Genetic analysis identifies the HMMR gene as a modifier of the breast cancer risk associated with BRCA1 gene mutation, while cell biological analysis of the protein product suggests a function in regulating development of the mammary gland.

No abstract

The c.156_157insAlu BRCA2 mutation has so far only been reported in hereditary breast/ovarian cancer (HBOC) families of Portuguese origin. Since this mutation is not detectable using the commonly used screening methodologies and must be specifically sought, we screened for this rearrangement in a total of 5,440 suspected HBOC families from 22 labs from 13 countries from several continents. Whereas the c.156_157insAluBRCA2 mutation was detected in 11 of 149 suspected HBOC families from Portugal, representing 37.9% of all deleterious mutations, in other countries it was detected only in one proband living in France and in four individuals requesting predictive testing living in France and in the USA, all having in common the fact that they are relatively recent immigrants of Portuguese origin in those countries. After performing an extensive haplotype study in carrier families, we estimate that this founder mutation has occurred 558±215 years ago. We further demonstrate significant quantitative differences regarding the production of the BRCA2 full length RNA and the transcript with exon 3 skipping in c.156_157insAlu BRCA2 mutation carriers and in controls, indicating that disruption of alternative transcript ratios is the mechanism causing hereditary breast/ovarian cancer associated with this BRCA2 rearrangement. We further show that the cumulative incidence of breast cancer in c.156_157insAlu BRCA2 mutation carriers does not differ from that of other BRCA2 and BRCA1 pathogenic mutations, further strengthening its role as the major contributor to hereditary predisposition to breast cancer in Portugal. We recommend that all suspected HBOC families from Portugal or with Portuguese ancestry are specifically tested for this rearrangement, ideally prior to screening of the entire coding regions of BRCA1 and BRCA2.3

HRE hypomethylation in CEACAM6 promoter correlates with high expression in IEC. Our findings suggest that abnormal DNA methylation leading to CEACAM6 increased expression and AIEC-mediated gut inflammation can be related to changes in nutritional habits, such as low intake in methyl donor molecules, leading to abnormal epigenetic marks in mouse model mimicking CD susceptibility.

Breast cancer is a common disease partially caused by genetic risk factors. Germline pathogenic variants in DNA repair genes BRCA1, BRCA2, PALB2, ATM, and CHEK2 are associated with breast cancer risk. FANCM, which encodes for a DNA translocase, has been proposed as a breast cancer predisposition gene, with greater effects for the ER-negative and triple-negative breast cancer (TNBC) subtypes. We tested the three recurrent protein-truncating variants FANCM:p.Arg658*, p.Gln1701*, and p.Arg1931* for association with breast cancer risk in 67,112 cases, 53,766 controls, and 26,662 carriers of pathogenic variants of BRCA1 or BRCA2. These three variants were also studied functionally by measuring survival and chromosome fragility in FANCM−/− patient-derived immortalized fibroblasts treated with diepoxybutane or olaparib. We observed that FANCM:p.Arg658* was associated with increased risk of ER-negative disease and TNBC (OR = 2.44, P = 0.034 and OR = 3.79; P = 0.009, respectively). In a country-restricted analysis, we confirmed the associations detected for FANCM:p.Arg658* and found that also FANCM:p.Arg1931* was associated with ER-negative breast cancer risk (OR = 1.96; P = 0.006). The functional results indicated that all three variants were deleterious affecting cell survival and chromosome stability with FANCM:p.Arg658* causing more severe phenotypes. In conclusion, we confirmed that the two rare FANCM deleterious variants p.Arg658* and p.Arg1931* are risk factors for ER-negative and TNBC subtypes. Overall our data suggest that the effect of truncating variants on breast cancer risk may depend on their position in the gene. Cell sensitivity to olaparib exposure, identifies a possible therapeutic option to treat FANCM-associated tumors.