Regulation of Aryl Hydrocarbon Receptor Interacting Protein (AIP) Protein Expression by MiR-34a in Sporadic Somatotropinomas

Abstract

IntroductionPatients with germline AIP mutations or low AIP protein expression have large, invasive somatotroph adenomas and poor response to somatostatin analogues (SSA).MethodsTo study the mechanism of low AIP protein expression 31 sporadic somatotropinomas with low (n = 13) or high (n = 18) AIP protein expression were analyzed for expression of AIP messenger RNA (mRNA) and 11 microRNAs (miRNAs) predicted to bind the 3’UTR of AIP. Luciferase reporter assays of wild-type and deletion constructs of AIP-3’UTR were used to study the effect of the selected miRNAs in GH3 cells. Endogenous AIP protein and mRNA levels were measured after miRNA over- and underexpression in HEK293 and GH3 cells.ResultsNo significant difference was observed in AIP mRNA expression between tumors with low or high AIP protein expression suggesting post-transcriptional regulation. miR-34a was highly expressed in low AIP protein samples compared high AIP protein adenomas and miR-34a levels were inversely correlated with response to SSA therapy. miR-34a inhibited the luciferase-AIP-3’UTR construct, suggesting that miR-34a binds to AIP-3’UTR. Deletion mutants of the 3 different predicted binding sites in AIP-3’UTR identified the c.*6–30 site to be involved in miR-34a’s activity. miR-34a overexpression in HEK293 and GH3 cells resulted in inhibition of endogenous AIP protein expression.ConclusionLow AIP protein expression is associated with high miR-34a expression. miR-34a can down-regulate AIP-protein but not RNA expression in vitro. miR-34a is a negative regulator of AIP-protein expression and could be responsible for the low AIP expression observed in somatotropinomas with an invasive phenotype and resistance to SSA.

Markery Proliferacji I Inwazyjności W Guzach Przysadki Wydzielających Hormon Wzrostu

“…In some 50% of sporadic adenomas, low intrinsic AIP expression, predominant invasiveness, and poor response to somatostatin analogues (SSA) are observed [27,33,34,38], especially in patients with confirmed AIP mutation [27]. While in somatropinomas AIP was claimed to be a better marker of invasiveness than Ki-67 and p53 [34], its expression varied widely in our study and elsewhere [27].…”

MANAGEMENT OF ENDOCRINE DISEASE: Personalized medicine in the treatment of acromegaly

“…Patients who harbor an AIP germline mutation are younger and present a more aggressive tumor with worse response to fg-SRL treatment 76,77,79 . Interestingly, in half of the patients with sporadic acromegaly, low expression of the AIP protein is observed due to mechanisms other than mutations [80][81][82][83] . These patients also present a worse response to fg-SRL, as described by our group 81 .…”

“…Such biomarkers include the acute octreotide test, the presence of a gsp mutation, the expression of E-cadherin, the expression of sst5 and its truncated isoform (sst5TMD4), the expression of miR-34a, the expression of β-arrestin, the Ki-67 labeling index and the Raf kinase expression 57,68,72,83,[86][87][88][89][90][91] . Additionally, some demographic characteristics, such as younger age, male gender and high pretreatment GH levels were associated with a poor response to fg-SRL in some studies [92][93][94] .…”

A mikro-RNS-ek szerepe az agyalapimirigy-daganatok tumorbiológiájában

“…Egy miRNS-nek a bá-zispárosodás szabályai szerint több célgénje is van, és egy célmolekula kifejeződését számos miRNS is szabályoz-hatja. A biológiai funkciók hátterében álló mechanizmusokat a sejten belüli jelátviteli útvonalakkal lehet a leginkább jellemezni, így a miRNS-ek szabályozó szerepét nemcsak egy-egy génhez (1. táblázat) [34,42,[44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59], hanem egy-egy jelátviteli útvonalhoz is lehet rendelni.…”