c-Src dependency of NSAID-induced effects on NF-κB-mediated apoptosis in colorectal cancer cells

Long-term aspirin or related non-steroidal anti-inflammatory drugs (NSAIDs) ingestion can protect against colorectal cancer (CRC). NSAIDs have a pro-apoptotic activity and we have shown that stimulation of the nuclear factor-kappaB (NF-kappa B) pathway is a key component of this pro-apoptotic effect. However, the upstream pathways have yet to be fully elucidated. Here, we demonstrate that aspirin activates the c-Src tyrosine kinase pathway in CRC cells. We show that c-Src activation occurs in a time-and dose-dependent manner, preceding aspirin-mediated degradation of I kappa B alpha, nuclear/nucleolar translocation of NF-kappa B/RelA and induction of apoptosis. Furthermore, inhibition of c-Src activity, by chemical inhibition or expression of a kinase dead form of the protein abrogates aspirin-mediated degradation of I kappa B alpha, nuclear translocation of RelA and apoptosis, suggesting a causal link. Expression of constitutively active c-Src mimics aspirin-induced stimulation of the NF-kappa B pathway. The NSAIDs sulindac, sulindac sulphone and indomethacin all similarly activate a c-Src-dependent NF-kappa B and apoptotic response. These data provide compelling evidence that c-Src is an upstream mediator of aspirin/NSAID effects on NF-kappa B signalling and apoptosis in CRC cells and have relevance to the development of future chemotherapeutic/chemopreventative agents.