[Functional redistribution of caspase activities in K562 cells, induced for differentiation and apoptosis by...

Activity of caspases 3, 9, 6 has been investigated in erythroleukemia K562 cells under conditions of induction or inhibition of erythroid differentiation using cyclophosphane (N'-bis-(beta-chlorethyl)-N'-O-trimethyl ester of diamide of phosphoric acid, antitumour agent of oncologic practice) and two newsynthetic thiazophosphol derivatives--2-t-butylamino-4-thioxo-4-chloromethyl-1,3,4-thiazophosphol-2-in, 2-anilino-4-thioxo-4-chloromethyl-1,3,4-thiazophosphol-2-in as modulators of differentiation. The treatment of K562 cells with cyclophosphane and the t-butylamine thiazophosphol derivative was accompanied by the induction of erythroid differentiation, activation of caspase 3 and caspase 9, followed by subsequent induction of apoptosis. Treatment of cancer cells with the aniline thiazophosphol derivative led to a loss of erythroid differentiation in cells and increased expression of the monocyte lineage associated surface antigen, activation of caspases 3, 9, 6, and induction of apoptosis. In the latter case the level of activity of caspase 3 was lower than in the cells treated in the presence of other compounds. Possible functional redistribution of activity of cell caspases involved in the realization of different directions of differentiation and apoptosis in K562 cells is discussed.