c-erbB-2/p185-directed therapy in human lung adenocarcinoma

Background. These experiments were conducted to determine whether p185 can be therapeutically targeted in adenocarcinoma of the lung using an anti-p185-gelonin conjugate. c-erbB-2/p185 is overexpressed in up to one third of non-small cell lung cancers. CALU-3 is a human lung adenocarcinoma cell line that overexpresses p185. muMoAb-4D5 is a murine anti-p185 monoclonal immunoglobulin G1. Gelonin is a potent type 1 ribosomal inhibitory protein. Methods. 4D5 and gelonin were covalently modified and linked. Purification was confirmed by SDS-polyacrylamide gel electrophoresis. Dose-dependent cytotoxicity was quantified using 3H-thymidine uptake by CALU-3 cells after incubation with 4D5-gelonin conjugate or with control substances (4D5, gelonin, unconjugated 4D5 + gelonin, or control antibody MOPC-21). Results. The 4D5-gelonin conjugate showed a 50% inhibitory concentration of 3.5 × 10−10 mol/L, but 4D5 alone demonstrated no cytotoxic effect. Gelonin and the unconjugated 4D5-gelonin mixture had one tenth the cytotoxicity of the 4D5-gelonin conjugate (inhibitory concentration = 6.5 × 10−9 mol/L and 8.5 × 10−9 mol/L, respectively). The conjugate exhibited minimal toxicity against a p185-negative cell line (NIH3T3). Conclusions. Selective and efficient killing of human lung adenocarcinoma cells can be achieved in vitro using c-erbB-2/p185—directed therapy.