Expression of TrkC in favorable human neuroblastomas.

Human neuroblastomas have been found to express the neurotrophin receptors TrkA and TrkB. Expression of TrkA correlates with favorable outcome, while expression of full-length TrkB is associated with unfavorable, more aggressive, N-myc amplified tumors. In this study we have determined the expression of TrkC in neuroblastoma primary tumors and cell lines. Using probes for the extracellular domain and the tyrosine kinase domain of human TrkC, we found by Northern analysis that TrkC mRNA is expressed in 14 of 55 (25%) tumors from a representative panel of neuroblastomas. A 14 kb transcript was detected by both probes, indicating that it would encode the full-length TrkC protein. A significant association was found between TrkC mRNA expression detected by Northern analysis and lower stage tumors [stage 1, 2, 4S, 11 of 30 (37%); vs stage 3, 4, 3 of 25 (12%), chi2 = 4.4, P < 0.04]. Only one of eight primary tumors with N-myc amplification had detectable TrkC mRNA expression and none of the eight neuroblastoma cell lines expressed TrkC by Northern analysis. Our results suggest that TrkC is involved in the biology of favorable neuroblastomas.