Multiple defects of the nerve growth factor receptor in human neuroblastomas

Abstract

We hypothesized that defects in the nerve growth factor receptor (NGFR) pathway may play a role in maintenance of the undifferentiated state of neuroblastomas. To test this hypothesis, we examined the structure and function of the NGFR in a panel of 10 neuroblastoma cell lines. Southern blot analysis showed that all 10 cell lines possess apparently normal NGFR genes. Northern blot and ligand binding/immunoprecipitation assays revealed four receptor-positive cell lines (NGP, NLF, SK-N-SH and, LA-N-6), with NGFR mRNA and protein of expected sizes (3.8 kb and approximately 75 kD respectively). NGF binding assays and Scatchard analyses were performed on these four lines. The NGP line possesses only low affinity receptor (Kd approximately 3.5 x 10(-9] while the other three lines express both low- and high-affinity forms (Kd approximately 10(-9) and Kd approximately 10(-11), respectively). However, none of the 10 lines exhibited an early or late response to NGF treatment as assayed by c-fos mRNA induction (45 min) and neurite extension (8-10 days). These results demonstrate at least three distinct defects in the NGFR pathway in these tumor lines: 1) absence of NGFR mRNA or protein expression, 2) expression of only low-affinity receptor, and 3) inability of high affinity receptor to mediate a response to NGF. Such defects may play an important role in the initiation or maintenance of the undifferentiated state of neuroblastoma.