Fig. 2

ER stress sensors or signals triggering MDSC activation and immunosuppression may serve as targets in immunotherapy in cancers. In lung carcinoma or metastasis cancer, CHOP, PERK, and TRAIL-Rs could be targeted by inhibitors that reduce MDSCs by inhibiting ER stress. sXBP1/ATF3/CHOP/ROS/Arg I signaling activated LOX-1+CD15+ PMN-MDSCs in Hepatocellular carcinoma. sXBP1 is one of the most important sensors in ER stress. Targeting sXBP1 signaling could reduce the immunosuppression of MDSCs in HCC and Melanoma. IRE1α, one of ER stress sensors, could also be an inhibitory target in Ovarian carcinoma. 4-Phenylbutyric acid (4-PBA), a chemical chaperone widely used as an ER stress reducer, attenuated Tg-induced MDSC expansion and tumor growth in melanoma