miR-26a Plays an Important Role in Cell Cycle Regulation in ACTH-Secreting Pituitary Adenomas by Modulating Protein Kinase Cδ

Abstract

The functional aftermath of microRNA (miRNA) dysregulation in ACTH-secreting pituitary adenomas has not been demonstrated. miRNAs represent diagnostic and prognostic biomarkers as well as putative therapeutic targets; their investigation may shed light on the mechanisms that underpin pituitary adenoma development and progression. Drugs interacting with such pathways may help in achieving disease control also in the settings of ACTH-secreting pituitary adenomas. We investigated the expression of 10 miRNAs among those that were found as most dysregulated in human pituitary adenoma tissues in the settings of a murine ACTH-secreting pituitary adenoma cell line, AtT20/D16v-F2. The selected miRNAs to be submitted to further investigation in AtT20/D16v-F2 cells represent an expression panel including 5 up-regulated and 5 down-regulated miRNAs. Among these, we selected the most dysregulated mouse miRNA and searched for miRNA targets and their biological function. We found that AtT20/D16v-F2 cells have a specific miRNA expression profile and that miR-26a is the most dysregulated miRNA. The latter is overexpressed in human pituitary adenomas and can control viable cell number in the in vitro model without involving caspase 3/7-mediated apoptosis. We demonstrated that protein kinase Cδ (PRKCD) is a direct target of miR-26a and that miR26a inhibition delays the cell cycle in G1 phase. This effect involves down-regulation of cyclin E and cyclin A expression via PRKCD modulation. miR-26a and related pathways, such as PRKCD, play an important role in cell cycle control of ACTH pituitary cells, opening new therapeutic possibilities for the treatment of persistent/recurrent Cushing's disease.

Epidrug mediated re-expression of miRNA targeting the HMGA transcripts in pituitary cells

“…However, although technical limitations precluded us from determining the relative or absolute contribution of each of these pathways, our conclusions are reinforced by the independent approaches that reach similar conclusions and described above. [11,14,45] Thus far, investigations characterizing the inappropriate expression of miRNA in the genesis of pituitary adenomas has already led to the identification of subtype-specific miRNA profiles [46,47,16], identification of miRNA that show correlations with tumour size [40] or are predictive of tumor sensitivity and or response to therapeutic interventions. [47,16] and have been subject to recent and extensive review, [48][49][50][51].…”

“…Indeed, and in this context, some of these issues have been subject to recent review (52). More recent reports that in this case identify targets of miRNA that themselves play key roles or are central regulators of pathways that include, as example protein kinase Cδ and PTEN-AKT respectively might offer alternate indirect approaches [16,15]. In these cases investigators identified previously unknown, but what would appear to be novel targets that may represent pathways for more direct therapeutic interventions.…”

“…[14] More recent studies, of inappropriate miRNA expression profile in this case in GH and ACTH secreting adenomas also show that particular miRNA can elicit growth suppressive actions in vitro, and also in, in vivo model systems. [15,16] Collectively, these reports portend the therapeutic potential of miRNA through either restoration or inhibition of their expression in tumour cells.…”

Mitotane reduces human and mouse ACTH-secreting pituitary cell viability and function

“…The cell line was maintained in DMEM (Invitrogen) supplemented with 10% horse serum (HS) (LGC Standards, Milano, Italy) and antibiotic antimycotic (EuroClone, Milano, Italy) at 37 8C in 5% CO 2 , as described previously (Gentilin et al 2013). Before each experiment, cells were incubated in 0.5% HS medium for 48 h followed by a 24-h incubation in 10% HS medium.…”

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.…”