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

Identification and characterization of ATM founder mutation in BRCA-negative breast cancer patients of Arab ethnicity

Breast cancer (BC) is the most prevalent malignancy among women worldwide with germline pathogenic variants/likely pathogenic variants (PVs/LPVs) in BRCA1/2 accounting for a large portion of hereditary cases. Recently, heterozygous PVs/LPVs in the ATM serine/threonine kinase or Ataxia-telangiectasia mutated gene (ATM) has been identified as a moderate susceptibility factor for BC in diverse ethnicities. However, the prevalence of ATM PVs/LPVs in BC susceptibility in Arab populations remains largely unexplored. This study investigated the prevalence of ATM PVs/LPVs among BC patients from Saudi Arabia, employing capture-sequencing technology for ATM PVs/LPVs screening in a cohort of 715 unselected BC patients without BRCA1/2 PVs/LPVs. In addition, founder mutation analysis was conducted using the PHASE program. In our entire cohort, four unique PVs/LPVs in the ATM gene were identified in six cases (0.8%). Notably, one recurrent LPV, c.6115G > A:p.Glu2039Lys was identified in three cases, for which haplotype analysis confirmed as a novel putative founder mutation traced back to 13 generations on average. This founder mutation accounted for half of all identified mutant cases and 0.4% of total screened cases. This study further reveals a significant correlation between the presence of ATM mutation and family history of BC (p = 0.0127). These findings underscore an approximate 0.8% prevalence of ATM germline PVs/LPVs in Arab BC patients without BRCA1/2 PVs/LPVs and suggest a founder effect of specific recurrent ATM mutation. These insights can help in the design of a genetic testing strategy tailored to the local population in Saudi Arabia, thereby, enabling more accurate clinical management and risk prediction.

Prevalence and clinical implications of germline mutations among Jordanian patients with ovarian cancer. The Jordanian exploratory cancer genetics ( Jo‐ECAG ) ovarian study

BACKGROUND

Ovarian cancer is one of the most common gynecological malignancies. Due to the absence of effective screening methods, ovarian cancer is usually diagnosed at late stages. Patients with pathogenic and likely-pathogenic germline variants (PGVs) in BRCA1 or BRCA2 harbor elevated risk of developing both ovarian and breast cancers. Identifying PGVs may help in both cancer prevention and active disease treatment. Worldwide prevalence of PGVs varies and the matter is poorly addressed among Arab patients.

METHODS

Patients with epithelial ovarian, fallopian tube or primary peritoneal cancers were offered the universal 20 or 84-multi-gene panel testing as per standard guidelines. Cascade family screening was also offered to all first and second-degree relatives of PGV positive patients. Genetic testing was done at a referral lab using a next generation sequencing (NGS)-based platform.

RESULTS

During the study period, 152 patients, median age (range): 50 (18-79) years old, were tested. The majority (n = 100, 65.8%) had high-grade serous carcinoma, and 106 patients (69.7%) had metastatic disease at presentation. In total, 38 (25.0%) had PGVs, while 47 (30.9%) others had variants of uncertain significance (VUS). PGVs were mostly in BRCA1 (n = 21, 13.8%) and in BRCA2 (n = 12, 7.9%), while 6 (3.9%) others had PGVs in non-BRCA1/2 genes. PGV rates were significantly higher among 15 patients with a positive family history of ovarian cancer (60.0%, p = .022) and among 52 patients with a positive family history of breast cancer (40.4%, p = .017).

CONCLUSIONS

PGVs are common among Jordanian women with ovarian cancer, and mostly occur in BRCA1/2. Given its clinical impact on disease prevention and precision therapy, universal testing should be routinely offered.

Germline variants profiling of BRCA1 and BRCA2 in Chinese Hakka breast and ovarian cancer patients

Objective

To investigate the prevalence and spectrum of BRCA1 and BRCA2 mutations in Chinese Hakka patients with breast and ovarian cancer.

Methods

A total of 1,664 breast or ovarian cancer patients were enrolled for genetic testing at our hospital. Germline mutations of the BRCA gene were analysed by next-generation sequencing, including the coding regions and exon intron boundary regions.

Results

The 1,664 patients included 1,415 (85.04%) breast cancer patients and 245 (14.72%) ovarian cancer patients, while four (0.24%) patients had both the breast and ovarian cancers. A total of 151 variants, including 71 BRCA1 variants and 80 BRCA2 variants, were detected in the 234 (14.06%) patients. The 151 variants included 58 pathogenic variants, 8 likely pathogenic variants, and 85 variants of unknown significance (VUS). A total of 56.25% (18/32) and 65.38% (17/26) of pathogenic variants (likely pathogenic variants are not included) were distributed in exon 14 of BRCA1 and exon 11 of BRCA2, respectively. The most common pathogenic variants among this Hakka population are c.2635G > T (p.Glu879*) (n = 7) in the BRCA1 gene and c.5164_5165del (p.Ser1722Tyrfs*4) (n = 7) in the BRCA2 gene among the Hakka population. A hotspot mutation in the Chinese population, the BRCA1 c.5470_5477del variant was not found in this Hakka population. The prevalence and spectrum of variants in the BRCA genes in the Hakka patients are different from that in other ethnic groups.

Conclusions

The most common pathogenic variant in this population is c.2635G > T in the BRCA1 gene, and c.5164_5165delAG in the BRCA2 gene in this population. The prevalence and spectrum of variants in the BRCA1 and BRCA2 genes in the Hakka patients from southern China are different from those in other ethnic groups.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09943-0.

The Features of BRCA1 and BRCA2 Germline Mutations in Hakka Ovarian Cancer Patients: BRCA1 C.536 A>T Maybe a Founder Mutation in This Population

Objective

To investigate the frequencies of BRCA1 and BRCA2 mutations in Chinese Hakka patients with ovarian cancer.

Methods

The protein coding regions and exon intron boundary regions of the BRCA gene were sequenced using genomic DNA isolated from the lymphocytes of patients with next-generation sequencing. The patients’ family history and clinical records were collected.

Results

A total of 195 patients with ovarian cancer were included in the study, and 52 distinct variants of the BRCA gene were identified. It was found that 64 patients (64/195, 32.8%) had BRCA gene mutations, including 32 patients (50.0%) with BRCA1 mutation, 27 patients (42.2%) with BRCA2 mutation, and 5 patients (7.8%) with both mutations. Furthermore, 22 pathogenic mutations were detected in 26 patients, 2 likely pathogenic variants in 2 patients, 12 variants of uncertain significance in 20 patients, and 16 likely benign variants in 24 patients. The mutations were mainly found to occur in exons 8, 14, and 17 of BRCA1 and exons 10, 11, 14, and 15 of BRCA2. The results showed that the BRCA genes possess different mutation hotspots in different ethnic groups. In addition, recurrent mutations were noted in many patients. BRCA1 c.536 A>T, considered a founder mutation, was identified in 10 patients (15.63%, 10/64), followed by BRCA1 c.2635 G>T (6.25%, 4/64) and BRCA2 c.2566 T>C (6.25%, 4/64).

Conclusion

The BRCA1 c.536 A>T could be considered to be a founder mutation in this ovarian cancer population. This recurrent BRCA1 mutation has rarely been observed in other ethnic groups. Our findings are expected to provide valuable data for clinical consultation and for designing individualized treatment for ovarian cancer.

Prevalence of specific and recurrent/founder pathogenic variants in BRCA genes in breast and ovarian cancer in North Africa

Background

Elucidation of specific and recurrent/founder pathogenic variants (PVs) in BRCA (BRCA1 and BRCA2) genes can make the genetic testing, for breast cancer (BC) and/or ovarian cancer (OC), affordable for developing nations.

Methods

To establish the knowledge about BRCA PVs and to determine the prevalence of the specific and recurrent/founder variants in BRCA genes in BC and/or OC women in North Africa, a systematic review was conducted in Morocco, Algeria, and Tunisia.

Results

Search of the databases yielded 25 relevant references, including eleven studies in Morocco, five in Algeria, and nine in Tunisia. Overall, 15 studies investigated both BRCA1 and BRCA2 genes, four studies examined the entire coding region of the BRCA1 gene, and six studies in which the analysis was limited to a few BRCA1 and/or BRCA2 exons. Overall, 76 PVs (44 in BRCA1 and32 in BRCA2) were identified in 196 BC and/or OC patients (129 BRCA1 and 67 BRCA2 carriers). Eighteen of the 76 (23.7%) PVs [10/44 (22.7%) in BRCA1 and 8/32 (25%) in BRCA2] were reported for the first time and considered to be novel PVs. Among those identified as unlikely to be of North African origin, the BRCA1 c.68_69del and BRCA1 c.5266dupC Jewish founder alleles and PVs that have been reported as recurrent/founder variants in European populations (ex: BRCA1 c.181T>G, BRCA1 c1016dupA). The most well characterized PVs are four in BRCA1 gene [c.211dupA (14.7%), c.798_799detTT (14%), c.5266dup (8.5%), c.5309G>T (7.8%), c.3279delC (4.7%)] and one in BRCA2 [c.1310_1313detAAGA (38.9%)]. The c.211dupA and c.5309G>T PVs were identified as specific founder variants in Tunisia and Morocco, accounting for 35.2% (19/54) and 20.4% (10/49) of total established BRCA1 PVs, respectively. c.798_799delTT variant was identified in 14% (18/129) of all BRCA1 North African carriers, suggesting a founder allele. A broad spectrum of recurrent variants including BRCA1 3279delC, BRCA1 c.5266dup and BRCA2 c.1310_1313detAAGA was detected in 42 patients. BRCA1 founder variants explain around 36.4% (47/129) of BC and outnumber BRCA2 founder variants by a ratio of ≈3:1.

Conclusions

Testing BC and/or OC patients for the panel of specific and recurrent/founder PVs might be the most cost-effective molecular diagnosis strategy.

Association between germline pathogenic variants and breast cancer risk in Japanese women: the HERPACC study

Approximately 5-10% of breast cancers are hereditary, caused by germline pathogenic variants (GPVs) in breast cancer predisposition genes. To date, most studies of the prevalence of GPVs and risk of breast cancer for each gene based on cases and non-cancer controls have been conducted in Europe and the United States, and little information from Japanese populations is available. Furthermore, no studies considered confounding by established environmental factors and single nucleotide polymorphisms (SNPs) identified in genome-wide association studies (GWAS) together in GPV evaluation. To evaluate the association between GPVs in nine established breast cancer predisposition genes including BRCA1/2 and breast cancer risk in Japanese women comprehensively, we conducted a case-control study within the Hospital-based Epidemiologic Research Program at Aichi Cancer Center (629 cases and 1153 controls). The associations between GPVs and the risk of breast cancer were assessed by odds ratios (OR) and 95% confidence intervals (CI) using logistic regression models adjusted for potential confounders. A total of 25 GPVs were detected among all cases (4.0%: 95%CI:2.6-5.9), whereas four individuals carried GPVs in all controls (0.4%). OR for breast cancer by all GPVs and by GPVs in BRCA1/2 was 12.2 (4.4-34.0, P = 1.74E-06) and 16.0 (4.2-60.9, P = 5.03E-0.5), respectively. A potential confounding with GPVs was observed for the GWAS-identified SNPs, whereas not for established environmental risk factors. In conclusion, GPVs increase the risk of breast cancer in Japanese women regardless of environmental factors and GWAS-identified SNPs. Future studies investigating interactions with environment and SNPs are warranted.

Prevalence of BRCA1 and BRCA2 pathogenic sequence variants in ovarian cancer patients in the Gulf region: the PREDICT study

BACKGROUND

Patients with pathogenic sequence variants (PSVs) in BRCA1/BRCA2 are at high risk of developing ovarian cancer (OC). However, genetic testing for BRCA1/BRCA2 PSVs is still not a routine practice in the Middle East. With the lack of epidemiological studies in the region, we aim to describe the prevalence of BRCA1/BRCA2 PSVs in patients with OC across different countries in the Gulf region.

METHODS

The PREDICT study was an observational, prospective, epidemiological study, which consecutively recruited women with ovarian, primary peritoneal, and fallopian tube cancers from the following Gulf countries over the period from July 2017 to July 2019; United Arab Emirates (UAE), Kuwait, and Oman. The study was approved by the local ethics committee of participating centers. The BRCA1/BRCA2 PSVs were assessed by tissue genetic testing using next-generation sequencing (NGS).

RESULTS

A total of 105 women were included with a median age at diagnosis of 52 years (IQR 44.5 - 61.0). Nearly 11.4% of patients reported a family history of ovarian or breast cancer, while 4.7% of patients reported a family history of other cancers. Most of the patients (70.3%) had advanced disease (FIGO stage III/IV) at presentation. Eighty-eight patients (84%) were successfully tested for somatic BRCA1/BRCA2 PSVs. Fifteen patients (17%) were found to have PSVs in either BRCA1, BRCA2, or both genes; of them, 10 patients (11.2%) had BRCA1 somatic PSVs alone, eight patients (9.1%) had BRCA2 somatic PSVs, while three patients (2.9%) had both PSVs. Five patients with BRCA1/BRCA2 somatic PSVs had germline PSVs tests, and three of them tested positive. Concerning treatment, 87.6% of patients received perioperative chemotherapy and 6.6% as first-line palliative chemotherapy. Eighty-seven (82.9%) patients underwent debulking surgery, with no residual disease in 42.5% of patients.

CONCLUSION

Our study showed that the prevalence of BRCA1/BRCA2 somatic PSVs in patients with OC is higher than the reported global figures (2-8%). However, more studies are warranted to further elucidate the prevalence of BRCA1/BRCA2 somatic and germline PSVs, as well as other relevant genetic alterations, to better understand their impact on OC patient outcomes in Gulf countries.

TRIAL REGISTRATION

NCT03082976 .

Familial/inherited cancer syndrome: a focus on the highly consanguineous Arab population

The study of hereditary cancer, which accounts for ~10% of cancer cases worldwide is an important subfield of oncology. Our understanding of hereditary cancers has greatly advanced with recent advances in sequencing technology, but as with any genetic trait, gene frequencies of cancer-associated mutations vary across populations, and most studies that have located hereditary cancer genes have been conducted on European or Asian populations. There is an urgent need to trace hereditary cancer genes across the Arab world. Hereditary disease is particularly prevalent among members of consanguineous populations, and consanguineous marriages are particularly common in the Arab world. There are also cultural and educational idiosyncrasies that differentiate Arab populations from other more thoroughly studied groups with respect to cancer awareness and treatment. Therefore, a review of the literature on hereditary cancers in this understudied population was undertaken. We report that BRCA mutations are not as prevalent among Arab breast cancer patients as they are among other ethnic groups, and therefore, other genes may play a more important role. A wide variety of germline inherited mutations that are associated with cancer are discussed, with particular attention to breast, ovarian, colorectal, prostate, and brain cancers. Finally, we describe the state of the profession of familial cancer genetic counselling in the Arab world, and the clinics and societies dedicated to its advances. We describe the complexities of genetic counselling that are specific to the Arab world. Understanding hereditary cancer is heavily dependent on understanding population-specific variations in cancer-associated gene frequencies.