Currently, we are testing a series of cellular markers for human gastric cancer stem cells (CD44, CD24, CD133, ESA, ALDH1, etc.)and using human primary gastric cancer tissues to identify the true side population of the assumed gastric cancer stem cells, and to delineate the role of miR-34 in these tumor-initiating cells. The gene discussed is ALDH1A1; the disease is gastric cancer.