Comprehensive identification of microRNA arm selection preference in lung cancer: miR-324-5p and -3p serve oncogenic functions in lung cancer.

MicroRNA (miRNA/miR) dysfunction is a hallmark of lung cancer, and results in the dysregulation of tumor suppressors and oncogenes during lung cancer progression. Selection of the 5p and 3p arms of miRNA is a mechanism that improves the modulation of miRNA biological functions and complicates the regulatory network in human types of cancer. However, the involvement of arm selection preference of miRNA in lung cancer remains unclear. In the present study, changes in miRNA arm selection preference were comprehensively identified in lung cancer and corresponding adjacent normal tissues by analyzing The Cancer Genome Atlas. Arm selection was revealed to be consistent in the majority of miRNAs in lung cancer. Only a few miRNAs had significantly altered arm selection preference in lung cancer. Among these, the biological functions of the individual arms of miR-324 were investigated further. The data revealed that miR-324-5p and -3p were significantly overexpressed in lung cancer cells. Ectopic expression of miR-324-5p significantly promoted cell proliferation and invasion in lung cancer cells, while miR-324-3p overexpression significantly increased cell proliferation but did not alter the invasion of lung cancer cells. In conclusion, the arm selection preference of miRNA may be an additional mechanism through which biological functions are modulated. The results of the present study provide a novel insight into the underlying mechanisms of lung cancer and may direct research into future therapies.

MicroRNA-324 in Human Cancer: miR-324-5p and miR-324-3p Have Distinct Biological Functions in Human Cancer.

MicroRNAs (miRNAs) are small non-coding RNAs that have crucial regulatory functions in carcinogenesis. miR-324-5p and miR-324-3p are generated from the same hairpin RNA structure, however, both are diverse in their direct target genes and expression levels. We report that expression of miR-324-5p and -3p was frequently observed to be either up-regulated or down-regulated, and the selection preference of miR-324 for 5p and 3p arms significantly varied in various types or human cancer. Overexpression of miR-324-5p or -3p suppressed growth and invasion of breast cancer cells. Overexpression of miR-324-5p reduced the growth and invasive abilities of colorectal cancer cells, whereas miR-324-3p suppressed colorectal cancer cell invasion but did not influence cell growth. We conclude that miR-324-5p and miR-324-3p might have distinct biological functions, further complicating the regulatory network in human cancer. Therefore, the arm selection preference of miR-324 may be a method for modulating its function.

Arm Selection Preference of MicroRNA-193a Varies in Breast Cancer.

MicroRNAs (miRNAs) are short noncoding RNAs derived from the 3' and 5' ends of the same precursor. However, the biological function and mechanism of miRNA arm expression preference remain unclear in breast cancer. We found significant decreases in the expression levels of miR-193a-5p but no significant differences in those of miR-193a-3p in breast cancer. MiR-193a-3p suppressed breast cancer cell growth and migration and invasion abilities, whereas miR-193a-5p suppressed cell growth but did not influence cell motility. Furthermore, NLN and CCND1, PLAU, and SEPN1 were directly targeted by miR-193a-5p and miR-193a-3p, respectively, in breast cancer cells. The endogenous levels of miR-193a-5p and miR-193a-3p were significantly increased by transfecting breast cancer cells with the 3'UTR of their direct targets. Comprehensive analysis of The Cancer Genome Atlas database revealed significant differences in the arm expression preferences of several miRNAs between breast cancer and adjacent normal tissues. Our results collectively indicate that the arm expression preference phenomenon may be attributable to the target gene amount during breast cancer progression. The miRNA arm expression preference may be a means of modulating miRNA function, further complicating the mRNA regulatory network. Our findings provide a new insight into miRNA regulation and an application for breast cancer therapy.

Emerging role of microRNAs in modulating endothelin-1 expression in gastric cancer.

Endothelin-1 (ET-1) is a small 21-amino acid peptide that is known to exert diverse biological effects on a wide variety of tissues and cell types through its own receptors. The ET-1-ETRA axis is frequently dysfunctional in numerous types of carcinomas, and contributes to the promotion of cell growth and migration. microRNAs (miRNAs) are small non-coding RNAs that play a critical role in carcinogenesis through mRNA degradation or the translational inhibition of cancer-associated protein-coding genes. However, the role of ET-1 and the relationship between ET-1 and miRNAs in gastric cancer remain unknown. Results of the analysis of the database of The Cancer Genome Atlas (TCGA) revealed that ET-1 is significantly overexpressed in gastric cancer cells when compared with its expression in adjacent normal cells. Exogenous ET-1 significantly enhanced gastric cancer cell proliferation, implying that ET-1 plays an oncogenic role in gastric cancer carcinogenesis. Using a luciferase reporter assay we showed that 18 miRNA candidates had a significant silencing effect on ET-1 expression by up to 20% in HEK293T cells. Among them, 5 miRNAs (miR-1, miR-101, miR-125A, miR-144 and let-7c) were shown to be involved in ET-1 silencing through post-transcriptional modulation in gastric cancer. Our data also revealed that DNA hypermethylation contributes to the silenced miR-1 expression in gastric cancer cells. The ectopic expression of miR-1 significantly inhibited AGS cell proliferation by suppressing ET-1 expression. Overall, our study revealed that ET-1 overexpression may be due to DNA hypermethylation resulting in the silencing of miR-1 expression in gastric cancer cells. In addition, we identified several miRNAs as potential modulators for ET-1 in gastric cancer, which may be used as targets for gastric cancer therapy.

Co-modulated behavior and effects of differentially expressed miRNA in colorectal cancer.

BACKGROUND: MicroRNAs (miRNAs) are short noncoding RNAs (approximately 22 nucleotides in length) that play important roles in colorectal cancer (CRC) progression through silencing gene expression. Numerous dysregulated miRNAs simultaneously participate in the process of colon cancer development. However, the detailed mechanisms and biological functions of co-expressed miRNA in colorectal carcinogenesis have yet to be fully elucidated. RESULTS: The objective of this study was to identify the dysfunctional miRNAs and their target mRNAs using a wet-lab experimental and dry-lab bioinformatics approach. The differentially expressed miRNA candidates were identified from 2 miRNA profiles, and were confirmed in CRC clinical samples using reported target genes of dysfunctional miRNAs to perform functional pathway enrichment analysis. Potential target gene candidates were predicted by an in silico search, and their expression levels between normal and colorectal tumor tissues were further analyzed using real-time polymerase chain reaction (RT-PCR). CONCLUSION: Fifteen dysfunctional miRNAs were engaged in metastasis-associated pathways through comodulating 7 target genes, which were identified by using a multi-step approach. The roles of these candidate genes are worth further exploration in the progression of colon cancer, and could potentially be targets in future therapy.

Comprehensive analysis of microRNAs in breast cancer.

BACKGROUND: MicroRNAs (miRNAs) are short noncoding RNAs (approximately 22 nucleotides in length) that play important roles in breast cancer progression by downregulating gene expression. The detailed mechanisms and biological functions of miRNA molecules in breast carcinogenesis have yet to be fully elucidated. This study used bioinformatics and experimental approaches to conduct detailed analysis of the dysregulated miRNAs, arm selection preferences, 3' end modifications, and position shifts in isoforms of miRNAs (isomiRs) in breast cancer. METHODS: Next-generation sequencing (NGS) data on breast cancer was obtained from the NCBI Sequence Read Archive (SRA). The miRNA expression profiles and isomiRs in normal breast and breast tumor tissues were determined by mapping the clean reads back to human miRNAs. Differences in miRNA expression and pre-miRNA 5p/3p arm usage between normal and breast tumor tissues were further investigated using stem-loop reverse transcription and real-time polymerase chain reaction. RESULTS: The analysis identified and confirmed the aberrant expression of 22 miRNAs in breast cancer. Results from pathway enrichment analysis further indicated that the aberrantly expressed miRNAs play important roles in breast carcinogenesis by regulating the mitogen-activated protein kinase (MAPK) signaling pathway. Data also indicated that the position shifts in isomiRs and 3' end modifications were consistent in breast tumor and adjacent normal tissues, and that 5p/3p arm usage of some miRNAs displayed significant preferences in breast cancer. CONCLUSIONS: Expression pattern and arm selection of miRNAs are significantly varied in breast cancers through analyzing NGS data and experimental approach. These miRNA candidates have high potential to play critical roles in the progression of breast cancer and could potentially provide as targets for future therapy.