A simple in vitro method of screening panels of monoclonal antibodies for tumor binding.

We have developed a simple in vitro method of evaluating the relative binding properties of anti-tumor antibodies to human tumor and normal tissues. Cryopreserved surgical explants of tissues as 1 mm cubes are incubated in microtiter plate wells containing media and radiolabeled antibody. We show that the accumulation of antibody in tumor tissue is a specific process which may be reduced by preincubation with saturating levels of unlabeled specific antibody. Evaluation of 7 anti-breast and 4 anti-colorectal tumor antibodies against their respective tumor tissues showed good reproducibility of repeat measurements and up to a 100-fold difference in accumulation among different antibodies to the same tissue. Equivalent results were obtained with the same tissues employed fresh and after cryopreservation. Because of the simplicity of the assay, panels of antibodies may be screened against the large numbers of tumor and normal tissues required to identify superior antibodies for human trials.