DEVELOPMENT AND CHARACTERIZATION OF ANTIRENAL CELL-CARCINOMA X ANTICHELATE BISPECIFIC MONOCLONAL-ANTIBODIES FOR 2-PHASE TARGETING OF RENAL-CELL CARCINOMA

To test a two-step approach for radioimmunotargeting of renal cell can cer, quadroma cells secreting antichelate x anti-renal cell carcinoma bispecific antibodies were obtained by somatic cell fusion, Five monoc lonal antibodies against the chelate 1,4,7-triaxaheptane-N,N',N''-pent aacetic acid (DTPA) were produced and characterized, Competitive bindi ng assays indicated that the anti-DTPA antibodies reacted with DTPA ch elated with indium, yttrium, chromium, iron, or zinc, The affinity con stants of the anti;DTPA antibodies for In-111-DTPA ranged from 0.19 to 0.23 nM(-1). Using different chelates, a remarkable chelate specifici ty of the anti-DTPA antibodies was demonstrated, The chelates recogniz ed by the antibodies DTIn1, DTIn2, and DTIn4 share a N(N'')-diacetic a cid group, whereas the chelates recognized by DTIn3 share a N'-acetic acid group, suggesting the presence of different essential structures within the DTPA molecule that determine the reactivity of the antibodi es. Five anti-DTPA antibody-producing hybridomas were used for somatic cell fusion with hybridoma G250 directed against renal cell carcinoma , resulting in three bispecific antibody-producing quadroma cell lines , The bispecific monoclonal antibodies were purified from ascites flui d using protein A affinity chromatography followed by hydroxylapatite chromatography and/or cation exchange chromatography, Of the total IgG amount present in the ascites fluid, 10-15% represented the bispecifi c antibodies, These bispecific antibodies will allow testing and optim ization of a two-step approach for radioimmunotargeting of chelated ra dionuclides.