TGFB1 improve the octreotide inhibitory effects in functioning and non-functioning pituitary tumor cells

PICECH F.; SOSA L.; PEREZ, PABLO; MOYANO G; CECENARRO L.; DE BATISTA J; COCCA H.; GUTIÉRREZ S.; MUKDSI J. H.; TORRES A.; PETITI J. P.

Mar del Plata

Congreso; LXIV Reunión Anual de la Sociedad Argentina de Investigación Clínica (SAIC); 2019

Octreotide (OCT), somatostatin analog that binds with high affinity to receptor SSTR2, is widely used to inhibit GH secretion and cell proliferation in GH-secreting adenomas. However, a significant percentage of patients are resistant to OCT. The aim was to investigate if OCT inhibitory effects are modulated by alterations on SSTR2 expression and/or interaction with TGFβ1/Smad2/3 pathway. We determined the expression of SSTR2, SSTR5, TβRI and TβRII by IHC and WB in normal pituitaries (n=6) and in 16 functioning (4 PRL, 10 GH and 2 ACTH) and 9 non-functioning adenomas (NFPA). GH3 and human NFPA cells, WT and overexpressing SSTR2, were treated for 24 h with the OCT (100 nM) and/or TGFβ1 (4 mg/ml). SSTRs and TβRs mRNA and protein expression were analyzed by qPCR and WB, GH and PRL secretion by WB, cell proliferation by BrdU incorporation. In vivo experiments by xenograft model with nude mice (t-test or one-way ANOVA-Fisher). Pituitary tumors exhibited a markedly decrease in SSTR2, SSTR5 and TβR2 expression compared to normal pituitary gland. We observed that the combination OCT/TGFβ1 lead to a significant reduction in GH and PRL secretion levels compared to OCT treatment and the hSSTR2 overexpression sensitized pituitary tumor cells to the anti-secretory effect of OCT. A significant proliferative reduction in GH3 and NFPA human cells was showed after OCT/TGFb1 treatment compared to OCT alone, effects that were potentiated in hSSTR2 overexpressing cells. These responses were associated with a significant decrease of ERK1/2, AKT and Cyclin D1 proteins and an increase of Smad2/3-mediated anti-proliferative cascade. The in vivo assays showed that the cytostatic effect of OCT was improved in presence of TGFb1 after 11d of treatment. Our results demonstrated that OCT inhibitory effects on GH- and PRL-secretion and proliferation were improved in presence of TGFβ1. These responses were reinforced in pituitary tumor cells with higher levels of SSTR2.