A novel pathway involving melanoma differentiation associated gene-7/interleukin-24 mediates nonsteroidal anti-inflammatory drug-induced apoptosis and growth arrest of cancer cells

Numerous studies show that nonsteroidal anti-inflammatory drugs (NSAIDs) are effective in chemoprevention or treatment of cancer. Nevertheless, the mechanisms underlying these antineoplastic effects remain poorly understood. Here, we report that induction of the cancer-specific proapoptotic cytokine melanoma differentiation associated gene-7/interleukin-24 (MDA-7/IL-24) by several NSAIDs is an essential step for induction of apoptosis and G ₂-M growth arrest in cancer cells in vitro and inhibition of tumor growth in vivo. We also show that MDA-7/IL-24-dependent up-regulation of growth arrest and DNA damage inducible 45 α (GADD45α) and GADD45γ gene expression is sufficient for cancer cell apoptosis via c-Jun NH ₂-terminal kinase (JNK) activation and growth arrest induction through inhibition of Cdc2-cyclin B checkpoint kinase. Knockdown of GADD45α and GADD45γ transcription by small interfering RNA abrogates apoptosis and growth arrest induction by the NSAID treatment, blocks JNK activation, and restores Cdc2-cyclin B kinase activity. Our results establish MDA-7/IL-24 and GADD45α and GADD45γ as critical mediators of apoptosis and growth arrest in response to NSAIDs in cancer cells.