Protein-tyrosine kinase inhibition: mechanism-based discovery of antitumor agents.

Protein-tyrosine kinases (PTKs) have been shown to induce the cascade of altered cell parameters characteristic of transformed cells. This proposition provides an important rationale for the discovery of potential antitumor agents from natural sources on the basis of inhibition of PTK activity. Numerous naturally occurring and synthetic analogues of PTK inhibitors were systematically evaluated in this review based on their structure-activity relationships and potential antitumor efficacy.