Abstract： [Objective] To detect the expression levels of connexin43(Cx43),P-gp and COX-2 in bone marrow of patients with acute leukemia (AL),and investigate their relationship with the pathogenesis,prognosis and resistance of this condition.[Methods]Using SYBR green real-time quantitative reverse transcription polymerase chain reaction (SYBR-RT-PCR),the expression of Cx43,P-gp and COX-2 mRNA were detected in 77 AL patients at different phases,including 36 initially-treated,20 complete-remission (CR)and 20 relapsed.A follow-up was done in those initially lreated.[Results]Expression levels of Cx43,P-gp and COX-2 mRNA from initially-treated were 0.52±0.57,1.42 ±1.06,1.14±0.95;those from relapse AL patients were 0.20±0.40,2.29 ±1.11,1.69±0.81,respectively,those from CR patients were 0.95±0.37,0.93±-0.73,0.79±0.58,respectively,those from normal patients were 1.16 ±0.67,0.86±0.63,0.61±0.57.Expression levels of Cx43 mRNA in initially-treated and relapse AL patients were significantly lower than those in normal patients and CR patients (initially-treated P were 0.001,0.005;relapse patients were P＜0.001),while the comparison between normal patients and CR patients showed no statistical significance (P=0.185).Cx43mRNA expression level was negatively correlated with P-gp and COX-2 mRNA,and a negative correlation was noted of both two expressions in initially-treated and relapse groups (Cx43 mRNA and P-gp mRNA r were -0.471,-0.362,-0.526;Cx43 mRNA and COX-2 mRNA r were -0.479,-0.344,-0.471).A follow-up of four months was conducted in 36 initially-treated patients,eight of them died.The expression Cx43 in those who died was lower than that who survived.The difference was significant(t=2.16,P=0.042).[Conclusion] Cx43mRNA expression levels of initially-treated and relapse AL patients were lower than those in normal patients and CR patients,P-gp and COX-2 mRNA expression levels of initially-treated and relapse AL patients were higher than those in normal patients and CR patients.Cx43 expre-ssion probably is a favorable prognostic factor.Cx43 is participation in the genesis,development and drug resistance of AL.