Differences in cancer prevalence among CHEK2 carriers identified via multi-gene panel testing

A deep intronic recurrent CHEK2 variant c.1009-118_1009-87delinsC affects pre-mRNA splicing and contributes to hereditary breast cancer predisposition

Germline CHEK2 pathogenic variants confer an increased risk of female breast cancer (FBC). Here we describe a recurrent germline intronic variant c.1009-118_1009-87delinsC, which showed a splice acceptor shift in RNA analysis, introducing a premature stop codon (p.Tyr337PhefsTer37). The variant was found in 21/10,204 (0.21%) Czech FBC patients compared to 1/3250 (0.03%) controls (p = 0.04) and in 4/3639 (0.11%) FBC patients from an independent German dataset. In addition, we found this variant in 5/2966 (0.17%) Czech (but none of the 443 German) ovarian cancer patients, three of whom developed early-onset tumors. Based on these observations, we classified this variant as likely pathogenic.

Triple Primary Cancers: An Analysis of Genetic and Environmental Factors

The occurrence of multiple primary cancers (MPC) is thought to reflect increased cancer susceptibility in patients due to a combination of genetic and environmental factors. Here we conducted a retrospective review of 2,894 consecutive patients evaluated at a single institution and identified 31 (1.14%) individuals with a history of three or more primary cancers, then analyzed the genetic and environmental influences associated with their propensity for developing malignancies. We found that 35.5% of patients had a hereditary cancer syndrome (HCS), with high penetrance HCS in 72.7% of cases, suggesting that monogenic causes underly a significant proportion of triple primary cancer risk. Analysis of cancer frequencies found that the diagnosis of breast cancer was associated with a significantly lower likelihood of HCS, while the diagnosis of colorectal, prostate, and pancreas cancer was associated with a significantly higher likelihood of HCS. Comparison of HCS-positive and HCS-negative patients revealed similar demographic characteristics, mean age at first diagnosis, and family history of cancer. Moreover, no significant differences in lifestyle behaviors, occupational exposures, chronic health conditions, or treatment with chemotherapy and radiation were observed between HCS-positive and -negative groups, though outliers in tobacco smoking, as well as systemic treatment after both first and second primary cancers were observed. These findings indicate a robust contribution of HCS to cancer susceptibility among patients with triple primary cancers while environmental influences were less evident. This emphasizes the need for larger MPC cohorts incorporating additional genetic and environmental factors to more comprehensively characterize drivers of cancer risk.

PREVENTION RELEVANCE

In patients with three or more primary cancers, genetic predisposition explained a significant proportion of cases; however, treatment history, lifestyle habits, and other exposures appeared to play a less significant role. This highlights the value of early genetic screening and the need to develop more sensitive markers of cancer susceptibility. See related Spotlight, p. 193.

CHEK2 germline variants identified in familial nonmedullary thyroid cancer lead to impaired protein structure and function

Approximately 5 to 15% of nonmedullary thyroid cancers (NMTC) present in a familial form (familial nonmedullary thyroid cancers [FNMTC]). The genetic basis of FNMTC remains largely unknown, representing a limitation for diagnostic and clinical management. Recently, germline mutations in DNA repair-related genes have been described in cases with thyroid cancer (TC), suggesting a role in FNMTC etiology. Here, two FNMTC families were studied, each with two members affected with TC. Ninety-four hereditary cancer predisposition genes were analyzed through next-generation sequencing, revealing two germline CHEK2 missense variants (c.962A > C, p.E321A and c.470T > C, p.I157T), which segregated with TC in each FNMTC family. p.E321A, located in the CHK2 protein kinase domain, is a rare variant, previously unreported in the literature. Conversely, p.I157T, located in CHK2 forkhead-associated domain, has been extensively described, having conflicting interpretations of pathogenicity. CHK2 proteins (WT and variants) were characterized using biophysical methods, molecular dynamics simulations, and immunohistochemistry. Overall, biophysical characterization of these CHK2 variants showed that they have compromised structural and conformational stability and impaired kinase activity, compared to the WT protein. CHK2 appears to aggregate into amyloid-like fibrils in vitro, which opens future perspectives toward positioning CHK2 in cancer pathophysiology. CHK2 variants exhibited higher propensity for this conformational change, also displaying higher expression in thyroid tumors. The present findings support the utility of complementary biophysical and in silico approaches toward understanding the impact of genetic variants in protein structure and function, improving the current knowledge on CHEK2 variants' role in FNMTC genetic basis, with prospective clinical translation.

Profiling of the genetic features of patients with breast, ovarian, colorectal and extracolonic cancers: Association to CHEK2 and PALB2 germline mutations

BACKGROUND AND AIMS

Cancer predisposition goes beyond BRCA and DNA Mismatch Repair (MMR) genes since multi-gene panel testing has become the routine diagnostic tool for hereditary cancer suspicion (HCS) cases. CHEK2 and PALB2 are some of the foremost-mutated non-BRCA/MMR actionable genes in families with a significant familial aggregation. Therefore, the purpose of this work is to unravel which tumours other than breast, ovary or colorectal display the patients.

MATERIALS AND METHODS

We have analysed 528 probands that meet the inclusion criteria for Hereditary Breast and Ovarian Cancer and Lynch Syndrome established by our Hereditary Cancer Regional Program with a customized 35 genes-panel by using Ion Torrent™ Technology.

RESULTS

We have identified pathogenic variants (PVs) in 61 families (1.55%), of which more than half (31 probands) harboured PVs in CHEK2 and PALB2 genes. Ours results reveal that not only were PVs CHEK2 and PALB2 carriers more likely to have family history of cancer not limited to breast, ovarian or colorectal cancers, but also they are prone to other extracolonic cancers, noteworthy endometrial and gastric cancers.

CONCLUSIONS

Multigene panel testing improves the chance of finding PVs in actionable genes in families with HCS. In addition, the coexistence of variants should be recorded to implement a polygenic risk algorithm that might explain the missing heritability in the aforementioned families.

Breast and colorectal cancer risks among over 6,000 CHEK2 pathogenic variant carriers: A comparison of missense versus truncating variants

BACKGROUND AND AIMS

Heterozygous truncating pathogenic variants (PVs) in CHEK2 confer a 1.5 to 3-fold increased risk for breast cancer and may elevate colorectal cancer risks. Less is known regarding missense variants. Here we compared the cancer associations with truncating and missense PVs in CHEK2 across breast and colorectal cancer.

METHODS

This was a retrospective analysis of 705,797 patients who received single laboratory multigene panel testing between 2013 and 2020. Multivariable logistic regression models determined cancer risk associated with CHEK2 variants as odds ratios (ORs) and 95% confidence intervals (CIs) after adjusting for age at diagnosis, cancer history, and ancestry. Breast and colorectal cancer analyses were performed using 6255 CHEK2 PVs, including truncating PVs (N = 4505) and missense PVs (N = 1750).

RESULTS

CHEK2 PVs were associated with an increased risk of ductal invasive breast cancer (p < 0.001) and ductal carcinoma in situ (DCIS) (p < 0.001), with no statistically significant differences when truncating PVs (p < 0.001) and missense PVs (p < 0.001) were evaluated separately. All CHEK2 variants assessed conferred little to no risk of colorectal cancer.

CONCLUSIONS

In our large cohort, CHEK2 truncating and missense PVs conferred similar risks for breast cancer and did not seem to elevate risk for colorectal cancer.

Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG)

PURPOSE

Although the role of CHEK2 germline pathogenic variants in cancer predisposition is well known, resources for managing CHEK2 heterozygotes in clinical practice are limited.

METHODS

An international workgroup developed guidance on clinical management of CHEK2 heterozygotes informed by peer-reviewed publications from PubMed.

RESULTS

Although CHEK2 is considered a moderate penetrance gene, cancer risks may be considered as a continuous variable, which are influenced by family history and other modifiers. Consequently, early cancer detection and prevention for CHEK2 heterozygotes should be guided by personalized risk estimates. Such estimates may result in both downgrading lifetime breast cancer risks to those similar to the general population or upgrading lifetime risk to a level at which CHEK2 heterozygotes are offered high-risk breast surveillance according to country-specific guidelines. Risk-reducing mastectomy should be guided by personalized risk estimates and shared decision making. Colorectal and prostate cancer surveillance should be considered based on assessment of family history. For CHEK2 heterozygotes who develop cancer, no specific targeted medical treatment is recommended at this time.

CONCLUSION

Systematic prospective data collection is needed to establish the spectrum of CHEK2-associated cancer risks and to determine yet-unanswered questions, such as the outcomes of surveillance, response to cancer treatment, and survival after cancer diagnosis.

Molecular characteristics of breast tumors in patients screened for germline predisposition from a population-based observational study

BACKGROUND

Pathogenic germline variants (PGVs) in certain genes are linked to higher lifetime risk of developing breast cancer and can influence preventive surgery decisions and therapy choices. Public health programs offer genetic screening based on criteria designed to assess personal risk and identify individuals more likely to carry PGVs, dividing patients into screened and non-screened groups. How tumor biology and clinicopathological characteristics differ between these groups is understudied and could guide refinement of screening criteria.

METHODS

Six thousand six hundred sixty breast cancer patients diagnosed in South Sweden during 2010-2018 were included with available clinicopathological and RNA sequencing data, 900 (13.5%) of which had genes screened for PGVs through routine clinical screening programs. We compared characteristics of screened patients and tumors to non-screened patients, as well as between screened patients with (n = 124) and without (n = 776) PGVs.

RESULTS

Broadly, breast tumors in screened patients showed features of a more aggressive disease. However, few differences related to tumor biology or patient outcome remained significant after stratification by clinical subgroups or PAM50 subtypes. Triple-negative breast cancer (TNBC), the subgroup most enriched for PGVs, showed the most differences between screening subpopulations (e.g., higher tumor proliferation in screened cases). Significant differences in PGV prevalence were found between clinical subgroups/molecular subtypes, e.g., TNBC cases were enriched for BRCA1 PGVs. In general, clinicopathological differences between screened and non-screened patients mimicked those between patients with and without PGVs, e.g., younger age at diagnosis for positive cases. However, differences in tumor biology/microenvironment such as immune cell composition were additionally seen within PGV carriers/non-carriers in ER + /HER2 - cases, but not between screening subpopulations in this subgroup.

CONCLUSIONS

Characterization of molecular tumor features in patients clinically screened and not screened for PGVs represents a relevant read-out of guideline criteria. The general lack of molecular differences between screened/non-screened patients after stratification by relevant breast cancer subsets questions the ability to improve the identification of screening candidates based on currently used patient and tumor characteristics, pointing us towards universal screening. Nevertheless, while that is not attained, molecular differences identified between PGV carriers/non-carriers suggest the possibility of further refining patient selection within certain patient subsets using RNA-seq through, e.g., gene signatures.

TRIAL REGISTRATION

The Sweden Cancerome Analysis Network - Breast (SCAN-B) was prospectively registered at ClinicalTrials.gov under the identifier NCT02306096.

The CHK2 kinase is recurrently mutated and functionally impaired in the germline of pediatric cancer patients

Predisposing CHEK2 germline variants are associated with various adult-type malignancies, whereas their impact on cancer susceptibility in childhood cancer is unclear. To understand the frequency of germline variants in the CHEK2 gene and their impact on pediatric malignancies, we used whole-exome sequencing to search for CHEK2 variants in the germlines of 418 children diagnosed with cancer in our clinics. Moreover, we performed functional analysis of the pathogenic CHEK2 variants to analyze the effect of the alterations on CHK2 protein function. We detected a CHEK2 germline variant in 32/418 (7.7%) pediatric cancer patients and 46.8% of them had leukemia. Functional analysis of the pathogenic variants revealed that 5 pathogenic variants impaired CHK2 protein function. 6/32 patients carried one of these clearly damaging CHEK2 variants and two of them harbored a matching family history of cancer. In conclusion, we detected germline CHEK2 variants in 7.7% of all pediatric cancer patients, of which a minority but still relevant fraction of approximately 20% had a profound impact on protein expression or its phosphorylation after irradiation-induced DNA damage. Accordingly, we conclude that CHEK2 variants increase the risk for not only adult-onset but also pediatric cancer.

Two unrelated cases with biallelic CHEK2 variants:a novel condition with constitutional chromosomal instability?

Constitutional heterozygous mutations in CHEK2 gene have been associated with hereditary cancer risk. To date, only a few homozygous CHEK2 mutations have been reported in families with cancer susceptibility. Here, we report two unrelated individuals with a personal and familial cancer history in whom biallelic CHEK2 alterations were identified. The first case resulted homozygous for the CHEK2 c.793-1 G > A (p.Asp265Thrfs*10) variant, and the second one was found to be compound heterozygous for the c.1100delC (p.Thr367Metfs*15) and the c.1312 G > T (p.Asp438Tyr) variants. Multiple cytogenetic anomalies were demonstrated on peripheral lymphocytes of both patients. A literature revision showed that a single other CHEK2 homozygous variant was previously associated to a constitutional randomly occurring multi-translocation karyotype from peripheral blood in humans. We hypothesize that, at least some biallelic CHEK2 mutations might be associated with a novel disorder, further expanding the group of chromosome instability syndromes. Additional studies on larger cohorts are needed to confirm if chromosomal instability could represent a marker for CHEK2 constitutionally mutated recessive genotypes, and to investigate the cancer risk and the occurrence of other anomalies typically observed in chromosome instability syndromes.

Genomic Breakpoints’ Characterization of a Large CHEK2 Duplication in an Italian Family with Hereditary Breast Cancer

CHEK2 (checkpoint kinase 2; MIM# 604373) is a tumor suppressor gene that encodes a serine threonine kinase involved in pathways such as DNA repair, cell cycle arrest, mitosis, and apoptosis. Pathogenic variants in CHEK2 contribute to a moderately increased risk of breast and other cancers. Several variant classes have been reported, either point mutations or large intragenic rearrangements. However, a significant portion of reported variants has an uncertain clinical significance. We report an intragenic CHEK2 duplication, ranging from intron 5 to intron 13, identified in an Italian family with hereditary breast cancer. Using long range PCR, with duplication-specific primers, we were able to ascertain the genomic breakpoint. We also performed a real-time PCR to assess a possible loss-of-function effect. The genomic characterization of large intragenic rearrangements in cancer susceptibility genes is important for the clinical management of the carriers and for a better classification of rare variants. The molecular definition of breakpoints allows for the prediction of the impact of the variant on transcripts and proteins, aiding in its characterization and clinical classification.

Comprehensive Molecular Profiling of Colorectal Cancer With Situs Inversus Totalis by Next-Generation Sequencing

Background

Colorectal cancer (CRC) is one of the most prevalent malignances worldwide. However, CRC with situs inversus totalis (SCRC) is extremely rare, and molecular characterization of this disease has never been investigated.

Methods

Tumor tissue samples from 8 patients with SCRC and 33 CRC patients without situs inversus totalis (NSCRC) were subjected to multigene next-generation sequencing.

Results

The most frequently mutated genes in SCRC were APC, TP53, CHEK2, MDC1, GNAQ, KRAS, and SMAD4. A high frequency of SCRC tumors had mutations in DNA damage repair genes. Single amino acid substitutions in the DNA damage repair genes caused by continuous double base substitution was identified in the majority of this population. Furthermore, mutational profiles showed notable differences between the SCRC and NSCRC groups. In particular, CHEK2, MDC1, GNAQ, SMAD4, BRCA1, HLA-B, LATS2, and NLRC5 mutations were more frequently observed in SCRC patients. The mutation loci distributions of KRAS in the SCRC cohort differed from that of the NSCRC cohort. Additionally, differences in the targeted genomic profiles and base substitution patterns were observed between the two groups.

Conclusions

These findings comprehensively revealed a molecular characterization of SCRC, which will contribute to the development of personalized therapy and improved clinical management of SCRC patients.

CHEK2p.I157T Mutation Is Associated with Increased Risk of Adult-Type Ovarian Granulosa Cell Tumors

Pathogenic germline mutations c.1100delC and p.I157T in the CHEK2 gene have been associated with increased risk of breast, colon, kidney, prostate, and thyroid cancers; however, no associations have yet been identified between these two most common European founder mutations of the CHEK2 gene and ovarian cancers of any type. Our review of 78 female heterozygous carriers of these mutations (age > 18 years) found strikingly higher proportion of adult-type granulosa cell tumors of the ovary (AGCTs) among ovarian cancers that developed in these women (~36%) compared to women from the general population (1.3%). Based on this finding, we performed a cross-sectional study that included 93 cases previously diagnosed with granulosa cell tumors, refined and validated their AGCT diagnosis through an IHC study, determined their status for the two CHEK2 mutations, and compared the prevalence of these mutations in the AGCT cases and reference populations. The prevalence ratios for the p.I157T mutation in the AGCT group relative to the global (PR = 26.52; CI95: 12.55−56.03) and European non-Finnish populations (PR = 24.55; CI95: 11.60−51.97) support an association between the CHEK2p.I157T mutation and AGCTs. These rare gynecologic tumors have not been previously associated with known risk factors and genetic predispositions. Furthermore, our results support the importance of the determination of the FOXL2p.C134W somatic mutation for accurate diagnosis of AGCTs and suggest a combination of IHC markers that can serve as a surrogate diagnostic marker to infer the mutational status of this FOXL2 allele.

CHEK2 mutations and papillary thyroid cancer: correlation or coincidence?

We report the case of a breast cancer survivor, diagnosed with an underlying CHEK2 c.1100delC heterozygosity, who developed a papillary thyroid cancer 5 years later. A CHEK2 c.1100delC (likely) pathogenic variant is associated with an increased risk of breast, prostate and colorectal cancer and therefore risk-specific screening will be offered. Current national and international screening guidelines do not recommend routine screening for thyroid cancer. Hence, we reviewed the literature to explore the possible association between a CHEK2 mutation and thyroid cancer. A weak association was found between the various CHEK2 mutations and papillary thyroid cancer. The evidence for an association with CHEK2 c.1100delC in particular is the least robust. In conclusion, there is insufficient evidence to warrant systematic thyroid screening in CHEK2 carriers.

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.

A Genome-Wide Profiling of Glioma Patients with an IDH1 Mutation Using the Catalogue of Somatic Mutations in Cancer Database

Simple Summary

Glioma patients that present a somatic mutation in the isocitrate dehydrogenase 1 (IDH1) gene have a significantly better prognosis and overall survival than patients with the wild-type genotype. An IDH1 mutation is hypothesized to occur early during cellular transformation and leads to further genetic instability. A genome-wide profiling of glioma patients in the Catalogue of Somatic Mutations in Cancer (COSMIC) database was performed to classify the genetic differences in IDH1-mutant versus IDH1-wildtype patients. This classification will aid in a better understanding of how this specific mutation influences the genetic make-up of glioma and the resulting prognosis. Key differences in co-mutation and gene expression levels were identified that correlate with an improved prognosis.

Abstract

Gliomas are differentiated into two major disease subtypes, astrocytoma or oligodendroglioma, which are then characterized as either IDH (isocitrate dehydrogenase)-wild type or IDH-mutant due to the dramatic differences in prognosis and overall survival. Here, we investigated the genetic background of IDH1-mutant gliomas using the Catalogue of Somatic Mutations in Cancer (COSMIC) database. In astrocytoma patients, we found that IDH1 is often co-mutated with TP53, ATRX, AMBRA1, PREX1, and NOTCH1, but not CHEK2, EGFR, PTEN, or the zinc finger transcription factor ZNF429. The majority of the mutations observed in these genes were further confirmed to be either drivers or pathogenic by the Cancer-Related Analysis of Variants Toolkit (CRAVAT). Gene expression analysis showed down-regulation of DRG2 and MSN expression, both of which promote cell proliferation and invasion. There was also significant over-expression of genes such as NDRG3 and KCNB1 in IDH1-mutant astrocytoma patients. We conclude that IDH1-mutant glioma is characterized by significant genetic changes that could contribute to a better prognosis in glioma patients.

Recent Insights on Genetic Testing in Primary Prostate Cancer

Prostate cancer (PCa) is one of the most common cancers in developed countries. The results of large trials indicate that the proportion of PCa attributable to hereditary factors is as high as 15%, highlighting the importance of genetic testing. Despite improved understanding of the prevalence of pathogenic variants among men with PCa, it remains unclear which men will most benefit from genetic testing. In this review, we summarize recent evidence on genetic testing in primary PCa and its impact on routine clinical practice. We outline current guideline recommendations on genetic testing, most importantly, for mutations in BRCA1/2, MMR, CHEK2, PALB2, and HOXB13 genes, as well as various single nucleotide polymorphisms associated with an increased risk of developing PCa. The implementation of genetic testing in clinical practice, especially in young patients with aggressive tumors or those with positive family history, represents a new challenge for the coming years and will identify men with pathogenic variants who may benefit from early screening/intervention and specific therapeutic options.

Genetically Informed Prostate Cancer Screening

Prostate cancer represents a significant health care burden in the United States due to its incidence, treatment-related morbidity, and cancer-specific mortality. The burden begins with prostate-specific antigen screening, which has been subject to controversy due to concerns of overdiagnosis and overtreatment. Advancements in molecular oncology have provided evidence for the inherited predisposition to prostate cancer, which could improve individualized, risk-adapted approaches to screening and mitigate the harms of routine screening. This review presents the current evidence for the genetic basis of prostate cancer and novel genetically informed, risk-adapted screening strategies for prostate cancer.

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.