Soy soluble polysaccharide induces apoptosis in HCT-116 human colon cancer cells via reactive oxygen species generation

Abstract

Previous studies have suggested that soy sauce contains specific bioactive components and various biological activities of soy sauce have been observed. Soy soluble polysaccharide (SSPS), a predominant bioactive compound in soy sauce, has numerous pharmacological actions, including anti-inflammatory and immunomodulating activities. In the current study, the apoptotic effects of SSPS were investigated in HCT-116 human colon cancer cells. Treatment with SSPS significantly inhibited cell growth in a concentration-dependent manner by inducing apoptosis but not necrosis. This induction was associated with the generation of reactive oxygen species (ROS), mitochondrial dysfunction, activation of caspases and cleavage of the poly (ADP-ribose) polymerase protein. Induction of apoptotic cell death of HCT-116 cells by SSPS showed a correlation with the downregulation of members of the inhibitor of apoptosis protein family, including X-linked inhibitor of apoptosis protein and antiapoptotic Bcl-2, and upregulation of Bax and Bad. Administration of N-acetyl-L-cysteine, a scavenger of ROS, significantly decreased SSPS-induced apoptosis. These results indicate a critical role of signaling cascades involving a ROS-mediated caspase pathway in the anticancer effects of SSPS.