Chromogranin A (CGA) is a major secretory protein present in the soluble matrix of chromaffin granules of neuroendocrine cells and tumours, such as phaeochromocytomas. CCA has several functions, some of which may be involved in the distinct phenotypic differences of phaeochromocytomas in patients with von Hippel-Lindau (VHL) syndrome compared to multiple endocrine neoplasia type 2 (MEN 2). In this study, we therefore compared tumour and plasma levels of CGA in patients with phaeochromocytoma associated with the two syndromes. We show that phaeochromocytomas from MEN 2 patients express substantially more CCA than tumours from VHL patients at both the mRNA (3-fold greater) and protein (20-fold) level. We further show that relative to increases in plasma catecholamines, patients with phaeochromocytomas associated with MEN 2 have higher plasma concentrations of CCA than those with tumours in VHL syndrome. These data supplement other observations that phaeochromocytomas in VHL compared to MEN 2 patients express lower amounts of catecholamines and other chromaffin granule cargo, such as chromogranin B and neuropeptide Y. Possibly the differences in tumour CCA expression may contribute to differences in secretory vesicle formation and secretion in the two types of tumours. Alternatively the differences in expression in CGA and other secretory constituents may reflect downregulation of the entire regulated secretory pathway in VHL compared to MEN 2 tumours.
- Chromaffin cells