Genetic susceptibility to breast cancer

Patient decision aids in mainstreaming genetic testing for women with ovarian cancer: A prospective cohort study

OBJECTIVE

To evaluate patient preference for short (gist) or detailed/extensive decision aids (DA) for genetic testing at ovarian cancer (OC) diagnosis.

DESIGN

Cohort study set within recruitment to the Systematic Genetic Testing for Personalised Ovarian Cancer Therapy (SIGNPOST) study (ISRCTN: 16988857).

SETTING

North-East London Cancer Network (NELCN) population.

POPULATION/SAMPLE

Women with high-grade non-mucinous epithelial OC.

METHODS

A more detailed DA was developed using patient and stakeholder input following the principles/methodology of IPDAS (International Patients Decision Aids Standards). Unselected patients attending oncology clinics evaluated both a pre-existing short and a new long DA version and then underwent mainstreaming genetic testing by a cancer clinician. Appropriate inferential descriptive and regression analyses were undertaken.

MAIN OUTCOME MEASURES

Satisfaction, readability, understanding, emotional well-being and preference for long/short DA.

RESULTS

The mean age of patients was 66 years (interquartile range 11), and 85% were White British ethnicity. Of the participants, 74% found DAs helpful/useful in decision-making. Women reported higher levels of satisfaction (86% versus 58%, p < 0.001), right amount of information provided (76.79% versus49.12%, p < 0.001) and improved understanding (p < 0.001) with the long DA compared with the short DA. There was no statistically significant difference in emotional outcomes (feeling worried/concerned/reassured/upset) between 'short' and 'long' DA; 74% of patients preferred the long DA and 24% the short DA. Patients undergoing treatment (correlation coefficient (coef) = 0.603; 95% CI 0.165-1.041, p = 0.007), those with recurrence (coef = 0.493; 95% CI 0.065-0.92, p = 0.024) and older women (coef = 0.042; 95% CI 0.017-0.066, p = 0.001) preferred the short DA. Ethnicity did not affect outcomes or overall preference for long/short DA.

CONCLUSIONS

A longer DA in OC patients has higher satisfaction without increasing emotional distress. Older women and those undergoing treatment/recurrence prefer less extensive information, whereas those in remission preferred a longer DA.

Dysregulation of deubiquitination in breast cancer

Breast cancer (BC) is a highly frequent malignant tumor that poses a serious threat to women's health and has different molecular subtypes, histological subtypes, and biological features, which act by activating oncogenic factors and suppressing cancer inhibitors. The ubiquitin-proteasome system (UPS) is the main process contributing to protein degradation, and deubiquitinases (DUBs) are reverse enzymes that counteract this process. There is growing evidence that dysregulation of DUBs is involved in the occurrence of BC. Herein, we review recent research findings in BC-associated DUBs, describe their nature, classification, and functions, and discuss the potential mechanisms of DUB-related dysregulation in BC. Furthermore, we present the successful treatment of malignant cancer with DUB inhibitors, as well as analyzing the status of targeting aberrant DUBs in BC.

Comprehensive genomic profiling of breast cancers characterizes germline-somatic mutation interactions mediating therapeutic vulnerabilities

Germline-somatic mutation interactions are universal and associated with tumorigenesis, but their role in breast cancer, especially in non-Caucasians, remains poorly characterized. We performed large-scale prospective targeted sequencing of matched tumor-blood samples from 4079 Chinese females, coupled with detailed clinical annotation, to map interactions between germline and somatic alterations. We discovered 368 pathogenic germline variants and identified 5 breast cancer DNA repair-associated genes (BCDGs; BRCA1/BRCA2/CHEK2/PALB2/TP53). BCDG mutation carriers, especially those with two-hit inactivation, demonstrated younger onset, higher tumor mutation burden, and greater clinical benefits from platinum drugs, PARP inhibitors, and immune checkpoint inhibitors. Furthermore, we leveraged a multiomics cohort to reveal that clinical benefits derived from two-hit events are associated with increased genome instability and an immune-activated tumor microenvironment. We also established an ethnicity-specific tool to predict BCDG mutation and two-hit status for genetic evaluation and therapeutic decisions. Overall, this study leveraged the large sequencing cohort of Chinese breast cancers, optimizing genomics-guided selection of DNA damaging-targeted therapy and immunotherapy within a broader population.

Circulating tumor biomarkers in early-stage breast cancer: characteristics, detection, and clinical developments

Breast cancer is the most common form of cancer in women, contributing to high rates of morbidity and mortality owing to the ability of these tumors to metastasize via the vascular system even in the early stages of progression. While ultrasonography and mammography have enabled the more reliable detection of early-stage breast cancer, these approaches entail high rates of false positive and false negative results Mammograms also expose patients to radiation, raising clinical concerns. As such, there is substantial interest in the development of more accurate and efficacious approaches to diagnosing breast cancer in its early stages when patients are more likely to benefit from curative treatment efforts. Blood-based biomarkers derived from the tumor microenvironment (TME) have frequently been studied as candidate targets that can enable tumor detection when used for patient screening. Through these efforts, many promising biomarkers including tumor antigens, circulating tumor cell clusters, microRNAs, extracellular vesicles, circulating tumor DNA, metabolites, and lipids have emerged as targets that may enable the detection of breast tumors at various stages of progression. This review provides a systematic overview of the TME characteristics of early breast cancer, together with details on current approaches to detecting blood-based biomarkers in affected patients. The limitations, challenges, and prospects associated with different experimental and clinical platforms employed in this context are also discussed at length.

Potential of chimeric antigen receptor (CAR)-redirected immune cells in breast cancer therapies: Recent advances

Despite substantial developments in conventional treatments such as surgery, chemotherapy, radiotherapy, endocrine therapy, and molecular-targeted therapy, breast cancer remains the leading cause of cancer mortality in women. Currently, chimeric antigen receptor (CAR)-redirected immune cell therapy has emerged as an innovative immunotherapeutic approach to ameliorate survival rates of breast cancer patients by eliciting cytotoxic activity against cognate tumour-associated antigens expressing tumour cells. As a crucial component of adaptive immunity, T cells and NK cells, as the central innate immune cells, are two types of pivotal candidates for CAR engineering in treating solid malignancies. However, the biological distinctions between NK cells- and T cells lead to differences in cancer immunotherapy outcomes. Likewise, optimal breast cancer removal via CAR-redirected immune cells requires detecting safe target antigens, improving CAR structure for ideal immune cell functions, promoting CAR-redirected immune cells filtration to the tumour microenvironment (TME), and increasing the ability of these engineered cells to persist and retain within the immunosuppressive TME. This review provides a concise overview of breast cancer pathogenesis and its hostile TME. We focus on the CAR-T and CAR-NK cells and discuss their significant differences. Finally, we deliver a summary based on recent advancements in the therapeutic capability of CAR-T and CAR-NK cells in treating breast cancer.

Breast cancer in the era of precision medicine

Breast cancer is a heterogeneous disorder with different molecular subtypes and biological characteristics for which there are diverse therapeutic approaches and clinical outcomes specific to any molecular subtype. It is a global health concern due to a lack of efficient therapy regimens that might be used for all disease subtypes. Therefore, treatment customization for each patient depending on molecular characteristics should be considered. Precision medicine for breast cancer is an approach to diagnosis, treatment, and prevention of the disease that takes into consideration the patient's genetic makeup. Precision medicine provides the promise of highly individualized treatment, in which each individual breast cancer patient receives the most appropriate diagnostics and targeted therapies based on the genetic profile of cancer. The knowledge about the molecular features and development of breast cancer treatment approaches has increased, which led to the development of new targeted therapeutics. Tumor genomic profiling is the standard of care for breast cancer that could contribute to taking steps to better management of malignancies. It holds great promise for accurate prognostication, prediction of response to common systemic therapies, and individualized monitoring of the disease. The emergence of targeted treatment has significantly enhanced the survival of patients with breast cancer and contributed to reducing the economic costs of the health system. In this review, we summarized the therapeutic approaches associated with the molecular classification of breast cancer to help the best treatment selection specific to the target patient.

Making Biomarkers Relevant to Healthcare Innovation and Precision Medicine

Translational medicine, the exchange between laboratory (bench) and the clinic (bedside), is decidedly taking on a vital role. Many companies are now focusing on a translational medicinal approach as a therapeutic strategy in decision making upon realizing the expenses of drug attrition in late-stage advancement. In addition, the utility of biomarkers in clinical decision and therapy guidance seeks to improve the patient outcomes and decrease wasteful and harmful treatment. Efficient biomarkers are crucial for the advancement of diagnoses, better molecular targeted therapy, along with therapeutic advantages in a broad spectrum of various diseases. Despite recent advances in the discovery of biomarkers, the advancement route to a clinically validated biomarker remains intensely challenging, and many of the candidate biomarkers do not progress to clinical applications, thereby widening the innovation gap between research and application. The present article will focus on the clinical view of biomarkers in a reverse design, addressing how a biomarker program should appear if it is expected to create an impact on personalized medicine and patient care.

Germline mutations in Chinese ovarian cancer with or without breast cancer

BACKGROUND

Ovarian and breast cancers are known to have significant genetic components. Considering the differences in the mutation spectrum across ethnicity, it is important to identify hereditary breast and ovarian cancer (HBOC) genes mutation in Chinese for clinical management.

METHODS

Two cohorts of 451 patients with ovarian cancer only (OV) and 93 patients with both breast and ovarian (BROV) cancers were initially screened for BRCA1, BRCA2, TP53, and PTEN. 109 OV and 43 BROV patients with extensive clinical risk and were being tested negative, were then further characterized by 30-gene panel analysis.

RESULTS

Pathogenic BRCA1/2 variants were identified in 45 OV patients and 33 BROV patients, giving a prevalence of 10% and 35.5%, respectively. After the extended screening, mutations in other HBOC genes were identified in an additional 12.8% (14/109) of the OV cohort and 14% (6/43) in the BROV cohort. The most commonly mutated genes in the OV cohort were MSH2 (4.6%) while in the BROV cohort were MSH2 (4.7%) and PALB2 (4.7%). With this extended multigene testing strategy, pathogenic mutations were detected in 12.8% of OV patients (BRCAs: 10%; additional genes: 12.8%) and 40.9% (BRCAs: 35.5%; additional genes: 14%) of BROV patients.

CONCLUSION

Extended characterization of the contributions of HBOC genes to OV and BROV patients has significant impacts on further management in patients and their families, expanding the screening net for more asymptomatic individuals.

Breast cancer burden in Africa: evidence from GLOBOCAN 2018

BACKGROUND

Breast cancer is the leading malignancy in African females. This study aims to examine the breast cancer burden in Africa using recently released GLOBOCAN 2018 estimates.

METHODS

The incidence and mortality estimates of age- and country-wise burden of breast cancer in 54 African countries were obtained from GLOBOCAN 2018.

RESULTS

In Africa, breast cancer caused 74 072 deaths, and 168 690 cases were estimated to have occurred in 2018. The age-standardized incidence rate stood at 37.9/100 000 in Africa, varying from 6.9/100 000 in the Gambia to 69.6/100 000 in Mauritius. The age-standardized mortality rate stood at 17.2/100 000 in 2018, ranging from 4/100 000 in the Gambia to 29.1/100 000 in Somalia in 2018. Nigeria was the leading country in terms of absolute burden with 26 310 cases and 11 564 deaths, followed by Egypt with 23 081 new cases and 9254 deaths. The mortality-to-incidence ratio for Africa stood at 0.44, varying from 0.24 in Libya to 0.68 in the Central African Republic.

CONCLUSION

To tackle breast cancer burden in Africa, the main challenges are late-stage disease presentation, lack of screening and therapeutic infrastructure, lack of awareness and limited resources.

An overview on breast cancer genetics and recent innovations: Literature survey

Breast cancer is one of the leading cancers nowadays. The genetical mechanism behind breast cancer development is an intricate one. In this review, the genetical background of breast cancer, particularly BRCA 1 and BRCA 2 had been included. Moreover, to summarize the genetics of breast cancer, the recent and ongoing preclinical and clinical studies on the treatment of BRCA-associated breast cancer had also been included. A prime knowledge is that the BRCA gene is the basis of breast cancer risk. How it mediates cell proliferation and associated mechanisms are reviewed here. BRCA 1 gene can influence all phases of the cell cycle and regulate cell cycle progression. BRCA 1 gene can also respond to DNA damages and induce responsive mechanisms. The action of the BRCA gene on associated protein has a wide consideration in breast cancer development. Heterogeneity in breast cancer makes them a fascinating and challenging stream to diagnose and treat. Several clinical therapies are available for breast cancer treatments. Chemotherapy, endocrine therapy, radiation therapy and immunotherapy are the milestones in the cancer treatments. Ral binding protein 1 is a promising target for breast cancer treatment and the platinum-based chemotherapies are the other remarkable fields. In immunotherapy, the usage of anti-programmed death (PD)-1 antibody is a new class of cancer immunotherapy that hinders immune effecter inhibition and potentially expanding preexisting anticancer immune responses. Breast cancer genetics and treatment strategies are crucial in escalating survival rates.

Breast Self-Examination Practice Among Female University Students in Ethiopia: A Systematic Review and Meta-Analysis

Background:

Breast self-examination (BSE) is one of the most feasible methods of screening for early stages of breast cancer. However, the practice rate is insufficient in many low and middle-income countries including Ethiopia. Hence, this study aimed to estimate the pooled prevalence of BSE practice among female university students in Ethiopia.

Methods:

PubMed, Cochrane Library, Scopus, and Google Scholar were searched for studies that assessed BSE practice among female students in Ethiopian universities. The study included articles published from January 1st, 2010 to June 16th, 2020. The Cochran’s Q chi-square and the respective I² test statistics were used to check heterogeneity among the included studies. To assess publication biases, the funnel plot and Egger’s regression tests were employed. Subgroup analysis was done by using different characteristics of studies. Sensitivity analysis was also run to assess the effect of a single study on the pooled outcome. STATA™ Version 14 software packages were employed for data analysis.

Results:

Sixteen (n = 16) studies with 5,743 participants were included to estimate the pooled prevalence of BSE practice. The prevalence of regular BSE practice reported in the studies ranges from 0% to 26.4%. The estimated pooled prevalence of regular BSE practice among university students in Ethiopia is 11.23% which is very low. The prevalence of BSE practice was high, 13.6% in studies published before 2015, 12.0% among health science students, and 12.6% in studies with a sample size of 384 participants and above. In addition, the estimated pooled prevalence of irregular self-breast-examination practice was 33.28%.

Conclusion:

The rate of BSE practice among female university students is low. Thus, awareness strategies need to be designed to increase the practice rate among women in the country as BSE is one of the most feasible strategies in early detection of breast cancer if properly implemented.

The impact of consanguinity on women's attitudes toward molecular testing of breast cancer in Saudi Arabia

Background: Breast cancer is the most common cancer in adult women in Saudi Arabia; however, awareness about molecular testing for breast cancer is insufficient. The authors aimed to assess knowledge and attitudes to determine sociodemographic factors that correlate with perceptions of genetic testing among Saudi women. Materials & methods: This cross-sectional community-based study used a questionnaire to investigate the relationships between various social and economic factors. Results: There was a significant difference in interest in undergoing molecular testing between women in consanguineous and non-consanguineous marriages. Conclusion: The data show that consanguinity adds an extra layer of complexity to other sociodemographic barriers that hinder the efficacy of early breast cancer detection and prevention programs in Saudi Arabia.

Global, regional, national burden of breast cancer in 185 countries: evidence from GLOBOCAN 2018

PURPOSE

This study aims to examine the burden of breast cancer in 185 countries in 2018.

METHODS

The estimates of incidence, mortality, and prevalence of breast cancer were drawn from GLOBOCAN 2018. The overall burden of breast cancer was gauged using breast cancer burden index (BRCBI)-a novel index comprising age-standardized incidence rate (ASIR), age-standardized mortality rate (ASMR), mortality-to-incidence ratio (MIR), prevalence-to-incidence ratio (PIR), and prevalence-to-mortality ratio (PMR). The socioeconomic status of countries was measured using human development index (HDI) RESULTS: Globally, breast cancer was responsible for an estimated 626,679 deaths at age-standardized rate of 13/100,000; there were 2.1 million cases diagnosed in 2018 at age-standardized rate of 46.3/100,000. The ASIR varied 22-fold from 5/100,000 (Bhutan) to 113.2/100,000 (Belgium). The ASMR varied 13-fold from 2.7/100,000 (Bhutan) to 36.9/100,000 (Fiji). The HDI exhibited a positive gradient with ASIR (r = 0.73), PIR (r = 0.98), and PMR (r = 0.85); with MIR, however, it exhibited a negative association (r = - 0.83). The BRCBI spanned from 0.70 in Somalia to 78.92 in South Korea and exhibited a positive association with HDI (r = 0.76). An additional 46,823 female lives in 2018 and a cumulative total of 333,304 lives could have been saved over 2013-2018, had countries performed as per their HDI.

CONCLUSIONS

The substantial burden of breast cancer in developing and low-resource economies calls for a holistic approach to cancer management and control that includes oncologic infrastructure to provide cost-effective screening, diagnostic, therapeutic, and palliative services, greater breast cancer awareness, and mitigation of risk factors.

The relationship between BRCA-associated breast cancer and age factors: an analysis of the Japanese HBOC consortium database

BRCA1/2 pathogenic variant prevalence in Japanese breast cancer is unclear. Here, we analyzed BRCA1/2 pathogenic variant prevalence with a particular focus on age factors, using the Japanese HBOC consortium database. All registered subjects were Japanese individuals who underwent BRCA1/2 genetic testing from January 1996 to July 2017 according to the Japanese HBOC consortium database. Cases were extracted and analyzed for each evaluation item. Overall BRCA1 and BRCA2 pathogenic variant prevalence was 11.2% and 9.0% in the cohort of 2366 proband patients, respectively. The age at onset of breast cancer for patients with BRCA1/2 pathogenic variants was significantly lower than that for patients without a BRCA1/2 pathogenic variant. In both BRCA1/2 patients, ages at onset were not statistically significantly different between two subtype groups (ER-positive vs. TNBC). We analyzed the BRCA1/2 pathogenic variant prevalence among age groups in patients with no family history of breast or ovarian cancer. In the TNBC group, the rate of genetic variants was more frequent among younger patients. Our results demonstrated that early breast cancer onset is associated with a BRCA1/2 pathogenic variant in the Japanese population. Younger TNBC patients were more likely to have a BRCA1/2 pathogenic variant irrespective of a family history of breast or ovarian cancer.

Population-based genetic testing for Women's cancer prevention

Germline mutations in cancer-susceptibility-genes (CSG) can dramatically increase womens' lifetime risk of ovarian, endometrial, breast and bowel cancers. Identification of unaffected carriers is important to enable proactive engagement with highly effective screening and preventive options to minimise cancer risk. Currently, a family-history model is used to identify individuals with CSGs. Complex regional referral guidelines specify the family-history criteria required before an individual is eligible for genetic-testing. This model is ineffective, resource intense, misses >50% CSG carriers, is associated with underutilisation of genetic-testing services and delays detection of mutation carriers. Although awareness and detection of CSG-carriers has improved, over 97% carriers remain unidentified. This reflects significant missed opportunities for precision-prevention. Population-based genetic-testing (PBGT) represents a novel healthcare strategy with the potential to dramatically improve detection of unaffected CSG-carriers along with enabling population risk-stratification for cancer precision-prevention. Several research studies have assessed the impact, feasibility, acceptability, long-term psychological outcomes and cost-effectiveness of population-based BRCA-testing in the Ashkenazi-Jewish population. Initial data on PBGT in the general-population is beginning to emerge and large implementation studies investigating PBGT in the general-population are needed. This review will summarise the current research into the clinical, psycho-social, health-economic, societal and ethical consequences of a PBGT model for women's cancer precision-prevention.

Germline Mutation in 1338 BRCA-Negative Chinese Hereditary Breast and/or Ovarian Cancer Patients: Clinical Testing with a Multigene Test Panel

Differences in the mutation spectrum across ethnicities suggest the importance of identifying genes in addition to common high penetrant genes to estimate the associated breast cancer risk in China. A total of 1338 high-risk breast cancer patients who tested negative for germline BRCA1, BRCA2, TP53, and PTEN mutations between 2007 and 2017 were selected from the Hong Kong Hereditary Breast Cancer Family Registry. Patient samples were subjected to next-generation DNA sequencing using a multigene panel (Color Genomics). All detected pathogenic variants were validated by bidirectional DNA sequencing. The sequencing data were coanalyzed by a bioinformatics pipeline developed in-house. Sixty-one pathogenic variants (4.6%) were identified in this cohort in 11 cancer predisposition genes. Most carriers (77.1%) had early onset of breast cancer (age <45 years), 32.8% had family members with breast cancer, and 11.5% had triple-negative breast cancer. The most common mutated genes were PALB2 (1.4%), RAD51D (0.8%), and ATM (0.8%). A total of 612 variants of unknown significance were identified in 494 patients, and 87.4% of the variants of unknown significance were missense mutations. Pathogenic variants in cancer predisposition genes beyond BRCA1, BRCA2, TP53, and PTEN were detected in an additional 4.6% of patients using the multigene panel. PALB2 (1.4%) and RAD51D (0.8%) were the most commonly mutated genes in patients who tested mutation negative by a four-gene panel.

A novel CHEK2 variant identified by next generation sequencing in an Indian family with hereditary breast cancer syndrome

Genetic variations in CHEK2 (checkpoint kinase 2) gene have been associated with hereditary predisposition to various cancers including breast and ovarian cancer. CHEK2 tumor suppressor gene encodes for a checkpoint kinase that responds to breaks in DNA, regulates DNA repair and cellular proliferation. We report a BRCA negative family with multiple affected women having breast cancer, with a novel, missense, likely pathogenic variant in the CHEK2 gene (c.1376T>G; p.Ile459Ser) that segregated with subjects with breast cancer. This case provides insight into the role of the CHEK2 gene in causing breast cancer susceptibility in families and supports the use of multigene panel testing in cases with hereditary predisposition to breast cancer.

Association of Single-Nucleotide Polymorphisms in Monoubiquitinated FANCD2-DNA Damage Repair Pathway Genes With Breast Cancer in the Chinese Population

Objective:

The aim of the study was to estimate breast cancer risk conferred by individual single-nucleotide polymorphisms of breast cancer susceptibility genes.

Methods:

We analyzed the 48 tagging single-nucleotide polymorphisms of 8 breast cancer susceptibility genes involved in the monoubiquitinated FANCD2–DNA damage repair pathway in 734 Chinese women with breast cancer and 672 age-matched healthy controls.

Results:

Forty-five tagging single-nucleotide polymorphisms were successfully genotyped by SNPscan, and the call rates for each tagging single-nucleotide polymorphisms were above 98.9%. We found that 13 tagging single-nucleotide polymorphisms of 5 genes (Parter and localizer of Breast cancer gene2 (PALB2), Tumour protein 53 (TP53), Nijmegen breakage syndrome 1, Phosphatase and tensin homolog deleted from chromosome 10 (PTEN), and Breast cancer gene 1 (BRCA1-interacting protein 1)) were significantly associated with breast cancer risk. A total of 5 tagging single-nucleotide polymorphisms (rs2299941 of PTEN, rs2735385, rs6999227, rs1805812, and rs1061302 of Nijmegen breakage syndrome 1) were tightly associated with breast cancer risk in sporadic cases, and 5 other tagging single-nucleotide polymorphisms (rs1042522 of TP53, rs2735343 of PTEN, rs7220719, rs16945628, and rs11871753 of BRCA1-interacting protein 1) were tightly associated with breast cancer risk in familial and early-onset cases.

Conclusions:

Some of the tagging single-nucleotide polymorphisms of 5 genes (PALB2, TP53, Nijmegen breakage syndrome 1, PTEN, and BRCA1-interacting protein 1) involved in the monoubiquitinated FANCD2–DNA damage repair pathway were significantly associated with breast cancer risk.

Association of the study between LncRNA-H19 gene polymorphisms with the risk of breast cancer

BACKGROUND

The H19 is a maternally expressed imprinted gene transcribing a long noncoding RNA (lncRNA), which has previously been reported to be involved in tumorigenesis and cancer progression. The aim of this study was to evaluate the associations between two lncRNA-H19 (rs3741219 T>C and rs217727 C>T) gene polymorphisms with the risk of breast cancer (BC).

METHODS

In a case-control investigation, we evaluated 150 BC patients and 100 cancer-free subjects in East Azerbaijan Province of Iran. To assess two gene polymorphisms, the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used.

RESULTS

The genotype frequencies of two lncRNA-H19 (rs217727 C>T and rs3741219 T>C) gene polymorphisms TT + TC/CC and CC + CT/TT have not shown a statistically significant association with the risk of BC (P = 0.065; OR = 0.967; 95% CI, 0.938-0.996) and (P = 0.510; OR = 1.583; 95% CI, 0.399-6.726), respectively. In addition, our findings revealed a significant differences in allele frequencies in lncRNA-H19 rs217727 C>T polymorphism between groups (P = 0.033; OR = 1.985; 95% CI, 1.048-3.761).

CONCLUSION

Our findings suggested that rs217727 C>T polymorphism may be involved in the pathogenesis of BC, whereas rs3741219 T>C variation may not be involved in the genetic background of BC in Iranian.

Transcriptome mining of non-BRCA1/A2 and BRCA1/A2 familial breast cancer

About 10% of all breast cancer cases are the familial type. Mutations in two highly penetrance breast cancer susceptibility genes, BRCA1 and BRCA2, can only explain 20% to 25% of genetic susceptibility to breast cancer, and most familial breast cancer cases have intact BRCA1 and BRCA2 genes that refer to non-BRCA1/A2 or BRCAX familial breast cancer. Despite extensive studies, more than 50% of genetic susceptibility to breast cancer remained to be disclosed. Finding the differences between these two types of breast cancer (non-BRCA1/A2 and BRCA1/A2) at genomic, transcriptomic, and proteomic levels can help us to elucidate fundamental molecular processes and develope more promising therapeutic targets. Here, we used expression data of 391 patients with familial breast cancer including 195 non-BRCA1/A2 and 196 BRCA1 and/or BRCA2 cases from four independent studies by means of meta-analysis to find differences in gene expression signature between these two types of familial breast cancer. As well as, we applied comprehensive network analysis to find crucial protein complexes and regulators for each condition. Our results revealed significant overexpression of cell cycle processes in BRCA1/A2 patients and significant overexpression of estrogen axis in non-BRCA1/A2 patients. Moreover, we found FOXM1 as the central regulator of cell cycle processes and GATA3, FOXA1, and ESR1 as the main regulators of estrogen axis.

A FRET immunosensor for sensitive detection of CA 15-3 tumor marker in human serum sample and breast cancer cells using antibody functionalized luminescent carbon-dots and AuNPs-dendrimer aptamer as donor-acceptor pair

We proposed a FRET immunosensing for detection of CA15-3 tumor marker by highly biospecific interactions between CA 15-3 antigen and the corresponding antibody and aptamer. In this sandwich type immunoassay, CA15-3 antibody-functionalized carbon dots and AuNPs labeled PAMAM-Dendrimer/aptamer were used as donor/acceptor, respectively. When CA 15-3 Ag was added to homogenous immunoassay, the strong complex interaction between CA15-3 Ab-CA15-3 Ag- aptamer caused in more coming closer carbon dot and AuNPs and more decreasing fluorescence signal. The decreased fluorescence intensity was linear at three ranges including in concentration range 1.1 μUmL^-1 to 16 μU mL^-1 with regression of R² = 0.9879, at the concentration range 16 μU mL^-1 to 0.163 mU mL^-1 with regression of R² = 0.9944 and at the concentration range 0.163 mU mL^-1 to 5.0 mU mL^-1 with regression of R² = 0.9805. The detection limit of the FRET immunoassay was 0.9 μU mL^-1. This assay revealed good sensitivity and specificity with MDA-MB-231 breast cancer cells concentrations from 1000 to 40000 cells/mL with correlation coefficient of 0.9955 and detection limit of 300 cells/mL (3 cells in 10 μL of injected sample). In addition, this FRET immunosensing is applicable in diluted human serum. The recovery values were in the range of 95.86-96.97% for CA 15-3 Ag in spiked serum sample with RSD lower than 7.3%. The proposed immunoassay could be a valid model for establishing other immunoassays for detection of different cancer tumor markers with relevant antigens and antibodies.

Association of APC and MCC Polymorphisms with Increased Breast Cancer Risk in an Indian Population

The adenomatous polyposis coli (APC) and mutated in colorectal cancer (MCC) genes are key regulatory genes of the Wnt/β-catenin signaling pathway, which are independently involved in maintaining low levels of β-catenin in the cell. In addition to genetic and epigenetic alterations, some genetic polymorphisms in the genes associated with the Wnt signaling pathway have been reported to be associated with an increased risk of cancer, including breast cancer. In the present study we analyzed the association of genotype and haplotype status of two single nucleotide polymorphisms (SNPs), rs2229992 and rs11283943, in the APC and MCC genes, respectively, with an increased risk of breast carcinogenesis in a breast cancer and control population from eastern India. We observed a significant association of the rs11283943 SNP with increased breast cancer risk. Two specific haplotypes involving the minor allele of rs11283943 were found to be associated with an increased breast cancer risk. Kaplan-Meier curves showed a significant association of the 2–2 genotype (genotype homozygous for the rs11283943 minor allele) with decreased survival (p=0.045) of the breast cancer patients in our study, in particular patients with early-onset BC.

Next-Generation Sequencing Reveals a Nonsense Mutation (p.Arg364Ter) in MRE11A Gene in an Indian Patient with Familial Breast Cancer

BACKGROUND

The MRN complex consisting of MRE11A-RAD50-NBS1 proteins is involved in the repair of double-strand breaks, and mutations in genes coding for the MRN complex have been identified in families with breast and ovarian cancer.

CASE REPORT

In a BRCA-negative family with positive history of breast and endometrial cancer, next-generation sequencing-based panel testing identified a mutation in the MRE11A gene (NM_005590 c.1090C>T: p.Arg364Ter). This mutation results in a shorter mutated protein lacking 2 DNA binding domains (the GAR domain and the RAD50 binding site), abolishing the function of protein.

CONCLUSION

This case provides insight into the role of the MRE11A gene in causing breast cancer susceptibility in families, and supports the use of multigene panel testing in cases with hereditary predisposition to breast cancer.

Global Cancer in Women: Burden and Trends

This review is an abbreviated version of a report prepared for the American Cancer Society Global Health department and EMD Serono, Inc., a subsidiary of Merck KGaA, Darmstadt, Germany, which was released at the Union for International Cancer Control World Cancer Congress in Paris in November 2016. The original report can be found at https://www.cancer.org/health-care-professionals/our-global-health-work/global-cancer-burden/global-burden-of-cancer-in-women.html. Staff in the Intramural Research Department of the American Cancer Society designed and conducted the study, including analysis, interpretation, and presentation of the review. The funding sources had no involvement in the study design, data analysis and interpretation, or preparation of the reviewThere are striking disparities in the global cancer burden in women, yet few publications highlight cancer occurrence in this population, particularly for cancers that are not sex specific. This article, the first in a series of two, summarizes the current burden, trends, risk factors, prevention, early detection, and survivorship of all cancers combined and seven sites (breast, cervix, uterine corpus, ovary, colorectum, lung, and liver) that account for about 60% of the cancer burden among women worldwide, using data from the International Agency for Research on Cancer. Estimated 2012 overall cancer death rates in general are higher among women in low- and middle-income countries (LMICs) than high-income countries (HICs), despite their lower overall incidence rates, largely due to inadequate access to early detection and treatment. For example, the top mortality rates are in Zimbabwe (147 deaths per 100,000) and Malawi (138). Furthermore, incidence rates of cancers associated with economic development (e.g., lung, breast, colorectum) are rising in several LMICs. The burden of cancer among women could be substantially reduced in both HICs and LMICs through broad and equitable implementation of effective interventions, including tobacco control, HPV and HBV vaccination, and screening (breast, cervix, and colorectum). Cancer Epidemiol Biomarkers Prev; 26(4); 444-57. ©2017 AACRSee related article by Islami et al. in this CEBP Focus section, "Global Cancer in Women."

MicroRNA-101 inhibits cell progression and increases paclitaxel sensitivity by suppressing MCL-1 expression in human triple-negative breast cancer

Triple-negative breast cancer is the most aggressive breast cancer subtype. The aim of our study was to investigate the functional role of both miR-101 and MCL-1 in the sensitivity of human triple-negative breast cancer (TNBC) to paclitaxel. We found that the expression of miR-101 was strongly decreased in triple-negative breast cancer tissues and cell lines. The expression of miR-101 was not associated with clinical stage or lymph node infiltration in TNBC. Ectopic overexpression of miR-101 inhibit growth and induced apoptosis in vitro and suppressed tumorigenicity in vivo. MCL-1 was significantly overexpressed in most of the TNBC tissues and cell lines. Luciferase assay results confirmed MCL-1 as a direct target gene of miR-101. MiR-101 inhibited MCL-1 expression in TNBC cells and transplanted tumors. There was a negative correlation between the level of expression of miR-101 and MCL-1 in TNBC tissues. Suppression of MCL-1 enhanced the sensitivity of MDA-MB-435 cells to paclitaxel. Furthermore, miR-101 increased paclitaxel sensitivity by inhibiting MCL-1 expression. Our findings provide significant insight into the molecular mechanisms of TNBC carcinogenesis and may have clinical relevance for the development of novel, targeted therapies for TNBC.

Genetic Polymorphisms in Long Noncoding RNA H19 Are Associated With Susceptibility to Breast Cancer in Chinese Population

H19, a maternally expressed imprinted gene transcribing a long noncoding RNA, has previously been reported to be involved in tumorigenesis and cancer progression. However, the association between the H19 polymorphisms and breast cancer (BC) susceptibility has remained elusive. The aim of this study was to evaluate the associations between 2 H19 haplotype tagging SNPs (rs3741219 T>C, rs217727 C>T) and the risk of breast cancer. Our study comprised 464 BC patients and 467 cancer-free controls in China. rs3741219 and rs217727 were genotyped with polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) and created restriction site PCR (CRS-RFLP) assays, respectively. False-positive report probability (FPRP) was calculated to test the false-positive association. On performing univariate analysis, no significant association between H19 polymorphisms (rs3741219 and rs217727) and BC was observed. However, in further stratified analyses, CT+TT genotypes of rs217727 had a significantly lower risk of breast cancer among women with number of pregnancy >2 (OR = 0.79; 95% CI = 0.55-0.97). CT genotype of rs217727 was associated with ER positivity (OR = 2.19; 95 % CI = 1.07-4.45) and HER-2 positivity (OR = 1.34; 95 % CI = 1.05-2.12). It was proved that our results were less likely to be false positives according to false-positive report probability calculation. Our findings extend available data on the association of H19 polymorphisms and BC susceptibility. Further validation in large population or cohort studies is needed.

Germline BRCA testing is moving from cancer risk assessment to a predictive biomarker for targeting cancer therapeutics

PURPOSE

Originally, BRCA testing was used for risk assessment and prevention strategies for breast and ovarian cancer. Nowadays, BRCA status may influence therapeutic decision making at cancer diagnosis. Our objective was to analyze whether the medical advances have changed the burden and pattern of referral, and the pathogenic mutation detection rate.

METHODS

We included 969 probands from our hereditary cancer registry who undertook a full BRCA analysis between 2006 and 2014. Chi-square tests were used to compare categorical variables.

RESULTS

The number of genetic tests have raised from 28 to 170, representing a sixfold increase. In 2006, we tested 1.6 relatives/proband while this proportion was four in 2014. Overall, 20 % harbored a deleterious mutation and 11 % had a variant of unknown significance (VUS). There has been a downward trend in the detection rate of VUS. Testing patients with breast cancer during neoadjuvancy has raised from 4 to 25 % (p = 0.002), while testing them during remission has decreased from 79 to 29 % (p < 0.001). The proportion of patients assessed during the first 6 months after their cancer diagnosis has increased from 3 to 34 % (p = 0.001). Risk reducing mastectomy and salpingoophorectomy have raised from 0 to 24 %, and from 36 to 65 %, respectively.

CONCLUSIONS

BRCA testing has experienced a sixfold increase, the number of relatives being tested has doubled, and the test is being performed at earlier phases of the disease. It is necessary to adequate the health resources to preserve the BRCA genetic counseling quality while incorporating BRCA testing for therapeutic decision making.

Breastfeeding and breast cancer risk by receptor status--a systematic review and meta-analysis

BACKGROUND

Breastfeeding is inversely associated with overall risk of breast cancer. This association may differ in breast cancer subtypes defined by receptor status, as they may reflect different mechanisms of carcinogenesis. We conducted a systematic review and meta-analysis of case-control and prospective cohort studies to investigate the association between breastfeeding and breast cancer by estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status.

DESIGN

We searched the PubMed and Scopus databases and bibliographies of pertinent articles to identify relevant articles and used random-effects models to calculate summary odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

This meta-analysis represents 27 distinct studies (8 cohort and 19 case-control), with a total of 36 881 breast cancer cases. Among parous women, the risk estimates for the association between ever (versus never) breastfeeding and the breast cancers negative for both ER and PR were similar in three cohort and three case-control studies when results were adjusted for several factors, including the number of full-term pregnancies (combined OR 0.90; 95% CI 0.82-0.99), with little heterogeneity and no indication of publication bias. In a subset of three adjusted studies that included ER, PR, and HER2 status, ever breastfeeding showed a stronger inverse association with triple-negative breast cancer (OR 0.78; 95% CI 0.66-0.91) among parous women. Overall, cohort studies showed no significant association between breastfeeding and ER+/PR+ or ER+ and/or PR+ breast cancers, although one and two studies (out of four and seven studies, respectively) showed an inverse association.

CONCLUSIONS

This meta-analysis showed a protective effect of ever breastfeeding against hormone receptor-negative breast cancers, which are more common in younger women and generally have a poorer prognosis than other subtypes of breast cancer. The association between breastfeeding and receptor-positive breast cancers needs more investigation.

HBOC multi-gene panel testing: comparison of two sequencing centers

Multi-gene panels are used to identify genetic causes of hereditary breast and ovarian cancer (HBOC) in large patient cohorts. This study compares the diagnostic workflow in two centers and gives valuable insights into different next-generation sequencing (NGS) strategies. Moreover, we present data from 620 patients sequenced at both centers. Both sequencing centers are part of the German consortium for hereditary breast and ovarian cancer (GC-HBOC). All 620 patients included in this study were selected following standard BRCA1/2 testing guidelines. A set of 10 sequenced genes was analyzed per patient. Twelve samples were exchanged and sequenced at both centers. NGS results were highly concordant in 12 exchanged samples (205/206 variants = 99.51 %). One non-pathogenic variant was missed at center B due to a sequencing gap (no technical coverage). The custom enrichment at center B was optimized during this study; for example, the average number of missing bases was reduced by a factor of four (vers. 1: 1939.41, vers. 4: 506.01 bp). There were no sequencing gaps at center A, but four CCDS exons were not included in the enrichment. Pathogenic mutations were found in 12.10 % (75/620) of all patients: 4.84 % (30/620) in BRCA1, 4.35 % in BRCA2 (27/620), 0.97 % in CHEK2 (6/620), 0.65 % in ATM (4/620), 0.48 % in CDH1 (3/620), 0.32 % in PALB2 (2/620), 0.32 % in NBN (2/620), and 0.16 % in TP53 (1/620). NGS diagnostics for HBOC-related genes is robust, cost effective, and the method of choice for genetic testing in large cohorts. Adding 8 genes to standard BRCA1- and BRCA2-testing increased the mutation detection rate by one-third.

Association between MDM2 rs 2279744 polymorphism and breast cancer susceptibility: a meta-analysis based on 9,788 cases and 11,195 controls

Purpose

Previous studies have suggested associations between MDM2 (mouse double minute 2 homolog) polymorphisms and cancer risk. The aim of this study was to evaluate the relationship between the MDM2 rs 2279744 polymorphism and the susceptibility of breast cancer.

Methods

We searched PubMed, Web of Knowledge, Embase, and the Chinese National Knowledge Infrastructure (CNKI) database for case–control studies published up to October 2013 that investigated MDM2 rs 2279744 polymorphism and breast cancer risk. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of these associations.

Results

A total of 19 studies were identified for the meta-analysis, including 9,788 cases and 11,195 controls. The variant heterozygote (TG) was associated with breast cancer risk in the overall population (TG vs TT: OR =1.10, 95% CI =1.04–1.17, P=0.001, P=0.23 for heterogeneity test). In the subgroup analyses by ethnicity, a significantly increased risk was observed among Asians (G vs T: OR =1.12, 95% CI =1.02–1.23, P=0.02, P_het=0.04; GG vs TT: OR =1.29, 95% CI =1.06–1.56, P=0.01, P_het=0.04; TG vs TT: OR =1.36, 95% CI =1.15–1.60, P=0.0004, P_het=0.45; dominant model TG+GG vs TT: OR =1.21, 95% CI =1.03–1.41, P=0.02, P_het=0.07). However, among Caucasians, rs 2279744 was associated with breast cancer risk in only one genotype (TG vs TT: OR =1.09, 95% CI =1.00–1.18, P=0.04, P_het=0.37). No publication bias was found in the present study.

Conclusion

This meta-analysis provides evidence for the association between the MDM2 rs 2279744 polymorphism and breast cancer susceptibility. The results suggest that the MDM2 rs 2279744 polymorphism plays an important role in breast cancer, especially in Asians.

Understanding susceptibility to breast cancer metastasis: the genetic approach

Metastasis is a complex phenotype that is not discrete, is polygenic, varies in range over the entire population and follows non-Mendelian inheritance. Recent evidence indicates that inherited susceptibility affects not only the development of the primary tumor, but is also an important factor in progression and metastasis. Since metastasis accounts for the majority of breast cancer deaths, identification and understanding of the genetic modifiers of metastasis underlies success of personalized therapy. Studies from our laboratory and others have now characterized several metastasis susceptibility factors. While an important step forward, these certainly do not describe the entire metastatic phenomenon and efforts continue to expand this knowledge. Here we review the complex metastatic process and current knowledge on the genetics of breast cancer metastasis, including germline polymorphisms that have been associated with the disease.

miR-342 regulates BRCA1 expression through modulation of ID4 in breast cancer

A miRNAs profiling on a group of familial and sporadic breast cancers showed that miRNA-342 was significantly associated with estrogen receptor (ER) levels. To investigate at functional level the role of miR-342 in the pathogenesis of breast cancer, we focused our attention on its "in silico" predicted putative target gene ID4, a transcription factor of the helix-loop-helix protein family whose expression is inversely correlated with that of ER. ID4 is expressed in breast cancer and can negatively regulate BRCA1 expression. Our results showed an inverse correlation between ID4 and miR-342 as well as between ID4 and BRCA1 expression. We functionally validated the interaction between ID4 and miR-342 in a reporter Luciferase system. Based on these findings, we hypothesized that regulation of ID4 mediated by miR-342 could be involved in the pathogenesis of breast cancer by downregulating BRCA1 expression. We functionally demonstrated the interactions between miR-342, ID4 and BRCA1 in a model provided by ER-negative MDA-MB-231 breast cancer cell line that presented high levels of ID4. Overexpression of miR-342 in these cells reduced ID4 and increased BRCA1 expression, supporting a possible role of this mechanism in breast cancer. In the ER-positive MCF7 and in the BRCA1-mutant HCC1937 cell lines miR-342 over-expression only reduced ID4. In the cohort of patients we studied, a correlation between miR-342 and BRCA1 expression was found in the ER-negative cases. As ER-negative cases were mainly BRCA1-mutant, we speculate that the mechanism we demonstrated could be involved in the decreased expression of BRCA1 frequently observed in non BRCA1-mutant breast cancers and could be implicated as a causal factor in part of the familial cases grouped in the heterogeneous class of non BRCA1 or BRCA2-mutant cases (BRCAx). To validate this hypothesis, the study should be extended to a larger cohort of ER-negative cases, including those belonging to the BRCAx class.

Distribution of BRCA1 and BRCA2 Mutations in Asian Patients with Breast Cancer

Breast cancer is the most prevalent cancer in Asian females, and the incidence of breast cancer has been increasing in Asia. Because Asian patients develop breast cancer at a younger age than their Caucasian counterparts, the contributions of BRCA1 and BRCA2 (BRCA1/2) mutations in Asians are expected to be different than in Caucasians. The prevalence of BRCA1/2 mutations in the Asian population varies among countries and studies. Most Asian studies have reported more frequent mutations in BRCA2 than in BRCA1, with the exception of studies from India and Pakistan. In addition, the contribution of large genomic rearrangements of BRCA1/2 genes is relatively small in Asian populations in comparison to other ethnic populations. Various statistical models for the prediction of BRCA1/2 mutations have underestimated the risk of having these genetic mutations in Asians, especially in predicting BRCA2 gene mutation. Until recently, BRCA1/2 mutation analyses in Asia were mostly conducted by independent single institutions with different patient selection criteria and using various genotyping methods. However, a couple of Asian groups have initiated nationwide studies collecting BRCA1/2 mutational data. These national collaborative studies will help a comprehensive understanding of the prevalence of BRCA1/2 mutations in the Asian population.

MicroRNA-based molecular classification of non-BRCA1/2 hereditary breast tumours

Background:

Hereditary breast cancer comprises 5–10% of all breast cancers. Mutations in two high-risk susceptibility genes, BRCA1 and BRCA2, along with rare intermediate-risk genes and common low-penetrance alleles identified, altogether explain no more than 45% of the high-risk breast cancer families, although the majority of cases are unaccounted for and are designated as BRCAX tumours. Micro RNAs have called great attention for classification of different cancer types and have been implicated in a range of important biological processes and are deregulated in cancer pathogenesis.

Methods:

Here we have performed an exploratory hypothesis-generating study of miRNA expression profiles in a large series of 66 primary hereditary breast tumours by microarray analysis.

Results:

Unsupervised clustering analysis of miRNA molecular profiles revealed distinct subgroups of BRCAX tumours, ‘normal-like' BRCAX-A, ‘proliferative' BRCAX-B, ‘BRCA1/2-like' BRCAX-C and ‘undefined' BRCAX-D subgroup. These findings introduce a new insight in the biology of hereditary breast cancer, defining specific BRCAX subgroups, which could help in the search for novel susceptibility pathways in hereditary breast cancer.

Conclusion:

Our data demonstrate that BRCAX hereditary breast tumours can be sub-classified into four previously unknown homogenous groups characterised by specific miRNA expression signatures and histopathological features.

Busy lifestyles and mammography screening: time pressure and women's reattendance likelihood

Time pressure is often cited as a reason for non-attendance at mammography screening, although evidence from other areas of psychology suggests that time pressure can improve performance when barriers such as time pressure provide a challenge. We predicted that time pressure would negatively predict attendance in women whose self-efficacy for overcoming time pressure is low, but positively predict attendance when self-efficacy is high. Time pressure was operationalised as the self-reported number of dependent children and others, and average number of working hours per week. Australian women were surveyed after being invited to attend second or subsequent screenings at a free public screening service, and subsequent attendance monitored until six months after screening was due. The majority (87.5%) attended screening. Women with more dependent children and higher self-efficacy showed greater attendance likelihood, and women with fewer non-child dependants and lower self-efficacy were less likely to attend. Working hours did not predict attendance. Findings provide partial support for the idea that time pressure acts as a challenge for women with high self-efficacy.

Epigenetic regulation of multiple tumor-related genes leads to suppression of breast tumorigenesis by dietary genistein

Breast cancer is one of the most lethal diseases in women; however, the precise etiological factors are still not clear. Genistein (GE), a natural isoflavone found in soybean products, is believed to be a potent chemopreventive agent for breast cancer. One of the most important mechanisms for GE inhibition of breast cancer may involve its potential in impacting epigenetic processes allowing reversal of aberrant epigenetic events during breast tumorigenesis. To investigate epigenetic regulation for GE impedance of breast tumorigenesis, we monitored epigenetic alterations of several key tumor-related genes in an established breast cancer transformation system. Our results show that GE significantly inhibited cell growth in a dose-dependent manner in precancerous breast cells and breast cancer cells, whereas it exhibited little effect on normal human mammary epithelial cells. Furthermore, GE treatment increased expression of two crucial tumor suppressor genes, p21^WAF1 (p21) and p16^INK4a (p16), although it decreased expression of two tumor promoting genes, BMI1 and c-MYC. GE treatment led to alterations of histone modifications in the promoters of p21 and p16 as well as the binding ability of the c-MYC–BMI1 complex to the p16 promoter contributing to GE-induced epigenetic activation of these tumor suppressor genes. In addition, an orally-fed GE diet prevented breast tumorigenesis and inhibited breast cancer development in breast cancer mice xenografts. Our results suggest that genistein may repress early breast tumorigenesis by epigenetic regulation of p21 and p16 by impacting histone modifications as well as the BMI1-c-MYC complex recruitment to the regulatory region in the promoters of these genes. These studies will facilitate more effective use of soybean product in breast cancer prevention and also help elucidate the mechanisms during the process of early breast tumorigenesis.

BAC CGH-array identified specific small-scale genomic imbalances in diploid DMBA-induced rat mammary tumors

BACKGROUND

Development of breast cancer is a multistage process influenced by hormonal and environmental factors as well as by genetic background. The search for genes underlying this malignancy has recently been highly productive, but the etiology behind this complex disease is still not understood. In studies using animal cancer models, heterogeneity of the genetic background and environmental factors is reduced and thus analysis and identification of genetic aberrations in tumors may become easier. To identify chromosomal regions potentially involved in the initiation and progression of mammary cancer, in the present work we subjected a subset of experimental mammary tumors to cytogenetic and molecular genetic analysis.

METHODS

Mammary tumors were induced with DMBA (7,12-dimethylbenz[a]anthrazene) in female rats from the susceptible SPRD-Cu3 strain and from crosses and backcrosses between this strain and the resistant WKY strain. We first produced a general overview of chromosomal aberrations in the tumors using conventional kartyotyping (G-banding) and Comparative Genome Hybridization (CGH) analyses. Particular chromosomal changes were then analyzed in more details using an in-house developed BAC (bacterial artificial chromosome) CGH-array platform.

RESULTS

Tumors appeared to be diploid by conventional karyotyping, however several sub-microscopic chromosome gains or losses in the tumor material were identified by BAC CGH-array analysis. An oncogenetic tree analysis based on the BAC CGH-array data suggested gain of rat chromosome (RNO) band 12q11, loss of RNO5q32 or RNO6q21 as the earliest events in the development of these mammary tumors.

CONCLUSIONS

Some of the identified changes appear to be more specific for DMBA-induced mammary tumors and some are similar to those previously reported in ACI rat model for estradiol-induced mammary tumors. The later group of changes is more interesting, since they may represent anomalies that involve genes with a critical role in mammary tumor development. Genetic changes identified in this work are at very small scales and thus may provide a more feasible basis for the identification of the target gene(s). Identification of the genes underlying these chromosome changes can provide new insights to the mechanisms of mammary carcinogenesis.

Deregulated miRNAs in hereditary breast cancer revealed a role for miR-30c in regulating KRAS oncogene

Aberrant miRNA expression has been previously established in breast cancer and has clinical relevance. However, no studies so far have defined miRNAs deregulated in hereditary breast tumors. In this study we investigated the role of miRNAs in hereditary breast tumors comparing with normal breast tissue. Global miRNA expression profiling using Exiqon microarrays was performed on 22 hereditary breast tumors and 15 non-tumoral breast tissues. We identified 19 miRNAs differentially expressed, most of them down-regulated in tumors. An important proportion of deregulated miRNAs in hereditary tumors were previously identified commonly deregulated in sporadic breast tumors. Under-expression of these miRNAs was validated by qRT-PCR in additional 18 sporadic breast tumors and their normal breast tissue counterparts. Pathway enrichment analysis revealed that deregulated miRNAs collectively targeted a number of genes belonging to signaling pathways such as MAPK, ErbB, mTOR, and those regulating cell motility or adhesion. In silico prediction detected KRAS oncogene as target of several deregulated miRNAs. In particular, we experimentally validated KRAS as a miR-30c target. Luciferase assays confirmed that miR-30c binds the 3′UTR of KRAS transcripts and expression of pre-miR-30c down-regulated KRAS mRNA and protein. Furthermore, miR-30c overexpression inhibited proliferation of breast cancer cells. Our results identify miRNAs associated to hereditary breast cancer, as well as miRNAs commonly miss-expressed in hereditary and sporadic tumors, suggesting common underlying mechanisms of tumor progression. In addition, we provide evidence that KRAS is a target of miR-30c, and that this miRNA suppresses breast cancer cell growth potentially through inhibition of KRAS signaling.

Rare BRCA1 haplotypes including 3'UTR SNPs associated with breast cancer risk

Genetic markers identifying women at an increased risk of developing breast cancer exist, yet the majority of inherited risk remains elusive. While numerous BRCA1 coding sequence mutations are associated with breast cancer risk, BRCA1 mutations account for less then 5% of breast cancer risk. Since 3' untranslated region (3'UTR) polymorphisms disrupting microRNA (miRNA) binding can be functional and can act as genetic markers of cancer risk, we tested the hypothesis that such polymorphisms in the 3'UTR of BRCA1 and haplotypes containing these functional polymorphisms may be associated with breast cancer risk. We sequenced the BRCA1 3'UTR from breast cancer patients to identify miRNA disrupting polymorphisms. We further evaluated haplotypes of this region including the identified 3'UTR variants in a large population of controls and breast cancer patients (n = 221) with known breast cancer subtypes and ethnicities. We identified three 3'UTR variants in BRCA1 that are polymorphic in breast cancer populations, and haplotype analysis including these variants revealed that breast cancer patients harbor five rare haplotypes not generally found among controls (9.50% for breast cancer chromosomes, 0.11% for control chromosomes, p = 0.0001). Three of these rare haplotypes contain the rs8176318 BRCA1 3'UTR functional variant. These haplotypes are not biomarkers for BRCA1 coding mutations, as they are found rarely in BRCA1 mutant breast cancer patients (1/129 patients = 0.78%). These rare BRCA1 haplotypes and 3'UTR SNPs may represent new genetic markers of breast cancer risk.

Family history of breast cancer in first-degree relatives and triple-negative breast cancer risk

Triple-negative breast cancer accounts for less than 20% of breast cancers overall, but is the predominant subtype among carriers of mutations in BRCA1. However, few studies have assessed the association between breast cancer family history and risk of triple-negative breast cancer. We examined the relationship between having a family history of breast cancer in first-degree relatives and risk of triple-negative breast cancer, and risk of two other breast cancer subtypes defined by tumor marker expression. We evaluated data collected by the Breast Cancer Surveillance Consortium from 2,599,946 mammograms on 1,054,466 women, among whom 15% reported a first-degree family history of breast cancer. Using Cox regression in this cohort, we evaluated subtype-specific associations between family history and risk of triple-negative (N = 705), estrogen receptor-positive (ER+, N = 10,026), and hormone receptor-negative/HER2-expressing (ER-/PR-/HER2+, N = 308) breast cancer among women aged 40-84 years. First-degree family history was similarly and significantly associated with an increased risk of all the subtypes [hazard ratio (HR) = 1.73, 95% confidence interval (CI): 1.43-2.09, HR = 1.62, 95% CI: 1.54-1.70, and HR = 1.56, 95% CI: 1.15-2.13, for triple-negative, ER+, and ER-/PR-/HER2+, respectively]. Risk of all the subtypes was most pronounced among women with at least two affected first-degree relatives (versus women with no affected first-degree relatives, HR(triple-negative) = 2.66, 95% CI: 1.66-4.27, HR(ER+) = 2.05, 95% CI: 1.79-2.36, HR(ER)-(/PR)-(/HER2+) = 2.25, 95% CI: 0.99-5.08). Having a first-degree family history of breast cancer was associated with an increased risk of triple-negative breast cancer with a magnitude of association similar to that for the predominant ER+ subtype and ER-/PR-/HER2+ breast cancer.

Do alterations in mitochondrial DNA play a role in breast carcinogenesis?

A considerable body of evidence supports a role for oxidative stress in breast carcinogenesis. Due to their role in producing energy via oxidative phosphorylation, the mitochondria are a major source of production of reactive oxygen species, which may damage DNA. The mitochondrial genome may be particularly susceptible to oxidative damage leading to mitochondrial dysfunction. Genetic variants in mtDNA and nuclear DNA may also contribute to mitochondrial dysfunction. In this review, we address the role of alterations in mtDNA in the etiology of breast cancer. Several studies have shown a relatively high frequency of mtDNA mutations in breast tumor tissue in comparison with mutations in normal breast tissue. To date, several studies have examined the association of genetic variants in mtDNA and breast cancer risk. The G10398A mtDNA polymorphism has received the most attention and has been shown to be associated with increased risk in some studies. Other variants have generally been examined in only one or two studies. Genome-wide association studies may help identify new mtDNA variants which modify breast cancer risk. In addition to assessing the main effects of specific variants, gene-gene and gene-environment interactions are likely to explain a greater proportion of the variability in breast cancer risk.