Many studies have demonstrated that most cancers are clonal and are maintained by a cancer stem cell. Cancer stem cells have been identified in blood, breast, brain, lungs, gastrointestinal, prostate and ovarian cancer. Under normal homeostasis tissue specific stem cell division would be under strict control. When proliferation becomes independent of normal cellular controls, cancer develops. Studies indicate that cancer stem cells maintain their ability to differentiate, which explains the variety of cell types observed in tumors. Most therapies are directed at the fast growing tumor mass but not the slow dividing cancer stem cells and therefore the cancer is not eradicated. Understanding the process of transformation from a highly regulated stem cell to a cancer stem cell requires an understanding of genetic and epigenetic processes as well as having an understanding of the stem cell niche and the interaction of the stem cells with supportive cells in the niche. Current research is helping us to understand stem cells and stem cell regulation and in turn this will help to develop novel therapies to eliminate cancer and the initiating cancer stem cell. The relevant patents on the stem cell regulation and cancer therapy by stem cells are discussed.