Ethnicity-specific BRCA1, BRCA2, PALB2, and ATM pathogenic alleles in breast and ovarian cancer patients from the North Caucasus.

BACKGROUND: Mountain areas of the North Caucasus host several large ethnic communities that have preserved their national identity over the centuries. METHODS: This study involved high-grade serous ovarian cancer (HGSOC) and breast cancer (BC) patients from Dagestan (HGSOC: 37; BC: 198), Kabardino-Balkaria (HGSOC: 68; BC: 155), North Ossetia (HGSOC: 51; BC: 104), Chechnya (HGSOC: 68; BC: 79), Ingushetia (HGSOC: 19; BC: 103), Karachay-Cherkessia (HGSOC: 13; BC: 47), and several Armenian settlements (HGSOC: 16; BC: 101). The group of BC patients was enriched by young-onset and/or family history-positive and/or bilateral and/or receptor triple-negative cases. The entire coding region of BRCA1, BRCA2, PALB2, and ATM genes was analyzed by next-generation sequencing. RESULTS: A significant contribution of BRCA1/2 pathogenic variants (PVs) to HGSOC and BC development was observed across all North Caucasus regions (HGSOC: 19-39%; BC: 6-13%). Founder alleles were identified in all ethnic groups studied, e.g., BRCA1 c.3629_3630delAG in Chechens, BRCA2 c.6341delC in North Ossetians, BRCA2 c.5351dupA in Ingush, and BRCA1 c.2907_2910delTAAA in Karachays. Some BRCA1/2 alleles, particularly BRCA2 c.9895C > T, were shared by several nationalities. ATM PVs were detected in 14 patients, with c.1673delG and c.8876_8879delACTG alleles occurring twice each. PALB2 heterozygosity was observed in 5 subjects, with one variant seen in 2 unrelated women. CONCLUSION: This study adds to the evidence for the global-wide contribution of BRCA1/2 genes to HGSOC and BC morbidity, although the spectrum of their PVs is a subject of ethnicity-specific variations. The data on founder BRCA1/2 alleles may be considered when adjusting the BRCA1/2 testing procedure to the ethnic origin of patients.

Discrimination between Complete versus Non-Complete Pathologic Response to Neoadjuvant Therapy Using Ultrasensitive Mutation Analysis: A Proof-of-Concept Study in BRCA1-Driven Breast Cancer Patients.

Neoadjuvant chemotherapy (NACT) for breast cancer (BC) often results in pathologic complete response (pCR), i.e., the complete elimination of visible cancer cells. It is unclear whether the use of ultrasensitive genetic methods may still detect residual BC cells in complete responders. Breast carcinomas arising in BRCA1 mutation carriers almost always carry alterations of the TP53 gene thus providing an opportunity to address this question. The analysis of consecutive BC patients treated by NACT revealed a higher pCR rate in BRCA1-driven vs. BRCA1-wildtype BCs (13/24 (54%) vs. 29/192 (15%), p < 0.0001). Twelve pre-/post-NACT tissue pairs obtained from BRCA1 mutation carriers were available for the study. While TP53 mutation was identified in all chemonaive tumors, droplet digital PCR (ddPCR) analysis of the post-NACT tumor bed revealed the persistence of this alteration in all seven pCR-non-responders but in none of five pCR responders. Eleven patients provided to the study post-NACT tissue samples only; next-generation sequencing (NGS) analysis revealed mutated TP53 copies in all six cases without pCR but in none of five instances of pCR. In total, TP53 mutation was present in post-NACT tissues in all 13 cases without pCR, but in none of 10 patients with pCR (p < 0.000001). Therefore, the lack of visible tumor cells in the post-NACT tumor bed is indeed a reliable indicator of the complete elimination of transformed clones. Failure of ultrasensitive methods to identify patients with minimal residual disease among pCR responders suggests that the result of NACT is a categorical rather than continuous variable, where some patients are destined to be cured while others ultimately fail to experience tumor eradication.

Somatic loss of the remaining allele occurs approximately in half of CHEK2-driven breast cancers and is accompanied by a border-line increase of chromosomal instability.

PURPOSE: Germline mutations in CHEK2 gene represent the second most frequent cause of hereditary breast cancer (BC) after BRCA1/2 lesions. This study aimed to identify the molecular characteristics of CHEK2-driven BCs. METHODS: Loss of heterozygosity (LOH) for the remaining CHEK2 allele was examined in 50 CHEK2-driven BCs using allele-specific PCR assays for the germline mutations and analysis of surrounding single-nucleotide polymorphisms (SNPs). Paired tumor and normal DNA samples from 25 cases were subjected to next-generation sequencing analysis. RESULTS: CHEK2 LOH was detected in 28/50 (56%) BCs. LOH involved the wild-type allele in 24 BCs, mutant CHEK2 copy was deleted in 3 carcinomas, while in one case the origin of the deleted allele could not be identified. Somatic PIK3CA and TP53 mutations were present in 13/25 (52%) and 4/25 (16%) tumors, respectively. Genomic features of homologous recombination deficiency (HRD), including the HRD score ≥ 42, the predominance of BRCA-related mutational signature 3, and the high proportion of long (≥ 5 bp) indels, were observed only in 1/20 (5%) BC analyzed for chromosomal instability. Tumors with the deleted wild-type CHEK2 allele differed from LOH-negative cases by elevated HRD scores (median 23 vs. 7, p = 0.010) and higher numbers of chromosomal segments affected by copy number aberrations (p = 0.008). CONCLUSION: Somatic loss of the wild-type CHEK2 allele is observed in approximately half of CHEK2-driven BCs. Tumors without CHEK2 LOH are chromosomally stable. BCs with LOH demonstrate some signs of chromosomal instability; however, its degree is significantly lower as compared to BRCA1/2-associated cancers.

Frequency and molecular characteristics of PALB2-associated cancers in Russian patients.

PALB2 is а high-penetrance gene for hereditary breast cancer (BC). Our study aimed to investigate the spectrum of PALB2 mutations in Russian cancer patients. PALB2 sequencing revealed pathogenic variants in 3/190 (1.6%) young-onset and/or familial and/or bilateral BC cases but none in 96 ovarian cancer (OC) or 172 pancreatic cancer patients. Subsequently, seven recurrent PALB2 pathogenic alleles were selected from this and previous Slavic studies and tested in an extended patient series. PALB2 pathogenic variants were detected in 5/585 (0.9%) "high-risk" BC, 10/1508 (0.7%) consecutive BC and 5/1802 (0.3%) OC cases. Haplotyping suggested that subjects with Slavic alleles c.509-510delGA (n = 10) and c.172-175delTTGT (n = 4) as well as carriers of Finnish c.1592delT mutation (n = 4) originated from a single founder each, while PALB2 p.R414X allele (n = 4) had at least two independent founders. Somatic loss of heterozygosity (LOH) was revealed in 5/10 chemonaive BCs and in 0/2 BC samples obtained after neoadjuvant therapy. Multigene sequencing identified somatic PALB2 inactivating point mutation in one out of two tumors without PALB2 LOH but in none of four BCs with PALB2 LOH. Genomic instability, as determined by NGS, was observed in four out of five tumors with biallelic PALB2 inactivation but not in the BC sample with the preserved wild-type PALB2 allele. PALB2 germ-line mutations contribute to a small fraction of cancer cases in Russia. The majority although not all PALB2-driven BCs have somatic inactivation of the remaining PALB2 allele and therefore potential sensitivity to platinum compounds and PARP inhibitors.

Neoadjuvant therapy of BRCA1-driven ovarian cancer by combination of cisplatin, mitomycin C and doxorubicin.

BACKGROUND: Cisplatin, mitomycin C and anthracyclines demonstrate high activity in BRCA1-deficient tumors. This study aimed to evaluate the efficacy of the triplet combination of these drugs in BRCA1-driven high-grade serous ovarian carcinomas (HGSOCs). METHODS: Ten HGSOC patients with germ-line BRCA1 mutation received neoadjuvant chemotherapy (NACT) consisting of mitomycin C 10 mg/m2 (day 1), doxorubicin 30 mg/m2 (days 1 and 8) and cisplatin 80 mg/m2 (day 1), given every 4 weeks (MAP regimen). The comparator group included 16 women, who received standard NACT combination of paclitaxel 175 mg/m2 and carboplatin (6 AUC), given every 3 weeks (TCbP scheme). RESULTS: None of the patients treated by the MAP scheme demonstrated complete pathologic response in ovaries, while 4 women showed absence of tumor cells in surgically excised omental specimens. When chemotherapy response scores (CRS) were considered, poor responsiveness (CRS 1) was not observed in the MAP group, but was common for the TCbP regimen (6/16 (38 %) for ovaries and 5/16 (31 %) for omentum; p = 0.05 and 0.12, respectively). Median treatment-free interval (TFI) was not reached in women treated by the MAP, but was 9.5 months for the TCbP scheme (p = 0.1). The rate of the recurrence within 1 year after the completion of the treatment was 4/10 (40 %) for the MAP and 10/13 (77 %) for the TCbP (p = 0.1). CONCLUSIONS: The attempt to intensify NACT by administering combination of 3 drugs did not result in high rate of complete pathologic responses. However, there was a trend towards higher efficacy of the MAP regimen versus conventional TCbP scheme with regard to CRS and clinical outcomes.

Molecular profiles of BRCA1-associated ovarian cancer treated by platinum-based therapy: Analysis of primary, residual and relapsed tumors.

Our study aimed to analyze the evolution of molecular portraits of BRCA1-driven ovarian cancer (OC) during treatment. BRCA1 loss-of-heterozygosity status (LOH) and exome profiles were investigated in serial OC samples from 13 patients, which included primary tumors (n = 11) obtained before neoadjuvant therapy (NACT) or at primary debulking surgery, residual post-NACT cancer tissues (n = 13) and tumor relapses (16 samples from 13 patients). Loss of the wild-type BRCA1 allele was detected in 11/11 (100%) primary tumors, 6/13 (46%) residual post-NACT OC samples and 15/16 (94%) OC relapses. Full tumor triplets were available for four patients undergoing NACT; whereas primary carcinomas from these patients demonstrated BRCA1 LOH, the retention of the wild-type allele was detected in all four post-NACT residual tumors. These four women provided to the study 5 recurrent OC samples; 4 out of 5 tumor relapses had BRCA1 LOH thus resembling BRCA1 status observed in primary but not residual OC tissues. TP53 mutation was detected in 12 out of 13 patients and was retained across all serial samples. OC relapses tended to acquire additional intragenic mutations in genes involved in cell migration, adhesion and cell junction assembly. BRCA1-driven OCs demonstrate the plasticity of BRCA1 status during the treatment course. NACT results in rapid selection of pre-existing BRCA1-proficient cells. However, BRCA1 proficiency appears to be disadvantageous in the absence of platinum exposure, as tumor relapses usually re-acquire BRCA1 LOH during therapy holidays.

Frequency and spectrum of founder and non-founder BRCA1 and BRCA2 mutations in a large series of Russian breast cancer and ovarian cancer patients.

BACKGROUND: The spectrum of BRCA1 and BRCA2 mutations in Slavic countries is characterized by a high prevalence of founder alleles. METHODS: We analyzed a large data set of Russian breast cancer (BC) and ovarian cancer (OC) patients, who were subjected to founder mutation tests or full-length BRCA1 and BRCA2 analysis. RESULTS: The most commonly applied test, which included four founder mutations (BRCA1: 5382insC, 4153delA, 185delAG; BRCA2: 6174delT), identified BRCA1 or BRCA2 heterozygosity in 399/8533 (4.7%) consecutive BC patients, 230/2317 (9.9%) OC patients, and 30/118 (25.4%) women with a combination of BC and OC. The addition of another four recurrent BRCA1 mutations to the test (BRCA1 C61G, 2080delA, 3819del5, 3875del4) resulted in evident increase in the number of identified mutation carriers (BC: 16/993 (1.6%); OC: 34/1289 (2.6%); BC + OC: 2/39 (5.1%)). Full-length sequencing of the entire BRCA1 and BRCA2 coding region was applied to 785 women, very most of whom demonstrated clinical signs of BRCA-driven disease, but turned out negative for all described above founder alleles. This analysis revealed additional BRCA1 or BRCA2 mutation carriers in 54/282 (19.1%) BC, 50/472 (10.6%) OC, and 13/31 (42%) BC + OC patients. The analysis of frequencies of founder and "rare" BRCA1 and BRCA2 pathogenic alleles across various clinical subgroups (BC vs. OC vs. BC + OC; family history positive vs. negative; young vs. late-onset; none vs. single vs. multiple clinical indicators of BRCA1- or BRCA2-associated disease) revealed that comprehensive BRCA1 and BRCA2 analysis increased more than twice the number of identified mutation carriers in all categories of the examined women. CONCLUSION: Full-length BRCA1 and BRCA2 sequencing is strongly advised to Slavic subjects, who have medical indications for BRCA1 and BRCA2 testing but are negative for recurrent BRCA1 and BRCA2 mutations.

Exome sequencing study of Russian breast cancer patients suggests a predisposing role for USP39.

PURPOSE: Germline variants in known breast cancer (BC) predisposing genes explain less than half of hereditary BC cases. This study aimed to identify missing genetic determinants of BC. METHODS: Whole exome sequencing (WES) of lymphocyte DNA was performed for 49 Russian patients with clinical signs of genetic BC predisposition, who lacked Slavic founder mutations in BRCA1, BRCA2, CHEK2, and NBS1 genes. RESULTS: Bioinformatic analysis of WES data was allowed to compile a list of 229 candidate mutations. 79 of these mutations were subjected to a three-stage case-control analysis. The initial two stages, which involved up to 797 high-risk BC patients, 1504 consecutive BC cases, and 1081 healthy women, indicated a potentially BC-predisposing role for 6 candidates, i.e., USP39 c.*208G > C, PZP p.Arg680Ter, LEPREL1 p.Pro636Ser, SLIT3 p.Arg154Cys, CREB3 p.Lys157Glu, and ING1 p.Pro319Leu. USP39 c.*208G > C was strongly associated with triple-negative breast tumors (p = 0.0001). In the third replication stage, we genotyped the truncating variant of PZP (rs145240281) and the potential splice variant of USP39 (rs112653307) in three independent cohorts of Russian, Byelorussian, and German ancestry, comprising a total of 3216 cases and 2525 controls. The data obtained for USP39 rs112653307 supported the association identified in the initial stages (the combined OR 1.72, p = 0.035). CONCLUSIONS: This study suggests the role of a rare splicing variant in BC susceptibility. USP39 encodes an ubiquitin-specific peptidase that regulates cancer-relevant tumor suppressors including CHEK2. Further epidemiological and functional studies involving these gene variants are warranted.

Next generation sequencing analysis of consecutive Russian patients with clinical suspicion of inborn errors of immunity.

Primary immune deficiencies are usually attributed to genetic defects and, therefore, frequently referred to as inborn errors of immunity (IEI). We subjected the genomic DNA of 333 patients with clinical signs of IEI to next generation sequencing (NGS) analysis of 344 immunity-related genes and, in some instances, additional genetic techniques. Genetic causes of the disease were identified in 69/333 (21%) of subjects, including 11/18 (61%) of children with syndrome-associated IEIs, 45/202 (22%) of nonsyndromic patients with Jeffrey Modell Foundation (JMF) warning signs, 9/56 (16%) of subjects with periodic fever, 3/30 (10%) of cases of autoimmune cytopenia, 1/21 (5%) of patients with unusually severe infections and 0/6 (0%) of individuals with isolated elevation of IgE level. There were unusual clinical observations: twins with severe immunodeficiency carried a de novo CHARGE syndrome-associated SEMA3E c.2108C>T (p.S703L) allele; however, they lacked clinical features of CHARGE syndrome. Additionally, there were genetically proven instances of Netherton syndrome, Х-linked agammaglobulinemia, severe combined immune deficiency (SCID), IPEX and APECED syndromes, among others. Some patients carried recurrent pathogenic alleles, such as AIRE c.769C>T (p.R257*), NBN c.657del5, DCLRE1C c.103C>G (p.H35D), NLRP12 c.1054C>T (p.R352C) and c.910C>T (p.H304Y). NGS is a powerful tool for high-throughput examination of patients with malfunction of immunity.

Mitomycin C plus cisplatin for systemic treatment of recurrent BRCA1-associated ovarian cancer.

Background Previous studies on neoadjuvant therapy for BRCA1-driven ovarian cancer (OC) demonstrated higher efficacy of mitomycin C plus cisplatin combination as compared to standard drug schemes. These data call for evaluation of the utility of this regimen for the treatment of recurrent BRCA1-associated OC. Methods The study included 12 BRCA1 germ-line mutation carriers, whose disease relapsed after one (n = 4) or two (n = 8) lines of chemotherapy. The patients received cisplatin 100 mg/m2 and mitomycin C 10 mg/m2, given every four weeks, for 6 (n = 10), 8 (n = 1) or 5 (n = 1) cycles. Retrospective data on conventional treatment of OC relapses in BRCA1 heterozygotes (n = 47) served as a control. Results Grade 3-4 toxicities were observed in 4/12 (33%) cases. There were 6 complete responses (CR), 4 partial responses (PR) and 2 instances of stable disease (SD). Comparison of patients receiving mitomycin C plus cisplatin (n = 4) or conventional therapy (n = 44) at first relapse demonstrated marginal improvement of the progression-free survival (PFS) (16.6 months vs. 10.2 months, P = .067). Use of mitomycin C plus cisplatin (n = 8) for the treatment of second relapse resulted in significant prolongation of PFS as compared to standard regimens (n = 31) (14.8 months vs. 4.8 months, P = .002). Conclusions Mitomycin C plus cisplatin shows promising activity in recurrent BRCA1-driven ovarian cancer.

Gastric Cancer in BRCA1 Germline Mutation Carriers: Results of Endoscopic Screening and Molecular Analysis of Tumor Tissues.

INTRODUCTION: There is some evidence suggesting a link between BRCA1/2 germline mutations and increased risk of gastric cancer. METHODS: Endoscopic screening for stomach malignancies was performed in 120 BRCA1 mutation carriers in order to evaluate the probability of detecting the tumor disease. RESULTS: No instances of gastric cancer were revealed at the first visit. The analysis of atrophic changes performed by OLGA (Operative Link for Gastritis Assessment) criteria revealed that OLGA stages I-IV alterations were observed in 26 of 41 (63%) subjects aged >50 years as compared to 29 of 79 (37%) in younger subjects (p = 0.007, χ2 test). One BRCA1 mutation carrier developed gastric cancer 4 years after the first visit for endoscopic examination. We performed next-generation sequencing analysis for this tumor and additional 4 archival gastric cancers obtained from BRCA1/2 mutation carriers. Somatic loss of the remaining BRCA1/2 allele was observed in 3 out of 5 tumors analyzed; all of these carcinomas, but none of the malignancies with the retained BRCA1/2 copy, showed chromosomal instability. CONCLUSION: Taken together, these data justify further studies on the relationships between the BRCA1/2 and gastric cancer.

Pattern of TSC1 and TSC2 germline mutations in Russian patients with tuberous sclerosis.

Tuberous sclerosis (TS) is a rare autosomal-dominant genetic disease. TS is manifested by the development of multiple hamartomas, which affect brain, kidneys, retina, skin and other organs. This study aimed to reveal specific features of molecular epidemiology of TS in Russia. Blood DNA samples from 61 patients with definite (n = 53) or probable (n = 8) clinical diagnosis of TS were tested for mutations in TSC1 and TSC2 genes using Sanger sequencing and MLPA analysis. Five TSC1/2 mutation-negative patients were further analyzed by exome sequencing. TSC1/2 mutations were detected in 53/61 patients (87%): 39 (74%) carried mutations in the TSC2 and 14 (26%) in the TSC1. Large rearrangements (exon deletions/duplications) affected exclusively TSC2, accounting for 15% of lesions of this gene. 6/8 (75%) patients with incomplete clinical manifestation of TS carried TSC1/2 gene lesion. Overall, 96% of detected germline TSC1/2 mutations occurred de novo. Patients with no mutation identified (NMI) differed from TSC1/2 mutation carriers, being lacking cortical tubers and subependymal nodules but having higher frequencies of renal angiomyolipomas, rhabdomyomas, and lymphangioleiomyomatosis. Exome sequencing failed to identify overt disease-causing mutation candidates among NMI patients. Russian patients with TS have increased frequency of TSC2 large gene rearrangements and TSC1/2 mutations occurring de novo as compared to other studies. Patients with suspected TS diagnosis but NMI status may represent a distinct disease entity.

Efficacy of Neoadjuvant Therapy With Cisplatin Plus Mitomycin C in BRCA1-Mutated Ovarian Cancer.

OBJECTIVES: Cisplatin and mitomycin C exert high activity towards BRCA1-deficient cells. This study aimed to evaluate the efficacy of a combination of these drugs in hereditary BRCA1-associated ovarian cancer (OC). METHODS: Twelve OC patients, who could not be treated by primary debulking surgery owing to extensive tumor spread, were given neoadjuvant cisplatin (100 mg/m) and mitomycin C (10 mg/m) every 4 weeks for 3 (n = 9), 2 (n = 2), or 4 (n = 1) cycles. RESULTS: The decrease of tumor burden and complete surgical cytoreduction were achieved in all patients. Pathologic complete response, defined as the absence of tumor cells in surgically removed tissues, was observed in 2 (17%) of 12 cases. Retrospective analysis of 62 OC in BRCA1 mutation carriers subjected to conventional neoadjuvant chemotherapy schemes revealed 36 objective tumor responses (58%) and 37 instances (60%) of complete cytoreductive surgery; however, none of these patients demonstrated pathologic complete response. CONCLUSIONS: The combination of cisplatin plus mitomycin C showed promising results in BRCA1-driven OC and therefore deserves further clinical evaluation.

Multigene sequencing reveals heterogeneity of NLRP12-related autoinflammatory disorders.

NLRP12-related autoinflammatory disease (NLRP12-AID) is an exceptionally rare autosomal dominant disorder caused by germline mutations in NLRP12 gene. Very few patients with NLRP12-AD have been identified worldwide; therefore, there is a scarcity of data on phenotypic presentation of this syndrome. Here we provide evidence that NLRP12-AID may have clinical manifestations characteristic for primary immune deficiencies (PID). 246 children with periodic fever (PF) of unknown origin were subjects to the next generation sequencing (NGS) analysis; 213 of these patients had signs of primary immunodeficiency (PID) manifested by recurrent infections, while 33 kids had isolated PF. The NGS panel was composed of 302 genes implicated in PID and/or AID. 15 patients (9 girls and 6 boys) with NLRP12-AID were identified. Median age of first AID-related fever episode was 12 months, ranging from 2 months to 13 years. Main clinical features of NLRP12-related AID were periodic fever (100%), abdominal pain and diarrhea (47%), arthralgia (20%), headache (20%) and failure to thrive (33%). Nine patients demonstrated increased susceptibility to infection and two children suffered from Crohn's disease. Administration of short courses of NSAID or corticosteroids resulted in resolution of the disease flare. In one severe case, canakinumab (anti-interleukin-1ß antibody) was successfully used. Significant number of patients with genetically assigned diagnosis of NLPR12-AID has clinical features which close resemble primary immune deficiency. This phenotypic overlap may result in underdiagnosis of NLPR12-AID among patients with PID.

Detection of BRCA1 gross rearrangements by droplet digital PCR.

PURPOSE: Large genomic rearrangements (LGRs) constitute a significant share of pathogenic BRCA1 mutations. Multiplex ligation-dependent probe amplification (MLPA) is a leading method for LGR detection; however, it is entirely based on the use of commercial kits, includes relatively time-consuming hybridization step, and is not convenient for large-scale screening of recurrent LGRs. MATERIALS AND METHODS: We developed and validated the droplet digital PCR (ddPCR) assay, which covers the entire coding region of BRCA1 gene and is capable to precisely quantitate the copy number for each exon. RESULTS: 141 breast cancer (BC) patients, who demonstrated evident clinical features of hereditary BC but turned out to be negative for founder BRCA1/2 mutations, were subjected to the LGR analysis. Four patients with LGR were identified, with three cases of exon 8 deletion and one women carrying the deletion of exons 5-7. Excellent concordance with MLPA test was observed. Exon 8 copy number was tested in additional 720 BC and 184 ovarian cancer (OC) high-risk patients, and another four cases with the deletion were revealed; MLPA re-analysis demonstrated that exon 8 loss was a part of a larger genetic alteration in two cases, while the remaining two patients had isolated defect of exon 8. Long-range PCR and next generation sequencing of DNA samples carrying exon 8 deletion revealed two types of recurrent LGRs. CONCLUSION: Droplet digital PCR is a reliable tool for the detection of large genomic rearrangements.

Evidence for a pathogenic role of BRCA1 L1705P and W1837X germ-line mutations.

BRCA1 L1705P (c.5114T>C) has been classified in the NCBI SNP database as the variant with uncertain significance and is absent in major BRCA1 databases. BRCA1 W1837X (c.5511G>A) results in a loss of only last 27 residues of BRCA1 protein, thus its pathogenic role still requires a confirmation. This report describes two breast cancer (BC) patients carrying BRCA1 L1705P and W1837X germ-line mutations, respectively. Significant evidence for BC-predisposing impact of the mentioned mutations have been obtained: (1) both index cases presented with the triple-negative receptor status of BC disease; (2) complete segregation with BRCA1-related cancers was observed in the families of these patients; (3) somatic loss of the remaining (wild-type) BRCA1 allele was detected in tumor tissues of the affected women. The results of this study have to be taken into account while providing genetic counseling to cancer patients and while considering the use of BRCA1-specific therapeutic compounds for BC treatment.

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.

Breast cancer sensitivity to neoadjuvant therapy in BRCA1 and CHEK2 mutation carriers and non-carriers.

Breast carcinomas caused by inheritance of cancer-predisposing germ-line mutations have specific bioclinical features. This study aimed to analyze the efficacy of conventional cytotoxic treatment in BRCA1 and CHEK2 mutation carriers and non-carriers. The study included 415 Russian breast cancer patients aged 50 years or younger, who were subjected to various standard schemes of neoadjuvant therapy. The choice of therapy was done without the knowledge of the mutations status, because DNA testing was performed retrospectively using the archival tissue samples. 19 BRCA1 (4.6%) and 8 CHEK2 (1.9%) heterozygous genotypes were identified. BRCA1 mutation carriers achieved pathological complete response more frequently than non-carriers [6/19 (31.6%) vs. 46/388 (11.9%), p = 0.024]; this effect was limited to women treated by anthracycline-based therapy without taxanes [5/9 (55.6%) vs. 28/247 (11.3%), p = 0.002] and was not observed in any of 7 BRCA1 carriers receiving taxane-containing regimens. CHEK2 heterozygotes did not experience pathological complete response and showed lower frequency of objective clinical responses as compared to mutation non-carriers [4/8 (50%) vs. 333/388 (85.5%), p = 0.020]; the efficacy of neoadjuvant therapy was particularly poor in CHEK2 carriers receiving anthracyclines without taxanes. This study provides evidence for distinct sensitivity of BRCA1 and CHEK2 mutation-driven breast carcinomas to standard chemotherapeutic schemes.