Summary Cells from two adenocarcinomas, an adenoma and a metastatic node were isolated in soft agar. Expression of antigens, CEA, Y haptenic blood group and 791T-p72, defined by a range of candidate antibodies for tumour targeting was assessed.All of the cells expressed low levels of CEA but high levels of the Y haptenic blood group antigen although there was enormous inter and intraclonal variation. Of particular interest was the membrane expression of 791T-p72 antigen on all of the dividing tumour cells as previous studies had shown that 791T/36 antibody reacted with tumour stromal elements rather than malignant cell surfaces.The DNA content was abnormal in all of the cells whether they were derived from diploid or aneuploid primary tumours. They all grew readily in athymic mice and at least one monoclonal antibody, 791T/36, localised efficiently within these xenografts.Clonogenic cells therefore expressed the three tumour-associated antigens, several at higher levels than observed in the primary tumour. Monoclonal antibody 'cocktails' should therefore allow antibody mediated drug cytotoxicity to be effective at eradicating rapidly dividing tumour cells.

Immunoscintigraphy using radioisotope-labelled monoclonal antibody prepared against osteosarcoma 791T cells was used to detect a primary osteosarcoma. The eight-centimetre tumour was detected using rectilinear scintigraphy of 131I-labelled antibodies. Image enhancement was achieved by subtraction of blood-pool radioactivity labelled with technetium-99m. The ratio of tumour to non-tumour uptake of radioactivity (5:1) suggested that antibody targeting of therapeutic agents is feasible.

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