Immunoliposomes directed against colon adenocarcinoma cells: Delivery of 5-fluorodeoxyuridine to colon cancer cells and targeting to liver metastases

Tumor cell-specific immunoliposomes have been applied to deliver a dipalmitoyl derivative of 5-fluorodeoxyuridine (FUdR-dP) to CC531 adenocarcinoma cells. Immunoliposomes containing FUdR-dP caused stronger inhibition of CC531 in vitro cell growth than FUdR-dP in non-targeted liposomes. The immunoliposomes were not internalized but FUdR-dP was hydrolyzed intracellularly to FUdR within 24 h. Uptake and processing of FUdR-dP involves selective transfer from liposomes to the cell and subsequent digestion. In vivo, immunoliposomes enhanced tumor accumulation two-fold compared to non-immunoliposomes. The immunoliposomes appeared to be associated with tumor-associated macrophages rather than tumor cells. Both Fc receptors and scavenger receptors on macrophages are involved in the cell uptake