EWS-FLI1-induced osteosarcoma model unveiled a crucial role of impaired osteogenic differentiation on osteosarcoma development [ChIP-seq]

EWS-FLI1, a multi-functional fusion oncogene, is exclusively detectable in Ewing sarcomas. However, previous studies reported that a subset of osteosarcomas also harbor EWS-ETS family fusion, suggesting that the fusion gene may be involved in the development of a particular type of osteosarcomas. Here using the doxycycline inducible EWS-FLI1 system, we established an EWS-FLI1-dependent osteosarcoma model from murine bone marrow stromal cells. We revealed that the withdrawal of EWS-FLI1 expression enhances the osteogenic differentiation of sarcoma cells, leading to mature bone formation. Taking advantage of induced pluripotent stem cell (iPSC) technology, we also showed that the sarcoma-derived iPSCs with cancer-related genetic abnormalities exhibited the impaired differentiation program of osteogenic lineage irrespective of the EWS-FLI1 expression. Finally, we demonstrated that EWS-FLI1 contributed to in vitro sarcoma development from the sarcoma-iPSCs after osteogenic differentiation. These findings demonstrated that modulating cellular differentiation is fundamental principle of the EWS-FLI1-induced osteosarcoma development. Furthermore, the in vitro cancer model using sarcoma-iPSCs should provide a novel platform for dissecting relationship between cancer genome and cellular differentiation.