Thus, large chemical libraries could be readily screened in P‐gp‐overexpressing cells while searching for efficient restoration of MitoTracker Red fluorescence, which would be used as an indication for successful inhibition of P‐gp efflux activity, thus facilitating the development of MDR chemosensitizers for effective reversal of P‐gp‐mediated cancer MDR, which continues to be a major hindrance to curative chemotherapy of various human malignancies. This evidence concerns the gene PGP and cancer.