Alkylphospholipids are synthetic compounds with relatively simple structures combining amphiphilic character and anticancer properties. It is possible to prepare different types of liposomes from APL if a high amount of cholesterol and a charged component is added. The biological relevant properties can be changed by sterical stabilization of these vesicles by the incorporation of up to 10 mol% poly(ethylenglycol) derivatives of phosphoethanolamine. This incorporation increased the fixed aqueous layer thickness from 0.83 nm to 3.57 nm. As a result of this changed property the uptake of such liposomes by macrophages was reduced compared to liposomes without a sterical stabilization. APL liposomes are remarkably stable in buffer and in plasma. APL-liposomes are able to induce the release of tumoricidal factors like TNF and NO from different macrophage cell lines. The strongest release was induced by a synergistic action of liposomal APC and lipopolysaccharide. Sterical stabilization prevents such an activation process likely as a result of significantly reduced uptake and internalization by the macrophages. APL are highly therapeutically active in a number of hormone-independent human mammary carcinomas. Using the MaTu mammary carcinoma xenotransplanted to nude mice the sterically stabilized HPC-SUV have the strongest cancerostatic formulation.
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