Expression of a new human THY-1 related antigen in Ewing's sarcoma and peripheral neuroectodermal tumors

Ewing's sarcoma (ES), peripheral neuroectodermal tumor (PNET) and Askin's tumor of the chest wall share a reciprocal chromosomal translocation between the long arms of chromosomes 11 and 22 (q23-24; q12). In the absence of other distinguishing features this specific translocation is regarded as marker of a common and neuroectodermal origin for these rare tumors. A monoclonal antibody (HBA-71) developed in our laboratory has been found to recognize an unique ES and PNET associated antigen, which is also expressed in some normal tissues, including thymus, bone marrow, islets of Langerhans, ependyma and adenohypophysis. It is shown in this study that this HBA-71 antigen is closely related to the murine THY-1 antigens, major cell surface glycoproteins of thymocytes and brain in mice and rat. Both antigens have similar molecular ratios (18,000), amino acid compositions and sensitivity to tryptic digestion, show high cell surface expression, and binding of the appropriate antibodies to HBA-71 antigen triggers proliferation in thymocytes. The HBA-71 epitope may represent a primitive neuroectodermal marker of ES/PNET, or its expression may be directly linked to the reciprocal translocation invariably associated with HBA-71-positive ES and PNET tumors, which maps to the same region of chromosome 11 (q23-24) as the human Thy-1 gene.