Autophagy Promotes Immune Evasion of Pancreatic Cancer by Degrading MHC-I

Nature. 2020 May;581(7806):100-105. doi: 10.1038/s41586-020-2229-5. Epub 2020 Apr 22.

Abstract

Immune evasion is a major obstacle for cancer treatment. Common mechanisms of evasion include impaired antigen presentation caused by mutations or loss of heterozygosity of the major histocompatibility complex class I (MHC-I), which has been implicated in resistance to immune checkpoint blockade (ICB) therapy1-3. However, in pancreatic ductal adenocarcinoma (PDAC), which is resistant to most therapies including ICB4, mutations that cause loss of MHC-I are rarely found5 despite the frequent downregulation of MHC-I expression6-8. Here we show that, in PDAC, MHC-I molecules are selectively targeted for lysosomal degradation by an autophagy-dependent mechanism that involves the autophagy cargo receptor NBR1. PDAC cells display reduced expression of MHC-I at the cell surface and instead demonstrate predominant localization within autophagosomes and lysosomes. Notably, inhibition of autophagy restores surface levels of MHC-I and leads to improved antigen presentation, enhanced anti-tumour T cell responses and reduced tumour growth in syngeneic host mice. Accordingly, the anti-tumour effects of autophagy inhibition are reversed by depleting CD8+ T cells or reducing surface expression of MHC-I. Inhibition of autophagy, either genetically or pharmacologically with chloroquine, synergizes with dual ICB therapy (anti-PD1 and anti-CTLA4 antibodies), and leads to an enhanced anti-tumour immune response. Our findings demonstrate a role for enhanced autophagy or lysosome function in immune evasion by selective targeting of MHC-I molecules for degradation, and provide a rationale for the combination of autophagy inhibition and dual ICB therapy as a therapeutic strategy against PDAC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adenocarcinoma / drug therapy
  • Adenocarcinoma / genetics
  • Adenocarcinoma / immunology*
  • Adenocarcinoma / pathology
  • Animals
  • Antigen Presentation / drug effects
  • Antigen Presentation / immunology
  • Autophagy / drug effects
  • Autophagy / genetics
  • Autophagy / immunology*
  • CD8-Positive T-Lymphocytes / drug effects
  • CD8-Positive T-Lymphocytes / immunology
  • Carcinoma, Pancreatic Ductal / drug therapy
  • Carcinoma, Pancreatic Ductal / genetics
  • Carcinoma, Pancreatic Ductal / immunology*
  • Carcinoma, Pancreatic Ductal / pathology
  • Cell Cycle Checkpoints / drug effects
  • Cell Cycle Checkpoints / immunology
  • Cell Line, Tumor
  • Chloroquine / pharmacology
  • Female
  • Histocompatibility Antigens Class I / genetics
  • Histocompatibility Antigens Class I / immunology*
  • Histocompatibility Antigens Class I / metabolism*
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Male
  • Mice
  • Pancreatic Neoplasms / drug therapy
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / immunology*
  • Pancreatic Neoplasms / pathology
  • Tumor Escape / drug effects
  • Tumor Escape / immunology*

Substances

  • Histocompatibility Antigens Class I
  • Intracellular Signaling Peptides and Proteins
  • NBR1 protein, human
  • Chloroquine