Differential expression of the neural cell adhesion molecule NCAM 140 in human pituitary tumors

We have analyzed the expression of the intracellular marker protein
neuron specific enolase (NSE), synaptophysin (SYN) and of the cell
surface marker NCAM (neural cell adhesion molecule) in both normal
human hypophysis and in pituitary adenomas in order to explore
their potential use as diagnostic tools. All adenomas (4
prolactinomas, 3 growth hormone (GH) producing adenomas and 4
inactive adenomas) showed SYN and NSE immunoreactivity on tissue
sections and this was confirmed by immunoblots. NCAM 140 (an
isoform of NCAM with molecular mass 140 kDa) was detected by
immunoblotting in normal human adenohypophysis, in all GH adenomas,
and in three out of four inactive adenomas, but not in
prolactinomas. Using highly sensitive techniques, NCAM
immunoreactivity was observed by electron microscopy in all
adenomas. These data indicate that NCAM 140 is a constituent of the
cell surface of endocrine cells in both normal human
adenohypophysis and its tumors. Since prolactinomas express very
low levels of NCAM 140 compared to other hypophyseal tumors its
virtual absence could be used for differential diagnosis. A
combined analysis of NCAM, SYN and NSE could be useful to
characterize inactive adenomas which are not immunoreactive for
pituitary hormones and which may contain no or only low levels of
the alpha chain of the glycoprotein hormones.