Moderate penetrance genes complicate genetic testing for breast cancer diagnosis: ATM, CHEK2, BARD1 and RAD51D

Hereditary Breast Cancer: BRCA Mutations and Beyond

Hereditary breast cancers are manifested by pathogenic and likely pathogenic genetic mutations. Penetrance expresses the breast cancer risk associated with these genetic mutations. Although BRCA1/2 are the most widely known genetic mutations associated with breast cancer, numerous additional genes demonstrate high and moderate penetrance for breast cancer. This review describes current genetic testing, details the specific high and moderate penetrance genes for breast cancer and reviews the current approach to screening for breast cancer in patients with these genetic mutations.

Role of Breast Cancer Risk Estimation Models to Identify Women Eligible for Genetic Testing and Risk-Reducing Surgery

Hereditary breast and ovarian cancer (HBOC) syndrome is responsible for approximately 10% of breast cancers (BCs). The HBOC gene panel includes both high-risk genes, i.e., a four times higher risk of BC (BRCA1, BRCA2, PALB2, CDH1, PTEN, STK11 and TP53), and moderate-risk genes, i.e., a two to four times higher risk of BC (BARD1, CHEK2, RAD51C, RAD51D and ATM). Pathogenic germline variants (PGVs) in HBOC genes confer an absolute risk of BC that changes according to the gene considered. We illustrate and compare different BC risk estimation models, also describing their limitations. These models allow us to identify women eligible for genetic testing and possibly to offer surgical strategies for primary prevention, i.e., risk-reducing mastectomies and salpingo-oophorectomies.

Genetic counselors' and community clinicians' implementation and perceived barriers to informed consent during pre-test counseling for hereditary cancer risk

As demand for genetic cancer risk assessment (GCRA) continues to increase, so does the sense of urgency to scale up efforts to triage patients, facilitate informed consent, and order genetic testing for cancer risk. The National Society of Genetic Counselors outlines the elements of informed consent that should be addressed in a GCRA session. While this practice resource aims to improve health equity, research on how well the elements of informed consent are implemented in practice is lacking. This retrospective and prospective mixed-methods study assessed how adequately the elements of informed consent are addressed during pre-test GCRA among 307 community clinicians (CC) and 129 cancer genetic counselors (GC), and barriers they face to addressing these elements. Results revealed that more than 90% of both cohorts consistently addressed components of at least 5 of the 10 elements of informed consent during a pre-test consultation. Technical aspects and accuracy of the test and utilization of test results were the most similarly addressed elements. Notably, GCs more often review the purpose of the test and who to test, general information about the gene(s), and economic considerations whereas CCs more often review alternatives to testing. Both cohorts reported psychosocial aspects of the informed consent process as the least adequately addressed element. Time constraints and patient-related concerns were most often cited by both cohorts as barriers to optimal facilitation of informed consent. Additional barriers reported by CCs included provider lack of awareness, experience, or education, and availability of resources and institutional support. Findings from this study may contribute to the development of alternative delivery models that incorporate supplementary educational tools to enhance patient understanding about the utility of genetic testing, while helping to mitigate the barrier of time constraints. Equally important is the use of this information to develop continuing education tools for providers.

[News in breast oncology genetics for female and male population]

OBJECTIVES

Breast oncology genetics emerged almost 30 years ago with the discovery of the BRCA1 and BRCA2 genes. The evolution of analytical practices has progressively allowed access to tests whose results now have a considerable impact on the management of both female and male breast cancers. The Sénologie commission of the Collège national des gynécologues et obstétriciens français (CNGOF) asked five specialists in breast surgery, oncology and oncological genetics to draw up a summary of the oncogenetic testing criteria used and the clinical implications for the female and male population of the test results, with or without an identified causal variant. In the case of proven genetic risk, surveillance, risk-reduction strategies, and the specificities of surgical and medical management (with PARP inhibitors in particular) were updated.

METHODS

This summary was based on national and international guidelines on the monitoring and therapeutic management of genetic risk, and a recent review of the literature covering the last five years.

RESULTS

Despite successive technical developments, the probability of identifying a causal variant in a situation suggestive of a predisposition to breast and ovarian cancer remains around 10% in France. The risk of breast cancer in women with a causal variant of the BRCA1, BRCA2, PALB2, TP53, CDH1 and PTEN genes is estimated at between 35% and 85% at age 70. The presence of a causal variant in one of these genes is the subject of different recommendations for men and women, concerning both surveillance, the age of onset and imaging modalities of which vary according to the genes involved, and risk-reduction surgery, which is possible for women as soon as their risk level exceeds 30% and remains exceptionally indicated for men. In the case of breast cancer, PARP inhibitors are a promising new class of treatment for BRCA germline mutations.

CONCLUSION

A discipline resolutely focused on understanding molecular mechanisms, screening and preventive medicine/surgery, oncology genetics is currently also involved in new medical/surgical approaches, the long-term benefits/risks of which will need to be monitored.

Germline mutations of 4567 patients with hereditary breast-ovarian cancer spectrum in Thailand

Multi-gene panel testing has led to the detection of pathogenic/likely pathogenic (P/LP) variants in many cancer susceptibility genes in patients with breast-ovarian cancer spectrum. However, the clinical and genomic data of Asian populations, including Thai cancer patients, was underrepresented, and the clinical significance of multi-gene panel testing in Thailand remains undetermined. In this study, we collected the clinical and genetic data from 4567 Thai patients with cancer in the hereditary breast-ovarian cancer (HBOC) spectrum who underwent multi-gene panel testing. Six hundred and ten individuals (13.4%) had germline P/LP variants. Detection rates of germline P/LP variants in breast, ovarian, pancreatic, and prostate cancer were 11.8%, 19.8%, 14.0%, and 7.1%, respectively. Non-BRCA gene mutations accounted for 35% of patients with germline P/LP variants. ATM was the most common non-BRCA gene mutation. Four hundred and thirty-two breast cancer patients with germline P/LP variants (80.4%) met the current NCCN genetic testing criteria. The most common indication was early-onset breast cancer. Ten patients harbored double pathogenic variants in this cohort. Our result showed that a significant proportion of non-BRCA P/LP variants were identified in patients with HBOC-related cancers. These findings support the benefit of multi-gene panel testing for inherited cancer susceptibility among Thai HBOC patients. Some modifications of the testing policy may be appropriate for implementation in diverse populations.

High-Grade Serous Ovarian Cancer-A Risk Factor Puzzle and Screening Fugitive

High-grade serous ovarian cancer (HGSOC) is the most lethal tumor of the female genital tract. Despite extensive studies and the identification of some precursor lesions like serous tubal intraepithelial cancer (STIC) or the deviated mutational status of the patients (BRCA germinal mutation), the pathophysiology of HGSOC and the existence of particular risk factors is still a puzzle. Moreover, a lack of screening programs results in delayed diagnosis, which is accompanied by a secondary chemo-resistance of the tumor and usually results in a high recurrence rate after the primary therapy. Therefore, there is an urgent need to identify the substantial risk factors for both predisposed and low-risk populations of women, as well as to create an economically and clinically justified screening program. This paper reviews the classic and novel risk factors for HGSOC and methods of diagnosis and prediction, including serum biomarkers, the liquid biopsy of circulating tumor cells or circulating tumor DNA, epigenetic markers, exosomes, and genomic and proteomic biomarkers. The novel future complex approach to ovarian cancer diagnosis should be devised based on these findings, and the general outcome of such an approach is proposed and discussed in the paper.

Anthracycline-related cardiotoxicity in patients with breast cancer harboring mutational signature of homologous recombination deficiency (HRD)

BACKGROUND

The BRCA proteins play a key role in the homologous recombination (HR) pathway. Beyond BRCA1/2, other genes are involved in the HR repair (HRR). Due to the prominent role in the cellular repair process, pathogenic or likely pathogenic variants (PV/LPVs) in HRR genes may cause inadequate DNA damage repair in cardiomyocytes.

PATIENTS AND METHODS

This was a multicenter, hospital-based, retrospective cohort study to investigate the heart toxicity from anthracycline-containing regimens (ACRs) in the adjuvant setting of breast cancer (BC) patients carrying germline BRCA PV/LPVs and no-BRCA HRR pathway genes. The left ventricular ejection fraction (LVEF) was assessed using cardiac ultrasound before starting ACR therapy and at subsequent time points according to clinical indications.

RESULTS

Five hundred and three BC patients were included in the study. We predefined three groups: (i) BRCA cohort; (ii) no-BRCA cohort; (iii) variant of uncertain significance (VUS)/wild-type (WT) cohort. When baseline (T0) and post-ACR (T1) LVEFs between the three cohorts were compared, pre-treatment LVEF values were not different (BRCA1/2 versus HRR-no-BRCA versus VUS/WT cohort). Notably, during monitoring (T1, median 3.4 months), patients carrying BRCA or HRR no-BRCA germline pathogenic or likely pathogenic variants showed a statistically significant reduction of LVEF compared to baseline (T0). To assess the relevance of HRR on the results, we included the analysis of the subgroup of 20 BC patients carrying PV/LPVs in other genes not involved in HRR, such as mismatch repair genes (MUTYH, PMS2, MSH6). Unlike HRR genes, no significant differences in T0-T1 were found in this subgroup of patients.

CONCLUSION

Our data suggest that deleterious variants in HRR genes, leading to impaired HR, could increase the sensitivity of cardiomyocytes to ACR in early BC patients. In this subgroup of patients, other measurements, such as the global longitudinal strain, and a more in-depth assessment of risk factors may be proposed in the future to optimize cardiovascular risk management and improve long-term survival.

Understanding the mechanistic pathways and clinical aspects associated with protein and gene based biomarkers in breast cancer

Cancer is one of the most widespread and severe diseases with a huge mortality rate. In recent years, the second-leading mortality rate of any cancer globally has been breast cancer, which is one of the most common and deadly cancers found in women. Detecting breast cancer in its initial stages simplifies treatment, decreases death risk, and recovers survival rates for patients. The death rate for breast cancer has risen to 0.024 % in some regions. Sensitive and accurate technologies are required for the preclinical detection of BC at an initial stage. Biomarkers play a very crucial role in the early identification as well as diagnosis of women with breast cancer. Currently, a wide variety of cancer biomarkers have been discovered for the diagnosis of cancer. For the identification of these biomarkers from serum or other body fluids at physiological amounts, many detection methods have been developed. In the case of breast cancer, biomarkers are especially helpful in discovering those who are more likely to develop the disease, determining prognosis at the time of initial diagnosis and choosing the best systemic therapy. In this study we have compiled various clinical aspects and signaling pathways associated with protein-based biomarkers and gene-based biomarkers.

Theranostic biomarkers and PARP-inhibitors effectiveness in patients with non-BRCA associated homologous recombination deficient tumors: Still looking through a dirty glass window?

Breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2) deleterious variants were the first and, still today, the main biomarkers of poly(ADP)ribose polymerase (PARP)-inhibitors (PARPis) benefit. The recent, increased, numbers of individuals referred for counseling and multigene panel testing, and the remarkable expansion of approved PARPis, not restricted to BRCA1/BRCA2-Pathogenic Variants (PVs), produced a strong clinical need for non-BRCA biomarkers. Significant limitations of the current testing and assays exist. The different approaches that identify the causes of Homologous Recombination Deficiency (HRD), such as the germline and somatic Homologous Recombination Repair (HRR) gene PVs, the testing showing its consequences, such as the genomic scars, or the novel functional assays such as the RAD51 foci testing, are not interchangeable, and should not be considered as substitutes for each other in clinical practice for guiding use of PARPi in non-BRCA, HRD-associated tumors. Today, the deeper knowledge on the significant relationship among all proteins involved in the HRR, not limited to BRCA, expands the possibility of a successful non-BRCA, HRD-PARPi synthetic lethality and, at the same time, reinforces the need for enhanced definition of HRD biomarkers predicting the magnitude of PARPi benefit.

CHEK2 is not a Li-Fraumeni syndrome gene: time to update public resources

The gene-disease relationship for CHEK2 remains listed as 'Li-Fraumeni syndrome 2' in public resources such as OMIM and MONDO, despite published evidence to the contrary, causing frustration among Li-Fraumeni syndrome (LFS) clinical experts. Here, we compared personal cancer characteristics of 2095 CHEK2 and 248 TP53 pathogenic variant carriers undergoing multigene panel testing at Ambry Genetics against 15 135 individuals with no known pathogenic variant. Our results from a within-cohort logistic regression approach highlight obvious differences between clinical presentation of TP53 and CHEK2 pathogenic variant carriers, with no evidence of CHEK2 being associated with any of the TP53-related core LFS cancers. These findings emphasise the need to replace 'Li-Fraumeni syndrome 2' as the CHEK2-associated disease name, thereby limiting potential confusion.

Multigene testing panels reveal pathogenic variants in sporadic breast cancer patients in northern China

Background: Breast cancer, the most prevalent malignancy in women worldwide, presents diverse onset patterns and genetic backgrounds. This study aims to examine the genetic landscape and clinical implications of rare mutations in Chinese breast cancer patients. Methods: Clinical data from 253 patients, including sporadic and familial cases, were analyzed. Comprehensive genomic profiling was performed, categorizing identified rare variants according to the American College of Medical Genetics (ACMG) guidelines. In silico protein modeling was used to analyze potentially pathogenic variants' impact on protein structure and function. Results: We detected 421 rare variants across patients. The most frequently mutated genes were ALK (22.2%), BARD1 (15.6%), and BRCA2 (15.0%). ACMG classification identified 7% of patients harboring Pathogenic/Likely Pathogenic (P/LP) variants, with one case displaying a pathogenic BRCA1 mutation linked to triple-negative breast cancer (TNBC). Also identified were two pathogenic MUTYH variants, previously associated with colon cancer but increasingly implicated in breast cancer. Variants of uncertain significance (VUS) were identified in 112 patients, with PTEN c.C804A showing the highest frequency. The role of these variants in sporadic breast cancer oncogenesis was suggested. In-depth exploration of previously unreported variants led to the identification of three potential pathogenic variants: ATM c.C8573T, MSH3 c.A2723T, and CDKN1C c.C221T. Their predicted impact on protein structure and stability suggests a functional role in cancer development. Conclusion: This study reveals a comprehensive overview of the genetic variants landscape in Chinese breast cancer patients, highlighting the prevalence and potential implications of rare variants. We emphasize the value of comprehensive genomic profiling in breast cancer management and the necessity of continuous research into understanding the functional impacts of these variants.

High PGAP3 expression is associated with lymph node metastasis and low CD8+T cell in patients with HER2+ breast cancer

BACKGROUND

Breast cancer (BC) stands as the most prevalent malignancy among women and ranks as the second most frequently diagnosed cancer globally among newly identified cases. Post-GPI attachment to proteins factor 3（PGAP3）was reported to involve in lipid remodeling. However, its specific role in breast cancer remains inadequately elucidated. Consequently, the principal objective of this study was to investigate the clinical significance of PGAP3 in breast cancer.

METHODS

We conducted an extensive analysis using both public databases and our own sample cohort to assess the role of PGAP3 in breast cancer. Immunohistochemistry was employed to assess PGAP3 expression, immune markers, and the co-expression of PGAP3 with key susceptibility genes. Data analysis was performed using the R programming language.

RESULTS

Our findings revealed that PGAP3 is significantly overexpressed in breast cancer, particularly in human epidermal growth factor 2 positive (HER2 +) breast cancer cases (p < 0.001). Co-expression analyses demonstrated a significant correlation between PGAP3 and susceptibility genes associated with breast cancer, including BRCA1, BRCA2, PALB2, ATM, CHEK2, RAD51C, and RAD51D (p < 0.05). Logistic regression analysis identified PGAP3 as a significant predictor of estrogen receptor (ER), progesterone receptor (PR), HER2, and lymph node metastasis status (p < 0.01). Furthermore, higher PGAP3 expression was associated with decreased infiltration of CD8 + T cells in breast cancer samples.

CONCLUSION

Our study sheds light on the clinical significance of PGAP3 in breast cancer. PGAP3 is not only overexpressed in breast cancer but also correlates with key susceptibility genes, lymph node metastasis, and CD8 + T cell infiltration. These findings provide valuable insights into the potential role of PGAP3 as a biomarker in breast cancer and may contribute to our understanding of the disease's pathogenesis.

Hsa_circ_0007823 Overexpression Suppresses the Progression of Triple-Negative Breast Cancer via Regulating miR-182-5p-FOXO1 Axis

Background

This study aimed to analyze the specific expression of hsa_circ_0007823 in triple-negative breast cancer (TNBC) and explore the roles and related molecular mechanisms of hsa_circ_0007823 in TNBC.

Materials and Methods

Relative hsa_circ_0007823 levels in TNBC tissues and cell lines were examined by reverse transcription-quantitative polymerase chain reaction. The value of hsa_circ_0007823 levels was evaluated in patients' clinicopathological characteristics and prognostic prediction. A dual-luciferase reporter assay was used to determine the relationship between hsa_circ_0007823, miR-182-5p, and FOXO1. The effect of circ_0007823 overexpression on the growth of TNBC cells was investigated in vitro and in vivo.

Results

Lower levels of hsa_circ_0007823 were found in TNBC tissues and cell lines and were closely associated with lymph node metastasis, poorer overall and disease-free survival rates. MiR-182-5p was significantly up-regulated, whereas FOXO1 was down-regulated in TNBC cell lines. The miR-182-5p inhibition up-regulated FOXO1 in TNBC cells. Dual-luciferase reporter assays showed that hsa_circ_0007823, miR-182-5p, and FOXO1 interacted with each other. Overexpression of circ_0007823 significantly inhibited the viability, migration, and invasion of TNBC cell lines, but promoted apoptosis. In vivo experiments showed that circ_0007823 overexpression inhibited tumor growth and down-regulated miR-182-5p and up-regulated FOXO1.

Conclusion

Hsa_circ_0007823 overexpression could suppress the growth, invasion, and migration of TNBC cells, and inhibit tumor growth by regulating miR-182-5p/FOXO1.

Individualizing Breast Cancer Risk Assessment in Clinical Practice

Multiple tools exist to assess a patient's breast cancer risk. The choice of risk model depends on the patient's risk factors and how the calculation will impact care. High-risk patients-those with a lifetime breast cancer risk of ≥20%-are, for instance, eligible for supplemental screening with breast magnetic resonance imaging. Those with an elevated short-term breast cancer risk (frequently defined as a 5-year risk ≥1.66%) should be offered endocrine prophylaxis. High-risk patients should also receive guidance on modification of lifestyle factors that affect breast cancer risk.

Surgical options for patients with early-stage breast cancer and pathogenic germline variants: an oncologist perspectives

Breast cancer continues to be the most common cancer diagnosed among women worldwide. Family history of breast cancer is frequently encountered, and 5-15% of patients may carry inherited pathogenic germline variants, identification of which can be helpful for both; patients themselves and their unaffected close relatives. The availability and affordability of molecular diagnostics, like next generation sequencing (NGS), had resulted in wider adoption of such technologies to detect pathogenic variants of cancer-predisposing genes. International guidelines had recently broadened the indications for germline genetic testing to include much more patients, and also expanded the testing to include multi-gene panels, while some professional societies are calling for universal testing of all newly diagnosed patients with breast cancer, regardless of their age, personal or family history. The risk of experiencing a contralateral breast cancer (CBC) or ipsilateral recurrence, is well known. Such risk is highest with variants like BRCA1 and BRCA2, but less well-studied with other less common variants. The optimal local therapy for women with BRCA-associated breast cancer remains controversial, but tends to be aggressive and may involve bilateral mastectomies, which may not have any survival advantage. Additionally, surgical management of unaffected women, known to carry a pathogenic cancer-predisposing gene, may vary from surveillance to bilateral mastectomies, too. The oncological safety, and the higher satisfaction of unaffected women and patients with new surgical techniques, like the skin-sparing (SSM) and nipple-sparing (NSM) mastectomies, eased up the process of counselling. In this review, we address the oncological safety of less aggressive surgical options for both; patients and unaffected carriers.

Multigene germline testing usefulness instead of BRCA1/2 single screening in triple negative breast cancer cases

Triple negative breast cancer is considered as the worst aggressive subtype with poor prognosis. Recent studies suggest a hereditary component is involved in TNBC development, especially in young patients. However, genetic spectrum remains unclear. Our purpose was to evaluate the usefulness of multigene panel testing in triple negative patients compared to overall breast cancer cases as well as contributing to elucidate which genes are most implicated in triple negative subtype development. Two breast cancer cohorts, comprising 100 triple negative breast cancer patients and 100 patients with other breast cancer subtypes, were analyzed by Next-Generation Sequencing using an On-Demand panel which included 35 predisposition cancer genes associated with inherited cancer susceptibility. The percentage of germline pathogenic variant carriers was higher in the triple negative cohort. ATM, PALB2, BRIP1 and TP53 were the most non-BRCA mutated genes. Moreover, triple negative breast cancer patients without family history related who were identified as carriers were diagnosed at significantly earlier age. As conclusion, our study reinforces the usefulness of multigene panel testing in breast cancer cases but specifically in those with triple negative subtype regardless family history.

Effect on Germline Mutation Rate in a High-Risk Chinese Breast Cancer Cohort after Compliance with The National Comprehensive Cancer Network (NCCN) 2023 v.1 Testing Criteria

BACKGROUND

The National Comprehensive Cancer Network (NCCN) testing criteria for the high-penetrance breast cancer susceptibility genes, specifically BRCA1, BRCA2, CDH1, PALB2, PTEN, and TP53, have been recently modified in 2023 to 2023 v.1. The following criteria have been changed: (1) from a person diagnosed with breast cancer at ≤45 to ≤50; (2) from aged 45-50 of personal breast diagnosis to any age of diagnosis with multiple breast cancers; and (3) from aged ≥51 of personal breast diagnosis to any age of diagnosis with family history listed in NCCN 2022 v.2.

METHODS

High-risk breast cancer patients (n = 3797) were recruited from the Hong Kong Hereditary Breast Cancer Family Registry between 2007 and 2022. Patients were grouped according to NCCN testing criteria 2023 v.1 and 2022 v.2. A 30-gene panel for hereditary breast cancer was performed. The mutation rates on high-penetrance breast cancer susceptibility genes were compared.

RESULTS

About 91.2% of the patients met the 2022 v.2 criteria, while 97.5% of the patients met the 2023 v.1 criteria. An extra 6.4% of the patients were included after the revision of the criteria, and 2.5% of the patients did not meet both testing criteria. The germline BRCA1/2 mutation rates for patients meeting the 2022 v.2 and 2023 v.1 criteria were 10.1% and 9.6%, respectively. The germline mutation rates of all 6 high-penetrance genes in these two groups were 12.2% and 11.6%, respectively. Among the additional 242 patients who were included using the new selection criteria, the mutation rates were 2.1% and 2.5% for BRCA1/2 and all 6 high-penetrance genes, respectively. Patients who did not meet both testing criteria were those with multiple personal cancers, a strong family history of cancers not listed in the NCCN, unclear pathology information, or the patient's voluntary intention to be tested. The mutation rates of BRCA1/2 and the 6 high-penetrance genes in these patients were 5.3% and 6.4%, respectively.

CONCLUSION

This study provided a real-world application of the revision of NCCN guidelines and its effect on the germline mutation rate in the Chinese population. Applying the updated criteria for further genetic investigation would increase the positive detection rate, and potentially more patients would benefit. The balance between the resource and outcome requires careful consideration.

Harnessing Epigenetics for Breast Cancer Therapy: The Role of DNA Methylation, Histone Modifications, and MicroRNA

Breast cancer exhibits various epigenetic abnormalities that regulate gene expression and contribute to tumor characteristics. Epigenetic alterations play a significant role in cancer development and progression, and epigenetic-targeting drugs such as DNA methyltransferase inhibitors, histone-modifying enzymes, and mRNA regulators (such as miRNA mimics and antagomiRs) can reverse these alterations. Therefore, these epigenetic-targeting drugs are promising candidates for cancer treatment. However, there is currently no effective epi-drug monotherapy for breast cancer. Combining epigenetic drugs with conventional therapies has yielded positive outcomes and may be a promising strategy for breast cancer therapy. DNA methyltransferase inhibitors, such as azacitidine, and histone deacetylase inhibitors, such as vorinostat, have been used in combination with chemotherapy to treat breast cancer. miRNA regulators, such as miRNA mimics and antagomiRs, can alter the expression of specific genes involved in cancer development. miRNA mimics, such as miR-34, have been used to inhibit tumor growth, while antagomiRs, such as anti-miR-10b, have been used to inhibit metastasis. The development of epi-drugs that target specific epigenetic changes may lead to more effective monotherapy options in the future.

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.

Role of detection of mutations in the <i>BRСA1,2</i>, <i>CHEK2</i>, <i>PALB2</i> genes in diagnosis of oncological diseases and determination of the therapy strategy

Breast cancer (BC) is the most common malignant neoplasm in women in the Russian Federation. Today, biological markers that characterize the individual characteristics of the tumor, such as the tendency to metastasize, hormonal sensitivity, are of great importance for the diagnosis and treatment of patients with breast cancer. Among the genes associated with hereditary breast cancer, there are genes with high penetrance (BRCA1, BRCA2, MLH1, MSH2, STK11, PTEN, TP53 and APC) and genes with moderate penetrance (CHEK2, ATM and PALB2). All of the listed above genes are responsible for DNA repair by homologous recombination, and they represent a group of HRR genes (homologous recombination-related genes). Mutations in the BRCA1 and BRCA2 genes can also initiate cancer of the ovaries, pancreas, and prostate. Understanding of the molecular and genetic nature of an oncological disease allows applying targeted drugs to therapy of a disease.

Genetically transitional disease: a new concept in genomic medicine

Traditional classification of genetic diseases as monogenic and polygenic has lagged far behind scientific progress. In this opinion article, we propose and define a new terminology, genetically transitional disease (GTD), referring to cases where a large-effect mutation is necessary, but not sufficient, to cause disease. This leads to a working disease nosology based on gradients of four types of genetic architecture: monogenic, polygenic, GTD, and mixed. We present four scenarios under which GTD may occur; namely, subsets of traditionally Mendelian disease, modifiable Tier 1 monogenic conditions, variable penetrance, and situations where a genetic mutational spectrum produces qualitatively divergent pathologies. The implications of the new nosology in precision medicine are discussed, in which therapeutic options may target the molecular cause or the disease phenotype.

Rs867228 in FPR1 accelerates the manifestation of luminal B breast cancer

Formyl peptide receptor-1 (FPR1) is a pathogen recognition receptor involved in the detection of bacteria, in the control of inflammation, as well as in cancer immunosurveillance. A single nucleotide polymorphism in FPR1, rs867228, provokes a loss-of-function phenotype. In a bioinformatic study performed on The Cancer Genome Atlas (TCGA), we observed that homo-or heterozygosity for rs867228 in FPR1 (which affects approximately one-third of the population across continents) accelerates age at diagnosis of specific carcinomas including luminal B breast cancer by 4.9 years. To validate this finding, we genotyped 215 patients with metastatic luminal B mammary carcinomas from the SNPs To Risk of Metastasis (SToRM) cohort. The first diagnosis of luminal B breast cancer occurred at an age of 49.2 years for individuals bearing the dysfunctional TT or TG alleles (n = 73) and 55.5 years for patients the functional GG alleles (n = 141), meaning that rs867228 accelerated the age of diagnosis by 6.3 years (p=0.0077, Mann & Whitney). These results confirm our original observation in an independent validation cohort. We speculate that it may be useful to include the detection of rs867228 in breast cancer screening campaigns for selectively increasing the frequency and stringency of examinations starting at a relatively young age.