【Abstract】ObjectiveTo investigate the inhibitory effects of somatostatin analogue (SSTA) on the colonic carcinoma cell growth in vitro and in vivo and its possible mechanism. MethodsThe somatostatin receptor type Ⅱ (SSTR2) mRNA of colonic carcinoma cell line HCT116 was detected by using RTPCR and hybridization in situ. The effects of octreotide (Oct) or NC-8-12 (specific agonist of SSTR2 ) on the proliferation of HCT116 was measured with MTT after HCT116 stimulated by insulin or epidermal growth factor (EGF) and incubated with Oct or NC-8-12 simultaneously for 24 hours. The expression of cyclin D1 was detected with flow cytometry. The HCT116 were implanted in nude mice subcutaneously and treated with Oct or NC-8-12. The tumor volume and tumor weight were measured according to schedule. Results①SSTR2 mRNA was detected in HCT116 and the tumor implanted in nude mice; ②Insulin and EGF increased the proliferation of HCT116 significantly, and this proliferation could be inhibited by Oct and NC-8-12 partially; ③Insulin increased the Cyclin D1 expression of HCT116, its level decreased slightly when treated with Oct or NC-8-12 but not significantly (Pgt;0.05); ④The weight and volume of implanted tumor in nude mice treated with Oct or NC-8-12 showed no significant difference compared with the control group (Pgt;0.05). ConclusionBoth Oct and NC-8-12 could inhibit the proliferation of colonic carcinoma cell line HCT116 in vitro, which indicated that SSTR2 may mediated the inhibition. Oct and NC-8-12 have no effect on the growth of implanted HCT116 in nude mice in this experiment.
The model of transplanted colonic SW480 cell line carcinoma in gymnomouse body was set up to observe the effect of octapeptide somatostatin (SMS 201-995,SMS) on the transplanted carcinoma and elucidate its mechanism. Results: the volume, weight, DNA and protein content in carcinoma cell, cell amount and proliferation index of S and G2M phase in SMS group and SMS+PG (pentagastrin) group were markedly lower than those in PG group and control group, those of PG group were markedly higher than those in control group.The cell amount of G0/G1 phase in SMS group and SMS+PG group was markedly higher than that in PG group and control group, and that of PG group was markedly lower than that in control group.All these suggested that somatostatin could not only inhibit the growth of transplanted human colonic SW480 cell line carcinoma directly but also inhibit the growthpromoting effect of gastrin on the transplanted carcinoma.The mechanism might be that somatostatin inhibit the synthesis of cAMP, DNA and protein in carcinoma cells, then inhibit the cell growing from G0/G1 phase to S and G2M phases.Our study might provide experimental basis for the homonotherapy with analogue of somatostatin in patients with large intestine carcinoma.
Objective To detect expression of Ras association domain family 1A （RASSF1A） gene in the colonic carcinoma tissue and to analyze the relationship of this expression to its clinical features. Methods Immunohistochemistry and Western blot methods were employed for detecting the RASSF1A protein expressions in 34 colonic carcinoma tissues and corresponding normal colon tissues. RT-PCR was employed for detecting RASSF1A mRNA expression. Results ①The RASSF1A protein expression in the colonic carcinoma tissues was significantly lower than that in the normal colontissues by using immunohistochemistry〔35.3% （12/34） versus 97.1% （33/34）， P＜0.05〕.There were significant relati-onships of RASSF1A protein expressions to the tumor differentiation and TNM stage （P＜0.05）， in other words， the positive rates of RASSF1A protein in the moderately and well differentiated andⅠ＋Ⅱof TNM colonic carcinoma tissues were all higher （P＜0.05）. ② The RASSF1A protein expression in the colonic carcinoma tissues was significantly lower than that in the normal colon tissues by using Western blot 〔0.316 8±0.019 6 versus 0.914 4±0.177 6， P＜0.05〕， which was close to the result of RT-PCR〔0.158 9±0.223 7 versus 0.572 3±0.193 9， P＜0.05〕. Conclusions Absentexpre-ssion of RASSF1A gene in the colonic carcinoma tissue might play an important role in tumor genesis and tumor progre-ssion， and it might become useful early detection of the colonic carcinoma.
Objective To investigate the difference of minichromosome maintenance protein 2 (MCM2) mRNA expression among colonic normal mucosa, colonic adenoma and carcinoma. Methods The expressions of MCM2 mRNA were determined by real-time RT-PCR in 12 colonic normal mucosa, 33 colonic adenomas and 12 colonic carcinomas. Data were evaluated by relative expression software tool (REST-XL). Results The expressions of MCM2 mRNA elevated in turn by colonic normal mucosa, adenoma and carcinoma. The expression of MCM2 mRNA in colonic carcinomas was significantly higher than that in adenomas， as well as in normal mucosa (P=0.001), while the difference of MCM2 mRNA expressions between adenoma and normal mucosa was insignificant (P=0.184). Conclusion The difference of MCM2 mRNA expressions between adenoma and carcinoma indicated the potential value on early diagnosis for colonic carcinoma.