Interactions between the estrogen receptor, its cofactors and microRNAs in breast cancer

Significant association between ERCC2 and MTHR polymorphisms and breast cancer susceptibility in Moroccan population: genotype and haplotype analysis in a case-control study

Background

Genetic determinants of breast cancer (BC) remained largely unknown in the majority of Moroccan patients. The purpose of this study was to explore the association of ERCC2 and MTHFR polymorphisms with genetic susceptibility to breast cancer in Moroccan population.

Methods

We genotyped ERCC2 polymorphisms (rs1799793 (G934A) and rs13181 (A2251C)) and MTHFR polymorphisms (rs1801133 (C677T) and rs1801131 (A1298C)) using TaqMan SNP Genotyping Assays. Genotypes were compared in 151 BC cases and 156 population-matched controls. Allelic, genotypic and haplotype associations with the risk and clinicopathological features of BC were assessed using logistic regression analyses.

Results

ERCC2-rs1799793-AA genotype was associated with high risk of BC compared to wild type genotype (recessive model: OR: 2.90, 95% CI: 1.34–6.26, p = 0.0069) even after Bonferroni correction (p < 0,0125). MTHFR rs1801133-TT genotype was associated with increased risk of BC (recessive model, OR: 2.49, 95% CI: 1.17–5.29, p = 0.017) but the association turned insignificant after Bonferroni correction. For the rest of SNPs, no statistical associations to BC risk were detected.

Significant association with clinical features was detected for MTHFR-rs1801133-TC genotype with early age at diagnosis and familial BC. Following Bonferroni correction, only association with familial BC remained significant. MTHFR-rs1801131-CC genotype was associated with sporadic BC. ERCC2-rs1799793-AA genotype correlated with ER+ and PR+ breast cancer. ERCC2-rs13181-CA genotype was significantly associated large tumors (T ≥ 3) in BC patients. None of these associations passed Bonferroni correction.

Haplotype analysis showed that ERCC2 A-C haplotype was significantly associated with increased BC risk (OR: 3.71, 95% CI: 1.7–8.12, p = 0.0002 and p = 0.0008 before and after Bonferroni correction, respectively) and positive expression of ER and PR in BC patients. ERCC2 G-C haplotype was correlated with PR negative and larger tumor (T4). We did not find any MTHFR haplotypes associated with BC susceptibility. However, the less common haplotype MTHFR T-C was more frequent in young patients and in familial breast cancer, while MTHFR C-C haplotype was associated with sporadic BC form.

Conclusions

Our findings are a first observation of association between ERCC2 SNPs and breast cancer in Moroccan population. The results suggested that ERCC2 and MTHFR polymorphisms may be reliable for assessing risk and prognosis of BC in Moroccan population.

Hsa-miR-375 is a predictor of local control in early stage breast cancer

Background

A long-term analysis by the Early Breast Cancer Trialist Group (EBCTG) revealed a strong correlation between local control and cancer-specific mortality. MicroRNAs (miRs), short (20–25 nucleotides) non-coding RNAs, have been described as prognosticators and predictors for breast cancer in recent years. The aim of the current study was to identify miRs that can predict local control after breast conserving therapy (BCT) in early stage breast cancer.

Results

Clinical data of 46 early stage breast cancer patients with local relapse after BCT were selected from the institutional database. These patients were matched to 101 control patients showing identical clinical features but without local relapse. The study was conducted in two steps. (1) In the pilot study, 32 patients (16 relapses versus 16 controls) were screened for the most de-regulated microRNAs (= candidate microRNAs) in a panel of 1250 miRs by microarray technology. Eight miRs were found to be significantly de-regulated. (2) In the validation study, the candidate microRNAs were analyzed in an independent cohort of 115 patients (30 relapses versus 85 controls) with reverse transcription quantitative polymerase chain reaction (RT-qPCR). From these eight candidates, hsa-miR-375 could be validated. Its median fold change was 2.28 (Mann-Whitney U test, corrected p value = 0.008). In the log-rank analysis, high expression levels of hsa-miR-375 correlated with a significantly higher risk of local relapse (p = 0.003). In a multivariate analysis (forward stepwise regression) including established predictors and prognosticators, hsa-miR-375 was the only variable that was able to distinguish the statistical significance between relapse and control groups (raw p value = 0.000195 HR = 0.76, 95 % CI 0.66–0.88; corrected p value = 0.005).

Conclusions

Hsa-miR-375 predicts local control in patient with early stage breast cancer, especially in estrogen receptor α (ER-α)-positive patients. It can therefore serve as an additional molecular marker for treatment choice independently from known predictors and prognosticators. Validation in larger prospective studies is warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0198-1) contains supplementary material, which is available to authorized users.

miR-491-5p functions as a tumor suppressor by targeting JMJD2B in ERα-positive breast cancer

The involvement of miR-491-5p in breast cancer development is unclear. This study showed that miR-491-5p is significantly downregulated in ERα-positive breast cancer tissues and cell lines and is generally hypermethylated in ERα-positive breast cancer. MiR-491-5p overexpression significantly suppressed estrogen signaling and estrogen-stimulated proliferation of breast cancer cells. Furthermore, the histone demethylase JMJD2B was identified as a direct target of miR-491-5p. The ectopic expression of JMJD2B abrogated the phenotypic changes induced by miR-491-5p in breast cancer cells. Collectively, our data indicate that miR-491-5p plays a tumor suppressor role in the development and progression of breast caner and may be a novel therapeutic target against ERα-positive breast cancer.

MicroRNAs in cancer therapeutic response: Friend and foe

Cancer initiation and development engage extremely complicated pathological processes which involve alterations of a large number of cell signaling cascades and functional networks in temporal and spatial orders. During last decades, microRNAs (miRNAs), a class of non-coding RNAs, have emerged as critical players in cancer pathogenesis and progression by modulating many pathological aspects related to tumor development, growth, metastasis, and drug resistance. The major function of miRNAs is to post-transcriptionally regulate gene expression depending on recognition of complementary sequence residing in target mRNAs. Commonly, a particular miRNA recognition sequence could be found in a number of genes, which allows a single miRNA to regulate multiple functionally connected genes simultaneously and/or chronologically. Furthermore, a single gene can be targeted and regulated by multiple miRNAs. However, previous studies have demonstrated that miRNA functions are highly context-dependent, which leads to distinct pathological outcomes in different types of cancer as well as at different stages by alteration of the same miRNA. Here we summarize recent progress in studies on miRNA function in cancer initiation, metastasis and therapeutic response, focusing on breast cancer. The varying functions of miRNAs and potential application of using miRNAs as biomarkers as well as therapeutic approaches are further discussed in the context of different cancers.

Far beyond the usual biomarkers in breast cancer: a review

Research investigating biomarkers for early detection, prognosis and the prediction of treatment responses in breast cancer is rapidly expanding. However, no validated biomarker currently exists for use in routine clinical practice, and breast cancer detection and management remains dependent on invasive procedures. Histological examination remains the standard for diagnosis, whereas immunohistochemical and genetic tests are utilized for treatment decisions and prognosis determinations. Therefore, we conducted a comprehensive review of literature published in PubMed on breast cancer biomarkers between 2009 and 2013. The keywords that were used together were breast cancer, biomarkers, diagnosis, prognosis and drug response. The cited references of the manuscripts included in this review were also screened. We have comprehensively summarized the performance of several biomarkers for diagnosis, prognosis and predicted drug responses of breast cancer. Finally, we have identified 15 biomarkers that have demonstrated promise in initial studies and several miRNAs. At this point, such biomarkers must be rigorously validated in the clinical setting to be translated into clinically useful tests for the diagnosis, prognosis and prediction of drug responses of breast cancer.

Vitamin D and microRNAs in bone

MicroRNAs (miRNAs) are short noncoding RNAs that orchestrate complex posttranscriptional regulatory networks essential to the regulation of gene expression. Through complementarity with messenger RNA (mRNA) sequences, miRNAs act primarily to silence gene expression through either degradation or inhibited translation of target transcripts. In this way, miRNAs can act to fine-tune the transcriptional regulation of gene expression, but they may also play distinct roles in the proliferation, differentiation, and function of specific cell types. miRNA regulatory networks may be particularly important for signaling molecules such as vitamin D that exert pleiotropic effects on tissues throughout the body. The active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D) functions as a steroid hormone that, when bound to its nuclear vitamin D receptor, is able to regulate target gene expression. However, recent studies have also implicated 1,25(OH)2D in epigenetic regulation of genes most notably as a modulator of miRNA function. The current review details our understanding of vitamin D and miRNAs with specific emphasis on the implications of this interaction for biological responses to vitamin D in one of its classical target tissues, i.e., bone.

Evaluation of single nucleotide polymorphisms in microRNAs (hsa-miR-196a2 rs11614913 C/T) from Brazilian women with breast cancer

Background

Emerging evidence has shown that miRNAs are involved in human carcinogenesis as tumor suppressors or oncogenes. Single nucleotide polymorphisms (SNPs) located in pre-miRNAs may affect the processing and therefore, influence the expression of mature miRNAs. Previous studies generated conflicting results when reporting association between the hsa-miR-196a2 rs11614913 common polymorphism and breast cancer.

Methods

This study evaluated the hsa-miR-196a2 rs11614913 SNP in 388 breast cancer cases and 388 controls in Brazilian women. Polymorphism was determined by real-time PCR; control and experimental groups were compared through statistical analysis using the X² or Fisher’s exact tests.

Results

The analysis of the SNPs frequencies showed a significant difference between the groups (BC and CT) in regards to genotype distribution (χ²: p = 0.024); the homozygous variant (CC) was more frequent in the CT than in the BC group (p = 0.009). The presence of the hsa-miR-196a2 rs11614913 C/T polymorphism was not associated with histological grades (p = 0.522), axillary lymph node positive status (p = 0.805), or clinical stage (p = 0.670) among the breast cancer patients.

Conclusions

The results of this study indicated that the CC polymorphic genotype is associated with a decreased risk of BC and the presence of the T allele was significantly associated with an increased risk of BC.

A crossroad of microRNAs and immediate early genes (IEGs) encoding oncogenic transcription factors in breast cancer

Signaling networks are involved in development, as well as in malignancy of the mammary gland. Distinct external stimuli activate intricate signaling cascades, which culminate in the activation of specific transcriptional programs. These signal-specific transcriptional programs are instigated by transcription factors (TFs) encoded by the immediate early genes (IEGs), and they lead to diverse cellular outcomes, including oncogenesis. Hence, regulating the expression of IEGs is of great importance, and involves several complementary transcriptional and posttranscriptional mechanisms, the latter entails also microRNAs (miRNAs). miRNAs are a class of non-coding RNAs, which have been implicated in regulation of various aspects of signaling networks. Through examination of the basic characteristics of miRNA function, we highlight the benefits of using miRNAs as regulators of early TFs and signaling networks. We further focus on the role of miRNAs as regulators of IEGs, which shape the initial steps of signaling-induced transcription. We especially emphasize the role of miRNAs in buffering external noise and maintaining low basal activation of IEGs in the absence of proper stimuli.

microRNAs, Gap Junctional Intercellular Communication and Mesenchymal Stem Cells in Breast Cancer Metastasis

The failed outcome of autologous bone marrow transplantation for breast cancer opens the field for investigations. This is particularly important because the bone marrow could be a major source of cancer cells during tertiary metastasis. This review discusses subsets of breast cancer cells, including those that enter the bone marrow at an early period of disease development, perhaps prior to clinical detection. This population of cells evades chemotherapeutic damage even at high doses. An understanding of this population might be crucial for the success of bone marrow transplants for metastatic breast cancer and for the eradication of cancer cells in bone marrow. In vivo and in vitro studies have demonstrated gap junctional intercellular communication (GJIC) between bone marrow stroma and breast cancer cells. This review discusses GJIC in cancer metastasis, facilitating roles of mesenchymal stem cells (MSCs). In addition, the review addresses potential roles for miRNAs, including those already linked to cancer biology. The literature on MSCs is growing and their links to metastasis are beginning to be significant leads for the development of new drug targets for breast cancer. In summary, this review discusses interactions among GJIC, miRNAs and MSCs as future consideration for the development of cancer therapies.

Optimal management of bone metastases in breast cancer patients

Bone metastasis in breast cancer is a significant clinical problem. It not only indicates incurable disease with a guarded prognosis, but is also associated with skeletal-related morbidities including bone pain, pathological fractures, spinal cord compression, and hypercalcemia. In recent years, the mechanism of bone metastasis has been further elucidated. Bone metastasis involves a vicious cycle of close interaction between the tumor and the bone microenvironment. In patients with bone metastases, the goal of management is to prevent further skeletal-related events, manage complications, reduce bone pain, and improve quality of life. Bisphosphonates are a proven therapy for the above indications. Recently, a drug of a different class, the RANK ligand antibody, denosumab, has been shown to reduce skeletal-related events more than the bisphosphonate, zoledronic acid. Other strategies of clinical value may include surgery, radiotherapy, radiopharmaceuticals, and, of course, effective systemic therapy. In early breast cancer, bisphosphonates may have an antitumor effect and prevent both bone and non-bone metastases. Whilst two important Phase III trials with conflicting results have led to controversy in this topic, final results from these and other key Phase III trials must still be awaited before a firm conclusion can be drawn about the use of bisphosphonates in this setting. Advances in bone markers, predictive biomarkers, multi-imaging modalities, and the introduction of novel agents have ushered in a new era of proactive management for bone metastases in breast cancer.

Steroid receptor and microRNA regulation in cancer

PURPOSE OF REVIEW

Steroid hormone receptors (SHR) are crucial regulators of disease and the basis for clinical intervention in cancers. Recent evidence confirms that microRNAs (miRNAs) impact the pathobiology of hormone-regulated malignancies. Therefore, elucidating miRNA regulation of SHR expression and modulation of miRNAs by SHRs may provide diagnostic biomarkers or therapeutic targets.

RECENT FINDINGS

Estrogen receptor status has been established as a key factor in breast cancer prognosis and treatment. Recent studies detail the interactions between estrogen receptor and miRNAs in cancers. New evidence indicates involvement of miRNAs in the regulation of androgen receptor, progesterone receptor, glucocorticoid receptor in hormone responsive cancers. Several miRNAs regulate the expression of the SHRs, while other miRNAs are themselves regulated by SHR signaling in cancer.

SUMMARY

Cancers have distinct miRNA expression profiles that contribute to the pathobiology of the disease. In hormone-responsive cancers, the regulatory interactions between the SHR and miRNA may contribute to disease progression. The miRNA regulation of estrogen receptor in cancer has been established in estrogen-dependent cancers. The role of miRNAs in regulating progesterone receptor, androgen receptor and glucocorticoid receptor is under investigation with new insights emerging. These interactions can provide prognostic utility as well as the potential for therapeutic intervention in the future.

Epigenetically deregulated microRNA-375 is involved in a positive feedback loop with estrogen receptor alpha in breast cancer cells

Estrogen receptor α (ERα) upregulation causes abnormal cell proliferation in about two thirds of breast cancers, yet understanding of the underlying mechanisms remains incomplete. Here, we show that high expression of the microRNA miR-375 in ERα-positive breast cell lines is a key driver of their proliferation. miR-375 overexpression was caused by loss of epigenetic marks including H3K9me2 and local DNA hypomethylation, dissociation of the transcriptional repressor CTCF from the miR-375 promoter, and interactions of ERα with regulatory regions of miR-375. Inhibiting miR-375 in ERα-positive MCF-7 cells resulted in reduced ERα activation and cell proliferation. A combination of expression profiling from tumor samples and miRNA target prediction identified RASD1 as a potential miR-375 target. Mechanistic investigations revealed that miR-375 regulates RASD1 by targeting the 3' untranslated region in RASD1 mRNA. Additionally, we found that RASD1 negatively regulates ERα expression. Our findings define a forward feedback pathway in control of ERα expression, highlighting new strategies to treat ERα-positive invasive breast tumors.

The aryl hydrocarbon receptor nuclear translocator-interacting protein 2 suppresses the estrogen receptor signaling via an Arnt-dependent mechanism

We explored whether modulation of the estrogen receptor (ER) signaling is possible through an aryl hydrocarbon receptor nuclear translocator (Arnt)-dependent mechanism. We utilized the Arnt-interacting protein 2 (Ainp2) to examine whether the presence of Ainp2 in MCF-7 cells would interfere with the Arnt-mediated ER signaling. We found that Arnt increased the 17 beta-estradiol (E2)-dependent luciferase activity and Ainp2 significantly suppressed this Arnt-mediated luciferase activity. Ainp2 significantly suppressed 25% of the E2- and Arnt-dependent up-regulation of the GREB1 message. No suppression of the ER target gene expression by Ainp2 was detected in Arnt-knockdown MCF-7 cells and in Arnt-independent ER signaling. Although Ainp2 did not interact with ER alpha and ER beta, it suppressed the ER alpha::Arnt interaction and reduced the E2-driven recruitment of Arnt to the GREB1 promoter. We concluded that Ainp2 suppresses the ER signaling by not allowing Arnt to participate in the ER-dependent, Arnt-mediated activation of gene transcription.

miRNAs give worms the time of their lives: small RNAs and temporal control in Caenorhabditis elegans

Alteration in the timing of particular developmental events can lead to major morphological changes that have profound effects on the life history of an organism. Insights into developmental timing mechanisms have been revealed in the model organism Caenorhabditis elegans, in which a regulatory network of heterochronic genes times events during larval development, ensuring that stage-specific programs occur in the appropriate sequence and on schedule. Developmental timing studies in C. elegans led to the landmark discovery of miRNAs and continue to enhance our understanding of the regulation and activity of these small regulatory molecules. Current views of the heterochronic gene pathway are summarized here, with a focus on the ways in which miRNAs contribute to temporal control and how miRNAs themselves are regulated. Finally, the conservation of heterochronic genes and their functions in timing, as well as their related roles in stem cells and cancer, are highlighted.