Tyrosine kinase inhibitors and signal transduction modulators: Rationale and current status as chemopreventive agents for prostate cancer.

Cell growth and differentiation are processes intimately associated with carcinogenesis and regulated by tyrosine kinases and other signaling proteins. Identification of drugs that target signaling molecules is hampered by both the large number of targets and the complex nature of signaling cascades. Optimal development of chemopreventive agents must take into account affinity for the target, pharmacology, and safety profile of the agent. Validated biomarkers will allow the optimal implementation of chemopreventive trials. Directed epidemiologic studies can lead to the identification of lead compounds for chemoprevention, such as genistein. Therefore, agents targeted to pathways and molecules of known biological importance in the prostate hold the promise of clinical efficacy against prostate cancer in a chemopreventive setting.