Stem cells & pancreatic cancer.

It is now well established that human pancreatic ductal adenocarcinoma (PDAC) contains a subset of cells with self-renewal capabilities and subsequent exclusive in vivo tumorigenic capacity as assessed by limiting dilution tumorigenic transplantation assays into immunodeficient mice. These cells are considered pancreatic cancer stem cells (CSCs) and are able to form tumors indistinguishable from parental ones. Furthermore they display strong chemotherapy resistance and are implicated in tumor relapses and metastatic spread. Important next steps for advancing the field of pancreatic CSC research include the identification and characterization of CSCs in the unperturbed in vivo setting. This has been achieved just recently for other solid tumors such as glioblastoma using clonal analysis after lineage tracing in mice [1]. In vivo imaging of CSCs during tumor development should not only provide new insights into the in vivo features of CSCs, but also help to further unravel the influence of the stroma on CSC biology. Comprehensive studies of the tumor heterogeneity with respect to the coexistence of different clones potentially generated by distinct population of CSCs that are evolving by stochastic cell fate decisions may actually unite the CSC concept and the model of clonal evolution for pancreatic cancer. Eventually, the design of specific therapies against CSCs should open new alleys to improve survival of patients with PDAC. Combined therapies targeting CSCs and their progenies as well as the supportive stroma may represent the most promising approach for the future treatment of patients with PDAC.