Abundant but Inactive-state gpl40prototrkIs Expressed in Neuroblastomas of Patients with Good Prognosis

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Abstract
Steady‐state levels of gp140proto‐trk in cell lines and tumor tissues of neurohlastoma were examined by immunoblotting with anti‐gpl40proto‐trk The level of gpl40proto‐trk varied but showed good correlations with the stage of the tumor and the age of the patients at the time of diagnosis. Moreover, patients with higher expression of gpl40proto‐trk clearly had a far better survival rate than those with lower expression, suggesting that suppression of gp140proto‐trkstrongly correlates with the malignant conversion of the tumor. However, we found that neither autophosphorylation of gpl40proto‐trknor tyrosine phosphoryla‐tion of cellular proteins was elevated in tumors of the higher expression group. These results suggest that gpl40proto‐trk does not actively participate in the process of transformation or the suppression of malignant conversion. Rather, the higher level of gpl40proto‐trkmay reflect the greater level of differentiation of tumor cells.