ILK (BETA-1-INTEGRIN-LINKED PROTEIN-KINASE) - A NOVEL IMMUNOHISTOCHEMICAL MARKER FOR EWINGS-SARCOMA AND PRIMITIVE NEUROECTODERMAL TUMOR

ILK (beta 1-integrin-linked protein kinase) is a recently identified 5 9-kDa serine/threonine protein kinase that interacts with the cytoplas mic domain of the beta 1-integrin containing four ankyrin-like repeats . We have developed a polyclonal antibody against ILK and explored the ILK immunoreactivity in normal human cells and tissues. ILK was mainl y expressed in cardiac muscle and skeletal muscles. Surprisingly, ILK expression was observed in Ewing's sarcoma (ES; 100%), primitive neuro ectodermal tumour (PNET; 100%),,medulloblastoma (100%), and neuroblast oma (33.3%), whereas other small round cell sarcomas were not stained by the anti-ILK antibody. These results suggest that ILK could be a no vel marker for tumours with primitive neural differentiation. Our find ings support the notion that ES is a tumour that is closely related to PNET and that both originate from the neuroectoderm. ILK may be a sen sitive and specific immunohistochemical marker and useful for the posi tive identification of ES and PNET in formalin-fixed, paraffin-embedde d tissue sections.