CD9 and osteosarcoma: Yun et al. [256] established the implication of GRP75 in cancer stemness by demonstrating on malignant cells of different origins (carcinomas, osteosarcomas, melanoma) that GRP75 overexpression is positively correlated with the upregulation of cancer stemness markers, including ABCG2, OCT4, CD133, CD9, ALDH1, MRP1, and connexin.