Epidermal growth factor protects epithelial-derived cells from tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis by inhibiting cytochrome c release.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in combination with chemotherapeutic drugs induces a synergistic apoptotic response in cancer cells. TRAIL death receptors have also been implicated in chemotherapeutic drug-induced apoptosis. This has lead to TRAIL being proposed as a potential cancer treatment. In nude mice injected with human tumors, TRAIL reduces the size of these tumors without toxic side effects. We demonstrate that the epidermal growth factor (EGF) stimulation of human embryonic kidney cells HEK 293 and breast cancer cell line MDA MB 231 effectively protects these cells from TRAIL-induced apoptosis in a dose-dependent manner. This stimulation blocks apoptosis by inhibiting TRAIL-mediated cytochrome c release from the mitochondria and caspase 3-like activation. EGF survival response involves the activation of AKT. Expression of activated AKT was sufficient to block TRAIL-induced apoptosis, and kinase-inactive AKT expression blocked EGF-protective response. In contrast, inhibition of EGF stimulation of extracellular-regulated kinase (ERK) activity did not affect EGF protection. These findings indicate that EGF receptor activation provides a survival response against TRAIL-induced apoptosis by inhibiting mitochondrial cytochrome c release that is mediated by AKT activation in epithelial-derived cells.