PROGNOSTIC VALUE OF TRKA PROTEIN-DETECTION BY MONOCLONAL-ANTIBODY 5C3IN NEUROBLASTOMA

The effects of nerve growth factor, a neurotrophin mediating growth an d differentiation of neural crest-derived cells, are mediated by the r eceptor TrkA, TrkA mRNA expression has been associated with a good pro gnosis in human neuroblastoma (NB), We describe the use of monoclonal antibody 5C3 in detecting TrkA expression by immunohistochemistry in N E and other malignant tumors, A murine anti-TrkA IgG(1) monoclonal ant ibody, 5C3, was generated against the extracellular domain of human p1 40(TrkA), 5C3 detected a 140-kDa band on Western blots, 5C3 was optimi zed for immunostaining and used to detect p140(TrkA) on 113 frozen NE samples and 42 samples from nine other malignancies, MOPC21 IgG(1) ant ibody was used as a control, Results by immunohistochemistry were comp ared to TrkA expression assessed by reverse transcription-PCR and West ern analysis. The prognostic value of TrkA expression by these methods was evaluated and compared to other known prognostic variables, inclu ding stage, age, and MYCN copy number, TrkA expression was detected by immunohistochemistry in 73 of the 113 NE tumor specimens and strongly correlated with nonmetastatic disease. TrkA expression was specific f or NE among small round blue cell tumors, Both TrkA expression by immu nohistochemistry and localized/4s disease correlated with survival, Tu mors from 55 of 60 patients with localized/4s NE exhibited homogeneous or a mixed pattern of TrkA immunohistochemistry, whereas only 18 of 5 3 patients with stage 4 NE were immunoreactive. Detection of TrkA by r everse transcription-PCR and Western analysis was much more sensitive and no longer correlated with survival, 5C3 enables rapid detection of p140(TrkA) by immunohistochemistry and identifies patients more likel y to have localized NB with a favorable clinical outcome, Lack of TrkA expression is correlated with metastatic, malignant NE. A subset of p atients with NE, however, died of aggressive metastatic disease despit e TrkA expression, As a mimic of nerve growth factor, 5C3 may be usefu l in the study of TrkA-expressing tumors.