Therapeutic Action of Phytochemicals on Cancer Stem Cells

The cancer stem cell (CSC) concept has important implications not only for our understanding of carcinogenesis, but also for the development of cancer therapeutics. There is a growing body of preclinical evidence that cancer stem cells contribute to chemotherapy and radiation resistance in breast cancer. The use of drugs that interfere with stem cell self-renewal represents the strategy of choice, but also a great challenge because cancer stem cells and their normal counterparts share many pathways. Dietary compounds have been used in cancer prevention for decades, and some of these compounds target specific mechanisms that control CSC self-renewal. However, to date, no significant impact of CSCs on clinical outcome has been identified. The new paradigm imposed by the CSC model may change the way therapeutic effects are measured in clinical trials, stressing the effect on overall survival over just rapid tumor size reduction. In this chapter, we present the concept of cancer stem cell, mechanisms of conventional anticancer treatment resistance, and how dietary compounds may be used to target the self-renewal capability of CSCs.