Frontiers in Oncology (Apr 2022)

Intra-Tumoral CD8+ T-Cell Infiltration and PD-L1 Positivity in Homologous Recombination Deficient Pancreatic Ductal Adenocarcinoma

  • Bryn Golesworthy,
  • Bryn Golesworthy,
  • Yifan Wang,
  • Yifan Wang,
  • Yifan Wang,
  • Amanda Tanti,
  • Amanda Tanti,
  • Alain Pacis,
  • Alain Pacis,
  • Joan Miguel Romero,
  • Joan Miguel Romero,
  • Adeline Cuggia,
  • Adeline Cuggia,
  • Celine Domecq,
  • Celine Domecq,
  • Guillaume Bourdel,
  • Guillaume Bourdel,
  • Robert E. Denroche,
  • Gun Ho Jang,
  • Robert C. Grant,
  • Ayelet Borgida,
  • Barbara T. Grünwald,
  • Anna Dodd,
  • Julie M. Wilson,
  • Guillaume Bourque,
  • Guillaume Bourque,
  • Grainne M. O’Kane,
  • Grainne M. O’Kane,
  • Sandra E. Fischer,
  • Sandra E. Fischer,
  • Chelsea Maedler Kron,
  • Chelsea Maedler Kron,
  • Pierre-Olivier Fiset,
  • Pierre-Olivier Fiset,
  • Atilla Omeroglu,
  • Atilla Omeroglu,
  • William D. Foulkes,
  • William D. Foulkes,
  • Steven Gallinger,
  • Steven Gallinger,
  • Steven Gallinger,
  • Marie-Christine Guiot,
  • Marie-Christine Guiot,
  • Zu-Hua Gao,
  • Zu-Hua Gao,
  • George Zogopoulos,
  • George Zogopoulos,
  • George Zogopoulos

DOI
https://doi.org/10.3389/fonc.2022.860767
Journal volume & issue
Vol. 12

Abstract

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The immune contexture of pancreatic ductal adenocarcinoma (PDAC) is generally immunosuppressive. A role for immune checkpoint inhibitors (ICIs) in PDAC has only been demonstrated for the rare and hypermutated mismatch repair (MMR) deficient (MMR-d) subtype. Homologous recombination repair (HR) deficient (HR-d) PDAC is more prevalent and may encompass up to 20% of PDAC. Its genomic instability may promote a T-cell mediated anti-tumor response with therapeutic sensitivity to ICIs. To investigate the immunogenicity of HR-d PDAC, we used multiplex immunohistochemistry (IHC) to compare the density and spatial distribution of CD8+ cytotoxic T-cells, FOXP3+ regulatory T-cells (Tregs), and CD68+ tumor-associated macrophages (TAMs) in HR-d versus HR/MMR-intact PDAC. We also evaluated the IHC positivity of programmed death-ligand 1 (PD-L1) across the subgroups. 192 tumors were evaluated and classified as HR/MMR-intact (n=166), HR-d (n=25) or MMR-d (n=1) based on germline testing and tumor molecular hallmarks. Intra-tumoral CD8+ T-cell infiltration was higher in HR-d versus HR/MMR-intact PDAC (p<0.0001), while CD8+ T-cell densities in the peri-tumoral and stromal regions were similar in both groups. HR-d PDAC also displayed increased intra-tumoral FOXP3+ Tregs (p=0.049) and had a higher CD8+:FOXP3+ ratio (p=0.023). CD68+ TAM expression was similar in HR-d and HR/MMR-intact PDAC. Finally, 6 of the 25 HR-d cases showed a PD-L1 Combined Positive Score of >=1, whereas none of the HR/MMR-intact cases met this threshold (p<0.00001). These results provide immunohistochemical evidence for intra-tumoral CD8+ T-cell enrichment and PD-L1 positivity in HR-d PDAC, suggesting that HR-d PDAC may be amenable to ICI treatment strategies.

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