Correlations between anthracycline resistance, drug accumulation and membrane glycoprotein patterns in solid tumors of mice.

Both impaired drug accumulation and appearance of a new membrane glycoprotein species (mol. wt. approx. 180,000) are often associated with high levels of drug-induced resistance to a group of natural products which includes adriamycin (ADR) and daunorubicin (DNR). In this study, we examined solid murine mammary, pancreatic and colon tumors varying in degrees of inherent or (in vivo) induced adriamycin resistance. Neither impaired drug accumulation nor alterations in membrane glycoprotein patterns were correlated with drug resistance in these tumors. These results suggest that permeability and glycoprotein alterations may only be associated with very high degrees of drug resistance.