Integrated High-Throughput Bioinformatics (Microarray, RNA-Seq, and RNA Interaction) and qRT-PCR Investigation of BMPR1B Axis as a Potential Diagnostic Biomarker of Isfahan Breast Cancer.

Background: According to the bioinformatics analyses and previous studies, bone morphogenetic protein receptor type 1B (BMPR1B) dysregulation could remarkably affect breast cancer (BC) status as a potential biomarker and tumor suppressor. Therefore, the analysis of the expression level of BMPR1B and other relevant biological factors such as microRNAs, long non-coding RNAs, downstream proteins in the relevant signaling pathways, and finding the accurate biological mechanism of BMPR1B could be helpful for a better understanding of BC pathogenicity and discovering the new treatment methods and drugs. Materials and Methods: R Studio software (4.0.2) was used for microarray data analyses. GSE31448 dataset was downloaded by GEOquery package and analyzed by limma package. STRING and miRWalk online databases and Cytoscape software were used for interaction analyses. Quantitative measurement of BMPR1B expression level was performed by qRT-PCR experiment. Result: Microarray and real-time PCR analysis revealed that BMPR1B has a significant downregulation in the transforming growth factor (TGF)-beta and bone morphogenic protein (BMP) signaling pathways in BC samples. BMPR1B is a potential diagnostic biomarker, regulated by hsa-miR-181a-5p. Also, BMPR1B regulates the function of BMP2, BMP6, SMAD4, SMAD5, and SMAD6 proteins. Discussion: BMPR1B have a significant role in the development of BC by regulating the potential proteins' function, playing the diagnostic biomarker role, and regulation of TGF-beta and BMP signaling pathways. The high amount of BMPR1B protein helps in increasing the survival rate of the patients.

Design of crRNA to Regulate MicroRNAs Related to Metastasis in Colorectal Cancer Using CRISPR-C2c2 (Cas13a) Technique.

Colorectal cancer (CRC) is the third most prevalent cancer with the second-highest mortality rate worldwide. microRNAs (miRNAs) of cancer-derived exosomes have shown promising diagnosis potential. Recent studies have shown the metastatic potential of a specific group of microRNAs called metastasis. Therefore, down-regulation of miRNAs at the transcriptional level can reduce metastasis probability. The aim of this bioinformatics research is targeting of miRNAs precursors using CRISPR-C2c2 (Cas13a) technique. The C2c2 (Cas13a) enzyme structure was downloaded from the RCSB database, the sequence miRNAs and their precursors were collected from miRbase. The crRNAs were designed and evaluated for their specificity by using CRISPR-RT server. The modeling 3D structure of the designed crRNA was performed by RNAComposer server. Finally, HDOCK server was used to perform molecular docking to evaluate docked molecules' energy level and position. The crRNAs designed for miR-1280, miR-206, miR-195, miR- 371a, miR-34a, miR-27a, miR-224, miR-99b, miR-877, miR-495 and miR-384 that showed high structural similarity with the situation observed in normal and appropriate orientation was obtained. Despite high specificity, the correct orientation was not established in the case of crRNAs that designed to target miR-145, miR-378a, miR-199a, miR- 320a and miR-543. The predicted interactions between crRNAs and Cas13a enzyme showed that crRNAs have a strong potential to inhibit metastasis. Therefore, crRNAs may be considered as an effective anticancer agent for further research in drug development.

Transcription Analysis of the THBS2 Gene through Regulation by Potential Noncoding Diagnostic Biomarkers and Oncogenes of Gastric Cancer in the ECM-Receptor Interaction Signaling Pathway: Integrated System Biology and Experimental Investigation.

Background: Gastric cancer (GC) is the second most frequent cause of cancer-related death worldwide and the fourth most common malignancy. Despite significant improvements in patient survival over the past few decades, the prognosis for patients with GC remains dismal because of the high recurrence rate. In this comprehensive system biology and experimental investigation, we aimed to find new novel diagnostic biomarkers of GC through a regulatory RNA interaction network. Methods: Gene expression, coexpression, and survival analyses were performed using microarray and RNAseq datasets (analyzed by RStudio, GEPIA2, and ENCORI). RNA interaction analysis was performed using miRWalk and ENCORI online databases. Gene set enrichment analysis (GSEA) was performed to find related signaling pathways of up- and downregulated genes in the microarray dataset. Gene ontology and pathway enrichment analysis were performed by the enrichr database. Protein interaction analysis was performed by STRING online database. Validation of expression and coexpression analyses was performed using a qRT-PCR experiment. Results: Based on bioinformatics analyses, THBS2 (FC: 7.14, FDR < 0.0001) has a significantly high expression in GC samples. lncRNAs BAIAP2-AS1, TSIX, and LINC01215 have RNA interaction with THBS2. BAIAP2-AS1 (FC: 1.44, FDR: 0.018), TSIX (FC: 1.34, FDR: 0.038), and LINC01215 (FC: 1.19, FDR: 0.046) have significant upregulation in GC samples. THBS2 has a significant role in the regulation of the ECM-receptor signaling pathway. miR-4677-5p has a significant RNA interaction with THBS2. The expression level of THBS2, BAIAP2-AS1, TSIX, and LINC01215 has a nonsignificant negative correlation with the survival rate of GC patients (HR: 0.28, logrank p: 0.28). qRT-PCR experiment validates mentioned bioinformatics expression analyses. BAIAP2-AS1 (AUC: 0.7136, p value: 0.0096), TSIX (AUC: 0.7456, p value: 0.0029), and LINC01215 (AUC: 0.7872, p value: 0.0005) could be acceptable diagnostic biomarkers of GC. Conclusion: BAIAP2-AS1, lncRNA LINC01215, lncRNA TSIX, and miR-4677-5p might modulate the ECM-receptor signaling pathway via regulation of THBS2 expression level, as the high-expressed noncoding RNAs in GC. Furthermore, mentioned lncRNAs could be considered potential diagnostic biomarkers of GC.

Quantitative Expression of SFN, lncRNA CCDC18-AS1, and lncRNA LINC01343 in Human Breast Cancer as the Regulator Biomarkers in a Novel ceRNA Network: Based on Bioinformatics and Experimental Analyses.

Breast cancer (BC) is one of the leading cancers in the world, which has become an increasing serious problem. In this context, reports demonstrate that some long noncoding RNAs (lncRNAs) play significant regulatory roles in breast tumorigenesis and BC progression via various pathways and act as endogenous RNAs. Finding their dysregulation in cancer and evaluating their interaction with other molecules, such as short noncoding RNAs "microRNA (miRNAs)" as well as various genes, are the most important parts in cancer diagnostics. In this study, after performing GSEA and microarray analysis on the GSE71053 dataset, a new ceRNA network of CCDC18-AS1, LINC01343, hsa-miR4462, and SFN in BC was detected by bioinformatics analysis. Therefore, the expression of SFN, CCDC18-AS1, and LINC01343 was quantitatively measured in 24 BC and normal paired tissues using qRT-PCR. CCDC18-AS1, LINC01343, and SFN were expressed higher in BC than in the control (normal paired) tissues based on qRT-PCR data. Furthermore, a significant positive correlation was observed between CCDC18-AS1 and LINC01343 expression in the samples investigated in this study. The investigation of clinicopathological parameters showed that SFN was highly expressed in tumor size of <5 cm and in nonmenopausal ages, while CCDC18-AS1 and LINC01343 indicated a high expression in stages II-III and III of BC, respectively. The overall survival analysis displayed high and low survival in patients with high expression of SFN and CCDC18-AS1, respectively. The ROC curve analysis disclosed that SFN, CCDC18-AS1, and LINC01343 might be suggested as potential biological markers in BC patients. The high expression of CCDC18-AS1, LINC01343, and SFN in BC samples suggests their potential role in BC tumorigenesis and could be considered hallmarks for the diagnosis and prognosis of BC, although this will require further clinical investigations.

NEAT1 can be a diagnostic biomarker in the breast cancer and gastric cancer patients by targeting XIST, hsa-miR-612, and MTRNR2L8: integrated RNA targetome interaction and experimental expression analysis.

BACKGROUND: The most frequent malignancy in women is breast cancer (BC). Gastric cancer (GC) is also the leading cause of cancer-related mortality. Long non-coding RNAs (lncRNAs) are thought to be important neurotic regulators in malignant tumors. In this study, we aimed to evaluate the expression level of NEAT1 and the interaction of this non-coding RNA with correlated microRNAs, lncRNAs, and mRNAs or protein coding genes, experimentally and bioinformatically. METHODS: For the bioinformatics analyses, we performed RNA-RNA and protein-protein interaction analyses, using ENCORI and STRING. The expression analyses were performed by five tools: Microarray data analysis, TCGA data analysis (RNA-seq, R Studio), GEPIA2, ENCORI, and real-time PCR experiment. qRT-PCR experiment was performed on 50 GC samples and 50 BC samples, compared to adjacent control tissue. RESULTS: Based on bioinformatics and experimental analyses, lncRNA NEAT1 have a significant down-regulation in the breast cancer samples with tumor size lower than 2 cm. Also, it has a significant high expression in the gastric cancer patients. Furthermore, NEAT1 have a significant interaction with XIST, hsa-miR-612 and MTRNR2L8. High expression of NEAT1 have a correlation with the lower survival rate of breast cancer samples and higher survival rate of gastric cancer patients. CONCLUSION: This integrated computational and experimental investigation revealed some new aspects of the lncRNA NEAT1 as a potential prognostic biomarker for the breast cancer and gastric cancer samples. Further investigations about NEA1 and correlated mRNAs, lncRNAs, and microRNAs - specially the mentioned RNAs in this study - can lead the researchers to more clear information about the role of NEAT1 in the breast cancer and gastric cancer.

The interaction between MALAT1 target, miR-143-3p, and RALGAPA2 is affected by functional SNP rs3827693 in breast cancer.

A higher expression of MALAT1 has been reported in breast cancer. However, more studies are needed to decipher the mechanisms by which this lncRNA imposes its oncogenic effects. In this study, blood and tissue samples were taken from healthy normal and breast cancer subjects. qPCR was used to analyze the gene expression. HRM-PCR method was carried out to genotype the selected samples. Computational analysis was recruited to find novel targets of MALAT1 and miR-143-3p. The data analyses revealed that MALAT1 was up-regulated in breast cancer and could be a distinctive factor to diagnose cancer. The expression of MALAT1 was inversely correlated with miR-143-3p expression in the studied clinical samples. The down-regulation of miR-143-3p was proven in the clinical tumor samples as compared to the healthy controls. A negative correlation of miR-143-3p with its putative target, RALGAPA2 was observed. A functional SNP rs3827693 located within the 3'UTR region of RALGAPA2 mRNA was validated in this study to associate with breast cancer risk. The rs3827693 allele G significantly decreased the breast cancer incidence and augmented the negative correlation between RALGAPA2 and miR-143-3p, presumably through strengthening the interaction between these two transcripts. This study proposed MALAT1 miR-143-3p and miR-143-3p RALGAPA2 axis in breast cancer, whereby the latter can be altered by the clinically functional SNP rs3827693.

Fluctuating expression of miR-584 in primary and high-grade gastric cancer.

BACKGROUND: Gastric cancer is the fifth most common cancer worldwide. Along with environmental factors, such as Helicobacter pylori (H. pylori) infection, genetic changes play important roles in gastric tumor formations. miR-584 is a less well-characterized microRNA (miRNA), with apparent activity in human cancers. However, miR-584 expression pattern in gastric cancer development has remained unclear. This study aims to analyze the expression of miR-584 in gastric cancer samples and investigates the associations between this miRNA and H. pylori infection and clinical characteristics. METHODS: The expression level of miR-584 was studied in primary gastric cancers versus healthy control gastric mucosa samples using the RT-qPCR method. The clinical data were analyzed statistically in terms of miR-584 expression. In silico studies were employed to study miR-584 more broadly in order to assess its expression and find new potential target genes. RESULTS: Both experimental and in silico studies showed up-regulation of miR-584 in patients with gastric cancer. This up-regulation seems to be induced by H. pylori infection since the infected samples showed increased levels of miR-584 expression. Deeper analyses revealed that miR-584 undergoes a dramatic down-regulation in late stages, invasive and lymph node-metastatic gastric tumors. Bioinformatics studies demonstrated that miR-584 has a substantial role in cancer pathways and has the potential to target STAT1 transcripts. Consistent with the inverse correlation between TCGA RNA-seq data of miR-584 and STAT1 transcripts, the qPCR analysis showed a significant negative correlation between these two RNAs in a set of clinical samples. CONCLUSION: miR-584 undergoes up-regulation in the stage of primary tumor formation; however, becomes down-regulated upon the progression of gastric cancer. These findings suggest the potential of miR-584 as a diagnostic or prognostic biomarker in gastric cancer.

CD44 Gene rs8193 C Allele Is Significantly Enriched in Gastric Cancer Patients.

OBJECTIVE: Gastric cancer is a multifactorial disease. In addition to environmental factors, many genes are involved in this malignancy. One of the genes associated with gastric cancer is CD44 gene and its polymorphisms. CD44 gene plays role in regulating cell survival, growth and mobility. The single nucleotide polymorphism (SNP) rs8193, located in the CD44 gene, has not been studied in gastric cancer patients of the Iranian population. The present study aims to study this polymorphism in 86 gastric cancer patients and 96 healthy individuals. MATERIALS AND METHODS: In this cross-sectional case-control study, rs8193 polymorphism was genotyped by allele specific primer polymerase chain reaction (ASP-PCR) technique. The obtained data were statistically analyzed. To find the potential mechanism of action, rs8193 was bioinformatically investigated. RESULTS: rs8193 C allele played a risk factor role for gastric cancer. Patients carrying this allele were more susceptible to have gastric cancer, with lymph node spread. On the other hand, rs8193 T allele, a protective factor, was associated with a higher chance of accumulation in the lower stages of cancer. C allele might impose its effect via destabilizing CD44 and miR-570 interaction. CONCLUSION: rs8193 is statistically associated with the risk of malignancy, lymph node spread and stage of gastric cancer in Iranian population.

Evaluation of The Expression Levels of Three Long Non-Coding RNAs in Multiple Sclerosis.

OBJECTIVE: Multiple sclerosis (MS) is a chronic disorder involving both inflammatory and neurodegenerative responses. Long non-coding RNAs (lncRNAs) have been had an emerging role as the biomarkers of different disorders, including autoimmune diseases. Previous studies have shown that NR_003531.3 (MEG3a), AC000061.1_201, and AC007182.6 play a role in the pathogenesis of human autoimmune diseases. However, the potential significance of these lncRNAs, as the diagnostic biomarkers of MS, has not been studied yet. We aimed to quantitatively evaluate the expression levels of NR_003531.3, AC000061.1_201, and AC007182.6 in peripheral blood samples of MS patients in comparison with healthy controls. MATERIALS AND METHODS: In this case-control study, the blood samples from 20 MS patients and 10 healthy controls were collected. Total RNA was extracted, and the expression levels of three selected lncRNAs were quantitatively measured using the quantitative real time-polymerase chain reaction (qRT-PCR) method. RESULTS: We detected a significant down-regulation in the expression of NR_003531.3 in MS patients, while no marked changes were observed in the expression of AC000061.1_201 and AC007182.6 in patients compared with controls. Based on the receiver operating characteristic (ROC) curve analysis, NR_003531.3 could discriminate MS patients from healthy subjects effectively. Regarding the prognosis of MS patients, NR_003531.3 is significantly and inversely correlated with the expanded disability status scale (EDSS). CONCLUSION: The potential role of NR_003531.3 lncRNA as a diagnostic biomarker to distinguish MS patients is proposed. Prognostically, NR_003531.3 correlates with lower disability rates in MS patients.

Evaluation of the Expression Level and Hormone Receptor Association of miR-126 in Breast Cancer.

Breast cancer is a major cause of cancer-related death in women worldwide. miRNAs are new players of breast tumorigenesis, used as diagnostic and prognostic biomarkers. Among various miRNAs, miR-126 has been proposed to have a tumor suppressive role in HER2 positive cancer. However, to have a better understanding of its role, further validation is required. The aim of this study was evaluating miR-126 expression level in breast cancer tissues and investigating its potential association with HER2, estrogen and progesterone receptors. miR-126 expression level was measured in 108 specimens including 78 malignant and 30 normal samples using RT-qPCR. The outcome was statistically analyzed. In silico studies were performed to find the potential mechanism of action, through which miR-126 imposes its function. Down-regulation of miR-126 was observed in tumor samples, as compared to the matched normal tissues. Down-regulation of miR-126 was also associated significantly with the absence of estrogen receptor in malignant samples. No association between miR-126 expression and HER2 status was observed. Our in silico analyses showed the possible role of Crk, PI3K and Ras proto-oncogenes in breast cancer tumorigenesis. miR-126 is significantly down-regulated in breast cancer tissues. Statistically, it showed no correlation with HER2 positivity. However, the association between lower miR-126 and estrogen receptor negativity was observed.

TP53 rs1625895 is Related to Breast Cancer Incidence and Early Death in Iranian Population.

Breast cancer as the second most common cancer worldwide tend to be experienced by Iranian women 10 years earlier with a peak incidence at the premenopausal stage. Genetic mutations of TP53 tumor suppressor gene has been shown to be related to early onset of breast cancer. It has been shown already that rs1625895 polymorphic site is related to glioma as well as lung cancer. In this study, we have investigated the role of rs1625895 polymorphism in breast cancer incidence in Iranian women. DNA extraction of 86 breast cancer patients and 96 control individuals have been used for allele-specific primer-PCR and genotyping of allele A and allele G of the TP53 rs1625895. Genotypes frequencies have been shown that GG homozygosis as the most frequent genotype is a significant association with increased risk of breast cancer development in Iranian women (odds ratio = 6, p = 0.002). On the other hand and in comparison to allele G, allele A could cause early death of breast cancer patients by threefolds significantly (p = 0.011). As a conclusion, we show that allele A is the minor allele in both breast cancer patients and also control individuals and major allele G, is related to the increased risk of breast cancer development in Iranian women.

miR-581-Related Single Nucleotide Polymorphism, rs2641726, Located in MUC4 Gene, is Associated with Gastric Cancer Incidence.

MUC4 is aberrantly expressed in several carcinomas including breast, colon, ovarian, lung, prostate, stomach and pancreatic cancers. MUC4 can regulate cell apoptosis negatively and facilitate stomach tumorigenesis. In this research, we aimed to evaluate the possible association between rs2641726 (C > A) polymorphism of MUC4 and gastric cancer risk in the Iranian population. In this case-control study, we collected blood samples from 168 gastric cancer patients and 66 healthy subjects. Allele-specific primer polymerase chain reaction method was applied to genotype rs2641726 in the obtained DNA samples. This study demonstrated that rs2641726 C allele was significantly associated with the incidence of gastric cancer, odds ratio = 3.382, 95% confidence interval: 1.840-6.217 (P < 0.001). Furthermore, the distribution of this risk allele was highly enriched in the samples with stage III. In silico studies revealed that the C allele of rs2641726, located within MUC4 3'UTR, is potential to attenuate the interaction between miR-581 and MUC4 mRNA. This disturbing effect, which might result in higher expression of MUC4 oncoprotein, was proposed for the mechanism of action of the rs2641726 risk allele. rs2641726 C allele is significantly enriched in gastric cancer specimens. The attenuating effect of this allele on miR-581 and MUC4 interaction might be a potential mechanism of action by which C allele imposes its oncogenic impact.

miR-146a is deregulated in gastric cancer.

BACKGROUND: Gastric cancer is one of the most significant reasons for cancer-related death. miR-146a is one of the dysregulated factors associated with gastric tumorigenesis. However, deregulation of this microRNA (miRNA) has become controversial. Moreover, the inflammation-mediating role of this miRNA implies that miR-146a might be dysregulated by gastric cancer-related pathogens, such as Helicobacter pylori. However, the dysregulation of miR-146a in H. pylori-infected gastric tumors has not been widely studied. OBJECTIVES: We aimed to analyze the expression level of miR-146a in gastric cancer tissues and then to assess any potential association between miR-146a and H. pylori infection and other clinical characteristics. MATERIALS AND METHODS: miR-146a expression level was quantitatively studied by reverse transcription quantitative polymerase chain reaction, in 144 fresh tissues including 44 normal and 100 gastric cancer samples. RESULTS: A dramatic overexpression of miR-146a was observed in primary gastric tumors. miR-146a showed lower expression in progressed tumors with greater stages and lymph node metastasis. CONCLUSION: miR-146a is highly expressed in primary gastric tumor independent of H. pylori infection. It is highly expressed in the lower stages and lymph node-negative tumors. It might suggest the importance of upregulation and downregulation of this miRNA in the initiating/promoting and progressive steps of gastric tumorigenesis, respectively.

The association between rs1972820 and the risk of breast cancer in Isfahan population.

CONTEXT: A number of single nucleotide polymorphisms (SNPs) in ERBB4 gene have been linked to increase the risk of breast cancer. However, no study has been dedicated to analyze the significance of microRNA-related SNP rs1972820, located in ERBB4 3'-untranslated region (UTR), in breast tumors. AIMS: Here, we investigated the frequency and association between rs1972820 and breast cancer. SUBJECTS AND METHODS: The rs1972820 genotypes in 182 samples were collected from 96 healthy people, and 86 breast cancer patients were determined using tetra-primer amplification refractory mutation system-polymerase chain reaction. The frequency of genotypes was analyzed to find the association between rs1972820 and breast cancer risk. STATISTICAL ANALYSIS USED: Conditional logistic regression, odds ratios (ORs), the associated 95% confidence intervals (CIs), and Armitage's test were used in this study. RESULTS: In silico analysis suggested that rs1972820 located in the 3'UTR of ERBB4 gene affects the binding affinity of miR-3144-3p a potential oncomiRNA. Statistical analysis showed a significant association between SNP rs1972820 G allele and reduced breast cancer risk, odds ratio = 0.443 (95% CI: 0.196-0.998). CONCLUSIONS: rs1972820 SNP allele is significantly associated with the reduced risk of breast cancer and could be considered as a potential marker for breast cancer predisposition in population of Isfahan.

ESR1 single nucleotide polymorphism rs1062577 (c.*3804T>A) alters the susceptibility of breast cancer risk in Iranian population.

OBJECTIVES: Albeit single nucleotide polymorphisms related to ESR1 gene have been studied, only a number of them have been reported to be associated with breast cancer risk. rs1062577 is one of the most recent microRNA-related ESR1 SNPs; however, no study has been conducted to investigate the significance this polymorphism in Iranian population. In this study, we aimed to investigate the frequency and also the association between rs1062577 and breast cancer. MATERIALS AND METHODS: rs1062577 position was genotyped by Tetra-primer ARMS-PCR in totally 182 blood specimens obtained from breast cancer patients (n=86), and healthy blood donors (n=96). The distribution of different genotypes was statistically analyzed in terms of the potential association between rs1062577 different alleles, breast cancer risk and clinicopathological criteria of breast cancer patients. RESULTS: The statistical analyses confidently indicated that rs1062577 A allele is associated with the increased breast cancer risk in both univariate and multivariate regression models (Odds Ratio=8.403 and 32.602 respectively). rs1062577 T allele was statistically associated with stage I of breast cancer patients (p-value=0.025). In silico studies implied that rs1062577 A allele can alter the binding capacity of ESR1 mRNA and miRNAs via either breakage or formation of hydrogen bonds. CONCLUSION: rs1062577 A allele is significantly and dramatically associated with the elevated risk and greater stages of breast cancer.

Upregulation of miR-222 in both Helicobacter pylori- infected and noninfected gastric cancer patients.

Despite of promising improvements in treatment of gastric cancer, the mortality rate of this malignancy remains high. Chronic infection by Helicobacter pylori, interfering with intracellular signalling pathways, is the main risk factor for gastric cancer. Some evidence suggests that microRNAs (miRNA), the small noncoding RNA molecules, can play role as oncogenes or tumour suppressors in the cells. MiR-222 is one of the remarkable miRNAs undergoing upregulation in gastric cancer. However, the association between miR-222 upregulation and H. pylori infection in gastric cancer tissues remains unclear. The aim of this study was to analyse the expression level of miR-222 in gastric cancer tissues, evaluating the relationship between miR-222 expression level and H. pylori infection and also finding novel miR-222 targets based on in silico investigations. MiR-222 expression level in 200 patients including 112 H. pylori positive and 88 H. pylori negative was relatively measured using RT-qPCR and compared with 88 healthy samples. In silico enrichment analysis of miR-222 targets was performed by DAVID database to evaluate the possible role(s) of miR-222 in gastric tumourigenesis. We observed upregulated level of miR-222 in gastric cancer tissues compared with normal samples (P<0.05). However, no significant difference between miR-222 expression in H. pylori-positive and H. pylori-negative cases was observed. Our in silico analyses showed the possible role of p53, p27, PTEN and Elongin B in gastric cancer tumourigenesis. MiR-222 functions as an onco-miRNA and its overexpression can be involved in pathogenesis of gastric cancer, independent of H. pylori infection.

Tumor-promoting function of single nucleotide polymorphism rs1836724 (C3388T) alters multiple potential legitimate microRNA binding sites at the 3'-untranslated region of ErbB4 in breast cancer.

ErbB4 can act as either a tumor-suppressor gene or an oncogene in breast cancer. Multiple genetic factors including single nucleotide polymorphisms (SNPs) affect gene expression patterns. Multiple 3'-untranslated region (3'-UTR) SNPs reside within the target binding site of microRNAs, which can strengthen or weaken binding to target genes. The present study aimed to predict potential 3'­UTR variants of ErbB4 that alter the target binding site of microRNAs (miRNAs) and to clarify the association of the potential variant with the risk of developing breast cancer. In silico prediction was performed to identify potential functional SNPs within miRNA target binding sites in the 3'­UTR of ErbB4. Thus, 146 patients and controls were genotyped using restriction fragment length polymorphism-polymerase chain reaction. In addition to the Cochran-Armitage test for trend, allele and genotype frequency differences were determined to investigate the association between rs1836724 and the susceptibility to breast cancer. Bioinformatics analysis identified rs1836724 to be a polymorphism in the seed region of four miRNA binding sites (hsa-miR335-5p, hsa-miR-28-5p, has­miR­708­5p and has­miR­665), which may participate in the development of breast cancer. Logistic regression data indicated that the T allele of the polymorphism [OR (95% CI)=1.72 (1.056­2.808), P=0.029] is associated with the risk of breast cancer. Using bioinformatics tools, a correlation was indicated between the presence of the T allele and a reduction in ErbB4 RNA silencing based on miRNA interaction. Furthermore, case subgroup data analysis revealed an association between the C/T genotype and an ER positive phenotype [OR (95% CI)=6.00 (1.082­33.274), P=0.028] compared with the T/T genotype. ErbB4 and estrogen receptor 1 (ESR1) are regulated by identical miRNAs thus there may be a competition for binding sites. Due to this pattern, if the interaction between miRNAs with one gene is reduced, it may be consistent with the increase in interaction with another one. Therefore, more interaction with rs1836724 C variant within ErbB4 may be associated with higher expression of ESR1 (ER­positive phenotype). miRNAs interact with ErbB4 mRNA more frequently when it carries C allele at the rs1836724 position compared with the T carriers. Therefore, the identical miRNA interacts with ESR1 less frequently when ErbB4 mRNA has a C allele. Therefore, ESR1 expression may be higher when ErbB4 mRNA has a C allele.