Endometrial Cancer Stem Cells: Are They a Possible Therapeutic Target?

The dynamic regeneration of the human endometrium during the menstrual cycle is thought to be supported by a specialized cell population, probably residing in the basal layer, which continues to provide daughter cells with high proliferative potential. This cell population is assumed to have stem cell characteristics. Recent molecular studies have revealed the presence of putative epithelial and stromal stem cells in the endometrium. A cell population with stem cell characteristics also has been identified in malignant tumors and is known as cancer stem cells (CSC). Putative CSCs are prospectively isolated using methods based on either a surface marker or intracellular enzyme activity and then assessed by serial transplantation of sorted subpopulations of tumor cells into immunocompromised mice. Unlike many other tumor types, little information on the characteristics of CSCs in endometrial cancer is available. We and others have demonstrated that prospectively isolated CD133(+) cells and/or side population cells in endometrial cancer are capable of initiating tumor formation in immunocompromised mice and recapitulating the phenotype of the original tumor and, therefore, are potential endometrial CSCs. This review summarizes key elements of our understanding of the normal endometrial stem cells and endometrial CSCs and further discusses a potential strategy to target endometrial CSCs in cancer therapy.