CASP9 and esophageal cancer: In this study, Rk3 induced apoptosis in esophageal cancer cells through activation of Bax, cytochrome-C, cleaved caspase-3, cleaved caspase-9 and PARP and decreased the protein expression levels of Bad and Bcl-2, indicating that Rk3 induced apoptosis by triggering the intrinsic mitochondrial pathway in esophageal cells.