Sorbus commixta water extract induces apoptotic cell death via a ROS-dependent pathway

The stembark of Sorbus commixta Hedl. has been used for treating asthma, bronchitis, gastritis and edema. However, the anticancer and proapoptotic effects of the water extract of the stembark of S. commixta (SCE) remain unknown. In the present study, it was shown that SCE inhibited the cell viability of the hepatocellular carcinoma cell lines Hep3B and HepG2, and of the colon carcinoma cell line HCT116. DNA content analysis indicated that SCE increased the sub-G1 population of HCT116 cells. In addition, degradation of nuclear DNA and levels of proapoptotic cascade components, including caspase-9, caspase-3 and poly ADP-ribose polymerase, were augmented by SCE treatment. Mitochondrial membrane potential and the ratio of B-cell lymphoma-2 (Bcl-2)/Bcl-2-associated X protein (Bax) were also reduced. Furthermore, SCE increased the expression of proapoptotic proteins, including p21, p27 and p53. Mouse double minute 2 homology, a negative regulator of p53, was cleaved by SCE treatment. Intracellular reactive oxygen species (ROS) production was also increased by SCE treatment. However, the SCE-induced cytotoxic effects and the increased expression of proapoptotic proteins, including p53 and p21, and reduced Bcl-2/Bax ratio, could be attenuated by N-acetyl cysteine, an ROS inhibitor. Taken together, these results indicate that SCE is a potent proapoptotic herbal medicine, which exerts its effects via the ROS-mediated mitochondrial pathway.