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Tyrphostin induced growth inhibition: correlation with effect on p210bcr-abl autokinase activity in K562 chronic
1Laboratory of Biological Chemistry, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Abstract:
We have examined a series of tyrosine kinase inhibitors structurally related to erbstatin (tyrphostins) for inhibition of p210bcr-abl autokinase activity in vitro and for growth inhibition of chronic myelogenous leukemia (CML)K562 cells. Of the tyrphostins with IC50 for growth < 50 microM, AG814, AG946, AG952, AG896, AG953, AG956 and AG957 (structurally related to lavendustin A and piceatannol) completely inhibited p210bcr-abl kinase activity in an immune complex kinase assay. Another group of tyrphostins (AG807, AG568, AG763, AG1076, AG490, AG1318, AG556, AG1319, AG555 and AG1111) inhibits growth of K562 cells but not p210bcr-abl tyrosine kinase activity. Of the compounds which inhibit growth and p210bcr-abl tyrosine kinase activity, AG957 inhibits DNA synthesis as early as 2 h (60% inhibition at 20 microM of AG957), a time and concentration of drug where RNA and protein synthesis were not affected. AG957 inhibits p210bcr-abl tyrosine phosphorylation in living 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 antagonists. These data also raise the possibility that bcr-abl kinase activity is directly linked to maintenance of DNA synthesis in Philadelphia chromosome positive (Ph+) CML cells.
Insights
Tyrphostins, including AG957, inhibit p210bcr-abl kinase activity and K562 cell growth in chronic myelogenous leukemia (CML). AG957 shows potential as a lead for developing anti-bcr-abl tyrosine kinase antagonists.
Area of Science:
- Oncology
- Biochemistry
- Pharmacology
Background:
- Chronic myelogenous leukemia (CML) is characterized by the Philadelphia chromosome and the constitutively active p210bcr-abl tyrosine kinase.
- Targeting the p210bcr-abl kinase is a key strategy for CML treatment.
- Tyrphostins are a class of tyrosine kinase inhibitors with potential anti-cancer properties.
Purpose of the Study:
- To evaluate a series of erbstatin-related tyrphostins for their ability to inhibit p210bcr-abl autokinase activity.
- To assess the efficacy of these compounds in inhibiting the growth of K562 CML cells.
- To identify potential lead compounds for novel CML therapeutics.
Main Methods:
- In vitro kinase assays were used to measure p210bcr-abl autokinase inhibition.
- Cell growth inhibition assays were performed on K562 CML cells.
- Analysis of DNA, RNA, and protein synthesis was conducted.
- Inhibition of protein phosphorylation in living cells was assessed.
Main Results:
- Several tyrphostins, including AG957, demonstrated potent inhibition of p210bcr-abl kinase activity and K562 cell growth.
- AG957 significantly inhibited DNA synthesis within 2 hours without affecting RNA or protein synthesis.
- AG957 reduced p210bcr-abl tyrosine phosphorylation in living cells by 1 hour.
- Growth inhibition by AG957 was reversible after 4 hours but irreversible after 24 hours.
Conclusions:
- AG957 is a promising lead structure for developing novel anti-bcr-abl tyrosine kinase antagonists for CML treatment.
- The findings suggest a direct link between bcr-abl kinase activity and DNA synthesis maintenance in Philadelphia chromosome-positive CML cells.