Objective  To investigate the roles and regulation mechanism of miR-31 in human cutaneous squamous cell carcinoma (cSCC) growth.

  Methods  cSCC cells were transfected with the antisense oligonucleotide (ASO) of miR-31, and the cSCC growth was tested by colony formation and in vivo tumor formation assays. The target gene of miR-31 was validated by Western blot and green fluorescent protein (GFP) reporter assay. The cells were then transfected with the siRNA of the target gene, and the effect of the target gene on cell growth was preformed by colony formation assay. Finally, real-time PCR and immunohistochemistry were used for analysis of the expression of miR-31 and its target gene.

  Results  miR-31 ASO resulted in a low number of cell colonies and small tumor volume (P < 0.05). Western blot showed that the cells with miR-31 ASO had a higher protein level of large tumor suppressor homolog 2 (LATS2) than the control. The 3' UTR of LATS2 had a binding site with miR-31, and miR-31 ASO increased the GFP intensity controlled by LATS2 3' UTR, whereas no effect was observed on the mutant LATS2 3' UTR. Western blot showed that LATS2 siRNA inhibited the expression of LATS2 protein by about 80%. Knocking down of LATS2 increased the colony number by about 70% or 1.3-fold in cSCC cells. Real-time PCR showed that miR-31 was overexpressed in most cSCC tissues, compared with normal tissues. An inverse relationship existed between miR-31 and LATS2 expression levels. Immunohistochemistry validated that LATS2 was downregulated in cSCC tissues.

  Conclusion  miR-31, which functions as an oncogene, promotes cSCC growth by suppressing LATS2 expression. Our data suggest that miR-31 is a potential miRNA-based therapeutic target for cSCC growth.