Gene Expression in Normal and Tumor Ovarian Epithelial Cells from Non-carriers and Heterozygous Carriers of a BRCA French Canadian Mutation.. Homo sapiens

We hypothesized that the transcriptome of primary cultures of morphologically normal ovarian surface epithelial cells could be altered by the presence of a heterozygous BRCA1 or BRCA2 mutation. We aimed to discover early events associated to ovarian carcinogenesis, which could represent putative targets for preventive strategies of this silent killer tumor. We identified the first molecular signature associated with French Canadian BRCA1 or BRCA2 founder mutations in morphologically normal ovarian epithelial cells. We discovered that wild-type and mutated BRCA2 allelic transcripts were expressed not only in morphologically normal but also in tumor cells from 8765delAG BRCA2 carriers. Further analysis of morphologically normal ovarian and tumor cells from C4446T BRCA1 carriers lead to the same observation. Our data support the idea that one single hit in BRCA1 or BRCA2 is sufficient to alter the transcriptome of phenotypically normal ovarian epithelial cell. The highest level of BRCA2 mutated allele transcript expression was measured in cells originating from the most aggressive ovarian tumor. The penetrance of the mutation and the aggressiveness of the related tumor could depend on a dosage effect of the mutated allele transcript. Overall design: We studied the molecular profiles associated with 5 a priori classes of samples : 4 non-familial morphologically normal ovarian surface epithelium (NOSEs) : NM class, 2 BRCA1-mutated NOSEs : M1 class, 3 BRCA2-mutated NOSEs : M2 class, 3 BRCA1-mutated ovarian tumor cells (TOVs) : TM1 class and one BRCA2-mutated TOV :TM2 class. No technical replicates were included in this study. The following contrasts were computed : NM vs. M1, NM vs. M2, M1 vs. M2, M1 vs. TM1 and M (M1 union M2) vs. TM (TM1 union TM2).

本研究提出假说：杂合性BRCA1或BRCA2突变的存在，可改变形态正常的卵巢表面上皮细胞原代培养物的转录组（transcriptome）。本研究旨在探寻与卵巢癌变（ovarian carcinogenesis）相关的早期事件，这些事件可作为这类沉默杀手肿瘤的预防策略潜在靶点。本研究在形态正常的卵巢上皮细胞中，首次鉴定出与法裔加拿大人BRCA1或BRCA2奠基者突变（founder mutation）相关的分子特征（molecular signature）。本研究发现，在携带8765delAG型BRCA2突变的个体中，野生型（wild-type）与突变型BRCA2等位基因转录本不仅在形态正常细胞中表达，也在其肿瘤细胞中表达。对携带C4446T型BRCA1突变的个体的形态正常卵巢细胞及肿瘤细胞的进一步分析，得到了一致的观测结果。本研究数据支持如下观点：BRCA1或BRCA2的单等位基因变异，即可改变表型正常的卵巢上皮细胞的转录组。在源自侵袭性最强的卵巢肿瘤的细胞中，检测到了最高水平的BRCA2突变等位基因转录本表达量。该突变的外显率（penetrance）以及相关肿瘤的侵袭性，可能取决于突变等位基因转录本的剂量效应。整体实验设计：本研究针对5类先验分类的样本开展分子谱分析：4例非家族性形态正常卵巢表面上皮细胞（NOSEs，ovarian surface epithelium）：NM组；2例携带BRCA1突变的NOSEs：M1组；3例携带BRCA2突变的NOSEs：M2组；3例携带BRCA1突变的卵巢肿瘤细胞（TOVs，ovarian tumor cells）：TM1组；以及1例携带BRCA2突变的卵巢肿瘤细胞（TOV，ovarian tumor cell）：TM2组。本研究未设置技术重复样本。本研究设置了如下差异比较组：NM vs. M1、NM vs. M2、M1 vs. M2、M1 vs. TM1，以及M（M1与M2的合集）vs. TM（TM1与TM2的合集）。