[Inhibitory effect of magnesium cantharidate on human hepatoma SMMC-7721 cell proliferation by blocking MAPK...

Objective To investigate the anticancer mechanism of magnesium cantharidate by observing its effect on the mitogen-activated protein kinase (MAPK) signaling pathway in human hepatoma SMMC-7721 cells. Methods The protein phosphatase 2A (PP2A) activity detection kit was used to detect the effects of magnesium cantharidate and okadaic acid (OA) on PP2A activity. After the treatment of SMMC-7721 cells with magnesium cantharidate and/or OA, mRNA levels of extracellular signal-regulated kinase 1 (ERK1), ERK2, p38MAPK, c-Jun N-terminal kinase 1 (JNK1) and JNK2 were detected by real-time quantitative PCR, and the protein expression levels and protein phosphorylation of ERK1, ERK2, p38 MAPK and JNK were determined by Western blotting. Results The effect of magnesium cantharidate on the activity of PP2A in SMMC-7721 cells was not evident at the concentration of 0.283 μmol/L, but the activity of PP2A was declined significantly at 0.567 μmol/L or higher concencentrations in a concentration-dependent manner. Likewise, OA also displayed apparent inhibitory effect on the activity of PP2A at 0.059 nmol/L. Compared with the control group, mRNA levels of ERK1 and ERK2 were not changed by magnesium cantharidate at 0.283 μmol/L, but they significantly declined at the concentrations greater than 0.567 μmol/L. In contrast, mRNA levels of ERK1 and ERK2 were significantly elevated by 0.059 nmol/L OA. mRNA levels of p38MAPK, JNK1 and JNK2 significantly increased after the treatment of 0.059 nmol/L OA or magnesium cantharidate at varying concentrations. Compared with the control group, phosphorylation levels of ERK1 and ERK2 were not changed by 0.283 μmol/L magnesium cantharidate, but decreased significantly when the concentration was 0.567 μmol/L or above. In contrast, the phosphorylation levels of ERK1 and ERK2 showed a significant increase in 0.059 nmol/L OA treated group. The phosphorylation levels of p38 MAPK, JNK1 and JNK2 were also significantly increased by 0.059 nmol/L OA or magnesium cantharidate in a concentration-dependent manner. Conclusion Magnesium cantharidate may inhibit the proliferation of SMMC-7721 cells by inhibiting the activity of PP2A and ERK1/2 signaling pathway.