Cytokines interact with their receptor complexes to orchestrate diverse processes-from immune responses to behavioral modulation. Interleukin-17A (IL-17A) mediates protective immune responses by binding to IL-17 receptor A (IL-17RA) and IL-17RC subunits. IL-17A also modulates social interaction, yet the role of cytokine receptors in this process and their expression in the brain remains poorly characterized. Here, we mapped the brain-region-specific expression of all major IL-17R subunits and found that in addition to IL-17RA, IL-17RB-but not IL-17RC-plays a role in social behaviors through its expression in the cortex. We further showed that IL-17E, expressed in cortical neurons, enhances social interaction by acting on IL-17RA- and IL-17RB-expressing neurons. These findings highlight an IL-17 circuit within the cortex that modulates social behaviors. Thus, characterizing spatially restricted cytokine receptor expression can be leveraged to elucidate how cytokines function as critical messengers mediating neuroimmune interactions to shape animal behaviors.

While microbiota regulates immunity, and altered microbiota composition was linked to atherosclerosis, the role of cytokine signaling in intestinal epithelial cells (IEC) controlling host-microbiota interactions in atherosclerosis remains unknown. Here we found that IL17RC deletion in IEC enhanced atherosclerosis in Western diet (WD) fed Ldlr-/-Il17rcDIEC mice that was accompanied by reduced mucus and junction proteins and enhanced gut permeability. RNAseq analysis revealed heightened inflammation and altered luminal and adhesive microbiota composition in small intestines of Ldlr-/-Il17rcDIEC mice with atherosclerosis. Single cell RNA seq of immune cells showed accumulation of IL17A + gdT cells in aortas of Ldlr-/-Il17rcDIEC mice. Furthermore, atherosclerosis in Ldlr-/-Il17rcDIEC mice was accompanied by neuronal expansion and activation as determined by RNA seq and microscopy, while chemical denervation suppressed the disease. The expansion of Th1+ sympathetic neurons is aortas of Ldlr-/-Il17rcDIEC mice was microbiota dependent as co-housing enhanced the disease in IL17RC sufficient mice, while microbiota depletion suppressed it, along with neuronal and inflammatory signatures in aortas. Overall, our work uncovers novel role of IL17RC signaling in atherosclerosis and shows that intestinal IL17RC controls the disease by keeping in check intestinal barrier and microbiota that in turn regulates IL17A + gdT cells and neuroinflammation in aorta. Supported by NIH/NHLBI 1R01HL173975-01 Cytokines and Chemokines and Their Receptors (CCR)

We demonstrated previously that blocking IL-17A, a proinflammatory cytokine, prevents oxycodone-induced depression-like effects and anxiety-like effects during abstinence from MDPV (a psychostimulant) in rats. Here, we tested the hypothesis that eliminating IL-17A signaling (pharmacological antagonism using IL-17A Ab or genetic deletion of IL-17RC) would inhibit behavioral and neurochemical effects elicited by methamphetamine (METH) exposure and abstinence in adult mice. We investigated rewarding and locomotor-activating effects of METH and withdrawal-induced anxiety- and depression-like effects during METH abstinence. Mice received saline or METH (5 mg/kg, IP) once daily for 18 d. Locomotion was measured on days 1 and 15. Anxiety- and depression-like effects were investigated 72 and 96 h after the last METH injection using the elevated plus maze and forced swim test, respectively. IL-17A antibody (Ab, 60 μg/100 μl, IP) was injected every 3rd day of METH exposure. METH-induced hyperlocomotion was significantly reduced in IL-17RC knockout mice or by treatment with the IL-17A Ab (100 μg/100 μl). Neutralization of IL-17A or genetic deletion of IL-17RC prevented development of depression-like effects during METH abstinence. Also, mRNA levels of IL-17RC, but not IL-17RA, in the NAC were enhanced during METH abstinence. Development of METH conditioned place preference (CPP) was prevented by IL-17A Ab but was not affected by IL-17RC deletion in mice conditioned with METH (3 mg/kg) for 4 d. Our data show that abolishing IL-17A signaling reduces METH-induced hyperlocomotion and CPP and attenuates depression-like effects during METH abstinence. These results highlight studying IL-17A blockade as a neuroimmune-based approach to mitigate METH adverse effects.

Microbiota plays a crucial role in regulating immunity and has been suggested to contribute to atherosclerosis, the precise role of cytokine signaling in intestinal epithelial cells (IEC) in controlling microbiota, inflammation, and vascular disease is poorly understood. Here we investigate the role of IL-17RC signaling in intestinal epithelial cells (IEC) using newly generated Ldlr -/- Il17rc Δ IEC mice. We found that IEC-specific ablation of IL-17RC heightened intestinal inflammation, altered microbiota composition, and led to enhanced atherosclerosis development accompanied by accumulation of activated myeloid and T cells in aortas along with upregulation of genes reminiscent of neuroinflammatory signature. IL-17RC ablation in IEC reduced tight junction proteins contributing to enhanced gut permeability. RNAseq analysis of intestines revealed upregulation of multiple inflammatory pathways, including interferon and TLR signaling, while several metabolic pathways were downregulated in Ldlr -/- Il17rc Δ IEC mice; implying an important role of IL-17R signaling in the control of IEC metabolism, microbes and metabolites at the host-microbiota interface. Metagenomic sequencing revealed alteration of microbiota composition in Ldlr -/- Il17rc Δ IEC . Atherosclerosis development was microbiota dependent as co-housing enhanced the disease in control mice, while microbiota depletion significantly suppressed the disease.Our work uncovers novel protective role of IL-17 signaling in intestine which regulates the barrier, microbiota and metabolism leading to reduced neuroinflammation in atherosclerotic aorta.

Abstract Liver cancer is the 3rd leading cause of cancer death. Hepatocellular carcinoma (HCC) is the major form of primary liver cancer, with a growing incidence rate estimated to surge by 50% in the coming twenty years. Although some success has been achieved with immune checkpoint blockade inhibitors, many HCC patients do not respond well to the treatments. Therefore, it is critical to better understand immune mechanisms regulating HCC to identify new biomarkers and develop novel immunotherapies for HCC patients. HCC is driven by chronic liver diseases and is frequently associated with chronic inflammation in the liver. Cytokines are small mediators of inflammation that play an essential role in inflammatory diseases and tumorigenesis. IL27 is a member of the IL6/IL12 superfamily with context-dependent roles in various inflammatory disorders and cancer. IL27 receptor (R) is expressed by most immune cells and several non-immune cells and plays pivotal roles in the regulation of immune responses. Recent work from our lab shows that IL27R signaling suppresses anti-cancer immune response in HCC, acting via the control of innate cytotoxic cells, and Il27ra -/- mice develop significantly less HCC. However, how IL27R signaling regulates T cell subsets in HCC in vivo remains elusive. Here, using diethylnitrosamine (DEN)-induced mouse model of HCC we found a reduction of regulatory T cells (Tregs) in tumor-bearing Il27ra-/-mice along with lowered HCC burden. ScRNA sequencing of CD45+ cells isolated from HCC tumors indicated a less proliferative phenotype of Tregs and more cytotoxic and less exhausted CD8 T cells in mice with Il27ra deficiency. Pathway analysis suggested that IL27R-deficient Tregs were more quiescent, as characterized by the downregulation of various metabolic pathways. Our newly generated Foxp3 cre Il27ra flox mice show a significant reduction of DEN-driven HCC accompanied by an increase of tumor-infiltrating activated CD8 T cells compared to IL27R sufficient controls. Treg-specific deletion of IL27R caused the upregulation of TCF1 in Tregs which has been recently demonstrated to control Treg immune-suppressive functions in colorectal cancer. Meanwhile, tumor-infiltrating effector CD8 T cells were increased in Foxp3 cre+ Il27ra flox mice relative to their Foxp3 cre- Il27ra flox littermate controls. Interestingly, CD8 T cell specific deletion of IL27R did not impact HCC growth in CD8 cre Il27ra flox mice. Overall, our data suggest that IL27R signaling suppresses anti-HCC immunity by enhancing the pro-tumorigenic Tregs and suppressing anti-tumor effector CD8 T cell functions. Citation Format: Zhengzheng Shi, Jiani Zhu, Aleksandra Mazitova, Anastasiia Marchenko, Sergei Grivennikov, Ekaterina Koltsova. IL-27R signaling modulates protective versus pathogenic T cell responses in hepatocellular carcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C015.

Abstract Advanced colorectal cancer (CRC) is resistant to current immunotherapies and prone to metastasis. Chronic inflammation mediated by cytokines such as interleukin (IL)17 activates the oncogenic pathways in cancer cells, promoting sporadic and inflammation-associated CRC. Increased levels of IL17A in early stages of CRC portends poor prognosis indicating its potential involvement into metastasis. We and others previously showed that IL17A signaling is required for early CRC tumorigenicity in a variety of models and that in early CRC, its ability to signal to epithelial cells is essential. What remains unknown is whether IL17 signaling to other cell types within the tumor microenvironment (TME) is essential to control tumor progression and metastasis. Using a model of colitis-associated cancer (CAC) we found that “late” IL17A neutralization decreases tumor burden, possibly acting through regulation of myeloid cells and chemokine network essential for the control of immunosuppressive TME. Next, using models of colorectal cancer liver metastasis (CRLM) including intraportal cell injection and cecum transplantation of organoids with distinct set of oncogenic mutation we found that IL17 neutralization reduces metastasis. FACS analysis revealed that IL17A promotes the recruitment of tumor-associated macrophages and other key myeloid subsets into the metastatic liver environment. Interestingly, ablation of IL17RC (receptor) in myeloid cells only (using Il17rcf/f -LysMCre mice) led to reduction in metastasis and reshaping of metastatic myeloid cell compartments. Meanwhile, IL17 signaling in hepatocytes was required for early metastasis and pre-metastatic niche formation, as the ablation of IL17RC in hepatocytes (using Il17rcf/f -AlbCre mice) led to a reduction of metastatic numbers but not growth. This coincided with reduced neutrophil recruitment and enhanced activation of cytotoxic innate lymphoid cells and CD8 T lymphocytes, indicating the role of hepatocyte specific IL17 signaling in blunting anti-tumor immunity. Our findings illuminate the role of inflammatory cytokine IL17 into CRC progression and metastasis and imply its distinct cell type specific role within the metastatic liver TME. Citation Format: Katarzyna Chojnacka, Dan Kamen, Katrina M. Reyes, Hana Tomizawa, Sergei I. Grivennikov. Crosstalk between hepatocyte and myeloid-specific IL17 signaling in colorectal cancer metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1385.

Immunoglobulin A (IgA) is the most abundant antibody isotype produced across mammals and plays a specialized role in mucosal homeostasis1. Constantly secreted into the lumen of the intestine, IgA binds commensal microbiota to regulate their colonization and function2,3with unclear implications for health. IgA deficiency is common in humans but is difficult to study due to its complex aetiology and comorbidities4–8. Using genetically and environmentally controlled mice, here we show that IgA-deficient animals have increased susceptibility to endogenous colorectal tumours. Cellular and molecular analyses revealed that, in the absence of IgA, colonic epithelial cells induce antibacterial factors and accelerate cell cycling in response to the microbiota. Oral treatment with IgA was sufficient to both reduce steady-state proliferation and protect mice from tumours, but this function was due to antibody structure rather than binding specificity. In both organoid and monolayer culture systems, IgA directly suppressed epithelial growth. Co-immunoprecipitation mass spectrometry and a targeted CRISPR screen identified DMBT1 as an IgA-binding epithelial surface protein required for IgA-mediated suppression of proliferation. Together, IgA and DMBT1 regulate Notch signalling and tune the normal cycling of absorptive colonocyte progenitors. In mice, deleting the transmembrane and cytoplasmic signalling portions of DMBT1 or blocking Notch signalling was sufficient to reverse both the increased proliferation and tumour susceptibility of IgA knockouts. These experiments establish a homeostatic function for IgA in tempering physiological epithelial responses to microbiota to maintain mucosal health.

Background & AimsAdvanced colorectal carcinoma (CRC) is characterized by a high frequency of primary immune evasion and refractoriness to immunotherapy. Given the importance of interferon (IFN)-γ in CRC immunosurveillance, we investigated whether and how acquired IFN-γ resistance in tumor cells would promote tumor growth, and whether IFN-γ sensitivity could be restored.MethodsSpontaneous and colitis-associated CRC development was induced in mice with a specific IFN-γ pathway inhibition in intestinal epithelial cells. The influence of IFN-γ pathway gene status and expression on survival was assessed in patients with CRC. The mechanisms underlying IFN-γ resistance were investigated in CRC cell lines.ResultsThe conditional knockout of the IFN-γ receptor in intestinal epithelial cells enhanced spontaneous and colitis-associated colon tumorigenesis in mice, and the loss of IFN-γ receptor α (IFNγRα) expression by tumor cells predicted poor prognosis in patients with CRC. IFNγRα expression was repressed in human CRC cells through changes in N-glycosylation, which decreased protein stability via proteasome-dependent degradation, inhibiting IFNγR-signaling. Downregulation of the bisecting N-acetylglucosaminyltransferase III (MGAT3) expression was associated with IFN-γ resistance in all IFN-γ–resistant cells, and highly correlated with low IFNγRα expression in CRC tissues. Both ectopic and pharmacological reconstitution of MGAT3 expression with all-trans retinoic acid increased bisecting N-glycosylation, as well as IFNγRα protein stability and signaling.ConclusionsTogether, our results demonstrated that tumor-associated changes in N-glycosylation destabilize IFNγRα, causing IFN-γ resistance in CRC. IFN-γ sensitivity could be reestablished through the increase in MGAT3 expression, notably via all-trans retinoic acid treatment, providing new prospects for the treatment of immune-resistant CRC.

Supplementary Data from IL27 Signaling Serves as an Immunologic Checkpoint for Innate Cytotoxic Cells to Promote Hepatocellular Carcinoma

Colorectal cancer (CRC) is one of the most common cancers, with an annual incidence of ~135,000 in the US, associated with ~50,000 deaths. Autosomal dominant polycystic kidney disease (ADPKD), associated with mutations disabling the PKD1 gene, affects as many as 1 in 1000. Intriguingly, some studies have suggested that individuals with germline mutations in PKD1 have reduced incidence of CRC, suggesting a genetic modifier function. Using mouse models, we here establish that loss of Pkd1 greatly reduces CRC incidence and tumor growth induced by loss of the tumor suppressor Apc . Growth of Pkd1 −/− ;Apc −/− organoids was reduced relative to Apc −/− organoids, indicating a cancer cell-intrinsic activity, even though Pkd1 loss enhanced activity of pro-oncogenic signaling pathways. Notably, Pkd1 loss increased colon barrier function, with Pkd1 -deficient animals resistant to DSS-induced colitis, associated with upregulation of claudins that decrease permeability, and reduced T cell infiltration. Notably, Pkd1 loss caused greater sensitivity to activation of CFTR, a tumor suppressor in CRC, paralleling signaling relations in ADPKD. Overall, these data and other data suggest germline and somatic mutations in PKD1 may influence incidence, presentation, and treatment response in human CRC and other pathologies involving the colon.

BACKGROUND & AIMS: Aberrant DNA methylation is frequent in colorectal cancer (CRC), but underlying mechanisms and pathologic consequences are poorly understood.METHODS: We disrupted active DNA demethylation genes Tet1 and/or Tdg from ApcMin mice and characterized the methylome and tran-scriptome of colonic adenomas. Data were compared to human colonic adenocarcinomas (COAD) in The Cancer Genome Atlas.RESULTS: There were increased numbers of small intestinal adenomas in ApcMin mice expressing the TdgN151A allele, whereas Tet1-deficient and Tet1/TdgN151A-double heterozy-gous ApcMin colonic adenomas were larger with features of erosion and invasion. We detected reduction in global DNA hypomethylation in colonic adenomas from Tet1-and Tdg- mutant ApcMin mice and hypermethylation of CpG islands in Tet1-mutant ApcMin adenomas. Up-regulation of inflammatory, immune, and interferon response genes was present in Tet1- and Tdg-mutant colonic adenomas compared to control ApcMin adenomas. This up-regulation was also seen in murine colonic organoids and human CRC lines infected with lentiviruses expressing TET1 or TDG short hairpin RNA. A 127-gene in-flammatory signature separated colonic adenocarcinomas into 4 groups, closely aligned with their microsatellite or chromo-somal instability and characterized by different levels of DNA methylation and DNMT1 expression that anticorrelated with TET1 expression. Tumors with the CpG island methylator phenotype (CIMP) had concerted high DNMT1/low TET1 expression. TET1 or TDG knockdown in CRC lines enhanced killing by natural killer cells. CONCLUSIONS: Our findings reveal a novel epigenetic regulation, linked to the type of genomic instability, by which TET1/TDG-mediated DNA demethylation decreases methylation levels and inflammatory/ interferon/immune responses. CIMP in CRC is triggered by an imbalance of methylating activities over demethylating activ-ities. These mice represent a model of CIMP CRC.

Hepatocellular carcinoma (HCC) is the most common form of liver cancer with poor survival and limited therapeutic options. HCC development is accompanied by underlying chronic inflammation, which represents a major unifying mechanism for tumor promotion. While some tumor-promoting inflammatory mechanisms had been proposed, the identity of immune mechanisms controlling anti-cancer immunity in HCC remain poorly understood. Interleukin (IL)-27 receptor signaling plays an anti-inflammatory role in a variety of infectious and chronic inflammatory diseases. Here, using genetic and pharmacological approaches we found that IL-27 receptor (IL-27R) signaling promotes HCC development in vivo. Genetic loss of IL-27R suppressed HCC in both carcinogen-induced and non-alcoholic steatohepatitis (NASH)-driven models. Mechanistically, the pro-tumorigenic effect was mediated by an immunoregulatory role of IL-27R within the tumor microenvironment, particularly the suppression of cytotoxic Natural killer (NK) cells. Single-cell RNA analysis further established the role of IL-27R signaling in restraining cytotoxic populations of NK cells. IL-27R ablation enhanced the accumulation and activation of cytotoxic NK cells during acute liver injury and in HCC tumors, while depletion or functional impairment of NK cells abrogated the effect of genetic IL-27R disruption. Taken together, our data suggest an unexpected role of IL-27R signaling as a novel immunological checkpoint regulating innate cytotoxic cell activity and promoting development of HCC of different etiologies. Citation Format: Aleksandra M. Mazitova, Turan Aghayev, Jennifer Fang, Amiran Dzutsev, Giorgio Trinchieri, Kerry S. Campbell, Sergei I. Grivennikov, Ekaterina K. Koltsova. IL-27 signaling regulates anti-cancer immune response in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3130.

Whole-brain radiotherapy (WBRT) is the treatment backbone for many patients with brain metastasis; however, its efficacy in preventing disease progression and the associated toxicity have questioned the clinical impact of this approach and emphasized the need for alternative treatments. Given the limited therapeutic options available for these patients and the poor understanding of the molecular mechanisms underlying the resistance of metastatic lesions to WBRT, we sought to uncover actionable targets and biomarkers that could help to refine patient selection. Through an unbiased analysis of experimental in vivo models of brain metastasis resistant to WBRT, we identified activation of the S100A9-RAGE-NF-κB-JunB pathway in brain metastases as a potential mediator of resistance in this organ. Targeting this pathway genetically or pharmacologically was sufficient to revert the WBRT resistance and increase therapeutic benefits in vivo at lower doses of radiation. In patients with primary melanoma, lung or breast adenocarcinoma developing brain metastasis, endogenous S100A9 levels in brain lesions correlated with clinical response to WBRT and underscored the potential of S100A9 levels in the blood as a noninvasive biomarker. Collectively, we provide a molecular framework to personalize WBRT and improve its efficacy through combination with a radiosensitizer that balances therapeutic benefit and toxicity.

While microbiota regulates immunity and was suggested to play a role in atherosclerosis, the specific role of cytokine signaling in intestinal epithelial cells (IEC) in control of microbiota, inflammation, and vascular disease remains unknown. We previously showed that IL-23 enforces intestinal barrier, controls pro-atherogenic bacteria, metabolites, and activation of myeloid cells, and protects from atherosclerosis. Here we investigate the role of IL-23-regulated IL-17 signaling in IEC using newly generated Ldlr -/- Il17rc fl/fl VillinCre + mice. We found that IEC-specific ablation of IL-17RC heightened subclinical intestinal inflammation, altered microbiota composition, and led to enhanced atherosclerosis development accompanied by accumulation of activated myeloid and T cells in aortas. Mechanistically, IL-17RC ablation in IEC reduced tight junction proteins as well as IgA transport to the lumen due to altered Pigr expression thereby contributing to the expansion of pro-atherogenic microbiota. RNAseq analysis revealed upregulation of multiple inflammatory pathways, including interferon and TLR signaling, while several metabolic pathways such as fatty acid oxidation and pyruvate pathways were downregulated in IL17RC IEC Ldlr -/- mice; implying an important role of IL-17R signaling in the control of IEC and microbial metabolism. Our work uncovers a novel protective role of IEC-specific IL-17 signaling in atherosclerosis and establishes a paradigm of cytokine-mediated regulation of barrier, microbiota, and metabolic pathways in cardiovascular diseases.

TNF and LTα are structurally related cytokines of the TNF superfamily. Their genes are located in close proximity to each other and to the Ltb gene within the TNF/LT locus inside MHC. Unlike Ltb, transcription of Tnf and of Lta is tightly controlled, with the Tnf gene being an immediate early gene that is rapidly induced in response to various inflammatory stimuli. Genes of the TNF/LT locus play a crucial role in lymphoid tissue organogenesis, although some aspects of their specific contribution remain controversial. Here, we present new findings and discuss the distinct contribution of TNF produced by ILC3 cells to Peyer’s patch organogenesis.

Stem cells are fundamental units of tissue remodeling whose functions are dictated by lineage-specific transcription factors. Home to epidermal stem cells and their upward-stratifying progenies, skin relies on its secretory functions to form the outermost protective barrier, of which a transcriptional orchestrator has been elusive. KLF5 is a Krüppel-like transcription factor broadly involved in development and regeneration whose lineage specificity, if any, remains unclear. Here we report KLF5 specifically marks the epidermis, and its deletion leads to skin barrier dysfunction in vivo. Lipid envelopes and secretory lamellar bodies are defective in KLF5-deficient skin, accompanied by preferential loss of complex sphingolipids. KLF5 binds to and transcriptionally regulates genes encoding rate-limiting sphingolipid metabolism enzymes. Remarkably, skin barrier defects elicited by KLF5 ablation can be rescued by dietary interventions. Finally, we found that KLF5 is widely suppressed in human diseases with disrupted epidermal secretion, and its regulation of sphingolipid metabolism is conserved in human skin. Altogether, we established KLF5 as a disease-relevant transcription factor governing sphingolipid metabolism and barrier function in the skin, likely representing a long-sought secretory lineage-defining factor across tissue types.

Colorectal cancer (CRC) is one of the most common cancers, with an annual incidence of ~135,000 in the US, associated with ~ 50,000 deaths. CRC typically arises from mutations that inactivate the tumor suppressor APC, which activates the WNT/CTNNB1 pathway to drive cell transformation and tumor growth. Identifying factors that reduce incidence of CRC is of high interest. Intriguingly, a large population study has found a decreased incidence of CRC in patients with autosomal dominant polycystic kidney disease (ADPKD), an inherited disease affecting approximately 1 in 1,000 individuals. ADPKD typically arises from germline mutations in the PKD1 gene, which encodes a transmembrane signaling protein that is ubiquitously expressed. Puzzlingly, activated WNT/CTNNB1 signaling is also found in ADPKD, which would be expected to enhance rather than reduce likelihood of CRC. To investigate the role of PKD1 in modulating CRC tumorigenesis, we established a mouse model with tamoxifen-inducible loss of Apc with or without parallel loss of Pkd1 in the colon. Pkd1 loss vey significantly reduced tumor incidence (~80%) and rate of growth. In addition, growth of Pkd1-/-;Apc-/- organoids was reduced relative to Apc-/-organoids, indicating a cancer cell-intrinsic activity. Analysis of signaling pathway activation by RNA-seq indicated that Pkd1-deficient CRC organoids had enhanced WNT/CTNNB1 signaling, excluding reduced activation of this core driver pathway as a mechanism of action. Considering alternative mechanisms, a prominent feature of ADPKD is reprogramming barrier function in renal cells to reduce permeability, supporting cyst development; notably, compromised integrity of the epithelial barrier is associated with CRC. We tested the hypothesis that loss of Pkd1 increased colon barrier integrity. As a first approach, we compared susceptibility of wt versus Pkd1-/- mice to dextran-sodium sulfate (DSS), which induces colitis by damaging epithelial barriers. Histopathological assessment confirmed significantly less DSS-induced damage of colon tissue in Pkd1-/- mice. Further, treatment of DSS-treated mice with orally gavaged FITC-dextran led to elevated FITC-dextran in the serum of wt versus Pkd1-/- mice, indicating greater passage through a functionally impaired barrier. In ADPKD, decreased barrier permeability is mediated by upregulation of specific claudins (CLDN4, 7); in CRC, these claudins are typically reduced during and promote tumor formation. We detected strong elevation of CLDN4 and CLDN7 in the colonic epithelium of Pkd1-/- versus wt mice, with the expressed proteins having consistently greater localization to cell junctions. Based on these and other data, we identify PKD1 control of barrier function as an important regulatory mechanism in CRC tumorigenesis, which may suggest novel therapeutic strategies based on targeting PKD1-associated effector pathways. Citation Format: Anna S. Nikonova, Alexander Y. Deneka, Flaviane Silva, Rosella Tricarico, Anna Kiseleva, Sergey Grivennikov, Erica A. Golemis. Loss of Pkd1 limits colorectal cancer by increasing colon barrier function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 940.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by low survival, early metastasis, and rapidly emerging resistance to therapy. Interferon gamma (IFN-γ) signaling pathway is one of the key regulators of the tumor microenvironment in numerous cancer settings and its possible key role in myeloid cells is suggested. Here we investigated the IFN-y signaling in myeloid cells during PDAC development, progression, and metastasis using mice with conditional ablation of IFNgR2 in myeloid cells (IFNgR2-Delta-Mye). We performed an orthotopical injection of cells derived from conditional murine pancreatic model (Pdx1Cre-Kras-P53, or “KPC” cells) into IFNgR2-LysMCre (IFNgR2-Delta-Mye) mice. Ablation of IFN-γ signaling in myeloid cells led to a higher tumor burden compared to controls. Subsequent RNA sequence analysis demonstrated that IFN-γR2 deficiency in myeloid cells resulted in increased TGFβ1 gene expression as well as changes in metabolic and growth factor pathways in macrophages isolated from tumor tissue. Immunofluorescent analysis demonstrated that IFN-γR2 deletion in myeloid cells led to changes in cancer cell differentiation, resulting in a loss of characteristic epithelial histological pattern and shifting it towards more aggressive phenotype, possible via TGFβ1 dependent mechanism. Using murine model of liver metastasis, we found that loss of IFN-γR2 in myeloid cells leads to increased metastatic outgrowth of PDAC KPC cells. This effect was partially dependent on the gut microbiota, as shown by “separated and co-housed mice” experiments. Deficiency of IFN-γR2 in myeloid cells resulted in increased recruitment and infiltration of monocytes in normal and tumor/metastatic liver tissues. Our data identifies myeloid cell type specific IFN-γ signaling pathway as an important regulator of pancreatic cancer progression and metastasis, that can be potentially exploited as a novel immunooncology target. Citation Format: Elena Ivleva, Natalia Andreeva, Sergei Grivennikov. IFN-γ signaling in myeloid cells regulates pancreatic cancer growth and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2117.