Cholecystokinin receptor antagonist alters pancreatic cancer microenvironment and increases efficacy of immune checkpoint antibody therapy in mice

We examined the effects of CCKR antagonists or immune checkpoint blockade antibodies alone or in combination in murine models of PDAC. Monotherapy with CCKR blockade significantly decreased tumor size and metastases in SCID mice with orthotopic PDAC, and in C57BL/6 mice, it reduced fibrosis and induced the influx of TILs. Immune-competent mice bearing syngeneic pancreatic cancer (Panc02 and mT3-2D) that were treated with the combination of CCK receptor antagonists and immune checkpoint blockade antibodies survived significantly longer with smaller tumors. Tumor immunohistochemical staining and flow cytometry demonstrated that the tumors of mice treated with the combination regimen had a significant reduction in Foxp3+  T-regulatory cells and an increase in CD4+ and CD8+ lymphocytes. Masson’s trichrome stain analysis revealed 50% less fibrosis in the tumors of mice treated with CCKR antagonist compared to controls and compared to checkpoint antibody therapy. CCKR antagonists given with immune checkpoint antib ody therapy represent a novel approach for improving survival of PDAC. The mechanism by which this combination therapy improves the survival of PDAC may be related to the decreased fibrosis and immune cells of the tumor microenvironment.
Source: Cancer Immunology, Immunotherapy - Category: Cancer & Oncology Source Type: research