Targeting CXCL12 from FAP-expressing carcinoma-associated fibroblasts synergizes with anti–PD-L1 immunotherapy in pancreatic cancer

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 http://www.pnas.org/content/110/50/20212.full                     

  1. Christine Feiga,1,
  2. James O. Jonesa,1,
  3. Matthew Kramana,1,
  4. Richard J. B. Wellsa,1,
  5. Andrew Deonarineb,
  6. Derek S. Chana,
  7. Claire M. Connella,
  8. Edward W. Robertsa,2,
  9. Qi Zhaoc,
  10. Otavia L. Caballeroc,
  11. Sarah A. Teichmannd,
  12. Tobias Janowitza,
  13. Duncan I. Jodrella,
  14. David A. Tuvesona,3, and
  15. Douglas T. Fearona,4
  1. aCancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge CB2 0RE, United Kingdom;
  2. bMedical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom;
  3. cLudwig Collaborative Laboratory, Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21231; and
  4. dEuropean Molecular Biology Laboratory-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SD, United Kingdom
  1. Contributed by Douglas T. Fearon, October 31, 2013 (sent for review September 7, 2013)

Significance

Cancer immune evasion is well described. In some cases, this may be overcome by enhancing T-cell responses. We show that despite the presence of antitumor T cells, immunotherapeutic antibodies are ineffective in a murine pancreatic cancer model recapitulating the human disease. Removing the carcinoma-associated fibroblast (CAF) expressing fibroblast activation protein (FAP) from tumors permitted immune control of tumor growth and uncovered the efficacy of these immunotherapeutic antibodies. FAP+ CAFs are the only tumoral source of chemokine (C-X-C motif) ligand 12 (CXCL12), and administering AMD3100, an inhibitor of chemokine (C-X-C motif) receptor 4, a CXCL12 receptor, also revealed the antitumor effects of an immunotherapeutic antibody and greatly diminished cancer cells. These findings may have wide clinical relevance because FAP+ cells are found in almost all human adenocarcinomas.

Abstract

An autochthonous model of pancreatic ductal adenocarcinoma (PDA) permitted the analysis of why immunotherapy is ineffective in this human disease. Despite finding that PDA-bearing mice had cancer cell-specific CD8+ T cells, the mice, like human patients with PDA, did not respond to two immunological checkpoint antagonists that promote the function of T cells: anti-cytotoxic T-lymphocyte-associated protein 4 (α-CTLA-4) and α-programmed cell death 1 ligand 1 (α-PD-L1). Immune control of PDA growth was achieved, however, by depleting carcinoma-associated fibroblasts (CAFs) that express fibroblast activation protein (FAP). The depletion of the FAP+ stromal cell also uncovered the antitumor effects of α-CTLA-4 and α-PD-L1, indicating that its immune suppressive activity accounts for the failure of these T-cell checkpoint antagonists. Three findings suggested that chemokine (C-X-C motif) ligand 12 (CXCL12) explained the overriding immunosuppression by the FAP+ cell: T cells were absent from regions of the tumor containing cancer cells, cancer cells were coated with the chemokine, CXCL12, and the FAP+ CAF was the principal source of CXCL12 in the tumor. Administering AMD3100, a CXCL12 receptor chemokine (C-X-C motif) receptor 4 inhibitor, induced rapid T-cell accumulation among cancer cells and acted synergistically with α-PD-L1 to greatly diminish cancer cells, which were identified by their loss of heterozygosity of Trp53 gene. The residual tumor was composed only of premalignant epithelial cells and inflammatory cells. Thus, a single protein, CXCL12, from a single stromal cell type, the FAP+ CAF, may direct tumor immune evasion in a model of human PDA