CD117 and Stro-1 are MSC markers. They have been found to be preferentially expressed in spheres and doxorubicin-resistant osteosarcoma cells and CD117-Stro-1 double-positive OSCs have been identified in both human and murine osteosarcoma cells and were found to exhibit high degrees of multipotency, invasiveness, drug resistance and elevated levels of self-renewal and metastatic potential [27]. Furthermore, they were enriched in metastasis-associated marker CXCR4 and drug-resistance marker ABCG2 [27]. Adhikari et al. also showed them to be highly effective in forming transplantable tumors. In contrast, CD117-Stro-1 double-negative cells lacked this ability [27]. Several studies have confirmed these findings [35], [36] and [54], demonstrating the importance of CD117 and stro-1 as molecular markers for identifying and isolating OSCs in osteosarcoma. CD105 and CD44 have also been identified as effective MSC markers in osteosarcoma along with CD117 and stro-1 [10].