INVESTIGATION OF THE ROLE OF MONONUCLEAR PHAGOCYTES IN THE TRANSPORTATION OF DOXORUBICIN-CONTAINING LIPOSOMES INTO A SOLID TUMOR

The present paper is concerned with the question whether cells of the mononuclear phagocyte system (MPS) function as a transport system for doxorubicin (DXR)-containing liposomes into solid tumors. The investigations were performed in solid IgM immunocytoma bearing Lou/M Wsl rats. In this tumor system macrophage accumulation was observed during DXR and cisplatin induced tumor regression. Tumor-bearing rats were treated i.v. with 1 mg/kg DXR (either free or entrapped in liposomes) for 4 consecutive days. Changes in the cellular composition of the tumor were studied by histology and cytology comparing free and liposomal DXR treatment. Therapy with DXR-liposomes (lip DXR) induced macrophage accumulation similar to free DXR. No differences in cellular changes in the tumor between both types of treatment were found. The DXR-content of tumor-associated cells was measured at various times during treatment with free or lip DXR by means of flow cytometry. Most DXR-fluorescence was associated with dead cells and ce...