Senotoxins target senescence via lipid binding specificity, ion imbalance and lipidome remodeling

Senescence is a driver of aging and a barrier to tumor progression, but its persistent accumulation drives inflammation and relapse. Thus, the success of chemotherapy could be jeopardized when senescence emerges in the tumor microenvironment. Here we identified the senolytic properties of a pore-forming toxin, sticholysin I (StnI). StnI and our engineered improved form, StnIG, selectively hampers viability of chemotherapy-induced senescent cancer cells, as well as senescent primary cells. We show that its selectivity is mediated by specific binding and lipid ratios associated with senescence, including compromised membrane bilayer asymmetry. Mechanistically, StnIG triggers sodium and calcium influx and an enduring potassium efflux in senescent cells. Calcium triggers the opening of calcium-activated potassium channels, leading to cell death by apoptosis and pyroptosis. Finally we show that StnIG synergizes with senescence-inducing chemotherapy to drive remission of solid tumors in mice. Our findings define StnI and StnIG as senotoxins with translational potential for cancer therapy.