Objective Cyclin D1 gene plays a significant role in regulating cell cycle progression.It is reported that over-expression of cyclin D1 gene is intimately associated with origination,development and prognosis of tumor and is associated with tumor cells resistance to chemotherapy drug.Suppression of cyclin D1 protein expression leads to cellular chemosensitization.This study was to determine whether this effect also existed in chronic leukemia cell line K562 by inhibiting the expression of cyclin D1 protein through RNA interference.Methods Plasmid vectors expressing small hairpin RNA (shRNA) targeting at cyclin D1 gene were constructed and transfected into K562 cells by chitosan.Cyclin D1 protein was examined using Western Blotting analysis.The cell cycle and apoptosis were determined by flow cytometry.Cellular chemosensitization was evaluated by MTY assay.Results Expression of cyclin D1 protein was markedly down-regulated after transfection with pshRNA-419 and pshRNA-575 at 48 h.Down-regulation of cyclin D1 protein could affect the redistribution of cell cycle,induce apoptosis of K562 cells,decrease 50％inhibitoryconcentration (IC50) of adriamycin and enhance cellular chemosensitization.But there had no above biological effects observed after transfection with blank vector and control vector of m-pshRNA-790 at 48 h.ConclusionK562 cells could be chemosensitized by the down-regulation of cyclin D1 expression through RNA interference.

Objective : To investigate the effect and mechanism of methyltransferase-like 3 (METTL3) on the pro- liferation , migration , and secretion of inflammatory factors by synovial fibroblasts from rheumatoid arthritis (RA) . Methods : The expression of METTL3 in synovial tissue (SF) from 25 patients with rheumatoid arthritis and 25 pa- tients with osteoarthritis was detected by RT-qPCR and immunohistochemistry , respectively . The concentration of RNA m6A was detected by ELISA . RA synovial fibroblasts were isolated and cultured , and divided into NC ( nor- mal control) group , hi-METTL3 (overexpression of METTL3) group , si-METTL3 (knock-down METTL3) group , and STM2457 (METTL3 specific inhibitor) intervention group . Cell proliferation was detected by CCK-8 method . Apoptosis was detected by flow cytometry . And the concentrations of interleukin-6 ( IL-6) , interleukin-17A ( IL- 17A) , receptor activator of nuclear factor-kappa B ligand (RANKL) , and osteoprotegerin (OPG) in the superna- tant of cell culture were detected by ELISA . Results : Compared with synovial tissue of osteoarthritis , the expres- sion of mRNA m6A and METTL3 in synovial tissue of RA significantly increased (P < 0. 05) . After overexpression of METTL3 , the expression of m6A in synovial fibroblasts increased . The proliferation and migration abilities of SF in hi-METTL3 group were significantly improved , and their apoptosis did not change significantly . The secretion of cytokines IL-6 and RANKL of SF in hi-METTL3 group significantly increased , while the OPG significantly de- creased (P < 0. 05) . After interfering with METTL3 expression , the expression of m6A in synovial fibroblasts de- creased . Cell proliferation and migration of SF in siMETTL3 group significantly decreased . The secretion of cyto- kines IL-6 and RANKL significantly decreased , and OPG significantly increased ( P < 0. 05) . After intervention with METTL3 inhibitor STM2457 , the proliferation and migration of synovial fibroblasts were significantly reduced , and the secretion of cytokines IL-6 and RANKL significantly reduced , and OPG significantly increased ( P < 0. 05) . There was no significant difference in the expression of IL-17A among each group . Conclusion METTL3 may promote the proliferation and migration of RA synovial fibroblasts , enhance the expression of IL-6 and RANKL , and inhibit the expression of OPG through RNA m6A methylation modification .