Adriamycin resistance in HL60 cells and accompanying modification of a surface membrane protein contained in drug-sensitive cells.

HL60 cells resistant to Adriamycin contain a 32P-labeled, Mr 150,000 surface membrane protein (p150) which is not detected in cells sensitive to drug. The levels of phosphorylation of this protein increase with increasing levels of resistance. Analysis of plasma membranes prepared from cells labeled with [14C]glucosamine shows, however, that both sensitive cells and those exhibiting an 80-fold increase in drug resistance contain essentially identical levels of a highly glycosylated Mr 150,000 protein. Identical results are obtained when cells are labeled with [14C]galactose or [14C]mannose. Limited proteolytic digestion of [14C]glucosamine-labeled p150 from sensitive and resistant cells shows that the glycopeptides formed are identical. Additional studies involving binding of proteins to insolubilized lectin indicate that 32P-labeled p150 is glycosylated. Polyacrylamide gel electrophoresis of p150 followed by silver staining shows no difference in the levels of this protein in sensitive and 80-fold drug-resistant cells. Further studies show that two-dimensional tryptic peptide maps of 125I-labeled p150 of sensitive and resistant cells are essentially the same. It has also been found that treatment of cells with 12-O-tetradecanoylphorbol-13-acetate followed by [14C]glucosamine labeling results in a selective decrease in the glycosylation of p150 of sensitive and resistant cells. TPA has an identical effect on the phosphorylation of p150 in cells resistant to drug. HL60 cells have also been examined for the presence of the Mr 170,000 to 180,000 P-glycoprotein. Using immunoblot analysis with a monoclonal antibody directed against the P-glycoprotein we did not detect the presence of this protein in membranes of drug-sensitive or -resistant HL60 cells. The results of this study suggest that Adriamycin resistance in HL60 cells may be related to a modified form of a protein contained in cells sensitive to drug. Proteins active in drug resistance in this system may be distinct from those described for other cell lines.