The uptake of a monoclonal antibody (Po66) in lung tumour cell aggregates involves a phagocytose-like phenomenon

Abstract

The efficacy of radioimmunotherapy with radiolabelled monoclonal antibody (Mab) depends on the amount of antibody taken up by the tumour and on its intratumoral distribution. Multicellular spheroids (MTS) of lung cell carcinoma was investigated to study cellular and subcellular distribution of a Mab Po66 labelled with I-125. We have shown that the incorporation of Po66 in MTS regularly increases during 3 days while Py, a non specific Mab, remains low. The distribution of radiolabelled studied by light and electron microscopy autoradiography have demonstrated that Po66 first localized on extra cellular debris, is then phagocyted and observed in the cytoplasm of viable cells. This mechanism of penetration and distribution of Mab Po66 is a new and interesting phenomenon, and emphasizes contribution of transmission electron microscopy in nuclear medicine.