EXPRESSION OF NUCLEAR ONCOGENES AND MARKERS OF DIFFERENTIATION IN HUMAN MULTIDRUG-RESISTANT HBL100 CELL-LINE

Colchicine-resistant variants (HBL100/R(C)) derived from the HBL100/S cell line are described. HBL100/R(C) exhibit a typical multidrug-resis tant phenotype, unstable in the absence of colchicine (Col) (HBL100/R0 ). We have analyzed the expression of nuclear oncogenes (c-myc, c-myb, c-jun and c-fos) and of surface and cytosolic markers of differentiat ion in sensitive and treated or untreated resistant HBL100 cells. Doxo rubicin (DOX) and Col treatment decreased the levels of c-myc, and c-m yb mRNA with an increase in the levels of c-jun and c-fos. In parallel we found an increase in expression of markers of differentiation and the degree of multidrug-resistance after treatment with DOX and Col. C ol, like DOX, modulated the expression of nuclear oncogenes and induce d the markers of differentiation in HBL100 cells. The coordination of nuclear oncogene expression may promote both the differentiation progr am and the multidrug-resistance phenomenon.