Immunohistochemical analysis of filamin a expression in acromegaly and its correlation with tumor characteristics and treatment response

Acromegaly, caused by growth hormone-secreting pituitary tumors, often causes significant challenges in its management due to poor surgical outcomes and resistance to pharmacological treatment. The present study aims to explore the expression of Filamin A (FLNA), a cytoskeletal protein involved in somatostatin receptor signaling, and its clinical relevance in acromegaly. We conducted immunohistochemical (IHC) study on 34 GH-secreting pituitary tumors to evaluate FLNA expression intensity and its associations with somatostatin receptors (SSTR2, SSTR5), E-Cadherin, tumor characteristics obtained through imaging studies, and pharmacological treatment responses. Our findings revealed a 100% FLNA positivity rate, with moderate to strong FLNA expression correlating significantly with SSTR5 expression and the presence of suprasellar tumor extension, indicating a potential role in tumor invasiveness. Moreover, patients with macrodenomas presented significantly higher FLNA intensity compared to the ones with microadenomas. FLNA expression showed no significant association with SSTR2, E-Cadherin, surgical cure rate or first-generation somatostatin receptor ligand (fgSRL) responses. However, the series of patients treated with Pasireotide (n = 4) demonstrated a trend suggesting better biochemical control with higher FLNA expression. In conclusion, our results suggest that FLNA may be associated with tumor invasiveness in GH-secreting pituitary tumors. While data on Pasireotide-treated patients are exploratory, further studies are needed to assess FLNA's potential as a treatment response marker in acromegaly.