Abstract
Immunotherapy has shown promising results in multiple solid tumors and hematological malignancies. However, pancreatic ductal adenocarcinoma (PDAC) has been largely refractory to current clinical immunotherapies. The V-domain Ig suppressor of T-cell activation (VISTA) inhibits T-cell effector function and maintains peripheral tolerance. Here, we determine VISTA expression in nontumorous pancreatic (n = 5) and PDAC tissue using immunohistochemistry (n = 76) and multiplex immunofluorescence staining (n = 67). Additionally, VISTA expression on tumor-infiltrating immune cells and matched blood samples (n = 13) was measured with multicolor flow cytometry. Further, the effect of recombinant VISTA on T-cell activation was investigated in vitro, and VISTA blockade was tested in an orthotopic PDAC mouse model in vivo. PDAC showed significantly higher VISTA expression compared to that of a nontumorous pancreas. Patients with a high density of VISTA-expressing tumor cells had reduced overall survival. The VISTA expression of CD4+ and CD8+ T cells was increased after stimulation and particularly after a coculture with tumor cells. We detected a higher level of proinflammatory cytokine (TNFα and IFNγ) expression by CD4+ and CD8+ T cells, which was reversed with the addition of recombinant VISTA. A VISTA blockade reduced tumor weights in vivo. The VISTA expression of tumor cells has clinical relevance, and its blockade may be a promising immunotherapeutic strategy for PDAC.