SCINTIGRAPHIC DETECTION OF NEURAL-CELL-DERIVED SMALL-CELL LUNG-CANCER USING GLIOMA-SPECIFIC ANTIBODY

Radiolabeled GA-17, a murine monoclonal antibody that reacts specifically with glioma cells, bound to a small-cell lung cancer (SCLC) cell line NCI-H69 derived from neural cells, both in vitro and in vivo. The affinity constant of GA-17 F(ab')(2) fragment binding to NCI-H69 was 1.02x10(8)/M while that to the glioma cell line U87MG was 1.22x10(8)/M. Iodine-l25-labeled GA-17 F(ab')(2) fragments injected i.v. localized well in NCI-H69 cells xenografted in nude mice. The percentage of the injected dose per gram accumulated in the xenografted tumor was 6.87+/-1.34%g(-1) (mean+/-SD, n=5) 24 h after injection. On the other hand, control monoclonal F(ab')(2) fragments accumulated in the xenografted tumor at 0.75+/-0.30%g(-1). The tumor-to-blood ratio was 1.8 for NCI-H69, while that of control F(ab')(2) was 0.60. In conclusion, the radiolabeled GA-17 F(ab')(2) fragment is expected to be useful clinically to visualize the small-cell lung cancer and in radioimmunotherapy.