Pancreatic cancer stem cells: new insights and perspectives.

Since the identification of self-renewing cells in the hematopoietic system several decades ago, stem cells have changed the way we study biology and medicine. Solid tumors contain a distinct subpopulation of cells that have stem cell characteristics and are exclusively responsible for tumorigenicity. This discovery has led to the development of the stem cell concept of cancer, which proposes that a subpopulation of self-renewing tumor cells, also termed cancer stem cells, is responsible for tumorigenesis and metastasis. This contrasts with the stochastic model of tumor development, which holds that all tumor cells are capable of tumor initiation. Different subpopulations of cancer stem cells have been identified in pancreatic ductal adenocarcinoma, based on the use of combinations of surface markers that allow their isolation, propagation, and further characterization. Importantly, cancer stem cells are not only capable of self-renewal and differentiation, but may also confer virulence via immune system evasion and multidrug resistance, and potentially via vasculogenic mimicry and transition to migratory and metastasizing derivatives. Therapeutic targeting of this subset of cells and the pathways defining their virulence holds great promise for the development of more effective strategies for the amelioration and eradication of this most lethal form of cancer.