Pituitary adenomas are usually benign
neuroendocrine tumors. However, some of those that are histopathologically undistinguishable behave aggressively and metastasize. The polysialylated
neural cell adhesion molecule (
PSA-NCAM), which is highly expressed during the development of the brain and pituitary, is detected in some
neuroendocrine tumors and might be relevant as a prognostic marker in
pituitary tumors. In the present study, we have searched for
PSA-NCAM expression in four lineages of rat pituitary transplantable
tumors (SMtTW). Each lineage, maintained by serial
tumor grafts under the kidney
capsule and skin, differed in its GH/Prl secretion, growth rate, and malignant behavior.
PSA-NCAM expression, detected by immunohistochemistry and Western blotting and quantified by ELISA, varied according to the SMtTW lineage. The benign
tumors, SMtTW2, with a low growth rate never expressed
PSA-NCAM. Another benign lineage, SMtTW3, with a high growth rate expressed a low amount of
PSA-NCAM. The highest
PSA-NCAM expression was seen in
tumors that grew beneath the skin, invaded the kidney, and metastasized (SMtTW4).
Tumors of the SMtTW10 lineage, which behaved as either benign or malignant
tumors, were heterogeneous in terms of
PSA-NCAM expression. In this rat transplantable
pituitary tumor model,
PSA-NCAM expression correlated in decreasing order with: (a) invasiveness (P < 0.0001), (b)
metastases (P = 0.004), (c) ability to grow under the skin (P = 0.006), and (d) growth rate under the kidney
capsule (P < 0.01), but not with
hormone secretion (r = 0.207). This model, which is very similar to the human pathology, suggests that
PSA-NCAM evaluation is of interest in the diagnosis of
malignancy and the prognosis of human
pituitary tumors. In addition, the SMtTW
tumors could be instrumental in evaluating the effects of new therapeutic agents modulating
PSA-NCAM expression.