Expression Of Tumor Suppressor Gene P33～(ING1b) In Gastric Carcinoma

Objective oncomolecularbiology has confirmed that tumor suppressor gene was participated in the process of gastric carcinoma. Loss of its functions cause by gene deletion and mutation contribute to cell transformation and tumor formation. ING1 gene (Inhibitor of growth 1 gene), a recently identified candidate tumor suppressor gene, encode the protein P33ING1b. P33ING1b protein is involved in restriction of cell growth and proliferation, apoptosis, tumor anchorage independent growth, cellular senescence, maintenance of genomic stability, and modulation of cell cycle checkpoints. The study of p33ING1b expression in gastric carcinoma was profit to analyze its role in the process of gastric carcinoma .which would help us to interpret the mechanism of gastric carcinoma.Methods p331NG1b protein expression in 51 cases of gastric carcinoma and 20cases of normal gastric mucosa was examined by S-P immunohistochemical method, Futhermore, the relationship between the expression of p33ING1b and the clinicopathologic features was determined. We examined the expression of p33ING1b mRNA by RT-PCR in 15 cases of gastric carcinoma and the adjacent normal gastric mucosa of the gastrectomy; protein expression in the same samples was examined by western-blotting; the mutation of exon la and 2 of p33ING1b gene was examined by PCR-SSCP.Result p33ING1b protein displayed in both nuclear and cytoplasmic localization. The positive rate of P33ING1b protein expression was 100% (20/20) in normal gastric mucosa. The intensities of S-P immunostaining were scored (+) 6 cases, (++) 6 cases and (+ + +) 8 cases among the 20 cases normal gastric mucosa. But in the gastric carcinoma the positive rate of p33ING1b protein expression was41.2% (21/51). The intensities of S-P immunostaining were scored (±) 5 cases, (± ±) 9 cases, (± ± ±) 7 cases and ( -) 30cases among the 51 cases of gastric carcinoma. The positive rate of p33ING1b protein expression was decreased in gastric carcinoma than normal gastric mucosa(P<0.05).The positive rate of P33ING1b protein expression was 65% (13/20) in well differentiated, moderately differentiated 38.9% (7/18) and poorly differentiated 7.7% (1/13) . The positive rate of P33ING1b protein expression in poorly differentiated cases was significantly lower than that in well differentiated and moderately differentiated cases(P<0.05); The loss expression of p33ING1b protein was related to differentiation of gastric carcinoma.The results of RT-PCR showed that the expression rate of p33ING1b mRNA was different between gastric carcinoma (8/15, 53.3%) and the adjacent normal gastric mucosa(15/15,100%); the average level of p33ING1b mRNA expression was 0.377±0.184 in gastric carcinoma and 1. 048 ±0. 081 in the adjacent normal gastric mucosa. It was down-regulated in gastric carcinoma compares with the adjacent normal gastric mucosa(P<0.05).The results of Western-blotting showed that the expression rate of P33ING1b protein was the same as the result of RT-PCR; the average level of p33ING1b protein expression was 0.338±0.199 in gastric carcinoma and 0. 998 ± 0. 245 in the adjacent normal gastric mucosa. Western-blotting analysis revealed that the p33ING1b protein expression in normal gastric mucosa was significantly stronger than that in matched gastric carcinoma(P<0.05).There was no mutation of p33ING1b gene in exon la and exon 2 in the 15 cases gastric carcinomas.Gonclusions① The positive rate of p33ING1b protein expression was decreased in gastriccarcinoma than normal gastric mucosa.② The loss expression of P33ING1b protein was related to differentiation of gastric...