Tolerance of mouse kidney allografts arises in grafts that develop regulatory tertiary lymphoid organs (rTLOs). Single-cell RNA-seq (scRNA-seq) data and adoptive transfer of alloreactive T cells after transplantation showed that cytotoxic CD8 ⁺ T cells are reprogrammed within the accepted graft to an exhausted/regulatory-like phenotype mediated by IFN-γ. Establishment of rTLOs was required because adoptive transfer of alloreactive T cells prior to transplantation results in kidney allograft rejection. Despite the presence of intragraft CD8 ⁺ cells with a regulatory phenotype, they were not essential for the induction and maintenance of kidney allograft tolerance since renal allotransplantation into CD8-KO recipients resulted in acceptance and not rejection. Analysis of scRNA-seq data from allograft kidneys and malignant tumors identified similar regulatory-like cell types within the T cell clusters and trajectory analysis showed that cytotoxic CD8 ⁺ T cells are reprogrammed into an exhausted/regulatory-like phenotype intratumorally. Induction of cytotoxic CD8 ⁺ T cell dysfunction of infiltrating cells appears to be a beneficial mechanistic pathway that protects the kidney allotransplant from rejection through a process we call “defensive tolerance.” This pathway has implications for our understanding of allotransplant tolerance and tumor resistance to host immunity.

Nerves can regulate tumorigenesis and cancer progression. However, clarification of the role of axon guidance molecules in tumorigenesis, innervation, and metastasis is required to better understand the tumor-promoting functions of nerves. Using murine KrasG12D-mutant pancreatic organoids, we screened axon guidance molecules and identified netrin-1 upregulation. Netrin-1 was also upregulated in vivo during pancreatic tumorigenesis in humans and mice. Mutant KRAS and β-adrenergic signaling upregulated netrin-1 and its receptor NEO1 in epithelial cells in part through the MAPK pathway. Ex vivo culture of celiac ganglia showed that netrin-1 promoted the axonogenesis of sympathetic neurons through nerve NEO1. In the Pdx1-Cre;LSL-KrasG12D/+ model, knockout (KO) of Ntn1, which encodes netrin-1, decreased sympathetic innervation and the development of pancreatic intraepithelial neoplasia. Treatment of pancreatic tumor organoids with recombinant netrin-1 enhanced cell growth, epithelial–mesenchymal transition (EMT), and cancer stemness with the upregulation of ZEB1 and SOX9 through NEO1-mediated activation of focal adhesion kinase (FAK). In Pdx1-Cre;LSL-KrasG12D/+;LSL-Trp53R172H/+ mice, Ntn1 KO reduced innervation, FAK phosphorylation, and the features of EMT and stemness to extend mouse survival. In a liver metastasis model of pancreatic ductal adenocarcinoma (PDAC), treatment with a netrin-1–neutralizing antibody or tumoral KO of Neo1 reduced ZEB1 and SOX9 and decreased tumor progression. In contrast, netrin-1 overexpression promoted innervation and the progression of PDAC liver metastasis. These data suggest that the netrin-1/NEO1 axis is a key regulator of PDAC progression, directly influencing cancer cell stemness and EMT while indirectly promoting tumor growth through nerves. Inhibiting the netrin-1 pathway could represent a potential therapeutic approach for PDAC. Significance: Netrin-1 promotes pancreatic tumorigenesis and metastasis directly and indirectly through nerves, highlighting the importance of tumor cell-nerve cross-talk in cancer and the potential of netrin-1 blockade as a treatment strategy.

(1) Background: The aim of this study is to assess perioperative therapy in stage IA-III pancreatic cancer cross-validating the German Cancer Registry Group of the Society of German Tumor Centers—Network for Care, Quality, and Research in Oncology, Berlin (GCRG/ADT) and the National Cancer Database (NCDB). (2) Methods: Patients with clinical stage IA-III PDAC undergoing surgery alone (OP), neoadjuvant therapy (TX) + surgery (neo + OP), surgery+adjuvantTX (OP + adj) and neoadjuvantTX + surgery + adjuvantTX (neo + OP + adj) were identified. Baseline characteristics, histopathological parameters, and overall survival (OS) were evaluated. (3) Results: 1392 patients from the GCRG/ADT and 29,081 patients from the NCDB were included. Patient selection and strategies of perioperative therapy remained consistent across the registries for stage IA-III pancreatic cancer. Combined neo + OP + adj was associated with prolonged OS as compared to neo + OP alone (17.8 m vs. 21.3 m, p = 0.012) across all stages in the GCRG/ADT registry. Similarly, OS with neo + OP + adj was improved as compared to neo + OP in the NCDB registry (26.4 m vs. 35.4 m, p < 0.001). (4) Conclusion: The cross-validation study demonstrated similar concepts and patient selection criteria of perioperative therapy across clinical stages of PDAC. Neoadjuvant therapy combined with adjuvant therapy is associated with improved overall survival as compared to either therapy alone.