The selective PI3Kα inhibitor BYL719 as a novel therapeutic option for neuroendocrine tumors: Results from multiple cell line models

PLoS One. 2017 Aug 11;12(8):e0182852. doi: 10.1371/journal.pone.0182852. eCollection 2017.

Abstract

Background/aims: The therapeutic options for metastatic neuroendocrine tumors (NETs) are limited. As PI3K signaling is often activated in NETs, we have assessed the effects of selective PI3Kp110α inhibition by the novel agent BYL719 on cell viability, colony formation, apoptosis, cell cycle, signaling pathways, differentiation and secretion in pancreatic (BON-1, QGP-1) and pulmonary (H727) NET cell lines.

Methods: Cell viability was investigated by WST-1 assay, colony formation by clonogenic assay, apoptosis by caspase3/7 assay, the cell cycle by FACS, cell signaling by Western blot analysis, expression of chromogranin A and somatostatin receptors 1/2/5 by RT-qPCR, and chromogranin A secretion by ELISA.

Results: BYL719 dose-dependently decreased cell viability and colony formation with the highest sensitivity in BON-1, followed by H727, and lowest sensitivity in QGP-1 cells. BYL719 induced apoptosis and G0/G1 cell cycle arrest associated with increased p27 expression. Western blots showed inhibition of PI3K downstream targets to a varying degree in the different cell lines, but IGF1R activation. The most sensitive BON-1 cells displayed a significant, and H727 cells a non-significant, GSK3 inhibition after BYL719 treatment, but these effects do not appear to be mediated through the IGF1R. In contrast, the most resistant QGP-1 cells showed no GSK3 inhibition, but a modest activation, which would partially counteract the other anti-proliferative effects. Accordingly, BYL719 enhanced neuroendocrine differentiation with the strongest effect in BON-1, followed by H727 cells indicated by induction of chromogranin A and somatostatin receptor 1/2 mRNA-synthesis, but not in QGP-1 cells. In BON-1 and QGP-1 cells, the BYL719/everolimus combination was synergistic through simultaneous AKT/mTORC1 inhibition, and significantly increased somatostatin receptor 2 transcription compared to each drug separately.

Conclusion: Our results suggest that the agent BYL719 could be a novel therapeutic approach to the treatment of NETs that may sensitize NET cells to somatostatin analogs, and that if there is resistance to its action this may be overcome by combination with everolimus.

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Caspase 7 / genetics
  • Caspase 7 / metabolism
  • Cell Cycle / drug effects
  • Cell Line, Tumor
  • Chromogranin A / genetics
  • Chromogranin A / metabolism
  • Class I Phosphatidylinositol 3-Kinases / antagonists & inhibitors*
  • Class I Phosphatidylinositol 3-Kinases / genetics
  • Class I Phosphatidylinositol 3-Kinases / metabolism
  • Dose-Response Relationship, Drug
  • Drug Synergism
  • Everolimus / pharmacology*
  • Gene Expression Regulation, Neoplastic*
  • Glycogen Synthase Kinase 3 / genetics
  • Glycogen Synthase Kinase 3 / metabolism
  • Humans
  • Pancreas / drug effects*
  • Pancreas / metabolism
  • Pancreas / pathology
  • Protein Kinase Inhibitors / pharmacology*
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Receptors, Somatostatin / genetics
  • Receptors, Somatostatin / metabolism
  • Signal Transduction
  • Thiazoles / pharmacology*

Substances

  • Antineoplastic Agents
  • Chromogranin A
  • Protein Kinase Inhibitors
  • Receptors, Somatostatin
  • SSTR2 protein, human
  • Thiazoles
  • somatostatin receptor type 1
  • Alpelisib
  • somatostatin receptor 5
  • Everolimus
  • Class I Phosphatidylinositol 3-Kinases
  • PIK3CA protein, human
  • Proto-Oncogene Proteins c-akt
  • Glycogen Synthase Kinase 3
  • CASP3 protein, human
  • CASP7 protein, human
  • Caspase 3
  • Caspase 7

Grants and funding

This work has been supported by a grant from NOVARTIS (YING Investigator program) to JS and from the Roggenbruck Foundation (Hamburg, Germany) to JS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. "Zentralklinik Bad Berka GmbH, Germany" is a communal hospital of the Rhön-Klinikum AG and provided support in the form of salaries for authors [FB,PG], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the author contributions section.