Alterations of membrane constituents in carcinomas and drug resistant tumour cells

Abstract

The cell surface changes occuring during malignant transformation are discussed. In malignant tumours, the amount of some membrane associated proteins (LETS1), myosin, collagen etc) is decreased while the amount of glycoproteins and the activity of glycosyltransferases is increased. The activity of some hydrolytic enzymes is also increased in transformed cells. The composition of membrane lipids is remarkably altered in malignant cells. The cell surface properties of the drug resistant and sensitive tumour cells are different. We found the resistant L1210 cells to be less agglutinable than the sensitive line. Pretreatment with Colchicin and Vincristin significantly reduced the agglutinability of sensitive L1210 cells. The sensitive L1210 cells are able to incorporate 3H Colchicine and 14C Vincristine more readily than the resistant L1210 cells. Growth stimulating agents like insulin, high serum concentration etc. are more effective with drug sensitive cells than with the drug resistant line.