A novel pathway combining calreticulin exposure and ATP secretion in immunogenic cancer cell death

EMBO J. 2012 Mar 7;31(5):1062-79. doi: 10.1038/emboj.2011.497. Epub 2012 Jan 17.


Surface-exposed calreticulin (ecto-CRT) and secreted ATP are crucial damage-associated molecular patterns (DAMPs) for immunogenic apoptosis. Inducers of immunogenic apoptosis rely on an endoplasmic reticulum (ER)-based (reactive oxygen species (ROS)-regulated) pathway for ecto-CRT induction, but the ATP secretion pathway is unknown. We found that after photodynamic therapy (PDT), which generates ROS-mediated ER stress, dying cancer cells undergo immunogenic apoptosis characterized by phenotypic maturation (CD80(high), CD83(high), CD86(high), MHC-II(high)) and functional stimulation (NO(high), IL-10(absent), IL-1β(high)) of dendritic cells as well as induction of a protective antitumour immune response. Intriguingly, early after PDT the cancer cells displayed ecto-CRT and secreted ATP before exhibiting biochemical signatures of apoptosis, through overlapping PERK-orchestrated pathways that require a functional secretory pathway and phosphoinositide 3-kinase (PI3K)-mediated plasma membrane/extracellular trafficking. Interestingly, eIF2α phosphorylation and caspase-8 signalling are dispensable for this ecto-CRT exposure. We also identified LRP1/CD91 as the surface docking site for ecto-CRT and found that depletion of PERK, PI3K p110α and LRP1 but not caspase-8 reduced the immunogenicity of the cancer cells. These results unravel a novel PERK-dependent subroutine for the early and simultaneous emission of two critical DAMPs following ROS-mediated ER stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Antigens, CD / metabolism
  • B7-1 Antigen / metabolism
  • B7-2 Antigen / metabolism
  • Calreticulin / metabolism*
  • Cell Death*
  • Cell Line
  • Dendritic Cells / immunology
  • Endoplasmic Reticulum / drug effects
  • Histocompatibility Antigens Class II / metabolism
  • Humans
  • Immunoglobulins / metabolism
  • Membrane Glycoproteins / metabolism
  • Neoplasms / immunology*
  • Photosensitizing Agents / pharmacology
  • Reactive Oxygen Species / metabolism
  • Reactive Oxygen Species / toxicity


  • Antigens, CD
  • B7-1 Antigen
  • B7-2 Antigen
  • CD83 antigen
  • CD86 protein, human
  • Calreticulin
  • Histocompatibility Antigens Class II
  • Immunoglobulins
  • Membrane Glycoproteins
  • Photosensitizing Agents
  • Reactive Oxygen Species
  • Adenosine Triphosphate