Isolation, characterization, evaluation and mechanistic study of the antiproliferation fractions from shiitake (Lentinula edodes) exudates towards HL60 (acute promyelocytic leukemia) cell line.

摘要

Leukemia is a malignant cancer that involves the bone marrow and blood circulation systems. Leukemia results in the uncontrolled growth of abnormal (leukemic) white blood cells and may also invade other organs, including the liver, spleen, lymph nodes, testes, and brain. In 2007, about 44,240 new cases of leukemia were diagnosed and 21,790 patients died from all types of leukemias in USA.;Shiitake was first cultivated in China more than 800 years ago. It is the second most commonly cultivated edible mushrooms in the world nowadays. For a long time, shiitake has been valued for its unique taste and flavor and as a medicinal invigorant. According to ancient Chinese medicinal theory, consumption of shiitake was in favor of long life and good health. In China and Japan, shiitake has been used as both a food and a medicinal herb for thousands of years. It is the source of several well-studied preparations with proven pharmacological properties, especially the polysaccharide lentinan. Currently, most researches concentrate on the anticancer activities of the extracts from the fruiting body of shiitake, especially polysaccharides. Report about the anti-cancer effects of other components from the shiitake mushroom is scarce. The objectives of this investigations were: (1) to study the anticancer activities of brownish substances obtained during the solid medium culture of shiitake on specific cancer cell unes, especially HL60 cancer cell line; (2) to isolate and characterize the active compound(s) in the brown mushroom exudates; and (3) to propose the possible mechanism of actions, especially the function of the bcl-2 family genes and proteins.;In this study, a novel compound was isolated and purified from the solid culture medium (potato dextrose agar) of shiitake 1358 strain through series of methods, such as ethanol precipitation, macroporous resin column separation, semi-preparative high performance liquid chromatography separation and preparative thin-layer chromatography separation. Analyzing spectra from fourier transform infra-red spectroscopy, gas chromatography-mass spectrometry, 1-dimension and 2-dimension nuclear magnetic resonance, the chemical structure of the novel compound was determined and named as 4-amino-5,6-dihydrobenzo[d]oxonine-2,7(1H,4H)-dione. It could inhibit the proliferation of HL-60 leukemia cells significantly and with an IC50 of 1.56 mug/ml (7.123 mumol/L) in the 72-hour treatment. From the results, it is suggested that this compound could activate the G2 phase checkpoint control of the cell cycle to arrest the cell cycle in G2 phase. In addition, it could suppress the replicative DNA synthesis to inhibit the proliferation of HL-60 leukemia cells. The more important is that this compound can induce the apoptosis of HL-60 leukemia cells significantly through intrinsic and extrinsic apoptotic pathways. The compound could induce intrinsic and extrinsic apoptosis through the regulation of the apoptosis-related proteins, such as Fas ligand, Bax, Bcl-2, Caspase 8, Caspase 9, and Caspase 3. For intrinsic pathway, the compound might upregulate Bax, downregulated Bcl-2, activated the Caspase 9, subsequently activated Capase 3, and ultimately led to cell death. For extrinsic pathway, the compound upregulated the Fas ligand, cleaved and activated Procaspase 8 to active Caspase 8, further cleaved and activated Procaspase 3 to active Caspase 3 to commit the cells to apoptosis.