Depletion of Adipose Stroma-Like Cancer-Associated Fibroblasts Potentiates Pancreatic Cancer Immunotherapy.

[ABSTRACT] Immune checkpoint blockade therapy, transformative in some cancer types, has remained ineffective for patients with pancreatic cancer. The effects of subpopulations of cancer-associated fibroblasts (CAF) on cancer progression and therapy resistance are incompletely understood. In this study, the roles of CAFs expressing platelet-derived growth factor receptor β (Pdgfrb) and of CAFs expressing markers of adipose stromal cells (ASC) were analyzed in mice with pancreatic ductal adenocarcinoma. Ablation of Pdgfrb+ cells resulted in suppression of primary pancreatic tumor growth, reduction of extracellular matrix deposition, and increased cancer cell metastasis to the liver. A peptide D-CAN, which induces apoptosis in ASC-like CAFs, also reduced pancreatic tumor growth and extracellular matrix deposition while promoting metastases. Single-cell RNA sequencing demonstrated that depletion of either Pdgfrb+ or ASC-like CAFs decreased frequencies of tumor endothelial cells and viable cancer cells. However, whereas depletion of Pdgfrb+ CAFs led to stronger induction of cancer cell aggressiveness markers, depletion of ASC-like CAFs had an opposite effect on remaining CAFs. Depletion of ASC-like CAFs using D-CAN also led to higher infiltration of cytotoxic T-lymphocytes and B-lymphocytes. Administration of anti-PDL1 antibody (aPDL1), which inhibits the immune checkpoint, had a stronger suppressive effect on tumor growth when combined with D-CAN in both female and male mice. Liver metastases were also reduced by the D-CAN/aPDL1 combination more effectively than by aPDL1 alone in female mice. We conclude that improved approaches to target ASC-like CAFs may be effective in combination with immunotherapy.

[SIGNIFICANCE] This study shows that populations of CAFs have distinct effects on pancreatic cancer progression and shows that depletion of CAFs expressing adipose markers potentiates tumor/metastasis suppression effects of immune checkpoint blockade.