TYRPHOSTIN INDUCED GROWTH-INHIBITION - CORRELATION WITH EFFECT ON P210(BCR-ABL) AUTOKINASE ACTIVITY IN K562 CHRONIC MYELOGENOUS LEUKEMIA

We have examined a series of tyrosine kinase inhibitors structurally r elated to erbstatin (tyrphostins) for inhibition of p210(bcr-abl) auto kinase activity in vitro and for growth inhibition of chronic myelogen ous leukemia (CML) K562 cells. Of the tyrphostins with IC50 for growth <50 mu M, AG814, AG946, AG952, AG896, AG953, AG956 and AG957 (structu rally related to lavendustin A and piceatannol) completely inhibited p 210(bcr-abl) kinase activity in an immune complex kinase assay. Anothe r group of tyrphostins (AG807, AG568, AG763, AG1076, AG490, AG1318, AG 556, AG1319, AG555 and AG1111) inhibits growth of K562 cells but not p 210(bcr-abl) tyrosine kinase activity. Of the compounds which inhibit growth and p210(bcr-abl) tyrosine kinase activity, AG957 inhibits DNA synthesis as early as 2 h (60% inhibition at 20 mu M of AG957), a time and concentration of drug where RNA and protein synthesis were not af fected. AG957 inhibits p210(bcr-abl) tyrosine phosphorylation in livin g cells by 1 h without an inhibition of total protein phosphorylation. Growth inhibition by AG957 was reversible after 4 h of exposure, but irreversible after 24 h. AG957 can be considered as an important lead structure for the development of anti-bcr-abl tyrosine kinase antagoni sts. These data also raise the possibility that bcr-abl kinase activit y is directly linked to maintenance of DNA synthesis in Philadelphia c hromosome positive (Ph(+)) CML cells.