Objective:To evaluate the underlying mechanism of Jianpi Jiedu Recipe(健脾解毒方,JJR)in the reversion of multidrug resistance concerning colorectal cancer in vitro and in vivo.Methods:Mice were treated orally with JJR at a daily 4.25 g/(kg-day)or injected with vinblastine(VCR)2.5 mg/(kg·day)for 3 weeks after having been inoculated with HCT8/V cells;tumor tissues were assayed by hematoxylin and eosin staining.Firstly,the effects of JJR on the expression of cyclooxygenase-2(COX-2)were tested by real-time polymerase chain reaction(PCR)technique and COX-2 gene silenced by siRNA.Secondly,the variation of intracellular concentration of oxaliplatin(L-OHP)was evaluated by the inductively coupled plasma mass spectroscopy(ICPMS)in HCT8/V and its COX-2 siRNA cells;the concentration of JJR combined with chemotherapeutic drugs and the reverse effect of multidrug resistance(MDR)in HCT8/V cells was evaluated by the MTT assay.Thirdly,real-time quantitative PCR and Western blot analysis were used to detect the multidrug resistance gene 1(MDR1)mRNA and P-gp expression.Results:JJR had an inhibitory effect on the growth of tumors in vivo,and it,in combination with chemotherapeutic drugs,could reverse the drug-resistance of HCT8/V cells and increase the sensitivity of HCT8/V cells to VCR,DDP,5-Fu,and THP.ICP-MS results showed that JJR could increase the concentration of drugs in HCT8/V cells(P<0.01).Furthermore,it was shown that JJR could reverse drug resistance of colorectal cancer cells by decreasing MDR1 expression and P-gp level via downregulation of COX-2,which has been represented as one of the major mechanisms that contributes to the MDR phenotype(P<0.01).Conclusion:JJR reversed multidrug resistance and enhanced the sensitivity to chemotherapy,which could be attributed to the down-regulation of COX-2 in MDR1/P-gp-mediated MDR colorectal cancer after chemotherapy. Objective: To evaluate the underlying mechanism of Jianpi Jiedu Recipe in the reversion of multidrug resistance of colorectal cancer in vitro and in vivo. Methods: Mice were treated orally with JJR at a daily 4.25 g / (kg -day) or injected with vinblastine (VCR) 2.5 mg / (kg · day) for 3 weeks after having inoculated with HCT8 / V cells; tumor tissues were assayed by hematoxylin and eosin staining. Firstly, the effects of JJR on the expression of cyclooxygenase-2 (COX-2) were tested by real-time polymerase chain reaction (PCR) technique and COX-2 gene silenced by siRNA. Secondarily, the variation of intracellular concentration of oxaliplatin (L- OHP) was evaluated by the inductively coupled plasma mass spectroscopy (ICPMS) in HCT8 / V and its COX-2 siRNA cells; the concentration of JJR combined with chemotherapeutic drugs and the reverse effect of multidrug resistance (MDR) in HCT8 / V cells was evaluated by the MTT assay. thirdly , real-time quantitative PCR and Western blot analysis were used to detect the multidrug resistance gene 1 (MDR1) mRNA and P-gp expression. Results: JJR had an inhibitory effect on the growth of tumors in vivo, and it, in combination with chemotherapeutic drugs, could reverse the drug-resistance of HCT8 / V cells and increase the sensitivity of HCT8 / V cells to VCR, DDP, 5-Fu and THP.ICP-MS results showed that JJR could increase the concentration of drugs in HCT8 / V cells (P <0.01) was shown that JJR could reverse drug resistance of colorectal cancer cells by decreasing MDR1 expression and P-gp level via downregulation of COX-2, which has been represented as one of the major mechanisms that contributes to the MDR phenotype (P <0.01). Conclusion: JJR reversed multidrug resistance and enhanced the sensitivity to chemotherapy, which could be attributed to the down-regulation of COX-2 in MDR1 / P-gp-mediated MDR colorectal cancer after chemotherapy.