Correspondence
Should a BRCA2 Stop Codon Human Variant, Usually Considered a Polymorphism, Be Classified as a Predisposing Mutation? Germline mutations in the tumor suppressor genes BRCA1 and BRCA2 can increase the risk of breast and/or ovarian cancer up to 20-fold.1 Hundreds of different BRCA2 sequence variations, including causative mutations, polymorphisms, and variants of uncertain significance, are annotated in the Breast Cancer Information Core (BIC) database (research.nhgri.nih.gov/ bic/). The correct interpretation of the significance of variants (ie, the ability to discriminate between disease predisposing/causing and neutral/benign variants) still remains a challenge, and occasionally opposite effects have been found to be related to the same nucleotide sequence change. During our routine screening for germline cancer predisposing mutations in the BRCA1/BRCA2 genes, we analyzed a patient with a history of 2 primary breast cancers and a cluster of tumors within the family. In particular, the patient had 6 brothers. Three of them had been affected by a single neoplasia: one was diagnosed with lung cancer at age 53 years, one was diagnosed with bladder cancer at age 78 years, and the third was diagnosed with throat cancer at age 72 years. Two other brothers had been affected by 2 primary cancers each: one was diagnosed with esophageal and lung cancers at ages 65 years and 71 years, respectively (and was still alive at the time of last follow-up), and the other was diagnosed with jaw and bladder cancers at the ages of 52 years and 60 years, respectively. The other 4 brothers died as a consequence of their disease. The sixth brother (aged 60 years at the time of last follow-up) has a negative history for cancer, although his daughter died of brain cancer at age 4 years. Moreover, an uncle of the patient died of lung cancer. Finally, the daughter of the brother affected by bladder cancer has a history of ovarian cancer diagnosed at age 35 years and recently was diagnosed with rectal cancer with hepatic lesions at the age of 56 years. K3326X, a polymorphic stop codon in the coding region of BRCA2, was first described as a polymorphism Cancer
Month 00, 2014
that does not increase susceptibility to breast cancer; however, its frequency was found to be < 1% in both controls and patients with breast cancer.2 A subsequent study demonstrated that deletion of the BRCA2 COOH terminus renders mouse cells hypersensitive to ionizing radiation and rapidly senescent, which is consistent with the hypothesis of defective MmRad51-mediated DNA repair.3 In addition, although K3326X appears to be unrelated to breast cancer susceptibility, several studies have suggested that it may increase the risk of other oncological diseases. In fact, the K3326X polymorphic stop codon, in the compound heterozygous state, has been associated with the onset of Fanconi anemia, a rare autosomal recessive cancer susceptibility syndrome that appears to be related to a BRCA2 mutation that disrupts the protein’s COOH terminus.4 Subsequently, the frequency of K3326X was found to be higher in patients with familial pancreatic cancer, lung cancer, and esophageal squamous cell carcinoma compared with control populations.5-7 Although our patient’s history strongly suggested the presence of familial neoplasias, the molecular analysis of BRCA1 and BRCA2 did not identify any previously defined causative mutation. Instead, it revealed the BRCA2 K3326X variant, which causes a premature stop codon and the loss of 93 amino acids at the protein’s C-terminus.2 We identified the K3326X variant in only 1 allele of 200 patients with breast cancer who were analyzed, which corresponds to a frequency of 0.25%. The case report described herein supports the heterogeneity of cancer types associated with a predisposing mutation, thereby suggesting that more complex pathogenetic mechanisms are related to BRCA2 variants than previously believed. Given the above-mentioned reports and our patient’s genotype and family history, caution should be exerted in considering BRCA2 K3326X as merely a benign polymorphism, as codified in the BIC database; rather, we believe this opens the debate that it may be considered a pathogenetic variant. FUNDING SUPPORT Supported by grant PS 35-126/Ind and grant PON01_02589 (MICROMAP) 2012 from the Ministry of University and Research (both to Dr. Salvatore) and grant RF-2010-2318372 from the Ministry of Health (to Dr. Salvatore).
CONFLICT OF INTEREST DISCLOSURES The authors made no disclosures. 1
Correspondence
REFERENCES 1. Lalloo F, Evans DG. Familial breast cancer. Clin Genet. 2012;82: 105-114. 2. Mazoyer S, Dunning AM, Serova O, et al. A polymorphic stop codon in BRCA2. Nat Genet. 1996;14:253-254. 3. Morimatsu M, Donoho G, Hasty P. Cells deleted for Brca2 COOH terminus exhibit hypersensitivity to gamma-radiation and premature senescence. Cancer Res. 1998;58:3441-3447. 4. Howlett NG, Taniguchi T, Olson S, et al. Biallelic inactivation of BRCA2 in Fanconi anemia. Science. 2002;297:606-609. 5. Martin ST, Matsubayashi H, Rogers CD, et al. Increased prevalence of the BRCA2 polymorphic stop codon K3326X among individuals with familial pancreatic cancer. Oncogene. 2005;24: 3652-3656. 6. Rudd MF, Webb EL, Matakidou A, et al. Variants in the GH-IGF axis confer susceptibility to lung cancer. Genome Res. 2006;16: 693-701.
2
7. Akbari MR, Malekzadeh R, Nasrollahzadeh D, et al. Germline BRCA2 mutations and the risk of esophageal squamous cell carcinoma. Oncogene. 2008;27:1290-1296.
Valeria D’Argenio, MD1,2 Maria Valeria Esposito, MS1,2 Jean Ann Gilder1,3 Giulia Frisso, MD, PhD1,2 Francesco Salvatore, MD, PhD1,2,4 1 CEINGE-Biotecnologie Avanzate, Naples, Italy Department of Molecular Medicine and Medical Biotechnologies, University of Naples Federico II Naples, Italy 3 Scientific Communication Srl, Naples, Italy 4 IRCCS-Fondazione SDN, Naples, Italy
2
DOI: 10.1002/cncr.28605, Published online Month 00, 2014 in Wiley Online Library (wileyonlinelibrary.com)
Cancer
Month 00, 2014
Should a BRCA2 Stop Codon Human Variant, Usually Considered a Polymorphism, Be Classified as a Predisposing Mutation? Germline mutations in the tumor suppressor genes BRCA1 and BRCA2 can increase the risk of breast and/or ovarian cancer up to 20-fold.1 Hundreds of different BRCA2 sequence variations, including causative mutations, polymorphisms, and variants of uncertain significance, are annotated in the Breast Cancer Information Core (BIC) database (research.nhgri.nih.gov/ bic/). The correct interpretation of the significance of variants (ie, the ability to discriminate between disease predisposing/causing and neutral/benign variants) still remains a challenge, and occasionally opposite effects have been found to be related to the same nucleotide sequence change. During our routine screening for germline cancer predisposing mutations in the BRCA1/BRCA2 genes, we analyzed a patient with a history of 2 primary breast cancers and a cluster of tumors within the family. In particular, the patient had 6 brothers. Three of them had been affected by a single neoplasia: one was diagnosed with lung cancer at age 53 years, one was diagnosed with bladder cancer at age 78 years, and the third was diagnosed with throat cancer at age 72 years. Two other brothers had been affected by 2 primary cancers each: one was diagnosed with esophageal and lung cancers at ages 65 years and 71 years, respectively (and was still alive at the time of last follow-up), and the other was diagnosed with jaw and bladder cancers at the ages of 52 years and 60 years, respectively. The other 4 brothers died as a consequence of their disease. The sixth brother (aged 60 years at the time of last follow-up) has a negative history for cancer, although his daughter died of brain cancer at age 4 years. Moreover, an uncle of the patient died of lung cancer. Finally, the daughter of the brother affected by bladder cancer has a history of ovarian cancer diagnosed at age 35 years and recently was diagnosed with rectal cancer with hepatic lesions at the age of 56 years. K3326X, a polymorphic stop codon in the coding region of BRCA2, was first described as a polymorphism Cancer
Month 00, 2014
that does not increase susceptibility to breast cancer; however, its frequency was found to be < 1% in both controls and patients with breast cancer.2 A subsequent study demonstrated that deletion of the BRCA2 COOH terminus renders mouse cells hypersensitive to ionizing radiation and rapidly senescent, which is consistent with the hypothesis of defective MmRad51-mediated DNA repair.3 In addition, although K3326X appears to be unrelated to breast cancer susceptibility, several studies have suggested that it may increase the risk of other oncological diseases. In fact, the K3326X polymorphic stop codon, in the compound heterozygous state, has been associated with the onset of Fanconi anemia, a rare autosomal recessive cancer susceptibility syndrome that appears to be related to a BRCA2 mutation that disrupts the protein’s COOH terminus.4 Subsequently, the frequency of K3326X was found to be higher in patients with familial pancreatic cancer, lung cancer, and esophageal squamous cell carcinoma compared with control populations.5-7 Although our patient’s history strongly suggested the presence of familial neoplasias, the molecular analysis of BRCA1 and BRCA2 did not identify any previously defined causative mutation. Instead, it revealed the BRCA2 K3326X variant, which causes a premature stop codon and the loss of 93 amino acids at the protein’s C-terminus.2 We identified the K3326X variant in only 1 allele of 200 patients with breast cancer who were analyzed, which corresponds to a frequency of 0.25%. The case report described herein supports the heterogeneity of cancer types associated with a predisposing mutation, thereby suggesting that more complex pathogenetic mechanisms are related to BRCA2 variants than previously believed. Given the above-mentioned reports and our patient’s genotype and family history, caution should be exerted in considering BRCA2 K3326X as merely a benign polymorphism, as codified in the BIC database; rather, we believe this opens the debate that it may be considered a pathogenetic variant. FUNDING SUPPORT Supported by grant PS 35-126/Ind and grant PON01_02589 (MICROMAP) 2012 from the Ministry of University and Research (both to Dr. Salvatore) and grant RF-2010-2318372 from the Ministry of Health (to Dr. Salvatore).
CONFLICT OF INTEREST DISCLOSURES The authors made no disclosures. 1
Correspondence
REFERENCES 1. Lalloo F, Evans DG. Familial breast cancer. Clin Genet. 2012;82: 105-114. 2. Mazoyer S, Dunning AM, Serova O, et al. A polymorphic stop codon in BRCA2. Nat Genet. 1996;14:253-254. 3. Morimatsu M, Donoho G, Hasty P. Cells deleted for Brca2 COOH terminus exhibit hypersensitivity to gamma-radiation and premature senescence. Cancer Res. 1998;58:3441-3447. 4. Howlett NG, Taniguchi T, Olson S, et al. Biallelic inactivation of BRCA2 in Fanconi anemia. Science. 2002;297:606-609. 5. Martin ST, Matsubayashi H, Rogers CD, et al. Increased prevalence of the BRCA2 polymorphic stop codon K3326X among individuals with familial pancreatic cancer. Oncogene. 2005;24: 3652-3656. 6. Rudd MF, Webb EL, Matakidou A, et al. Variants in the GH-IGF axis confer susceptibility to lung cancer. Genome Res. 2006;16: 693-701.
2
7. Akbari MR, Malekzadeh R, Nasrollahzadeh D, et al. Germline BRCA2 mutations and the risk of esophageal squamous cell carcinoma. Oncogene. 2008;27:1290-1296.
Valeria D’Argenio, MD1,2 Maria Valeria Esposito, MS1,2 Jean Ann Gilder1,3 Giulia Frisso, MD, PhD1,2 Francesco Salvatore, MD, PhD1,2,4 1 CEINGE-Biotecnologie Avanzate, Naples, Italy Department of Molecular Medicine and Medical Biotechnologies, University of Naples Federico II Naples, Italy 3 Scientific Communication Srl, Naples, Italy 4 IRCCS-Fondazione SDN, Naples, Italy
2
DOI: 10.1002/cncr.28605, Published online Month 00, 2014 in Wiley Online Library (wileyonlinelibrary.com)
Cancer
Month 00, 2014
