MCM6 and cancer: To investigate whether a reduction in readthrough also applies to the senescent response induced by chemotherapeutic drugs in cancer cells (therapy-induced senescence: TIS) we treated PC3 prostate cancer cells with camptothecin for 24 h and confirmed that most of the cell population was senescent using the SA-β-Gal assay and western blots for phospho-RB, MCM6 and pH3(S10) (Fig. 6A,B).