Interactions of Retinoids and Transforming Growth Factor-Beta in the Chemoprevention of Cancer

Several years ago, we suggested that some new approaches are necessary if we intend to solve the problem of epithelial cancer in humans [1]. The conventional clinical approach that has been followed with most epithelial cancer has been to wait until the patient has invasive disease and then treat this disease with cytotoxic chemotherapy, surgery, or radiation. None of these modalities has been uniquely successful for the treatment of all types of epithelial cancer, in spite of some advances that have occurred. In the conventional approach to the disease, cancer is treated as if it were an entity that could be destroyed or removed, ignoring the evidence that cancer is a diffuse, evolutionary, developmental process [2]. What is called “cancer” in clinical incidence statistics is the process in its terminal stages; by this time many of the physiological controls that allow for orderly epithelial growth have been lost.