OBJECTIVE:To study the mechanism of histone deacetylase inhibitor RGFP109 in reversing resistance of glioma U251 cells. METHODS:TR/U251 cells resistance to temozolomide(TMZ)was extrablished. The test was divided into normal con-trol group,TMZ group(40 μmol/L)and TMZ(40 μmol/L)+RGFP109(0-120 μmol/L)different concentrations groups. After 24 h of adding into related medicines,CCK-8 was used to detect the cell survival rate and calculate the half inhibitory concentration (IC50). TUNEL and Annexin V/PI were used to detect the cell apoptosis in normal control group,TMZ group and TMZ+RGFP109 (42μmol/L)group. Immunoblotting was used to detect the O6-methyl guanine-DNA methyltransferase(MGMT),Survivin,B lym-phoma 2(Bcl-2),B lymphoma xL(Bcl-xL)protein expression;and gel migration test was used to detect the p65 acetylation level and its binding capacity with κB-DNA. RESULTS:Compared with normal control group,cell survival rate in TMZ+RGFP109 dif-ferent concentrations groups was obviously decreased (P<0.05),showing a concentration-dependent manner. When the RGFP109 concentration was 42 μmol/L,the sensitivity of TMZ to TR/U251 cells was the same with U251 cells. Compared with normal con-trol group,MGMT,Survivin,Bcl-2,Bcl-xL protein expressions in cells of TMZ groups were enhanced(P<0.01);p65 acetyla-tion level had no obvious changes,while the binding capacity of p65 and κB-DNA was strengthened (P<0.01). Compared with TMZ group,MGMT,Survivin,Bcl-2,Bcl-xL protein expressions in cells of TMZ groups were weakened(P<0.01);p65 acetyla-tion level was enhanced (P<0.01);and the binding capacity of p65 and κB-DNA was weakened (P<0.01). CONCLUSIONS:RGFP109 can reverse the resistance of U251 cells to TMZ by down-regulating the anti-apoptotic protein expressions adjusted by transcription factorκB(NF-κB)and weakening the binding of p65 andκB-DNA.