Risk for breast cancer and management of unaffected individuals with non-BRCA hereditary breast cancer

Causative Genes of Homologous Recombination Deficiency (HRD)-Related Breast Cancer and Specific Strategies at Present

Recently, homologous recombination deficiency (HRD) has become a new target for hereditary cancers. Molecular-based approaches for hereditary cancers in the clinical setting have been reviewed. In particular, the efficacy of the PARP inhibitor has been considered by several clinical trials for various kinds of hereditary cancers. This indicates that the PARP inhibitor can be effective for any kind of BRCA mutated cancers, regardless of the organ-specific cancer. Homologous recombination deficiency (HRD) has become a new target for hereditary cancers, indicating the necessity to confirm the status of HRD-related genes. ARID1A, ATM, ATRX, PALB2, BARD1, RAD51C and CHEK2 are known as HRD-related genes for which simultaneous examination as part of panel testing is more suitable. Both surgical and medical oncologists should learn the basis of genetics including HRD. An understanding of the basic mechanism of homologous repair recombination (HRR) in BRCA-related breast cancer is mandatory for all surgical or medical oncologists because PARP inhibitors may be effective for these cancers and a specific strategy of screening for non-cancers exists. The clinical behavior of each gene should be clarified based on a large-scale database in the future, or, in other words, on real-world data. Firstly, HRD-related genes should be examined when the hereditary nature of a cancer is placed in doubt after an examination of the relevant family history. Alternatively, HRD score examination is a solution by which to identify HRD-related genes at the first step. If lifetime risk is estimated at over 20%, an annual breast MRI is necessary for high-risk screening. However, there are limited data to show its benefit compared with BRCA. Therefore, a large-scale database, including clinical information and a long-term follow-up should be established, after which a periodical assessment is mandatory. The clinical behavior of each gene should be clarified based on a large-scale database, or, in other words, real-world data.

A Global Regional Comparison of the Risk of Breast Cancer in Woman Using Oral Contraceptives-Systematic Review and Meta-Analysis

Background: Incidence of breast cancer (BrCa) may be correlated with country development, with a rise in cases anticipated in regions of the world that are currently undergoing an economic transformation. Herein, differences with regard to the occurrence of breast cancer between individual countries may depend on the distribution of risk factors, the level of early detection, also ethnicity and race, as well as clinical characteristics. The aim of our study was to identify and then investigate observational studies in which the risk of breast cancer was associated with the use of oral hormonal contraceptives (OCs), with particular emphasis on geographic region, and to conduct a systematic review and meta-analysis of the obtained data. Methods: RR (relative risk) was calculated and displayed in forest plots for visual interpretation. Accordingly, 74 studies involving a total of 198,579 women were eligible for inclusion in the meta-analysis. This is the first meta-analysis to comprehensively summarize the evidence between OC use and BrCa risk in connection with geographical region. Results: The cumulative results of the meta-analysis for specific parts of the world are: Africa (RR = 1.16, p = 0.216) and the Americas (RR = 1.03, p = 0.597); Asia (RR = 1.29, p = 0.014); European countries (RR = 1.01, p = 0.904); and Middle East countries (RR = 1.29, p = 0.043). Subgroup analyses showed an increased risk of BrCa for the analyzed variables that depended upon the geographical region. Conclusions: Our meta-analysis suggests that OC use may be associated with a higher BrCa risk, although a statistically significant association was not found for all geographical regions of the world.

BRCA2 and TP53 Mutations in a Breast Cancer Patient: A Case Report and Review of the Literature

Hereditary breast cancer (BC) accounts for 5-10% of all BC cases. Pathogenic or likely pathogenic germline variants in BRCA1 and BRCA2 genes are the most common cause of hereditary BC. However, other genes may also be involved, such as TP53, PALB2, PTEN, ATM, and CHEK2, among others. Multigene tests are essential in the treatment approach to young BC patients, since the detection of specific mutations may help guide changes in preventive measures and treatment plans. This report describes a rare case of BC in a young patient with pathogenic germline variants in BRCA2 and TP53 genes and also presents a literature review of the topic.

Screening Familial Risk for Hereditary Breast and Ovarian Cancer

Importance

Most patients with pathogenic or likely pathogenic (P/LP) variants for breast cancer have not undergone genetic testing.

Objective

To identify patients meeting family history criteria for genetic testing in the electronic health record (EHR).

Design, Setting, and Participants

This study included both cross-sectional (observation date, February 1, 2024) and retrospective cohort (observation period, January 1, 2018, to February 1, 2024) analyses. Participants included patients aged 18 to 79 years enrolled in Renown Health, a large health system in Northern Nevada. Genotype was known for 38 003 patients enrolled in Healthy Nevada Project (HNP), a population genomics study.

Exposure

An EHR indicating that a patient is positive for criteria according to the Seven-Question Family History Questionnaire (hereafter, FHS7 positive) assessing familial risk for hereditary breast and ovarian cancer (HBOC).

Main Outcomes and Measures

The primary outcomes were the presence of P/LP variants in the ATM, BRCA1, BRCA2, CHEK2, or PALB2 genes (cross-sectional analysis) or a diagnosis of cancer (cohort analysis). Age-adjusted cancer incidence rates per 100 000 patients per year were calculated using the 2020 US population as the standard. Hazard ratios (HRs) for cancer attributable to FHS7-positive status were estimated using cause-specific hazard models.

Results

Among 835 727 patients, 423 393 (50.7%) were female and 29 913 (3.6%) were FHS7 positive. Among those who were FHS7 positive, 24 535 (82.0%) had no evidence of prior genetic testing for HBOC in their EHR. Being FHS7 positive was associated with increased prevalence of P/LP variants in BRCA1/BRCA2 (odds ratio [OR], 3.34; 95% CI, 2.48-4.47), CHEK2 (OR, 1.62; 95% CI, 1.05-2.43), and PALB2 (OR, 2.84; 95% CI, 1.23-6.16) among HNP female individuals, and in BRCA1/BRCA2 (OR, 3.35; 95% CI, 1.93-5.56) among HNP male individuals. Being FHS7 positive was also associated with significantly increased risk of cancer among 131 622 non-HNP female individuals (HR, 1.44; 95% CI, 1.22-1.70) but not among 114 982 non-HNP male individuals (HR, 1.11; 95% CI, 0.87-1.42). Among 1527 HNP survey respondents, 352 of 383 EHR-FHS7 positive patients (91.9%) were survey-FHS7 positive, but only 352 of 883 survey-FHS7 positive patients (39.9%) were EHR-FHS7 positive. Of the 29 913 FHS7-positive patients, 19 764 (66.1%) were identified only after parsing free-text family history comments. Socioeconomic differences were also observed between EHR-FHS7-negative and EHR-FHS7-positive patients, suggesting disparities in recording family history.

Conclusions and Relevance

In this cross-sectional study, EHR-derived FHS7 identified thousands of patients with familial risk for breast cancer, indicating a substantial gap in genetic testing. However, limitations in EHR family history data suggested that other identification methods, such as direct-to-patient questionnaires, are required to fully address this gap.

Men with metastatic prostate cancer carrying a pathogenic germline variant in breast cancer genes: disclosure of genetic test results to relatives

Some patients with metastatic prostate cancer carry a pathogenic germline variant (PV) in a gene, that is mainly associated with an increased risk of breast cancer in women. If they test positive for such a PV, prostate cancer patients are encouraged to disclose the genetic test result to relatives who are at risk in case the carrier status changes the relatives' medical care. Our study aimed to investigate how men who learned they carry a PV in BRCA1, BRCA2, PALB2, CHEK2 or ATM disclosed their carrier status to at-risk relatives and to assess the possible psychological burden for the carrier and their perception of the burden for relatives. In total, 23 men with metastatic prostate cancer carrying a PV completed the IRI questionnaire about family communication; 14 also participated in a semi-structured interview. Patients felt highly confident in discussing the genetic test result with relatives. The diagnosis of prostate cancer was experienced as a burden, whereas being informed about genetic testing results did in most cases not add to this burden. Two patients encountered negative experiences with family communication, as they considered the genetic test result to be more urgent than their relatives. This mixed-methods study shows that metastatic prostate cancer patients with a PV in genes mainly associated with increased risk of breast cancer feel well-equipped to communicate about this predisposition in their families. Carriers felt motivated to disclose their genetic test result to relatives. Most of them indicated that the disclosure was not experienced as a psychological burden.

Patient-reported outcomes in bilateral prophylactic mastectomy with breast reconstruction: A narrative review

In women at high risk of developing breast cancer, bilateral prophylactic mastectomy (BPM) 1 significantly reduces the risk; simultaneously, breast reconstruction preserves body integrity. Given the complex and personal nature of such surgical procedures, patient assessment of satisfaction and health-related quality of life (HRQoL) 2 is essential in evaluation of surgical outcomes. With this review, we aim to organize the current knowledge on patient-reported outcomes (PROs) 3 in bilateral prophylactic surgery. Literature search was conducted using the databases Google Scholar, PubMed, and Web of Science to address the following questions, which can help clinicians and women undergoing the procedures navigate their healthcare decision-making process: How does BPM with reconstruction influence cancer-related distress? How does the surgery impact patient satisfaction and HRQoL? How do preoperative PROs differ from postoperative outcomes? Does the type of BPM and the type of reconstruction impact patient satisfaction and HRQoL? Furthermore, we summarize available patient-reported outcome measures (PROMs) 4 that can be administered to women undergoing BPM with reconstruction. In addition, we discuss possible future directions for PRO research in prophylactic breast surgery.

An apparent quandary: adoption of polygenics and gene panels for personalised breast cancer risk stratification

Over the past 30 years, genetic and epidemiological advances have revolutionised the prediction of breast cancer risk in women with significant family history. By screening these women for high- and intermediate-risk pathogenic variants and by interrogating their genomes for multiple lower-risk single-nucleotide polymorphisms (SNPs), we can provide individually tailored risk profiles in carriers of Mendelian breast cancer risk variants and in non-carriers, but clinical implementation of this approach is suboptimal. Risk mitigation may involve enhanced surveillance, preventive medications or risk-reducing surgery but barriers exist to the adoption of polygenic risk score (PRS)-based models in the clinic. PRS development has suffered from both systematic biases resulting from development and validation in those of European ancestry and from the consequences of unanticipated evolutionary differences particularly with regard to those of African ancestry. PRS approaches which take into account underlying genetic diversity offer a practical solution to the misapplication of European-derived PRS to other population groups including women of multiple ancestries. All ancestry PRS technology offers net benefit regardless of potency differences. While the new science of polygenics has surged ahead and its stratification insights have been incorporated into risk modelling, training of providers and genetic counsellors lags far behind and an educational revolution is also necessary to provide optimal patient care.

The Future of Breast Cancer Research in the Survivorship Field

Prevalence of survivors of breast cancer has been steadily increasing in the last 20 years. Currently, more than 90% of women diagnosed with early-stage breast cancer are expected to be alive at 5 years from diagnosis thanks to early detection and breakthrough innovations in multimodal treatment strategies. Alongside this advancement in clinical outcomes, survivors of breast cancer might experience several specific challenges and present with unique needs. Survivorship trajectories after diagnosis and treatment of breast cancer can be significantly impacted by long-lasting and severe treatment-related side effects, including physical problems, psychological distress, fertility issues in young women, and impaired social and work reintegration, which add up to patients' individual risk of cancer recurrence and second primary malignancies. Alongside cancer-specific sequelae, survivors still present with general health needs, including management of chronic preexisting or ensuing conditions. Survivorship care should implement high-quality, evidence-based strategies to promptly screen, identify, and address survivors' needs in a comprehensive way and minimize the impact of severe treatment sequelae, preexisting comorbidities, unhealthy lifestyles, and risk of recurrence on quality of life. This narrative review focuses on core areas of survivorship care and discuss the state of the art and future research perspectives in key domains including selected long-term side effects, surveillance for recurrences and second cancers, well-being promotion, and specific survivors' needs.

Breast cancer genetics and risk assessment: an overview for the clinician

Breast cancer is the most common cancer in women globally with enormous associated morbidity, mortality and economic impact. Prevention of breast cancer is a global public health imperative. To date, most of our global efforts have been directed at expanding population breast cancer screening programs for early cancer detection and not at breast cancer prevention efforts. It is imperative that we change the paradigm. As with other diseases, prevention of breast cancer starts with identification of individuals at high risk, and for breast cancer this requires improved identification of individuals who carry a hereditary cancer mutation associated with an elevated risk of breast cancer, and identification of others who are at high risk due to non-genetic, established modifiable and non-modifiable factors. This article will review basic breast cancer genetics and the most common hereditary breast cancer mutations associated with increased risk. We will also discuss the other non-genetic modifiable and non-modifiable breast cancer risk factors, available risk assessment models and an approach to incorporating screening for genetic mutation carriers and identifying high-risk women in clinical practice. A discussion of guidelines for enhanced screening, chemoprevention and surgical management of high-risk women is beyond the scope of this review.

Factors that influence the management recommendations breast surgeons provide to women with pathogenic variants in moderate penetrance breast cancer susceptibility genes

Pathogenic variants in moderate penetrance breast cancer susceptibility genes, such as ATM and CHEK2, confer a two- to five-fold increased lifetime risk for breast cancer. The National Comprehensive Cancer Network has guidelines for breast surgeons to utilize when counseling women with pathogenic variants in these genes; however, previous studies indicate that other factors impact breast surgeons' recommendations to patients. This study investigated factors influencing management recommendations presented by breast surgeons to women with pathogenic variants in moderate penetrance breast cancer susceptibility genes. Focus groups and interviews were conducted with breast surgeons practicing in Ohio, Kentucky, and Indiana. A total of 15 breast surgeons from eight different hospitals participated in five focus groups and three individual interviews. Participants discussed factors they consider when making management recommendations for risk reduction in women with pathogenic variants in moderate penetrance breast cancer susceptibility genes. Participants provided risk management recommendations for given scenarios. Patient motivation/opinion, family history, patient current health status, patient personal preference, and patient anxiety level were among the most common factors mentioned. It appeared that how these factors are valued and applied in practice varies. There was no consensus among breast surgeons on which risk-reducing management options they would recommend in each scenario. There are many factors breast surgeons take into consideration when making recommendations for this patient population. This information could inform future research on decision making around treatment for individuals with pathogenic variants in moderate penetrance breast cancer susceptibility genes.

Mainstream germline genetic testing in men with metastatic prostate cancer: design and protocol for a multicenter observational study

BACKGROUND

In international guidelines, germline genetic testing is recommended for patients with metastatic prostate cancer. Before undergoing germline genetic testing, these patients should receive pre-test counseling. In the standard genetic care pathway, pre-test counseling is provided by a healthcare professional of a genetics department. Because the number of patients with metastatic prostate cancer is large, the capacity in the genetics departments might be insufficient. Therefore, we aim to implement so-called mainstream genetic testing in the Netherlands for patients with metastatic prostate cancer. In a mainstream genetic testing pathway, non-genetic healthcare professionals discuss and order germline genetic testing. In our DISCOVER study, we will assess the experiences among patients and non-genetic healthcare professionals with this new pathway.

METHODS

A multicenter prospective observational cohort study will be conducted in 15 hospitals, in different regions of the Netherlands. We developed an online training module on genetics in prostate cancer and the counseling of patients. After completion of this module, non-genetic healthcare professionals will provide pre-test counseling and order germline genetic testing in metastatic prostate cancer patients. Both non-genetic healthcare professionals and patients receive three questionnaires. We will determine the experience with mainstream genetic testing, based on satisfaction and acceptability. Patients with a pathogenic germline variant will also be interviewed. We will determine the efficacy of the mainstreaming pathway, based on time investment for non-genetic healthcare professionals and the prevalence of pathogenic germline variants.

DISCUSSION

This study is intended to be one of the largest studies on mainstream genetic testing in prostate cancer. The results of this study can improve the mainstream genetic testing pathway in patients with prostate cancer.

TRIAL REGISTRATION

The study is registered in the WHO's International Clinical Trials Registry Platform (ICTRP) under number NL9617.

Breast Cancer Epidemiology and Contemporary Breast Cancer Care: A Review of the Literature and Clinical Applications

Substantial progress has been made in contemporary breast cancer care, resulting in a consistently declining breast cancer mortality rate and an improvement in quality of life. Advancements include deescalation of therapy in low-risk populations and refining systemic therapy options. Research into molecular biomarkers continues to evolve and holds the promise of achieving the goal of precision medicine, while guidelines for supportive care and survivorship have been created to address the needs of an ever-increasing number of breast cancer survivors. A collaborative, multidisciplinary team approach is essential for patients and survivors to achieve optimal outcomes and enjoy productive high-quality lives. Gynecologists, in particular, play a key role in screening and survivorship care.

Germline Cancer Susceptibility Gene Testing in Unselected Patients With Colorectal Adenocarcinoma: A Multicenter Prospective Study

BACKGROUND & AIMS

Hereditary factors play a role in the development of colorectal cancer (CRC). Identification of germline predisposition can have implications on treatment and cancer prevention. This study aimed to determine the prevalence of pathogenic germline variants (PGVs) in CRC patients using a universal testing approach, association with clinical outcomes, and the uptake of family variant testing.

METHODS

We performed a prospective multisite study of germline sequencing using a more than 80-gene next-generation sequencing platform among CRC patients (not selected for age or family history) receiving care at Mayo Clinic Cancer Centers between April 1, 2018, and March 31, 2020.

RESULTS

Of 361 patients, the median age was 57 years (SD, 12.4 y), 43.5% were female, 82% were white, and 38.2% had stage IV disease. PGVs were found in 15.5% (n = 56) of patients, including 44 in moderate- and high-penetrance cancer susceptibility genes. Thirty-four (9.4%) patients had incremental clinically actionable findings that would not have been detected by practice guideline criteria or a CRC-specific gene panel. Only younger age at diagnosis was associated with the presence of PGVs (odds ratio, 1.99; 95% CI, 1.12-3.56). After a median follow-up period of 20.7 months, no differences in overall survival were seen between those with or without a PGV (P = .2). Eleven percent of patients had modifications in their treatment based on genetic findings. Family cascade testing was low (16%).

CONCLUSIONS

Universal multigene panel testing in CRC was associated with a modest, but significant, detection of heritable mutations over guideline-based testing. One in 10 patients had changes in their management based on test results. Uptake of cascade family testing was low, which is a concerning observation that warrants further study.

Concurrent pathogenic variations in patients with hereditary cancer syndromes

Cancer is a multifactorial disorder; however, 5-10% of all cancers show hereditary background. In recent years many targeted next generation sequencing panels comprising cancer predisposition genes have been developed and used for diagnostic purposes in patients with increased cancer risk. Screening multiple genes at a time allows multiple variants in different genes to be detected as well. This study aims to determine the cases with concurrent mutations in different hereditary cancer predisposition genes and how they are clinically affected. Here, we screened 1090 index cases by next generation sequencing based hereditary cancer panels and evaluated the reflection of multiple variations on the phenotype. We detected 11 (1%) cases with pathogenic variants in more than one gene. These concurrent variations occurred mostly in BRCA1/2 (7/11) accompanied with MUTYH, ATM, CHECK2, NBN, and RAD50. In addition, MUTYH&ATM, NBN&MSH6, MUTYH&CHEK2 double heterozygous cases were detected. Moreover, we identified a case with three heterozygous variations in CDH1, MUTYH, and CHEK2. These patients presented malignancies that were mostly related to pathogenic variations they carried. Although they are rare, defining double heterozygous cases is important for managing appropriate therapy and accurate genetic consulting for the patients and family members.

Breast cancer: Muscarinic receptors as new targets for tumor therapy

The development of breast cancer is a complex process that involves the participation of different factors. Several authors have demonstrated the overexpression of muscarinic acetylcholine receptors (mAChRs) in different tumor tissues and their role in the modulation of tumor biology, positioning them as therapeutic targets in cancer. The conventional treatment for breast cancer involves surgery, radiotherapy, and/or chemotherapy. The latter presents disadvantages such as limited specificity, the appearance of resistance to treatment and other side effects. To prevent these side effects, several schedules of drug administration, like metronomic therapy, have been developed. Metronomic therapy is a type of chemotherapy in which one or more drugs are administered at low concentrations repetitively. Recently, two chemotherapeutic agents usually used to treat breast cancer have been considered able to activate mAChRs. The combination of low concentrations of these chemotherapeutic agents with muscarinic agonists could be a useful option to be applied in breast cancer treatment, since this combination not only reduces tumor cell survival without affecting normal cells, but also decreases pathological neo-angiogenesis, the expression of drug extrusion proteins and the cancer stem cell fraction. In this review, we focus on the previous evidences that have positioned mAChRs as relevant therapeutic targets in breast cancer and analyze the effects of administering muscarinic agonists in combination with conventional chemotherapeutic agents in a metronomic schedule.

Co-occurrence of germline pathogenic variants for different hereditary cancer syndromes in patients with Lynch syndrome

BACKGROUND

Lynch syndrome (LS) is a hereditary condition characterized by a high risk of colorectal cancer, endometrial cancer, and other neoplasia associated with germline alterations in DNA mismatch repair genes. The classical genetic diagnostic strategy for LS consists of the Sanger sequencing of genes associated with the suspected syndrome. Next-generation sequencing (NGS) enables the simultaneous sequencing of a large number of hereditary cancer genes. Here, we aimed to study whether other germline pathogenic variants of hereditary cancer genes are present in patients with LS.

METHODS

A cohort of 84 probands with a previous genetic diagnosis of LS by Sanger sequencing was reanalyzed using NGS via a commercial panel of 94 hereditary cancer genes by hybrid capture. The American College of Medical Genetics and Genomics criteria were used to classify the clinical significance of the variants. The findings of NGS were confirmed by Sanger sequencing. When possible, genetic analyses of the new findings in the proband's relatives were also performed by Sanger sequencing.

RESULTS

We identified five families (6%), out of 84, with at least two germline pathogenic variants conferring to high or moderate risk in different dominant cancer-predisposing genes: [MLH1-BRCA2-NBN], [MLH1-BRCA1], [MSH2-ATM], [MSH6-NF1], and [MLH1-FANCA]. Interestingly, only one out of these five families exhibited a clinical phenotype associated with the new pathogenic variants. The family with three pathogenic variants of the [MLH1-BRCA2-NBN] genes showed a high aggregation of tumors associated with LS and breast and ovarian cancer syndrome.

CONCLUSIONS

Our results showed that the co-occurrence of more than one pathogenic variant in cancer-predisposing genes was remarkable among cases of LS. In most cases, no clinicial manifestations were associated with the secondary pathogenic variants. Further studies are needed to confirm these findings and elucidate their clinical impact. Reanalysis of LS families should be considered only in families with mixed clinical phenotypes.

How Have Multigene Panels Changed the Clinical Practice of Genetic Counseling and Testing

Historically, genetic testing (and billing) for hereditary cancer risk was essentially performed gene by gene, with clinicians ordering testing only for the genes most likely to explain a patient's or family's cancer presentation, with laboratories typically charging $1,000 to $1,500 for each gene that was sequenced. Given the expense, only patients at high risk of having a hereditary syndrome were offered testing. With the introduction of next-generation sequencing technologies, however, laboratories are able to test for multiple genes at the same time with greater efficiency, significantly decreased costs, and relatively little increased expense when adding additional genes. This has drastically altered clinical practice so that clinicians now typically order testing for a panel of multiple genes for most patients. Although this approach has streamlined the diagnostic odyssey, it has introduced several problems, as well, including difficulties in choosing the appropriate panel test for a given patient, assessing the significance of identified genetic variants (including variants of uncertain significance [VUS]), and understanding the disease risks and management associated with pathogenic variants in a given gene. Many laboratories offer testing for genes that have limited data supporting their associated cancer risks, which then leads to an inability to set management guidelines based on that gene. In addition, testing larger numbers of genes increases the likelihood of finding one or more VUS, which introduce their own management issues. Thus, although panel testing has certainly moved clinical practice forward in many ways, it has also raised its own set of problems that increase the complexity of genetic counseling and highlight the need for education of community practitioners on the complexities and nuances of this testing. Whenever possible, testing should be performed by, or in consultation with, cancer genetics professionals.

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.