Expression patterns of microRNA-218 and its potential functions by targeting CIP2A and BMI1 genes in melanoma.

Melanoma is the most aggressive skin cancer, and it is typically resistant or rapidly develops resistance to a variety of chemotherapeutic agents. microRNAs (miRNAs) play a part in the occurrence and development of malignant melanoma. In this study, we analyzed the miR-218 expression level in melanoma patients and cell lines and observed alterations in proliferation, cell cycle, migration, and invasion by increasing miR-218 expression in melanoma cell lines. We also performed bioinformatic analyses using TargetScan and miRanda and cloned both the wild-type and mutant versions of the human cancerous inhibitor of protein phosphatase 2A (CIP2A) and B lymphoma Mo-MLV insertion region 1 (BMI1) 3'-UTR fragments into the pmirGLO reporter vector. We then used the Dual-Luciferase assay system, quantitative real-time RT-PCR (qRT-PCR), and Western blot analysis to determine that miR-218 targeted the 3'-UTR of the oncogenes CIP2A and BMI1 and thus regulated the biological process of melanoma. We further demonstrated that CIP2A and BMI1 knockdown phenocopies miR-218 overexpression. In conclusion, our findings have shown that miR-218 is downregulated in melanoma. By targeting CIP2A and BMI1, miR-218 regulates the proliferation, migration, and invasion of the melanoma cell lines A375 and SK-MEL-2, indicating that miR-218 plays a pivotal role in melanoma development.