Therapeutic targeting of the DNA damage response in prostate cancer

PURPOSE OF REVIEW

The present article highlights the most common DNA repair gene mutations, using specific examples of individual genes or gene classes, and reviews the epidemiology and treatment implications for each one [with particular emphasis on poly-ADP-ribose polymerase (PARP) inhibition and PD-1 blockade].

RECENT FINDINGS

Genetic and genomic testing have an increasingly important role in the oncology clinic. For patients with prostate cancer, germline genetic testing is now recommended for all men with high-risk and metastatic disease, and somatic multigene tumor testing is recommended for men with metastatic castration-resistant disease. The most common mutations that are present in men with advanced prostate cancer are in genes coordinating DNA repair and the DNA damage response.

SUMMARY

Although much of what is discussed currently remains investigational, it is clear that genomically-targeted treatments will become increasingly important for patients with prostate cancer in the near future and beyond.

The association between the methylation frequency of BRCA1/2 gene promoter and occurrence and prognosis of breast carcinoma: A meta-analysis

OBJECTIVES

Breast cancer susceptibility gene 1/2 (BRCA1/2) is a promising tumor marker in many types of cancer. However, the methylation frequency of BRCA1/2 gene with occurrence risk and survival benefit of patients with breast carcinoma remains controversy. The aim of the present study was to assess the relationship between BRCA1/2 gene promoter methylation and the occurrence and prognosis in breast carcinoma based on a meta-analysis, meanwhile, this article explored the differential expression levels of BRCA1/2 gene promoter methylation in peripheral blood and tumor tissues of breast cancer patients.

METHODS

Electronic databases (PubMed, Medline, Cochrane Library, and CNKI) were searched up to June 2019. The number of BRCA1/2 promoter methylation-positive and -negative patients in breast carcinoma patients were measured, and hazard ratio (HR) with 95% confidence interval (CI) for the association between BRCA1/2 gene promoter methylation and the prognosis of breast carcinoma patients. Primary end points were presence of breast cancer, overall survival (OS), disease-free survival (DFS). Statistical analysis was performed with STATA 12.0.

RESULTS AND CONCLUSIONS

Fifty-eight articles including 19,084 individuals met full eligibility criteria. We observed that the frequency of BRCA1 gene promoter methylation was higher in breast cancer tissues compared with normal tissues, and the prognostic analysis suggested that BRCA1 gene promoter methylation was significantly associated with poor overall survival and poor disease-free survival. This study also verified that there was no statistically significant difference in the methylation frequency of BRCA1 gene promoter between peripheral blood and tumor tissues in breast cancer patients, which suggests that the detection of BRCA1 promoter methylation in peripheral blood may be a non-invasive and rapid way to monitor the occurrence breast cancer.

What Black Women Know and Want to Know About Counseling and Testing for BRCA1/2

Black women are just as likely to have hereditary breast cancer mutations as White women, yet their participation in genetic counseling and testing is substantially lower. This study sought to describe Black women's awareness and perceptions of BRCA1/2 testing and to identify barriers and motivators to seeking BRCA1/2 services. Fifty intercept interviews were conducted with Black women in public places (a professional women's basketball game, a grocery store, a faith-based community event, and the waiting area at a breast care clinic) in Washington, DC. More than half of the women (54%) were aware that genetic tests to determine risk for certain breast and ovarian cancers exist, but the majority (88%) had never heard of BRCA1/2, specifically. After hearing a description of BRCA1/2 genetic markers, 82% stated that they would agree to BRCA1/2 testing if it was offered to them. Perceived advantages of testing included cancer prevention and the ability to share information with family members. Perceived disadvantages included emotional distress associated with identification of the mutation and the potential misuse of results to deny healthcare or employment. Physician recommendation, self-care, and known family history were among the motivators for testing. Women listed possible media and venues for intervention. In spite of low rates of BRCA1/2 testing in the Black community, women in this sample were open to the idea. Interventions that address barriers and include cultural tailoring are necessary.

Methodological quality of English-language genetic guidelines on hereditary breast-cancer screening and management: an evaluation using the AGREE instrument

BACKGROUND

We examined the methodological quality of guidelines on syndromes conferring genetic susceptibility to breast cancer.

METHODS

PubMed, EMBASE, and Google were searched for guidelines published up to October 2010. All guidelines in English were included. The Appraisal of Guidelines, Research and Evaluation (AGREE) instrument was used to assess the quality of the guidelines, and their reported evidence base was evaluated.

RESULTS

Thirteen guidelines were deemed eligible: seven had been developed by independent associations, and the other six had national/state endorsements. Four guidelines performed satisfactorily, achieving a score of greater than 50% in all six AGREE domains. Mean ± SD standardized scores for the six AGREE domains were: 90 ± 9% for 'scope and purpose', 51 ± 18% for 'stakeholder involvement', 55 ± 27% for 'rigour of development', 80 ± 11% for 'clarity and presentation', 37 ± 32% for 'applicability', and 47 ± 38% for 'editorial independence'. Ten of the thirteen guidelines were found to be based on research evidence.

CONCLUSIONS

Given the ethical implications and the high costs of genetic testing for hereditary breast cancer, guidelines on this topic should provide clear and evidence-based recommendations. Our analysis shows that there is scope for improving many aspects of the methodological quality of current guidelines. The AGREE instrument is a useful tool, and could be used profitably by guidelines developers to improve the quality of recommendations.

Breast cancer genetic counselling referrals: how comparable are the findings between the UK and the Netherlands?

Counselees from different countries may differ in demographic and medical characteristics and this could affect their pre-counselling cognitions and psychosocial variables. Research outcomes may therefore not be easily transferable between countries. To examine this, a cross-national comparison of UK (West Midlands: WM) and Dutch (Middle Netherlands: MN) counselees in breast cancer genetic counselling was conducted. Two hundred thirty-eight WM and 156 MN proband counselees were compared on demographics, breast cancer history and referral pathways. Multivariate logistic regression analyses were performed to check whether national differences in knowledge of breast cancer and heredity, risk perception, worry and information needs persisted when corrected for the background characteristics. About half of the Dutch compared to 8% of UK counselees were affected by breast cancer. More UK than Dutch counselees were at high risk from hereditary breast cancer. UK counselees had higher risk perceptions and more knowledge about breast cancer prevalence, but these differences lost significance when corrected for counselees' risk levels and other background characteristics. Counselees from the UK might report higher levels of worry than Dutch counselees and this could not be explained by their background characteristics. Comparisons of findings between the UK and the Netherlands show that the UK seems to have a higher percentage of high-risk referrals and these counselees seem to have higher risk perceptions. Irrespective of their actual risk level, UK counselees might be more worried. Comparing findings between the different countries raises questions about how transferable research findings are from one culture to another.

TGFBR1 signaling and breast cancer

Over the past decade mutations discovered in genes such as BRCA1, BRCA2, TP53 and PTEN, have emerged as high-penetrance susceptibility genes and are clinically relevant for determination of breast cancer risk. Genetic counseling and subsequent screening for mutations and gene rearrangement has improved patient outcome through early detection and prophylactic interventions in patients with familial breast cancer syndromes. However, these high-penetrance genes only account for a small fraction of the hereditary linked breast cancers. It is currently believed that low-penetrance susceptibility alleles and/or environmental factors may play an important role in the remaining cases. TGFBR1*6A (*6A) is a common hypomorphic variant of the type I TGF-β receptor gene (TGFBR1) that has been associated with risk for several forms of cancer, in particular breast cancer. Several epidemiological studies have suggested that patients who carry the *6A allele have an increased risk of breast cancer. Furthermore, functional analysis suggests that this mutation alters TGF-β signaling and promotes tumorigenesis. Although a decade of research has provided basic information in regards to the prevalence of this mutation in several cancer types and populations the molecular underpinning of its functional effects are poorly understood. A better understanding of the molecular mechanism of TGFBR1 signaling in breast cancer may have an impact on breast cancer risk assessment and breast cancer prevention.

Diffusion of breast cancer risk assessment in primary care

BACKGROUND

Physicians who provide primary care to women have the opportunity to identify patients at high risk for breast cancer who are candidates for risk reduction strategies. Our objective was to determine the prevalence and determinants of the adoption of breast cancer risk assessment by primary care physicians.

METHODS

A cross-sectional survey of a nationally representative random sample of 351 internists, family practitioners, and obstetricians-gynecologists. We used a questionnaire that assessed knowledge, attitudes, discussion of breast cancer risk, use of software to calculate breast cancer risk, and ordering of BRCA1/2 testing.

RESULTS

Eighty-eight percent of physicians reported discussing breast cancer risk at least once during the previous 12 months; 48% had ordered or referred a patient for BRCA1/2 testing; and 18% had used a software program to calculate breast cancer risk. Physicians who had used BRCA1/2 testing or discussed breast cancer risk factors were more likely to be obstetrician-gynecologists and not in a solo practice; the use of risk software was also more common among obstetrician-gynecologists but was also associated with having a family member with breast cancer and a greater knowledge about breast cancer risk. Having patients ask for risk information was associated with the discussion of risk factors but not with the other risk assessment strategies.

CONCLUSIONS

Diffusion of breast cancer risk assessment is occurring in primary care practices, with a greater adoption of BRCA1/2 testing than of the use of risk assessment software. Adoption of these strategies seems to be related to the salience of breast cancer personally (for the physician) and within the practice, as well as the size of the practice, rather than attitudes about the risk assessment methods.

Glutathione-S-transferase M1, T1 and P1 polymorphisms, and breast cancer risk, in BRCA1/2 mutation carriers

Variation in penetrance estimates for BRCA1/2 carriers suggests that other environmental and genetic factors may modify cancer risk in carriers. The GSTM1, T1 and P1 isoenzymes are involved in metabolism of environmental carcinogens. The GSTM1 and GSTT1 gene is absent in a substantial proportion of the population. In GSTP1, a single-nucleotide polymorphism that translates to Ile112Val was associated with lower activity. We studied the effect of these polymorphisms on breast cancer (BC) risk in BRCA1/2 carriers. A population of 320 BRCA1/2 carriers were genotyped; of them 262 were carriers of one of the three Ashkenazi founder mutations. Two hundred and eleven were affected with BC (20 also with ovarian cancer (OC)) and 109 were unaffected with BC (39 of them had OC). Risk analyses were conducted using Cox proportional hazard models adjusted for origin (Ashkenazi vs non-Ashkenazi). We found an estimated BC HR of 0.89 (95% CI 0.65-1.12, P=0.25) and 1.11 (95% CI 0.81-1.52, P=0.53) for the null alleles of GSTM1 and GSTT1, respectively. For GSTP1, HR for BC was 1.36 (95% CI 1.02-1.81, P=0.04) for individuals with Ile/Val, and 2.00 (95% CI 1.18-3.38) for carriers of the Val/Val genotype (P=0.01). An HR of 3.20 (95% CI 1.26-8.09, P=0.01), and younger age at BC onset (P=0.2), were found among Val/Val, BRCA2 carriers, but not among BRCA1 carriers. In conclusion, our results indicate significantly elevated risk for BC in carriers of BRCA2 mutations with GSTP1-Val allele with dosage effect, as implicated by higher risk in homozygous Val carriers. The GSTM1- and GSTT1-null allele did not seem to have a major effect.

How do women decide? Accepting or declining BRCA1/2 testing in a nationwide clinical sample in the United States

OBJECTIVE

To examine the role of the practitioner, informed consent, and genetic counseling in genetic testing decisions and to assess their relative influence on women's decision to have clinical BRCA1/2 testing.

METHODS

Qualitative study using in-depth open-ended interviews with 68 women who had considered clinical BRCA1/2 testing.

RESULTS

Slightly less than half of the women who had considered BRCA1/2 testing were found to have had a clear and preexisting desire to test or not to test, irrespective of practitioner attitude or advice.

CONCLUSION

The decision to accept or decline genetic testing is the result of a complex process that goes beyond interactions between health care providers and patients, indicating a caution against exclusive reliance on informed consent or counseling encounters.