abstract
- The in vivo relationship between human tumor cells and interacting normal cells in their local environment is poorly understood. Here, using a uniquely developed in vitro co-culture system for human embryonic stem cells (hESCs), we examined the interactions between transformed and normal human stem cells. Co-culture of transformed-hESCs (t-hESCs) with normal hESCs led to enhanced self-renewal and niche independence in normal hESCs. Global gene expression analysis of normal hESCs after timed exposure to t-hESCs indicated a transition of the molecular network controlling the hESC state, which included epigenetic changes, towards neoplastic features. These included enhanced pluripotent marker expression and a differentiation blockade as major hallmark changes. Functional studies revealed a loss in normal terminal differentiation programs for both hematopoiesis and neural lineages after normal stem cell co-culture with transformed variants. This transmission of neoplastic properties from t-hESCs to normal hESCs was dependent on direct cell-cell contact. Our study indicates that normal human stem cells can co-opt neoplastic cancer stem cell properties, raising the possibility that assimilation of healthy cells towards neoplastic behavior maybe a contributing feature of sustained tumorigenesis in vivo.