Radioimmune Assay and Characteristics of Antibodies to Macromomycin (NSC 170105)1

surface. MCR is unique in that it apparently inhibits DNA synthesis while binding to the plasma membrane (12, 13). This mechanism of action requires that the binding of MCR to the cell surface freezes on modifies the moleof the mom bnane in mediating cellular metabolism. Kunimotoetal. (13) hypothesize that the interaction between MCR and tumor cells is analogous to the interactions between bacteniocins and bacterial cells. Since MCR may serve as a valuable tool for elucidating membrane function and because the drug is active against the experimental model tumors that have some, although restricted, predictive value for clinical chemotherapy, de velopment of a sensitive, specific, and rapid method for estimating MCR concentrations in biological materials was warranted. This report describes the development of a ma dioimmune assay for MCR and use of the assay, as well as purified antimacromomycin antibodies, in the detection of MCR in body fluids and on tumor cell surfaces.