Identification of CHEK2 germline mutations in BRCA1/2 and PALB2 negative breast and ovarian cancer patients

Introduction: The CHEK2 gene is known to be an important signal transducer involved in DNA repair, apoptosis, or cell cycle arrest in response to DNA damage. The mutations in this gene have been associated with a wide range of cancers, both sporadic and hereditary. Germline CHEK2 mutations are linked to an increased risk of breast cancer. Therefore, the aim of this study was to identify the prevalence of CHEK2 variants in BRCA1/2 and PALB2 negative early-onset patients with breast cancer and/or ovarian cancer in a Turkish population for the first time. Methods: The study included 95 patients with BRCA1/2 and PALB2 negative early-onset breast cancer and/or ovarian cancer and also 60 unaffected women. All the intron/exon boundaries and coding exons of CHEK2 were subjected to mutational analysis by heteroduplex analysis and DNA sequencing. Results: A total of 16 CHEK2 variants were found in breast cancer patients within the Turkish population. CHEK2 c.1100delC mutation studied in the CHEK2 gene most frequently was not detected in our study. The prevalence of variants of uncertain significance in CHEK2 was found to be 7.3% (n= 7) in BRCA1/2 and PALB2 mutation negative Turkish patients with early-onset breast and/or ovarian cancer. Discussion/Conclusion: The present study may shed light on alternative variations that could be significant for understanding the prevalence and clinical suitability of the CHEK2 gene.

Recurrent Germline Mutations of CHEK2 as a New Susceptibility Gene in Patients with Pheochromocytomas and Paragangliomas

Purpose. Recently, pheochromocytomas and paragangliomas (PPGLs) have been strongly suspected as hereditary tumors, as approximately 40% of patients carry germline mutations. In the cancers where defects occur to corrupt DNA repair and facilitate tumorigenesis, a CHEK2 strong association has been observed. Therefore, the purpose of this study was to investigate the effect of CHEK2 mutations for its possible pathogenicity in PPGLs. Methods. Four patients with CHEK2 mutations were recruited, as previously detected by the whole exome sequencing. Sanger sequencing was used to verify the germline mutations as well as the loss of heterozygosities (LOHs) in their somatic DNAs. Immunohistochemistry was used to analyze the expression of CHEK2 and its downstream target p53 Ser20 (phosphorylated p53). Results. The average age of studied patients was 44.25 ± 11.18 years, at the time diagnosis. One patient had multiple tumors which recurred quickly, while two patients had distant metastasis. None of the patient had any relevant family history. Four germline CHEK2 mutations were identified (c.246_260del; c.715G > A; c.1008+3A > T; and c.1111C > T). All the patients were predicted to have either pathogenic or suspected pathogenic mutations. There was no LOH of CHEK2 gene in somatic DNAs found. Additionally, neither CHEK2 proteins nor its downstream target p53 Ser20 were expressed in the tumor tissues. The inactivation of CHEK2 leads to the decrease in the p53 phosphorylation, which might promote tumorigenesis. Conclusions. For the first time, CHEK2 was identified as a susceptibility gene for PPGLs. However, the penetrance of CHEK2 gene with genotype-phenotype correlation needs to be investigated.

Hereditary breast cancer associated with the CHEK2 gene: Study through NGS in a Spanish cohort.

e22502 Background: Inherited mutations in the CHEK2 gene have been associated with an increased lifetimerisk of develop breast cancer (BC). The main objective of the study is to identify in our population the prevalence of mutations in the CHEK2 gene in diagnosed BC patients, as well as to evaluate the phenotypic characteristics of the tumour and family history. Methods: A genetic study was performed in 396 patients diagnosed of BC at the University Hospital Lozano Blesa of Zaragoza (Spain). We selected 9 patients with genetic variants in the CHEK2 gene and performed a descriptive analysis of the clinical variables, a bibliographic review of the genetic variants and a co-segregation study. Results: We identified 2 pathogenic variants ( CHEK2 c.349 A>G and c.507delT) and 6 variants of uncertain significance (VUS). The genotypic characteristics of the VUS are summarized in the table. In all cases there was a family history of BC in first and /or second degree relatives. The variant cosegregated with the disease in one of the families. Conclusions: The pathogenic missense variant c.349A>G was found in two families. This is a rare missense variant. Studies have shown that this variant had a significant impact on the protein based on in silico prediction and has been associated with BC. In our study, this variant was found in a patient with renal carcinoma and was identified in a proband with a strong family history of pancreatic and ovarian cancer (OC). However, there aren’t exist data about the risk of developing other cancer, different of BC, with this specific mutation. The other pathogenic variant detected was CHEK2 c.507delT in a family with history of BC and OC. This variant is a frameshift mutation, predicted to cause loss of normal protein function. CHEK2 507delT was reported in one of 12 BC families in one series and is possible its relation with OC. With regard to the VUS the cosegregation analysis in selected families may help understand if a variant could have played a role in developing cancer. In conclusion, CHEK2 mutations have been associated with increased risk for BC. However, the frequency of carriers may vary depending on the population, and different mutations may be associated with different cancer risks. More studies are needed to establish a complete range of risks associated with CHEK2 mutations. [Table: see text]

The clinical and molecular characteristics of patients with personal or family history of gastrointestinal malignancies/polyposis and checkpoint kinase 2 (CHEK2) mutations.

44 Background: Checkpoint Kinase 2 (CHEK 2) encodes the protein CHK2, a serine/threonine kinase involved in pathways that conduct DNA repair as well as apoptosis in response to initial DNA damage. Germline mutations in the CHEK2 gene are associated with several malignancies such as colon, breast, stomach, prostate, kidney, thyroid and soft tissue cancers. Here, we describe the clinical and molecular characteristics of patients with personal or family history of gastrointestinal (GI) malignancies/polyposis and CHEK2 gene mutations. Methods: This is an IRB-approved retrospective chart-review study. Between 2016 and 2020, 1011 unique genetic counseling visits were conducted. Germline testing was recommended by a certified genetic counselor if medically necessary. All patients with a germline CHEK2 mutation were identified (N = 16). Patients with a CHEK2 mutation and personal and family history of GI malignancies/polyposis were further explored and their clinical and molecualr characteristics are summarized. Results: The reasons for referral to the Cancer Genetics Counseling Services in patients with pathogenic CHEK2 mutations were personal history of colon cancer (N = 3) and family history of colon cancer (N = 4). One patient with the CHEK2 c.1100delC mutation had a personal history of juvenile polyposis syndrome and a family history of colon cancer. In our cohort, 11 out of 16 (69%) patients had a CHEK2 mutation and personal or family history of GI malignancies/polyposis. The median age was 57 years old (25-80). Six (55%) patients were males. All (100%) patients were Caucasians. Seven (64%) patients had a pathogenic germline CHEK2 mutation and 4 (36%) patients had a variant of unknown significance (VUS). Among patients with pathogenic germline CHEK2 mutations (N = 7), 5 (72%) patients had CHEK2 c.1100delC mutation, 1 (14%) patient had CHEK2 c.190G > A mutation and 1 (14%) patient had CHEK2 c.470T > C mutation. The CHEK2 VUS mutations seen in our cohort were CHEK2 c.539G > A, CHEK2 p.V395L, CHEK2 gain of exons 3-15 and CHEK2 c.1421G > A mutations. Conclusions: All patients in our cohort with CHEK2 mutations were Caucasians. The majority of our patients (69%) had an underlying personal or family history of GI malignancies/polyposis. In patients with personal or family history of GI malignancies/polyposis and CHEK2 mutation, 64% were found to have pathogenic CHEK2 mutations. The most common diagnosed CHEK2 mutation in our cohort was CHEK2 c.1100delC mutation.

CHEK2 Germline Variants in Cancer Predisposition: Stalemate Rather than Checkmate

Germline alterations in many genes coding for proteins regulating DNA repair and DNA damage response (DDR) to DNA double-strand breaks (DDSB) have been recognized as pathogenic factors in hereditary cancer predisposition. The ATM-CHEK2-p53 axis has been documented as a backbone for DDR and hypothesized as a barrier against cancer initiation. However, although CHK2 kinase coded by the CHEK2 gene expedites the DDR signal, its function in activation of p53-dependent cell cycle arrest is dispensable. CHEK2 mutations rank among the most frequent germline alterations revealed by germline genetic testing for various hereditary cancer predispositions, but their interpretation is not trivial. From the perspective of interpretation of germline CHEK2 variants, we review the current knowledge related to the structure of the CHEK2 gene, the function of CHK2 kinase, and the clinical significance of CHEK2 germline mutations in patients with hereditary breast, prostate, kidney, thyroid, and colon cancers.

BRCA1/2 and CHEK2 mutation prevalence in patients with breast and/or ovarian cancer in the South of Russia.

e13088 Background: The development of breast cancer (BC) and ovarian cancer (OC), as well as their chemoresistance may be due to the presence of mutations in many genes, but most often in BRCA1/2 and CHEK2. Early diagnosis and subsequent preventive interventions improve the survival of patients with mutations in the BRCA1/2 genes. Genotyping of the gene inactivation events predicts a high sensitivity of BC and OC to platinum-containing cytostatics. Our purpose was to study the spectrum of germline mutations in the BRCA1/2 and CHEK2 genes in BC and/or OC patients in the South of Russia. Methods: The study included 622 patients of 10 nationalities with BC and/or OC from the South of Russia. Genomic DNA was isolated from peripheral blood leukocytes; mutations were detected by Real-Time PCR in the BRCA1 (185delAG, 300T > C, 2080delA, 4154delA, 5382insC, 3819delGTAAA, 3875delGTCT), BRCA2 (6174delT), CHEK2 (1100delC, IVS2+1G > A, 470T > C) genes. Results: Mutations in the BRCA1/2 gene were found in 13.5% of cases, in CHEK2 – 6.2%. In the BRCA1/2 gene, the frequency of 5382insC mutation was 76.2%; 4153 delA – 9.5%; 300T > G – 7.1%; 2080delA – 3.6%; 185delAG, 3875delGTCT, 6174delT - 1.2% each. In the CHEK2 gene: 470Т > C – 73.1%; IVS2+1G > A – 23.1%; 1100delC – 3.8%. Two patients showed a combination of 5382insC mutation in the BRCA1 gene and 470T > C mutation in the CHEK2 gene. The observed prevalence of mutations in BRCA1 was generally consistent with that for European countries (p = 0.062). Identification of 470T > C mutation in CHEK2 in two cases confirmed the final diagnosis of Li-Fraumeni syndrome (OMIM: 609265); however, we failed to establish a family history of cancer in one patient. A high-risk cancer group was formed for prophylactic purposes based on the data of genotyping for major mutations in the BRCA1/2 and CHEK2 genes in patients with BC/OC and their healthy relatives. Conclusions: The frequency of BRCA1/2 and CHEK2 mutations in the studied multinational population of Caucasian patients with BC and/or OC was 17.2%. The 5382insC BRCA1/2 (76.2%) and 470Т > C CHEK2 (73.1%) mutations were the most frequent which corresponded to the occurrence of these SNPs in populations of European countries.