HIGH NM23-H1/NDPK-A EXPRESSION IN EWING TUMORS - PARADOXICAL IMMUNOHISTOCHEMICAL REACTIVITY AND LACK OF PROGNOSTIC-SIGNIFICANCE

Expression of nm23-HI/NDPK-A has been reported to correlate inversely with metastasizing potential of rodent experimental cells and some human tumors. In the search for reliable molecular prognostic indicators for Ewing tumors (ET), a group of aggressive presumably neuroectodermal malignancies in children and adolescents, we studied nm23-HI/NDPK-A expression. Northern-blot and RT-PCR analyses were employed to semi-quantificatively measure nm23-HI mRNA levels in ET cell lines and tissue extracts. A panel of monoclonal antibodies (MAbs) were used to evaluate protein abundance by Western blotting and immunohistochemistry. The nm23-HI/NDPK-A gene was also investigated on the DNA level to define possible genomic alterations. Our results revealed neither nm23-HI allelic loss nor gene amplification and failed to show any significant variation in nm23-HI mRNA or NDPK-A protein levels of primary or metastatic ET. NDPK-A protein levels were high and comparable to those of MCF-7 breast-cancer cells and to aggressive stage-IV neuroblastoma cell lines. nm23-H2/NDPK-B expression in ET was slightly more variable but generally lower than in MCF-7 cells. In the immunohistochemical analysis, however, discrepancies in the reactivity patterns with different antibodies were observed. Differential sensitivity to various fixation methods and heat treatment painted to a structurally polymorphic NDPK-A protein. nm23-HI expression studies using immunohistochemistry for prognostic counselling should thus be interpreted with caution. (C) 1995 Wiley-Liss, Inc.