A functional polymorphism in the miR-146a gene and age of familial breast/ovarian cancer diagnosis

Evaluation of microRNA expression profiles and their associations with risk alleles in lymphoblastoid cell lines of familial ovarian cancer

Interindividual variations of microRNA expression are likely to influence the expression of microRNA target genes and, therefore, contribute to phenotypic differences in humans, including cancer susceptibility. Whether microRNA expression variation has any role in ovarian cancer development is still unknown. Here, we evaluated microRNA expression profiles in lymphoblastoid cell lines from 74 women with familial ovarian cancer and 47 unrelated controls matched on gender and race. We found that the cases and unrelated controls can be clustered using 95 differentially expressed microRNAs with 91% accuracy. To assess the potential implications of microRNAs in ovarian cancer, we investigated the associations between microRNA expression and seven ovarian cancer risk variants discovered from genome-wide association studies (GWAS), namely, rs3814113 on 9p22.2, rs2072590 on 2q31, rs2665390 on 3q25, rs10088218, rs1516982, rs10098821 on 8q24.21 and rs2363956 on 19p13. We observed 130 significant associations at a permutation level of 0.01. Compared with other risk variants, rs3814113 and rs2072590 had the greatest number of significant associations (68 and 37, respectively). Interestingly, 14 microRNAs that were associated with ovarian cancer risk alleles belong to five microRNA clusters. The most notable cluster is the tumorigenic miR-17-92 cluster with five microRNAs, all of which are significantly associated with rs3814113. Using pathway analysis, several key biological pathways were significantly overrepresented, such as cellular response to stress (P = 2.87 × 10(-06)), etc. Further characterization of significant associations between microRNAs and risk alleles could facilitate the understanding of the functions of these GWAS discovered risk alleles in the genetic etiology of ovarian cancer.

Increased risk of breast cancer associated with CC genotype of Has-miR-146a Rs2910164 polymorphism in Europeans

BACKGROUND

Emerging evidence suggests that microRNAs play a critical role in the pathogenesis of breast cancer. Several molecular epidemiological studies were conducted in recent years to evaluate the association between has-miR-146a rs2910164 polymorphism and breast cancer risk in diverse populations. However, the results remain conflicting rather than conclusive.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a meta-analysis of 6 case-control studies that included 4238 breast-cancer cases and 4469 case-free controls. We assessed the strength of the association, using odds ratios (ORs) with 95% confidence intervals (CIs). Overall, this meta-analysis showed that the rs2910164 polymorphism was not associated with a significantly increased risk of breast cancer in all genetic models (for GC vs GG: OR = 1.00, 95% CI = 0.90-1.09, P(heterpgeneity) = 0.364; for CC vs GG: OR = 1.16, 95% CI = 0.98-1.36, P(heterpgeneity) = 0.757; for GC+CC vs GG: OR = 1.02, 95% CI = 0.93-1.12, P(heterpgeneity) = 0.562; for CC vs GC+GG: OR = 1.10, 95% CI = 0.96-1.26, P(heterpgeneity) = 0.441). However, in the stratified analysis by ethnicity, we found the rs2910164 polymorphism was associated with increased breast cancer risk among Europeans in homozygote comparison (CC vs. GG: OR = 1.29, 95%CI = 1.02-1.63, P(heterpgeneity) = 0.950, P = 0.032) and recessive model (CC vs. GC+GG: OR = 1.31, 95%CI = 1.05-1.65, P(heterpgeneity) = 0.839, P = 0.019). No publication bias was found in the present study.

CONCLUSIONS/SIGNIFICANCE

This meta-analysis suggests, for the first time, that the CC homozygote of rs2910164 may contribute to breast cancer susceptibility in Europeans.

Increased risk of breast cancer associated with CC genotype of Has-miR-146a Rs2910164 polymorphism in Europeans

Background

Emerging evidence suggests that microRNAs play a critical role in the pathogenesis of breast cancer. Several molecular epidemiological studies were conducted in recent years to evaluate the association between has-miR-146a rs2910164 polymorphism and breast cancer risk in diverse populations. However, the results remain conflicting rather than conclusive.

Methodology/Principal findings

We performed a meta-analysis of 6 case-control studies that included 4238 breast-cancer cases and 4469 case-free controls. We assessed the strength of the association, using odds ratios (ORs) with 95% confidence intervals (CIs). Overall, this meta-analysis showed that the rs2910164 polymorphism was not associated with a significantly increased risk of breast cancer in all genetic models (for GC vs GG: OR = 1.00, 95% CI = 0.90−1.09, P_{heterpgeneity} = 0.364; for CC vs GG: OR = 1.16, 95% CI = 0.98−1.36, P_{heterpgeneity} = 0.757; for GC+CC vs GG: OR = 1.02, 95% CI = 0.93−1.12, P_{heterpgeneity} = 0.562; for CC vs GC+GG: OR = 1.10, 95% CI = 0.96−1.26, P_{heterpgeneity} = 0.441). However, in the stratified analysis by ethnicity, we found the rs2910164 polymorphism was associated with increased breast cancer risk among Europeans in homozygote comparison (CC vs. GG: OR = 1.29, 95%CI = 1.02−1.63, P_{heterpgeneity} = 0.950, P = 0.032) and recessive model (CC vs. GC+GG: OR = 1.31, 95%CI = 1.05−1.65, P_{heterpgeneity} = 0.839, P = 0.019). No publication bias was found in the present study.

Conclusions/Significance

This meta-analysis suggests, for the first time, that the CC homozygote of rs2910164 may contribute to breast cancer susceptibility in Europeans.

Environmental chemical exposures and human epigenetics

Every year more than 13 million deaths worldwide are due to environmental pollutants, and approximately 24% of diseases are caused by environmental exposures that might be averted through preventive measures. Rapidly growing evidence has linked environmental pollutants with epigenetic variations, including changes in DNA methylation, histone modifications and microRNAs. Environ mental chemicals and epigenetic changes All of these mechanisms are likely to play important roles in disease aetiology, and their modifications due to environmental pollutants might provide further understanding of disease aetiology, as well as biomarkers reflecting exposures to environmental pollutants and/or predicting the risk of future disease. We summarize the findings on epigenetic alterations related to environmental chemical exposures, and propose mechanisms of action by means of which the exposures may cause such epigenetic changes. We discuss opportunities, challenges and future directions for future epidemiology research in environmental epigenomics. Future investigations are needed to solve methodological and practical challenges, including uncertainties about stability over time of epigenomic changes induced by the environment, tissue specificity of epigenetic alterations, validation of laboratory methods, and adaptation of bioinformatic and biostatistical methods to high-throughput epigenomics. In addition, there are numerous reports of epigenetic modifications arising following exposure to environmental toxicants, but most have not been directly linked to disease endpoints. To complete our discussion, we also briefly summarize the diseases that have been linked to environmental chemicals-related epigenetic changes.

Catalog of microRNA seed polymorphisms in vertebrates

MicroRNAs (miRNAs) are a class of non-coding RNA that plays an important role in posttranscriptional regulation of mRNA. Evidence has shown that miRNA gene variability might interfere with its function resulting in phenotypic variation and disease susceptibility. A major role in miRNA target recognition is ascribed to complementarity with the miRNA seed region that can be affected by polymorphisms. In the present study, we developed an online tool for the detection of miRNA polymorphisms (miRNA SNiPer) in vertebrates (http://www.integratomics-time.com/miRNA-SNiPer) and generated a catalog of miRNA seed region polymorphisms (miR-seed-SNPs) consisting of 149 SNPs in six species. Although a majority of detected polymorphisms were due to point mutations, two consecutive nucleotide substitutions (double nucleotide polymorphisms, DNPs) were also identified in nine miRNAs. We determined that miR-SNPs are frequently located within the quantitative trait loci (QTL), chromosome fragile sites, and cancer susceptibility loci, indicating their potential role in the genetic control of various complex traits. To test this further, we performed an association analysis between the mmu-miR-717 seed SNP rs30372501, which is polymorphic in a large number of standard inbred strains, and all phenotypic traits in these strains deposited in the Mouse Phenome Database. Analysis showed a significant association between the mmu-miR-717 seed SNP and a diverse array of traits including behavior, blood-clinical chemistry, body weight size and growth, and immune system suggesting that seed SNPs can indeed have major pleiotropic effects. The bioinformatics analyses, data and tools developed in the present study can serve researchers as a starting point in testing more targeted hypotheses and designing experiments using optimal species or strains for further mechanistic studies.

Implication of miRNA in the diagnosis and treatment of breast cancer

Breast cancer (BC) comprises a group of different diseases characterized by changes in tissue structure and gene expression. Recent advances in molecular biology have shed new light on the participation of genes and their products in the biology of BC. MicroRNAs (miRNAs) are small noncoding endogenous RNA molecules that appear to modulate the expression of more than a third of human genes, and their implications in cancer have grasped the attention of the scientific community. Recently, several studies have described the association between miRNA expression profiles and pathological and clinical BC features. Moreover, these molecules represent a new type of molecular marker that can identify prognosis and guide the management of BC patients. With the increasing understanding of miRNA networks and their impact in the biology of BC, as well as the development of viable strategies to modulate specific miRNAs, we could improve the treatment of this disease.

MicroRNAs: toward the clinic for breast cancer patients

Expression of microRNAs (miRNAs) has been found to be deregulated in all human cancers, where they may behave either as oncogenes or as tumor-suppressor genes. In the last 5 years, miRNA investigations in breast cancer represented an exciting area of discovery, which produced new knowledge on the molecular basis of this disease, tools for molecular classification, and new markers with diagnostic and prognostic relevance, as well as the discovery of novel breast cancer-predisposing genes. In this review, we describe current knowledge of the role of microRNAs in breast cancer.

MicroRNAs in mutagenesis, genomic instability, and DNA repair

MicroRNAs (miRNAs) are aiding our understanding of cancer biology, and are now coming close to therapeutic use as well. Here, we focus specifically on the interaction between miRNAs and genomic instability. MiRNA regulation is essential to many cellular processes, and escape from this regulatory network seems to be a common characteristic of malignant transformation. Genomic instability may preferentially target miRNAs either because of selective pressure or because of inherent vulnerability related to their location near fragile sites. Furthermore, disruption of miRNA processing elements affords a more global release from miRNA regulation. Finally, we review how miRNAs function as both effectors and modulators of the DNA damage response, intricately weaved with traditional elements such as ATM, P53, and MMR. Thus, miRNAs are important substrates for genomic instability and play a crucial role in cellular DNA sensing and repair mechanisms.

Association between the rs2910164 polymorphism in pre-mir-146a and oral carcinoma progression

MicroRNAs are short non-coding RNAs that regulate gene expression by RNA interference. Oral squamous cell carcinoma (OSCC) is a prevalent malignancy worldwide. miR-146a has been reported to regulate Toll-like receptors and cytokine signaling, which are both crucial for inflammation and oncogenesis. This study identifies that areca nut extract, TNFα and TGFβ up-regulates miR-146a in OSCC cells. The increased expression of miR-146a enhanced the oncogenicity of OSCC cells. In addition, a G to C polymorphism (rs2910164), which is located in the pre-miR-146a and has been associated with functional alterations in miR-146a, was significantly more prevalent among OSCC patients having more advanced nodal involvement. Our analysis also suggested a higher miR-146a expression in OSCC tissues of patients carrying C polymorphism. The present study concluded a higher prevalence of the pre-mir-146a C-variant was associated with OSCC progression in patients with this disease.

A functional polymorphism in the pre-miR-146a gene is associated with risk and prognosis in adult glioma

MicroRNAs (miRNAs) are non-coding RNAs that function as post-transcriptional regulators of tumor suppressors and oncogenes. Single nucleotide polymorphisms (SNPs) in miRNAs may contribute to carcinogenesis by altering expression of miRNAs and their targets. A G>C polymorphism (rs2910164) in the miR-146a precursor sequence leads to a functional change associated with the risk for numerous malignancies. A role for this SNP in glioma pathogenesis has not yet been examined. We investigated whether rs2910164 genotypes influence glioma risk and prognosis in a multi-center case-control study comprised of 593 Caucasian glioma cases and 614 community-based controls. Unconditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for rs2910164 genotypes according to case status. Cox proportional hazards regression modeling was used to estimate hazards ratios (HR) and 95% CIs according to genotype among glioblastomas, the most lethal glioma subtype. An increased glioma risk was observed among rs2910164 minor allele (C) carriers (per allele OR (95% CI) = 1.22 (1.01-1.46, p (trend) = 0.039)). The association was stronger among older subjects carrying at least one copy of the C allele (OR (95% CI) = 1.38 (1.04-1.83, P = 0.026). Mortality was increased among minor allele carriers (HR (95% CI) = 1.33 (1.03-1.72, P = 0.029)), with the association largely restricted to females (HR (95% CI) = 2.02 (1.28-3.17, P = 0.002)). We provide novel data suggesting rs2910164 genotype may contribute to glioma susceptibility and outcome. Future studies are warranted to replicate these findings and characterize mechanisms underlying these associations.

MicroRNAs in thyroid cancer

CONTEXT

Traditionally, factors predisposing to diseases are either genetic ("nature") or environmental, also known as lifestyle-related ("nurture"). Papillary thyroid cancer is an example of a disease where the respective roles of these factors are surprisingly unclear.

EVIDENCE ACQUISITION

Original articles and reviews summarizing our current understanding of the role of microRNA in thyroid tumorigenesis are reviewed and evaluated.

CONCLUSION

The genetic predisposition to papillary thyroid cancer appears to consist of a variety of gene mutations that are mostly either of low penetrance and common or of high penetrance but rare. Moreover, they likely interact with each other and with environmental factors. The culpable genes may not be of the traditional, protein-coding type. A limited number of noncoding candidate genes have indeed been described, and we propose here that the failure to find mutations in traditional protein-coding genes is not coincidental. Instead, a more likely hypothesis is that changes in the expression of multiple regulatory RNA genes, e.g. microRNAs, may be a major mechanism. Our review of the literature strongly supports this notion in that a polymorphism in one microRNAs (miR-146a) predisposes to thyroid carcinoma, whereas numerous other microRNAs are involved in signaling (mainly PTEN/PI3K/AKT and T3/THRB) that is central to thyroid carcinogenesis.

Management of hereditary ovarian cancer

Mutations in BRCA1 and BRCA2 genes account for the majority of hereditary breast and ovarian cancers. Approximately 10% of cases of ovarian cancer are due to germline mutations in BRCA1 and BRCA2. Ovarian cancer associated with BRCA1 and BRCA2 mutations has a distinct histological phenotype. This type of cancer is predominantly of serous or endometrioid histology and is high grade. Patients with BRCA1 or BRCA2 mutations should be offered risk-reducing salpingo-oophorectomy by age 40 years, or when childbearing is complete. Nowadays there are no differences between the treatments provided for sporadic and hereditary ovarian cancer, although there are indications that targeted therapy is effective in women with BRCA1/BRCA2-associated tumors. Retrospective studies reveal a high level of sensitivity to platinum agents in BRCA-associated tumors and initial trials show good efficacy and tolerability for polyADP-ribose polymerase inhibitors in mutation carriers with advanced ovarian cancers. These agents might also potentially be used in chemoprevention. Authors review the current management of hereditary ovarian cancer. Orv. Hetil., 2011, 152, 1596–1608.

[Association of human microRNA related genetic variations with cancer]

microRNAs (miRNAs) are a highly conserved class of small noncoding RNAs that regulate gene expression by post-transcriptional degradation or translational repression. miRNAs are involved in the regulation of cell apoptosis, proliferation, differentiation and other physiological processes, and are closely related with the development of cancer. More recently, it has been proposed that the presence of genetic variations (e.g., single nucleotide polymorphism and copy number variation) in microRNA genes, their biogenesis pathway and target binding sites affect the miRNA processing machinery and targeting, and have a significant genetic effect. In this review, we focus on the miRNA-related genetic variations and cancer susceptibility and progression.

Has-miR-146a polymorphism (rs2910164) and cancer risk: a meta-analysis of 19 case-control studies

Epidemiological studies have evaluated the association between has-miR-146a polymorphism (rs2910164) and cancer risk. However, published data are still inconclusive. Here, we performed a meta-analysis to assess the relationship between has-miR-146a polymorphism (rs2910164) and cancer susceptibility until May 8, 2010. Nineteen published case-control studies including a total of 10,496 cases and 12,885 controls were acquired. Overall, Increased cancer risk was found in domain model (OR = 1.18, 95% CI: 1.03-1.35) rather than in other genetic models when all studies were pooled into the meta-analysis. Stratified analysis shown that significant association between rs2910164 polymorphism and cancer susceptibility was present in Asians (OR = 1.14, 95% CI: 1.01-1.29 for CG vs. CC; OR = 1.19, 95% CI: 1.03-1.39 for GG + CG vs. CC), but not in Caucasian populations. In the subgroup analysis by cancer types, no significantly increased risk of breast, gastric, prostate or bladder cancer were found in any of the genetic models. In summary, this meta-analysis suggests that has-miR-146a polymorphism (rs2910164) is associated with increased cancer susceptibility in Asians. However, further well-designed studies with large sample size will be necessary to validate the risk identified in the current meta-analysis.

The rs2910164:G>C SNP in the MIR146A gene is not associated with breast cancer risk in BRCA1 and BRCA2 mutation carriers

The rs2910164:G>C SNP is located in the gene for miR-146a, a microRNA that binds the 3' UTR of the BRCA1 transcript. Preliminary data based on the analysis of a small number of cases suggested that this single nucleotide polymorphism (SNP) might be associated with the age of onset of familial breast and ovarian cancer. This effect was not confirmed on a large series of familial breast cancer cases negative for a BRCA1 or BRCA2 mutation. We show here a lack of association of the rs2910164:G>C SNP with breast cancer risk in a series of 1,166 BRCA1 and 560 BRCA2 mutation carriers. In conclusion, the polymorphism in the miR-146a gene is unlikely to be of substantial significance regarding breast cancer risk.

No association of pre-microRNA-146a rs2910164 polymorphism and risk of hepatocellular carcinoma development in Turkish population: a case-control study

AIM

MicroRNAs (miRNAs) are an abundant class of small non-protein coding RNAs with posttranscriptional regulatory functions as tumor suppressors and oncogenes. Aberrant expression and structural alteration of miRNAs are considered to participate in tumorigenesis and cancer development. It has been suggested that the presence of single nucleotide polymorphisms in precursor miRNAs (pre-miRNAs) can alter miRNA processing, expression, and/or binding to target mRNA and represent another type of genetic variability that can contribute to the susceptibility of human cancers. A G/C polymorphism (rs2910164), which is located in the sequence of miR-146a precursor, results in a change from G:U to C:U in its stem region.

METHODS

To determine the association of the miR-146a rs2910164 polymorphism on the risk of hepatocellular carcinoma (HCC) development in Turkish population, a hospital-based case-control study was designed consisting of 222 subjects with HCC and 222 cancer-free control subjects matched on age, gender, smoking and alcohol status. The genotype frequency of miR-146a rs2910164 polymorphism was determined by using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay.

RESULTS

No statistically significant differences were found in the allele or genotype distributions of the miR-146a rs2910164 polymorphism among HCC and cancer-free control subjects (p>0.05).

CONCLUSION

Our results demonstrate that the miR-146a rs2910164 polymorphism has no major role in genetic susceptibility to hepatocellular carcinogenesis, at least in the population studied here. Independent studies are needed to validate our findings in a larger series, as well as in patients of different ethnic origins.

MicroRNA sequence and expression analysis in breast tumors by deep sequencing

MicroRNAs (miRNA) regulate many genes critical for tumorigenesis. We profiled miRNAs from 11 normal breast tissues, 17 noninvasive, 151 invasive breast carcinomas, and 6 cell lines by in-house-developed barcoded Solexa sequencing. miRNAs were organized in genomic clusters representing promoter-controlled miRNA expression and sequence families representing seed sequence-dependent miRNA target regulation. Unsupervised clustering of samples by miRNA sequence families best reflected the clustering based on mRNA expression available for this sample set. Clustering and comparative analysis of miRNA read frequencies showed that normal breast samples were separated from most noninvasive ductal carcinoma in situ and invasive carcinomas by increased miR-21 (the most abundant miRNA in carcinomas) and multiple decreased miRNA families (including miR-98/let-7), with most miRNA changes apparent already in the noninvasive carcinomas. In addition, patients that went on to develop metastasis showed increased expression of mir-423, and triple-negative breast carcinomas were most distinct from other tumor subtypes due to upregulation of the mir~17-92 cluster. However, absolute miRNA levels between normal breast and carcinomas did not reveal any significant differences. We also discovered two polymorphic nucleotide variations among the more abundant miRNAs miR-181a (T19G) and miR-185 (T16G), but we did not identify nucleotide variations expected for classical tumor suppressor function associated with miRNAs. The differentiation of tumor subtypes and prediction of metastasis based on miRNA levels is statistically possible but is not driven by deregulation of abundant miRNAs, implicating far fewer miRNAs in tumorigenic processes than previously suggested.

Expression of microRNA 210 associates with poor survival and age of tumor onset of soft-tissue sarcoma patients

Expression of microRNAs can affect age of tumor onset and prognosis of cancer patients. However, nothing is known about the effects of microRNAs on altered age of cancer onset and disease-specific survival of soft-tissue sarcoma (STS) patients. The levels of miR-210, also known as hypoxia-regulated microRNA, were analyzed by quantitative real-time (RT)-PCR in the tumors of 78 STS patients. The patients were stratified according to their microRNA levels with low, intermediate and high expression levels and the association of microRNA expression and patients' survival was analyzed using multivariate Cox's regression hazard analyses. A significant correlation between an intermediate miR-210 expression and disease-specific death of STS patients [relative risk (RR) = 3.19; p = 0.018] was observed compared with patients with high expression levels in their tumors. Interestingly, the association between an intermediate expression of miR-210 and a poor prognosis was only significant in female STS patients (RR = 11.28; p = 0.010), but not observed in male individuals. Furthermore, the expression of miR-210 showed a significant association with the age of tumor onset in a gender-specific manner. Specifically, male patients with an intermediate expression of miR-210 associated with a 9.6-year later age of tumor onset (p = 0.017) compared with males with a low expression of miR-210 in their tumors. However, no significant differences in the female patients were observed. This study provides the first evidence of a correlation of expression levels of a single microRNA (miR-210) with the prognosis and age of tumor onset in a gender-specific manner in STS patients.

Clinical significance of miR-146a in gastric cancer cases

PURPOSE

The profiles of microRNAs change significantly in gastric cancer. MiR-146a is reported to be a tumor suppressor in pancreatic cancer, breast cancer, and prostate cancer. We investigated the clinical significance of miR-146a in gastric cancer, in particular focusing on hypothetical miR-146a target genes, such as epidermal growth factor receptor (EGFR) and interleukin-1 receptor-associated kinase (IRAK1).

EXPERIMENTAL DESIGN

We examined miR-146a levels in 90 gastric cancer samples by q-real-time (qRT)-PCR and analyzed the association between miR-146a levels and clinicopathologic factors and prognosis. The regulation of EGFR and IRAK1 by miR-146a was examined with miR-146a-transfected gastric cancer cells. Moreover, we analyzed the association between miR-146a levels and the G/C single nucleotide polymorphism (SNP) within pre-miR-146a seed sequences in 76 gastric cancer samples, using direct sequencing of genomic DNA.

RESULTS

In 90 clinical samples of gastric cancer, miR-146a levels in cancer tissues were significantly lower than those in the corresponding noncancerous tissue (P < 0.001). Lower levels of miR-146a were associated with lymph node metastasis and venous invasion (P < 0.05). Moreover, a lower level of miR-146a was an independent prognostic factor for overall survival (P = 0.003). Ectopic expression of miR-146a inhibited migration and invasion and downregulated EGFR and IRAK1 expression in gastric cancer cells. In addition, G/C SNP within the pre-miR-146a seed sequence significantly reduced miR-146a levels in the GG genotype compared with the CC genotype.

CONCLUSIONS

MiR-146a contains an SNP, which is associated with mature miR-146a expression. MiR-146a targeting of EGFR and IRAK1 is an independent prognostic factor in gastric cancer cases.

Effects of common polymorphisms rs11614913 in miR-196a2 and rs2910164 in miR-146a on cancer susceptibility: a meta-analysis

Background

MicroRNAs regulate gene expression at the post-transcriptional level and involved in diverse biological and pathological processes, including tumorigenesis. Rs11614913 in miR-196a2 and rs2910164 in miR-146a are shown to associate with increased/decreased cancer risk. We performed a meta-analysis to systematically summarize the possible association.

Methodology/Principal Findings

We assessed published studies of the association between these microRNA polymorphisms and cancer risk from eleven studies with 16,771 subjects for miR-196a2 and from ten studies with 15,126 subjects for miR-146a. As for rs11614913, the contrast of homozygote (TT vs CC: OR = 0.92, 95% CI = 0.85–0.99, P_{heterogeneity} = 0.45), allele (T vs C: OR = 0.96, 95% CI = 0.92–0.99, P_{heterogeneity} = 0.61) and recessive model (OR = 0.90, 95% CI = 0.84–0.97, P_{heterogeneity} = 0.50) produced statistically association. Subgroup analysis by ethnicity, statistically significantly decreased cancer risks were found among Asians for allele contrast (OR = 0.95, 95% CI = 0.90–0.99, P_{heterogeneity} = 0.74) and the recessive genetic model (OR = 0.90, 95% CI = 0.82–0.98, P_{heterogeneity} = 0.85). According to subgroup analysis by tumor types, the protective effect of C/T polymorphism was only found in breast cancer under allele contrast (T vs C: OR = 0.94, 95% CI = 0.88–0.99, P_{heterogeneity} = 0.26). For rs2910164, no significant associations were found among overall analysis model with relatively large heterogeneity. Through the stratified analysis, heterogeneity decreased significantly. In the subgroup analyses by cancer types, the C allele of rs2910164 was associated with protection from digestive cancer in allele contrast (C vs G: OR = 0.86, 95% CI = 0.77–0.96, P_{heterogeneity} = 0.51).

Conclusions/Significance

Our meta-analysis suggests that the rs11614913 most likely contributes to decreased susceptibility to cancer, especially in Asians and breast cancer. Besides, the C allele of the rs2910164 might be associated with a protection from digestive cancer.

Association between SNPs in pre-miRNA and risk of chronic obstructive pulmonary disease

OBJECTIVES

Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airway obstruction and persistent chronic airway inflammation and is influenced by genetic and environmental factors. This study aimed to explore the genetic aspect of its initial occurrence.

DESIGN AND METHODS

We conducted a case-control study of 432 COPD patients and 511 control subjects frequency-matched in age and gender distribution. We genotyped three single nucleotide polymorphisms (SNPs) in pre-miRNAs using a PCR-RFLP assay and evaluated their relevance to COPD susceptibility.

RESULTS

We found that the TT genotype and T allele of miR-196a2 rs11614913 were significantly associated with a decreased risk for COPD, compared with the CC genotype and C allele. Similarly, the GG genotype and G allele of miR-499 rs3746444 were associated with a decreased risk for COPD, compared with the AA genotype and A allele.

CONCLUSIONS

These findings suggest that both rs11614913 and rs3746444 may be involved in susceptibility to COPD.

Cancer microRNAs: from subtype profiling to predictors of response to therapy

MicroRNAs (miRNAs) are key regulators of gene expression that regulate important oncogenes and tumor suppressors. Many miRNAs can also act as oncogenes or tumor suppressors, and thus the altered expression of miRNAs is a hallmark of many cancer types. Dysregulated miRNAs provide a potentially powerful new tool that could be used to enable the characterization of tumor environments and identify novel and important oncogenic pathways. More recently, there has been growing interest in the field of miRNAs as biomarkers of cancer risk, diagnosis and response to therapy. Understanding the associations between miRNA expression and cancer phenotypes, and the potential of miRNA profiling in clinical applications, promises to be highly rewarding in the field of cancer research.

Polymorphism of the pre-miR-146a is associated with risk of cervical cancer in a Chinese population

OBJECTIVE

MicroRNAs are tiny non-coding RNAs that reportedly play an important role in numerous physiological processes. A G>C polymorphism (rs2910164) is located on the passenger strand of the precursor of miR-146a, which could alter mature miR-146a expression. We hypothesized that a possible association exists between miR-146a gene polymorphisms and cervical cancer risk in a population-based control study of female residents in Jiangsu Province.

METHODS

The subjects included 447 cervical cancer cases and 443 cancer-free controls with frequency matched by age. We genotyped the functional polymorphism of miR-146a (rs2910164) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, and used a sample of 24 cervical cancer tissue to test the expression of miR-146a by real-time quantitative reverse transcription.

RESULTS

Our study indicated that the subjects carrying GG homozygote had a 1.496-fold increased risk than those carrying CG/CC genotypes (95% CI=1.068-2.095). Moreover, miR-146a quantification showed that the carriers of GG genotype had obviously more reduced miR-146a expression level compared with the carriers of CC genotype.

CONCLUSION

Our study suggests that the risk of cervical cancer in a Chinese population partly results from miRNA-146a expression deviation in vivo, being caused by common polymorphism in miR-146a. This is an initial study to indicate that miR-146a (rs2910164) might contribute to cervical cancer susceptibility.

Down-regulation of BRCA1 expression by miR-146a and miR-146b-5p in triple negative sporadic breast cancers

Germ-line mutations in the BRCA1 gene strongly predispose women to breast cancer (lifetime risk up to 80%). Furthermore, the BRCA1 protein is absent or present at very low levels in about one third of sporadic breast cancers. However, the mechanisms underlying BRCA1 somatic inactivation appear multiple and are still not fully understood. We report here the involvement of miR-146a and miR-146b-5p that bind to the same site in the 3′UTR of BRCA1 and down-regulate its expression as demonstrated using reporter assays. This was further confirmed with the endogenous BRCA1 gene by transfecting microRNA (miRNA) precursors or inhibitors in mammary cell lines. This down-regulation was accompanied by an increased proliferation and a reduced homologous recombination rate, two processes controlled by BRCA1. Furthermore, we showed that the highest levels of miR-146a and/or miR-146b-5p are found in basal-like mammary tumour epithelial cell lines and in triple negative breast tumours, which are the closest to tumours arising in carriers of BRCA1 mutations. This work provides further evidence for the involvement of miRNAs in sporadic breast cancer through down-regulation of BRCA1.

A functional varient in microRNA-146a is associated with risk of esophageal squamous cell carcinoma in Chinese Han

MicroRNAs are a new class of non-proteincoding, small RNAs that function as tumor suppressors or oncogenes. They participate in diverse biological pathways and function as gene regulators. A G>C polymorphism (rs2910164), which is located in the sequence of miR-146a precursor, results in a change from G:U to C:U in its stem region. However, it remains largely unknown whether this single nucleotide polymorphism (SNP) may alter esophageal squamous cell carcinoma (ESCC) susceptibility. In the current study, we evaluated association between rs2910164 and ESCC susceptibility in a case-control study of 444 sporadic ESCC patients and 468 matched cancer-free controls in a Chinese Han population. Compared with rs2910164 variant genotype CC, genotype GG was associated with increased risk of ESCC (Odds Ratio, 2.39, 95% Confidence Interval, 1.36-4.20). In the smokers, the risk of rs2910164 GG genotype was more notable (Odds Ratio, 3.17, 95% Confidence Interval, 1.71-4.46). In the stratification analyses, we also found there was a strong correlation between rs2910164 C/G variant and the clinical TNM stage (P < 0.01). These findings suggest that this functional SNP in pre-miR-146a could contribute to ESCC susceptibility and clinical outcome.

A variant in microRNA-196a2 is associated with susceptibility to hepatocellular carcinoma in Chinese patients with cirrhosis

AIMS

Cirrhosis is an important risk factor for hepatocellular carcinoma (HCC) in China, while little is known of the genetic susceptibility to hepatocarcinogenesis. Traditional approaches to identification of novel genetic predisposition genes have focused on protein encoding genes. There is evidence to suggest that microRNAs (miRNA) may play an important role in tumorigenesis. Recent studies have implicated that the rs11614913 SNP in miR-196a2 may be associated with susceptibility to lung cancer, congenital heart disease, breast cancer, as well as reduced survival in non-small cell lung cancer. This study aims to assess whether this functional polymorphism can influence susceptibility to and the progression of cirrhosis-related HCC.

METHODS

532 patients with hepatic cirrhosis (310 patients with HCC and 222 patients without HCC) were enrolled. DNA was extracted from blood specimens, and miR-196a2 polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In addition, tumour tissues of liver (n=59) were obtained from the studied HCC patients for measurement of miR-196a expression levels.

RESULTS

The frequency of the CC genotype among HCC patients was higher than that in the control group, implying that the cirrhotic patients with the CC genotype or C allele containing genotypes (CT and CC) may have a higher risk of HCC. However, in a subsequent analysis of the association between this polymorphism and clinicopathological characteristics, there was an association between rs11614913 genotype and tumour size (p=0.046), but not with tumour number, grade, stage, invasiveness or Child-Pugh grade. In a genotype-phenotype correlation analysis using 59 tumour tissues of liver, rs11614913 CC or carrying at least one C allele was associated with significantly increased mature miR-196a expression (p=0.006 or =0.002).

CONCLUSIONS

Our results suggest, for the first time, that miR-196a2 polymorphism may contribute to cirrhosis-related HCC susceptibility in Chinese patients through influencing mature miR-196a expression.

The role of microRNAs in ovarian cancer initiation and progression

Epithelial ovarian cancer (EOC) has the highest mortality rate of all gynaecological cancers. One of the greatest impediments to improving outcome is an incomplete understanding of the molecular underpinnings of EOC pathogenesis and progression. Recent studies suggest that microRNAs (miRNAs) are involved in ovarian tumorigenesis and cancer development. Several miRNA profiling studies have identified some consensus aberrantly expressed miRNAs in EOC tissues, and these EOC-related miRNAs may play critical roles in the pathogenesis and progression of EOC. Moreover, some of the miRNAs may have diagnostic or prognostic significance. In this review, recent progress to reveal the role of miRNAs in EOC will be addressed, and a model for miRNA functions in ovarian cancer initiation and progression will be proposed.

Oncogenic microRNAs (OncomiRs) as a new class of cancer biomarkers

Small non-coding RNAs (microRNAs or miRs) represent one of the most fertile areas of cancer research and recent advances in the field have prompted us to reconsider the traditional concept of cancer. Some miRs exert negative control over the expression of numerous oncoproteins in normal cells and consequently their deregulation is believed to be an important mechanism underlying cancer development and progression. Owing to their distinct patterns of expression associated with cancer type, remarkable stability and presence in blood and other body fluids, miRs are considered to be highly promising cancer biomarkers. The identification of "miR signatures" associating cancer cell phenotypes with disease outcome and specific risk factor exposures will undoubtedly open new avenues for early diagnosis and therapy of cancer, as well as for the development of novel strategies for cancer prevention.

Common genetic polymorphisms in pre-microRNAs and risk of cervical squamous cell carcinoma

MicroRNAs (miRNAs) function as gene regulator and they participate in diverse biological pathways. Common single nucleotide polymorphisms (SNPs) in pre-microRNAs may change their property through altering miRNAs expression and/or maturation. We conducted a pilot study to test whether SNPs in pre-microRNAs were associated with cervical squamous cell carcinoma (CSCC). Genotypes of three SNPs in pre-miRNAs (hsa-miR-196a2 rs11614913 C/T, hsa-miR-499 rs3746444 A/G, and hsa-miR-146a rs2910164 G/C) in 226 CSCC patients and 309 control subjects were determined with the use of PCR-restriction fragment length polymorphism (RFLP) assay. Significantly increased CSCC risks were found to be associated with G allele of rs3746444 and G allele of rs2910164 (P = 0.017, OR = 1.454, and P = 0.016, OR = 1.355, respectively). Increased CSCC risks were associated with them in different genetic model (P = 0.0004, OR = 1.98 for rs3746444 in an overdominant model, and P = 0.024, OR = 2.10 for rs2910164 in a codominant model, respectively). Results of stratified analyses revealed that rs2910164 is associated with tumor differentiation and lymph node status (P = 0.043, OR = 2.08, and a borderline P = 0.057, OR = 0.41, respectively). No association between rs11614913 and CSCC risk was observed. The present study provides evidence that rs3746444 and rs2910164 are associated with CSCC, indicating that common genetic polymorphisms in pre-microRNAs contribute to the pathogenesis of CSCC.

Genetic variants within miR-126 and miR-335 are not associated with breast cancer risk

MicroRNAs (miRNAs) are 20-22 nt non-coding RNAs which promote the degradation of target mRNAs or repression of the translation of mRNAs by sequence specific targeting. Many miRNAs are considered as oncogenes or tumor suppressors. MiR-126 and miR-335 play roles in the suppression of breast cancer metastasis by inhibiting tumor growth, proliferation, and cell invasion. The effects of SNPs within the two miRNAs are still unknown. In our study, we analyzed two SNPs, rs4636297 within miR-126 and rs41272366 within miR-335, in three study populations for a putative association with breast cancer risk. We compared the genotype and allele frequencies of rs4636297 and rs41272366 in 2854 cases versus 3188 controls of the three study populations independently and combined. None of the performed analyses showed statistically significant results. In conclusion, our data suggest that the two genetic variants within miR-126 and miR-335 are not associated with breast cancer risk.

Polymorphisms affecting micro-RNA regulation and associated with the risk of dietary-related cancers: a review from the literature and new evidence for a functional role of rs17281995 (CD86) and rs1051690 (INSR), previously associated with colorectal cancer

In this review, we focus on the genetic variations (single nucleotide polymorphisms, SNPs) known to occur in microRNAs and in their binding sites and the susceptibility to cancers of the gastro-intestinal (GI) tract in humans. Since the sequence complementarity and the thermodynamics of binding play an essential role in the interaction of miRNA with its target mRNA, sequence variations in the miRNA-binding seed regions or in miRNA genes (either within pre-, pri-, or mature miRNA regions) should reinforce, weaken, or disrupt the miRNA-mRNA interaction and affect the expression of mRNA targets. Indirect evidences supporting these hypotheses are reported in the literature, essentially coming from case-control association studies. Several studies have been published on the association between miR-SNPs or SNPs within their binding sites and the risk of oesophageal, gastric, or colorectal cancer. Unfortunately, functional studies are lacking. Besides reviewing the available literature, we present here for the first time two SNPs (rs17281995 in CD86 and rs1051690 in INSR) previously associated with the risk of CRC in a Czech population are also associated with the risk in a Spanish population. Moreover, we show for the first time that both these alleles regulate differentially the amount of a reporter gene (luciferase) in an in vitro assay on HeLa cells. These findings suggest that both these SNPs may have a functional role in regulating the expression of CD-86 and INSR proteins acting at the level of the 3'UTR. More functional studies are needed in order to better understand the role of polymorphic regulatory sequences at the 3'UTR of genes.

Alterations of microRNAs and their targets are associated with acquired resistance of MCF-7 breast cancer cells to cisplatin

Cancer cells that develop resistance to chemotherapeutic agents are a major clinical obstacle in the successful treatment of breast cancer. Acquired cancer chemoresistance is a multifactorial phenomenon, involving various mechanisms and processes. Recent studies suggest that chemoresistance may be linked to drug-induced dysregulation of microRNA function. Furthermore, mounting evidence indicates the existence of similarities between drug-resistant and metastatic cancer cells in terms of resistance to apoptosis and enhanced invasiveness. We studied the role of miRNA alterations in the acquisition of cisplatin-resistant phenotype in MCF-7 human breast adenocarcinoma cells. We identified a total of 103 miRNAs that were overexpressed or underexpressed (46 upregulated and 57 downregulated) in MCF-7 cells resistant to cisplatin. These differentially expressed miRNAs are involved in the control of cell signaling, cell survival, DNA methylation and invasiveness. The most significantly dysregulated miRNAs were miR-146a, miR-10a, miR-221/222, miR-345, miR-200b and miR-200c. Furthermore, we demonstrated that miR-345 and miR-7 target the human multidrug resistance-associated protein 1. These results suggest that dysregulated miRNA expression may underlie the abnormal functioning of critical cellular processes associated with the cisplatin-resistant phenotype.

Association between hsa-mir-146a genotype and tumor age-of-onset in BRCA1/BRCA2-negative familial breast and ovarian cancer patients

An increasing body of evidence points to a possible role of microRNAs (miRNAs) in hereditary cancer syndromes. To evaluate the role of miRNA allelic variants in the susceptibility to familial breast and ovarian cancers in BRCA1/BRCA2-negative patients, we focused our attention on three miRNAs, miR-146a, miR-17 and miR-369, based on their affinity to either BRCA1 or BRCA2 messenger RNA and their localization on chromosome regions commonly deleted in those tumors. The analysis was performed on 101 Italian probands with ascertained familiarity for breast/ovarian cancer and tested negative for both BRCA1 and BRCA2 gene mutations. No allelic variant was detected for hsa-mir-17 and hsa-mir-369, and allelic and genotype frequencies for miR-146a rs2910164 single-nucleotide polymorphism (SNP) were comparable with that of 155 controls from the same population, ruling out a role for genetic variations in these three miRNAs as major determinants in cancer predisposition of BRCA1/BRCA2-negative patients. Instead, our study suggests that mir-146a rs2910164 SNP may impact on the age of cancer onset. In fact, subjects with mir-146a a GC or CC genotypes developed tumors at younger age compared with individuals with the GG genotype Thus, in contrast to a recent report, our data support the hypothesis by Shen and coworkers of an association between the C allele of hsa-mir-146a and early cancer onset and prompt further investigations on the relevance of this polymorphism in early familial breast/ovarian tumor development.

Genetic variations in microRNA-related genes are associated with survival and recurrence in patients with renal cell carcinoma

We took a polygenic approach to evaluate the effects of 41 potentially functional single-nucleotide polymorphisms (SNPs) in microRNAs (miRNAs)-related genes on survival and recurrence among renal cell carcinoma (RCC) patients. During a median follow-up of 21.8 months, among 316 RCC patients, 64 died and 56 developed recurrence. In single-SNP analysis, we identified seven SNPs significantly associated with RCC survival and five SNPs with recurrence. The most significant associations were SNPs in GEMIN4 with the variant alleles of both rs7813 and rs910925 associated with 1.74-fold [95% confidence interval (CI) = 1.15-2.62] increased risk of death, whereas the variant allele of rs3744741 conferred a decreased risk of death [hazard ratio (HR) = 0.39; 95% CI = 0.19-0.77]. Several SNPs belonging to the pre-miRNA and were identified to be significantly associated with RCC recurrence. Haplotypes of DICER and DROSHA were also associated with altered patient survival and recurrence. More importantly, we observed cumulative effects of multiple SNPs on RCC survival. Compared with subjects carrying zero to two unfavorable genotypes, those carrying three to five and six and more unfavorable genotypes had an increased risk of death with a HR of 2.49 (95% CI = 1.24-5.00) and 6.66 (95% CI = 2.49-17.86), respectively, with significant dose-response trend (P for trend<0.001). As the first study of miRNA-related genetic polymorphisms on RCC clinical outcome, our results strongly suggested that miRNA-related SNPs may impact the recurrence and survival in RCC patients. Future investigation in larger populations and functional characterizations are necessary to validate these results.

Correlation between pre-miR-146a C/G polymorphism and gastric cancer risk in Chinese population

AIM: To investigate the association between pre-miR-146a C/G polymorphism and gastric cancer risk.

METHODS: We performed a hospital-based, case-control study using polymerase chain reaction-restriction fragment length polymorphism method in 608 individuals (304 gastric cancer patients and 304 age and sex matched cancer-free controls).

RESULTS: The frequencies of pre-miR-146a C/G genotypes in the case group were significantly different from those in the control groups (P = 0.037). Compared with CC genotype carriers, subjects with the variant genotypes (GC + GG) had a 58% increased risk of gastric cancer (adjusted OR = 1.58, 95% CI: 1.11-2.20, P = 0.009). Moreover, a higher gastric cancer risk was especially evident in younger individuals aged ≤ 58 years, nonsmokers, and males (adjusted OR = 1.76, 95% CI: 1.08-2.87, P = 0.024; adjusted OR = 1.55, 95% CI: 1.06-2.28, P = 0.025; adjusted OR = 1.53, 95% CI: 1.04-2.27, P = 0.033; respectively).

CONCLUSION: Pre-miR-146a C/G polymorphism might be associated with an elevated risk of gastric cancer in Chinese population.

The association between two polymorphisms in pre-miRNAs and breast cancer risk: a meta-analysis

Emerging evidence has shown that miRNAs participate in human carcinogenesis as tumor suppressors or oncogenes. Single nucleotide polymorphism (SNP) which located in the pre-miRNA may affect the processing and then influence the expression of mature miRNA. Previous studies yielded conflicting results as to the association of two common polymorphisms in pre-miRNAs (i.e. hsa-miR-146 rs2910164 and hsa-miR-196a2 rs11614913) with breast cancer. To derive a more precise effect on the association between these polymorphisms and breast cancer risk, we conducted a meta-analysis. Through retrieving PubMed for the period up to May 2010, a total of four studies were identified with 3,007 cases and 3,718 controls for has-miR-146a rs2910164 polymorphism and with 3,287 cases and 4,298 controls for hsa-miR-196a2 rs11614913 polymorphism. We found that individuals carrying CC genotype of has-miR-196a2 rs11614913 polymorphism was associated with an increased breast cancer risk in homozygote comparison (OR = 1.30; 95% CI, 1.01-1.68), and dominant model (OR = 1.11; 95% CI, 1.01-1.23). However, no significant association between has-miR-146a rs2910164 polymorphism and breast cancer risk was observed in all comparison models tested. These findings suggest that has-miR-196a2 rs11614913 polymorphism may play crucial roles in breast cancer development.

The role of microRNA-146a (miR-146a) and its target IL-1R-associated kinase (IRAK1) in psoriatic arthritis susceptibility

MicroRNAs have shown different expression patterns in immune diseases. The present study explores the association of miRNA-146a variant rs2910164 and of two IRAK1 (target of miR-146a) polymorphisms rs3027898 and rs1059703 with psoriasic arthritis (PsA). Twenty-nine PsA and 66 controls were enrolled in the study. To study if the statistical significant differences between patients with PsA and controls are independent to psoriasis, we expanded the study in 49 patients with ankylosing spondylitis (AS). Strong statistical significant difference was observed in IRAK1 rs3027898 polymorphism distribution between patients with PsA and controls (P = 0.003), as between patients with AS and controls (P < 0.001). Marginally significant difference was observed in distribution of IRAK1 rs1059703 genotypes between patients with PsA and controls (P = 0.058), but no difference was observed in miRNA-146a rs2910164 distribution (P = 0.394). This is the first study that addresses IRAK1 rs3027898 polymorphism association with PsA susceptibility, but further studies could help to understand the extent of the proposed association.

Micromarkers: miRNAs in cancer diagnosis and prognosis

Molecular diagnostics in cancer should provide the highest specificity and sensitivity in classification, prognostic stratification and early detection. miRNAs could contribute to hitting the mark, or at least to come nearer, by virtue of their cancer-specific expression and stability. Indeed, different to other RNA classes, miRNAs can be detected and quantified not only in frozen tissues, but also in formalin-fixed paraffin-embedded tissues, as well as serum/plasma samples. Thus, miRNA studies have quickly moved from research on the molecular basis of cancer to areas of clinical application. This review summarizes the potential role of miRNAs as molecular markers for cancer classification, prognostic stratification and drug-response prediction. It also summarizes their potential as circulating markers and cancer-predisposing genes. If we consider that studies on miRNAs in cancer therapy have already given important contributions, miRNAs have an impact in all cancer areas. Whether this will translate into clinical applications is still too early to say. However, in the diagnostic field, miRNAs may already represent an improvement over presently available approaches; for example, their expression profile is effective in the identification of tissue of origin of metastasis. In addition, circulating miRNAs are expected to provide improved specificity and/or sensitivity over presently available markers.

The realm of microRNAs in cancers

MicroRNAs (miRNAs) are members of the non-protein coding RNA family. miRNAs, which can regulate genes on transcriptomic level through either degrading the target messenger RNA (mRNA) or suppressing the protein synthesis, also take part in a number of biological functions that involve development, differentiation, proliferation and apoptosis. The mutations and polymorphisms in the expression levels of miRNA genes or alterations in their epigenetic mechanisms may play their roles in the formation of malignancies. Increasing evidence shows that aberrant miRNA expression profiles are present in a variety of cancers. Therefore, it has been suggested that these profiles could be useful for diagnosis and classification of different tumor types and that these small RNAs might provide significant opportunities for the development of future miRNA-based therapies. In this review, we aimed to look into the realm of miRNAs, which is a recent area of research, appraise their biological activities on molecular level and their probable benefits on clinical practice.

Alterations of MicroRNAs in Solid Cancers and Their Prognostic Value

MicroRNAs (miRNAs) are evolutionarily conserved, naturally abundant, small, regulatory non-coding RNAs that inhibit gene expression at the post-transcriptional level in a sequence-specific manner. Each miRNA represses the protein expression of several coding genes in a manner proportional to the sequence complementarity with the target transcripts. MicroRNAs play key regulatory roles in organismal development and homeostasis. They control fundamental biological processes, such as stem-cell regulation and cellular metabolism, proliferation, differentiation, stress resistance, and apoptosis. Differential miRNA expression is found in malignant tumors in comparison to normal tissue counterparts. This indicates that miRNA deregulation contributes to the initiation and progression of cancer. Currently, miRNA expression signatures are being rigorously investigated in various tumor types, with the aim of developing novel, efficient biomarkers that can improve clinical management of cancer patients. This review discusses deregulated miRNAs in solid tumors, and focuses on their emerging prognostic potential.

Up-regulated microRNA-146a negatively modulate Helicobacter pylori-induced inflammatory response in human gastric epithelial cells

Helicobacter pylori (H. pylori) is a major human pathogenic bacterium in gastric mucosa. However, the regulatory mechanism of H. pylori-induced immune response is not clear. MicroRNAs (miRNAs) have recently emerged as key post-transcriptional regulators of gene expression, and their role in H. pylori infection is just beginning to be explored. Here, we first reported that H. pylori infection up-regulated the expression of miR-146a in gastric epithelial cells as well as in gastric mucosal tissues in NF-κB-dependent manner. In turn, miR-146a may downregulate the expression of target genes, interleukin-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6). Furthermore, miR-146a negatively regulated H. pylori-triggered interleukin (IL)-8, growth-related oncogene (GRO)-α, and macrophage inflammatory protein (MIP) -3α through diminishing NF-κB activity. In conclusion, H. pylori-induced miR-146a plays a potential role in a negative feedback loop to modulate the inflammation by targeting IRAK1 and TRAF6.

Pharmacological studies of the mechanism and function of interleukin-1beta-induced miRNA-146a expression in primary human airway smooth muscle

BACKGROUND

Despite the widespread induction of miR-146a during the innate immune response little is known regarding its biogenesis, function and mechanism. We have therefore examined the role of miR-146a during the interleukin (IL)-1beta-stimulated IL-6 and IL-8 release and proliferation in primary human airway smooth muscle (HASM) cells.

METHODS

HASM cells were isolated from human lung re-section, cultured to a maximum of 3 - 6 passages and then exposed to IL-1beta. miR-146a expression were determined by qRT-PCR, IL-6 and IL-8 release by ELISA and proliferation using bromodeoxyuridine incorporation. The role of NF-kappaB and the MAP kinase pathways was assessed using pharmacological inhibitors of IKK2 (TPCA-1), JNK (SP600125), p38 MAP kinase (SB203580) and MEK-1/2 (PD98059). miR-146a function was determined following transfection of HASM with inhibitors and mimics using Amaxa electroporation.

RESULTS

IL-1beta induced a time-dependent and prolonged 100-fold induction in miR-146a expression, which correlated with release of IL-6 and IL-8. Exposure to IL-1beta had no effect upon HASM proliferation. Pharmacological studies showed that expression of primary miR-146a was regulated at the transcriptional levels by NF-kappaB whilst post-transcriptional processing to mature miR-146a was regulated by MEK-1/2 and JNK-1/2. Functional studies indicated that IL-1beta-induced miR-146a expression does not negatively regulate IL-6 and IL-8 release or basal proliferation. However, inhibition of IL-1beta-induced IL-6 and IL-8 release was observed at the super-maximal intracellular miR-146a levels obtained by transfection with miR-146a mimics and indicates that studies using miRNA mimics can produce false positive results. Mechanistic studies showed that in the presence of super-maximal levels, the action of miR-146a mimics was mediated at a step following IL-6 and IL-8 mRNA transcription and not through down-regulation of IL-1 receptor associated kinase 1 (IRAK-1) and TNF receptor-associated factor 6 (TRAF6) protein expression, two predicted miR-146a targets involved in IL-1beta signalling.

CONCLUSIONS

We have shown that IL-1beta-induced miR-146a expression in HASM and that this was regulated at the transcriptional level by NF-kappaB and at the post-transcriptional level by the MEK-1/2 and JNK-1/2. Unlike previous reports, studies using miRNA inhibitors showed that miR-146a expression did not regulate IL-6 and IL-8 release or proliferation and suggest miR-146a function and mechanism is cell-type dependent.

Genetic variation in microRNA networks: the implications for cancer research

Many studies have highlighted the role that microRNAs have in physiological processes and how their deregulation can lead to cancer. More recently, it has been proposed that the presence of single nucleotide polymorphisms in microRNA genes, their processing machinery and target binding sites affects cancer risk, treatment efficacy and patient prognosis. In reviewing this new field of cancer biology, we describe the methodological approaches of these studies and make recommendations for which strategies will be most informative in the future.

Common genetic polymorphisms in pre-microRNAs were associated with increased risk of dilated cardiomyopathy

BACKGROUND

Common single nucleotide polymorphisms (SNPs) in pre-microRNAs may change their property through altering microRNAs (miRNAs) expression and/or maturation, resulting diverse functional consequences. We conducted a pilot study to test whether SNPs in pre-microRNAs were associated with dilated cardiomyopathy (DCM).

METHODS

Genotypes of 3 SNPs in pre-miRNAs (has-mir-196a2 rs11614913 C/T, hsa-mir-499 rs3746444 A/G, hsa-mir-146a rs2910164 C/G) in 221 DCM patients and 321 control subjects were determined with the use of PCR-restriction fragment length polymorphism (RFLP) assay.

RESULTS

Significantly increased DCM risks were found to be associated with variant allele of has-mir-196a2 rs11614913 C/T (T allele) and hsa-mir-499 rs3746444 A/G (G allele) (P<0.0001, OR=1.730, 95% CI=1.345-2.227, and P<0.0001, OR=1.794, 95% CI=1.350-2.385, respectively). We found that increased DCM risk was statistically significantly associated with these 2 SNPs in a dominant model (P=0.0001 and P<0.0001 for rs11614913 and rs3746444, respectively). No association between DCM risk and hsa-mir-146a rs2910164 C/G was observed (P=0.451, OR=1.102, 95% CI=0.856-1.418).

CONCLUSIONS

Both the has-mir-196a2 rs11614913 C/T and hsa-mir-499 rs3746444 A/G, but not hsa-mir-146a rs2910164 C/G, are associated with a significantly increased risk of DCM, indicating that common genetic polymorphisms in pre-microRNAs are associated with DCM.