Current targets for anticancer drug discovery.

The call for the discovery of less toxic, more selective, and more effective agents to treat cancer has become more urgent. Inhibition of angiogenesis continues to be one of the main streams in the current cancer drug discovery activity. Insights into tumor angiogenesis biology have led to the identification of a number of molecules, which are important for the progression of these processes. Of particular interest is a group of growth factors including fibroblast growth factor, platelet-derived growth factor, and vascular endothelial growth factor. These growth factors and their corresponding receptor tyrosine kinases have become important targets for inhibition of the proliferation of endothelial cells, the main component of blood vessels. The validated targets for inhibition of angiogenesis also include a family of matrix metalloproteinases and cell adhesion molecules. In the closely related area, protein kinases have emerged as one of the most important targets for drug discovery. Besides growth factor receptor tyrosine kinases, numerous other protein kinases implicated in malignancies have been identified including non-receptor kinases such as Bcl-Abl and Src kinases. In addition, the cell cycle regulators (cyclin-dependent kinases, p21 gene) and apoptosis modulators (Bcl-2 oncoprotein, p53 tumor suppressor gene, survivin protein, etc) have also attracted renewed interest as potential targets for anticancer drug discovery. Other molecular targets include protein farnesyltransferase (FTase), histone deacetylase (HDAC), and telomerase, which have essential roles in cellular signal transduction pathways (FTase, HDAC) and cell life-span (telomerase). This review presents a comprehensive summary and discussion on the most important targets currently attracting a great deal of interest in contemporary anticancer drug design and discovery. Recent advances complementing these targets are also highlighted.