Targeted cancer therapy: promise and reality.

Signal transduction therapy for cancer targets specific molecular elements that are essential for survival of the tumor. Gleevec has a profound effect on early phase chronic myeloid leukemia because it inhibits the major driving factor of the tumor, BCR-ABL. Almost all other cancers depend on several factors, and blocking a single signal transduction factor is largely ineffective. Effective signal transduction therapy will entail finding the appropriate combination of signal transduction inhibitors for each cancer. We discuss the use of preclinical animal models to predict successful signal transduction therapy in the clinic, and conclude that their utility is limited.