Friend erythroleukemia cells induce angiogenesis in chick embryo chorioallantoic membrane and in human umbilical vein endothelial cells

The effects of Friend erythroleukemia cells on angiogenesis were studied in chick embryo chorioallantoic membrane assay and in human umbilical vein endothelial cells. In chorioallantoic membrane assay, the conditioned medium of Friend cells stimulated in vivo angiogenesis to an extent comparable to that observed with Prostaglandin El, used as positive control. Prostaglandin El added to conditioned medium of Friend cells did not further increase angiogenesis. Conditioned medium of Friend erythroleukemia cells also stimulated proliferation of human umbilical vein endothelial cells to an extent comparable to that observed with fetal bovine serum, used as positive control. Conditioned medium and fetal bovine serum together did not affect human umbilical vein endothelial cells proliferation, as compared to that observed when tested separately. These results seem to indicate that Friend erythroleukemia cells produce and secrete factors stimulating angiogenesis. These findings extend and confirm the hypothesis that successful angiogenesis is necessary for development of leukemias.

Tea-induced apoptosis in human leukemia K562 cells as assessed by comet formation.

Programmed cell death or apoptosis is a physiological process by which genetically damaged cells or undesired cells can be eliminated. Various morphological and molecular changes undergoing during the process of apoptosis are the formation of apoptotic blebs of the cell membrane, cell shrinkage, condensation of chromatin and the disruption of deoxyribonucleic acid (DNA) into typical fragments of multiples of 180 base pairs. These changes can be detected in a number of ways. DNA ladder formation, which is observed following gel electrophoresis technique although is widely accepted but does not reflect the DNA breakdown in individual cell and also may miss contributions from small sub-populations in a heterogeneous cell population. Alkaline comet assay as measured by single cell gel electrophoresis, on the other hand, accurately measures DNA fragmentation on a single cell level and allows analysis of subpopulation of cells. The assay was originally developed for measuring DNA damage of cells exposed to any genotoxic agent. However, the comet image generated by an apoptotic cell is different from that obtained with a cell treated for a short time with a genotoxic agent. Correlation of comet formation with various other established parameters of apoptosis is very important. The present study aims to correlate different features of apoptosis with the formation of comet tail in human leukemia K-562 cells using tea extracts. Apoptosis as measured by formation of apoptotic bodies, flow cytometric analysis, activation of caspase 3 and 8, and expressions of apoptosis related genes such as bcl-2 and bax showed high degree of correlation with comet tail moment. This indicates that comet assay can accurately reflect measure of DNA fragmentation and hence can be used to detect a cell undergoing apoptosis.

Tanshinone IIA, an ingredient of Salvia miltiorrhiza BUNGE, induces apoptosis in human leukemia cell lines through the activation of caspase-3

Tanshinone II-A is a derivative of phenanthrene-quinone isolated from Salvia miltiorrhiza BUNGE, a traditional herbal medicine that is known to induce antiinflammatory, anti-oxidative and cytotoxic activity. We have examined cellular effects of Tanshione II-A on HL60 human promyelocytic leukemic cells and K562 human erythroleukemic cells. Tanshione II-A induced a dose- and time-dependent DNA fragmentation into the multiples of 180 bp and specific proteolytic cleavage of poly(ADP-ribose) polymerase in both cell lines. PI-staining and flow cytometry analysis of K562 cells following Tanshione II-A treatment showed an increase of the cells possessing hypodiploid DNA indicative of apoptotic state of cells. Caspase-3 activity was significantly increased during Tanshinone II-A treatment of both HL60 and K562 cells, whereas caspase-1 activity was not changed. These results suggest that Tanshione II-A induced HL60 and K562 cellular apoptosis that may be associated with the selective members of caspase family. Copyright 2000 Academic Press.