Esculetin induces death of human colon cancer cells via the reactive oxygen species-mediated mitochondrial apoptosis pathway

The present study investigated the apoptotic effects of esculetin, a coumarin derivative, on the human colon cancer cell line HT-29. Esculetin had cytotoxic effects on HT-29 cells in a dose- and time-dependent manner; treatment with 55 μg/mL esculetin reduced cell viability by 50%. Esculetin induced apoptosis, as evidenced by apoptotic body formation, an increased percentage of cells in sub-G1 phase, and DNA fragmentation. Moreover, esculetin increased mitochondrial membrane depolarization, released cytochrome c into cytosol, and modulated the expression of apoptosis-associated proteins, resulting in reduced expression of B cell lymphoma-2, increased expression of Bcl-2-associated X protein, and activation of caspase-9 and caspase-3. Esculetin induced the formation of reactive oxygen species; however, treatment with an antioxidant reduced the apoptotic cell death induced by esculetin treatment. In addition, esculetin activated mitogen-activated protein kinases and specific inhibitors of these kinases abrogated the reduction in cell viability induced by esculetin treatment.