Selective Senolysis of 5FU-Induced CRC Senescent Cells by Piceatannol Through Mitochondrial Depolarization and AIF-Dependent Apoptosis

Chemotherapy-induced senescence (CIS) contributes to tumor persistence and relapse. In this study, we investigated the senolytic activity of piceatannol (PCT) in 5-fluorouracil (5FU)-induced senescent colorectal cancer (CRC) cells. Senescence was established in P53-proficient HCT116 cells and normal colon fibroblasts (CCD18Co) following prolonged 5FU exposure, as shown by increased SA-β-gal activity, upregulation of P16, P21, and P53, mitochondrial depolarization, and enhanced oxidative stress. Subsequent PCT treatment selectively induced apoptosis in senescent populations, while non-senescent or p53-mutant, senescence-resistant HT29 cells were minimally affected. This effect was prevented by N-acetylcysteine, indicating a redox-sensitive mechanism. Mechanistically, PCT triggered mitochondrial depolarization and AIF-associated, caspase-independent apoptosis without increasing ROS. Morphological analysis with MitoTracker and quantitative morphometry using Fiji confirmed a fragmented mitochondrial network, characterized by reduced form factor, length, and number per cell. Western blotting revealed downregulation of fusion proteins (MFN1, MFN2), decreased FIS1, stable DRP1, and marked upregulation of the DRP1 adaptor MFF, consistent with suppressed fusion and enhanced fission competence. Together, these findings demonstrate that PCT selectively targets chemotherapy-induced senescent CRC cells through mitochondrial fragmentation and AIF-dependent apoptosis, highlighting its potential as an adjuvant strategy to limit the long-term burden of therapy-induced senescence.