Transcription profiling by array of human HeLa cells with M1775R and A1789T BRCA1 missense mutations

BRCA1 (breast cancer 1, early onset) mutations confer a high breast and ovarian cancer risk. Most of BRCA1 cancer-predisposing mutations originate truncated proteins, but missense mutations have also been detected in familial breast and ovarian cancer patients. These variants are rare and their role in cancer predisposition is often difficult to ascertain. Our purpose in the present work was to study the molecular mechanisms affected in human cells by two BRCA1 missense variants both located in the second BRCA1 BRCT domain, M1775R and A1789T. These variants were isolated from familial breast cancer patients and their role in the pathogenesis of breast cancer was also investigated by a study previously performed by our group in yeast cells. Here we present a microarray study to compare the expression profiles of HeLa cells transfected with these two variants and HeLa cells transfected with BRCA1 wild type. Data analysis was performed by evaluating three comparisons: M1775R versus wild-type (M1775RvsWT-contrast), A1789T versus wild-type (A1789TvsWT-contrast) and the mutated BRCT domain versus wild-type (MutvsWT-contrast), obtained by considering the two variants as a unique BRCT mutation. We found 173 differentially expressed genes in MutvsWT-contrast, 201 in M1775RvsWT-contrast and 313 in A1789TvsWT-contrast. Our results showed that the considered BRCA1 variants had an impact on cell processes often deregulated in cancerogenesis, such as cell cycle progression and DNA damage response and repair. Thus, our study further supports the putative role in the pathogenesis of cancer of the M1775R and A1789T BRCA1 variants from a molecular point of view.

BRCA1（乳腺癌1号基因，早期发病型）突变可显著升高乳腺癌与卵巢癌的发病风险。多数BRCA1癌症易感突变会编码截短蛋白，但家族性乳腺癌和卵巢癌患者体内也可检测到错义突变。这类变异较为罕见，其在癌症易感性中的作用往往难以明确。本研究旨在探究两种位于BRCA1第二个BRCT结构域（BRCT domain）的错义变异——M1775R与A1789T——对人细胞分子机制的影响。上述两种变异均分离自家族性乳腺癌患者，本团队此前已在酵母细胞中开展相关研究，以解析其在乳腺癌发病机制中的作用。本研究通过微阵列实验，比较转染这两种变异的海拉细胞（HeLa）与转染野生型（wild-type）BRCA1的海拉细胞的基因表达谱。数据分析围绕三组对照展开：M1775R vs 野生型（M1775RvsWT-对照）、A1789T vs 野生型（A1789TvsWT-对照），以及将两种变异视为单一BRCT突变的突变型BRCT结构域 vs 野生型（MutvsWT-对照）。结果显示，MutvsWT-对照分组中共鉴定出173个差异表达基因，M1775RvsWT-对照分组中为201个，A1789TvsWT-对照分组中则达313个。本研究结果表明，所分析的BRCA1变异会影响癌症发生过程中常出现失调的细胞通路，包括细胞周期进程、DNA损伤应答与修复。综上，本研究从分子层面进一步支持了M1775R与A1789T这两种BRCA1变异可能参与癌症发病过程的推定观点。