Different subpopulations of cancer stem cells have been identified in pancreatic ductal adenocarcinoma, based on the use of a combination of surface markers, such as CD44, CD24, EpCAM (Epithelial Cell Adhesion Molecule), also known as ESA (Epithelial Cell Surface Antigen), CD326, CD133 and others, such as side population (SP) cells with overexpression of ABCG2 transporters and CXCR4. The gene discussed is CD44; the disease is cancer.