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TGF‐β1/Smad2/3 signaling pathway modulates octreotide antisecretory and antiproliferative effects in pituitary somatotroph tumor cells
Author(s) -
Picech Florencia,
Sosa Liliana DV.,
Perez Pablo A.,
Cecenarro Laura,
Oms Sergio R.,
Coca Hugo A.,
De Battista Juan C.,
Gutiérrez Silvina,
Mukdsi Jorge H.,
Torres Alicia I.,
Petiti Juan P.
Publication year - 2021
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.30360
Subject(s) - somatostatin receptor 2 , endocrinology , somatostatin , medicine , pituitary tumors , downregulation and upregulation , transforming growth factor , acromegaly , cell growth , somatotropic cell , cancer research , cyclin d1 , in vivo , signal transduction , biology , chemistry , somatostatin receptor , pituitary gland , cancer , hormone , cell cycle , microbiology and biotechnology , growth hormone , biochemistry , genetics , gene
Octreotide (OCT) is used to inhibit hormone secretion and growth in somatotroph tumors, although a significant percentage of patients are resistant. It has also been tested in nonfunctioning (NF) tumors but with poor results, with these outcomes having been associated with SSTR2 levels and impaired signaling. We investigated whether OCT inhibitory effects can be improved by TGF‐β1 in functioning and nonfunctioning somatotroph tumor cells. OCT effects on hormone secretion and proliferation were analyzed in the presence of TGF‐β1 in WT and SSTR2‐overexpressing secreting GH3 and silent somatotroph tumor cells. The mechanism underlying these effects was assessed by studying SSTR and TGFβR signaling pathways mediators. In addition, we analyzed the effects of OCT/TGF‐β1 treatment on tumor growth and cell proliferation in vivo. The inhibitory effects of OCT on GH‐ and PRL‐secretion and proliferation were improved in the presence of TGF‐β1, as well as by SSTR2 overexpression. The OCT/TGF‐β1 treatment induced downregulation of pERK1/2 and pAkt, upregulation of pSmad3, and inhibition of cyclin D1. In vivo experiments showed that OCT in the presence of TGF‐β1 blocked tumor volume growth, decreased cell proliferation, and increased tumor necrosis. These results indicate that SSTR2 levels and the stimulation of TGF‐β1/TGFβR/Smad2/3 pathway are important for strengthening the antiproliferative and antisecretory effects of OCT.