Transcriptional Regulation of Phenylethanolamine N‐Methyltransferase in Pheochromocytomas from Patients with von Hippel–Lindau Syndrome and Multiple Endocrine Neoplasia Type 2

Abstract

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.

DNA Methylation Profiling in Pheochromocytoma and Paraganglioma Reveals Diagnostic and Prognostic Markers

“…Our results verified PNMT hypermethylation previously reported in SDHBrelated PPGLs (2). PNMT hypomethylation in RET-and NF1-and hemimethylation in VHL-related PPGLs is highly consistent their associated neurochemical phenotypes (2,20,29). However, this model does not explain why other "cluster 1" tumors do not display an adrenergic phenotype, even when PNMT is hemimethylated.…”

GENETICS IN ENDOCRINOLOGY: The genetics of phaeochromocytoma: using clinical features to guide genetic testing

“…It was estimated that about 30% of sporadic aPCA and eFPGL have a similar gene expression signature to VHL/SDHX tumours and the other 70% to NF1/RET (53). Interestingly, the differences in gene expression profiles can be correlated with the tendency of VHL and SDHX tumours to produced mainly noradrenaline, and RET/NF1 tumours to be adrenergic (56). Recently, Burnichon et al (55) have demonstrated that the gene expression profiling can be used to identify which subset of sporadic tumours are likely to harbour somatic VHL or RET mutations and so provide a basis for potential personalised therapies.…”

Gene Expression Profiling of Benign and Malignant Pheochromocytoma

“…These findings fit with others indicating that familial pheochromocytomas develop by a single pathway linking mutations in disease-causing genes to failure of apoptosis after withdrawal of growth factors during chromaffin cell development. 14 As advanced elsewhere in this volume by Huynh et al, 15 epinephrine-producing tumors in MEN 2A are hypothesized to develop due to susceptibility of more fully developed PNMT-expressing chromaffin cells to the effects of activating RET mutations, whereas norepinephrine-producing pheochromocytomas in VHL syndrome develop from neural crest progenitors before their final development into differentiated epinephrine-producing adrenal chromaffin cells.…”