SRC skews cell fate from apoptosis to senescence

Cells responding to DNA damage implement complex adaptive programs that often culminate in two distinct outcomes: apoptosis or senescence. Here, to systematically identify factors driving each response, we analyzed human IMR-90 fibroblasts exposed to increasing doses of the genotoxin etoposide. We identified SRC as a key kinase contributing to this decision fork. SRC was activated by low (50 μM) etoposide but not by high (200 μM) etoposide levels. At low DNA damage, SRC-mediated activation of p38 critically promoted cell survival and senescence, and increased pro-survival BCL2L2 levels, while SRC-mediated repression of p53 prevented a rise in pro-apoptotic PUMA levels. At high DNA damage, SRC was not active, leading to elevation of p53, inhibition of p38, and apoptosis. In mice exposed to DNA damage, pharmacologic inhibition of SRC prevented the tissue accumulation of senescent cells. Inhibiting SRC could be exploited for inducing senescent-cell apoptosis in tissues to improve health outcomes. Human IMR-90 fibroblasts were exposed to low (50 μM) or high (200 μM) doses of the genotoxin etoposide for 48 hours, and compared to control IMR-90 cells.