Ophiopogonin B induces the autophagy and apoptosis of colon cancer cells by activating JNK/c-Jun signaling pathway.

OBJECTIVE: To investigate the effect of Ophiopogonin B (OP-B) on the autophagy and apoptosis of colon cancer cells via the regulation of JNK/c-Jun signaling pathway.

METHODS: Colon cancer cell lines (HT-29 and HCT-116) were treated with various concentrations of OP-B (0, 5, 10and 20 μmol/l) and JNK inhibitor SP600125. MTT assay, flow cytometry, immunofluorescence staining were used to detect the biological function ofHT-29 and HCT-116 cells, and expressions of autophagy-,apoptotic- and pathway-related proteins were measured by Western Blot. Moreover, a nude mice model with transplanted tumor was used to observe the effect of OP-B on the growth, autophagy and apoptosis of the transplanted tumor of colon cancer.

RESULTS: The results demonstrated that OP-B suppressed the proliferation of HT-29 and HCT-116 cell lines through the G0/G1 phase cell cycle arrest. Moreover, OP-B induced apoptosis by inhibiting the expression of Bax and cleaved caspase 3 and promoting the expression of Bcl-2. Treatment with OP-B also increased the expression of Beclin 1 and the conversion of LC3I to LC3II with the activation of JNK/c-Jun signaling pathway, but reduced the expression of P62, whereas SP600125 (an inhibitor of JNK) reversed these process. In addition, the xenograft model using HCT-116 cells provided further evidence of the inhibition of OP-B on tumor proliferation. Immunohistochemistry detection verified that OP-B enhance the positive expression rate of LC3, and increase the apoptosis index of tumor cells in vivo. Importantly, all these changes induced by OP-B were clearly in a dose-dependent manner.

CONCLUSION: OP-B may induce cell autophagy, apoptosis and cell cycle arrest by activating the JNK/ c-Jun signaling pathway, thereby inhibiting the growth of colon cancer.