Stem cells have the unique ability to develop into different types of tissue cells in the human body, and are often involved in the onset of cancer, especially leukemia. Like other cells in the body, stem cells activate a diverse family of proteins that pump different substances in and out of cells, called ABC transporters. In normal cells, these proteins pump toxic substances out and useful ones in. But some of these proteins also pump anti-cancer drugs out of cancer cells, causing the treatment to fail. Maria Ho is researching how ABC transporters in stem cells can cause drug resistance in leukemia. Maria is measuring the level of ABC transporters in chemo-refractory and responsive leukemic stem cells to determine which transporters are required for normal functions and which ones are related to cancer. This research will help explain the course of the disease and lead to more effective cancer treatments to target the transporters involved in leukemia.