Multidrug-resistance associated protein (MRP), a member of ATP-binding cassette superfamily transporters,confers multi-drug resistance by reducting intracellular drug concentrations and/or altering the pattern of intracellular drug distribution. Using mrp gene knockout models, researchers have found that a total block of mrp is compatible with life and its physiological functions seem to be an ATP-depending pump to co-transport free GSH and some presently unknown endogenous metabolites to protect the normal extracellular environment.

Purpose:To evaluate the feasibility and study the mechanism of buthionine sulfoximine (B SO) as an effective sensitizer to overcome cisplatin resistance caused by overex pressing multidrug resistance associated protein(MRP).Methods:T he vector pcDNA3.1(-)-MRP, which included the complete cDNA of mrp, was transf ected into human lung cancer cell line SPC-A-1 and the positive clone(SPC-A- 1/MRP) was screened by G418,MRP expression comfirmed by Werstern blot and immuno histochemistry. The cell line SPC-A-1/MRP(-) was constructed by transfected p lasmid pcDNA3.1(-) as control. Comparing the sensitivities of SPC-A-1/MRP and control cells to anticancer drug- cisplatin(CDDP) with or without 1mg/mL BSO w as done by MTT assay. At the same time, the changes of glutathione detoxifcation system (glutathione,glutathione S-transferase , glutathione peroxidase) by RT -PCR and biochemistry methods under treated with CDDP and/or BSO were determine d.Results:SPC-A-1/MRP cells showed 2 fold resistance to CDDP as compared to the parent S PC-A-1/MRP(-) cell line and the cytotoxicity was markedly enhanced by 1mg/m B SO at low cisplatin concentration. When treated with CDDP , accompanied by a hig her transscript of MRP, it was found there was greater GSH content and lower tot al GSH-Px activity in the resistant SPC-A-1/MRP cells. Combined with BSO, the GSH content decreased greatly ,the MRP mRNA was reduced and the transscript of GST and GSH-Px were increased although the activities of both GST and GSH-Px were all decreased.Conclusions:Cisplatin resistance can be caused by over-expression MRP, glutation detoxifcat ion system played an important role in MRP-mediated resistance which can be ove rcomed by BSO.

Purpose: To explore the relationship between the effect of docetaxel inducing apoptosis of non-small-cell lung cancer cell and intracellular level of reactive oxygen. Methods: SPC-AI lung cancer cells were treated with 10 -8mol/L docetaxel for 24 hours to observe the apoptotic morphological change under the electromicroscope and fluorescence microscope in ritro. The treated cells were harvested to analyze the cell cycles using flow cytometry and to estimate the intracellular reactive oxygen levels by staining with 2', 7-dichlorodihydrofluorescein diacetate and dihydroethidine. Results: After SPC-AI lung cancer cells were exposed to 10 ~ mol/L docetaxel for 24 hours, the typical apoptotic morphological changes were observed under the electromicroscope and fluorescence microscope. There was a higher reactive oxygen level in docetaxe-treated cells group than in control group. After 24 hours docetaxel exposure, there was a significant G2 ~'M phase arrest of SPC-AI lung cancer cells. Conclusions: Docetaxel can induce apoptosis in SPC-AI lung cancer cells through the mechanism of G2 ~ M phase arrest and by elevating intracellular level of reactive oxygen.

0.05). Conclusions In human liver microsome system in vitro,CYP1A2,2B6 and CYP2A6 contribute to the metabolism of 629.It is very important for bioreduction drugs design and development,and provide the basic experimental and theoretical profiles for extensive application in clinic.

Objective To investigate radiation induced bystander effect and its mechanism on hepatoma HepG2 cells under hypoxia condition. Methods Non-irradiated bystander hepatoma cells were co-cultured with irradiated cells or treated with the conditioned medium (CM) from irradiated cells, then micronuclei (MN) were measured for both irradiated cells and bystander cells. Results The MN yield of irradiated HepG2 cells under hypoxic condition was significantly lower than that under normoxia, the oxygen enhancement ratio of HepG2 cells of MN was 1.6. For both hypoxic and normoxic condition, the MN yield of bystander cells were obviously enhanced to a similar high level after co-culturing with irradiated cells or with CM treatment, and it also correlated with the irradiation dose. When the hypoxic HepG2 cells were treated with either DMSO, a scavenger of reactive oxygen species (ROS), or aminognanidine, an iNOS inhibitor, the yield of bystander MN was partly diminished, and the reducing rate of DMSO was 42.2%-46.7 %, the reducing rate of aminognanidine was 42 %. Conclusion ROS, NO and their downstream signal facets are involved in the radiation induced bystander effect of hypoxic HepG2 cells.