The role of barrier function, autophagy, and cytokines in maintaining intestinal homeostasis

Intestinal homeostasis is maintained through the interplay of the intestinal mucosa, local and systemic immune factors, and the microbial content of the gut. The cellular processes of autophagy, endoplasmic reticulum stress, the unfolded protein response and regulation of reactive oxygen species production are required to maintain a balance between pro-inflammatory responses against potential pathogens and a tolerogenic response towards commensal bacteria. Intestinally active cytokines regulate innate immune pathways and cellular pathways within the gut mucosa. Disruption of these processes, or alterations in the cytokine milieu, can result in an improper response to the commensal gut microbial community leading to inappropriate inflammation characteristic of conditions such as inflammatory bowel disease.

Cancers from Novel Pole-Mutant Mouse Models Provide Insights into Polymerase-Mediated Hypermutagenesis and Immune Checkpoint Blockade

POLE mutations are a major cause of hypermutant cancers, yet questions remain regarding mechanisms of tumorigenesis, genotype-phenotype correlation, and therapeutic considerations. In this study, we establish mouse models harboring cancer-associated POLE mutations P286R and S459F, which cause rapid albeit distinct time to cancer initiation in vivo, independent of their exonuclease activity. Mouse and human correlates enabled novel stratification of POLE mutations into three groups based on clinical phenotype and mutagenicity. Cancers driven by these mutations displayed striking resemblance to the human ultrahypermutation and specific signatures. Furthermore, Pole-driven cancers exhibited a continuous and stochastic mutagenesis mechanism, resulting in intertumoral and intratumoral heterogeneity. Checkpoint blockade did not prevent Pole lymphomas, but rather likely promoted lymphomagenesis as observed in humans. These observations provide insights into the carcinogenesis of POLE-driven tumors and valuable information for genetic counseling, surveillance, and immunotherapy for patients. SIGNIFICANCE: Two mouse models of polymerase exonuclease deficiency shed light on mechanisms of mutation accumulation and considerations for immunotherapy.See related commentary by Wisdom and Kirsch p. 5459.

Facile synthesis of dendrimer like mesoporous silica nanoparticles to enhance targeted delivery of interleukin-22

Interleukin (IL)-22 is a multifunctional cytokine with a very short half-life that activates STAT3 and can elicit strong anti-inflammatory effects in the intestine but can induce inflammation in other sites. Several long-circulating IL-22 fusion proteins have been manufactured to date; however, those were associated with adverse effects in other organs limiting their utility for treating intestinal inflammation. Targeted delivery of IL-22 to the intestine could utilize its anti-inflammatory properties and overcome systemic toxicity. Therefore, this study aimed to synthesise large pore mesoporous silica nanoparticles (LPMSN), load recombinant (r)IL-22 in the LPMSN and test its bioactivity in the STAT3 reporter LS174T, wild type LS174T, Caco-2 intestinal epithelial cells, and healthy human colonic organoids. Our data showed one hundred percent loading capacity (w/w) of the synthesised LPMSN, which prolonged IL-22 induced STAT3 luciferase activities in LS174T and p-STAT3 immunofluorescence in Caco-2 cells. LPMSN also stabilized and increased the permeability of rIL-22 across Caco-2 monolayers. Moreover, LPMSN-IL-22 retained the functionality of the cytokine in human colonic organoids. Taken together, these data demonstrate the protection and effective delivery of IL-22 using bio-nanomaterials (LPMSN) that could enable targeted oral delivery of this IL-22.

MODL-25. REPLICATION REPAIR DEFICIENT MOUSE MODELS PROVIDE INSIGHT ON HYPERMUTANT BRAIN TUMOURS, MECHANISMS OF IMMUNE EVASION, AND COMBINATORIAL IMMUNOTHERAPY

Replication repair deficiency (RRD) is the leading cause of hypermutant brain tumours in children. RRD is caused by defects in one of four mismatch repair (MMR) genes and mutations in POLE or POLD1. Such tumours are resistant to common therapeutic agents and animal models are needed to study RRD in vivo and test novel therapies like immune checkpoint inhibitors (ICIs). To model RRD brain tumours specifically, we engineered a Pole mutant mouse model harbouring the S459F mutation (Pole^S459F). We combined Pole^S459F mice with conditional Msh2 knockout (Msh2^LoxP) and Nestin-cre mice. All Nestin-cre⁺Msh2^LoxP/LoxPPole^S459F/+ mice rapidly succumbed to posterior fossa brain tumours between 8.6 and 12.4 weeks. Importantly, tumours exhibited hallmark “ultrahypermutation” (~350 mutations/Mb) and the corresponding signatures characteristic of human combined MMR and POLE-proofreading glioblastoma. Interestingly, Nestin-cre⁺Msh2^LoxP/LoxPPole^S459F/S459F mice failed to establish normal cerebella, suggesting such mutational loads may not support normal brain development. Furthermore, OLIG2-cre⁺Msh2^LoxP/LoxPPole^S459F/+ mice failed to develop tumors. Tumors transplanted into syngeneic vs immunocompromised animals egrafted well orthotopically in the mouse hindbrain but significantly less efficiently when engrafted subcutaneously. Furthermore, immunocompromised and subcutaneous tumors revealed striking differences in mutational burden and clonal architecture, suggestive of nonautonomous immunoediting. Finally, anti-PD1 was sufficient to treat subcutaneously engrafted tumors in immunocompetent animals. This first mouse model of immunocompetent, hypermutant brain tumors can be used to uncover unique characteristics of RRD tumour evolution and allow for immune based therapeutic preclinical testing. Experiments to assess combinational ICIs and other therapeutic interventions in orthotopically transplanted tumors will also be presented.