MURINE BISPECIFIC ANTIBODY 1A10 DIRECTED TO HUMAN TRANSFERRIN RECEPTOR AND A 42-KDA TUMOR-ASSOCIATED GLYCOPROTEIN

Previously, we observed that bispecific antibodies (''antigen forks'') that bound to certain pairs of different tumor surface antigens could inhibit cell growth, The chemically linked heteroconjugate of MAb 454 A12 (murine IgG1 recognizing human transferrin receptor) and 317G5 (mu rine IgG1 recognizing a 42-kDa tumor-associated glycoprotein) was part icularly inhibitory toward human colorectal cancer cell lines, and the iron-chelating agent deferoxamine was found to augment inhibition of tumor cell growth by this antigen fork, Further experiments revealed t hat an antigen fork constructed by linking Fab' fragments instead of w hole antibodies retained activity, which led us to construct a fork-se creting hybrid hybridoma, Hybridoma 454A12 was fused with hybridoma 34 F2 (murine IgG1 with the same specificity as 317G5). Hybrid hybridomas whose supernatants blocked binding of both 454A12 and 34F2 probes wer e further tested for the ability to block growth of SW948 human colore ctal cancer cells in an MTT growth assay, and were chosen for subcloni ng, Ascites produced by clone 1A10 was purified by affinity and cation exchange chromatography. Purified 1A10 bispecific antibody showed gro wth inhibitory activity comparable to that of a chemically linked hete roconjugate of its parental antibodies 34F2 and 454A12. Adding deferox amine greatly enhanced the inhibitory activity of 1A10 and effectively prevented regrowth of tumor cells in vitro. By heterologously crossli nking two antigens that are coexpressed on many tumor cells, this bisp ecific antibody is able to inhibit tumor growth with enhanced selectiv ity. (C) 1996 Academic Press, Inc.