CD248 and osteosarcoma: In addition to targeting the tumor stroma, endosialin expression is upregulated in tumor cells of mesenchymal origin such as soft tissue sarcomas and osteosarcomas.58–60 Further studies will be required to establish if the optimal value of E3K CAR-T cells, whether for targeting the tumor stroma or endosialin+ tumors, will be in combination with other therapies.