Fig 1: OxPhos inhibition sensitizes irinotecan-resistant cells to irinotecan. (a) The effect of 5 µM gossypol and 100 µM phenformin on irinotecan-resistant A549 (A549R) cells after 48 h was determined by SRB assay (n = 3). (b) Increased protein level of ALDH1L1 on irinotecan-resistant A549 (A549R) cells as analyzed by immunoblotting. (c–d) The effect of 40 µM ALDH1L1 siRNA treatment for 72 h and irinotecan treatment for 48 h on A549 and A549R cells was determined by SRB assay (n = 3). (e) Increased protein levels of oxphos complexes were analyzed after transient treatment of 200 µM irinotecan on A549 cells by immunoblotting. (f) Transient treatment of 200 µM irinotecan on A549 cells increased mitochondrial membrane potential, as determined by TMRE staining and flow cytometry (n = 3). Each bar represents the mean + s.d. *p < 0.05, **p < 0.01, ***p < 0.001.