Cancer protection associated with the consumption of olive products is well established, but not for leukemia. The protective effects of olive (Olea europaea L.) leaves were investigated by incubating human promyelocytic leukemia HL-60 cells with olive leaf extracts (OLEs) from seven principal Tunisian olive varieties, namely, Chemchali, Chemlali, Chétoui, Gerboui, Sayali, Zalmati and Zarrazi. The results showed significant growth inhibition of HL-60 cells incubated for 48 h with a 100-fold dilution of each OLE which had been obtained by incubating 10 g of dried leaves in 100 ml of 70% ethanol for one week with subsequent ultrafiltration. DNA fragmentation was observed in the cells incubated for 19 h with a 100-fold dilution of the Chemchali, Chemlali and Zalmati extracts. The results of a nitroblue tetrazolium (NBT) assay revealed NBT reduction, a differentiation marker, by the OLE-treated cells after an overnight incubation. The Gerboui extract showed the highest NBT reduction ability at more than 90%. An HPLC analysis revealed the presence of apigenin 7-glucoside in the extract, which was found in subsequent experiments to be responsible for the Gerboui extract-mediated cell differentiation.

Genistein is an isoflavonic phyto-oestrogen contained in soya beans. It is thought to display anti-cancer effects. This study was designed to investigate its effect on human intestinal colon cancer Caco-2 cells. MTT assay, flow cytometric analysis and western blotting were used to investigate the effect of genistein on cell proliferation, cell cycle progression and protein alterations of selected cell cycle-related proteins in Caco-2 cells. Our results showed that genistein and daidzein significantly suppressed cell proliferation. Genistein treatment was demonstrated to modulate cell cycle distribution through accumulation of cells at G2/M phase, with a significant decreasing effect of Cyclin B1 and Serine/threonine-protein kinase 2 (Chk2) proteins expression. However, daidzein did not alter the cell cycle progression in Caco-2 cells. All these observation strongly indicate that genistein has anti-proliferative effect in human intestinal colon cancer Caco-2 cells through the downregulation of cell cycle check point proteins, Cyclin B1 and Chk2.

Indoleacetic acid falcarindiol ester (compound 1) has previously been isolated and purified using an SiO2 column and ODS HPLC from an acetone extract of Japanese ivy (Hedera rhombea). Here we investigate the differentiation-inducing activity of compound 1 using the human promyelocytic leukemia HL-60 cell line. The effect of compound 1 on HL-60 cell viability and proliferation was determined at different treatment times using the 3-(4,5-dimethythiazol-2-yl)-2,5-diohenyl-2 H-tetrazolium bromide (MTT) assay and flow cytometry analysis. Also cell cycle kinetics were examined using propidium iodide staining of DNA. Cell differentiation was assessed by specific and non-specific esterase double staining assays, and by detection of the cell surface differentiation markers CD11b and CD14 using flow cytometry. The results showed HL-60 cell growth inhibition at 0.1 and 1.0 microg/mL compound 1, whereas 10 microg/mL was cytotoxic. The growth suppression induced by compound 1 was accompanied by G0/G1 phase arrest in the cell cycle at 1.0 microg/mL. Moreover, staining and immunochemical analysis indicated that compound 1 induced granulocytic differentiation in HL-60 cells. This is the first report describing granulocytic differentiation activity of a falcarindiol derived polyacetylenic compound on leukemia cells.

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