Contribution of PROP1 in the pathogenesis of Cushing’s disease: A preliminary study

Abstract

Prophet of Pit1 (PROP1) is the pituitary specific transcription factor which was cloned as an upstream regulator of PIT1. Cushing’s disease is caused by corticotroph adenomas which does not belong to the PIT1 lineage. The aim of this study was to elucidate the involvement of PROP1 in the pathogenesis of Cushing’s disease. Since it is difficult to accurately evaluate PROP1 expression in pituitary adenomas by RT-PCR analysis due to the inevitable contamination of surgical tissue specimens with normal pituitary cells, we examined six corticotroph adenomas by immunohistochemistry. Adenomas were classified into 2 subtypes based on their staining patterns of CAM5.2: diffuse and non-diffuse types. It is likely that diffuse-type adenomas are composed of more differentiated tumor cells. PROP1 was positive in all three cases of non-diffuse-type adenomas, but negative in all three cases of diffuse-type adenomas, suggesting that PROP1 was prominently expressed in less differentiated non-PIT1 lineage corticotroph adenomas. This study is the first report to analyze PROP1 expression in pituitary adenomas by immunohistochemistry. PROP1 may have a role in tumorigenesis of pituitary adenomas in Cushing’s disease, and is expected to be a new therapeutic target for refractory pituitary adenomas.