Reversal of drug resistance in breast carcinoma cells by anti-mdr1 ribozyme regulated by the tumor-specific MUC-1 promoter.

Multidrug resistance (MDR) is a serious obstacle for cancer chemotherapy. The aim of this study was to reverse MDR of breast carcinoma cells specifically by degrading mdr1 mRNA with anti-mdr1 ribozyme. Our strategy was to limit the expression of ribozyme to only breast-derived cells, but not other type of cells. The results showed the recombinant ribozyme pEGFP-RZmuc was expressed in two kinds of breast carcinoma cells, but not in non-breast-derived cancer cells. Evaluation of chemosensitivity showed that a 15-fold reduction in drug resistance for Adriamycin and a 32-fold reduction in drug resistance for Vinblastine were observed in the transfected cells. Our results demonstrate the efficacy and selectivity of pEGFP-RZmuc to reverse MDR in drug resistant breast carcinoma cells in vitro.