Detection of P-glycoprotein in human leukemias using monoclonal antibodies.

Overexpression of a Mr 170,000 membrane glycoprotein (P-glycoprotein) is consistently associated with multidrug resistance in cell lines. Two monoclonal antibodies (Mab) against P-glycoprotein (265/F4 and C 219) were used to examine tumour samples from patients with leukemias for evidence of P-glycoprotein overexpression. High levels of P-glycoprotein (greater than 5% positive cells) were detected with both antibodies in samples from 3 out of 18 patients suggesting that a multidrug resistant phenotype may also occur in human leukemias.