人胃癌IFN-γ-STAT1通路的作用及其机制

The antagonistic effect between STAT1 and Survivin and its clinical significance in gastric cancer

In previous studies, we observed that STAT1 and Survivin correlated negatively with gastric cancer tissues, and that the functions of the IFN-γ-STAT1 pathway and Survivin in gastric cancer are the same as those reported for other types of cancer. In this study, the SGC7901 gastric cancer cell line and 83 gastric cancer specimens were used to confirm the relationship between STAT1 and Survivin, as well as the clinical significance of this relationship in gastric cancer. IFN-γ and STAT1 and Survivin antisense oligonucleotides (ASONs) were used to knock down the expression in SGC7901 cells. The protein expression of STAT1 and Survivin was tested by immunocytochemical and image analysis methods. A gastric cancer tissue microarray was prepared and tested by immunohistochemical methods. Data were analyzed by the Spearman's rank correlation analysis, the χ(2) test and Cox's multivariate regression analysis. Upon knockdown of IFN-γ, STAT1 and Survivin expression by ASON in the SGC7901 cell line, an antagonistic effect was observed between STAT1 and Survivin. In gastric cancer tissues, STAT1 showed a negative correlation with depth of invasion (p<0.05) in gastric cancer tissues exhibiting a negative Survivin protein expression. Furthermore, in tissues exhibiting a negative STAT1 protein expression, Survivin correlated negatively with N stage (p<0.05). Pathological and molecular markers were used to conduct Cox's multivariate regression analysis, and depth of invasion and N stage were found to be prognostic factors (p<0.05). On the other hand, in tissues exhibiting a negative Survivin protein expression, Cox's multivariate regression analysis revealed that the differentiation type and STAT1 protein expression were prognostic factors (p<0.05). There is an antagonistic effect between STAT1 and Survivin in gastric cancer, and this antagonistic effect is of clinical significance in gastric cancer.

IFN-γ regulates P53 expression in gastric cancer through a STAT1-independent pathway

AIM: To explore the relationship between STAT1 and p53 mRNA expression in human gastric cancer cell line SGC7901 and to characterize the regulatory effect of interferon-γ (IFN-γ) on p53 expression in gastric cancer.

METHODS: After SGC7901 cells were treated with IFN-γ and antisense oligonucleotides (ASON) targeting the STAT1 gene, alone or in combination, the mRNA expression of p53 and STAT1 was tested by RT-PCR, and cell apoptosis was examined by Hoechst 33258 staining. The protein expression of p53 and STAT1 in human gastric cancer tissue was examined by immunohistochemistry. Average optical density was compared between different groups using Student's t test analysis. The relationship between the expression of STAT1 and P53 protein in human gastric cancer was evaluated using Spearman rank correlation analysis.

RESULTS: Treatment with IFN-γ up-regulated the mRNA expression of STAT1 and p53 in SGC7901 cells (both P < 0.05). Treatment with STAT1-specific ASON induced down-regulation of STAT1 mRNA expression (P < 0.05) in a concentration-dependent manner. The expression of p53 mRNA was lower in all ASON groups than in the control group (all P > 0.05). Simultaneous treatment with IFN-γ and STAT1-specific ASON induced lower STAT1 mRNA expression than treatment with IFN-γ alone (P < 0.05). The mRNA expression of p53 was higher in all cells treated simultaneously with IFN-γ and STAT1-specific ASON than in those treated with IFN-γ alone (all P > 0.05). There was no correlation between STAT1 and p53 mRNA and protein expression in human gastric cancer tissue and cell lines. Treatment with either IFN-γ or STAT1-specific ASON had no significant impact on cell apoptosis.

CONCLUSION: IFN-γ could regulate p53 expression in gastric cancer through a STAT1-independent pathway.

Regulatory effect of IFN-γ on the survivin signaling pathway in gastric adenocarcinoma

AIM: To characterize the role of survivin in the pathogenesis of gastric adenocarcinoma and to investigate the regulatory effect of interferon-γ (IFN-γ) on the survivin signaling pathway in gastric adenocarcinoma.

METHODS: Protein expression was examined by immunohistochemistry. After IFN-γ and antisense oligonucleotide against survivin were used to treat SGC7901 cells, mRNA and protein expression was tested by RT-PCR and immunocytochemistry, respectively, and apoptosis was determined by Hoechst 33258 staining. Statistical analysis was performed using the Spearman's rank correlation test and student's t-test.

RESULTS: There was a positive correlation between caspase-7 and survivin expression (P = 0.03) as well as between caspase-7 and p21^waf (P = 0.02) expression in gastric adenocarcinoma. Treatment with survivin antisense oligonucleotide down-regulated the protein expression of survivin (P < 0.05) but had no significant impact on caspase-7 and p21^waf protein expression (both P > 0.05). IFN-γ treatment down-regulated the mRNA expression of survivin (P < 0.05) but up-regulated the mRNA expression of caspase-7 and p21^waf (both P < 0.05). Treatment with either IFN-γ or survivin antisense oligonucleotide had no significant impact on cell apoptosis.

CONCLUSION: Although the expression of survivin is correlated with that of caspase-7 and p21^waf, survivin can not regulate apoptosis in gastric adenocarcinoma by regulating caspase-7 and p21^waf expression. IFN-γ can regulate apoptosis in gastric adenocarcinoma by down-regulating survivin expression and up-regulating caspase-7 and p21^waf expression.