Experimental Study Of Exogenous Somatostatin On Proliferation Of Human Hepatic Carcinoma Cell

Hepatic cellular carcinoma (HCC) is one of the most severe malignant tumors that threaten human health and life. It is characterized as its insidious onset, rapid growth, short life span, high mortality and unfavourable prognosis. The majority of the patients who suffer the hepatic carcinoma couldn't receive the operation when they were diagnosed. Lots of therapeutic regimens are available for that patients, for instance, transcatheter hepatic arterial chemoembolization, radar therapy, radiotherapy, etc. But the therapeutic effect are still unsatisfactory.Somatostatin (SST), one kind of the polypeptide antibiotics, has extensive biologic activity. It reacts both from the aspect of classic internal hormone by blood circulation, and the effect of local regulation as neurotransmitter. Scientists have synthesised lots of somatostatin analog (SSTA) as octreotide on the base of definiting the functional groups and structure of somatostatin. SSTA has the benefits of specificity, long plasma half-life, duration and safety compared with SST. At present, we have received some effects on the malignant tumours'treatment of SSTA in experimental study. But the mechanism of action are still not clear. It may effect both from direct pathway by combining the somatostatin receptor (SSTR) and the indirect pathway as inhibiting tumor-promoting factor. It is reported that it not only has the strong depressant effect on neuroendocrine tumor ( eg. Neuroendocrine, insulinoma), but also has the same effect on entity tumor as gastric cancer, colon carcinoma, prostatic carcinoma, pancreatic carcinoma, melanoma and so on. Recently, researchers have done lots of further investigation on the base of the tumor inhibition effect of SST, but its effect on hepatic carcinoma was rarely reported.In our experiment, we chose the octreotide as the pharmaceutical preparation and the human hepatic carcinoma cell line BEL-7402 as the research target. Investigated the effect on cell proliferation of somatostatin in different concentration and discussed the mechanism of the action.At first, we detected the cytoactive by CCK-8 (Cell Counting Kit-8) and discovered that the absorbance of experimental groups with octreotide in medium and high concentration were lower than control groups, with concentration dependency. And the absorbance of each experimental groups were still lower than their control groups after 24h,48h,72h,96h and 120h with time dependency. However, the absorbance of experimental groups with octreotide in low concentration didn't have the statistic contrast compared with their control groups. To verify the effect on cell proliferation of somatostatin and discuss the mechanism of action further, we detected the cell cycle of hepatic carcinoma cell line BEL-7402 with different concentration of octreotide by flow cytometry. We discovered that, in each experimental groups, the percentage of cell in G1 phase were higher than those in their control groups. What's more, the percentage of cell in S and G2 phase were lower than those in their control groups. So, we concluded that somatostatin can inhibit cell division by decreasing the cell proportion in S and G2 stage in cell cycle.It's confirmed that it is the loss of control of apoptosis and the disequilibrium between cell proliferation and apoptosis that cause the development of tumor. Because of this, we tried to discover the mechanism of action from cell apoptosis. After we collected hepatic carcinoma cell line BEL-7402 with octreotide in different concentration, we detected the mRNA expression of bcl-2 and bax. We discovered bcl-2 and bax mRNA were expressed both in experimental groups and in control groups, more over, the expression of bax mRNA in experimental groups were higher than their control groups. On the contrary, the expression of bcl-2 mRNA in experimental groups were lower than their control groups. Thus, we concluded that somatostatin could promote apoptosis by decreasing the mRNA expression of bcl-2 and increasing the mRNA expression of bax. Further more, inhibited the cell proliferation of human hepatic carcinoma cell line BEL-7402.Above all, we make a conclusion that: The somatostatin in medium and high concentration have the depressant effect to hepatic carcinoma cell line BEL-7402, and the effect has the obvious concentration and time dependency. Somatostatin can inhibit cell proliferation by changing the cell cycle and inhibiting cell division. More over, somatostatin can promote apoptosis of human hepatic carcinoma cell line BEL-7402 by decreasing the mRNA expression of bcl-2 and increasing the mRNA expression of bax to inhibit the cell proliferation. Our experiment has provided the basic experimental theory for the clinical application of SST. In addition, the further research of SST and the development of new SSTA can provide the new idea and new way for the treatment of human malignant tumor.