Fig. 2

Chemotherapy resistance and mtDNA-depleted ESCC. A mtDNA-depleted cells had significantly decreased sensitivity to cisplatin (CDDP), 5-fluorouracil (5-FU), and docetaxel (DTX) compared with control cells. B The rate of apoptosis was lower in mtDNA-depleted ESCC than in control cells (apoptosis rate under CDDP 0 µM; control-sh: 5.8%, tfam-sh1: 5.0%, tfam-sh2: 3.8%, apoptosis rate under CDDP 5 µM; control-sh: 23.3%, tfam-sh1: 10.1%, tfam-sh2: 6.0%). C, D ESCC cells cultured with CDDP and 5-FU long-term were resistant to chemotherapy. Moreover, the mtDNA copy number of CDDP- and 5-FU-resistant cell lines was lower than that of control cells by PCR, and there was significantly difference between CDDP-resistant cell lines and control cells. E TE8 control cells and mtDNA-depleted TE8 cells were cultured for 14 days and then injected into BALB/cAJcl nude mice treated with intraperitoneal injection of saline or CDDP every 3–4 days. F The proliferation of control cells and mtDNA-depleted ESCC cells was analyzed by WST assay. Control cells in mice treated with saline injection proliferated more than mtDNA-depleted ESCC cells. On the other hand, mtDNA-depleted ESCC cells had higher in tumor volume after CDDP injection than control cells. The physical changes were in line with the results of the WST assay