Yoko Matsumoto

Novel mechanism of hybrid liposomes-induced apoptosis in human tumor cells.

Hybrid liposomes can be prepared by simply ultrasonicating a mixture of vesicular and micellar molecules in a buffer solution. The physical properties of these liposomes, such as size, membrane fluidity, phase transition temperature and hydrophobicity can be controlled by changing the composition. Hybrid liposomes composed of dimyristoylphosphatidylcholine and polyoxyethylene (10) dodecyl ether were found to inhibit the growth of human promyelocytic leukemia (HL‐60) cells without using any drugs. Induction of apoptosis by hybrid liposomes in HL‐60 cells was verified on the basis of fluorescence microscopy and flow cytometry analysis, after fusion and accumulation of hybrid liposomes, which was revealed on the basis of microphysiometer. We elucidated the pathways of apoptosis induced by the hybrid liposomes. That is, hybrid liposomes fused and accumulated in tumor cell membranes, and the apoptosis signal first passed through mitochondria, caspase‐9 and caspase‐3, second through Fas, caspase‐8, caspase‐3 and then reached the nucleus. Hybrid liposomes themselves can induce apoptosis in human tumor cells along with high inhibitory effects on the growth of tumor cells.

Specific accumulation and growth inhibitory effects of hybrid liposomes to hepatoma cells In vitro

Specific accumulation and growth inhibitory effects of hybrid liposomes composed of 90 mol% dimyristoylphosphatidylcholine and 10 mol% polyoxyethylene(23)dodecyl ether were obtained in human hepatoma cells without affecting normal liver cells at all.

Enhanced inhibitory effects of extracts from Ginkgo biloba L. leaves encapsulated in hybrid liposomes on the growth of tumor cells in vitro

Abstract Inhibitory effects of extracts from Ginkgo biloba L. leaves with a variety of organic solvents and hot water on the growth of B-16 mouse melanoma (B-16 melanoma) and human lung adenocarcinoma (RERF-LC-OK) cells were examined. Although free extracts showed little inhibitory effects on the growth of tumor cells, extracts encapsulated in hybrid liposomes (HLs), which were composed of l -α-dimyristylphosphatidylcholine (DMPC) as a phospholipid and Tween 20 as a surfactant, exhibited inhibitory effects on the growth of B-16 melanoma cells. Significant inhibitory effects of petroleum ether extract (Extract “P”) encapsulated in HL on the growth of B-16 melanoma cells were observed. Further separation of Extract “P” using preparative layer chromatography (PLC) resulted in four fractions. Among them, one fraction had a remarkably high inhibitory effect (80%) on the growth of B-16 melanoma and RERF-LC-OK cells. These results suggest the presence of hydrophobic antitumor agents in G. biloba L. leaf.