UVB-activated indole-3-acetic acid induces apoptosis of PC-3 prostate cancer cells

Indole-3-acetic acid (IAA) has recently shown anticancer activity in combination with horseradish peroxidase. The current study demonstrated that IAA irradiated with ultraviolet B (IAA(UVB)) is able to generate free radicals and induce cell death in a time-dependent fashion in PC-3 prostate cancer cells, while PC-3 cells treated with IAA alone exhibited no toxic responses. It was also found through Western blot analysis that the cytotoxic effect of IAA(UVB) resulted from apoptosis. Treatment with IAA(UVB) for 24 hours showed a significant increase in phosphorylated p38 mitogen-activated protein kinase and c-Jun N-terminal kinase, the stress signaling proteins. Furthermore, pro-caspases (-3, -8, and -9) were clearly down-regulated and poly(ADP-ribose) polymerase cleavages were demonstrated in the group treated with IAA(UVB). Flow cytometric analysis also demonstrated the induction of apoptosis by IAA(UVB) in PC-3 cells. In conclusion, this study demonstrated that IAA induced cell death in combination with UVB irradiation by increasing apoptosis in PC-3 cells.