Preoperative Somatostatin Analogue Treatment Might Trigger Apoptosis and Autophagy in Tumor Tissues of Patients with Acromegaly: A Pilot Study

Abstract

To evaluate the effect of preoperative somatostatin analog (SRL) treatment on proteins associated with apoptosis and autophagy in patients with acromegaly and to determine factors correlating with these parameters. Ex-vivo tumor samples of 11 SRL-treated and 9 SRL-untreated patients were retrospectively included in the study. Apoptotic and autophagic proteins were determined via immunohistochemical staining and apoptosis was evaluated via in situ DNA end labeling (TUNEL). TUNEL, caspase-3, and ATG-5 immunopositivity was significantly increased (p<0.01, p=0.01, p=0.01, respectively), survivin and beclin-1 immunopositivity was significantly decreased (p=0.03, p=0.02, respectively) in SRL-treated patients as compared with SRL-untreated controls. Ki-67 index was decreased significantly in the SRL-treated group (p=0.01). Significant positive correlations were detected between TUNEL and caspase-3 immunopositivity (r=0.577, p<0.01), and between survivin and beclin-1 immunopositivity (r=0.503, p=0.03). Age at diagnosis, preoperative GH, IGF-1 levels, tumor size, and invasion status were not found to affect TUNEL positivity nor did they correlate with caspase-3, survivin, beclin-1, ATG-5 immunopositivity (p>0.05 for all). Preoperative SRL treatment was the only factor that had a significant effect on TUNEL positivity (adjusted R2=0.39, p=0.02). Preoperative treatment duration was positively correlated with TUNEL and caspase-3 immunopositivity (r=0.526, p=0.02; r=0.475, p=0.04, respectively) and negatively correlated with survivin immunopositivity (r=-0.533, p=0.01). Somatostatin analog treatment might induce apoptosis, increase autophagy, and decrease cell proliferation in GH-secreting adenomas. Also, proteins related to cross-talk between autophagy and apoptosis are upregulated after SRL treatment.