Studies Of Tumor Suppressor Gene P33～(ING1b) In Breast Carcinoma

Background: Tumor-related gene includes oncogene proto-oncogene viral oncogene tumor suppresspr gene drug-resistance gene et al. Tumor suppressor gene negatively control cell growth, proliferation and differentiation. Loss of its functions caused by gene deletion and/or mutation contribute to cell transformation and tumor formation. INGl, a recently identified candidate tumor suppressor gene, is downregulated and is deleted and mutated in a variety of primary tumors and established cell lines. In exocrine pancreatic carcinoma, inactivation of wild-type p53 is an important molecular event in tumorigenesis. Gene net related with p53 functions plays a major role in cell progression, differentiation and sustaining normal morphologic structure. p33INGlbprotein encoded by INGl gene was closely physically related with p53 protein. p33INGlb protein may be a member of the family of p53 protein. Some of the functions of INGl, such as cell cycle arrest and apoptosis, have been shown to be dependent on the activity of both INGl and p53 proteins. To investigate the alterations and expressions of p33INGlb gene, as well as its relationship with p53, may be efficiently demonstrate the molecular mechanism of pancreatic carcinogenesis.Methods: Immunohistochemistry was applied To discuss the pathological relationship between the expression ofp33ING1b, p53 C-erbB-2 PCNA and prognosis in breast carcinoma and their exertion in clinic. 23 cases of breast carcinomas were analyzed for heterozygosity(LOH) at INGl locus, using four narrow spaced microsatellite markers. The mutation of p33INGlb gene was examined by PCR-SSCP technique and DNA sequencing in 40 cases of pancreatic carcinomas. Results:1. p33INGlb expression in breast carcinoma group and control group was positive, the expression in breast carcinoma group was extremely low (65%, 52/80), significantly different from the other group (P<0. 01) . The positive rates of p33INGlb p53 C-erbB-2 PCNA expression were found 65% 60% 61.25% 68.75% respectively. The expression of p33INGlb were positively correlation with p53 and the level of estrogen receptor (P<0. 05), and the expression of p33INGlb p53 were correlation with tumor size and lymph node metastases. The expression of C-erbB-2 PCNA were positively correlation with histological grading and lymph node metastases (P<0. 05) , and they were negatively correlation with the level of ER and PR.2. The results of PCR-SSCP and DNA sequencing demonstrated that INGlb gene did not have a fragmental frame shift or deletion in 40 cases of tumor and surrounding tumor tissues. Only one case of PC present abnormal band shifting by SSCP which had a point mutation in p33INGIbgene exon 2. In all surrounding breast tumor tissues p33INGlb gene did not exhibit mutation. p33INGlb gene had a low mutation rate in PCs, which suggested that gene mutation was not the main reason that p33INGlb lost its tumor suppressing function in breast carcinomas.3. There are loss of heterozygosity on ING1 locus of chromosome 13q33~34. Fourteen(60. 9%) of 23 tumor samples showed LOH in all of the informative markers tested, including D13S261, D13S1047, D13S1315 and DS42490. The rates of the four microsatellite markers were 8.7% 21.7% 13.0% and 26.1%, respectively. But only 2 of them show no protein expression. This suggest that genetic alterations that abrogate normal function of ING1 may contributeto breast carcinoma cell carcinogenesis, but not contribute to the loss expression of p33ING1b proteinConclusions:1. Deletions and/or mutations are not the main reason responsible for the loss of normal functions of p33INGlb. The loss of p33INGlb expression may contribute to the development of breast carcinoma.2. LOH of ING1 locus on chromosome 13q33-34 may abrogate the functions of ING1.3. Some functions of p33INGlb, such as growth arrest and apoptosis, may be interrelated with p53 and require the activities of both gene.