Figure 5. Maf1 overexpression suppresses UPRmt-induced IR resistance in A549 cells. (A, B) EtBr activates UPRmt in the presence of rapamycin. A549 cells were treated with indicated drugs or/and IR. UPRmt marker genes (HSP60 and mtHSP70) were examined by RT-qPCR. (C, D) Maf1 overexpression (oe) prevents EtBr from increasing HSP60 and mtHSP70 expression in the present of rapamycin and IR. (E, F) Maf1(oe) sensitizes A549 cells to IR and is not additive to rapamycin. A549 cells (500 cells/plate) stably expressed Maf1 were treated with rapamycin and IR, then allowed to form colonies for 2 weeks. A549 cells were plated at 50 cells/plate as non-irradiated controls. Representative data are shown in (E) and the quantifications of 3 biological replicates in (F). (G) High expression of UPRmt marker genes (HSP60 and mtHSP70) are significantly associated with poor prognosis in lung adenocarcinoma (LAUD) patients. (H) A working model showing the role of Maf1-UPRmt in mediating rapamycin’s enhancing effect on IR sensitivity. For all bar graph, the error bars stand for Standard Deviation (SD) of the mean. Statistical significance was evaluated by 2-tailed, paired student’s t-test (ns, not significant, *, P<0.05, **, P<0.01).