Non-responsiveness and toxicity are large problems encountered during cancer treatment. Utilization of compounds that synergize should increase treatment efficacy while avoiding problems of toxicity. This review explores interactions between classes of compounds, including anti-estrogens, retinoids, monoterpenes and tyrosine kinase inhibitors, that are effective independent, and how their synergistic interaction could be exploited in cancer treatment. The effects of these compounds on insulin-like growth factors (IGF) and transforming-growth factor-beta (TGF-beta) will also be examined.