Determination of cytotoxicity in vivo using 111indium-labeled human tumor cells.

Loss of radioactivity from nude mice was determined after inoculation of human tumor cells prelabeled with [111In]indium oxine (111InOx). Elimination of 111In was increased somewhat by treating the mice with diphtheria toxin (DT), which is toxic selectively for human cells compared to mice. Calcium disodium edetate (CaNa2EDTA), a metal chelating agent, facilitated elimination of 111In and increased the difference in the rates of loss of radioactivity from mice bearing viable compared to DT-killed cells.