Mutations in PPM1D/Wip1 phosphatase impair the DNA damage-induced checkpoint and may predispose cells to tumorigenesis.

Background Germline mutations in the BRCA1 and BRCA2 genes have been shown to account for the majority of hereditary breast and ovarian cancers. The purpose of our study was to estimate the incidence and spectrum of pathogenic mutations in BRCA1/2 genes in high-risk Czech families.

Complete or partial inability to sense and repair DNA damage increases the risk of developing cancer. The ataxia telangiectasia mutated (ATM) protein kinase has a crucial role in response to DNA double-strand breaks. Hereditary mutations in the ATM gene are the cause of a rare genomic instability syndrome ataxia telangiectasia (AT) characterized, among others, by elevated cancer risk. Although clear in homozygotes, numerous studies have failed to find a link between heterozygotes and cancer. However, there is increasing evidence that ATM heterozygotes have an increased risk of developing breast cancer. First, epidemiological studies conferred an increased risk of breast cancer among AT relatives. Second, in vitro studies of heterozygous cells provide strong evidence of hyperradiosensitivity. Third, some clinical studies found an increased frequency of ATM mutations among high-risk breast cancer families.

Background: Several reports indicate that inherited mutations in the PALB2 gene predispose to breast cancer. However, there is little agreement about the clinical relevance and usefulness of mutation screening in this gene. We analyzed the prevalence and spectrum of germline mutations in PALB2 to estimate their contribution to hereditary breast and/or ovarian cancer in the Czech Republic.Methods: The entire PALB2 coding region was sequenced in 409 breast/ovarian cancer patients negative for BRCA1 and BRCA2 mutations. Testing for large genomic rearrangements (LGR) was performed by multiplex ligation-dependent probe amplification (MLPA) analysis.Results: We have identified 13 different pathogenic alterations including 10 truncating mutations and three LGRs in 16 of 409 patients (3.9%), whereas one truncating mutation was found in a group of 1,226 controls (0.08%; P ¼ 2.6 Â 10

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Large genomic rearrangements (LGR) represent substantial proportion of pathogenic mutations in the BRCA1 gene, whereas the frequency of rearrangements in the BRCA2 gene is low in many populations. We screened for LGRs in BRCA1 and BRCA2 genes by multiplex ligation-dependent probe amplification (MLPA) in 521 unrelated patients negative for BRCA1/2 point mutations selected from 655 Czech high-risk breast and/or ovarian cancer patients. Besides long range PCR, a chromosome 17-specific oligonucleotide-based array comparative genomic hybridization (aCGH) was used for accurate location of deletions. We identified 14 patients carrying 8 different LGRs in BRCA1 that accounted for 12.3% of all pathogenic BRCA1 mutations. No LGRs were detected in the BRCA2 gene. In a subgroup of 239 patients from high-risk families, we found 12 LGRs (5.0%), whereas two LGRs were revealed in a subgroup of 282 non-familial cancer cases (0.7%). Five LGRs (deletion of exons 1-17, 5-10, 13-19, 18-22 and 21-24) were novel; two LGRs (deletion of exons 5-14 and 21-22) belong to the already described Czech-specific mutations; one LGR (deletion of exons 1-2) was reported from several countries. The deletions of exons 1-17 and 5-14, identified each in four families, represented Czech founder mutations. The present study indicates that screening for LGRs in BRCA1 should include patients from breast or ovarian cancer families as well as high-risk patients with non-familial cancer, in particular cases with early-onset breast or ovarian cancer. On the contrary, our analyses do not support the need to screen for LGRs in the BRCA2 gene. Implementation of chromosome-specific aCGH could markedly facilitate the design of primers for amplification and sequence analysis of junction fragments, especially in deletions overlapping gene boundaries.

The CHEK2 gene mutations I157T (c.470T>C) and IVS2+1G>A affecting the forkhead-associated domain (FHA) have been shown to increase the risk of breast cancer development in several populations. We analyzed the CHEK2 gene segment coding for FHA domain in 673 unselected breast cancer patients and 683 controls from the Czech Republic using the denaturant high-performance liquid chromatography. The found frequency of predominant FHA alteration I157T did not differ between breast cancer patients (19/673; 2.82%) and controls (17/683; 2.49%; P=0.71). Besides this mutation we characterized another nine alterations-six located within FHA coding sequence and three occurring in introns 1 or 2). Eight variants occurred once each in patients with breast cancer and two were present in controls. Three alterations found in breast cancer patients were novel missense variants (Y159H, T172A, and L174F) affecting highly conservative residues in FHA domain. Despite the lack of association of I157T mutation with breast cancer development in our population we deduced that the FHA domain is the subject of rare population-specific alterations that might modify risk of various cancers.