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MiR-34a is upregulated in AIP mutated pituitary adenomas and induces octreotide-resistant cell proliferation and growth hormone secretion

ABSTRACT: Pituitary adenomas (PAs) are intracranial tumors associated with significant morbidity due to hormonal dysregulation, mass effects and heavy treatment burden. Growth hormone (GH)-secreting PAs (somatotropinomas) cause acromegaly-gigantism. Genetic forms of somatotropinomas due to germline AIP mutations (AIPmut+) have an early onset and are aggressive and resistant to treatment with somatostatin analogs (SSAs), including octreotide. The molecular underpinnings of these clinical features remain unclear. We investigate the role of miRNA dysregulation in AIPmut+ versus AIPmut- PA samples by array analysis. miR-34a and miR-145 were found highly expressed in AIPmut+ vs AIPmut-somatotropinomas. Ectopic expression of AIPmut (p.R271W) in Aip-/- mouse embryonic fibroblasts upregulated miR-34a and miR-145, establishing a causal link between AIPmut and miRNA expression. In PA cells (GH3), miR-34a overexpression promoted proliferation, clonogenicity, migration and suppressed apoptosis, whereas miR-145 moderately affected proliferation and apoptosis. Moreover, high miR-34a expression increased intracellular cAMP, a critical mitogenic factor in PAs. Crucially, high miR-34a expression significantly blunted octreotide-mediated GH inhibition and anti-proliferative effects. miR-34a directly targets Gnai2 encoding Gαi2, a G protein subunit inhibiting cAMP production. Accordingly, Gαi2 levels were significantly lower in AIPmut+ versus AIPmut- PA. Taken together, somatotropinomas with AIP mutations overexpress miR-34a, which in turn downregulates Gαi2 expression, increases cAMP concentration and ultimately promotes cell growth. Upregulation of miR-34a also impairs the hormonal and antiproliferative response of PA cells to octreotide. Thus, miR-34a is a downstream target of mutant AIP that promotes a cellular phenotype mirroring the aggressive clinical features of AIPmut+ acromegaly.

ORGANISM(S): synthetic construct Homo sapiens

PROVIDER: GSE140604 | GEO | 2020/08/18

REPOSITORIES: GEO

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MiR-34a is upregulated in AIP mutated pituitary adenomas and induces octreotide-resistant cell proliferation and growth hormone secretion

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