Recent studies have demonstrated dramatic shifts in metabolic supply-and-demand ratios during inflammation, a process resulting in localized tissue hypoxia within inflammatory lesions ("inflammatory hypoxia"). As part of the adaptive immune response, T cells are recruited to sites of inflammatory hypoxia. Given the profound effects of hypoxia on gene regulation, we hypothesized that T-cell differentiation is controlled by hypoxia. To pursue this hypothesis, we analyzed the transcriptional consequences of ambient hypoxia (1% oxygen) on a broad panel of T-cell differentiation factors. Surprisingly, these studies revealed selective, robust induction of FoxP3, a key transcriptional regulator for regulatory T cells (Tregs). Studies of promoter binding or loss-and gain-of-function implicated hypoxia-inducible factor (HIF)-1α in inducing FoxP3. Similarly, hypoxia enhanced Treg abundance in vitro and in vivo. Finally, Treg-intrinsic HIF-1α was required for optimal Treg function and Hif1a-deficient Tregs failed to control T-cell-mediated colitis. These studies demonstrate that hypoxia is an intrinsic molecular cue that promotes FoxP3 expression, in turn eliciting potent antiinflammatory mechanisms to limit tissue damage in conditions of reduced oxygen availability.lymphocyte | metabolism | TGF-beta

Human papillomaviruses (HPVs) are small DNA viruses causally associated with benign warts and multiple cancers, including cervical and head-and-neck cancers. While the vast majority of people are exposed to HPV, most instances of infection are cleared naturally. However, the intrinsic host defense mechanisms that block the early establishment of HPV infections remain mysterious. Several antiviral cytidine deaminases of the human APOBEC3 (hA3) family have been identified as potent viral DNA mutators. While editing of HPV genomes in benign and premalignant cervical lesions has been demonstrated, it remains unclear whether hA3 proteins can directly inhibit HPV infection. Interestingly, recent studies revealed that HPV-positive cervical and head-and-neck cancers exhibited higher rates of hA3 mutation signatures than most HPV-negative cancers. Here, we report that hA3A and hA3B expression levels are highly upregulated in HPV-positive keratinocytes and cervical tissues in early stages of cancer progression, potentially through a mechanism involving the HPV E7 oncoprotein. HPV16 virions assembled in the presence of hA3A, but not in the presence of hA3B or hA3C, have significantly decreased infectivity compared to HPV virions assembled without hA3A or with a catalytically inactive mutant, hA3A/E72Q. Importantly, hA3A knockdown in human keratinocytes results in a significant increase in HPV infectivity. Collectively, our findings suggest that hA3A acts as a restriction factor against HPV infection, but the induction of this restriction mechanism by HPV may come at a cost to the host by promoting cancer mutagenesis. IMPORTANCEHuman papillomaviruses (HPVs) are highly prevalent and potent human pathogens that cause >5% of all human cancers, including cervical and head-and-neck cancers. While the majority of people become infected with HPV, only 10 to 20% of infections are established as persistent infections. This suggests the existence of intrinsic host defense mechanisms that inhibit viral persistence. Using a robust method to produce infectious HPV virions, we demonstrate that hA3A, but not hA3B or hA3C, can significantly inhibit HPV infectivity. Moreover, hA3A and hA3B were coordinately induced in HPV-positive clinical specimens during cancer progression, likely through an HPV E7 oncoprotein-dependent mechanism. Interestingly, HPV-positive cervical and head-and-neck cancer specimens were recently shown to harbor significant amounts of hA3 mutation signatures. Our findings raise the intriguing possibility that the induction of this host restriction mechanism by HPV may also trigger hA3A-and hA3B-induced cancer mutagenesis. Human papillomaviruses (HPVs) are small, nonenveloped DNA viruses known as one of the most prevalent sexually transmitted pathogens. Among almost 200 different genotypes, ϳ24 high-risk HPV genotypes are causally associated with multiple human cancers, including nearly all cervical cancers and a portion of head-and-neck squamous cell carcinomas (1). From 1988 to 2004, the incidence of HPV-associ...

BackgroundInflammatory bowel diseases, encompassing Crohn's disease and ulcerative colitis, are characterised by persistent leucocyte tissue infiltration leading to perpetuation of an inappropriate inflammatory cascade. The neuronal guidance molecule netrin-1 has recently been implicated in the orchestration of leucocyte trafficking during acute inflammation. We therefore hypothesised that netrin-1 could modulate leucocyte infiltration and disease activity in a model of inflammatory bowel disease.DesignDSS-colitis was performed in mice with partial genetic netrin-1 deficiency (Ntn-1+/− mice) or wild-type mice treated with exogenous netrin-1 via osmotic pump to examine the role of endogenous and therapeutically administered netrin-1. These studies were supported by in vitro models of transepithelial migration and intestinal epithelial barrier function.ResultsConsistent with our hypothesis, we observed induction of netrin-1 during intestinal inflammation in vitro or in mice exposed to experimental colitis. Moreover, mice with partial netrin-1 deficiency demonstrated an exacerbated course of DSS-colitis compared to littermate controls, with enhanced weight loss and colonic shortening. Conversely, mice treated with exogenous mouse netrin-1 experienced attenuated disease severity. Importantly, permeability studies and quantitative assessment of apoptosis reveal that netrin-1 signalling events do not alter mucosal permeability or intestinal epithelial cell apoptosis. In vivo studies of leucocyte transmigration demonstrate suppression of neutrophil trafficking as a key function mediated by endogenous or exogenously administered netrin-1. Finally, genetic studies implicate the A2B adenosine receptor in netrin-1-mediated protection during DSS-colitis.ConclusionsThe present study identifies a previously unrecognised role for netrin-1 in attenuating experimental colitis through limitation of neutrophil trafficking.

A majority of human papillomavirus (HPV) infections are asymptomatic and self-resolving in the absence of medical interventions. Various innate and adaptive immune responses, as well as physical barriers, have been implicated in controlling early HPV infections. However, if HPV overcomes these host immune defenses and establishes persistence in basal keratinocytes, it becomes very difficult for the host to eliminate the infection. The HPV oncoproteins E5, E6, and E7 are important in regulating host immune responses. These oncoproteins dysregulate gene expression, protein-protein interactions, posttranslational modifications, and cellular trafficking of critical host immune modulators. In addition to the HPV oncoproteins, sequence variation and dinucleotide depletion in papillomavirus genomes has been suggested as an alternative strategy for evasion of host immune defenses. Since anti-HPV host immune responses are also considered to be important for antitumor immunity, immune dysregulation by HPV during virus persistence may contribute to immune suppression essential for HPV-associated cancer progression. Here, we discuss cellular pathways dysregulated by HPV that allow the virus to evade various host immune defenses.

High-risk human papillomaviruses (HPVs) are causally associated with multiple human cancers. Previous studies have shown that the HPV oncoprotein E7 induces immune suppression; however, the underlying mechanisms remain unknown. To understand the mechanisms by which HPV deregulates host immune responses in the tumor microenvironment, we analyzed gene expression changes of all known chemokines and their receptors using our global gene expression data sets from human HPV-positive and -negative head/neck cancer and cervical tissue specimens in different disease stages. We report that, while many proinflammatory chemokines increase expression throughout cancer progression, CXCL14 is dramatically downregulated in HPV-positive cancers. HPV suppression of CXCL14 is dependent on E7 and associated with DNA hypermethylation in the CXCL14 promoter. Using in vivo mouse models, we revealed that restoration of Cxcl14 expression in HPV-positive mouse oropharyngeal carcinoma cells clears tumors in immunocompetent syngeneic mice, but not in Rag1-deficient mice. Further, Cxcl14 reexpression significantly increases natural killer (NK), CD4+ T, and CD8+ T cell infiltration into the tumor-draining lymph nodes in vivo. In vitro transwell migration assays show that Cxcl14 reexpression induces chemotaxis of NK, CD4+ T, and CD8+ T cells. These results suggest that CXCL14 downregulation by HPV plays an important role in suppression of antitumor immune responses. Our findings provide a new mechanistic understanding of virus-induced immune evasion that contributes to cancer progression.