The effect of somatostatin and SSTR3 on proliferation and apoptosis of gastric cancer cells.

In the present study, we detected the expression of SSTR3 protein in 40 patients with gastric adenocarcinoma and 40 cases of normal gastric mucosa by immunoperoxidased staining. SSTR3 mRNA and protein were also examined in gastric cancer cell lines and eternal gastric epithelial cell line by RT-PCR, immunofluorescence and Western blot. The effect of octreotide on the growth of gastric cancer cells was examined by MTT test, and the apoptosis by flow cytometry. Competitive protein binding method was also used to evaluate the role of SSTR3. The results were: (1) SSTR3 protein existed in the membrane of gastric cancer cells. In normal gastric mucosa, SSTR3 protein distributed to the cellular membrane and cytoplasm or interstitial tissue in submucosa. The expression of SSTR3 protein was significantly lower in gastric cancer compared with normal mucosa. Moreover, the poor-differentiated adenocarcinoma was lower than the well-differentiated adenocarcinoma, and the similar result in cell lines. (2) Octreotide could inhibit the growth and induce the apoptosis of gastric cancer and normal epithelial cells that expressed SSTR3, but didn't affect the cells with no or weakly expression of SSTR3. (3) When the cells were administrated octreotide in combination of SSTR3 antibody, the effect of octreotide decreased dramatically. The preliminary study suggested that SSTR3 might play a role in the growth and apoptosis of gastric cancer. In those gastric cancers that expressed SSTR3, octreotide could be effective in inhibiting cell growth and inducing cell apoptosis through mediation of SSTR3.