Expression of the pituitary transcription factor Ptx-1, but not that of the trans-activating factor Prop-1, is reduced in human corticotroph adenomasand is associated with decreased alpha-subunit secretion

We have studied the expression of the pituitary transcription factors Ptx-1 and Prop-1 in a series of 34 pituitary adenomas fully characterized for in vitro hormone secretion and histological staining. In studies involving ma mmalian cell lines, the pituitary transcription factor Ptx-1 has been shown to be a pituitary hormone panactivator, whereas more recent studies have s hown that it plays an important role in alpha-subunit gene expression. Its expression has not been examined previously in human pituitary adenomas cha racterized by in vitro hormone secretory profiles. Of the 34 pituitary aden omas studied, Ptx-l expression was reduced by more than 50% compared to tha t of the housekeeping gene human glyceraldehyde-3-phosphate dehydrogenase i n the 6 corticotroph adenomas, which also had significantly reduced alpha-s ubunit production (all 6 tumors secreting less than or equal to 0.5 ng/24 h ). Mutations of the pituitary transcription factor Prop-1, which is respons ible for the syndrome of Ames dwarfism in mice, are being increasingly reco gnized as a cause of combined pituitary hormone deficiency in humans, altho ugh ACTH deficiency has been described only once. Prop-1 expression was det ected in all 34 pituitary adenomas, including 6 corticotroph adenomas and 5 gonadotroph adenomas. The expression of Prop-1 has not been described prev iously in these cell phenotypes.