HIGH-LEVELS OF EXPRESSION OF NEUROPEPTIDE-Y MESSENGER-RNA IN HUMAN PHEOCHROMOCYTOMAS

1. Neuropeptide Y (NPY) gene expression in human phaeochromocytomas wa s investigated by measuring the levels of NPY mRNA and NPY-immunoreact ivity (NPY-IR) in human phaeochromocytoma tissues in comparison with t hose in normal human adrenal tissues. 2. The amounts of NPY mRNA and N PY-IR in human phaeochromocytomas were 18 and 93 times higher, respect ively, than those in normal adrenal glands. In contrast, beta-actin ge ne expression was similar in human phaeochromocytomas to that in norma l adrenal glands. 3. The amount of NPY mRNA relative to total cellular RNA was 6-fold higher in phaeochromocytoma tissues than in normal hum an adrenal medulla, suggesting increased NPY gene expression in the tu mour cells. 4. Induction of differentiation of PC12 rat phaeochromocyt oma cells by compounds, such as dexamethasone and nerve growth factor, resulted in a marked increase in the NPY mRNA level. 5. These finding s suggest that NPY gene expression is increased in well-differentiated human phaeochromocytoma cells. Its high level of expression could be responsible for the marked overproduction of NPY by this tumour.