Sahnane Nora, Carnevali Ileana, Formenti Giorgio, Casarin Jvan, Facchi Sofia, Bombelli Raffaella, Di Lauro Eleonora, Memoli Domenico, Salvati Annamaria, Rizzo Francesca, Sessa Fausto, Tibiletti Maria Grazia
SC Anatomia Patologica, Ospedale di Circolo, ASST Settelaghi, 21100 Varese, Italy.
Centro di Ricerca dei Tumori Eredo-Familiari, Dipartimento di Medicina e Chirurgia, University of Insubria, 21100 Varese, Italy.
Int J Mol Sci. 2020 Dec 19;21(24):9708. doi: 10.3390/ijms21249708.
Homologous Recombination Deficiency (HRD) is a frequent feature of high-grade epithelial ovarian carcinoma (EOC), associated with sensitivity to PARP-inhibitors (PARPi). The best characterized causes of HRD in EOCs are germline or somatic mutations in and genes. Although promoter methylation is a well-known mechanism of gene transcriptional repression, few data have been published about gene methylation in EOCs. In this retrospective study, we quantitatively analyzed by pyrosequencing a selected series of 90 formalin-fixed (FFPE) primary EOCs without germline mutations. We identified 20/88 (22.7%) EOCs showing promoter methylation, including 17/88 (19.3%) in and 4/86 (4.6%) in promoters, one of which showing concomitant methylation. Mean methylation levels were 49.6% and 45.8% for and respectively, with methylation levels ≥50% in 10/20 methylated EOCs. Constitutive methylation was excluded by testing blood-derived DNA. In conclusion, pyrosequencing methylation analysis of genes is a robust, quantitative and sensitive assay applicable to FFPE samples. Remarkably, a considerable subset of germline -negative EOCs showed somatic methylation and, likely, HRD. A subpopulation of women with methylation, even without mutations, could potentially benefit from PARP-inhibitors; further clinical studies are needed to clarify the predictive role of somatic methylation of PARP-therapy response.
同源重组缺陷（HRD）是高级别上皮性卵巢癌（EOC）的常见特征，与对聚（ADP-核糖）聚合酶抑制剂（PARPi）敏感相关。EOC中HRD最明确的原因是BRCA1和BRCA2基因的种系或体细胞突变。虽然启动子甲基化是一种众所周知的基因转录抑制机制，但关于EOC中BRCA1基因甲基化的报道较少。在这项回顾性研究中，我们通过焦磷酸测序对90例无BRCA1种系突变的福尔马林固定（FFPE）原发性EOC进行了定量分析。我们鉴定出20/88（22.7%）的EOC显示BRCAI启动子甲基化，包括17/88（19.3%）的BRCAI启动子甲基化和4/86（4.6%）的BRCA2启动子甲基化，其中1例显示同时存在BRCA2甲基化。BRCAI和BRCA2的平均甲基化水平分别为49.6%和45.8%，在20例甲基化EOC中有10例甲基化水平≥50%。通过检测血液来源的DNA排除了组成性BRCAI甲基化。总之，BRCA基因的焦磷酸测序甲基化分析是一种适用于FFPE样本的可靠、定量且灵敏的检测方法。值得注意的是，相当一部分种系BRCA1阴性的EOC显示体细胞甲基化，可能存在HRD。即使没有BRCA1突变，一部分BRCA1甲基化的女性也可能从PARPi中获益；需要进一步的临床研究来阐明体细胞BRCA1甲基化对PARP治疗反应的预测作用。
