Combined EGFR and ROCK Inhibition in Triple-negative Breast Cancer Leads to Cell Death Via Impaired Autophagic Flux

Mol Cell Proteomics. 2020 Feb;19(2):261-277. doi: 10.1074/mcp.RA119.001800. Epub 2019 Nov 26.

Abstract

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with very limited therapeutic options. We have recently shown that the combined inhibition of EGFR and ROCK in TNBC cells results in cell death, however, the underlying mechanisms remain unclear. To investigate this, here we applied a mass spectrometry-based proteomic approach to identify proteins altered on single and combination treatments. Our proteomic data revealed autophagy as the major molecular mechanism implicated in the cells' response to combinatorial treatment. We here show that EGFR inhibition by gefitinib treatment alone induces autophagy, a cellular recycling process that acts as a cytoprotective response for TNBC cells. However, combined inhibition of EGFR and ROCK leads to autophagy blockade and accumulation of autophagic vacuoles. Our data show impaired autophagosome clearance as a likely cause of antitumor activity. We propose that the inhibition of the autophagic flux on combinatorial treatment is attributed to the major cytoskeletal changes induced on ROCK inhibition, given the essential role the cytoskeleton plays throughout the various steps of the autophagy process.

Keywords: Label-free quantification; TNBC; autophagy; cancer biology; combination treatment; drug resistance; drug targets; phosphoproteome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Autophagy / drug effects*
  • Cell Death / drug effects*
  • Cell Line, Tumor
  • ErbB Receptors / antagonists & inhibitors
  • Female
  • Gefitinib / pharmacology
  • Humans
  • Imidazoles / pharmacology
  • Mass Spectrometry
  • Oxadiazoles / pharmacology
  • Protein Kinase Inhibitors / pharmacology*
  • Proteomics
  • Triple Negative Breast Neoplasms / metabolism*
  • rho-Associated Kinases / antagonists & inhibitors*

Substances

  • Antineoplastic Agents
  • Imidazoles
  • N-(3-((2-(4-amino-1,2,5-oxadiazol-3-yl)-1-ethyl-1H-imidazo(4,5-c)pyridin-6-yl)oxy)phenyl)-4-((2-(4-morpholinyl)ethyl)oxy)benzamide
  • Oxadiazoles
  • Protein Kinase Inhibitors
  • EGFR protein, human
  • ErbB Receptors
  • rho-Associated Kinases
  • Gefitinib