Investigating the causal role of MRE11A p.E506* in breast and ovarian cancer

The nuclease MRE11A is often included in genetic test panels for hereditary breast and ovarian cancer (HBOC) due to its BRCA1-related molecular function in the DNA repair pathway. However, whether MRE11A is a true predisposition gene for HBOC is still questionable. We determined to investigate this notion by dissecting the molecular genetics of the c.1516G > T;p.E506* truncating MRE11A variant, that we pinpointed in two unrelated French-Canadian (FC) HBOC patients. We performed a case-control study for the variant in ~ 2500 breast, ovarian, and endometrial cancer patients from the founder FC population of Quebec. Furthermore, we looked for the presence of second somatic alterations in the MRE11A gene in the tumors of the carriers. In summary, these investigations suggested that the identified variant is not associated with an increased risk of developing breast or ovarian cancer. We finally performed a systematic review for all the previously reported MRE11A variants in breast and ovarian cancer. We found that MRE11A germline variants annotated as pathogenic on ClinVar often lacked evidence for such classification, hence misleading the clinical management for affected patients. In summary, our report suggests the lack of clinical utility of MRE11A testing in HBOC, at least in the White/Caucasian populations

MRN Complex and Cancer Risk: Old Bottles, New Wine

The MRN complex, composed of MRE11A, RAD50, and NBN, mediates vital molecular functions to maintain genomic stability and hence protect against related disorders. Germline mutations in the MRN genes predispose to three different syndromes: ataxia-telangiectasia-like disorder (MRE11A deficiency), Nijmegen breakage syndrome (NBS; NBN deficiency), and NBS-like disorder (RAD50 deficiency). The potential cancer component of these syndromes in addition to the close physical and functional proximity of the MRN complex to BRCA1 has promoted the MRN genes as candidate risk genes for developing breast cancer. This notion has been challenged by independent large-scale population-based studies. Despite having their two-decade old candidacy as breast cancer genes close to being refuted, it has recently been reported that the MRN genes rise to have potential new roles in clonal hematopoiesis. In this article, we discuss the history and current status of MRN genes' clinical utility in breast cancer and then focus on their recently uncovered and less understood roles in clonal hematopoiesis that likely predispose to health-related disorders such as hematologic malignancies and/or cardiovascular morbid events