Expression of pituitary homeo box 1 (Ptx1) in human non-neoplastic pituitaries and pituitary adenomas

We investigated the localization of pituitary homeo box 1 (Ptx1) protein in five human non-neoplastic pituitaries and 73 of all types of pituitary ade nomas using immunohistochemistry, and the expression of Ptx1 messenger RNA (mRNA) in 18 representative pituitary adenomas using the reverse transcript ase polymerase chain reaction (RT-PCR) technique. By immunohistochemical an alysis, Ptx1 protein was extensively detected in the nuclei of normal human pituitary cells. Ptx1 was detected in 10/14 (71.4%) of growth hormone IGH) -secreting adenomas, 12/12 (100%) of prolactin (PRL)-secreting adenomas, 18 /20 (90%) of adrenocorticotropic hormone (ACTH)-secreting adenomas, 6/7 (85 .7%) of thyroid-stimulating hormone (TSH)-secreting adenomas, and 17/20 (85 %) of clinically non-functioning adenomas, including 9/10 (90%) of gonadotr opin-subunit-positive adenomas. Thus, there was no relationship between Ptx 1 expression and a particular type of pituitary adenomas. By RT-PCR analysi s, Ptx1 mRNA was expressed in all 18 cases of pituitary adenomas, including two cases negative for Ptx1 protein by immunohistochemistry. These results suggested that Ptx1 may be an universal transcription factor in both neopl astic and non-neoplastic conditions in human pituitaries, The synergistic a ction with other transcription factors may be speculated to determine the s pecific production of the anterior pituitary hormones.