675

BRCA2

BRCC2|BROVCA2|FACD|FAD|FAD1|FANCB|FANCD|FANCD1|GLM3|PNCA2;breast cancer 2, early onset;BRCA2;breast cancer 2, early onset

BRCA1/BRCA2-containing complex, subunit 2|breast and ovarian cancer susceptibility gene, early onset|breast cancer 2 tumor suppressor|breast cancer susceptibility protein BRCA2|breast cancer type 2 susceptibility protein|fanconi anemia group D1 protein

13q12.3

protein-coding

Fanconi anemia is an inherited disease characterized by bone marrow failure, congenital malformations, and predisposition to cancer. The breast cancer susceptibility gene BRCA2 was recently found to be associated with Fanconi anemia complementation group D1 (FA-D1). We examined four kindreds afflicted with Fanconi anemia for the presence of germline BRCA2 mutations. One kindred, of Ashkenazi Jewish ancestry, had five members who were diagnosed with breast cancer and two cousins who were BRCA2*6174delT/C3069X compound heterozygotes and had Fanconi anemia and brain tumors. In another kindred of Ashkenazi Jewish and Lithuanian Catholic ancestry, a child with Fanconi anemia and a medulloblastoma was a BRCA2*6174delT/886delGT compound heterozygote. Two other kindreds each contained a Fanconi anemia-afflicted child who developed medulloblastoma; one child was of Latin American ancestry and a compound heterozygote for BRCA2*I2490T/ 5301insA and the other was African American and a compound heterozygote for BRCA2*Q3066X/E1308X. Median age of the Fanconi anemia-afflictedchildren at brain tumor diagnosis was 3.5 years. The co-occurrence of brain tumors, Fanconi anemia, and breast cancer observed in one of these kindreds constitutes a new syndromic association. Individuals who carry a germline BRCA2 mutation and who plan to have children with a partner of Ashkenazi Jewish descent should consider undergoing genetic counseling.

Fanconi anemia is an inherited disease characterized by bone marrow failure, congenital malformations, and predisposition to cancer. The breast cancer susceptibility gene BRCA2 was recently found to be associated with Fanconi anemia complementation group D1 (FA-D1). We examined four kindreds afflicted with Fanconi anemia for the presence of germline BRCA2 mutations. One kindred, of Ashkenazi Jewish ancestry, had five members who were diagnosed with breast cancer and two cousins who were BRCA2*6174delT/C3069X compound heterozygotes and had Fanconi anemia and brain tumors. In another kindred of Ashkenazi Jewish and Lithuanian Catholic ancestry, a child with Fanconi anemia and a medulloblastoma was a BRCA2*6174delT/886delGT compound heterozygote. Two other kindreds each contained a Fanconi anemia-afflicted child who developed medulloblastoma; one child was of Latin American ancestry and a compound heterozygote for BRCA2*I2490T/ 5301insA and the other was African American and a compound heterozygote for BRCA2*Q3066X/E1308X. Median age of the Fanconi anemia-afflictedchildren at brain tumor diagnosis was 3.5 years. The co-occurrence of brain tumors, Fanconi anemia, and breast cancer observed in one of these kindreds constitutes a new syndromic association. Individuals who carry a germline BRCA2 mutation and who plan to have children with a partner of Ashkenazi Jewish descent should consider undergoing genetic counseling.

Fanconi anemia (FA) and Bloom syndrome (BS) are rare autosomal recessive geneticdisorders manifesting in childhood, with a predisposition to cancer development in adolescence and adulthood. Both syndromes are relatively prevalent among the Ashkenazi Jewish population, and, in both syndromes, mutations specific to this population have been identified. Similarly, unique Ashkenazi mutations were found in the genes BRCA1 and BRCA2. These two genes, when mutated, play important roles in familial breast and ovarian carcinogenesis. The genes involved in the pathogenesis of the FA and BS belong to the general class of instability genes. Heterozygosity for the FA gene has no known promalignant potential, while the BSmutation carrier state was associated with an increased frequency of colorectal cancer. The especially frequent carrier state among the Ashkenazi Jewish population coupled with the high prevalence of BRCA1 and BRCA2 in the same population has led us to search for coinheritance affecting the potential for cancer development. One hundred Ashkenazi women with known BRCA1 and BRCA2 mutations were screened for the FA mutation IVS4+4 A-->T and the BS mutation blm(Ash). Our results indicate that there is an increased prevalence of both FA and BS mutation carriers among the population studied compared with the general Ashkenazi population (prevalence of FA mutation 4/100 women [4%] as compared to 35/3104 previously published controls [1.1%], P=0.031, and for BS mutation 3/100[3.2%] as compared to 36/4001 [0.9%], P=0.058). There was no statistically significant effect of the coinheritance on cancer prevalence, type of cancer, orage of cancer onset. Coinheritance of FA and/or BS mutations seems to be more prevalent among BRCA mutation carriers, but a larger study encompassing more women may help in clarifying this issue.

Fanconi anemia (FA) and Bloom syndrome (BS) are rare autosomal recessive geneticdisorders manifesting in childhood, with a predisposition to cancer development in adolescence and adulthood. Both syndromes are relatively prevalent among the Ashkenazi Jewish population, and, in both syndromes, mutations specific to this population have been identified. Similarly, unique Ashkenazi mutations were found in the genes BRCA1 and BRCA2. These two genes, when mutated, play important roles in familial breast and ovarian carcinogenesis. The genes involved in the pathogenesis of the FA and BS belong to the general class of instability genes. Heterozygosity for the FA gene has no known promalignant potential, while the BSmutation carrier state was associated with an increased frequency of colorectal cancer. The especially frequent carrier state among the Ashkenazi Jewish population coupled with the high prevalence of BRCA1 and BRCA2 in the same population has led us to search for coinheritance affecting the potential for cancer development. One hundred Ashkenazi women with known BRCA1 and BRCA2 mutations were screened for the FA mutation IVS4+4 A-->T and the BS mutation blm(Ash). Our results indicate that there is an increased prevalence of both FA and BS mutation carriers among the population studied compared with the general Ashkenazi population (prevalence of FA mutation 4/100 women [4%] as compared to 35/3104 previously published controls [1.1%], P=0.031, and for BS mutation 3/100[3.2%] as compared to 36/4001 [0.9%], P=0.058). There was no statistically significant effect of the coinheritance on cancer prevalence, type of cancer, orage of cancer onset. Coinheritance of FA and/or BS mutations seems to be more prevalent among BRCA mutation carriers, but a larger study encompassing more women may help in clarifying this issue.

Missense mutations of the V600E type constitute the vast majority of tumor-associated somatic alterations in the v-RAF murine sarcoma viral oncogene homolog B1 (BRAF) gene. Initially described in melanoma, colon and papillary thyroid carcinoma, these alterations have also been observed in primary nervous system tumors albeit at a low frequency. We analyzed exon 15 of BRAF spanning the V600 locus by direct sequencing in 1,320 adult and pediatric tumors of the nervous system including various types of glial, embryonal, neuronal and glioneuronal, meningeal, adenohypophyseal/sellar, and peripheral nervous system tumors. A total of 96 BRAF mutations were detected; 93 of the V600E type and 3 cases with a three base pair insertion between codons 599 and 600. The highest frequencies of BRAF (V600E) mutations were found in WHO grade II pleomorphic xanthoastrocytomas (42/64; 66%) and pleomorphic xanthoastrocytomas with anaplasia (15/23; 65%), as well as WHO grade I gangliogliomas (14/77; 18%), WHO grade III anaplastic gangliogliomas (3/6) and pilocytic astrocytomas (9/97; 9%). In pilocytic astrocytomas BRAF (V600E) mutation was strongly associated with extra-cerebellar location (p = 0.009) and was most frequent in diencephalic tumors (4/12; 33%). Glioblastomas and other gliomas were characterized by a low frequency or absence of mutations. No mutations were detected in non-glial tumors, including embryonal tumors, meningiomas, nerve sheath tumors and pituitary adenomas. The high mutation frequencies in pleomorphic xanthoastrocytomas, gangliogliomas and extra-cerebellar pilocytic astrocytomas implicate BRAF (V600E) mutation as a valuable diagnostic marker for these rare tumor entities. Future clinical trials should address whether BRAF (V600E) mutant brain tumor patients will benefit from BRAF (V600E)-directed targeted therapies.

The fact that BRCA genes operate as tumor suppressors is evident from the genetics of the different human disorders caused by inherited mutations. Germline mutations affecting 1 allele of either BRCA1 or BRCA2 confer susceptibility to different types of cancers such as breast cancer and medulloblastoma. A family with a history of cancer was identified in Eastern Turkey in which one of the family members (a 13-year-old boy) had medulloblastoma. Venous blood was collected from available family members. The BRCA1 and BRCA2 genes were sequenced in the patient with medulloblastoma and the healthy father. An Asn372His homozygous variation was noted in the BRCA2 gene in the patient with medulloblastoma whereas the variation was heterozygous in the healthy father. A biallelic homozygous variation was demonstrated in the BRCA2 gene, which is important in medulloblastoma suppression, and may have caused medulloblastoma formation in the 13-year-old boy. Further investigations in large human populations with medulloblastoma are necessary for further delineation of BRCA gene malfunctions and their relationship to medulloblastoma formation, and to clarify the therapeutic implications of these malfunctions.