Expression levels of microRNA‑455 and its potential functions by targeting IGF‑1R in melanoma.

Melanoma has the highest fatality and malignancy of all skin cancers. In cancer, microRNAs (miRNAs) act as tumor suppressors or oncogenes, and inactivation of oncogenic miRNAs or restoration of tumor suppressor miRNAs has potential for cancer treatment. In the present study, miR‑455 expression levels were examined in melanoma tissues and cell lines, and miR‑455 was significantly downregulated in melanoma compared with matched normal tissues or normal epidermal melanocytes. In addition, increasing miR‑455 expression in melanoma cells reduced cell proliferation and invasion. Bioinformatic analysis revealed that insulin‑like growth factor 1 receptor (IGF‑1R) was a putative target of miR‑455. Luciferase reporter assays, reverse transcription‑quantitative polymerase chain reaction and western blot confirmed that miR‑455 targeted the 3'‑untranslated region of IGF‑1R and thus regulated the biological processes of melanoma cells. IGF‑1R knockdown resulted in similar effects as miR‑455 overexpression in melanoma cells. In summary, these findings indicated that miR‑455 was downregulated in melanoma, and inhibited proliferation and invasion of melanoma cells through directly targeting IGF‑1R. This also suggested that the restoration of miR‑455 may be worth investigation as a therapeutic treatment for patients with melanoma.