Anti-angiogenesis effect of melittin on Mock/MHCC97-H cells by the regulation of cathepsin S in vivo

Objective: To study the anti-angiogenesis effect of melittin on human hepatoma Mock/MHCC97-H cells by regulating the expression of cathepsin S (CatS) in vivo. Methods: Models of in situ transplantation tumor of Mock/MHCC97-H cells and silencing cathepsin shRNA-CatS/ MHCC97-H cells in nude mice were established. The model mice were randomly divided into four groups. In the A1 group, the mice were inoculated with shRNA-CatS/MHCC97-H cells and treated with melittin. In the A2 group, the mice were inoculated with shRNA-CatS/MHCC97-H cells and treated with saline. In the B1 group, the mice were inoculated with Mock/MHCC97-H cells and treated with melittin. In the B2 group, the mice were inoculated with Mock/MHCC97-H cells and treated with saline. The A1 and B1 group were injected with melittin (80 mg/kg) intraperitoneally every day. The A2 and B2 group were injected with 0.2 mL normal saline intraperitoneally every day. After administration for 25 days, the animals were sacrificed. The tumor size and weight in nude mice in each group were recorded. The expression of CD34 protein in the xenograft tumor tissues was detected by immunohistochemistry. The expression of Cat S, VEGF-A, p-VEGFR2, Ras, Raf, p-Raf, MEK1, p-MEK1, ERK1/2 and p-ERK1/2 proteins were detected by western blot. Results: The B1 group had significantly smaller tumor volumes and lower tumor weights than the B2 group (both P 0.001). There was no significant difference between the A1 group and A2 group in tumor volumes and weights. The number of CD34-positive microvessels in the B2 group was significantly higher than that in the A2 group (P 0.001). The number of CD34-positive microvessels in the B1 group was significantly lesser than that in the A1 group (P 0.001). Most strikingly, in the model featuring inoculation of Mock/MHCC97-H cells, CatS, VEGF-A, p-VEGFR2, Ras, Raf, p-Raf, MEK1, p-MEK1, ERK1/2 and p-ERK1/2 expression were inhibited when treated with melittin. However, in the model featuring the inoculation of shRNA-CatS/MHCC97-H cells, no such effects were observed with similar treatments. Conclusion: Melittin can inhibit the growth of tumors and angiogenesis by blocking the CatS-VEGf-A signaling pathway.