Expression of Pit-1 mRNA and activin/inhibin subunits in clinically nonfunctioning pituitary adenomas. In situ hybridization and immunohistochemical analysis.
Pit-1 is a transcription factor which has been reported to regulate differentiation toward GH,PRL and TSH in the anterior pituitary glands. In the human pituitary adenomas, Pit-1 is highly expressed in GH secreting and TSH secreting adenomas as it can well be anticipated. Interestingly, human non-functioning pituitary adenomas also express Pit-1, especially it was expressed in all aSU positive nonfunctioning adenomas. The human anterior pituitary cells are special in comparison with rodents in a finding that aSU is frequently colocalized with GH. As aSU is the first hormone appearing during fetal development in the rodent pituitary glands, it may be postulated that aSU Pit-1 positive cells undergo differentiation in the GH cell lineage. From this background, this paper proposes that “aSU positive Pit-1 Positive” cells are the ones in the GH cell lineage, more specifically a dedifferentiated cell lineage toward