THU044 The Subcellular Localization Of β-Catenin Is Associated With Tumor Size And The Surgical Remission Rate In Growth Hormone-producing Pituitary Adenomas

Disclosure: S. Kuwabara: None. H. Kameda: None. H. Nomoto: None. K. Cho: None. A. Nakamura: None. Y. Ishi: None. H. Motegi: None. F. Miki: None. H. Miyoshi: None. T. Atsumi: None. The Wnt/β-catenin pathway is the best understood Wnt signaling pathway and controls cell proliferation. In the presence of Wnt, the translocation of β-catenin from the cytoplasm to the nucleus leads to pathway activation. It has been reported that the nuclear accumulation of β-catenin is associated with Ki-67 expression in pituitary adenomas and that the invasiveness of growth hormone (GH)-producing pituitary adenomas is associated with β-catenin expression. We aimed to clarify the effects of the Wnt/β-catenin pathway in GH-producing pituitary adenomas. We performed immunofluorescence staining using antibodies against GH and β-catenin in pathological samples of pituitary adenoma from 62 patients with acromegaly who underwent pituitary surgery at our hospital between January 2008 and December 2021. We also obtained clinical data for the patients, including the results of endocrine testing, and evaluated the relationships of key indices with the intracellular localization of β-catenin. Samples from 26 cases (42%) showed strong punctate expression of β-catenin in the nuclei (dot pattern (DP) group), and samples from 36 cases (58%) showed β-catenin expression in the cytoplasm or cell membrane (non-DP group). There were no differences in the sex, age, GH concentration, or insulin-like growth factor I (IGF-1) SD scores of the two groups, but the DP group had larger tumors (diameters 18±8 vs. 13±7 mm) and a higher prevalence of macroadenomas (77% vs. 53%). In the DP group, a paradoxical preoperative GH response (an increase of ≥30% of the basal concentration) to 75-g oral glucose tolerance testing was more frequent (46 vs. 22%, p<0.05) and postoperative remission was less frequent (23% vs. 50%, p<0.05). Accordingly, the Wnt/β-catenin pathway appears to be more active in the DP group. The larger tumors and lower postoperative remission rate of the DP group suggest that the Wnt/β-catenin pathway may influence tumor growth. Wnt/β-catenin pathway could play a major role in GH-producing pituitary tumor growth, therefore this pathway would be a potential therapeutic target in the affected patients. Presentation: Thursday, June 15, 2023