Concurrent MEK and autophagy inhibition is required to restore cell death associated danger-signalling in Vemurafenib-resistant melanoma cells

Biochem Pharmacol. 2015 Feb 1;93(3):290-304. doi: 10.1016/j.bcp.2014.12.003. Epub 2014 Dec 18.


Vemurafenib (PLX4032), an inhibitor of BRAF(V600E), has demonstrated significant clinical anti-melanoma effects. However, the majority of treated patients develop resistance, due to a variety of molecular mechanisms including MAPK reactivation through MEK. The induction of a cancer cell death modality associated with danger-signalling resulting in surface mobilization of crucial damage-associated-molecular-patterns (DAMPs), e.g. calreticulin (CRT) and heat shock protein-90 (HSP90), from dying cells, is emerging to be crucial for therapeutic success. Both cell death and danger-signalling are modulated by autophagy, a key adaptation mechanism stimulated during melanoma progression. However, whether melanoma cell death induced by MAPK inhibition is associated with danger-signalling, and the reliance of these mechanisms on autophagy, has not yet been scrutinized. Using a panel of isogenic PLX4032-sensitive and resistant melanoma cell lines we show that PLX4032-induced caspase-dependent cell death and DAMPs exposure in the drug-sensitive cells, but failed to do so in the drug-resistant cells, displaying heightened MEK activation. MEK inhibitor, U0126, treatment sensitized PLX4032-resistant cells to death and re-established their danger-signalling capacity. Only melanoma cells exposing death-induced danger-signals were phagocytosed and induced DC maturation. Although the PLX4032-resistant melanoma cells displayed higher basal and drug-induced autophagy, compromising autophagy, pharmacologically or by ATG5 knockdown, was insufficient to re-establish their PLX4032 sensitivity. Interestingly, autophagy abrogation was particularly efficacious in boosting cell death and ecto-CRT/ecto-HSP90 in PLX4032-resistant cells upon blockage of MEK hyper-activation by U0126. Thus combination of MEK inhibitors with autophagy blockers may represent a novel treatment regime to increase both cell death and danger-signalling in Vemurafenib-resistant metastatic melanoma.

Keywords: Autophagy; Cell death; Danger-signalling; Melanoma; PLX4032.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autophagy / drug effects*
  • Autophagy / physiology
  • Butadienes / pharmacology
  • Cell Death / drug effects
  • Cell Death / physiology
  • Coculture Techniques
  • Drug Resistance, Neoplasm / drug effects*
  • Drug Resistance, Neoplasm / physiology
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Indoles / pharmacology*
  • Indoles / therapeutic use
  • MAP Kinase Kinase Kinases / antagonists & inhibitors*
  • MAP Kinase Kinase Kinases / metabolism
  • Melanoma* / drug therapy
  • Melanoma* / metabolism
  • Nitriles / pharmacology
  • Signal Transduction / drug effects*
  • Signal Transduction / physiology
  • Sulfonamides / pharmacology*
  • Sulfonamides / therapeutic use
  • Vemurafenib


  • Butadienes
  • Enzyme Inhibitors
  • Indoles
  • Nitriles
  • Sulfonamides
  • U 0126
  • Vemurafenib
  • MAP Kinase Kinase Kinases