Stem cells in Barrett's esophagus: HALOs or horns?

摘要

Recent concepts regarding the role of stem cells in cancer have interesting implications for endoscopists intent on ablating neoplasia in Barrett's esophagus. For years, the prevailing concept of carcinogenesis has been that cancer develops through a sequence of mutations that enable an affected cell to generate autonomous growth signals and to replicate while avoiding signals that might inhibit proliferation or trigger apoptosis. As a result of the unregulated proliferation of this advantaged clone, masses of neo-plastic cells accumulate and form solid tumors. Epithelial tumors comprise a heterogeneous population of neoplastic cells, however, and such tumors can be considered abnormal organs. It is not clear how an entire abnormal organ can develop from a single epithelial-cell clone. Within a malignant tumor, furthermore, only a small minority of the cells are capable of sustaining the cancer and of proliferating elsewhere in the body. Those observations led to the concept that malignancies develop from a small number of cancer stem cells that perpetuate themselves through self renewal and that give rise to a variety of more differentiated neoplastic-cell types, most of which are incapable of forming new tumors#