Abstract: Objective To explore the effects of reactivator of P53 and induction of tumor apoptosis (RITA) on the cell apoptosis of lung squamous carcinoma cells and its mechanism. Methods MTT assay was used to detect the effects of different concentrations of RITA on the proliferation of H226 and BEAS-2B cells, and the appropriate intervention concentration was screened. After treatment with 0, 0.05, 0.1 and 0.2 μmol/L RITA, reactive oxygen species (ROS) content and apoptosis rate of H226 cells were detected by flow cytometry. The expression levels of P-Src, Src, P-Stat3, Stat3, Bim, Mcl-1, Survivin, Bax and Bcl-2 in H226 cells were detected by Western blot assay. After H226 cells were treated with 0.2 μmol/L RITA and 5.0 mmol/L antioxidant N-acetylcysteine (NAC) at the same time, it was observed whether NAC could reverse the biological effects of RITA on H226 cells. Results With the increment on concentration from 0.05 to 0.2 μmol/L, the viability activity decreased with the increased concentration of RITA. The half inhibitory concentration (IC50) in H226 cells was (0.130±0.008) μmol/L. There was no significant effect on the proliferation of BEAS-2B cells at the same concentration. RITA 0-0.2 μmol/L increased the ROS level and induced apoptosis in H226 cells. Meanwhile, 0-0.2 μmol/L RITA also down-regulated the protein expressions of P-Src, P-Stat3, Mcl-1, Survivin and Bcl-2, while up-regulated Bim and Bax expression. After NAC treatment, the effect of RITA on inhibiting Src/Stat3 pathway activity and inducing apoptosis was reversed in H226 cells. Conclusion RITA inhibits the activity of Src/Stat3 pathway by increasing ROS generation, and thus induces apoptosis of H226 cells.

Key words: lung neoplasms, carcinoma, squamous cell, reactive oxygen species, genes, P53, apoptosis, STAT3 transcription factor, RITA, src-family kinases