Tsongalis G J, Linfert D R, Johnson R C, Ackroyd R, Berman M M, Ricci A
Department of Pathology and Laboratory Medicine, Hartford Hospital, CT 06102, USA.
Arch Pathol Lab Med. 1998 Jun;122(6):548-50.
Germline mutations in the tumor suppressor genes BRCA1 and BRCA2 confer substantial increased lifetime risk for breast cancer, and in the case of BRCA1, for ovarian carcinoma as well. These two genes alone account for the vast majority of hereditary breast cancer families. Numerous mutations have been described in each gene, the majority of which are small insertions or deletions resulting in expression of a truncated protein.
Several common mutations can be detected using a polymerase chain reaction-mediated, site-directed mutagenesis assay, which transforms the amplicon derived from either the wild-type or mutant allele by adding or removing a restriction endonuclease site. We screened 49 putative sporadic breast tumors using this methodology, targeting four BRCA1 mutations (185delAG, 5382insC, R1443X, and E1250X) and a single BRCA2 mutation (6174delT).
Using the polymerase chain reaction-mediated, site-directed mutagenesis assay, we identified two mutations, namely, a 185delAG mutation (BRCA1) and a 6174delT mutation (BRCA2). Interestingly, these two mutations were found in the same sample. None of the remaining 48 breast tumors showed evidence of these mutations. Allele-specific oligonucleotide probes were then employed in conjunction with the Universal GeneComb Test Kit, which confirmed the presence of mutations.
Our data suggest that the common germline BRCA1 and BRCA2 mutations are infrequently encountered in sporadic breast cancers. The one case with dual BRCA1 and BRCA2 mutations suggests that this tumor may be hereditary in origin, despite the lack of a positive family history. Double heterozygosity for mutations in BRCA1 and BRCA2 may have increasingly significant implications with regard to predisposition to breast cancer.
肿瘤抑制基因BRCA1和BRCA2中的种系突变会显著增加乳腺癌的终生患病风险，就BRCA1而言，还会增加卵巢癌的患病风险。仅这两个基因就占绝大多数遗传性乳腺癌家族病例。每个基因都已发现众多突变，其中大多数是小的插入或缺失，导致截短蛋白的表达。
使用聚合酶链反应介导的定点诱变检测法可检测几种常见突变，该方法通过添加或去除一个限制性内切酶位点来改变源自野生型或突变等位基因的扩增子。我们使用这种方法筛查了49例疑似散发性乳腺肿瘤，针对四个BRCA1突变（185delAG、5382insC、R1443X和E1250X）和一个BRCA2突变（6174delT）。
使用聚合酶链反应介导的定点诱变检测法，我们鉴定出两个突变，即一个185delAG突变（BRCA1）和一个6174delT突变（BRCA2）。有趣的是，这两个突变出现在同一样本中。其余48例乳腺肿瘤均未显示这些突变的证据。然后将等位基因特异性寡核苷酸探针与通用基因组合检测试剂盒结合使用，证实了突变的存在。
我们的数据表明，散发性乳腺癌中很少遇到常见的种系BRCA1和BRCA2突变。这例同时存在BRCA1和BRCA2双重突变的病例表明，尽管缺乏阳性家族史，但该肿瘤可能起源于遗传。BRCA1和BRCA2突变的双重杂合性可能对乳腺癌易感性具有越来越重要的意义。
