HIF-1α Induces Multidrug Resistance in Gastric Cancer Cells by Inducing MiR-27a

Abstract

This study aimed to determine the correlation between HIF-1α and miR-27a expression and to evaluate the effect of inhibition of HIF-1α expression on miR-27a expression and drug resistance in gastric cancer (GC). In the present study, real time-PCR and Western blot were performed to detect the expression of HIF-1α in GC tissues and cell lines. Then, OCUM-2MD3/L-OHP cells were transfected with HIF-1α-siRNA, a miR-27a mimic or pcDNA-HIF-1α, and cell survival was determined via the MTT assay. The expression of HIF-1α, miR-27a, and MDR-related genes was measured via real time-PCR and Western blot. ChIP and dual luciferase activity assays were performed to assess the transcriptional regulation of HIF-1α and miR-27a. The results revealed that transfection with HIF-1α-siRNA markedly decreased the levels of miR-27a, resulting in dramatically enhanced inhibition of the proliferation rate of OCUM-2MD3/L-OHP cells. Compared to non-transfected cells, the survival rate was significantly reduced in the cells transfected with HIF-1α-siRNA after treatment with L-OHP. The cell survival rate was significantly increased in OCUM-2MD3/L-OHP cells transfected with the miR-27a mimic, whereas HIF-1α overexpression did not result in any clear change in cell survival. The results of the dual luciferase activity assay demonstrated that HIF-1α enhances the transcriptional activity of the miR27a promoter in cells transfected with a reporter plasmid containing the upstream promoter region of miR27a together with pcDNA-HIF-1α. ChIP analysis suggested that HIF-1α directly binds to the promoter region of miR27a. Inhibition of HIF-1α or miR27a expression decreased MDR1/P-gp, LRP, and Bcl-2 expression in OCUM-2MD3/L-OHP cells. Thus, we found that HIF-1α is closely associated with MDR in GC and that HIF-1α may suppress MDR1/P-gp, LRP and Bcl-2 expression by inhibiting miR-27a expression.

Inverse Correlation between IL-10 and HIF-1α in Macrophages Infected with Histoplasma capsulatum

“…Both of these could account for the increase seen at both the transcriptional and resultant protein level. A variety of micro RNAs which are regulated by HIF-1α have been shown to inhibit IL-10 production; these include miR-27a and Let-7 family members Let-7b, Let-7c, and Let-7f (85–89). While few studies have focused on the role of HIF-1α in controlling mRNA stability, it binds to VEGF mRNA and regulates transcript decay (90, 91).…”

Molecular mechanisms of hypoxia in cancer

“…Zhao and co-workers recently reported that HIF1alpha suppresses MDR1/P-glycoprotein in gastric cancer by inhibiting miR-27a expression in gastric cancer [62], and in colon cancer cells, inhibition of HIF1 leads to downregulation of p -glycoprotein and reversal of multidrug resistant phenotype [63]. In contrast, pronounced hypoxia has minor effect on p -glycoprotein expression and activity [64], while acidosis, a feature of the hpoxic micro-environement, increases p -glycoprotein activity [65].…”

Dysregulation of miRNAs as a signature for diagnosis and prognosis of gastric cancer and their involvement in the mechanism underlying gastric carcinogenesis and progression

“…MiR‐20b, miR‐27a, and miR‐181a have been shown to enhance the resistance of GC cells to EOX through targeting HIF1A/HIF‐1α, MDR1, and HIPK2 . The miR‐27a was another oncogene that could regulate HIF‐1α which is closely related to MDR in GC and may also inhibits LRP, Bcl‐2, and MDR1/P‐gp . Zhang et al reveal that miR‐107 was downregulated in MDR GC cell lines and elevated the sensitivity of GC cells to DOX by inhibiting drug efflux and suppressing P‐gp expression.…”