Endosialin­expressing bone sarcoma stem­like cells are highly tumor­initiating and invasive.

It has been reported that the presence of a small group of cancer stem­like 'side population (SP)' cells is responsible for therapy failure and tumor recurrence. The present study demonstrated that primary human osteosarcoma samples contained a SP of about 3.9% which overexpressed ABC transporters, including ABCA1, ABCB1, ABCB2 and ABCG2, which are associated with drug resistance and may have contributed to multi­drug resistance of SP cells. Furthermore, these SP cells displayed increased expression of endosialin (CD248) and other stem cell surface proteins, including CD133, octamer­binding transcription factor 3/4A, Nanog and Nestin, which are ultimately responsible for high self­renewal and deregulated cell proliferation. In addition, it was shown that endosialin­overexpressing SP cells were able to regenerate the tumor population and had a high invasive potential. Therefore, the present study suggested that osteosarcoma SP cells were cancer stem cells, as they displayed stem­like properties; furthermore, endosialin may be a potential target to prevent osteosarcoma recurrence following chemotherapy.