OBJECTIVETo stably reverse the multidrug resistance (MDR) of breast carcinoma cells in vitro.

METHODSTwo anti-mdr-1 ribozyme plasmids, RZ196 and RZ179, were constructed with EGFP as reporter gene and transfected into drug-resistant breast carcinoma cells in vitro. The expression of EGFP was observed by laser confocal microscopy. Flow cytometry, RT-PCR and Rhodamine123 efflux assay were used to detect P-glyco protein (p-gp) and mdr-1 mRNA.

RESULTSAfter transfection with RZ196 and RZ179, the mdr-1 indices were reduced from 2.20 to 0.76 and 1.40, the expression rates of p-gp were reduced from 55.0% to 4.6% and 18.2%, the fluorescence intensity increased from 22.0% to 46.2% and 70.1%, TCL reduced from 75% to 28% and 43% respectively. In addition, the expression of ribozyme plasmid in tumor cells was stable under G418 selection. After two months, the mdr-1 indices remained at 0.81 and 1.47 in the cells transfected RZ196 and RZ179 respectively. The expression rates of p-gp were 5.2% and 19.5% and the Rh123 fluorescence intensity was 51.4% and 71.6% respectively.

CONCLUSIONSBoth anti-mdr-1 ribozyme RZ196 and RZ179 can stably reverse MDR phenotype of breast carcinoma cells in vitro. RZ196 construct appears to be more effective.