Growth inhibitory effects of DJ-1-small interfering RNA on laryngeal carcinoma Hep-2 cells

Cancer of the larynx is the commonest head and neck squamous cell carcinoma. The DJ-1 gene is a novel mitogen-dependent oncogene. Survivin is a structurally unique member of the inhibitors of apoptosis proteins. DJ-1 and survivin play important roles in carcinogenesis. The function of DJ-1, and the relationship between DJ-1 and survivin in laryngeal carcinoma, has never been explored. Small interfering RNAs (siRNAs) directed against the DJ-1 gene were initially transfected into laryngeal carcinoma Hep-2 cells with liposome. The viability of Hep-2 cells was then detected by the MTT assay. The changes in cell-cycle distribution were monitored by flow cytometry. Finally, changes in DJ-1 and survivin genes mRNA and protein levels were evaluated by semi-quantitative RT-PCR and Western blotting, respectively. Blocking expression of the DJ-1 gene with DJ-1-siRNA significantly suppressed the viability of Hep-2 cells. Treatment with DJ-1-siRNA resulted in a G2/M accumulation. Expressions of DJ-1 and survivin gene mRNA and protein levels were suppressed by DJ-1-siRNA in a dose-dependent manner. These data indicate, for the first time, that the DJ-1 gene may have an important role in the carcinogenesis of laryngeal carcinoma.