KIT and Ewing sarcoma: Although some gene array and immunohistochemistry studies in tumor tissues of patients with STS have revealed that certain TK receptors (e.g., KIT, PDGFβ) are overexpressed [28], [29], at present it is still unclear whether TK inhibitors as single agents or combined with conventional chemotherapy are effective on cellular models of STS others than GIST [30] and Ewing tumor cells [31].