Studies have shown that the expression of inhibitor of differentiation (Id-1) is increased in
bladder cancer and is associated with drug resistance.
S-allylmercaptocysteine (SAMC), a water-soluble component of garlic, is known to have a potent
therapeutic effect on human
cancer. The aim of this study was to investigate whether Id-1 expression mediates SAMC-induced cell death in
bladder cancer cells. After generating stable Id-1-expressing and si-Id-1 transfectants in various
bladder cancer cell lines, cell sensitivity to SAMC was compared by colony formation and MTT assays. The results indicated that Id-1 overexpression reduced the positive effect of SAMC on cell survival, while the inactivation of Id-1 increased cellular susceptibility to SAMC. Using
DAPI staining, the apoptosis of
bladder cancer cells induced by SAMC was shown to be negatively regulated by Id-1 expression. The expression of apoptosis-related
proteins analyzed by Western blotting further supported the negative role of Id-1 in SAMC-induced apoptosis. Furthermore, by
wound closure and
type I collagen invasion assays, the inhibitory effect of SAMC on the invasion and migration of
bladder cancer cells was found to be associated with the down-regulation of Id-1. Our results demonstrated that SAMC-induced apoptosis is associated with the Id-1 pathway, and that the inactivation of Id-1 enhances the ability of SAMC to inhibit the survival, invasion and migration of
bladder cancer cells. These findings may lead to the development of novel therapeutic strategies for the treatment of
bladder cancer.