CHARACTERISTICS OF HUMAN TUMOR-CELL LINES AFTER INDUCTION OF MULTIDRUG-RESISTANCE

A colorimetric technique was used to investigate some aspects of multi drug resistant (MDR)-induced cell lines. Continuous contact of the ind ucing agent with cells was necessary for MDR induction and this was fo llowed by a series of phases i.e., a selection phase (ESP) lasted up t o 6 days, a conditioning phase (CP) lasted up to 14 days and an expans ion phase (EP) lasted up to 7 days. Gene transfection to correct missi ng MHC class I antigens on the Fen cell line did not affect cell behav iour. Of particular interest was the finding that the withdrawal of th e MDR inducing agent did not reverse MDR phenotype immediately.