EXPRESSION OF NOR-1 AND ITS CLOSELY-RELATED MEMBERS OF THE STEROID THYROID-HORMONE RECEPTOR SUPERFAMILY IN HUMAN NEUROBLASTOMA CELL-LINES

Previously, we isolated a cDNA of neuron derived orphan receptor (NOR-1), a putative transcription factor with strong homologies to the orphan nuclear receptors NGFI-B and NURR1. In the present study, we examined the gene expression of NOR-1 as well as NGFI-B and NURR1 in human neuroblastoma cell lines by reverse transcription-polymerase chain reaction and nucleotide sequencing. Although the mRNAs of these orphan receptors were detected in all six neuroblastoma cell lines examined, basal expression levels of these genes varied among cell lines. Treatment with forskolin and 12-O-tetradecanoylphorbol-13-acetate rapidly increased the expression of all these genes in neuroblastoma NB-OK-I cells. This induction did not require de novo protein synthesis, indicating that the NOR-I gene as well as NGFI-B and NURR1 genes is an immediate-early gene. This is the first demonstration of NOR-I gene expression in tumor cell lines.