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Background: MicroRNA-490-3p (miR-490-3p) plays a role in the pathogeneses of a variety of cardiovascular diseases. Bioinformatic analysis showed that miR-490-3p was downregulated in the myocardial tissues of mice with myocardial infarction (MI). Nevertheless, the functions and mechanisms of miR-490-3p in MI remain unclear., Methods: This study used an in-vitro model to investigate the role of miR-490-3p in MI. Human cardiac myocytes (HCMs) were cultured in a hypoxic environment. 3-(4,5)-Dimethylthiahiazo (-zy1)- 3,5-di-phenytetrazoliumromide (MTT) assay and flow cytometry were used to detect cell viability and apoptosis. The expression levels of forkhead box O1 (FOXO1) and miR-490-3p were detected by quantitative real-time PCR and Western blot. The levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), lactate dehydrogenase (LDH), cardiac troponin I (cTnI), and creatine kinase MB (CK-MB) were detected by enzyme-linked immunosorbent assay (ELISA). The targeted relationship between miR-490-3p and FOXO1 3'UTR was determined by a dual-luciferase reporter gene assay., Results: miR-490-3p was significantly down-regulated in hypoxia-induced HCM cells, while FOXO1 was markedly up-regulated. miR-490-3p overexpression inhibited HCM cell inflammatory responses and injury after hypoxia treatment. FOXO1 was validated to be a direct target of miR- 490-3p, and its overexpression weakened the effects of miR-490-3p on cell viability, apoptosis, as well as inflammatory responses., Conclusion: miR-490-3p alleviates cardiomyocyte injury via targeting FOXO1 in MI., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Chemotherapy is one of the most common treatments used for hepatocellular carcinoma (HCC), which effectively improves outcome and reduces tumor recurrence. However, the drug resistance mechanisms involved in chemotherapy, which is the predominant challenge in HCC treatment, remain to be fully elucidated. Therefore, there is an urgent requirement for the identification of novel therapeutic strategies or drugs. MicroRNAs (miRs) have become an area of interest, and in the present study, the effects of miR‑133a and miR‑326 on HepG2 cells, and their function on B‑cell lymphoma‑extra large (Bcl‑xl) in HepG2 cells were investigated. Using computational programs, Bcl‑xl was predicted as the common target gene of miR‑133a and miR‑326. A dual‑luciferase reporter assay was used to verify the target genes of miRs. The mRNA and protein levels of Bcl‑xl were observed to be downregulated following transfection with miR‑133a or miR‑326 mimics. Combining miR‑133a or miR‑326 with 5‑fluorouracil (5‑FU) or cisplatin (DDP) resulted in increased cell death. The results of the present study indicated that miR‑133a, miR‑326 and Bcl‑xl acted protectively against the apoptosis, induced by 5‑FU or DDP, in HepG2 cells. This suggested the potential use of miRs either as ancillary anti‑cancer drugs or as anti‑cancer drugs themselves.

Recent studies have shown that a class of small, functional RNAs, named microRNAs, may regulate multidrug resistance-associated protein 1 (ABCC1). Since ABCC1 is an important efflux transporter responsible for cellular drug disposition, the discovery of microRNAs (miRNA) brings an idea that there may be some other unknown multidrug resistance (MDR) mechanisms exist. Using computational programs, we predicted that the 3'untranslated region (3'UTR) of ABCC1 contains a potential miRNA binding site for miR-133a and also two other for miR-326. These binding sites were confirmed by luciferase reporter assay. ABCC1 mRNA degradation was accelerated dramatically in cells transfected with miR-133a or miR-326 mimics using qRT-PCR, Furthermore, western blot analysis indicated that ABCC1 protein expression was significantly down-regulated in hepatocellular carcinoma cells line HepG2 after transfection with miR-133a or miR-326 mimics, suggesting the involvement of mRNA degradation and protein expression mechanism. The effects of the two miRNAs on adriamycin (ADM) sensitivity to HepG2 cells were determined by MTT assay. Compared with mock transfection, miR-133a or miR-326 mimics transfection sensitized these cells to ADM. These findings for the first time demonstrated that the involvement of miR-133a and miR-326 in MDR is mediated by ABCC1 in hepatocellular carcinoma cell line HepG2 and suggested that miR-133a and miR-326 may be efficient agents for preventing and reversing ADM resistance in cancer cells.

Let-7 microRNA is expressed in lower lever in a variety of human tumors and is involved in tumorigenesis. This study investigated the inhibitory effect of the let-7g microRNA on the expression of the HMGA2 gene in the fluorouracil (5-Fu)-resistant human hepatoma cell line Bel-7402/5-Fu, and the effect of let-7 g microRNA on drug sensitization in Bel-7402/5-Fu cells. Let-7 g microRNA and negative microRNA plasmids were constructed and transient transfected into Bel-7402/5-Fu cells. Expression levels of HMGA2 mRNA and protein in microRNA transient transfectants were clearly reduced as compared with negative microRNA transfectants and untreated cells. Flow cytometry revealed increased in S phase in let-7 g microRNA cells. dimethylthiazol-diphenyltetrazolium bromide (MTT) results indicated that microRNA transfectants had a higher cell inhibition rate than the negative vector or untreated cells after treatment with 0.13-13 microg/ml 5-Fu. In addition, cyclin A was down-regulated in the let-7 g transfectants cells.The results showed that let-7 g microRNA contributed to an increase of 5-Fu-induced cell cycle inhibit in human hepatoma cell and sensitized cells to 5-Fu, leading to increased the effectiveness of the drug in treating hepatoma cancer.

This study was done to explore the role of microRNA-98 (miR-98) in cisplatin sensitization in human lung adenocarcinoma cell line. Differential expressions of miRNAs were analysed between cisplatin-resistant human lung adenocarcinoma cell line A549/DDP and its parental cell A549 by miRNAs microarray, of which 14 miRNAs were showed to be significantly (>2-fold) up-regulated and 8 miRNAs had marked down-regulation (<0.5-fold) in A549/DDP cells compared with in A549 cells. MiR-98, a member in the let-7 family, acts as a negative regulator in the expression of HMGA2 (high mobility group A2) oncogene, and it has been shown to have a nearly 3-fold decrease in A549/DDP cells. We found that elevated expression of miR-98 led to a higher sensitivity of A549/DDP cells to cisplatin, and the protein level of HMGA2, was clearly up-regulated in both A549/DDP and A549 cells by miR-98. Moreover, both Bcl-XL and Bcl-2, were down-regulated in the Pre-miR-98(TM) transfectants cells. We for the first time demonstrated that the expression of miR-98 increases cells spontaneous apoptosis and sensitizes cells to cisplatin at least in part via HMGA2 up-regulation. Our findings provided insight into some specific miRNAs in lung cancer as potential therapeutic targets.

Recently, we have reported tissue- and stage-specific expression of miR-195 in human hepatocellular carcinoma cells and so far, not many reports discuss the function of this microRNA (miRNA). Expression profiling of miRNAs revealed a limited set of miRNAs with altered expression in drug resistant hepatocellular carcinoma cell line BEL-7402/5-FU compared to its parental BEL-7402 cell line. Real-time PCR confirmed down-regulation of miR-195 in BEL-7402/5-FU cells. Western blots were performed to determine protein levels of LATS2, P53 and CDK2. MTT analysed the cell proliferation activity. Flow cytometry were performed to determine apoptosis rate. Up-regulation of miR-195 increased expression of LATS2 and increased apoptosis of HCC cells, while Anti-miR-195 treatment inhibited expression of LATS2. miR-195 over-expression inhibited the luciferase activity of a LATS2 3' untranslated region-based reporter construct in BEL-7402/5-FU cells. These results indicate that miR-195 could increase cell apoptosis by targeting LATS2 in hepatocellular carcinoma cells.

The role of microRNA-195 in developing acquired drug resistance in hepatocellular carcinoma cells was investigated. Expression profiling of miRNAs revealed a limited set of miRNAs with altered expression in drug resistant hepatocellular carcinoma cell line BEL-7402/5-FU compared to its parental BEL-7402 cell line. Real-time PCR confirmed down-regulation of miRNA-195 in BEL-7402/5-FU cells. Overexpression of miRNA-195 sensitized BEL-7402/5-FU cells to anticancer drugs. Consistent with these findings, miR-195 antisense oligonucleotide induced drug resistance in BEL-7402/5-FU cells. Also, the basal levels of the anti-apoptotic protein Bcl-w were high in BEL-7402/5-FU cells and miR-195 overexpression repressed Bcl-w protein level and inhibited the luciferase activity of a Bcl-w 3' untranslated region-based reporter construct in both BEL-7402/5-FU and BEL-7402 cells. These results indicate that miR-195 could improve the drug sensitivity at least in part by targeting Bcl-w to increase cell apoptosis in hepatocellular carcinoma cells.