ABUNDANT BUT INACTIVE-STATE GP140(PROTO-TRK) IS EXPRESSED IN NEUROBLASTOMAS OF PATIENTS WITH GOOD PROGNOSIS

Steady state levels of gp140(proto-trk) in cell lines and tumor tissue s of neuroblastoma were examined by immunoblotting with anti-gp140(pro to-trk). The level of gp140(proto-trk) varied but showed good correlat ions with the stage of the tumor and the age of the patients at the ti me of diagnosis. Moreover, patients with higher expression of gp140(pr oto-trk) clearly had a far better survival rate than those with lower expression, suggesting that suppression of gp140(proto-trk) strongly c orrelates with the malignant conversion of the tumor. However, we foun d that neither autophosphorylation of gp140(proto-trk) nor tyrosine ph osphorylation of cellular proteins was elevated in tumors of the highe r expression group. These results suggest that gp140(proto-trk) does n ot actively participate in the process of transformation or the suppre ssion of malignant conversion. Rather, the higher level of gp140(proto -trk) may reflect the greater level of differentiation of tumor cells.