Analysis of tumor suppressor genes for breast cancer

BRCA 1和BRCA 2基因的突变涉及大约60%的家族性乳腺癌，这些结果表明存在导致遗传性乳腺癌的第三个主要基因。该基因的分离对于遗传性乳腺癌的基因检测具有重要意义。利用酵母双杂交系统分离BRCA 2结合蛋白。我们发现BRCA 2与Rad 51形成复合物，并且Rad 51基因的北方印迹分析的模式与BRCA 2基因的模式非常相似。因此，Rad 51基因的改变可能参与遗传性乳腺癌的发展。为了研究这种可能性，我们筛选了日本遗传性乳腺癌患者的Rad 51突变，发现外显子6有一个单一的改变。这被确定存在于两名双侧乳腺癌患者的生殖细胞中。在这两名患者中，血液DNA显示密码子150的第二个核苷酸的G-到-A转换， ...更多信息 导致谷氨酰胺取代精氨酸。由于这种改变在乳腺癌或结肠癌患者中不存在，我们假设这种错义改变可能代表疾病相关突变。BRCA 2结合蛋白的另一个候选者，命名为BRAP 1，与据报道与乳腺癌发生相关的Amphiphysin和BIN 1高度同源。确定该基因的外显子-内含子边界，并对乳腺癌家系中的生殖系突变和原发性乳腺癌中的体细胞突变进行筛查。虽然没有发现突变的家庭和原发性癌症，BRAP 1基因的表达水平被检测到显着降低，在乳腺癌细胞系和胰腺癌细胞株，我们已经描述了一小部分的可能性，双侧乳腺癌是由于生殖细胞的Rad 51的改变。然而，第三个主要的乳腺癌易感基因仍然未知;需要付出巨大的努力来分离负责的基因。少

Mutations in the BRCA1 and BRCA2 genes are involved in approximately 60% of familial breast cancers and these results indicate the existence of the 3rd major gene responsible for hereditary breast cancers. The isolation of this gene is important for the genetic testing of hereditary breast cancer. The yeast two-hybrid system was used to isolate BRCA2-binding proteins. We showed that BRCA2 formed a complex with Rad51 and the pattern of northern blot analysis of the Rad51 genewas closely similar to that of the BRCA2 gene. It is therefore possible that alterations of the Rad51 gene may be involved in the development of hereditary breast cancers. To investigate this possibility, we screened Japanese patients with hereditary breast cancer for Rad51 mutations and found a single alteration in exon 6. This was determined to be present in the germline in two patients with bilateral breast cancer. In both patients, blood DNAs showed G-to-A transition of the second nucleotide of codon 150, which … More results in the substitution of glutamine for arginine. Since this alteration was not present in patients with breast or colon cancer examined, we assume that this missense alteration is likely to represent a disease-associated mutation. Another candidate of BRCA2-binding protein, designated BRAP1, is highly homologous to Amphiphysin and BIN1, that were reported to be associated with breast carcinogenesis. The exon-intron boundaries of this gene were determined, and screening for germline mutation in breast cancer families and for somatic mutation in primary breast cancers was performed. Although no mutation was found in families and primary cancers, the expression level of the BRAP1 gene was detected to be remarkably decreased in breast cancer cell lines and pancreas cancer cell lines.We have described the possibility that a small portion of bilateral breast cancers is due to germline alterations of Rad51. However, the 3rd major breast cancer susceptibility gene remains unknown ; intense efforts will be required to isolate the gene (s) responsible. Less