High frequency of BRCA1, but not CHEK2 or NBS1 (NBN), founder mutations in Russian ovarian cancer patients

Targeted next-generation sequencing of 21 candidate genes in hereditary ovarian cancer patients from the Republic of Bashkortostan

About 5-10% of all ovarian cancer cases show familial clustering, and some 15-25% of familial ovarian cancer cases are mediated by high-penetrance mutations in the BRCA1 and BRCA2 genes. Only few other genes have been identified for familial ovarian cancer.We conducted targeted next-generation sequencing of the protein coding region of 21 candidate genes, including UTR regions, in genomic DNA samples of 48 patients with familial ovarian cancer from the Republic of Bashkortostan. We identified deleterious variants in BRCA1, BRCA2, CHEK2, MSH6 and NBN in a total of 16 patients (33%). The NBN truncating variant, p.W143X, had not previously been reported. Seven patients (15%) were carriers of the c.5266dupC variant in BRCA1, supporting a Russian origin of this founder allele. An additional 15 variants of uncertain clinical significance were observed. We conclude that our gene panel explains about one-third of familial ovarian cancer risk in the Republic of Bashkortostan.

BRCA Mutations-The Achilles Heel of Breast, Ovarian and Other Epithelial Cancers

Two related tumor suppressor genes, BRCA1 and BRCA2, attract a lot of attention from both fundamental and clinical points of view. Oncogenic hereditary mutations in these genes are firmly linked to the early onset of breast and ovarian cancers. However, the molecular mechanisms that drive extensive mutagenesis in these genes are not known. In this review, we hypothesize that one of the potential mechanisms behind this phenomenon can be mediated by Alu mobile genomic elements. Linking mutations in the BRCA1 and BRCA2 genes to the general mechanisms of genome stability and DNA repair is critical to ensure the rationalized choice of anti-cancer therapy. Accordingly, we review the literature available on the mechanisms of DNA damage repair where these proteins are involved, and how the inactivating mutations in these genes (BRCAness) can be exploited in anti-cancer therapy. We also discuss a hypothesis explaining why breast and ovarian epithelial tissues are preferentially susceptible to mutations in BRCA genes. Finally, we discuss prospective novel therapeutic approaches for treating BRCAness cancers.

A spectrum of BRCA1 and BRCA2 germline deleterious variants in ovarian cancer in Russia

PURPOSE

Pathogenic variants (PVs) in BRCA1 and BRCA2 genes are essential biomarkers of an increased breast and ovarian cancer risk and tumor sensitivity to poly ADP ribose polymerase inhibitors. In Russia, eight PVs were thought to be the most common, among which BRCA1 c.5266dup is the most frequently identified one.

METHODS

We show the distribution of BRCA1/2 PVs identified with quantitative PCR and targeted next-generation sequencing in 1399 ovarian cancer patients recruited into the study from 72 Russian regions in 2015-2021.

RESULTS

The most abundant PVs were c.5266dup (41.0%), c.4035del (7.0%), c.1961del (6.3%), c.181 T > G (5.2%), c.3756_3759del (1.8%), c.3700_3704del (1.5%), and c.68_69del (1.5%), all found in BRCA1 and known to be recurrent in Russia. Several other frequent PVs were identified: c.5152 + 1G > T (1.2%), c.1687C > T (1.0%), c.4689C > G (0.9%), c.1510del (0.6%), c.2285_2286del (0.6%) in the BRCA1 gene; and c.5286 T > G (1.2%), c.2808_2811del (0.8%), c.3847_3848del (0.8%), c.658_659del (0.7%), c.7879A > T (0.6%), in the BRCA2 gene. For the most common PV in the BRCA2 gene c.5286 T > G, we suggested that it arose about 700 years ago and is a new founder mutation.

CONCLUSION

This study extends our knowledge about the BRCA1 and BRCA2 pathogenic variants variability.

Application Areas of Traditional Molecular Genetic Methods and NGS in relation to Hereditary Urological Cancer Diagnosis

Next generation sequencing (NGS) is widely used for diagnosing hereditary cancer syndromes. Often, exome sequencing and extended gene panel approaches are the only means that can be used to detect a pathogenic germline mutation in the case of multiple primary tumors, early onset, a family history of cancer, or a lack of specific signs associated with a particular syndrome. Certain germline mutations of oncogenes and tumor suppressor genes that determine specific clinical phenotypes may occur in mutation hot spots. Diagnosis of such cases, which involve hereditary cancer, does not require NGS, but may be made using PCR and Sanger sequencing. Diagnostic criteria and professional community guidelines developed for hereditary cancers of particular organs should be followed when ordering molecular diagnostic tests for a patient. This review focuses on urological oncology associated with germline mutations. Clinical signs and genetic diagnostic laboratory tests for hereditary forms of renal cell cancer, prostate cancer, and bladder cancer are summarized. While exome sequencing, or, conversely, traditional molecular genetic methods are the procedure of choice in some cases, in most situations, sequencing of multigene panels that are specifically aimed at detecting germline mutations in early onset renal cancer, prostate cancer, and bladder cancer seems to be the basic solution for molecular genetic diagnosis of hereditary cancers.

Identification of deleterious germline CHEK2 mutations and their association with breast and ovarian cancer

Germline mutations in checkpoint kinase 2 (CHEK2), a multiple cancer-predisposing gene, increase breast cancer (BC) risk; however, risk estimates differ substantially in published studies. We analyzed germline CHEK2 variants in 1,928 high-risk Czech breast/ovarian cancer (BC/OC) patients and 3,360 population-matched controls (PMCs). For a functional classification of VUS, we developed a complementation assay in human nontransformed RPE1-CHEK2-knockout cells quantifying CHK2-specific phosphorylation of endogenous protein KAP1. We identified 10 truncations in 46 (2.39%) patients and in 11 (0.33%) PMC (p = 1.1 × 10^-14 ). Two types of large intragenic rearrangements (LGR) were found in 20/46 mutation carriers. Truncations significantly increased unilateral BC risk (OR = 7.94; 95%CI 3.90-17.47; p = 1.1 × 10^-14 ) and were more frequent in patients with bilateral BC (4/149; 2.68%; p = 0.003), double primary BC/OC (3/79; 3.80%; p = 0.004), male BC (3/48; 6.25%; p = 8.6 × 10^-4 ), but not with OC (3/354; 0.85%; p = 0.14). Additionally, we found 26 missense VUS in 88 (4.56%) patients and 131 (3.90%) PMC (p = 0.22). Using our functional assay, 11 variants identified in 15 (0.78%) patients and 6 (0.18%) PMC were scored deleterious (p = 0.002). Frequencies of functionally intermediate and neutral variants did not differ between patients and PMC. Functionally deleterious CHEK2 missense variants significantly increased BC risk (OR = 3.90; 95%CI 1.24-13.35; p = 0.009) and marginally OC risk (OR = 4.77; 95%CI 0.77-22.47; p = 0.047); however, carriers low frequency will require evaluation in larger studies. Our study highlights importance of LGR detection for CHEK2 analysis, careful consideration of ethnicity in both cases and controls for risk estimates, and demonstrates promising potential of newly developed human nontransformed cell line assay for functional CHEK2 VUS classification.

Prevalence, spectrum, and founder effect of BRCA1 and BRCA2 mutations in epithelial ovarian cancer from the Middle East

Germline mutations in breast cancer susceptibility gene 1 and 2 have previously been estimated to contribute to 13-18% of all epithelial ovarian cancer (EOC). To characterize the prevalence and effect of BRCA1 and BRCA2 mutations in Middle Eastern EOC patients, BRCA mutation screening was performed in 407 unselected ovarian cancer patients using targeted capture and/or Sanger sequencing. A total of 19 different pathogenic variants (PVs) were identified in 50 (12.3%) women. Nine PVs were recurrent accounting for 80% of cases with PVs (40/50) in the entire cohort. Founder mutation analysis revealed only two mutations (c.4136_4137delCT and c.1140dupG) sharing the same haplotypes thus representing founder mutations in the Middle Eastern population. Identification of the mutation spectrum, prevalence, and founder effect in Middle Eastern population facilitates genetic counseling, risk assessment, and development of a cost-effective screening strategy.

BRCA1-associated and sporadic ovarian carcinomas: outcomes of primary cytoreductive surgery or neoadjuvant chemotherapy

OBJECTIVE

Tumors arising in BRCA1/2 mutation carriers are characterized by increased platinum sensitivity; however, it is unknown whether this feature should be considered while choosing between primary surgical versus systemic treatment. This study aimed to compare outcomes of ovarian cancer patients undergoing either primary surgery or interval cytoreduction based on BRCA1/2 status.

METHODS

The study included consecutive ovarian cancer patients, who were treated at the N.N. Petrov Institute of Oncology (St Petersburg, Russia) from 2000 to 2013 and who underwent complete or optimal cytoreductive surgery. A comparison of disease outcomes was performed for the total group of ovarian cancer patients as well as for 69 BRCA1-mutated and 151 sporadic high-grade serous advanced-stage ovarian carcinomas. Frequency comparisons were performed by Chi-square test or Fisher exact test. Disease-free interval and overall survival were analyzed by Mann-Whitney U-test and Kaplan-Meier method. Hazard ratios were calculated by Cox regression analysis.

RESULTS

The analysis included 283 consecutive patients who underwent optimal cytoreduction (size of residual tumor <1 cm (n=156)) or complete tumor excision (n=127) on primary surgery (n=168) or after neoadjuvant chemotherapy (n=115). 84 patients carried germline mutation in BRCA1 (n=77) or BRCA2 (n=7) genes, while 199 ovarian cancer patients were classified as sporadic. High-grade serous ovarian cancer patients treated with neoadjuvant chemotherapy had a lower disease-free interval compared with those undergoing primary surgery followed by adjuvant therapy (7.8 vs 14.2 months, p<0.001). This difference was attributed mainly to sporadic cases (5.1 vs 12.2 months, p<0.001), while BRCA1-associated cancers had a similar disease-free interval regardless of the sequence of treatments (12.5 vs 15.8 months, p=0.53). When treated with neoadjuvant chemotherapy, BRCA1-mutated patients had improved overall survival as compared with sporadic cases (45.7 vs 25.3 months, p=0.007), while patients subjected to primary surgery showed similar overall survival irrespective of BRCA1 status (54.6 vs 53.9 months, p=0.56). A total of 29/61 (48%) BRCA1/2-associated patients relapsed as a single local tumor; this was lower in sporadic cancer patients (38/134 (28%); p=0.01).

CONCLUSION

In BRCA1 mutation carriers, the oncologic outcomes are similar when comparing primary surgery versus neoadjuvant chemotherapy. In addition, BRCA1-mutation carriers often have a single site of disease when diagnosed with recurrent ovarian cancer.

Targeted sequencing to discover germline variants in the BRCA1 and BRCA2 genes in a Russian population and their association with breast cancer risk

BRCA1 and BRCA2 are tumor suppressor genes involved in the repair of DNA damage and transcriptional regulation of the cell cycle. Alterations in BRCA1/2 lead to production of functionally defective proteins that impair DNA repair. Certain mutant variants of BRCA1/2 are strongly associated with increased risk of breast and ovarian cancers, with emerging data on association with other types of cancer. However, variability of BRCA1/2 in Russian populations remains understudied. In this study, we performed targeted sequencing of BRCA1/2 in 145 breast cancer (BC) patients with a family history of BRCA-associated cancers and 47 age-matched cancer-free control individuals with or without a family history of cancer. Subjects for this study were recruited in the Voronezh region of the Russian Federation. We found that two polymorphic variants, rs1799967 (BRCA1) and rs4987117 (BRCA2), were strongly associated with the risk of BC. Both variants have not been previously reported as associated with risk of breast cancer. Presence of the rs4987117 variant increases risk of breast cancer onset (OR = 2.76, p-value = 0.022). Notably, although variant rs80357906 (5382InsC) has been reported as a risk factor for hereditary BC, it was not significantly associated with breast cancer risk in our population (p = 0.192). We also found 12 novel polymorphic variants in BRCA1/2 genes (2 in BRCA1 and 10 in BRCA2). However, none of these variants demonstrated association with the disease. Five germline variants were observed at high frequency (mean AF = 67.14%) and therefore can be considered as a common haplotype in the Voronezh region of the Russian Federation. In summary, our study demonstrates that known pathological variants of BRCA1/2 genes may not be reflective of breast cancer risk assessment when applied to the Russian population. Further, more extended population-specific studies are needed to reveal the reliable list of BRCA1/2 polymorphisms associated with risk of breast cancer in the Russian population.

Prevalence of two BRCA1 mutations, 5382insC and 300T > G, in ovarian cancer patients from Ukraine

Ovarian cancer is the seventh most common cancer in women worldwide and the leading cause of gynecological malignant diseases-related deaths in women. The most significant risk factor for ovarian cancer is an inherited genetic mutation in one of two genes: breast cancer gene 1 (BRCA1) or breast cancer gene 2 (BRCA2). The germline mutation c.5266dupC (also known as 5382insC or 5385insC) is the most common mutation among Slavic patients with breast and/or ovarian cancer. Missense mutation c.181T > G (also known as 300T > G or p.C61G) is regarded as the founder change in many Central European countries. We screened 306 ovarian cancer patients diagnosed at different ages by mutagenically separated polymerase chain reaction (PCR) and real-time PCR. A total of 25 BRCA1 mutations were detected (18 cases of 5382insC and 7 cases of 300 T > G). The frequency of the BRCA1 5382insC mutation is similar in breast and ovarian cancer patients from Ukraine, but the frequency of 300T > G was estimated in Ukraine at first time.

Impact of germline and somatic BRCA1/2 mutations: tumor spectrum and detection platforms

The BRCA1/2 genes are long and complex and mutation carriers are at risk of developing malignancies, mainly of gynecological origin. Various mutations arise in these genes and their characterization is a time-consuming, cost intensive, complicated process. Tumors of BRCA1/2 origin have distinct molecular and histological features that can impact responses to therapy. Therefore, detection of these mutations constitutes an important step in the risk assessment, prevention strategy and treatment of subjects. Although Sanger sequencing is the gold standard for the detection of genetic mutations, several next generation sequencing-based high throughput platforms have been developed and adapted for the detection of BRCA1/2 mutations. This review provides a comprehensive overview of the sequencing platforms available for the screening and identification of these mutations. We also summarize what is known about the different types of mutations that arise in these genes and the tumor spectra they result in. Finally, we present a short discussion on existing clinical guidelines which assist physicians in the decision-making process. These parameters have important consequences for the management of patients and an urgent need exists for the development of detection platforms that are cost effective and can provide clinicians with conclusive results within a significantly shorter time.

Genetic analysis of melanocortin 1 receptor red hair color variants in a Russian population of Eastern Siberia

The melanocortin 1 receptor is a G_s protein-coupled receptor implicated in melanogenesis regulation. The receptor gene is highly polymorphic, which accounts for the association of several of its single-nucleotide polymorphisms (SNPs) with an increased risk of melanoma. The present study aimed to evaluate the distribution of melanocortin 1 receptor gene variants R151C, R160W, and D294H within the Russian population of Eastern Siberia and its association with melanoma development. Melanoma patients (n=95) admitted to Krasnoyarsk Territorial Oncological Center and healthy controls (n=334) were enrolled in the study. A clinical examination of patients was performed to evaluate the phenotypic features of melanoma patients. SNPs were analyzed by real-time PCR. Clinical examination indicated a more frequent occurrence of fair skin type, blue eyes, blonde and red hair, and more frequent localization of freckles on the neck, trunk, and extremities in the melanoma group of patients. The R151C melanocortin 1 receptor gene variant was found in 18% of melanoma patients and associated with an increased likelihood of melanoma development (odds ratio=6.4; 95% confidence interval: 2.8–14.3; P=0.0001). The two remaining variant alleles of the melanocortin 1 receptor gene occurred with low frequency both in controls and in the melanoma group. The R160W SNP was identified neither in controls nor in melanoma patients. The D294H heterozygous variant was observed in 0.3% of individuals in the control group and in 1.1% of the patients in the melanoma group. Such an asymmetric distribution of the melanocortin 1 receptor within red hair color genotypes in the population under study compared with other populations may be because of Russian genetic homogeneity. Carriers of the mutant R151C allele should exercise caution in terms of exposure to the sun to avoid the risk of melanoma development.

High response rates to neoadjuvant platinum-based therapy in ovarian cancer patients carrying germ-line BRCA mutation

Preoperative therapy provides an advantage for clinical drug assessment, as it involves yet untreated patients and facilitates access to the post-treatment biological material. Testing for Slavic founder BRCA mutations was performed for 225 ovarian cancer (OC) patients, who were treated by platinum-based neoadjuvant therapy. 34 BRCA1 and 1 BRCA2 mutation carriers were identified. Complete clinical response was documented in 12/35 (34%) mutation carriers and 8/190 (4%) non-carriers (P = 0.000002). Histopathologic response was observed in 16/35 (46%) women with the germ-line mutation versus 42/169 (25%) patients with the wild-type genotype (P = 0.02). Somatic loss of heterozygosity (LOH) for the remaining wild-type BRCA1 allele was detected only in 7/24 (29%) post-neoadjuvant therapy residual tumor tissues as compared to 9/11 (82%) BRCA1-associated OC, which were not exposed to systemic treatment before the surgery (P = 0.009). Furthermore, comparison of pre- and post-treatment tumor material obtained from the same patients revealed restoration of BRCA1 heterozygosity in 2 out of 3 sample pairs presenting with LOH at diagnosis. The obtained data confirm high sensitivity of BRCA-driven OC to platinating agents and provide evidence for a rapid selection of tumor cell clones without LOH during the course of therapy.

Screening for common mutations in BRCA1 and BRCA2 genes: interest in genetic testing of Tunisian families with breast and/or ovarian cancer

BACKGROUND

In the Tunisian population, as yet a limited number of BRCA1/2 germline mutations have been reported in hereditary breast and/or ovarian cancer. These mutations are located in a few exons of BRCA1/2. The aim of the present study was to search for these mutations in 66 unrelated patients with hereditary breast and/or ovarian cancer in order to assess the interest in such a targeted approach for genetic testing in Tunisia.

MATERIALS AND METHODS

Blood specimens from the 66 Tunisian patients, with family history of breast and/or ovarian cancer, were collected at the Salah Azaiz Cancer Institute of Tunis. The exons 5, 20 and part of exon 11 of BRCA1 as well as part of exons 10 and 11 of BRCA2 were analyzed by Sanger sequencing.

RESULTS

12 patients had deleterious mutations in the BRCA1 or BRCA2 genes (18%), including a novel frame-shift mutation of BRCA1 (c.3751dup; 3780insT). Four distinct BRCA1 mutations were detected eight patients: c.5266dup (5382insC) and c.211dup (330insA) each in three patients, c.3751dup (3870insT) and c.4041_4042del (4160delAG) each in one patient. The four remaining cases all carried the same BRCA2 mutation, c.1310_1313del (1538delAAGA). Besides these deleterious mutations, eight polymorphisms and unclassified variants were detected, one of them being never reported (BRCA1c.3030T>G, p.Pro1010Pro).

CONCLUSION

In this study, we show that targeting relevant exons in BRCA1 and BRCA2 genes allows detection of a substantial percentage of mutations in the Tunisian population. Therefore such an approach may be of interest in genetic testing of high-risk breast and ovarian cancer families in Tunisia.

High prevalence of GPRC5A germline mutations in BRCA1-mutant breast cancer patients

In a search for new breast cancer (BC) predisposing genes, we performed a whole exome sequencing analysis using six patient samples of familial BC and identified a germline inactivating mutation c.183delG [p. Arg61fs] in an orphan G protein-coupled receptor GPRC5A. An extended case-control study revealed a tenfold enrichment for this mutation in BC patients carrying the 5382insC allele of BRCA1, the major founder mutation in the Russian population, compared to wild-type BRCA1 BC cases [6/117 (5.1%) vs. 8/1578 (0.5%), p = 0.0002]. In mammary tumors (n = 60), the mRNA expression of GPRC5A significantly correlated with that of BRCA1 (p = 0.00018). In addition, the amount of GPRC5A transcript was significantly lower in BC obtained from BRCA1 mutation carriers (n = 17) compared to noncarriers (n = 93) (p = 0.026). Accordingly, a siRNA-mediated knockdown of either BRCA1 or GPRC5A in the MDA-MB-231 human BC cell line reduced expression of GPRC5A or BRCA1, respectively. Knockdown of GPRC5A also attenuated radiation-induced BRCA1- and RAD51-containing nuclear DNA repair foci. Taken together, these data suggest that GPRC5A is a modifier of BC risk in BRCA1 mutation carriers and reveals a functional interaction of these genes.

NBN Gene Polymorphisms and Cancer Susceptibility: A Systemic Review

The relationship between DNA repair failure and cancer is well established as in the case of rare, high penetrant genes in high cancer risk families. Beside this, in the last two decades, several studies have investigated a possible association between low penetrant polymorphic variants in genes devoted to DNA repair pathways and risk for developing cancer. This relationship would be also supported by the observation that DNA repair processes may be modulated by sequence variants in DNA repair genes, leading to susceptibility to environmental carcinogens. In this framework, the aim of this review is to provide the reader with the state of the art on the association between common genetic variants and cancer risk, limiting the attention to single nucleotide polymorphisms (SNPs) of the NBN gene and providing the various odd ratios (ORs). In this respect, the NBN protein, together with MRE11 and RAD50, is part of the MRN complex which is a central player in the very early steps of sensing and processing of DNA double-strand breaks (DSBs), in telomere maintenance, in cell cycle control, and in genomic integrity in general. So far, many papers were devoted to ascertain possible association between common synonymous and non-synonymous NBN gene polymorphisms and increased cancer risk. However, the results still remain inconsistent and inconclusive also in meta-analysis studies for the most investigated E185Q NBN miscoding variant.

Evidence for predictive role of BRCA1 and bTUBIII in gastric cancer

Sensitivity of gastric cancer (GC) to conventional cytotoxic therapy may be at least in part attributed to molecular features of the tumor cells. We analyzed all patients with metastatic GC treated in the N.N. Petrov Institute of Oncology (St. Petersburg) within years 1999-2010 and identified 65 cases with evaluable treatment response and available biological material. Two of 65 patients (3 %) carried germ-line BRCA1 5382insC mutation and demonstrated particularly pronounced response to the treatment; both of their tumors showed loss of the remaining BRCA1 allele, thus confirming the causative role of BRCA1 heterozygosity in GC predisposition. RNA expression of TS, DPD, BRCA1, ERCC, TOP2A and bTUBIII was analyzed in the remaining 63 tumors. Low BRCA1 expression was associated with increased response rate [6/9 (67 %) vs. 17/54 (32 %), p = 0.04]. Low bTUBIII level correlated with the improved probability of tumor response [21/49 (43 %) vs. 1/13 (8 %), p = 0.02] and prolonged overall survival (10.5 vs. 7.1 months, p = 0.02); this trend was maintained both for taxane-containing and for taxane-free drug combinations. We conclude that GC should be considered as a part of BRCA1-related hereditary cancer syndrome. Tumors with BRCA1 inactivation and low bTUBIII expression demonstrate improved response to cytotoxic therapy.

BRCA1 gene mutations frequency estimation by allele-specific real-time PCR of pooled genomic DNA samples

The frequencies of four mutations in the BRCA1 gene (185delAG, T300G, 4153delA, and 5382insC) were estimated in the Russian population. The mutations were analyzed in 7920 DNA samples obtained from randomly selected Novosibirsk citizens and 570 samples from breast cancer patients at Siberian hospitals. The mutations were detected by allele-specific real-time PCR. The mutation analysis was performed with pooled DNA samples to reduce the cost of the study. The 5382insC mutation was found in 20 of 7920 (0.25%) population DNA samples and in 14 of 570 (2.46%) breast cancer samples; the T300G mutation was detected in 4 population samples (0.05%) and in 2 breast cancer samples (0.35%); the 185delAG or 4153delA mutations were not identified in any of the 7920 samples and were detected in 1 (0.18%) breast cancer case each.

Drug therapy for hereditary cancers

Tumors arising in patients with hereditary cancer syndromes may have distinct drug sensitivity as compared to their sporadic counterparts. Breast and ovarian neoplasms from BRCA1 or BRCA2 mutation carriers are characterized by deficient homologous recombination (HR) of DNA, that makes them particularly sensitive to platinum compounds or inhibitors of poly (ADP-ribose) polymerase (PARP). Outstandingly durable complete responses to high dose chemotherapy have been observed in several cases of BRCA-related metastatic breast cancer (BC). Multiple lines of evidence indicate that women with BRCA1-related BC may derive less benefit from taxane-based treatment than other categories of BC patients. There is virtually no reports directly assessing drug response in hereditary colorectal cancer (CRC) patients; studies involving non-selected (i.e., both sporadic and hereditary) CRC with high-level microsatellite instability (MSI-H) suggest therapeutic advantage of irinotecan. Celecoxib has been approved for the treatment of familial adenomatous polyposis (FAP). Hereditary medullary thyroid cancers (MTC) have been shown to be highly responsive to a multitargeted tyrosine kinase inhibitor vandetanib, which exerts specific activity towards mutated RET receptor. Given the rapidly improving accessibility of DNA analysis, it is foreseen that the potential predictive value of cancer-associated germ-line mutations will be increasingly considered in the future studies.

High frequency and allele-specific differences of BRCA1 founder mutations in breast cancer and ovarian cancer patients from Belarus

Breast cancer and ovarian cancer are common malignancies in Belarus accounting for about 3500 and 800 new cases per year, respectively. For breast cancer, the rates and age of onset appear to vary significantly in regions differentially affected by the Chernobyl accident. We assessed the frequency and distribution of three BRCA1 founder mutations 5382insC, 4153delA and Cys61Gly in two hospital-based series of 1945 unselected breast cancer patients and of 201 unselected ovarian cancer patients from Belarus as well as in 1019 healthy control females from the same population. Any of these mutations were identified in 4.4% of the breast cancer patients, 26.4% of the ovarian cancer patients and 0.5% of the controls. In the breast cancer patients, BRCA1 mutations were strongly associated with earlier age at diagnosis, with oestrogen receptor (ER) negative tumours and with a first-degree family history of breast cancer, although only 35% of the identified BRCA1 mutation carriers had such a family history. There were no marked differences in the regional distribution of BRCA1 mutations, so that the significant differences in age at diagnosis and family history of breast cancer patients from areas afflicted by the Chernobyl accident could not be explained by BRCA1. We next observed a higher impact and a shifted mutational spectrum of BRCA1 in the series of Byelorussian ovarian cancer patients where the three founder mutations accounted for 26.4% (53/201). While the Cys61Gly mutation appeared underrepresented in ovarian cancer as compared with breast cancer cases from the same population (p = 0.01), the 4153delA mutation made a higher contribution to ovarian cancer than to breast cancer (p < 0.01). BRCA1 mutations were significantly enriched among ovarian cancer cases with a first-degree family history of breast or ovarian cancer, whereas the median age at ovarian cancer diagnosis was not different between mutation carriers and non-carriers. Taken together, these results identify three BRCA1 founder mutations as key components of inherited breast and ovarian cancer susceptibility in Belarus and might have implications for cancer prevention, treatment and genetic counselling in this population.

Germline mutations of BRCA1 and BRCA2 genes in Turkish breast, ovarian, and prostate cancer patients

Distribution and prevalence of germline mutations in BRCA1 and BRCA2 differ among different populations. For the Turkish population, several studies have addressed high-risk breast cancer and ovarian cancer (BC-OC) patients. In most studies, both genes were analyzed in part, and a quite heterogeneous mutation spectrum was observed. For high-risk Turkish prostate cancer (PCa) patients, however, there are no data available about mutations of germline BRCA genes. To accurately determine the contribution of germline mutations in BRCA1 and BRCA2 in Turkish BC, OC, and PCa high-risk patients, 106 high-risk BC-OC patients, 50 high-risk PCa patients, and 50 control subjects were recruited. The study represents the only full screening, to date, of a large series of Turkish high-risk BC-OC patients and the only study in Turkish high-risk PCa patients. Mutation screenings were performed on coding exons of both genes with either denaturing gradient gel electrophoresis or denaturing high performance liquid chromatography, or with both techniques. Three deleterious mutations in BRCA1 and three deleterious mutations in BRCA2 were detected in different BC-OC patients, and one truncating mutation was detected in a high-risk PCa patient. In addition, 28 different unclassified and mostly novel variants were detected in both genes, as well as several silent polymorphisms. These findings reflect the genetic heterogeneity of the Turkish population and are relevant to genetic counseling and clinical management.

Irrelevance of CHEK2 variants to diagnosis of breast/ovarian cancer predisposition in Polish cohort

CHEK2 gen encodes cell cycle checkpoint kinase 2 that participates in the DNA repair pathway, cell cycle regulation and apoptosis. Mutations in CHEK2 gene may result in kinase inactivation or reduce both catalytic activity and capability of binding other proteins. Some studies indicate that alterations in CHEK2 gene confers increase the risk of breast cancer and some other malignancies, while the results of other studies are inconclusive. Thus the significance of CHEK2 mutations in aetiology of breast cancer is still debatable. The aim of our study was to evaluate the relationship between the breast/ovarian cancer and CHEK2 variants by: i) the analysis of the frequency of selected CHEK2 variants in breast and ovarian cancer patients compared to the controls; ii) evaluation of relationships between the certain CHEK2 variants and clinico-histopathological and pedigree data. The study was performed on 284 breast cancer patients, 113 ovarian cancer patients and 287 healthy women. We revealed the presence of 430T > C, del5395 and IVS2 + 1G > A variants but not 1100delC in individuals from both study and control groups. We did not observe significant differences between cancer patients and controls neither in regard to the frequency nor to the type of CHEK2 variants. We discussed the potential application of CHEK2 variants in the evaluation of breast and ovarian cancer predisposition.

On the origin and diffusion of BRCA1 c.5266dupC (5382insC) in European populations

The BRCA1 mutation c.5266dupC was originally described as a founder mutation in the Ashkenazi Jewish (AJ) population. However, this mutation is also present at appreciable frequency in several European countries, which raises intriguing questions about the origins of the mutation. We genotyped 245 carrier families from 14 different population groups (Russian, Latvian, Ukrainian, Czech, Slovak, Polish, Danish, Dutch, French, German, Italian, Greek, Brazilian and AJ) for seven microsatellite markers and confirmed that all mutation carriers share a common haplotype from a single founder individual. Using a maximum likelihood method that allows for both recombination and mutational events of marker loci, we estimated that the mutation arose some 1800 years ago in either Scandinavia or what is now northern Russia and subsequently spread to the various populations we genotyped during the following centuries, including the AJ population. Age estimates and the molecular evolution profile of the most common linked haplotype in the carrier populations studied further suggest that c.5266dupC likely entered the AJ gene pool in Poland approximately 400-500 years ago. Our results illustrate that (1) BRCA1 c.5266dupC originated from a single common ancestor and was a common European mutation long before becoming an AJ founder mutation and (2) the mutation is likely present in many additional European countries where genetic screening of BRCA1 may not yet be common practice.