MiR-92b inhibits proliferation and invasion of lung cancer by targeting EZH2

Comparative Analysis of microRNAs that Stratify in vitro Mammary stem and Progenitor Activity Reveals Functionality of Human miR-92b-3p

Mammary stem/progenitor cells are fundamental for mammary gland development and function. However, much remains to be elucidated regarding their function in mammals beyond the traditionally studied rodents, human, and to a lesser extent, ruminants. Due to the growing appreciation for microRNAs (miRNAs) as regulators of stem cells and their progenitors, we compared miRNA expression in mammary stem/progenitor cells from mammals with varying mammary stem/progenitor activity in vitro, in order to identify miRNA candidates that regulate stem/progenitor self-renewal and function. Mammosphere-derived epithelial cells (MDECs), which are primary cell lines enriched in mammary stem and progenitor cells, were generated from six mammalian species (i.e., cow, human, pig, horse, dog, and rat) and small RNA sequencing was performed. We identified 9 miRNAs that were significantly differentially expressed in MDEC cultures with a low versus high mammary stem/progenitor activity. miR-92b-3p was selected for functional follow-up studies, as this miRNA is understudied in primary mammary cells but has well-described gene targets that are known to regulate mammary stem/progenitor activity. Altering the expression of miR-92b-3p in MDECs from species with low stem/progenitor activity (human and cow) and those with high stem/progenitor activity (dog and rat) via inhibition and overexpression, respectively, resulted in significantly decreased mammosphere formation of human MDECs, but showed no significant effects in cow, dog, or rat MDECs. This study is the first to perform small RNA sequencing in MDECs from various mammals and highlights that conserved miRNAs can have different functions in mammary stem/progenitor cells across species.

miR-92b-3p Regulates Cell Cycle and Apoptosis by Targeting CDKN1C, Thereby Affecting the Sensitivity of Colorectal Cancer Cells to Chemotherapeutic Drugs

Simple Summary

Multidrug resistance (MDR) limits the effectiveness of colorectal cancer (CRC) treatment and miRNAs play an important role in drug resistance. To search for miRNA targets that may be involved in the CRC MDR phenotype, this study used small RNAomic screens to analyze the expression profiles of miRNAs in CRC HCT8 cell line and its chemoresistant counterpart HCT8/T cell line. It was found that miR-92b-3p was highly expressed in HCT8/T cells and chemotherapeutic drugs could stimulate CRC cells to up-regulate miR-92b-3p expression and conferred cellular resistance to chemotherapeutic drugs. This study revealed a new mechanism of MDR in CRC, elucidating for the first time the direct link between miR-92b-3p/CDKN1C and chemoresistance. In summary, this study suggested that miR-92b-3p could be used as a potential therapeutic target for reversing MDR in chemotherapy and as a candidate biomarker for predicting the efficacy of chemotherapy.

Abstract

Colorectal cancer (CRC) is the third most common malignant tumor in the world and the second leading cause of cancer death. Multidrug resistance (MDR) has become a major obstacle in the clinical treatment of CRC. The clear molecular mechanism of MDR is complex, and miRNAs play an important role in drug resistance. This study used small RNAomic screens to analyze the expression profiles of miRNAs in CRC HCT8 cell line and its chemoresistant counterpart HCT8/T cell line. It was found that miR-92b-3p was highly expressed in HCT8/T cells. Knockdown of miR-92b-3p reversed the resistance of MDR HCT8/T cells to chemotherapeutic drugs in vitro and in vivo. Paclitaxel (PTX, a chemotherapy medication) could stimulate CRC cells to up-regulate miR-92b-3p expression and conferred cellular resistance to chemotherapeutic drugs. In studies on downstream molecules, results suggested that miR-92b-3p directly targeted Cyclin Dependent Kinase Inhibitor 1C (CDKN1C, which encodes a cell cycle inhibitor p57Kip2) to inhibit its expression and regulate the sensitivity of CRC cells to chemotherapeutic drugs. Mechanism study revealed that the miR-92b-3p/CDKN1C axis exerted a regulatory effect on the sensitivity of CRC cells via the regulation of cell cycle and apoptosis. In conclusion, these findings showed that miR-92b-3p/CDKN1C was an important regulator in the development of drug resistance in CRC cells, suggesting its potential application in drug resistance prediction and treatment.

Enforced expression of miR-92b blunts E. coli lipopolysaccharide-mediated inflammatory injury by activating the PI3K/AKT/β-catenin pathway via targeting PTEN

Endometritis is a reproductive disorder characterized by an inflammatory response in the endometrium, which causes significant economic losses to the dairy farming industry. MicroRNAs (miRNAs) are implicated in the inflammatory response and immune regulation following infection by pathogenic bacteria. Recent miRNA microarray analysis showed an altered expression of miR-92b in cows with endometritis. In the present study, we set out to investigate the regulatory mechanism of miR-92b in endometritis. Here, qPCR results first validated that miR-92b was down-regulated during endometritis. And then, bovine endometrial epithelial cells (BEND cells) stimulated by high concentration of lipopolysaccharide (LPS) were employed as an in vitro inflammatory injury model. Our data showed that overexpression of miR-92b significantly suppressed the activation of Toll-like receptor 4 (TLR4) and nuclear factor-κB (NF‐κB) in LPS-stimulated BEND cells, thereby reducing pro-inflammatory cytokines release and inhibiting cell apoptosis. Looking into the molecular mechanisms of regulation of inflammatory injury by miR-92b, we observed that overexpression of miR-92b restrained TLR4/NF‐κB by activating the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT)/β-catenin pathway. Furthermore, the luciferase reporter assay suggested that miR-92b targeted inhibition of phosphatase and tensin homolog (PTEN), an inhibitor of the PI3K/AKT/β-catenin pathway. Importantly, in vivo experiments confirmed that up-regulation of miR-92b attenuated the pathological injury in an experimental murine model of LPS-induced endometritis. Collectively, these findings show that enforced expression of miR-92b alleviates LPS-induced inflammatory injury by activating the PI3K/AKT/β-catenin pathway via targeting PTEN, suggesting a potential application for miR-92b-based therapy to treat endometritis or other inflammatory diseases.