The histogenesis of
Ewing's sarcoma (ES), the second most frequent primary bone
tumor in humans, remains controversial. A new cell line (SIM-1) was derived from a
peripheral neuroectodermal tumor (
PNET) and used for the production of a
monoclonal antibody (HBA-71), which recognizes a novel
cell surface antigen of ES- and
PNET-derived cells and
paraffin-embedded
tumor sections. The HBA-71
antigen expression is restricted to
PNET/ES and the
antigen was not detected on cell lines or tissue sections of any other
tumor tested, with the exception of
ependymoma. Three
proteins with molecular weights of 300,000, 185,000, and 90,000 were isolated from SIM-1 membrane extracts by HBA-71 affinity chromatography.
Trypsin treatment of intact SIM-1 cells destroys the HBA-71
epitope and cleaves off two
proteins with molecular weights of 210,000 and 95,000. HBA-71
antigen expression is not influenced by treatment of ES cell lines with differentiation inducers. Within normal tissues reactivity was observed with the adenohypophysis, ependymal cells, endocrine pancreas, Sertoli, and ovary granulosa cells. The
reagent links ES with
PNET and provides a highly valuable probe for (a) the immunohistological differential diagnosis of ES/
PNET using fresh tissue or
paraffin sections from other small round cell
tumors, (b) the histogenetic studies of ES/
PNET, and (c) the in vivo diagnostic and therapeutic procedures in patients with ES and
PNET.