MicroRNA-326 inhibits melanoma progression by targeting KRAS and suppressing the AKT and ERK signalling pathways.

Melanoma is the seventh most common malignancy in females and the fifth most common cancer in males worldwide. An increasing number of studies have reported that microRNA (miRNA) dysregulation is frequently observed in various types of human cancers, including melanoma. Abnormally expressed miRNAs play an important role in melanoma formation and progression by serving as potential biomarkers and therapeutic targets. Recently, miRNA-326 (miR-326) has been reported to be differentially expressed in various types of tissues and play important roles in tumourigenesis and tumour development. However, the expression levels, biological roles and underlying mechanisms of miR-326 in melanoma remain unknown. In the present study, we demonstrated that miR-326 was significantly downregulated in melanoma tissues and cell lines. Functional assays revealed that the enforced expression of miR-326 suppressed melanoma cell proliferation and invasion and increased cell apoptosis in vitro. Using bioinformatic analysis, Kirsten rat sarcoma viral oncogene homolog (KRAS) was predicted as a potential target of miR-326. Luciferase reporter assay confirmed that miR-326 could directly target the 3'-untranslated region of KRAS. In addition, reverse transcription-quantitative polymerase chain reaction and western blot analysis revealed that miR-326 upregulation decreased the KRAS expression in melanoma cells at both the mRNA and protein level. Furthermore, KRAS was upregulated in melanoma tissues and inversely correlated with miR-326 expression. In addition, the KRAS knockdown phenocopied the tumour-suppressing effects of miR-326 overexpression on melanoma cells. The restoration of the expression of KRAS markedly reversed the antitumour effects induced by miR-326 overexpression in melanoma cells. Further experiments indicated that miR-326 inactivated the AKT and ERK signalling pathways in melanoma. Collectively, these results revealed that miR-326 serves as a tumour suppressor in melanoma by targeting KRAS and regulating the AKT and ERK signalling pathways, indicating that miR-326 may be a promising therapeutic target for melanoma patients.