MicroRNA‑33b inhibits cell proliferation and glycolysis by targeting hypoxia‑inducible factor‑1α in malignant melanoma

: Malignant melanoma (MM) is the most aggressive type of skin cancer. MicroRNA (miR) has been implicated in the development and progression of MM; however, their underlying mechanism of action remains largely unknown. The present study aimed to investigate the role of miR-33b in MM. Reverse transcription-quantitative polymerase chain reaction data indicated that the expression of miR-33b was significantly reduced (P<0.01) in MM cell lines, including WM35, WM451 and SK-MEL-1, when compared with human melanocyte cells. Subsequently, WM451 and SK-MEL-1 cells were transfected with an miR-33b mimic or inhibitor. MTT assay data demonstrated that the viability of MM cells markedly decreased following miR-33b overexpression; however, viability was markedly upregulated following miR-33b knockdown. Additionally, the glycolysis level was examined. Results demonstrated that glucose consumption and lactic acid production were significantly downregulated (P<0.01) after miR-33b upregulation, whereas these levels significantly increased in MM cells transfected with miR-33b inhibitor (P<0.01), suggesting that miR-33b negatively mediates the glycolysis level in MM cells. Bioinformatics indicated that hypoxia-inducible factor (HIF)-1α was a putative target gene of miR-33b, and this was confirmed by a luciferase reporter assay, which demonstrated that miR-33b was able to directly bind to the 3' untranslated region of HIF-1α mRNA. Furthermore, the expression of HIF-1α was negatively regulated by miR-33b at the post-transcriptional level in MM cells. Overexpression of HIF-1α reversed the inhibitory effect of miR-33b on the proliferation and glycolysis in MM cells. Finally, the results of the present study demonstrated that hexokinase 2 and lactate dehydrogenase-A may be involved in miR-33b/HIF-1α mediated glycolysis in MM cells. In conclusion, these results suggest that miR-33b inhibits cell proliferation and glycolysis by targeting HIF-1α in MM.