Prevalence of BRCA1 and BRCA2 germline variants in an unselected pancreatic cancer patient cohort in Pakistan.

BACKGROUND: BRCA1 and BRCA2 (BRCA1/2) are the most frequently investigated genes among Caucasian pancreatic cancer patients, whereas limited reports are available among Asians. We aimed to investigate the prevalence of BRCA1/2 germline variants in Pakistani pancreatic cancer patients. METHODS: One hundred and fifty unselected and prospectively enrolled pancreatic cancer patients were comprehensively screened for BRCA1/2 germline variants using denaturing high-performance liquid chromatography and high-resolution melting analyses, followed by DNA sequencing of the variant fragments. The novel variants were analyzed for their pathogenic effect using in-silico tools. Potentially functional variants were further screened in 200 cancer-free controls. RESULTS: Protein truncating variant was detected in BRCA2 only, with a prevalence of 0.7% (1/150). A frameshift BRCA2 variant (p.Asp946Ilefs*14) was identified in a 71-year-old male patient of Pathan ethnicity, with a family history of abdominal cancer. Additionally, we found a novel variant in BRCA2 (p.Glu2650Gln), two previously reported variants in BRCA1 (p.Thr293Ser) and BRCA2 (p.Ile2296Leu) and a recurrent nonsense variant in BRCA2 (p.Lys3326Ter). These variants were classified as variants of uncertain significance (VUS). It is noteworthy that none of these VUS carriers had a family history of pancreatic or other cancers. CONCLUSIONS: In this first study, BRCA1/2 pathogenic variant is identified with a low frequency in pancreatic cancer patients from Pakistan. Comprehensive multigene panel testing is recommended in the Pakistani pancreatic cancer patients to enhance genetic understanding in this population.

Contribution of germline PALB2 variants to an unselected and prospectively registered pancreatic cancer patient cohort in Pakistan.

BACKGROUND: Partner and localizer of BRCA2 (PALB2) is a pancreatic cancer (PC) susceptibility gene reported in Caucasians. However, limited data are available among Asians. We investigated the contribution of PALB2 germline variants to Pakistani PC patients. METHODS: 150 unselected and prospectively enrolled PC patients were comprehensively screened for PALB2 variants, using denaturing high-performance liquid chromatography and DNA sequencing. Novel variants were investigated for their pathogenic effect using in-silico tools. Potentially functional variants were screened in 200 controls. RESULTS: Twenty-two different PALB2 variants were identified. A missense variant (p.Arg37His) was identified in a 48-years-old male patient with a family history of breast cancer. Another missense variant (p.Trp898Arg) was identified in a 48-years-old male patient with a family history of esophageal cancer. A novel 3' downstream variant (c.∗480A>G) was detected in a 34-years-old female patient with family history of lung cancer. Another novel 3' downstream variant (c.∗417A>C) was identified in a 41-years-old male patient. All these variants were absent in 200 controls. p.Arg37His and p.Trp898Arg were predicted as likely pathogenic. c.∗417A>C and c.∗480A>G were classified as variants of uncertain significance. CONCLUSION: This is the first study that suggests a minimal contribution of PALB2 variants to PC risk in Pakistani population.

Chasing the origin of 23 recurrent BRCA1 mutations in Pakistani breast and ovarian cancer patients.

Knowledge of population specific BRCA1/2 founder mutations provides a valuable and cost-effective genetic testing strategy. Twenty-three recurrent BRCA1 mutations have been identified previously in 100 Pakistani breast and/or ovarian cancer families. These accounted for 72.5% of all BRCA1 mutations identified. In our study, we investigated whether these mutations (identified in ≥2 unrelated patients) have a common ancestral origin and estimated the ages of these mutations. Haplotype analyses were performed in 188 individuals (100 index patients, 88 relatives) from Pakistani breast/ovarian cancer families, all harboring one of the 23 recurrent BRCA1 mutations, and 90 healthy controls. Six microsatellite markers (D17S800, D17S1801, D17S855, D17S1322, D17S1323, and D17S951) were analyzed. Mutation ages were estimated using DMLE+2.3 software. An identical haplotype of different length was found in families harboring the same BRCA1 mutation and suggested founder effects for all 23 mutations. Sixteen founder mutations were ethnicity-specific: 15 occurred in families of Punjabi background and one in a family of Pathan background. The remaining seven mutations occurred in families with two ethnic backgrounds. All BRCA1 founder mutations were estimated to have arisen approximately 147 to 159 generations ago. Our findings suggest founder effects for all 23 recurrent BRCA1 mutations. This knowledge allows the design and development of a cost effective local genetic testing strategy in Pakistan.

Prevalence of RECQL germline variants in Pakistani early-onset and familial breast cancer patients.

BACKGROUND: The RecQ Like Helicase (RECQL) gene has previously been shown to predispose to breast cancer mainly in European populations, in particular to estrogen receptor (ER) and/or progesterone receptor (PR) positive tumor. Here, we investigated the contribution of pathogenic RECQL germline variants to hereditary breast cancer in early-onset and familial breast cancer patients from Pakistan. METHODS: Comprehensive RECQL variant analysis was performed in 302 BRCA1 and BRCA2 negative patients with ER and/or PR positive breast tumors using denaturing high-performance liquid chromatography followed by DNA sequencing. Novel variants were classified using Sherloc guidelines. RESULTS: One novel pathogenic protein-truncating variant (p.W75*) was identified in a 37-year-old familial breast cancer patient. The pathogenic variant frequencies were 0.3% (1/302) in early-onset and familial breast cancer patients and 0.8% (1/133) in familial patients. Further, three novel variants of unknown significance, p.I141F, p.S182S, and p.C475C, were identified in familial breast cancer patients at the age of 47, 68, and 47 respectively. All variants were absent in 250 controls. CONCLUSIONS: Our data suggest that the RECQL gene plays a negligible role in breast cancer predisposition in Pakistan.

Absence of the TRIP13 c.1060C>T Mutation in Wilms Tumor Patients From Pakistan.

BACKGROUND AND AIM: Wilms tumor (WT) is the most common childhood malignant renal tumor. Germline mutations in several WT predisposition genes have been identified. However, the fundamental cause of most WT patients remains unexplained. Recently, a founder mutation, c.1060C>T (p. Arg254X) in a mitotic spindle checkpoint gene, TRIP13, was reported in 5 unrelated children with WT from the United Kingdom, of Pakistani descent from Azad Kashmir region. This observation suggests other children with WT in Pakistan may also harbor this mutation. We conducted the first study to assess the contribution of TRIP13 c.1060C>T mutation to WT in Pakistan. MATERIALS AND METHODS: Constitutional genomic DNA from 68 Pakistani individuals including unrelated WT cases (n=26) and one (n=10) or both (n=32) of their parent(s) were screened for the TRIP13 c.1060C>T mutation using DNA sequence analysis. We also included positive controls in the analyses. RESULTS: The median age of WT diagnosis was 3.0 years (range, 0.75 to 10). The TRIP13 c.1060C>T mutation was not found in any WT patient (n=26) or their parents (n=42). Twenty-four patients (92.4%) presented with unilateral tumor and 2 patients (7.7%) were diagnosed with synchronous bilateral WT. Thirteen patients (50%) reported parental consanguinity. Thirteen patients (50.0%) belonged to the Punjabi ethnicity and 1 patient (3.8%) had a Kashmiri background. Four patients (16.7%) reported a family history of WT or other malignancies. The predominant histologic subtype was stromal (46.2%). The majority of patients presented with >5 cm of tumor size (81%). None of the patients had a personal or family history of congenital anomalies, or associated genetic syndromes. CONCLUSIONS: Our findings suggest that TRIP13 c.1060C>T mutation may be infrequent in Pakistani WT cases. Further evaluation of this mutation in a large number of WT patients of Kashmiri heritage and various ethnic backgrounds from Pakistan is warranted.

Prevalence and spectrum of MLH1, MSH2, and MSH6 pathogenic germline variants in Pakistani colorectal cancer patients.

BACKGROUND: Pathogenic germline variants in MLH1, MSH2 and MSH6 genes account for the majority of Lynch syndrome (LS). In this first report from Pakistan, we investigated the prevalence of pathogenic MLH1/MSH2/MSH6 variants in colorectal cancer (CRC) patients. METHODS: Consecutive cases (n = 212) were recruited at the Shaukat Khanum Memorial Cancer Hospital and Research Centre (SKMCH&RC), between November 2007 to March 2011. Patients with a family history of > 3 or 2 HNPCC-associated cancers were classified as HNPCC (n = 9) or suspected-HNPCC (n = 20), respectively (group 1; n = 29). Cases with no family history were designated as non-HNPCC (group 2; n = 183). MLH1/MSH2/MSH6 genes were comprehensively screened in group 1. Pathogenic/likely pathogenic variants identified in group 1 were subsequently evaluated in group 2. RESULTS: Eight distinct pathogenic/likely pathogenic MLH1/MSH2 variants were found in group 1 (10/29; 34.5%), belonging to HNPCC (5/9; 55.6%) and suspected-HNPCC (5/20; 25%) families and in group 2 (2/183; 1.1%) belonging to non-HNPCC. Overall, three recurrent variants (MSH2 c.943-1G > C, MLH1 c.1358dup and c.2041G > A) accounted for 58.3% (7/12) of all families harboring pathogenic/likely pathogenic MLH1/MSH2 variants. Pathogenic MSH6 variants were not detected. CONCLUSION: Pathogenic/likely pathogenic MLH1/MSH2 variants account for a substantial proportion of CRC patients with HNPCC/suspected-HNPCC in Pakistan. Our findings suggest that HNPCC/suspected-HNPCC families should be tested for these recurrent variants prior to comprehensive gene screening in this population.

Spectrum and prevalence of BRCA1/2 germline mutations in Pakistani breast cancer patients: results from a large comprehensive study.

BACKGROUND: Pathogenic germline mutations in BRCA1 and BRCA2 (BRCA1/2) account for the majority of hereditary breast and/or ovarian cancers worldwide. To refine the spectrum of BRCA1/2 mutations and to accurately estimate the prevalence of mutation in the Pakistani population, we studied 539 breast cancer patients selected for family history and age of diagnosis. METHODS: Comprehensive screening for BRCA1/2 germline mutations was performed using state-of-the-art technologies. RESULTS: A total of 133 deleterious mutations were identified in 539 families (24.7%), comprising 110 in BRCA1 and 23 in BRCA2. The prevalence of BRCA1/2 small-range mutations and large genomic rearrangements was 55.4% (36/65) for families with breast and ovarian cancer, 27.4% (67/244) for families with two or more cases of breast cancer, 18.5% (5/27) for families with male breast cancer, and 12.3% (25/203) for families with a single case of early-onset breast cancer. Nine mutations were specific to the Pakistani population. Eighteen mutations in BRCA1 and three in BRCA2 were recurrent and accounted for 68.2% (75/110) and 34.8% (8/23) of all identified mutations in BRCA1 and BRCA2, respectively. Most of these mutations were exclusive to a specific ethnic group and may result from founder effects. CONCLUSIONS: Our findings show that BRCA1/2 mutations account for one in four cases of hereditary breast/ovarian cancer, one in five cases of male breast cancer, and one in eight cases of early-onset breast cancer in Pakistan. Our study suggests genetic testing of an extended panel of 21 recurrent BRCA1/2 mutations for appropriately selected patients and their families in Pakistan.

A novel deleterious c.2656G>T MSH2 germline mutation in a Pakistani family with a phenotypic overlap of hereditary breast and ovarian cancer and Lynch syndrome.

BACKGROUND: Hereditary breast and ovarian cancer syndrome (HBOC) and Lynch syndrome (LS) account for a significant proportion of inherited gynecologic malignancies, mainly caused by pathogenic germline mutations in the BRCA1 and BRCA2 genes or in mismatch repair (MMR) genes, such as MLH1 and MSH2. Women harboring deleterious mutations in these genes have increased life-time risks of developing a number of malignancies including ovarian cancer. Since there is a phenotypic overlap of HBOC and LS, timely identification of individuals at-risk of a particular syndrome is crucial in order to optimize cancer risk management. CASE PRESENTATION: We report a novel pathogenic MSH2 mutation, c.2656G > T, which was identified in a 67-year-old female patient with breast cancer, who had previously tested negative for a deleterious mutation in the breast cancer susceptibility genes BRCA1, BRCA2, CHEK2 or RAD51C. The patient reported a personal history of endometrial cancer diagnosed at age 48, and a strong family history of breast and ovarian cancer, as well as several other malignancies within the spectrum of LS. The novel mutation was also found in the index patient's daughter and a niece, who were diagnosed with endometrial and ovarian cancer, respectively. Breast and endometrial tumors from c.2656G > T mutation carriers showed loss of MSH2 and MSH6 protein expression. The mutation was absent in the control population. CONCLUSIONS: Our finding suggests that testing for MMR genes may be of benefit to BRCA1/2 negative families with overlapping HBOC and LS phenotype in Pakistan. It is clinically significant to identify individuals harboring mutations in genes linked with a particular syndrome so that they can benefit from targeted life-saving cancer surveillance and preventive strategies.