CHEK2 1100delC mutation is frequent among Russian breast cancer patients

This study was aimed to assess the role of CHEK2 1100delC mutation in breast cancer (BC) predisposition in Russia. The 1100delC allele was detected in 14/660 (2.1%) unilateral BC cases and in 8/155 (5.2%) patients with the bilateral form of the disease, but only in 1/448 (0.2%) middle-aged control females and in none of 373 elderly tumor-free women. The obtained data point at potentially high clinical relevance of CHEK2 1100delC testing in females of Russian origin and warrant similar case-control studies in ethnically and geographically related regions, especially in Ukraine, Belarus and Baltic countries.     

Survival and contralateral breast cancer in CHEK2 1100delC breast cancer patients: impact of adjuvant chemotherapy

Background:

We assessed the sensitivity to adjuvant chemotherapy in cell cycle checkpoint kinase 2 (CHEK2) vs non-CHEK2 breast cancer patients by comparing the contralateral breast cancer incidence and distant disease-free and breast cancer-specific survival between both groups, stratified for adjuvant chemotherapy.

Methods:

One Dutch hereditary non-BRCA1/2 breast cancer patient cohort (n=1220) and two Dutch cohorts unselected for family history (n=1014 and n=2488, respectively) were genotyped for CHEK2 1100delC. Hazard ratios for contralateral breast cancer, distant disease-free and breast cancer-specific death for mutation carriers vs noncarriers were calculated using the Cox proportional hazard method, stratified for adjuvant chemotherapy.

Results:

The CHEK2 mutation carriers (n=193) had an increased incidence of contralateral breast cancer (multivariate hazard ratio 3.97, 95% confidence interval 2.59–6.07). Distant disease-free and breast cancer-specific survival were similar in the first 6 years in mutation carriers compared with noncarriers, but diverted as of 6 years after breast cancer diagnosis (multivariate hazard ratios and 95% confidence intervals 2.65 (1.79–3.93) and 2.05 (1.41–2.99), respectively). No significant interaction between CHEK2 and adjuvant chemotherapy was observed.

Conclusions:

The CHEK2 1100delC-associated breast cancer is associated with a higher contralateral breast cancer rate as well as worse survival measures beyond 6 years after diagnosis. No differential sensitivity to adjuvant chemotherapy was observed in CHEK2 patients.     

CHEK2 1100delC Variant and Breast Cancer Risk in Caucasians: A Meta-analysis Based on 25 Studies with 29,154 Cases and 37,064 Controls

Links between the CHEK2 1100delC heterozygote and breast cancer risk have been extensively explored.However, both positive and negative associations with this variant have been reported in individual studies. Fora detailed assessment of the CHEK2 1100delC heterozygote and breast cancer risk, relevant studies published asrecently as May 2012 were identified using PUBMED and EMBASE and selected using a priori defined criteria.The strength of the relationship between the CHEK2 1100delC variant and breast cancer risks was assessed byodds ratios (ORs) under the fixed effects model. A total of 29,154 cases and 37,064 controls from 25 case-controlstudies were identified in this meta-analysis. The CHEK2 1100delC heterozygote was more frequently detectedin cases than in controls (1.34% versus 0.44%). A significant association was found between CHEK2 1100delCheterozygote and breast cancer risk (OR=2.75, 95% CI: [2.25, 3.36]). The ORs and CIs were 2.33 (95% CI: [1.79,3.05]), 3.72 (95% CI: [2.61, 5.31]) and 2.78 (95% CI: [2.28, 3.39]) respectively in unselected, family, early-onsetbreast cancer subgroups. The CHEK2 1100delC variant could be a potential factor for increased breast cancerrisk in Caucasians. However, more consideration is needed in order to apply it to allele screening or other clinicalwork.     

The <Emphasis Type="Italic">CHEK2</Emphasis> 1100delC mutation is not present in Korean patients with breast cancer cases tested for <Emphasis Type="Italic">BRCA1</Emphasis> and <Emphasis Type="Italic">BRCA2</Emphasis> mutation

The germline CHEK2 1100delC mutation is a low penetrance breast cancer susceptibility allele, frequently observed in patient with family history of breast cancer and/or young age and the frequency varied according to race or ethnicity. In this study, we evaluated the significance of CHEK2 1100delC in predisposition to breast cancer by assessing its frequency in a material of 493 Korean breast cancer patients who had been screened for BRCA1 and BRCA2 mutations (42 patients had deleterious mutation of BRCA1/2). Mutation detection of CHEK2 1100delC was based upon analysis of primer extension products generated for previously amplified genomic DNA using a chip based MALDI-TOP mass spectrometry platform. After overall measurement automatically, assays which had bad peaks were checked again manually. None of the 493 Korean patients with breast cancer who were candidate for BRCA1 and BRCA2 test carried the 1100delC mutation observed in Caucasians with limited frequency. In the previous studies, we observed higher or comparable prevalence of BRCA1 and BRCA2 mutations in Korean patients with breast cancer compared to Caucasian breast cancer population. In the present study, we evaluated the role of a CHEK2 1100delC as a susceptibility mutation of breast cancer in the Korean population. However, our results suggest that this mutation is absent or may be very infrequent in Korean patients with breast cancer who have high risk of BRCA1 and BRCA2 mutation, making its screening irrelevant from the practical point view.     

The breast cancer low-penetrance allele 1100delC in the CHEK2 gene is not present in Spanish familial breast cancer population

Searching for low-penetrance genes involved in breast cancer susceptibility has been a field of interest in the last few years. Recently, the CHEK 2 gene, involved in DNA damage and replication checkpoints, has been pointed out as a good candidate; moreover, a specific variant in this gene,1100delC, has been found to increase breast cancer susceptibility among familial breast cancer cases not attributable to mutations in BRCA1 or BRCA2 genes. In our present study, we evaluated the role of the 1100delC variant as a susceptibility allele in breast cancer in the Spanish population. However, our results suggest that this variant is absent or very infrequent in our population, making its screening irrelevant from the practical point of view.     

CHEK2 1100delC mutation in Russian ovarian cancer patients

BRCA1 and BRCA2 germ-line mutations occur in a significant number of unselected ovarian cancer (OC) patients, thus making a noticeable contribution to OC morbidity. It is of interest whether CHEK2, which is frequently regarded as a third breast cancer specific gene, is also relevant to ovarian cancer pathogenesis. In this report we analyzed the presence of CHEK2 1100 delC founder mutation in 268 randomly recruited OC patients. The mutation was identified in 2 women with OC (0.8%) as compared to 1/448 (0.2%) healthy middle-aged and 0/373 elderly tumour-free women. Taken together this result and the negative findings of two other published reports on an association of CHEK2 with ovarian cancer indicate that there is no justification for intensive ovarian cancer screening in CHEK2 1100 delC carriers.     

Risk for contralateral breast cancer among carriers of the CHEK2*1100delC mutation in the WECARE Study

The protein encoded by the CHEK2 gene is involved in cellular repair of DNA damage. The truncating mutation, CHEK2*1100delC, seems to increase the risk for breast cancer. We investigated whether the CHEK2*1100delC mutation carrier status increases the risk for asynchronous contralateral breast cancer (CBC) and whether it interacts with radiation therapy (RT) or chemotherapy in regard to CBC risk. The germline mutation frequency was assessed in 708 women with CBC and 1395 women with unilateral breast cancer (UBC) in the Women's Environment, Cancer and Radiation Epidemiology (WECARE) Study whose first primary breast cancer was diagnosed before age 55 years and during 1985--1999. Seven women with CBC (1.0%) and 10 women with UBC (0.7%) were CHEK2*1100delC variant carriers (rate ratio (RR)=1.8, 95% confidence interval (CI)=0.6-5.4 for CBC vs UBC). Carriers who received RT for their first breast cancer, compared with non-carriers not treated with RT, had an RR of developing CBC of 2.6 (95% CI=0.8-8.7). We found no significant associations between the CHEK2*1100delC mutation and CBC overall or among those treated with RT. However, the sampling variability was such that modest increases in risk could not be excluded. Nonetheless, because this is a rare mutation, it is unlikely to explain a major fraction of CBC in the population.     

Synergistic interaction of variants in CHEK2 and BRCA2 on breast cancer risk

We studied the effects of BRCA2 and CHEK2 variants on breast cancer risk in two case-control series from Poland and Belarus. The missense BRCA2 variant T1915M was associated with a significant reduction in breast cancer risk (OR = 0.62; 95% CI 0.49–0.79; P = 0.0007). Modest increases of breast cancer risk were observed for the four analysed CHEK2 variants (I157T, 1100delC, IVS2 + 1G > A and del5395) (OR = 2.2; 95% 1.7–2.8; P = 0.0001). The highest risk was observed among women who carried both a BRCA2 and a CHEK2 variant (OR = 5.7; 95% CI 1.7–19; P = 0.006). We observed a statistically significant interaction effect between CHEK2 mutations and the BRCA2 substitution (P = 0.03). These data suggest that the BRCA2 T1915M polymorphism alone might be associated with a reduced risk of breast cancer, but among CHEK2 mutation carriers, it may lead to an unexpectedly high risk.

Founder mutations in early-onset, familial and bilateral breast cancer patients from Russia

Previous studies indicate that founder mutations may play a noticeable role in breast cancer (BC) predisposition in Russia. Here we performed a systematic analysis of eight recurrent mutations in 302 BC cases (St.-Petersburg, Russia), which were selected due to the presence of clinical indicators of hereditary disease (bilaterality and/or early onset (≤40 years) and/or family history). BC-associated alleles were revealed in 46 (15.2%) women. BRCA1 5382insC mutation was detected in 29 (9.6%) patients, CHEK2 1100delC in 9 (3.0%), BRCA1 4153delA in 3 (1.0%), CHEK2 IVS2+1G>A in 2 (0.7%), and BRCA1 185delAG, BRCA2 6174delT and NBS1 657del5 in 1 (0.3%) patient each. No cases with BRCA1 300T>G (C61G) mutation was identified. The obtained data suggest that a significant fraction of hereditary BC cases in Russia can be diagnosed using only a limited number of simple PCR tests.     

BRCA1/BRCA2 rearrangements and CHEK2 common mutations are infrequent in Italian male breast cancer cases

Male breast cancer (MBC) is a rare and poorly known disease. Germ-line mutations of BRCA2 and, to lesser extent, BRCA1 genes are the highest risk factors associated with MBC. Interestingly, BRCA2 germ-line rearrangements have been described in high-risk breast/ovarian cancer families which included at least one MBC case. Germ-line mutations of CHEK2 gene have been also implicated in inherited MBC predisposition. The CHEK2 1100delC mutation has been shown to increase the risk of breast cancer in men lacking BRCA1/BRCA2 mutations. Intriguingly, two other CHEK2 mutations (IVS2+1G>A and I157T) and a CHEK2 large genomic deletion (del9-10) have been associated with an elevated risk for prostate cancer. Here, we investigated the contribution of BRCA1, BRCA2 and CHEK2 alterations to MBC predisposition in Italy by analysing a large series of MBC cases, unselected for breast cancer family history and all negative for BRCA1/BRCA2 germ-line mutations. A total of 102 unrelated Italian MBC cases were screened for deletions/duplications of BRCA1, BRCA2 and CHEK2 by multiplex ligation-dependent probe amplification. No BRCA1, BRCA2 and CHEK2 genomic rearrangements, including the CHEK2 del9-10, were found in the series analysed. Furthermore, none of the MBC cases and 263 male population controls, also included in this study, carried the CHEK2 1100delC, IVS2+1G>A and I157T common mutations. Overall, our data suggest that screening of BRCA1/2 rearrangements is not advantageous in MBC cases not belonging to high-risk breast cancer families and that common CHEK2 mutations play an irrelevant role in MBC predisposition in Italy.     

<Emphasis Type="Italic">CHEK2</Emphasis> 1100delC and male breast cancer in the Netherlands

Mutations in the breast cancer susceptibility genes BRCA1, BRCA2, and CHEK2 are known risk factors for female breast cancer. Mutations in BRCA1 and BRCA2 also are associated with male breast cancer (MBC). Similarly, it had been suggested in the original CHEK2 identification report that the CHEK2 1100delC mutation confers an increased risk for MBC. Here, we have evaluated the risk of CHEK2 1100delC for MBC by genotyping CHEK2 1100delC in 23 familial and 71 unselected Dutch MBC cases. None of the 23 familial MBC cases carried the CHEK2 1100delC mutation. In contrast, CHEK2 1100delC was present in 3 of the 71 (4.2%) unselected MBC cases, which was significantly more prevalent than the 1.1% Dutch population frequency assessed in 1,692 individuals (P = 0.05, OR = 4.1, 95% CI 1.2–14.3). Our data suggest that, in the Netherlands, CHEK2 1100delC is associated with an increased risk for MBC.     

Correlation of CHEK2 protein expression and c.1100delC mutation status with tumor characteristics among unselected breast cancer patients

The CHEK2 kinase is a tumor suppressor whose activation in response to DNA double-strand breaks contributes to cell cycle arrest or apoptosis. The c.1100delC mutation is associated with familial breast cancer, and tumors from mutation carriers show reduced or absent CHEK2 protein expression. We have here studied CHEK2 protein expression by immunohistochemistry on a tissue microarray of 611 unselected breast tumors and also evaluated the tumor characteristics among 1,297 unselected breast cancer patients defined for the c.1100delC germ line mutation status (2.5% carrier frequency). CHEK2 protein expression was reduced in 21.1% of the unselected breast cancers studied. Tumors with reduced CHEK2 expression had more often larger primary tumor size (pT3-4; nominal significance p = 0.002) compared to tumors with normal staining. A similar trend for larger tumor size was seen among the 37 breast tumors from c.1100delC germ line mutation carriers. Tumors from c.1100delC mutation carriers were of higher grade than those of noncarriers (nominal significance p = 0.02). The c.1100delC germ line mutation also associated strongly with bilateral breast cancer. No significant correlation was seen between CHEK2 status and hormone receptor status, histology, lymph node status, or overall survival.     

BRCA1, BRCA2 and CHEK2 (1100 del C) Germline Mutations in Hereditary Breast and Ovarian Cancer Families in South India

Cancer of the breast is the second most common cancer seen among Indian women. This study describes the use ‍of DHPLC for mutation analysis for BRCA1, BRCA2 and CHEK2 (1100delC) in 22 patients with a family history of ‍breast and/or ovarian cancer and early onset breast cancer (<35 years of age). Three of the 22 patients were found to ‍have a non-sense mutation or a deletion, resulting in a premature stop codon, potentially leading to a truncated ‍protein. Two of these were in BRCA1 (one was a novel 5 base deletion) and one in the BRCA2 gene. No patient was ‍found in our series to have the CHEK2 (1100delC) mutation. DNA from a healthy blood donor and all but one of the ‍22 patients, demonstrated polymorphisms in BRCA1 and/or BRCA2 genes. This is the first study from South India, ‍on BRCA1, BRCA2 & CHEK2 (1100 del C) mutations in patients with a family history of breast and/or ovarian ‍cancer and early onset breast/ovarian cancer, using the sensitive DHPLC approach.     

Models for predicting BRCA1 and BRCA2 mutations in Han Chinese familial breast and/or ovarian cancer patients

Purpose Our aim was to find an appropriate method to estimate the likelihood that a family history of cancer was a result of a mutation in the BRCA1 or BRCA2 genes. We also compared the performance of the established method with three different methods (Couch, Sh-E and BRCApro) to identify an alternative strategy for genetic council targeted to the specified population. Patients and methods The family history as well as individual information of two hundred unrelated probands who had completed BRCA1 and BRCA2 mutation screening was analyzed to assess the likelihood of a pathogenic mutation. A model was developed by empirical method. The performance of this model was validated in a separate patient cohort compared with BRCApro. Results Several factors were associated with mutations in univariate analysis and a logistic model was devised to estimate the probability for a proband of harboring a mutation in BRCA1 and/or BRCA2. Using a greater than 10% probability threshold, the highest accuracy was achieved by the established model when compared to other three models, presenting the highest sensitivity, PPV, NPV and area under ROC curve. The empirical model showed a better ROC curve compared to BRCApro in the verification cohort. Conclusion A probability model targeted to Han Chinese population should be a useful tool in the genetic counseling for the specified ethnic. Its ability to predict BRCA2 mutation carriers needs to be improved. Nan-Yan Rao and Zhen Hu are contributed equally to this work.     

BRCA2, but not BRCA1, mutations account for familial ovarian cancer in Iceland: a population-based study

A single founder mutation in each of the BRCA genes has been identified in Iceland. The frequency of the BRCA1 G5193A and BRCA2 999del5 mutations in all ovarian cancer patients diagnosed over the period 1991–2000 was determined. Mutation status was correlated with family history, tumour morphology and age at diagnosis. Samples from 86% of cases (179 carcinomas and 74 borderline tumours) were available. In the carcinomas, BRCA1 and BRCA2 mutations were present in 1.2% and 6% of cases, respectively. No BRCA mutations were found in the borderline tumours. Odds Ratio (OR) of developing ovarian cancer was 20.65 for BRCA2 carriers. Family history of breast/ovarian cancer was present for 70% of BRCA2 carriers and approximately 14% for non-carriers with carcinoma. In conclusion, BRCA2 999del5 is present in 6% of ovarian cancer cases in Iceland and is associated with a 20-fold increase in the risk of the disease. The BRCA1 G5193A mutation is too rare to contribute significantly to ovarian cancer in Iceland.     

Analysis of <Emphasis Type="Italic">CHEK2</Emphasis> FHA domain in Czech patients with sporadic breast cancer revealed distinct rare genetic alterations

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. Zdenek Kleibl, Ondrej Havranek contributed equally to this work.     

Association of the C677T polymorphism in the MTHFR gene with breast and/or ovarian cancer risk in Jewish women

The C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with reduced enzyme activity, hyperhomocysteinaemia and increased risk for atherosclerosis in homozygotes. We examined the frequency of this mutation and its association with disease pattern in 491 Jewish women with either sporadic (n=355; 72%) or hereditary (n=136; 28%) breast and/or ovarian cancer and in 69 asymptomatic BRCA1/2 mutation carriers, genotyped for the three predominant Jewish founder BRCA1/2 mutations (185delAG, 5382insC and 6174delT). 677T homozygotes were equally distributed among women with sporadic breast and/or ovarian cancer (71/355; 20.0%) and among BRCA1/2 mutation carriers (43/205; 21.0%) (P=non-significant). 677T homozygotes were equally distributed among women diagnosed with breast cancer prior to (22/122; 18.0%) and after 42 years of age (42/243; 17.3%). Among BRCA1/2 carriers, the rate of 677T homozygotes in manifesting cancer (32/136; 23.5%) and asymptomatic individuals (11/69; 15.9%) was not significantly different. The rate of 677T homozygotes (24/72; 33.3%) was higher (P=0.0026) among women with bilateral breast cancer and those with both breast and ovarian carcinoma than among those with unilateral breast cancer (64/365; 17.5%). Differences in morbidity (one versus multiple breast/ovarian tumours) are mainly attributed to 677T homozygosity and partly to BRCA1/2 mutations. Confirmation of these data, namely, that the 677T allele is significantly more common in cases of bilateral breast cancer or combined breast and ovarian cancer would have important clinical implications.     

BRCA1 and BRCA2 germline mutational spectrum and evidence for genetic anticipation in Portuguese breast/ovarian cancer families

We present the first characterisation of the mutational spectrum of the entire coding sequences and exon–intron boundaries of the BRCA1 and BRCA2 genes as well as large BRCA1 rearrangements in Portuguese families with inherited predisposition to breast/ovarian cancer. Of the 100 probands studied, pathogenic mutations were identified in 22 (24.7%) of 89 breast and/or ovarian cancer families with more than one affected member (15 in BRCA1 and seven in BRCA2), but in none of the 11 patients without family history of cancer. One (6.7%) of the BRCA1 mutations is a large deletion involving exons 11–15. Seven pathogenic point mutations are novel: 2088C>T, 2156delinsCC, and 4255_4256delCT in BRCA1 and 4608_4609delTT, 5036delA, 5583_5584insT, and 8923C>T in BRCA2. The novel 2156delinsCC was identified in three probands from different families and probably represents a founder mutation in our population. We also found a previously reported 3450_3453del4 mutation in three unrelated patients. In addition to the 22 pathogenic mutations, we identified 19 missense mutations of uncertain pathogenic significance, three of them (5241G>C in BRCA1 and IVS6+13C>T and 3731T>C in BRCA2) previously undescribed. The percentage of cases with truncating mutations in BRCA1 and BRCA2 was higher in breast/ovarian cancer (37.0%, mostly BRCA1) and male breast cancer (40%, all BRCA2) families than in families with only female breast cancer (17.5%). Interestingly, we found evidence for genetic anticipation regarding age at diagnosis of both breast and ovarian cancer in those families presenting affected members in more than one generation. These findings should be taken into consideration while planning screening and prophylactic measures in families with inherited predisposition to breast and ovarian cancer.