Puromycin is a potent and specific inhibitor of tyrosine kinase activity in HL-60 cells.

The search for specific tyrosine kinase inhibitors constitutes a novel approach to the development of anticancer agents. Puromycin (PM) inhibits protein synthesis by causing the premature release of truncated PM-peptide complexes (PMPs), the structure of which predicts an inhibitory effect on tyrosine kinase activity (21). The present study was undertaken to investigate the effects of a low dose of PM (0.9 microM) on tyrosine kinase activity in HL-60 leukaemic cells. Experiments were specifically controlled to exclude inhibitory effects consequent on protein synthesis blockade. Soluble enzyme extracts derived from PM-treated cells showed attenuated phosphorylation of two independent synthetic tyrosine kinase-specific substrates, the polymer Poly(Glu:Tyr; 4:1) and the peptide substrate Raytide. In contrast, Protein Kinase C-specific activity was unaffected by PM-exposure. It is possible that inhibition was due to metabolites of PM, perhaps PMPs, rather than to PM itself. Whether the inhibition of tyrosine kinase activity observed with the substrates used in this study is equally applicable to all tyrosine kinases, is not yet clear. Nevertheless, low-dose PM could provide a useful tool for dissecting out the role of tyrosine phosphorylation in the regulation and dysregulation of cell growth, and could conceivably prove beneficial in the treatment of tumours in which tyrosine kinase overactivity is linked to oncogenesis.