Bailey-Lundberg, J. | Search bioRxiv

bioRxiv2022

Radiofrequency ablation remodels the tumor microenvironment and promotes systemic immunomodulation in pancreatic cancer

Background and AimsPancreatic ductal adenocarcinoma (PDAC) is characterized by resistance to therapy. A major contributing factor to therapeutic failure is profound desmoplasia and a well-documented hypoxic tumor microenvironment (TME). In PDAC, several therapeutic approaches, including chemotherapy and radiation alone or combined with immune checkpoint inhibitors, have shown minimal therapeutic success, placing an imperative need for the discovery and application of innovative treatments. Endoscopic ultrasound guided radiofrequency ablation (EUS-RFA) is a promising immunomodulator therapy for PDAC. In this work, we hypothesized RFA promotes local and systemic stromal and immunomodulating effects that can be identified for new combination therapeutic strategies. MethodsTo test our hypothesis, a syngeneic PDAC mouse model was performed by symmetrically injecting 100k murine KPC cells in bilateral flanks of C57BL/6 female mice. RFA treatment initiated when tumors reached 200-500 mm3 and was performed only in the right flank. The left flank tumor (non-RFA contralateral side) was used as a paired control for further analysis. ResultsRFA promoted a significant reduction in tumor growth rate 4 days after treatment in RFA treated and non-RFA side contralateral tumors from treated mice when compared to controls. Histological analysis revealed a significant increase in expression of cleaved Caspase3 in RFA treated tumors. In addition, collagen deposition and CD31+ cells were significantly elevated in RFA side and non-RFA contralateral tumors from RFA treated mice. Proteome profiling showed changes in C5a and IL-23 in RFA responsive tumors, indicating a role of RFA in modulating intratumoral inflammatory responses. ConclusionsThese data indicate RFA promotes local and systemic anti-tumor responses in a syngeneic mouse model of PDAC implicating RFA treatment for local tumors as well as metastatic disease. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

cancer biology↗

bioRxiv2021

Adar1 deletion causes degeneration of exocrine pancreas via Mavs-dependent interferon signaling

Adenosine deaminase acting on RNA 1 (ADAR1) is an RNA-binding protein that deaminates adenosine(A) to inosine(I). A-to-I editing alters post-transcriptional RNA processing making ADAR1 a critical regulator of gene expression. Consequently, Adar1 has been implicated in organogenesis. To determine the role of Adar1 in pancreatic development and homeostasis, we specifically deleted Adar1 from the murine pancreas (Ptf1aCre/+; Adar1Fl/Fl). The resulting mice had stunted growth likely due to malabsorption associated with exocrine pancreas insufficiency. Analyses of pancreases revealed ductal expansion, heightened interferon-stimulated gene expression and an increased influx of immune cells. In addition, we observed an increased prevalence of CD4+ T and natural killer cells in their splenic tissue. These results indicate an association between loss of pancreatic Adar1 with dysregulation of systemic immunity. Concurrent deletion of Adar1 and Mavs, a signaling protein implicated in the innate immune pathway rescued the degenerative phenotype and resulted in normal pancreatic development. Taken together, our work suggests that the primary function of Adar1 in the pancreas is to prevent aberrant activation of the Mavs-mediated innate immune pathway, thereby maintaining pancreatic homeostasis. Summary statementThis work defines the role of Adar1 in pancreatic development and homeostasis.

developmental biology↗