Transcriptional regulation of phenylethanolamine N-methyltransferase in pheochromocytomas from patients with von Hippel-Lindau syndrome and multiple endocrine neoplasia type 2.

Pheochromocytomas in multiple endocrine neoplasia type 2 (MEN-2) express phenylethanolamine N-methyltransferase (PNMT), the enzyme that catalyzes conversion of norepinephrine to epinephrine, whereas those in von Hippel-Lindau (VHL) syndrome do not. Consequently, pheochromocytomas in MEN-2 produce epinephrine, whereas those in VHL syndrome produce mainly norepinephrine. This study examined whether transcription factors known to regulate expression of PNMT explain the different tumor phenotypes in these syndromes. Quantitative polymerase chain reaction (PCR) and Western blotting were used to assess levels of mRNA and protein for the glucocorticoid receptor, early growth response 1 (Egr-1), the Sp1 transcription factor (Sp1), and MYC-associated zinc finger protein (MAZ) in 6 MEN-2 and 13 VHL tumors. Results were cross-checked with data obtained using microarray gene expression profiling in a further set of 10 MEN-2 and 12 VHL tumors. Pheochromocytomas in MEN-2 and VHL syndrome did not differ in expression of the glucocorticoid receptor, Egr-1, Sp1, or MAZ as assessed by quantitative PCR and Western blotting. Microarray data also indicated no relevant differences in expression of the glucocorticoid receptor, Egr-1, MAZ, and the AP2 transcription factor. Thus, our results do not support a role for the above transcription factors in determining differences in expression of PNMT in pheochromocytomas from patients with VHL syndrome and MEN-2. Microarray analysis, however, did indicate differences in expression of genes involved in neural crest cell lineage and chromaffin cell development, consistent with differential survival of PNMT-expressing cells in the two syndromes.