Progranulin mediates immune evasion of pancreatic ductal adenocarcinoma through regulation of MHCI expression.

Immune evasion is indispensable for cancer initiation and progression, although its underlying mechanisms in pancreatic ductal adenocarcinoma (PDAC) are not fully known. Here, we characterize the function of tumor-derived PGRN in promoting immune evasion in primary PDAC. Tumor- but not macrophage-derived PGRN is associated with poor overall survival in PDAC. Multiplex immunohistochemistry shows low MHC class I (MHCI) expression and lack of CD8+ T cell infiltration in PGRN-high tumors. Inhibition of PGRN abrogates autophagy-dependent MHCI degradation and restores MHCI expression on PDAC cells. Antibody-based blockade of PGRN in a PDAC mouse model remarkably decelerates tumor initiation and progression. Notably, tumors expressing LCMV-gp33 as a model antigen are sensitized to gp33-TCR transgenic T cell-mediated cytotoxicity upon PGRN blockade. Overall, our study shows a crucial function of tumor-derived PGRN in regulating immunogenicity of primary PDAC.

Proton Irradiation Increases the Necessity for Homologous Recombination Repair Along with the Indispensability of Non-Homologous End Joining.

Technical improvements in clinical radiotherapy for maximizing cytotoxicity to the tumor while limiting negative impact on co-irradiated healthy tissues include the increasing use of particle therapy (e.g., proton therapy) worldwide. Yet potential differences in the biology of DNA damage induction and repair between irradiation with X-ray photons and protons remain elusive. We compared the differences in DNA double strand break (DSB) repair and survival of cells compromised in non-homologous end joining (NHEJ), homologous recombination repair (HRR) or both, after irradiation with an equal dose of X-ray photons, entrance plateau (EP) protons, and mid spread-out Bragg peak (SOBP) protons. We used super-resolution microscopy to investigate potential differences in spatial distribution of DNA damage foci upon irradiation. While DNA damage foci were equally distributed throughout the nucleus after X-ray photon irradiation, we observed more clustered DNA damage foci upon proton irradiation. Furthermore, deficiency in essential NHEJ proteins delayed DNA repair kinetics and sensitized cells to both, X-ray photon and proton irradiation, whereas deficiency in HRR proteins sensitized cells only to proton irradiation. We assume that NHEJ is indispensable for processing DNA DSB independent of the irradiation source, whereas the importance of HRR rises with increasing energy of applied irradiation.

A Novel Approach for Image-Guided 131I Therapy of Pancreatic Ductal Adenocarcinoma Using Mesenchymal Stem Cell-Mediated NIS Gene Delivery.

The sodium iodide symporter (SLC5A5/NIS) as theranostic gene would allow for non-invasive imaging of functional NIS expression and therapeutic radioiodine application. Genetically engineered mesenchymal stem cells (MSC), based on their tumor-homing abilities, show great promise as tumor-selective NIS gene delivery vehicles for non-thyroidal tumors. As a next step towards clinical application, tumor specificity and efficacy of MSCs were investigated in an advanced genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC). Syngeneic murine MSCs were stably transfected with a NIS-expressing plasmid driven by the CMV-promoter (NIS-MSC). In vivo 123I-scintigraphy and 124I-PET revealed significant perchlorate-sensitive NIS-mediated radioiodide accumulation in PDAC after systemic injection of NIS-MSCs. Active MSC recruitment into the tumor stroma was confirmed using NIS immunohistochemistry (IHC). A therapeutic strategy, consisting of three cycles of systemic MSC-mediated NIS delivery, followed by 131I application, resulted in a significant delay and reduction in tumor growth as compared to controls. Furthermore, IHC analysis of α-SMA and Ki67 revealed differences in the amount and behavior of activated fibroblasts in tumors of mice injected with NIS-MSCs as compared with saline-treated mice. Taken together, MSCs as NIS gene delivery vehicles in this advanced endogenous PDAC mouse model demonstrated high stromal targeting of NIS by selective recruitment of NIS-MSCs after systemic application resulting in an impressive 131I therapeutic effect. IMPLICATIONS: These data expand the prospect of MSC-mediated radioiodine imaging-guided therapy of pancreatic cancer using the sodium iodide symporter as a theranostic gene in a clinical setting.

Notch-Induced Myeloid Reprogramming in Spontaneous Pancreatic Ductal Adenocarcinoma by Dual Genetic Targeting.

Despite advances in our understanding of the genetics of pancreatic ductal adenocarcinoma (PDAC), the efficacy of therapeutic regimens targeting aberrant signaling pathways remains highly limited. Therapeutic strategies are greatly hampered by the extensive desmoplasia that comprises heterogeneous cell populations. Notch signaling is a contentious pathway exerting opposite roles in tumorigenesis depending on cellular context. Advanced model systems are needed to gain more insights into complex signaling in the multilayered tumor microenvironment. In this study, we employed a dual recombinase-based in vivo strategy to modulate Notch signaling specifically in myeloid cells to dissect the tumorigenic role of Notch in PDAC stroma. Pancreas-specific KrasG12D activation and loss of Tp53 was induced using a Pdx1-Flp transgene, whereas Notch signaling was genetically targeted using a myeloid-targeting Lyz2-Cre strain for either activation of Notch2-IC or deletion of Rbpj. Myeloid-specific Notch activation significantly decreased tumor infiltration by protumorigenic M2 macrophages in spontaneous endogenous PDAC, which translated into significant survival benefit. Further characterization revealed upregulated antigen presentation and cytotoxic T effector phenotype upon Notch-induced M2 reduction. This approach is the first proof of concept for genetic targeting and reprogramming of myeloid cells in a complex disease model of PDAC and provides evidence for a regulatory role of Notch signaling in intratumoral immune phenotypes.Significance: This study provides insight into the role of myeloid-dependent NOTCH signaling in PDAC and accentuates the need to dissect differential roles of signaling pathways in different cellular components within the tumor microenvironment. Cancer Res; 78(17); 4997-5010. ©2018 AACR.