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

PICECH, F; SOSA L DEL V.; PEREZ P; MOYANO CRESPO G D; CECENARO L; DE BATISTA J; COCCA H; GUTIERREZ, S.; MUKDSI, J. H.; TORRES, A I; PETITI J P

Mar del Plata

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

Octreotide (OCT), somatostatin analogthat binds with high affinity to receptor SSTR2, is widely used toinhibit GH secretion and cell proliferation in GH-secretingadenomas. However, a significant percentage of patients areresistant to OCT. The aim was to investigate if OCT inhibitoryeffects are modulated by alterations on SSTR2 expression and/orinteraction with TGFb1/Smad2/3 pathway. We determined theexpression of SSTR2, SSTR5, TbRI and TbRII by IHC and WB innormal pituitaries (n= 6) and in 16 functioning (4 PRL, 10 GHand 2 ACTH) and 9 non-functioning adenomas (NFPA). EthicsCommittee (Repis N° 37/2014). GH3 and human NFPA cells, WTand overexpressing SSTR2, were treated for 24 h with the OCT(100 nM) and/or TGFb1 (4 mg/ml). SSTRs and TbRs mRNA andprotein expression were analyzed by qPCR and WB, GH and PRLsecretion by WB, cell proliferation by BrdU incorporation. In vivoexperiments by xenograft model with nude mice. Protocolapproved by CICUAL-FCM-UNC. (t-test or one-way ANOVAFisher).Pituitary tumors exhibited a markedly decrease inSSTR2, SSTR5 and TbR2 expression compared to normalpituitary gland. We observed that the combination OCT/TGFb1lead to a significant reduction in GH and PRL secretion levelscompared to OCT treatment and the hSSTR2 overexpressionsensitized pituitary tumor cells to the anti-secretory effect ofOCT. A significant proliferative reduction in GH3 and NFPAhuman cells was showed after OCT/TGFb1 treatment comparedto OCT alone, effects that were potentiated in hSSTR2overexpressing cells. These responses were associated with asignificant decrease of ERK1/2, AKT and Cyclin D1 proteins andan increase of Smad2/3-mediated anti-proliferative cascade. Thein vivo assays showed that the cytostatic effect of OCT wasimproved in presence of TGFb1 after 11d of treatment. Ourresults demonstrated that OCT inhibitory effects on GH- and PRLsecretionand proliferation were improved in presence of TGFb1.These responses were reinforced in pituitary tumor cells withhigher levels of SSTR2.