This EurekAlert! release looks at some of the challenges facing the increasing number of research groups who are attempting to destroy cancer stem cells: "Many of the colon cancer cells that form tumors can be killed by genetically short-circuiting the cells' ability to absorb a key nutrient, a new study has found. While the findings are encouraging, the test tube study using human colon cancer cells also illustrates the difficulty of defeating these cells, known as cancer stem cells (CSCs). ... It is becoming more evident that only a small number of cells in the tumor are capable of forming the tumor, namely the cancer stem cell. So the new strategy is to eliminate the cancer stem cells and thus lower the recurrence of cancer. ... Because CSCs have properties similar to normal stem cells, we have to find a way to attack them while keeping the adult stem cells alive. ... To do that, the research team inactivated a receptor that is found in increased amounts in colon cancer cells: the insulin-like growth factor receptor (IGF-1R). The colon cancer CSCs seem to need a fair amount of IGF to live, more than other cells, and they can't function without the IGF receptor. ... Working with human colon cancer cells, the researchers manipulated the cellular genetics using small interfering RNA (siRNA) to prevent the synthesis of IGF-1R. In this way, they reduced the number of IGF receptors by half, and reduced the number of CSCs by 35%."