RESUMO
BRCA1/2 mutations in Latin America are scarcely documented and in serious need of knowledge about the spectrum of BRCA pathogenic variants, information which may alter clinical practice and subsequently improve patient outcome. In addition, the search for data on testing policies in different regions constitutes a fundamental strength for the present study, which analyzes BRCA1/2 gene sequences and large rearrangements in 940 probands with familial and/or personal history of breast/ovary cancer (BOC). In non-mutated DNA samples, Multiplex Ligation-dependent Probe Amplification assays (MLPA) were used for the analysis of large rearrangements. Our studies detected 179 deleterious mutations out of 940 (19.04%) probands, including 5 large rearrangements and 22 novel mutations. The recurrent mutations accounted for 15.08% of the total and only 2.87% of the probands analyzed, very different from a Hispanic panel previously described. IN CONCLUSION: a) this first comprehensive description of the spectrum in BRCA1/2 sheds light on the low frequency of recurrent mutations; b) this information is key in clinical practice to select adequate sequencing studies in our population, subsequently improve patient outcome and prevent damage associated to false normal reports resulting from the use of invalid population panels; c) panels of mutations from other populations should be cautiously validated before imported, even those of apparently similar origin, a concept to be considered beyond significance in Argentina.
RESUMO
BACKGROUND: The spectrum of BRCA1/2 genetic variation in breast-ovarian cancer patients has been scarcely investigated outside Europe and North America, with few reports for South America, where Amerindian founder effects and recent multiracial immigration are predicted to result in high genetic diversity. We describe here the results of BRCA1/BRCA2 germline analysis in an Argentinean series of breast/ovarian cancer patients selected for young age at diagnosis or breast/ovarian cancer family history. METHODS: The study series (134 patients) included 37 cases diagnosed within 40 years of age and no family history (any ethnicity, fully-sequenced), and 97 cases with at least 2 affected relatives (any age), of which 57 were non-Ashkenazi (fully-sequenced) and 40 Ashkenazi (tested only for the founder mutations c.66_67delAG and c.5263insC in BRCA1 and c.5946delT in BRCA2). DISCUSSION: We found 24 deleterious mutations (BRCA1:16; BRCA2: 8) in 38/134 (28.3%) patients, of which 6/37 (16.2%) within the young age group, 15/57 (26.3%) within the non-Ahkenazi positive for family history; and 17/40 (42.5%) within the Ashkenazi. Seven pathogenetic mutations were novel, five in BRCA1: c.1502_1505delAATT, c.2626_2627delAA c.2686delA, c.2728 C > T, c.3758_3759delCT, two in BRCA2: c.7105insA, c.793 + 1delG. We also detected 72 variants of which 54 previously reported and 17 novel, 33 detected in an individual patient. Four missense variants of unknown clinical significance, identified in 5 patients, are predicted to affect protein function. While global and European variants contributed near 45% of the detected BRCA1/2 variation, the significant fraction of new variants (25/96, 26%) suggests the presence of a South American genetic component. This study, the first conducted in Argentinean patients, highlights a significant impact of novel BRCA1/2 mutations and genetic variants, which may be regarded as putatively South American, and confirms the important role of founder BRCA1 and BRCA2 mutations in Argentinean Ashkenazi Jews.
RESUMO
Juvenile breast cancer is rare and poorly known. We studied a series of five breast cancer patients diagnosed within 25 years of age that included two adolescents, 12- and 15-years-old, and 3 young women, 21-, 21-, and 25-years-old, respectively. All cases were scanned for germline mutations along the entire BRCA1/2 coding sequences and TP53 exons 4-10, using protein truncation test, denaturing high performance liquid chromatography and direct sequencing. Paraffin-embedded primary tumors (available for 4/5 cases), and a distant metastasis (from the 15-years-old) were characterized for histological and molecular tumor subtype, human papilloma virus (HPV) types 16/18 E6 sequences and tumor-associated mutations in TP53 exons 5-8. A BRCA2 germline mutation (p.Ile2490Thr), previously reported in breast cancer and, as compound heterozygote, in Fanconi anemia, was identified in the 21-year-old patient diagnosed after pregnancy, negative for cancer family history. The tumor was not available for study. Only germline polymorphisms in BRCA1/2 and/or TP53 were detected in the other cases. The tumors of the 15- and 12-years-old were, respectively, classified as glycogen-rich carcinoma with triple negative subtype and as secretory carcinoma with basal subtype. The tumors of the 25-year-old and of the other 21-year-old were, respectively, diagnosed as infiltrating ductal carcinoma with luminal A subtype and as lobular carcinoma with luminal B subtype. No somatic TP53 mutations were found, but tumor-associated HPV 16 E6 sequences were retrieved from the 12- and 25-year-old, while both HPV 16 and HPV 18 E6 sequences were found in the tumor of the 15-year-old and in its associated metastasis. Blood from the 15- and 25-year-old, diagnosed with high-stage disease, resulted positive for HPV 16 E6. All the HPV-positive cases were homozygous for arginine at TP53 codon 72, a genotype associated with HPV-related cancer risk, and the tumors showed p16(INK4A) immunostaining, a marker of HPV-associated cancers. Notably menarche at 11 years was reported for the two adolescents, while the 25-year-old was diagnosed after pregnancy and breast-feeding. Our data suggest that high-risk HPV infection is involved in a subset of histopathologically heterogeneous juvenile breast carcinomas associated with menarche or pregnancy and breast-feeding. Furthermore we implicate BRCA2 in a juvenile breast carcinoma diagnosed at 21 years of age, 4 years after an early full-term pregnancy, in absence of cancer family history.
