Journal of Carcinogenesis & Mutagenesis

Abstract

Vector-Based let-7a miRNAs Function as Suppressors of Multiple Oncogenes in SK-N-MC and SHEP Neuroblastoma Cells

Guan J, Guo S, Zeng X, Luo Y, Yang T and Cao J

Objective: This study was designed to determine the anti-tumor effect of vector-based let-7a miRNA in neuroblastoma cell lines.
Methods: A tetracycline (tet)-inducible let-7a expression vector was constructed and used to stably transfect SKN- MC and SHEP neuroblastoma cells. The effects of let-7a overexpression induced by tetracycline on cell proliferation and adhesion were analyzed in vitro by MTT assays and adhesion assays. The mRNA expression of the let-7 target oncogenes NRAS, KRAS, c-myc, and HMGA2 was examined by quantitative real-time reverse transcription polymerase chain reaction. Protein expression of N-RAS, K-RAS, c-Myc, HMGA2, NeuN, and β3- tubulin was analyzed using western blot and immunocytochemistry. Morphology of SK-N-MC and SHEP cells was also observed. Additionally, the let-7a-inducible vector-transfected SHEP cells were subcutaneously injected in nude mice, and tumor growth in vivo was also evaluated.
Results: Let-7a expression was significantly induced in neuroblastoma cells and inhibited cell proliferation and adhesion in both SK-N-MC and SHEP cells. Let-7a up-regulated β3-tubulin and NeuN expression in SK-N-MC and SHEP cells. However, short neurite-like outgrowth was observed only in SK-N-MC cells, but not in SHEP cells. Let-7a overexpression decreased the expression of N-RAS and HMGA2 proteins in both SK-N-MC and SHEP cells. c-Myc expression also decreased in SK-N-MC cells. The tumor sizes of SHEP xenografts in the tet-inducible group were smaller than those in the mice without tetracycline induction.
Conclusion: Taken together, our data demonstrate the anti-tumor effects of vector-based let-7a miRNA overexpression in SK-N-MC and SHEP neuroblastoma cells against multioncogenes. Let-7a miRNA is a potential therapeutic molecule for the treatment of neuroblastoma.