Tomasz Byrski

CHEK2 Is a Multiorgan Cancer Susceptibility Gene

A single founder allele of the CHEK2 gene has been associated with predisposition to breast and prostate cancer in North America and Europe. The CHEK2 protein participates in the DNA damage response in many cell types and is therefore a good candidate for a multisite cancer susceptibility gene. Three founder alleles are present in Poland. Two of these result in a truncated CHEK2 protein, and the other is a missense substitution of an isoleucine for a threonine. We ascertained the prevalence of each of these alleles in 4,008 cancer cases and 4,000 controls, all from Poland. The majority of the common cancer sites were represented. Positive associations with protein-truncating alleles were seen for cancers of the thyroid (odds ratio [OR] 4.9; P=.0006), breast (OR 2.2; P=.02), and prostate (OR 2.2; P=.04). The missense variant I157T was associated with an increased risk of breast cancer (OR 1.4; P=.02), colon cancer (OR 2.0; P=.001), kidney cancer (OR 2.1; P=.0006), prostate cancer (OR 1.7; P=.002), and thyroid cancer (OR 1.9; P=.04). The range of cancers associated with mutations of the CHEK2 gene may be much greater than previously thought.

Response to neoadjuvant therapy with cisplatin in BRCA1-positive breast cancer patients

Background Ten patients with breast cancer and a breast cancer susceptibility gene 1 (BRCA1) mutation, who presented with stages I to III breast cancer between December 2006 and 2007, were treated with four cycles of neoadjuvant cisplatin, followed by mastectomy and conventional chemotherapy. Methods The excised breast tissue and lymph nodes were examined for the presence of residual disease. Results Pathologic complete response was observed in nine patients (90%). Conclusions Platinum-based chemotherapy appears to be effective in a high proportion of patients with BRCA1-associated breast cancers. Clinical trials are now warranted to determine the optimum treatment for this subgroup of breast cancer patients.

Founder mutations in the BRCA1 gene in Polish families with breast-ovarian cancer.

We have undertaken a hospital-based study, to identify possible BRCA1 and BRCA2 founder mutations in the Polish population. The study group consisted of 66 Polish families with cancer who have at least three related females affected with breast or ovarian cancer and who had cancer diagnosed, in at least one of the three affected females, at age <50 years. A total of 26 families had both breast and ovarian cancers, 4 families had ovarian cancers only, and 36 families had breast cancers only. Genomic DNA was prepared from the peripheral blood leukocytes of at least one affected woman from each family. The entire coding region of BRCA1 and BRCA2 was screened for the presence of germline mutations, by use of SSCP followed by direct sequencing of observed variants. Mutations were found in 35 (53%) of the 66 families studied. All but one of the mutations were detected within the BRCA1 gene. BRCA1 abnormalities were identified in all four families with ovarian cancer only, in 67% of 27 families with both breast and ovarian cancer, and in 34% of 35 families with breast cancer only. The single family with a BRCA2 mutation had the breast-ovarian cancer syndrome. Seven distinct mutations were identified; five of these occurred in two or more families. In total, recurrent mutations were found in 33 (94%) of the 35 families with detected mutations. Three BRCA1 abnormalities-5382insC, C61G, and 4153delA-accounted for 51%, 20%, and 11% of the identified mutations, respectively.

A high proportion of founder BRCA1 mutations in Polish breast cancer families

Three mutations in BRCA1 (5382insC, C61G and 4153delA) are common in Poland and account for the majority of mutations identified to date in Polish breast and breast–ovarian cancer families. It is not known, however, to what extent these 3 founder mutations account for all of the BRCA mutations distributed throughout the country. This question has important implications for health policy and the design of epidemiologic studies. To establish the relative contributions of founder and nonfounder BRCA mutations, we established the entire spectrum of BRCA1 and BRCA2 mutations in a large set of breast–ovarian cancer families with origins in all regions of Poland. We sequenced the entire coding regions of the BRCA1 and BRCA2 genes in 100 Polish families with 3 or more cases of breast cancer and in 100 families with cases of both breast and ovarian cancer. A mutation in BRCA1 or BRCA2 was detected in 66% of breast cancer families and in 63% of breast–ovarian cancer families. Of 129 mutations, 122 (94.6%) were in BRCA1 and 7 (5.4%) were in BRCA2. Of the 122 families with BRCA1 mutations, 119 (97.5%) had a recurrent mutation (i.e., one that was seen in at least 2 families). In particular, 111 families (91.0%) carried one of the 3 common founder mutations. The mutation spectrum was not different between families with and without ovarian cancer. These findings suggest that a rapid and inexpensive assay directed at identifying the 3 common founder mutations will have a sensitivity of 86% compared to a much more costly and labor‐intensive full‐sequence analysis of both genes. This rapid test will facilitate large‐scale national epidemiologic and clinical studies of hereditary breast cancer, potentially including studies of chemoprevention.

Breast cancer predisposing alleles in Poland

SummaryMutant alleles of several genes in the DNA repair pathway have been found to predispose women to breast cancer. From a public health perspective, the importance of a given allele in a population is determined by the frequency of the allele and by the relative risk of breast cancer that it confers. In Poland founder alleles of the BRCA1, CHEK2 and NBS1 genes have been associated with an increased risk of breast cancer, but the relative contribution of each of these alleles to the overall breast cancer burden has not yet been determined. We screened 2012 unselected cases of breast cancer and 4000 population controls for 7 different mutations in these genes. Overall, a mutation was found in 12% of the cases and in 6% of the controls. Mutations in BRCA1 and CHEK2 contributed in approximately equal measure to the burden of breast cancer in Poland. A BRCA1 mutation was present in 3% of the cases. The missense BRCA1 mutation C61G was associated with a higher odds ratio for breast cancer (OR=15) than were either of the truncating BRCA1 mutations 4153delA (OR=2.0) and 5382insC (OR=6.2). In contrast, a higher odds ratio was seen for truncating CHEK2 mutations (OR=2.1) than for the missense mutation I157T (OR=1.4). This study suggests that cancer risks may be specific for particular alleles of a susceptibility gene and that these different risks should be taken into account by genetic counselors.

Results of a phase II open-label, non-randomized trial of cisplatin chemotherapy in patients with BRCA1-positive metastatic breast cancer

IntroductionThe purpose of this investigation was to evaluate the efficacy of cisplatin chemotherapy in BRCA1 mutation carriers with metastatic breast cancer.MethodsIn a phase II, open-label study, 20 patients with metastatic breast cancer who carried a mutation in BRCA1 were treated with cisplatin 75 mg/m2 intravenously every 3 weeks as part of a 21-day cycle for 6 cycles. Restaging studies to assess response were performed after cycles 2 and 6, and every three months thereafter.ResultsBetween July 2007 and January 2009, 20 patients were enrolled. Baseline characteristics were as follows: 65% had prior adjuvant chemotherapy, 55% had prior chemotherapy for metastatic breast cancer; mean age was 48 years (ranges 32 to 70); 30% estrogen receptor (ER) or progesterone receptor (PR)+, 70% ER/PR/Human Epidermal Growth Factor Receptor 2 (HER2)- and 0% HER2+. Overall response rate was 80%; nine patients experienced a complete clinical response (45%) and seven experienced a partial response (35%). Overall survival was 80% at one year, 60% at two years and 25% at three years. Four of the 20 patients are alive four years after initiating treatment. The median time to progression was 12 months. The median survival from the start of cisplatinum treatment was 30 months. Cisplatin-related adverse events, including nausea (50%), anemia (5%) and neutropenia (35%) were mostly mild to moderate in severity.ConclusionsThis phase II study demonstrates that cisplatin chemotherapy has high activity in women with a BRCA1 mutation and metastatic breast cancer and is generally well tolerated.Trial registrationThis trial is registered retrospectively on the clinical trials website ClinicalTrials.gov. The identifier is NCT01611727.

A Range of Cancers Is Associated with the rs6983267 Marker on Chromosome 8

Several genome-wide searches for common cancers have lead to the identification of a small number of loci that harbor low-risk cancer susceptibility markers. One marker, rs6983267 on chromosome 8q24, has been linked to both colon and prostate cancer, and is therefore a good candidate for a multicancer susceptibility marker. To determine the range of cancer sites associated with rs6983267, we genotyped 7,665 cases of cancer, representing 11 common cancer sites, and 1,910 controls. A significant odds ratio (OR) was observed for prostate cancer for carriers of genotype GG [OR, 1.77; 95% confidence interval (CI), 1.47-2.13]. The homozygote OR was higher for tumors with Gleason score 8 to 10 (OR, 1.94; 95% CI, 1.18-3.20) than for tumors with Gleason score 7 and below (OR, 1.65; 95% CI, 1.31-2.08). Significantly elevated (homozygote) ORs were observed for 4 other cancer sites, including colon (OR, 1.36; 95% CI, 1.08-1.72), kidney (OR, 1.52; 95% CI, 1.12-2.05), thyroid (OR, 1.37; 95% CI, 1.02-1.82), and larynx (OR, 1.39; 95% CI, 1.02-1.90). Information was available on family histories of cancer for eight sites. For six of the eight sites (prostate, breast, bladder, larynx, lung, and kidney), the homozygote ORs were higher for cases with a positive family history (at least one first-degree with any cancer) than for cases with unaffected first-degree relatives. Our results suggest that the range of cancers associated with the rs6983267 marker might be larger than previously thought.

Risk of Breast Cancer in Women With a CHEK2 Mutation With and Without a Family History of Breast Cancer

PURPOSE To estimate the risk of breast cancer in a woman who has a CHEK2 mutation depending on her family history of breast cancer. PATIENTS AND METHODS Seven thousand four hundred ninety-four BRCA1 mutation-negative patients with breast cancer and 4,346 control women were genotyped for four founder mutations in CHEK2 (del5395, IVS2+1G>A, 1100delC, and I157T). RESULTS A truncating mutation (IVS2+1G>A, 1100delC, or del5395) was present in 227 patients (3.0%) and in 37 female controls (0.8%; odds ratio [OR], 3.6; 95% CI, 2.6 to 5.1). The OR was higher for women with a first- or second-degree relative with breast cancer (OR, 5.0; 95% CI, 3.3 to 7.6) than for women with no family history (OR, 3.3; 95% CI, 2.3 to 4.7). If both a first- and second-degree relative were affected with breast cancer, the OR was 7.3 (95% CI, 3.2 to 16.8). Assuming a baseline risk of 6%, we estimate the lifetime risks for carriers of CHEK2 truncating mutations to be 20% for a woman with no affected relative, 28% for a woman with one second-degree relative affected, 34% for a woman with one first-degree relative affected, and 44% for a woman with both a first- and second-degree relative affected. CONCLUSION CHEK2 mutation screening detects a clinically meaningful risk of breast cancer and should be considered in all women with a family history of breast cancer. Women with a truncating mutation in CHEK2 and a positive family history of breast cancer have a lifetime risk of breast cancer of greater than 25% and are candidates for magnetic resonance imaging screening and for tamoxifen chemoprevention.

A large germline deletion in the Chek2 kinase gene is associated with an increased risk of prostate cancer

Background: Germline mutations in the Chek2 kinase gene (CHEK2) have been associated with a range of cancer types. Recently, a large deletion of exons 9 and 10 of CHEK2 was identified in several unrelated patients with breast cancer of Czech or Slovak origin. The geographical and ethnic extent of this founder allele has not yet been determined. Participants and methods: We assayed for the presence of this deletion, and of three other CHEK2 founder mutations, in 1864 patients with prostate cancer and 5496 controls from Poland. Results: The deletion was detected in 24 of 5496 (0.4%) controls from the general population, and is the most common CHEK2 truncating founder allele in Polish patients. The deletion was identified in 15 of 1864 (0.8%) men with unselected prostate cancer (OR 1.9; 95% CI 0.97 to 3.5; p = 0.09) and in 4 of 249 men with familial prostate cancer (OR 3.7; 95% CI 1.3 to 10.8; p = 0.03). These ORs were similar to those associated with the other truncating mutations (IVS2+1G→A, 1100delC). Conclusion: A large deletion of exons 9 and 10 of CHEK2 confers an increased risk of prostate cancer in Polish men. The del5395 founder deletion might be present in other Slavic populations, including Ukraine, Belarus, Russia, Baltic and Balkan countries. It will be of interest to see to what extent this deletion is responsible for the burden of prostate cancer in other populations.

Germline RECQL mutations are associated with breast cancer susceptibility

Several moderate- and high-risk breast cancer susceptibility genes have been discovered, but more are likely to exist. To discover new breast cancer susceptibility genes, we used 2 populations (from Poland and Quebec, Canada) and applied whole-exome sequencing in a discovery phase (n = 195), followed by validation. We identified rare recurrent RECQL mutations in each population. In Quebec, 7 of 1,013 higher-risk breast cancer cases and 1 of 7,136 newborns carried the c.643C>T (p.Arg215*) variant (P = 0.00004). In Poland, 30 of 13,136 unselected breast cancer cases and 2 of 4,702 controls carried the c.1667_1667+3delAGTA (p.K555delinsMYKLIHYSFR) variant (P = 0.008). RECQL is implicated in resolving stalled DNA replication forks to prevent double-stranded DNA (dsDNA) breaks. This function is related to that of other known breast cancer susceptibility genes, many of which are involved in repairing dsDNA breaks. We conclude that RECQL is a breast cancer susceptibility gene.