Monoclonal antibody to human Trk-A: diagnostic and therapeutic potential in neuroblastoma.

5C3 is a murine IgG1 antibody specific for the nerve growth factor (NGF) docking site of the human p140 trk-A receptor, with no cross-reactivity with human trk-B. In vitro, 5C3 and its Fab mimic the effects of NGF, a neurotrophin mediating growth and differentiation of neural crest-derived cells. When labelled with radioisotope, 5C3 images human trk-A positive tumours in vivo. More importantly, 5C3 induces regression of human trk-A positive tumours in rodents. We therefore investigated the value of 5C3 in detecting trk-A expression in human neuroblastoma by immunohistochemistry. 5C3 reactivity was detected in 73 of 113 neuroblastoma specimens and correlated strongly with localised/4s disease (55/60) with either a homogeneous or mixed pattern. Among stage 4 neuroblastoma, only 18/53 had homogeneous or mixed trk-A expression. 5C3 did not react with 46/48 other human malignancies, but was positive in 1 melanoma and 1 Wilms' tumour specimen. The prognostic, imaging and NGF-mimetic properties of antibody 5C3 and its derivatives may offer alternatives for the diagnosis and treatment of neuroblastoma.