The gut microbiota metabolite urolithin A, but not other relevant urolithins, induces p53-dependent cellular senescence in human colon cancer cells.

The promotion of senescence in cancer cells by dietary (poly)phenols gained attention as a promising chemopreventive strategy against colorectal (CRC) and other cancers. Urolithins (Uros) are ellagitannins and ellagic acid-derived gut microbiota metabolites that reach high concentrations in the human colon. They were postulated to be as potential anticancer agents in different CRC models, but their role as promoters of cellular senescence has never been comprehensively evaluated. We evaluated long-term senescent-mediated chemoprevention of physiologically relevant doses of different Uros and representative mixtures of human urolithin metabotypes in human CRC (HCT-116, Caco-2, and HT-29) and non-tumorigenic (CCD18-Co) cell lines. Our results show that Uro-A (but not Uro-C, IsoUro-A, or Uro-B) leads to a dose-dependent anti-clonogenic effect through the increase of the senescence-associated β-galactosidase activity, rather than by reversible cell cycle arrest and(or) apoptosis which require much higher concentrations. Senescence was accompanied by an elevated p53 and p21^Cip1/Waf1 expression in HCT-116 cells (p53-wild type), but not in other CRC lines with p53 mutated or non-tumorigenic cells, which suggests that long-term senescence-mediated chemoprevention is a p53-dependent manner. Moreover, the ATP-binding cassette transporters and the phase-II metabolism of Uros limited the induction of senescence, which anticipates lower effects of conjugated Uros against systemic cancers.