Format

Send to

Choose Destination
Neuroendocrinology. 2017;105(1):90-104. doi: 10.1159/000448843. Epub 2016 Aug 12.

Inhibition of mTOR's Catalytic Site by PKI-587 Is a Promising Therapeutic Option for Gastroenteropancreatic Neuroendocrine Tumor Disease.

Author information

1
Department of Gastroenterology, Infectious Diseases, Rheumatology CC13, Charité - Universitätsmedizin Berlin, Germany.

Abstract

BACKGROUND:

The characteristic clinical heterogeneity and mostly slow-growing behavior of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) cause problems in finding appropriate treatments. Thus, the current therapy options are not satisfactory. PKI-587 is a highly potent, novel dual inhibitor of PI3K and mTORC1/C2.

AIM:

We assessed the effects of PKI-587 in different GEP-NEN tumor models, including the poorly differentiated cell line LCC-18, and compared them with those of the established mTORC1 inhibitor everolimus.

METHODS:

We treated BON, QGP-1, KRJ-I, and LCC-18 cell lines with increasing concentrations of the inhibitor PKI-587, and compared the results with those of everolimus and DMSO. We assessed the impact of the treatments on viability (WST-1 assay), on apoptotic processes (caspase 3/7 assay, JC-1), and on cell cycle regulation (flow cytometry). We determined alterations in signaling mediators by phosphor-specific Western blot analysis and conducted multiplexed gene expression analysis (nCounter® technology).

RESULTS:

In all cell lines, PKI-587 dose-dependently inhibited proliferation, whereas everolimus was less effective. Treatment with PKI-587 led to cell cycle arrest and induction of apoptosis and successfully suppressed activity of the direct mTORC1 target 4E-BP1, a crucial factor for tumor genesis only partially inhibited by everolimus. Gene expression analyses revealed relevant changes of RAS, MAPK, STAT, and PI3K pathway genes after treatment. Treatment-dependent and cell line-characteristic effects on AKT/Rb/E2F signaling regarding cell cycle control and apoptosis are extensively discussed in this paper.

CONCLUSION:

PI3K/mTOR dual targeting is a promising new therapeutic approach in neuroendocrine tumor disease that should be evaluated in further clinical trials.

KEYWORDS:

4E-BP1; Everolimus; Gastroenteropancreatic neuroendocrine tumors; Gedatolisib; LCC-18 cell line; PKI-587; Signaling; mTOR inhibition

PMID:
27513674
PMCID:
PMC5475233
DOI:
10.1159/000448843
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for S. Karger AG, Basel, Switzerland Icon for PubMed Central
Loading ...
Support Center