MicroRNAs are emerging as important regulators of cancer‐related processes. Our studies show that microRNA‐9 (miR‐9) is downregulated in human ovarian cancer relative to normal ovary, and overexpression of miR‐9 suppresses cell growth in vitro. Furthermore, the 3′‐UTR of NF‐κB1 mRNA is found to be regulated directly by miR‐9, demonstrating that NF‐κB1 is a functionally important target of miR‐9 in ovarian cancer cells. When miR‐9 is overexpressed in ovarian cancer cells, the mRNA and protein levels of NF‐κB1 are both suppressed, whereas inhibition of miR‐9 results in an increase in the NF‐κB1 expression level. Ovarian cancer tissues display significantly low expression of miR‐9 and a high level of NF‐κB1 compared with normal tissues, indicating that regulation of NF‐κB1 by miR‐9 is an important mechanism for miR‐9 to inhibit ovarian cancer proliferation.

MicroRNAs are a class of small noncoding RNAs that function as key regulators of gene expression at the post-transcriptional level. In this study, we demonstrate that miR-214 is frequently down-regulated in cervical cancer, and its expression reduces the proliferation, migration, and invasiveness of cervical cancer cells, whereas inhibiting its expression results in enhanced proliferation, migration, and invasion. miR-214 binds to the 3′-UTR of UDP-N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase 7 (GALNT7), thereby repressing GALNT7 expression. Furthermore, we are the first to show, using quantitative real-time PCR, that GALNT7 is frequently up-regulated in cervical cancer. The knockdown of GALNT7 markedly inhibits cervical cancer cell proliferation, migration, and invasion, whereas ectopic expression of GALNT7 significantly enhances these properties, indicating that GALNT7 might function as an oncogene in cervical cancer. The restoration of GALNT7 expression can counteract the effect of miR-214 on cell proliferation, migration, and invasiveness of cervical cancer cells. Together, these results indicate that miR-214 is a new regulator of GALNT7, and both miR-214 and GALNT7 play important roles in the pathogenesis of cervical cancer.

MicroRNAs are short regulatory RNAs that negatively modulate gene expression at the post-transcriptional level, and are deeply involved in the pathogenesis of several types of cancers. To investigate whether specific miRNAs and their target genes participate in the molecular pathogenesis of laryngeal carcinoma, oligonucleotide microarrays were used to assess the differential expression profiles of microRNAs and mRNAs in laryngeal carcinoma tissues compared with normal tissues. The oncogenic miRNA, microRNA-21 (miR-21), was found to be upregulated in laryngeal carcinoma tissues. Knockdown of miR-21 by specific antisense oligonucleotides inhibited the proliferation potential of HEp-2 cells, whereas overexpression of miR-21 elevated growth activity of the cells, as detected by the colony formation assay. The cell number reduction caused by miR-21 inhibition was due to the loss of control of the G1-S phase transition, instead of a noticeable increase in apoptosis. Subsequently, a new target gene of miR-21, BTG2, was found to be downregulated in laryngeal carcinoma tissues. BTG2 is known to act as a pan-cell cycle regulator and tumor suppressor. These findings indicate that aberrant expression of miR-21 may contribute to the malignant phenotype of laryngeal carcinoma by maintaining a low level of BTG2. The identification of the oncogenic miR-21 and its target gene, BTG2, in laryngeal carcinoma is potentially valuable for cancer diagnosis and therapy.

Background: MicroRNAs (miRNAs) are a new class of naturally occurring, small, non-coding RNAs that regulate protein-coding mRNAs by causing mRNA degradation or repressing translation. The roles of miRNAs in lineage determination and proliferation, as well as the localization of several miRNA genes at sites of translocation breakpoints or deletions, have led to speculation that miRNAs could be important factors in the development or maintenance of the neoplastic state. Results: We showed that miR-9 was downregulated in human gastric adenocarcinoma. Overexpression of miR-9 suppressed the growth of human gastric adenocarcinoma cell line MGC803 cell as well as xenograft tumors derived from them in SCID mice. Bioinformatics analysis indicated a putative miR-9 binding site in the 3'-untranslated region (3'UTR) of the tumor-related gene NF-κB1 mRNA. In an EGFP reporter system, overexpression of miR-9 downregulated EGFP intensity, and mutation of the miR-9 binding site abolished the effect of miR-9 on EGFP intensity. Furthermore, both the NF-κB1 mRNA and protein levels were affected by miR-9. Finally, knockdown of NF-κB1 inhibited MGC803 cell growth in a time-dependent manner, while ectopic expression of NF-κB1 could rescue MGC803 cell from growth inhibition caused by miR-9. Conclusion: These findings indicate that miR-9 targets NF-κB1 and regulates gastric cancer cell growth, suggesting that miR-9 shows tumor suppressive activity in human gastric cancer pathogenesis.

MicroRNAs (miRNAs) are considered to be regulators of various biological processes in cancers, including the epithelial to mesenchymal transition (EMT), which is a key factor in cancer metastasis. In this study, we aimed to clarify the potential roles of miR-490-3p in hepatocellular carcinoma (HCC) cells. Using real-time quantitative RT-PCR, we discovered that miR-490-3p was up-regulated in HCC tissues and cells compared with the adjacent non-tumor tissues and normal cells. We also found that overexpression of miR-490-3p led to an increase in cell proliferation, migration, and invasion abilities and that it contributed to EMT. The inhibition of miR-490-3p had the opposite effect on the cells. We identified ERGIC3 (endoplasmic reticulum-Golgi intermediate compartment protein 3) as a direct target gene for miR-490-3p. Unlike most miRNA-mRNA interactions, miR-490-3p increased ERGIC3 mRNA and protein levels as well as the intensity of expression of the EGFP reporter gene controlled by the 3′-UTR of ERGIC3 mRNA. The up-regulation by miR-490-3p also required the participation of Ago2. The inhibition of miR-490-3p reduced the expression of ERGIC3. Overexpression of ERGIC3 led to the same effect on HCC cells as miR-490-3p overexpression, including EMT. Importantly, silencing ERGIC3 reversed the cellular responses mediated by miR-490-3p overexpression. In conclusion, our study indicated for the first time that miR-490-3p functioned like an oncogenic miRNA in HCC cells and that the inhibition of miR-490-3p might provide an potential treatment approach for HCC patients.