[Effect of TSC2 gene expression downregulation by lentivirus induced RNA interference on U937 cell line and its mechanism].

Objective: To investigate the effect of biology and mTOR pathway activity of down-regulated TSC2 gene expression on U937 leukemia cells. Methods: Gene expression was down-regulated by lentivirus induced RNA interference on TSC2 high expressed U937 cell line; the proliferation, apoptosis and differentiation were detected by CCK-8 assay, colony formation assay and flow cytometry; the gene expression level and protein kinase activity were detected by qRT-PCR and Western blot. Results: Down-regulated expression of TSC2 gene promoted U937 cell proliferation and colony formation ability ( P <0.05) . The proportion in G(0)/G(1) phase of TSC2 down-regulated U937 cell was much lower than that of the control cells [ (52.53±3.75) % vs (75.10±4.33) %, t =6.829, P =0.002], the S phase [ (22.43±1.00) % vs (15.47±1.20) %, t =-5.581, P =0.019] and G(2)/M phase [ (25.03±4.34) % vs (14.33±0.91) %, t =-5.413, P =0.013] was remarkably higher than that of the control cells ( P <0.05) . There were no statistically significant differences in cell apoptosis and differentiation ( P >0.05) . Down-regulation of TSC2 led to the increased activity of mTOR, 4EBP1 and S6K1, but did not influence the activity of AKT. The expressions of proliferation related cyclinD1, c-myc and PTEN were also up-regulated after TSC2 silenced, but the expressions of P27KIP and BCL-XL were not changed. Conclusion: Downregulation of TSC2 could promote the proliferation of U937 cells through up-regulation of mTOR activity.