Two different BRCA2 mutations found in a multigenerational family with a history of breast, prostate, and lung cancers
Diane A Caporale, Erica E Swenson
Department of Biology, University of Wisconsin – Stevens Point, Stevens Point, WI, USA
Abstract: Breast and lung cancer are two of the most common malignancies in the United States, causing approximately 40,000 and 160,000 deaths each year, respectively. Over 80% of hereditary breast cancer cases are due to mutations in two breast cancer predisposition genes, BRCA1 and BRCA2. These are tumor-suppressor genes associated with DNA repair. Since the discovery of these two genes in the mid-1990s, several other breast cancer predisposition genes have been identified, such as the CHEK2 gene encoding a regulator of BRCA1. Recently, studies have begun investigating the roles of BRCA1 and BRCA2 gene expression in lung cancer. We conducted a family-based case study that included a bloodline of Italian heritage with several cases of breast cancer and associated cancers (prostate and stomach) through multiple generations and on a nonblood relative of Scottish/Irish descent who was consecutively diagnosed with breast and lung cancer. Cancer history and environmental risk factors were recorded for each family member. To investigate possible genetic risks, we screened for mutations in specific hypervariable regions of the BRCA1, BRCA2, and CHEK2 genes. DNA was extracted and isolated from the individuals' hair follicles and cheek cells. Polymerase chain reaction (PCR), allele-specific PCR, and DNA sequencing were performed to identify and verify the presence or absence of mutations in these regions. Genotypes of several family members were determined and carriers of mutations were identified. Here we report for the first time the occurrence of two different BRCA2 frameshift mutations within the same family. Specifically, three Italian family members were found to be carriers of the BRCA2-c.2808_2811delACAA (3036delACAA) mutation, a 4-nucleotide deletion in exon 11, which is a truncated mutation that causes deleterious function of BRCA2. This mutation that has been reported in many women of Spanish descent is within a hotspot and is predicted to have resulted from three separate mutational events. Although sporadic mutations can occur, more than likely it is the result of a germ line mutation inherited from the Italian family line and was carried by a father that died of prostate cancer. Since individual III-2 had an early onset of breast cancer, it is recommended that siblings of II-1 seek genetic counseling and be screened for the BRCA2-3036delACAA variant. The individual with breast and lung cancer (II-8) was not a carrier of this mutation, but rather a carrier of the BRCA2-c.6275_6276delTT (6503delTT), which is also a truncated mutation but more common in those of Irish/Scottish descent. It is recommended that her immediate family members be screened for this mutation to assess their risk of breast cancer. We conclude that DNA screening of the BRCA2 promoter region and the BRCA2-6503delTT site from a lung tumor biopsy taken from individual II-8 would provide more insight into the possible association of this BRCA2 variant with lung cancer.
Keywords: breast/prostate/lung cancers, BRCA2 deletions, AS PCR, genogram
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