IFNγ treatment restores TAP-dependent presentation competence of PD-L1 sensitive PDAC cells

For immunotherapy, there is an urgent need to restore presentation-competence of cancer cells with defects in MHC-I processing/presentation. We identified two tumor-specific antigens expressed in the ER of pancreatic ductal adenocarcinoma cells (PDACCs) that induced effector CD8 T cells either independent (Cripto-1-Kb/Cr16-24) or dependent (gp70-Kb/p15E) on TAP-mediated antigen processing/presentation by DNA immunization. In systematic analyses, we showed that transplantation into syngeneic C57BL/6J mice or IFNγ-treatment in vitro upregulated MHC-I but also co-inhibitory PD-L1 molecules on PDACCs. IFNγ-treated PDACCs efficiently formed solid tumors in transplanted C57BL/6J and PD-L1-/- but were rejected in PD-1-/- mice. PDACCs induced a prophylactic immunity against tumor transplants in C57BL/6J mice when irradiated at day 2-3 post IFNγ-treatment, thereby silencing the tumor-initiated immune-suppressive PD-L1/PD-1-signaling axis. Immune-protection correlated with a significant enhanced induction of CD8 T cells against the TAP- but not the TAP-dependent antigen/epitope. RNA from PDAC cell lines, derived from KrasG12D/+, Trp53fl/fl, p48cre/+ mice on a C57BL/6J background (3 male, 2 female) was used. Cells were treated with IFNγ (20 ng/ml, 16 h) or left untreated prior to RNA extraction. Agilent Mouse Gene Expression Microarrays 4x44Kv2 were used.