelial ovarian cancer with the hypoxic condition may promote the loading of miR-940 into exosomes. These exosomes induce macrophage polarization by up-regulating the expression of the M2-type markers like CD206 and CD163. These findings demonstrated that exosomes transferred miR-940 to macrophages and induced macrophages to an M2-like phenotype, which is favorable for tumor progression [89]. Collectively, tumor-derived exosomes negatively modify immune cell function and participate in tumor growth.

Fig. 2
figure2

Effect of exosomes derived from hypoxic tumor cells on immune cells and angiogenesis

Role of hypoxic exosomes in tumor angiogenesis

Angiogenesis, the progress of new blood vessels from the pre-existing vessels, is a complex process and a critical factor that promotes the growth and metastasis of several solid tumors [90]. Hypoxia is frequently seen in the tumor microenvironment and up-regulates angiogenesis [91]. This process is highly regulated by various ligands, receptors, and several signaling pathways. Angiogenesis switch on/off is related to the balance between anti and pro-angiogenic factors. A growing body of evidence has highlighted the key role of the miRs cargo of hypoxic exosomes in tumor angiogenesis. A study by Umezu and co-workers demonstrated that miR-135b is abundantly present in hypoxia-resistant multiple myeloma (HR-MM) cells that enhance angiogenesis in human umbilical vein endothelial cells (HUVECs) through targeting HIF-1 in vitro [69]. Hypoxic lung cancer cells secrete exosomes enriched with miR-23a that facilitate the angiogenesis in HUVECs by down-regulating ZO-1 and prolyl hydroxylase proteins. These proteins are involved in tight junction [92]. Hypoxia increased miR-494 molecules in exosomes of non-small cell lung cancer (NSCLC) cells through the HIF-1α-mediated mechanism. These exosomes down-regulated PTEN and activated Akt/eNOS axis in HUVECs, and therefore promoted angiogenesis [93]. Recently, an analysis of exosomes from hypoxic human breast cancer cell line (MDA-MB-231 cells) showed that these exosomes contain many types of angiogenic mRNAs that can promote angiogenesis in HUVECs. Co-culturing of these exosomes with HUVECs could deliver exosomal VEGF-A mRNAs from tumor cells to HUVECs and were translated into protein in HUVECs, therefore induced VEGFR2-dependent angiogenesis [94]. Mao et al. [95] reported that exosomes released from hypoxic esophageal squamous cell carcinoma increased growth, migration, invasion, and tubulogenesis of HUVECs both in vitro and in vivo as compared to exosomes derived from normoxic cells. Under hypoxic conditions, pancreatic tumor cells release exosomes enriched with noncoding RNA UCA1 molecules that promote angiogenesis via miR-96-5p/AMOTL2/ERK1/2 axis both in vitro and in vivo [96]. Exosomes derived from hypoxic glioblastoma cells have been shown to transfer miR-182-5p that can directly inhibit miR-182-5p targets Kruppel-like factor 2 and 4, resulting in the up-regulation of VEGFR, thus increasing tumor angiogenesis. Furthermore, exosomal miR-182-5p can target tight junction-related proteins including occludin, ZO-1, and claudin-5 in ECs which result in promoting migration and metastasis [97]. A study by Matsuura et al. [98] demonstrated that exosomes isolated from human liver cancer cell lines (PLC/PRF/5 and HuH7) increased the angiogenic activity of HUVECs. They showed that these exosomes were enriched with miR-155 responsible for inducing angiogenesis in HUVECs. Exosomes derived from hypoxic papillary thyroid tumor cells including KTC-1 and BCPAP cells promoted the angiogenesis in HUVECs compared with those of normal thyroid follicular cell lines (Nthy-ori-3-1), normoxic BCPAP cells both in vitro and in vivo. In keeping, it was demonstrated that hypoxic exosomes contain high levels of miR-21, which targeted COL4A1 and TGFBI andinduced tubulogenesis and angiogenesis [99]. More recently, Mo et al. [100] found that exosomes derived from hypoxic A549 lung cancer cells contain angiopoietin-like 4 protein that induces angiogenesis in HUVECs. Also, exosomal miR-210 released from hypoxic leukemia cells induced tubulogenesis in ECs [101]. These data show exosomes from hypoxic tumor cells can promote angiogenesis, thus these exosomes may serve as a novel target for cancer treatment.

Diagnostic application of hypoxic exosomes

Early diagnosis of cancer is the hallmark of cancer therapy that improves the survival rate and quality of a patient’s life [102]. As exosomes released from tumor cells can be distributed to several bio-fluids, thus, a simple liquid-biopsy from plasma, serum, urine, and CSF is a non-invasive way for acquiring detailed information about tumor environment/status [15]. As exosomes originate directly from tumor cells, they may serve as a diagnostic tool for predicting the extent of the physiological and pathological status of tumor cells. Exosomes cargo like proteins and nucleic acids are altered upon the change in the dynamic of parental cells, suggesting a prognostic and diagnostic tool for the treatment of cancer [103]. Analyzing exosomal cargoes (miRs and proteins) gives a chance for scientists to predict the status of a pathological condition like tumor progression. Therefore, as under hypoxia condition tumor cells release more exosomes with distinct cargoes; they may be potentially used as a biomarker for hypoxia tumors. Exosomal biomarker represents superiority against other approaches evaluating hypoxia. Currently, some of the approaches have clinical challenges in estimating hypoxia. For instance, pimonidazole and immunohistochemistry techniques are invasive and necessitate surgical elimination of tumors. Consequently, the application of tumor-derived exosomes from bio-fluids to obtain evidence of hypoxia standing in various cancers could be noteworthy. In this regard, exosomal miRs and protein obtained from bio-fluids have biomarker potential for the diagnosis of different cancers [104, 105]. For example, Matsumura et al. [106] reported that expression of miR-19a in exosomes isolated from the serum of CRC patients was up-regulated, which could be considered as a relapse biomarker of CRC. In the case of hypoxic tumors, confirmed that HIF-1 mRNA molecules are enriched within tumor-derived exosomes that are commonly considered as a typical biomarker for diagnosing cancer development as well as therapy consequences [79]. A study conducted by Kucharzewska et al. [107] demonstrated that exosomes obtained from both Glioblastoma multiform (GBM) cells culture medium and isolated from the GBM patients plasma abundantly contain hypoxia-regulated proteins and mRNAs including PDGFs, Caveolin 1, IL- 8, MMPs, and LOX. The authors conclude that the mRNA and proteome content of these exosomes reflect the hypoxic status of cancer and have biomarker potential for GBM. Also, miRs and metabolites cargo of hypoxic exosome would be useful as a biomarker for diagnosis and prognosis of different cancers such as prostate, colorectal, and pancreatic cancers [108,109,110]. For example, the expression pattern of exosomal miR-210 from the serum of CRC patients may function as a promising non-invasive biomarker for the diagnosis and prognosis of CRC [108]. During the hypoxic condition, miR-210 is the most extensively and consistently up-regulated miR that commonly shows tumorigenesis properties in different tumors [111]. Similar to hypoxic exosomes from prostate tumor cells (PCa and LNCaP), exosomes obtained from the serum of PCa patients contain a high level of miR-885 and miR-521 [109]. Besides, proteins cargo (VLA-4, TYRP2, HSP90, and HSP70) of exosomes derived from the plasma of melanoma patients are significantly increased in comparison with healthy persons [112]. VLA-4 and TYRP2 are up-regulated under the hypoxic condition and their high expression in exosomes correlates with stage 3 melanoma [113, 114]. Previous studies have shown that HSP90 and HSP70 are hypoxic related proteins and play roles in hypoxic condition [115, 116]. In this regard, exosomal proteins have diagnostic and prognostic value for the melanoma tumor development and hypoxic status. Therefore, hypoxic exosomes may be a useful tool for predicting the hypoxic status of solid tumors, however, it seems that this evidence is not sufficient and further scrutiny is essential to examine and confirm the potential application of hypoxic exosomes to quantify the degree of hypoxia to detect stages of tumor development.

Possible therapeutic application of exosomes

Exosomes can reach target cells and alter the function, fate, and morphology through different signaling pathways. As mentioned, tumor cells under hypoxic conditions produce more exosomes, promoting tumorigenesis. Thus, it seems that targeting exosomes formation and secretion particularly from the hypoxic tumor may provide us with a tool that reduces tumorigenesis. Recent findings have shown that it is possible to inhibit the exosomes biogenesis and secretion from different cells. For example, Manumycin A and GW4869 have been shown to inhibit exosome biogenesis and release from cells [117]. Datta et al. [118] reported that Manumycin A inhibited exosomes biogenesis and secretion from aggressive prostate cells mainly by suppression of Ras/Raf/ERK1/2 signaling and hnRNP H1. They concluded that Manumycin A is a potential drug candidate to inhibit exosome biogenesis and secretion. Suppression of Rab27a, a protein involved in exosomes secretion, has been shown to inhibit exosome-dependent and -independent tumor cells growth [119]. Inhibition of Rab proteins involved in intracellular trafficking of exosomes/MVB may inhibit exosomes biogenesis and release, thus they may be a target to inhibit exosome biogenesis. For example, Rab5a has been involved in the early step of exosomes biogenesis, while Rab11, Rab27a, and Rab35 regulate the MVBs-plasma membrane fusion and exosomes secretion. Moreover, inhibition of sphingomyelinase, an enzyme catalyzes the formation of ceramide from sphingomyelin, may lessen exosomes biogenesis and loading, thus prevents tumor growth [120]. In human prostate cancer (PC3) cells, it was shown that Imipramine profoundly inhibited the biogenesis of both microvesicles and exosomes [121]. A fascinating approach has been proposed by Marleau and colleagues based on the effective elimination of blood exosomes of breast cancer patients by extracorporeal hemofiltration associated with affinity agents like exosome-trapping antibodies and lectins. This approach was proposed to trap particles < 200 nm from the whole circulatory system [122]. Considering the existence of numerous experiments on exosomes inhibition, there are challenges regarding analyzing and conclusions of findings, because as various methods are used to isolate and characterize exosomes. Moreover, some researchers did not include ISEV guidelines regarding the exosomes confirmation and validation, as exosome-based studies had been performed before the 2014 and 2018 declaration of ISEV guidelines about exosome-based studies [30, 123]. Besides, it is vital to discover the non-toxic doses of the drugs for target cells to confirm that any decrease in exosomes secretion resulting from exosomes inhibition not from cell death. The majority of these experiments were pre-clinical performed, thus, clinical trials are essential for the approval. Furthermore, the non-targeting effects of these drugs on exosomes biogenesis from normal cells remain an important concern. At least, in the field of cancer, key studies must still be necessary to investigate their effects on exosomes production from both healthy and tumor cells and to progress methods to specifically deliver drugs into tumor cells.

Another approach that exosomes can be used as a therapeutic agent is the drug delivery potential of them. According to previous studies, exosomes can be used as a drug delivery system in two ways: (I); direct loading by which therapeutic agents directly sorted into exosomes; and (II); indirect loading where source cells co-cultured with therapeutic agents or manipulated genetically to produce optional exosomes. In this regard, different approaches for producing optional exosomes have been examined, which comprise: incubating exosomes with the agents, electroporation, sonication, sensitive fusogenic peptide, and cationic lipid, liposome, and exosome-coated metal–organic nanoparticle [124, 125]. An example of the direct method, Zhuang et al. [126] encapsulated curcumin into tumor cell-derived exosomes. Then, these exosomes successfully delivered these exosomes to microglia cells through an intranasal way in a brain inflammatory model of mice. Also, the authors successfully inserted a Stat3 inhibitor into the same exosomes. They demonstrate that this method could provide a noninvasive and new therapeutic approach for the treatment of brain diseases. Besides drugs, siRNAs can also be loaded into the hydrophilic core of exosomes in the pharmaceutically active form [127, 128]. In this regard, Alvarez-Erviti et al. [129], for example, successfully loaded siRNAs into exosomes purified from dendritic cells and delivered those exosomes to the mouse brain.

An example of an indirect loading method, Pascucci et al. [130] co-cultured MSCs with paclitaxel (PTX) and then isolated exosomes from the supernatant. In keeping, they found that PTX was sorted into exosomes and these exosomes exhibited strong anti-tumor activity in vitro. Interestingly, exosomes from hypoxic MDA-MB-231 human breast cancer cells loaded with anti-cancer drug Olaparib exhibited better uptake rate when co-cultured with hypoxic cancer cells [131]. Collectively, exosomes may serve as a new avenue to overcome cancer, however, translation of pre-clinical results into the clinic needs more experiments regarding exosomes biology and bio-applications in disease models.

Conclusion

Hypoxia increases exosome biogenesis and secretion in tumor cells. Moreover, it can alter exosomes cargo. Exosomes released from tumor cells play a pivotal role in promoting growth, metastasis, and resistance of hypoxic tumors. Furthermore, exosomes from hypoxic tumors have been suggested to be a promising non-invasive biomarker for cancer diagnosis through analyzing their components such as proteins and miRs. Inhibition of exosomes biogenesis and secretion may help to reduce tumorigenesis. Exosomes can be used as a drug delivery system for the treatment of cancer. However, despite many experiments, translation of the preclinical findings into the clinic requires additional examinations in this field. Therefore, further scrutiny is essential for a better understanding of the mechanisms behind exosome loading and production under hypoxic conditions, which could be useful in targeting exosomes biogenesis and prevent tumorigenesis.

Availability of data and materials

The primary data for this study is available from the authors on direct request.

Abbreviations

ABs:

Apoptotic bodies

AMPK:

AMP-activated protein kinase

CAFs:

Cancer-associated fibroblasts

CMA:

Chaperone-mediated autophagy

CML:

Chronic myeloid leukemia

d-GalN/LPS:

D-galactosamine and Lipopolysaccharide

GBM:

Glioblastoma multiform

ECM:

Extracellular matrix

ECs:

Endothelial cells

EMT:

Epithelial-to-mesenchymal transition

ESCRT:

Endosomal sorting complex required for transport

EVs:

Extracellular vesicles

HIFs:

Hypoxia-inducible factors

HRE:

Hypoxia-responsive element

HR-MM:

Hypoxia-resistant multiple myeloma

HUVECs:

Human umbilical vein endothelial cells

ILVs:

Intraluminal vesicles

ISEV:

International Society for Extracellular Vesicles Protein type 2A

LOX:

Protein-lysine 6-oxidase

MAPK:

Mitogen-activated protein kinases

MHC:

Major histocompatibility complex

MMPs:

Matrix metalloproteinase

MSCs:

Mesenchymal stem cells

MSDCs:

Myeloid-derived suppressor cells

mTOR:

Mammalian target of rapamycin

MV:

Microvesicles

MVBs:

Multivesicular bodies

nSMase2:

Sphingomyelinase 2

NSCLC:

Non-small cell lung cancer

NOX:

NADPH oxidase

NPC:

Nasopharyngeal carcinoma

PI3K:

Phosphatidylinositol 3-kinases

PHD:

Prolylhydroxylase

PKM2:

Pyruvate kinase 2

PLP:

Proteolipid proteins

PM:

Plasma membrane

PTX:

Paclitaxel

ROCK:

RHO-associated protein kinase

ROS:

Reactive oxygen species

SNAREs:

Soluble NSF attachment protein receptors

TLR:

Toll-like receptors

VHL:

Von Hippel-Lindau

References

  1. 1.

    Deep G, Panigrahi GK. Hypoxia-induced signaling promotes prostate cancer progression: exosomes role as messenger of hypoxic response in tumor microenvironment. Critical Reviews™ in Oncogenesis 2015, 20.

  2. 2.

    Al Tameemi W, Dale TP, Al-Jumaily RMK, Forsyth NR. Hypoxia-modified cancer cell metabolism. Front Cell Dev Biol. 2019;7:4.

    PubMed  PubMed Central  Article  Google Scholar 

  3. 3.

    McKeown S. Defining normoxia, physoxia and hypoxia in tumours—implications for treatment response. Br J Radiol. 2014;87:20130676.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  4. 4.

    Tomes L, Emberley E, Niu Y, Troup S, Pastorek J, Strange K, Harris A, Watson PH. Necrosis and hypoxia in invasive breast carcinoma. Breast Cancer Res Treat. 2003;81:61–9.

    PubMed  Article  PubMed Central  Google Scholar 

  5. 5.

    Balkwill FR, Capasso M, Hagemann T: The tumor microenvironment at a glance. The Company of Biologists Ltd; 2012.

  6. 6.

    Folkman J: Role of angiogenesis in tumor growth and metastasis. In Seminars in oncology. Elsevier; 2002: 15–18.

  7. 7.

    Semenza GL. Hypoxia-inducible factors in physiology and medicine. Cell. 2012;148:399–408.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  8. 8.

    Harada H, Inoue M, Itasaka S, Hirota K, Morinibu A, Shinomiya K, Zeng L, Ou G, Zhu Y, Yoshimura M. Cancer cells that survive radiation therapy acquire HIF-1 activity and translocate towards tumour blood vessels. Nature communications. 2012;3:1–12.

    Article  CAS  Google Scholar 

  9. 9.

    Ivan M, Kondo K, Yang H, Kim W, Valiando J, Ohh M, Salic A, Asara JM, Lane WS, Kaelin WG Jr. HIFα targeted for VHL-mediated destruction by proline hydroxylation: implications for O2 sensing. Science. 2001;292:464–8.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  10. 10.

    Tukmechi A, Rezaee J, Nejati V, Sheikhzadeh N. Effect of acute and chronic toxicity of paraquat on immune system and growth performance in rainbow trout, O ncorhynchus mykiss. Aquacult Res. 2014;45:1737–43.

    CAS  Google Scholar 

  11. 11.

    Semenza GL. Targeting HIF-1 for cancer therapy. Nat Rev Cancer. 2003;3:721–32.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  12. 12.

    Mitani T, Harada N, Nakano Y, Inui H, Yamaji R. Coordinated action of hypoxia-inducible factor-1α and β-catenin in androgen receptor signaling. J Biol Chem. 2012;287:33594–606.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  13. 13.

    Harris AL. Hypoxia—a key regulatory factor in tumour growth. Nat Rev Cancer. 2002;2:38–47.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  14. 14.

    Zhang W, Zhou X, Yao Q, Liu Y, Zhang H, Dong Z. HIF-1-mediated production of exosomes during hypoxia is protective in renal tubular cells. American Journal of Physiology-Renal Physiology. 2017;313:F906–13.

    PubMed  PubMed Central  Article  Google Scholar 

  15. 15.

    Kowal J, Tkach M, Théry C. Biogenesis and secretion of exosomes. Curr Opin Cell Biol. 2014;29:116–25.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  16. 16.

    Jabbari N, Akbariazar E, Feqhhi M, Rahbarghazi R, Rezaie J. Breast cancer-derived exosomes: tumor progression and therapeutic agents. J Cell Physiol. 2020. https://doi.org/10.1002/jcp.29668.

    Article  PubMed  PubMed Central  Google Scholar 

  17. 17.

    Lu X, Kang Y. Hypoxia and hypoxia-inducible factors: master regulators of metastasis. Clin Cancer Res. 2010;16:5928–35.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  18. 18.

    Filipazzi P, Bürdek M, Villa A, Rivoltini L, Huber V. Recent advances on the role of tumor exosomes in immunosuppression and disease progression. In: Seminars in cancer biology. Elsevier; 2012, p. 342–349.

  19. 19.

    Park JE, Tan HS, Datta A, Lai RC, Zhang H, Meng W, Lim SK, Sze SK. Hypoxic tumor cell modulates its microenvironment to enhance angiogenic and metastatic potential by secretion of proteins and exosomes. Mol Cell Proteomics. 2010;9:1085–99.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  20. 20.

    Giraldo NA, Sanchez-Salas R, Peske JD, Vano Y, Becht E, Petitprez F, Validire P, Ingels A, Cathelineau X, Fridman WH. The clinical role of the TME in solid cancer. Br J Cancer. 2019;120:45–53.

    PubMed  Article  PubMed Central  Google Scholar 

  21. 21.

    Yuan Y, Jiang Y-C, Sun C-K, Chen Q-M. Role of the tumor microenvironment in tumor progression and the clinical applications. Oncol Rep. 2016;35:2499–515.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  22. 22.

    Khaksar M, Sayyari M, Rezaie J, Pouyafar A, Montazersaheb S, Rahbarghazi R. High glucose condition limited the angiogenic/cardiogenic capacity of murine cardiac progenitor cells in in vitro and in vivo milieu. Cell Biochem Funct. 2018;36:346–56.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  23. 23.

    Petrova V, Annicchiarico-Petruzzelli M, Melino G, Amelio I. The hypoxic tumour microenvironment. Oncogenesis. 2018;7:1–13.

    CAS  Article  Google Scholar 

  24. 24.

    Lucero R, Zappulli V, Sammarco A, Murillo OD, Cheah PS, Srinivasan S, Tai E, Ting DT, Wei Z, Roth ME. Glioma-derived miRNA-containing extracellular vesicles induce angiogenesis by reprogramming brain endothelial cells. Cell Rep. 2020;30(2065–2074):e2064.

    Google Scholar 

  25. 25.

    Varricchi G, Loffredo S, Galdiero MR, Marone G, Cristinziano L, Granata F, Marone G. Innate effector cells in angiogenesis and lymphangiogenesis. Curr Opin Immunol. 2018;53:152–60.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  26. 26.

    Xie F, Zhou X, Fang M, Li H, Su P, Tu Y, Zhang L, Zhou F. Extracellular vesicles in cancer immune microenvironment and cancer immunotherapy. Adv Sci. 2019;6:1901779.

    CAS  Article  Google Scholar 

  27. 27.

    Whiteside TL. Exosome and mesenchymal stem cell cross-talk in the tumor microenvironment. In: Seminars in immunology. Elsevier; 2018, p. 69–79.

  28. 28.

    Jarosz-Biej M, Smolarczyk R, Cichoń T, Kułach N. Tumor microenvironment as A “Game Changer” in cancer radiotherapy. Int J Mol Sci. 2019;20:3212.

    CAS  PubMed Central  Article  Google Scholar 

  29. 29.

    Peng J, Yang Q, Shi K, Xiao Y, Wei X, Qian Z. Intratumoral fate of functional nanoparticles in response to microenvironment factor: Implications on cancer diagnosis and therapy. Adv Drug Deliv Rev. 2019;143:37–67.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  30. 30.

    Théry C, Witwer KW, Aikawa E, Alcaraz MJ, Anderson JD, Andriantsitohaina R, Antoniou A, Arab T, Archer F, Atkin-Smith GK. Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines. Journal of extracellular vesicles. 2018;7:1535750.

    PubMed  PubMed Central  Article  Google Scholar 

  31. 31.

    Record M, Silvente-Poirot S, Poirot M, Wakelam MJ. Extracellular vesicles: lipids as key components of their biogenesis and functions. J Lipid Res. 2018;59:1316–24.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  32. 32.

    Théry C, Zitvogel L, Amigorena S. Exosomes: composition, biogenesis and function. Nat Rev Immunol. 2002;2:569–79.

    PubMed  Article  CAS  PubMed Central  Google Scholar 

  33. 33.

    McKelvey KJ, Powell KL, Ashton AW, Morris JM, McCracken SA. Exosomes: mechanisms of uptake. J Circulating Biomarkers. 2015;4:7.

    Article  CAS  Google Scholar 

  34. 34.

    Hassanpour M, Rezaie J, Nouri M, Panahi Y. The role of extracellular vesicles in COVID-19 virus infection. Infect Genet Evol. 2020. https://doi.org/10.1016/j.meegid.2020.104422.

    Article  PubMed  PubMed Central  Google Scholar 

  35. 35.

    Shen B, Fang Y, Wu N, Gould SJ. Biogenesis of the posterior pole is mediated by the exosome/microvesicle protein-sorting pathway. J Biol Chem. 2011;286:44162–76.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  36. 36.

    Yang J-M, Gould SJ. The cis-acting signals that target proteins to exosomes and microvesicles. London: Portland Press Ltd.; 2013.

    Google Scholar 

  37. 37.

    Mulcahy LA, Pink RC, Carter DRF. Routes and mechanisms of extracellular vesicle uptake. J Extracellular Vesicles. 2014;3:24641.

    Article  CAS  Google Scholar 

  38. 38.

    Morelli AE, Larregina AT, Shufesky WJ, Sullivan ML, Stolz DB, Papworth GD, Zahorchak AF, Logar AJ, Wang Z, Watkins SC. Endocytosis, intracellular sorting, and processing of exosomes by dendritic cells. Blood. 2004;104:3257–66.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  39. 39.

    Hassanpour M, Rahbarghazi R, Nouri M, Aghamohammadzadeh N, Safaei N, Ahmadi M. Role of autophagy in atherosclerosis: foe or friend? J Inflamm. 2019;16:8.

    Article  Google Scholar 

  40. 40.

    Wang T, Gilkes DM, Takano N, Xiang L, Luo W, Bishop CJ, Chaturvedi P, Green JJ, Semenza GL. Hypoxia-inducible factors and RAB22A mediate formation of microvesicles that stimulate breast cancer invasion and metastasis. Proc Natl Acad Sci USA. 2014;111:E3234-3242.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  41. 41.

    King HW, Michael MZ, Gleadle JM. Hypoxic enhancement of exosome release by breast cancer cells. BMC Cancer. 2012;12:421.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  42. 42.

    Kucharzewska P, Christianson HC, Welch JE, Svensson KJ, Fredlund E, Ringnér M, Mörgelin M, Bourseau-Guilmain E, Bengzon J, Belting M. Exosomes reflect the hypoxic status of glioma cells and mediate hypoxia-dependent activation of vascular cells during tumor development. Proc Natl Acad Sci USA. 2013;110:7312–7.

    CAS  PubMed  Article  Google Scholar 

  43. 43.

    Liu W, Li L, Rong Y, Qian D, Chen J, Zhou Z, Luo Y, Jiang D, Cheng L, Zhao S. Hypoxic mesenchymal stem cell-derived exosomes promote bone fracture healing by the transfer of miR-126. Acta Biomater. 2020;103:196–212.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  44. 44.

    Liu W, Rong Y, Wang J, Zhou Z, Ge X, Ji C, Jiang D, Gong F, Li L, Chen J. Exosome-shuttled miR-216a-5p from hypoxic preconditioned mesenchymal stem cells repair traumatic spinal cord injury by shifting microglial M1/M2 polarization. J Neuroinflammation. 2020;17:1–22.

    Article  CAS  Google Scholar 

  45. 45.

    Semenza GL. Defining the role of hypoxia-inducible factor 1 in cancer biology and therapeutics. Oncogene. 2010;29:625–34.

    CAS  PubMed  Article  Google Scholar 

  46. 46.

    Luo W, Hu H, Chang R, Zhong J, Knabel M, O’Meally R, Cole RN, Pandey A, Semenza GL. Pyruvate kinase M2 is a PHD3-stimulated coactivator for hypoxia-inducible factor 1. Cell. 2011;145:732–44.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  47. 47.

    Vaupel P, Harrison L. Tumor hypoxia: causative factors, compensatory mechanisms, and cellular response. Oncologist. 2004;9:4–9.

    PubMed  Article  Google Scholar 

  48. 48.

    Wei Y, Wang D, Jin F, Bian Z, Li L, Liang H, Li M, Shi L, Pan C, Zhu D. Pyruvate kinase type M2 promotes tumour cell exosome release via phosphorylating synaptosome-associated protein 23. Nat Commun. 2017;8:1–12.

    Article  CAS  Google Scholar 

  49. 49.

    Parolini I, Federici C, Raggi C, Lugini L, Palleschi S, De Milito A, Coscia C, Iessi E, Logozzi M, Molinari A. Microenvironmental pH is a key factor for exosome traffic in tumor cells. J Biol Chem. 2009;284:34211–22.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  50. 50.

    Ban J-J, Lee M, Im W, Kim M. Low pH increases the yield of exosome isolation. Biochem Biophys Res Commun. 2015;461:76–9.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  51. 51.

    Jordens I, Marsman M, Kuijl C, Neefjes J. Rab proteins, connecting transport and vesicle fusion. Traffic. 2005;6:1070–7.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  52. 52.

    Stenmark H, Olkkonen VM. The rab gtpase family. Genome Biol. 2001;2(reviews3007):3001.

    Google Scholar 

  53. 53.

    Dorayappan KDP, Wanner R, Wallbillich JJ, Saini U, Zingarelli R, Suarez AA, Cohn DE, Selvendiran K. Hypoxia-induced exosomes contribute to a more aggressive and chemoresistant ovarian cancer phenotype: a novel mechanism linking STAT3/Rab proteins. Oncogene. 2018;37:3806–21.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  54. 54.

    Panigrahi GK, Praharaj PP, Peak TC, Long J, Singh R, Rhim JS, Abd Elmageed ZY, Deep G. Hypoxia-induced exosome secretion promotes survival of African-American and Caucasian prostate cancer cells. Sci Rep. 2018;8:3853.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  55. 55.

    Wang Z, Jin N, Ganguli S, Swartz DR, Li L, Rhoades RA. Rho-Kinase activation is involved in hypoxia-induced pulmonary vasoconstriction. Am J Respir Cell Mol Biol. 2001;25:628–35.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  56. 56.

    Li B, Antonyak MA, Zhang J, Cerione RA. RhoA triggers a specific signaling pathway that generates transforming microvesicles in cancer cells. Oncogene. 2012;31:4740–9.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  57. 57.

    Yang JCS, Lin MW, Rau CS, Jeng SF, Lu TH, Wu YC, Chen YC, Tzeng SL, Wu CJ, Hsieh CH. Altered exosomal protein expression in the serum of NF-κB knockout mice following skeletal muscle ischemia-reperfusion injury. J Biomed Sci. 2015;22:40.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  58. 58.

    Hedlund M, Nagaeva O, Kargl D, Baranov V, Mincheva-Nilsson L. Thermal- and oxidative stress causes enhanced release of NKG2D ligand-bearing immunosuppressive exosomes in leukemia/lymphoma T and B cells. PLoS ONE. 2011;6:e16899.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  59. 59.

    Kim B, Boo K, Lee JS, Kim KI, Kim WH, Cho H-J, Park Y-B, Kim H-S, Baek SH. Identification of the KAI1 metastasis suppressor gene as a hypoxia target gene. Biochem Biophys Res Commun. 2010;393:179–84.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  60. 60.

    Chairoungdua A, Smith DL, Pochard P, Hull M, Caplan MJ. Exosome release of β-catenin: a novel mechanism that antagonizes Wnt signaling. J Cell Biol. 2010;190:1079–91.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  61. 61.

    Hervera A, De Virgiliis F, Palmisano I, Zhou L, Tantardini E, Kong G, Hutson T, Danzi MC, Perry RBT, Santos CX. Reactive oxygen species regulate axonal regeneration through the release of exosomal NADPH oxidase 2 complexes into injured axons. Nat Cell Biol. 2018;20:307–19.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  62. 62.

    Zhang W, Zhou Q, Wei Y, Da M, Zhang C, Zhong J, Liu J, Shen J. The exosome-mediated PI3k/Akt/mTOR signaling pathway in cervical cancer. Int J Clin Exp Pathol. 2019;12:2474.

    CAS  PubMed  PubMed Central  Google Scholar 

  63. 63.

    Jung KO, Youn H, Lee C-H, Kang KW, Chung J-K. Visualization of exosome-mediated miR-210 transfer from hypoxic tumor cells. Oncotarget. 2017;8:9899.

    PubMed  Article  PubMed Central  Google Scholar 

  64. 64.

    Ding L, Zhao L, Chen W, Liu T, Li Z, Li X. miR-210, a modulator of hypoxia-induced epithelial-mesenchymal transition in ovarian cancer cell. Int J Clin Exp Med. 2015;8:2299–307.

    PubMed  PubMed Central  Google Scholar 

  65. 65.

    Huang X, Ding L, Bennewith KL, Tong RT, Welford SM, Ang KK, Story M, Le Q-T, Giaccia AJ. Hypoxia-inducible mir-210 regulates normoxic gene expression involved in tumor initiation. Mol Cell. 2009;35:856–67.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  66. 66.

    Huang Z, Yang M, Li Y, Yang F, Feng Y. Exosomes derived from hypoxic colorectal cancer cells transfer Wnt4 to normoxic cells to elicit a prometastatic phenotype. Int J Biol Sci. 2018;14:2094.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  67. 67.

    Ramteke A, Ting H, Agarwal C, Mateen S, Somasagara R, Hussain A, Graner M, Frederick B, Agarwal R, Deep G. Exosomes secreted under hypoxia enhance invasiveness and stemness of prostate cancer cells by targeting adherens junction molecules. Mol Carcinog. 2015;54:554–65.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  68. 68.

    Kore RA, Edmondson JL, Jenkins SV, Jamshidi-Parsian A, Dings RPM, Reyna NS, Griffin RJ. Hypoxia-derived exosomes induce putative altered pathways in biosynthesis and ion regulatory channels in glioblastoma cells. Biochem Biophys Rep. 2018;14:104–13.

    PubMed  PubMed Central  Google Scholar 

  69. 69.

    Umezu T, Tadokoro H, Azuma K, Yoshizawa S, Ohyashiki K, Ohyashiki JH. Exosomal miR-135b shed from hypoxic multiple myeloma cells enhances angiogenesis by targeting factor-inhibiting HIF-1. Blood. 2014;124:3748–57.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  70. 70.

    Chiang AC, Massagué J. Molecular basis of metastasis. N Engl J Med. 2008;359:2814–23.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  71. 71.

    Chowdhury R, Webber JP, Gurney M, Mason MD, Tabi Z, Clayton A. Cancer exosomes trigger mesenchymal stem cell differentiation into pro-angiogenic and pro-invasive myofibroblasts. Oncotarget. 2015;6:715.

    PubMed  Article  PubMed Central  Google Scholar 

  72. 72.

    Huber MA, Kraut N, Beug H. Molecular requirements for epithelial–mesenchymal transition during tumor progression. Curr Opin Cell Biol. 2005;17:548–58.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  73. 73.

    Tan EJ, Olsson A-K, Moustakas A. Reprogramming during epithelial to mesenchymal transition under the control of TGFβ. Cell Adhesion Migration. 2015;9:233–46.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  74. 74.

    Peng Z, Wang C-X, Fang E-H, Wang G-B, Tong Q. Role of epithelial-mesenchymal transition in gastric cancer initiation and progression. World J Gastroenterol. 2014;20:5403–10.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  75. 75.

    Onder TT, Gupta PB, Mani SA, Yang J, Lander ES, Weinberg RA. Loss of E-cadherin promotes metastasis via multiple downstream transcriptional pathways. Can Res. 2008;68:3645.

    CAS  Article  Google Scholar 

  76. 76.

    Xue M, Chen W, Xiang A, Wang R, Chen H, Pan J, Pang H, An H, Wang X, Hou H, Li X. Hypoxic exosomes facilitate bladder tumor growth and development through transferring long non-coding RNA-UCA1. Mol Cancer. 2017;16:143.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  77. 77.

    Li L, Li C, Wang S, Wang Z, Jiang J, Wang W, Li X, Chen J, Liu K, Li C, Zhu G. Exosomes derived from hypoxic oral squamous cell carcinoma cells deliver miR-21 to normoxic cells to elicit a prometastatic phenotype. Can Res. 2016;76:1770.

    CAS  Article  Google Scholar 

  78. 78.

    Takahashi K, Yan IK, Haga H, Patel T. Modulation of hypoxia-signaling pathways by extracellular linc-RoR. J Cell Sci. 2014;127:1585.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  79. 79.

    Aga M, Bentz GL, Raffa S, Torrisi MR, Kondo S, Wakisaka N, Yoshizaki T, Pagano JS, Shackelford J. Exosomal HIF1α supports invasive potential of nasopharyngeal carcinoma-associated LMP1-positive exosomes. Oncogene. 2014;33:4613–22.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  80. 80.

    Wang Y, Yi J, Chen X, Zhang Y, Xu M, Yang Z. The regulation of cancer cell migration by lung cancer cell-derived exosomes through TGF-β and IL-10. Oncol Lett. 2016;11:1527–30.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  81. 81.

    Sceneay J, Parker BS, Smyth MJ, Möller A. Hypoxia-driven immunosuppression contributes to the pre-metastatic niche. Oncoimmunology. 2013;2:e22355–e22355.

    PubMed  PubMed Central  Article  Google Scholar 

  82. 82.

    Filipazzi P, Bürdek M, Villa A, Rivoltini L, Huber V. Recent advances on the role of tumor exosomes in immunosuppression and disease progression. Semin Cancer Biol. 2012;22:342–9.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  83. 83.

    Liu C, Yu S, Zinn K, Wang J, Zhang L, Jia Y, Kappes JC, Barnes S, Kimberly RP, Grizzle WE, Zhang H-G. Murine mammary carcinoma exosomes promote tumor growth by suppression of NK cell function. J Immunol. 2006;176:1375–85.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  84. 84.

    Ye SB, Zhang H, Cai TT, Liu YN, Ni JJ, He J, Peng JY, Chen QY, Mo HY, Jun-Cui, et al: Exosomal miR-24-3p impedes T-cell function by targeting FGF11 and serves as a potential prognostic biomarker for nasopharyngeal carcinoma. J Pathol 2016, 240:329–340.

  85. 85.

    Wen SW, Sceneay J, Lima LG, Wong CSF, Becker M, Krumeich S, Lobb RJ, Castillo V, Wong KN, Ellis S, et al. The biodistribution and immune suppressive effects of breast cancer-derived exosomes. Can Res. 2016;76:6816.

    CAS  Article  Google Scholar 

  86. 86.

    Fabbri M, Paone A, Calore F, Galli R, Gaudio E, Santhanam R, Lovat F, Fadda P, Mao C, Nuovo GJ. MicroRNAs bind to Toll-like receptors to induce prometastatic inflammatory response. Proc Natl Acad Sci. 2012;109:E2110–6.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  87. 87.

    Theodoraki M-N, Hoffmann TK, Jackson EK, Whiteside TL. Exosomes in HNSCC plasma as surrogate markers of tumour progression and immune competence. Clin Exp Immunol. 2018;194:67–78.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  88. 88.

    Liu Y, Xiang X, Zhuang X, Zhang S, Liu C, Cheng Z, Michalek S, Grizzle W, Zhang H-G. Contribution of MyD88 to the tumor exosome-mediated induction of myeloid derived suppressor cells. The American journal of pathology. 2010;176:2490–9.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  89. 89.

    Chen X, Ying X, Wang X, Wu X, Zhu Q, Wang X. Exosomes derived from hypoxic epithelial ovarian cancer deliver microRNA-940 to induce macrophage M2 polarization. Oncol Rep. 2017;38:522–8.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  90. 90.

    Hasina R, Lingen MW. Angiogenesis in oral cancer. J Dent Educ. 2001;65:1282–90.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  91. 91.

    Muz B, de la Puente P, Azab F, Azab AK. The role of hypoxia in cancer progression, angiogenesis, metastasis, and resistance to therapy. Hypoxia. 2015;3:83.

    PubMed  PubMed Central  Article  Google Scholar 

  92. 92.

    Hsu YL, Hung JY, Chang WA, Lin YS, Pan YC, Tsai PH, Wu CY, Kuo PL. Hypoxic lung cancer-secreted exosomal miR-23a increased angiogenesis and vascular permeability by targeting prolyl hydroxylase and tight junction protein ZO-1. Oncogene. 2017;36:4929–42.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  93. 93.

    Mao G, Liu Y, Fang X, Liu Y, Fang L, Lin L, Liu X, Wang N. Tumor-derived microRNA-494 promotes angiogenesis in non-small cell lung cancer. Angiogenesis. 2015;18:373–82.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  94. 94.

    Zhang P, Lim SB, Jiang K, Chew TW, Low BC, Lim CT. Cancer exosomes harbor diverse hypoxia-targeted mRNAs and contribute toward tumor angiogenesis. bioRxiv 2020.

  95. 95.

    Mao Y, Wang Y, Dong L, Zhang Y, Zhang Y, Wang C, Zhang Q, Yang S, Cao L, Zhang X. Hypoxic exosomes facilitate angiogenesis and metastasis in esophageal squamous cell carcinoma through altering the phenotype and transcriptome of endothelial cells. J Exp Clin Cancer Res. 2019;38:389.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  96. 96.

    Guo Z, Wang X, Yang Y, Chen W, Zhang K, Teng B, Huang C, Zhao Q, Qiu Z. Hypoxic tumor-derived exosomal long noncoding RNA UCA1 promotes angiogenesis via miR-96-5p/AMOTL2 in pancreatic cancer. Mol Ther Nucleic Acids. 2020;22:179–95.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  97. 97.

    Li J, Yuan H, Xu H, Zhao H, Xiong N. Hypoxic cancer-secreted exosomal miR-182-5p promotes glioblastoma angiogenesis by targeting Kruppel-like factor 2 and 4. Mol Cancer Res. 2020;18:1218–31.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  98. 98.

    Matsuura Y, Wada H, Eguchi H, Gotoh K, Kobayashi S, Kinoshita M, Kubo M, Hayashi K, Iwagami Y, Yamada D. Exosomal miR-155 derived from hepatocellular carcinoma cells under hypoxia promotes angiogenesis in endothelial cells. Dig Dis Sci. 2019;64:792–802.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  99. 99.

    Wu F, Li F, Lin X, Xu F, Cui R-R, Zhong J-Y, Zhu T, Shan S-K, Liao X-B, Yuan L-Q. Exosomes increased angiogenesis in papillary thyroid cancer microenvironment. Endocr Relat Cancer. 2019;26:525–38.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  100. 100.

    Mo F, Xu Y, Zhang J, Zhu L, Wang C, Chu X, Pan Y, Bai Y, Shao C, Zhang J. Effects of hypoxia and radiation-induced exosomes on migration of lung cancer cells and angiogenesis of umbilical vein endothelial cells. Radiat Res. 2020. https://doi.org/10.1667/RR15555.1/436363.

    Article  PubMed  Google Scholar 

  101. 101.

    Tadokoro H, Umezu T, Ohyashiki K, Hirano T, Ohyashiki JH. Exosomes derived from hypoxic leukemia cells enhance tube formation in endothelial cells. J Biol Chem. 2013;288:34343–51.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  102. 102.

    Schiffman JD, Fisher PG, Gibbs P. Early detection of cancer: past, present, and future. Am Soc Clin Oncol Educ Book. 2015;35:57–65.

    Article  Google Scholar 

  103. 103.

    Duijvesz D, Luider T, Bangma CH, Jenster G. Exosomes as biomarker treasure chests for prostate cancer. Eur Urol. 2011;59:823–31.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  104. 104.

    Hildonen S, Skarpen E, Halvorsen TG, Reubsaet L. Isolation and mass spectrometry analysis of urinary extraexosomal proteins. Sci Rep. 2016;6:36331.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  105. 105.

    Duijvesz D, Burnum-Johnson KE, Gritsenko MA, Hoogland AM, Vredenbregt-van den Berg MS, Willemsen R, Luider T, Paša-Tolić L, Jenster G. Proteomic profiling of exosomes leads to the identification of novel biomarkers for prostate cancer. PLoS ONE. 2013;8:e82589.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  106. 106.

    Matsumura T, Sugimachi K, Iinuma H, Takahashi Y, Kurashige J, Sawada G, Ueda M, Uchi R, Ueo H, Takano Y. Exosomal microRNA in serum is a novel biomarker of recurrence in human colorectal cancer. Br J Cancer. 2015;113:275.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  107. 107.

    Kucharzewska P, Christianson HC, Welch JE, Svensson KJ, Fredlund E, Ringnér M, Mörgelin M, Bourseau-Guilmain E, Bengzon J, Belting M. Exosomes reflect the hypoxic status of glioma cells and mediate hypoxia-dependent activation of vascular cells during tumor development. Proc Natl Acad Sci. 2013;110:7312–7.

    CAS  PubMed  Article  Google Scholar 

  108. 108.

    Wang W, Qu A, Liu W, Liu Y, Zheng G, Du L, Zhang X, Yang Y, Wang C, Chen X. Circulating miR-210 as a diagnostic and prognostic biomarker for colorectal cancer. Eur J Cancer Care. 2017;26:e12448.

    Article  Google Scholar 

  109. 109.

    Panigrahi GK, Ramteke A, Birks D, Ali HEA, Venkataraman S, Agarwal C, Vibhakar R, Miller LD, Agarwal R, Elmageed ZYA. Exosomal microRNA profiling to identify hypoxia-related biomarkers in prostate cancer. Oncotarget. 2018;9:13894.

    PubMed  PubMed Central  Article  Google Scholar 

  110. 110.

    Altadill T, Campoy I, Lanau L, Gill K, Rigau M, Gil-Moreno A, Reventos J, Byers S, Colas E, Cheema AK. Enabling metabolomics based biomarker discovery studies using molecular phenotyping of exosome-like vesicles. PLoS ONE. 2016;11:e0151339.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  111. 111.

    Dang K, Myers KA. The role of hypoxia-induced miR-210 in cancer progression. Int J Mol Sci. 2015;16:6353–72.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  112. 112.

    Peinado H, Alečković M, Lavotshkin S, Matei I, Costa-Silva B, Moreno-Bueno G, Hergueta-Redondo M, Williams C, García-Santos G, Ghajar CM. Melanoma exosomes educate bone marrow progenitor cells toward a pro-metastatic phenotype through MET. Nat Med. 2012;18:883.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  113. 113.

    Zhao XP, Wang M, Song Y, Song K, Yan TL, Wang L, Liu K, Shang ZJ. Membrane microvesicles as mediators for melanoma-fibroblasts communication: roles of the VCAM-1/VLA-4 axis and the ERK1/2 signal pathway. Cancer Lett. 2015;360:125–33.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  114. 114.

    Zbytek B, Peacock DL, Seagroves TN, Slominski A. Putative role of HIF transcriptional activity in melanocytes and melanoma biology. Dermato Endocrinol. 2013;5:239–51.

    Article  CAS  Google Scholar 

  115. 115.

    Zhou J, Schmid T, Frank R, Brüne B. PI3K/Akt is required for heat shock proteins to protect hypoxia-inducible factor 1α from pVHL-independent degradation. J Biol Chem. 2004;279:13506–13.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  116. 116.

    Jain K, Suryakumar G, Ganju L, Singh SB. Differential hypoxic tolerance is mediated by activation of heat shock response and nitric oxide pathway. Cell Stress Chaperones. 2014;19:801–12.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  117. 117.

    Zhou X, Zhang W, Yao Q, Zhang H, Dong G, Zhang M, Liu Y, Chen J-K, Dong Z. Exosome production and its regulation of EGFR during wound healing in renal tubular cells. Am J Physiol Renal Physiol. 2017;312:F963–70.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  118. 118.

    Datta A, Kim H, Lal M, McGee L, Johnson A, Moustafa AA, Jones JC, Mondal D, Ferrer M, Abdel-Mageed AB. Manumycin A suppresses exosome biogenesis and secretion via targeted inhibition of Ras/Raf/ERK1/2 signaling and hnRNP H1 in castration-resistant prostate cancer cells. Cancer Lett. 2017;408:73–81.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  119. 119.

    Bobrie A, Krumeich S, Reyal F, Recchi C, Moita LF, Seabra MC, Ostrowski M, Théry C. Rab27a supports exosome-dependent and-independent mechanisms that modify the tumor microenvironment and can promote tumor progression. Can Res. 2012;72:4920–30.

    CAS  Article  Google Scholar 

  120. 120.

    Trajkovic K, Hsu C, Chiantia S, Rajendran L, Wenzel D, Wieland F, Schwille P, Brügger B, Simons M. Ceramide triggers budding of exosome vesicles into multivesicular endosomes. Science. 2008;319:1244–7.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  121. 121.

    Kosgodage US, Trindade RP, Thompson PR, Inal JM, Lange S. Chloramidine/bisindolylmaleimide-I-mediated inhibition of exosome and microvesicle release and enhanced efficacy of cancer chemotherapy. Int J Mol Sci. 2017;18:1007.

    PubMed Central  Article  CAS  Google Scholar 

  122. 122.

    Marleau AM, Chen C-S, Joyce JA, Tullis RH. Exosome removal as a therapeutic adjuvant in cancer. J Transl Med. 2012;10:134.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  123. 123.

    Lötvall J, Hill AF, Hochberg F, Buzás EI, Di Vizio D, Gardiner C, Gho YS, Kurochkin IV, Mathivanan S, Quesenberry P. Minimal experimental requirements for definition of extracellular vesicles and their functions: a position statement from the International Society for Extracellular Vesicles. Milton: Taylor & Francis; 2014.

    Google Scholar 

  124. 124.

    Bunggulawa EJ, Wang W, Yin T, Wang N, Durkan C, Wang Y, Wang G. Recent advancements in the use of exosomes as drug delivery systems. J Nanobiotechnol. 2018;16:1–13.

    Article  CAS  Google Scholar 

  125. 125.

    Johnsen KB, Gudbergsson JM, Skov MN, Pilgaard L, Moos T, Duroux M. A comprehensive overview of exosomes as drug delivery vehicles—endogenous nanocarriers for targeted cancer therapy. Biochimica et Biophysica Acta (BBA) Reviews Cancer. 2014;1846:75–87.

    CAS  Article  Google Scholar 

  126. 126.

    Zhuang X, Xiang X, Grizzle W, Sun D, Zhang S, Axtell RC, Ju S, Mu J, Zhang L, Steinman L. Treatment of brain inflammatory diseases by delivering exosome encapsulated anti-inflammatory drugs from the nasal region to the brain. Mol Ther. 2011;19:1769–79.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  127. 127.

    Aryani A, Denecke B. Exosomes as a nanodelivery system: a key to the future of neuromedicine? Mol Neurobiol. 2016;53:818–34.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  128. 128.

    Jiang X-C, Gao J-Q. Exosomes as novel bio-carriers for gene and drug delivery. Int J Pharm. 2017;521:167–75.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  129. 129.

    Alvarez-Erviti L, Seow Y, Yin H, Betts C, Lakhal S, Wood MJA. Delivery of siRNA to the mouse brain by systemic injection of targeted exosomes. Nat Biotechnol. 2011;29:341–5.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  130. 130.

    Pascucci L, Coccè V, Bonomi A, Ami D, Ceccarelli P, Ciusani E, Viganò L, Locatelli A, Sisto F, Doglia SM. Paclitaxel is incorporated by mesenchymal stromal cells and released in exosomes that inhibit in vitro tumor growth: a new approach for drug delivery. J Control Release. 2014;192:262–70.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  131. 131.

    Jung KO, Jo H, Yu JH, Gambhir SS, Pratx G. Development and MPI tracking of novel hypoxia-targeted theranostic exosomes. Biomaterials. 2018;177:139–48.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  132. 132.

    Chen X, Zhou J, Li X, Wang X, Lin Y, Wang X. Exosomes derived from hypoxic epithelial ovarian cancer cells deliver microRNAs to macrophages and elicit a tumor-promoted phenotype. Cancer Lett. 2018;435:80–91.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  133. 133.

    Mace TA, Collins AL, Wojcik SE, Croce CM, Lesinski GB, Bloomston M. Hypoxia induces the overexpression of microRNA-21 in pancreatic cancer cells. J Surg Res. 2013;184:855–60.

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  134. 134.

    Umezu T, Tadokoro H, Azuma K, Yoshizawa S, Ohyashiki K, Ohyashiki JH. Exosomal miR-135b shed from hypoxic multiple myeloma cells enhances angiogenesis by targeting factor-inhibiting HIF-1. Blood J Am Soc Hematol. 2014;124:3748–57.

    CAS  Google Scholar 

  135. 135.

    Schlaepfer IR, Nambiar DK, Ramteke A, Kumar R, Dhar D, Agarwal C, Bergman B, Graner M, Maroni P, Singh RP. Hypoxia induces triglycerides accumulation in prostate cancer cells and extracellular vesicles supporting growth and invasiveness following reoxygenation. Oncotarget. 2015;6:22836.

    PubMed  PubMed Central  Article  Google Scholar 

  136. 136.

    Panigrahi GK, Praharaj PP, Peak TC, Long J, Singh R, Rhim JS, Elmageed ZYA, Deep G. Hypoxia-induced exosome secretion promotes survival of African-American and Caucasian prostate cancer cells. Scientific reports. 2018;8:1–13.

    Article  CAS  Google Scholar 

  137. 137.

    Huang Z, Feng Y. Exosomes derived from hypoxic colorectal cancer cells promote angiogenesis through Wnt4-induced β-catenin signaling in endothelial cells. Oncol Res Featuring Preclin Clin Cancer Therapeutics. 2017;25:651–61.

    Article  Google Scholar 

  138. 138.

    Svensson KJ, Kucharzewska P, Christianson HC, Sköld S, Löfstedt T, Johansson MC, Mörgelin M, Bengzon J, Ruf W, Belting M. Hypoxia triggers a proangiogenic pathway involving cancer cell microvesicles and PAR-2–mediated heparin-binding EGF signaling in endothelial cells. Proc Natl Acad Sci. 2011;108:13147–52.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  139. 139.

    Horie K, Kawakami K, Fujita Y, Sugaya M, Kameyama K, Mizutani K, Deguchi T, Ito M. Exosomes expressing carbonic anhydrase 9 promote angiogenesis. Biochem Biophys Res Commun. 2017;492:356–61.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  140. 140.

    Shan Y, You B, Shi S, Shi W, Zhang Z, Zhang Q, Gu M, Chen J, Bao L, Liu D. Hypoxia-induced matrix metalloproteinase-13 expression in exosomes from nasopharyngeal carcinoma enhances metastases. Cell Death Dis. 2018;9:1–13.

    Article  CAS  Google Scholar 

  141. 141.

    Ye SB, Zhang H, Cai TT, Liu YN, Ni JJ, He J, Peng JY, Chen QY, Mo HY, Zhang XS. Exosomal miR-24-3p impedes T-cell function by targeting FGF11 and serves as a potential prognostic biomarker for nasopharyngeal carcinoma. J Pathol. 2016;240:329–40.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  142. 142.

    Berchem G, Noman MZ, Bosseler M, Paggetti J, Baconnais S, Le Cam E, Nanbakhsh A, Moussay E, Mami-Chouaib F, Janji B. Hypoxic tumor-derived microvesicles negatively regulate NK cell function by a mechanism involving TGF-β and miR23a transfer. Oncoimmunology. 2016;5:e1062968.

    PubMed  Article  CAS  PubMed Central  Google Scholar 

  143. 143.

    Xue M, Chen W, Xiang A, Wang R, Chen H, Pan J, Pang H, An H, Wang X, Hou H. Hypoxic exosomes facilitate bladder tumor growth and development through transferring long non-coding RNA-UCA1. Mol Cancer. 2017;16:143.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  144. 144.

    Li L, Li C, Wang S, Wang Z, Jiang J, Wang W, Li X, Chen J, Liu K, Li C. Exosomes derived from hypoxic oral squamous cell carcinoma cells deliver miR-21 to normoxic cells to elicit a prometastatic phenotype. Can Res. 2016;76:1770–80.

    CAS  Article  Google Scholar 

Download references

Acknowledgements

Not applicable.

Funding

Not applicable.

Author information

Affiliations

Authors

Contributions

RJ and JR conceived the ideas. JR, MA and MH collected data. RR and JR designed and reviewed the manuscript. All authors reviewed the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Jafar Rezaie.

Ethics declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Jafari, R., Rahbarghazi, R., Ahmadi, M. et al. Hypoxic exosomes orchestrate tumorigenesis: molecular mechanisms and therapeutic implications. J Transl Med 18, 474 (2020). https://doi.org/10.1186/s12967-020-02662-9

Download citation

Keywords

  • Hypoxia
  • Exosomes
  • HIF
  • Tumor microenvironment
  • Tumorigenesis