Abstract: The model of subcutaneous transplantation tumor from human hepatoma cells SMMC-7721 in nude mice was established.Each nude mice was injected with magnesium cantharidate (6.26×10^-5 mmol) around the tumor in experimental group,while the same volume of sterile saline was injected as control group.After administration for 22 days,the effect of magnesium cantharidate on the proliferation of subcutaneous transplantation tumor was observed.On the basis of that,the histomorphologic characteristics of subcutaneous transplantation tumor in nude mice was observed by HE staining.HE staining showed that the volume of transplantation tumor cells in magnesium cantharidate group became smaller,cytoplasm pyknosis,acidophilic degeneration,nuclear pyknosis and fragmentation.The ultra-structural changes of subcutaneous transplantation tumor in nude mice was observed by transmission electron microscopy.The results showed that the nuclear membrane of transplantation tumor in magnesium cantharidate group disappeared,chromatin gathered together,etc.The expression level of bcl-2 and bax was detected by Two-step immunohistochemistry.The results showed that the expression of bcl-2 in magnesium cantharidate group was obviously lower,but the expression of bax was higher than that of control group (P<0.05).The study indicated that magnesium cantharidate can inhibit the proliferation of subcutaneous transplantation tumor from human hepatoma cells in nude mice and induce the apoptosis of transplantation tumor cells.The mechanism may be related with the up-regulation of the expression of bax and down-regulation of the expression of bcl-2.

Key words: magnesium cantharidate, nude mice, subcutaneous transplantation tumor, cell apoptosis