Objective To investigate effects of xeroderma pigmentosum B(XPB) gene on IL-6 induced proliferation and apoptosis in human vascular smooth muscle cells (VSMC).Methods Recombinant plasmid pcDNA3.1-XPB and vacant vector plasmid pcDNA3.1 were transfected stably into VSMC by liposome,and these cells were incubated with IL-6 at a 100 U/ml for 48 hours.The experiments were divided into six groups:blank control group; pcDNA3.1 group; pcDNA3.1-XPB group;IL-6 group; IL-6 + pcDNA3.1 group; IL-6 + pcDNA3.1-XPB group.The expression levels of XPB,Bcl-2,Bax and wild type p53 (wt-p53) were detected through reverse transcription polymerase chain reaction (RT-PCR) and Western blotting.The cell survival,cell cycle and apoptosis were examined with 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry,respectively.Results The transfection of pcDNA3.1-XPB increased the expression of XPB,Bax and wt-p53 (P＜0.05 or P＜0.01),decreased the expression of Bcl-2 (P＜0.05 or P＜0.01),and reduced the IL-6 induced effects on decreasing the expression of Bax and wt-p53 and increasing the expression of Bcl-2(P＜0.05 or P＜0.01).The over expression of XPB inhibited the cell growth(q=2.95,P＜ 0.05),and reduced the positive effects of IL-6 on VSMC growth ( 102.6 +6.2) ％ vs.(124.5 + 7.9) ％,q=3.49,P＜0.05.The over expression of XPB increased the apoptosis rate of VSMC(P＜0.01 ) and the cell amounts of G0/G1 phase (q=2.99,P＜ 0.05),decreased the cell amounts of S phase(q=3.05,P＜0.05),and reduced the IL-6 induced effects on decreasing the apoptosis rate of VSMC(5.9±2.1)％ vs.(0.3±0.1)％,q=7.53,P＜0.01; the cell amounts of G0/G1 phase(70.9±6.7) ％ vs.(54.8±2.9) ％,q=6.91,P＜0.01 ;and on increasing the cell amounts of Sphase(20.2+3.6)％ vs.(36.4+7.2)％,q=8.54,P＜0.01.Conclusions XPB gene could inhibit VSMC proliferation,promote VSMC apoptosis,and reduce the effects that IL-6 promotes VSMC proliferation and inhibits VSMC apoptosis.Therefore,XPB gene is likely to be potential molecular target for treatment of atherosclerosis.