| Abstract: | Drug resistance is a major problem in the successful treatment of cancer. Resistance to one drug is often associated with cross-resistance to other anticancer agents. This is commonly seen with the "natural product" anticancer drugs such as the Vinca alkaloids and anthracyclines. In experimental systems, specific changes in plasma membranes characterize this "multiple drug resistance." The most prominent of these is the enhanced expression in several systems of high-molecular-weight glycoproteins ranging from Mr approximately equal to 150,000 to approximately equal to 180,000, the amount of which has been shown to be related to the degree of drug resistance. We report here the production of three monoclonal antibodies that bind preferentially to the surfaces of cultured human leukemic lymphoblasts resistant to the Vinca alkaloid vinblastine. Each antibody recognizes a surface membrane glycoprotein with molecular weights of 180,000 to 210,000. Additionally, two of the antibodies also recognize a second surface glycoprotein with molecular weights of either approximately equal to 155,000 or approximately equal to 130,000. All of these glycoproteins are overexpressed in the alkaloid-resistant cells. While a Mr approximately equal to 180,000 protein has been shown to be associated with multiple drug resistance, the other two glycoproteins have not been described previously in these cells. These antibodies may be useful in studies of the mechanisms of drug resistance, as well as in screening cells from drug-resistant patients for these resistance-associated glycoproteins. |
