Objective         To investigate the underlying molecular mechanism of 5-aza-2′-deoxycytidine (5-Aza-CdR) in inhibition of renal carcinoma cell proliferation.       Methods         Cell proliferation was assessed by CCK-8 assay after the renal carcinoma cell lines 769-P and ACHN were treated with 5-Aza-CdR at different concentrations for 72 h. Flow cytometry was used to detect cell cycle in 769-

P cells after treatment of 5-Aza-CdR at different concentrations for 48 h. RT-PCR was used to detect the expression of methyltransferases DNMT1/3a/3b and suppressor of cytokine signaling 3 (SOCS3). The expression of P21 and SOCS3 at protein level was detected by Western blot analysis

and detected again in the 769-P cells with SOCS3 knockdown by small interfering RNA (siRNA) after 48 hours’ treatment of 5-Aza-CdR at different concentrations.       Results         CCK-8 assay revealed that 5-Aza-CdR remarkably inhibited the proliferation in the 2 cell lines in a dose-dependent manner (P0.05). 5-Aza-CdR treatment also resulted in the 769-P cells arrested at G

2

/M phase. RT-PCR showed 5-Aza-CdR down-regulated DNMT1 and DNMT3a but up-regulated SOCS3 (P0.05). Western blotting found that 5-Aza-CdR enhanced the expression of SOCS3 and P21. After knocking down the expression of SOCS3 of 769-P cells

we treated 769-P cells with 5-Aza-CdR for 48 h and found that  the up-regulation of P21 was weakened compared with control group.       Conclusion       5-Aza-CdR suppresses DNA methyltransferases

and enhances the expression of P21 mediated by SOCS3

and then inhibits the proliferation in renal carcinoma 769-P cells.