Cancer Chemoprevention*

Abstract

Cancer chemoprevention is the use of natural or synthetic compounds to prevent, suppress, or reverse the development of invasive carcinoma. Thus, the goal of chemoprevention is to reduce the occurrence of cancer by inhibiting or inducing key critical pathways that play a role in the carcinogenesis process. The progression toward invasive cancer is characterized by the accumulation of mutations and increased proliferation. Because carcinogenesis is a multistage process and often has a latency of many years or decades, there is considerable opportunity for intervention. Various studies have shown that chemopreventive agents possess strong cancer-protective properties that might interrupt the carcinogenesis process by interfering at the initiation, promotion, and progression stages of cancer. They might also lead to the modulation of proteins in diverse pathways and require the integration of different signals for the final chemopreventive and/or therapeutic effect. Compounds classified as blocking agents prevent carcinogens from reaching or reacting with critical target sites and suppressing agents prevent the evolution of the neoplastic process. Blocking mechanisms include alteration of drug metabolizing activities and scavenging of reactive oxygen species. Mechanisms that suppress tumorigenesis often involve modulation of signal transduction pathways, leading to altered gene expression, cell cycle arrest, and apoptosis. In this chapter, we summarize the current knowledge on dietary cancer-chemopreventive compounds, their induction of detoxifying enzymes, and effects on cellular-signaling events.