Control of T(H)17/T(reg) balance by hypoxia-inducible factor 1.

T cell differentiation into distinct functional effector and inhibitory subsets is regulated, in part, by the cytokine environment present at the time of antigen recognition. Here, we show that hypoxia-inducible factor 1 (HIF-1), a key metabolic sensor, regulates the balance between regulatory T cell (T(reg)) and T(H)17 differentiation. HIF-1 enhances T(H)17 development through direct transcriptional activation of RORγt and via tertiary complex formation with RORγt and p300 recruitment to the IL-17 promoter, thereby regulating T(H)17 signature genes. Concurrently, HIF-1 attenuates T(reg) development by binding Foxp3 and targeting it for proteasomal degradation. Importantly, this regulation occurs under both normoxic and hypoxic conditions. Mice with HIF-1α-deficient T cells are resistant to induction of T(H)17-dependent experimental autoimmune encephalitis associated with diminished T(H)17 and increased T(reg) cells. These findings highlight the importance of metabolic cues in T cell fate determination and suggest that metabolic modulation could ameliorate certain T cell-based immune pathologies.

MicroRNA-17 Modulates Regulatory T Cell Function by Targeting Co-regulators of the Foxp3 Transcription Factor.

Regulatory T (Treg) cells are important in maintaining self-tolerance and immune homeostasis. The Treg cell transcription factor Foxp3 works in concert with other co-regulatory molecules, including Eos, to determine the transcriptional signature and characteristic suppressive phenotype of Treg cells. Here, we report that the inflammatory cytokine interleukin-6 (IL-6) actively repressed Eos expression through microRNA-17 (miR-17). miR-17 expression increased in Treg cells in the presence of IL-6, and its expression negatively correlated with that of Eos. Treg cell suppressive activity was diminished upon overexpression of miR-17 in vitro and in vivo, which was mitigated upon co-expression of an Eos mutant lacking miR-17 target sites. Also, RNAi of miR-17 resulted in enhanced suppressive activity. Ectopic expression of miR-17 imparted effector-T-cell-like characteristics to Treg cells via the de-repression of genes encoding effector cytokines. Thus, miR-17 provides a potent layer of Treg cell control through targeting Eos and additional Foxp3 co-regulators.

TRAF6 directs FOXP3 localization and facilitates regulatory T-cell function through K63-linked ubiquitination.

Regulatory T cells (Tregs) are crucial mediators of immune control. The characteristic gene expression and suppressive functions of Tregs depend considerably on the stable expression and activity of the transcription factor FOXP3. Transcriptional regulation of the Foxp3 gene has been studied in depth, but both the expression and function of this factor are also modulated at the protein level. However, the molecular players involved in posttranslational FOXP3 regulation are just beginning to be elucidated. Here, we found that TRAF6-deficient Tregs were dysfunctional in vivo; mice with Treg-restricted deletion of TRAF6 were resistant to implanted tumors and displayed enhanced anti-tumor immunity. We further determined that FOXP3 undergoes K63-linked ubiquitination at lysine 262 mediated by the E3 ligase TRAF6. In the absence of TRAF6 activity or upon mutation of the ubiquitination site, FOXP3 displayed aberrant, perinuclear accumulation and disrupted regulatory function. Thus, K63-linked ubiquitination by TRAF6 ensures proper localization of FOXP3 and facilitates the transcription factor's gene-regulating activity in Tregs. These results implicate TRAF6 as a key posttranslational, Treg-stabilizing regulator that may be targeted in novel tolerance-breaking therapies.

Skeletal muscle index is associated with long term outcomes after lobectomy for non-small cell lung cancer.

BACKGROUND: Skeletal muscle indices have been associated with improved peri-operative outcomes after surgical resection of non-small-cell lung cancer (NSCLC). However, it is unclear if these indices can predict long term cancer specific outcomes. METHODS: NSCLC patients undergoing lobectomy at our institute between 2009-2015 were included in this analysis (N = 492). Preoperative CT scans were used to quantify skeletal muscle index (SMI) at L4 using sliceOmatic software. Cox proportional modelling was performed for overall (OS) and recurrence free survival (RFS). RESULTS: For all patients, median SMI was 45.7 cm2/m2 (IQR, 40-53.8). SMI was negatively associated with age (R = -0.2; p < 0.05) and positively associated with BMI (R = 0.46; P < 0.05). No association with either OS or RFS was seen with univariate cox modelling. However, multivariable modelling for SMI with patient age, gender, race, smoking status, DLCO and FEV1 (% predicted), American Society of Anesthesiology (ASA) score, tumor histology and stage, and postoperative neoadjuvant therapy showed improved OS (HR = 0.97; P = 0.0005) and RFS (HR = 0.97; P = 0.01) with SMI. Using sex specific median SMI as cutoff, a lower SMI was associated with poor OS (HR = 1.65, P = 0.001) and RFS (HR = 1.47, P = 0.03). CONCLUSIONS: SMI is associated with improved outcomes after resection of NSCLC. Further studies are needed to understand the biological basis of this observation. This study provides additional rationale for designing and implementation of rehabilitation trials after surgical resection, to gain durable oncologic benefit.

Stabilization of the transcription factor Foxp3 by the deubiquitinase USP7 increases Treg-cell-suppressive capacity.

Stable Foxp3 expression is required for the development of functional regulatory T (Treg) cells. Here, we demonstrate that the expression of the transcription factor Foxp3 can be regulated through the polyubiquitination of multiple lysine residues, resulting in proteasome-mediated degradation. Expression of the deubiquitinase (DUB) USP7 was found to be upregulated and active in Treg cells, being associated with Foxp3 in the nucleus. Ectopic expression of USP7 decreased Foxp3 polyubiquitination and increased Foxp3 expression. Conversely, either treatment with DUB inhibitor or USP7 knockdown decreased endogenous Foxp3 protein expression and decreased Treg-cell-mediated suppression in vitro. Furthermore, in a murine adoptive-transfer-induced colitis model, either inhibition of DUB activity or USP7 knockdown in Treg cells abrogated their ability to resolve inflammation in vivo. Our data reveal a molecular mechanism in which rapid temporal control of Foxp3 expression in Treg cells can be regulated by USP7, thereby modulating Treg cell numbers and function.

The ubiquitin ligase Stub1 negatively modulates regulatory T cell suppressive activity by promoting degradation of the transcription factor Foxp3.

Regulatory T (Treg) cells suppress inflammatory immune responses and autoimmunity caused by self-reactive T cells. The key Treg cell transcription factor Foxp3 is downregulated during inflammation to allow for the acquisition of effector T cell-like functions. Here, we demonstrate that stress signals elicited by proinflammatory cytokines and lipopolysaccharides lead to the degradation of Foxp3 through the action of the E3 ubiquitin ligase Stub1. Stub1 interacted with Foxp3 to promote its K48-linked polyubiquitination in an Hsp70-dependent manner. Knockdown of endogenous Stub1 or Hsp70 prevented Foxp3 degradation. Furthermore, the overexpression of Stub1 in Treg cells abrogated their ability to suppress inflammatory immune responses in vitro and in vivo and conferred a T-helper-1-cell-like phenotype. Our results demonstrate the critical role of the stress-activated Stub1-Hsp70 complex in promoting Treg cell inactivation, thus providing a potential therapeutic target for the intervention against autoimmune disease, infection, and cancer.

The deubiquitinase USP44 promotes Treg function during inflammation by preventing FOXP3 degradation.

The transcription factor forkhead box P3 (FOXP3) is essential for the development of regulatory T cells (Tregs) and their function in immune homeostasis. Previous studies have shown that in natural Tregs (nTregs), FOXP3 can be regulated by polyubiquitination and deubiquitination. However, the molecular players active in this pathway, especially those modulating FOXP3 by deubiquitination in the distinct induced Treg (iTreg) lineage, remain unclear. Here, we identify the ubiquitin-specific peptidase 44 (USP44) as a novel deubiquitinase for FOXP3. USP44 interacts with and stabilizes FOXP3 by removing K48-linked ubiquitin modifications. Notably, TGF-ß induces USP44 expression during iTreg differentiation. USP44 co-operates with USP7 to stabilize and deubiquitinate FOXP3. Tregs genetically lacking USP44 are less effective than their wild-type counterparts, both in vitro and in multiple in vivo models of inflammatory disease and cancer. These findings suggest that USP44 plays an important role in the post-translational regulation of Treg function and is thus a potential therapeutic target for tolerance-breaking anti-cancer immunotherapy.

Ubiquitin-dependent regulation of Foxp3 and Treg function.

Regulatory T (Treg) cells are crucial enforcers of immune homeostasis. Their characteristic suppressive function largely arises from an equally unique pattern of gene expression. A complex network of factors and processes contribute to this 'signature' Treg gene expression landscape. Many of these alter the level and activity of the Treg-defining transcription factor Foxp3. As stable expression of Foxp3 is important for the ability of Treg cells to successfully prevent excessive or inappropriate immune activation, uncovering the mechanisms regulating Foxp3 level is required for the understanding and therapeutic exploitation of Tregs. While transcriptional regulation of the Foxp3 gene has been studied in depth, additional regulatory layers exist controlling the expression and activity of this key transcription factor. These include less-defined mechanisms active at the post-translational level. These pathways are just beginning to be elucidated. Here, we summarize emerging evidence for distinct, post-translationally active, ubiquitin-dependent pathways capable of controlling the activation and expression of Foxp3 and the function of Tregs. These pathways offer untapped opportunities for therapeutic fine-tuning of Tregs and their all-important restraint of the immune system.

Treg functional stability and its responsiveness to the microenvironment.

Regulatory T cells (Tregs) prevent autoimmunity and tissue damage resulting from excessive or unnecessary immune activation through their suppressive function. While their importance for proper immune control is undeniable, the stability of the Treg lineage has recently become a controversial topic. Many reports have shown dramatic loss of the signature Treg transcription factor Forkhead box protein 3 (Foxp3) and Treg function under various inflammatory conditions. Other recent studies demonstrate that most Tregs are extremely resilient in their expression of Foxp3 and the retention of suppressive function. While this debate is unlikely to be settled in the immediate future, improved understanding of the considerable heterogeneity within the Foxp3(+) Treg population and how Treg subsets respond to ranging environmental cues may be keys to reconciliation. In this review, we discuss the diverse mechanisms responsible for the observed stability or instability of Foxp3(+) Treg identity and function. These include transcriptional and epigenetic programs, transcript targeting, and posttranslational modifications that appear responsive to numerous elements of the microenvironment. These mechanisms for Treg functional modulation add to the discussion of Treg stability.

Metabolic Regulation of T Cell Immunity.

It is becoming increasingly clear that cellular metabolism plays a critical role in the propagation of appropriate, effective, and pathologic immune responses. In this chapter, we detail the metabolic pathways involved in T cell activation and differentiation, highlighting specific factors responsible for directing the processes that lead to metabolic programming at important stages in the dynamic life cycle of this immune cell lineage. Additionally, this chapter will discuss how key metabolites are acquired, touching on the factors and conditions regulating the expression of crucial transporter molecules in response to activation and pathological states.

Metabolic control of the Treg/Th17 axis.

The interplay of the immune system with other aspects of physiology is continually being revealed and in some cases studied in considerable mechanistic detail. A prime example is the influence of metabolic cues on immune responses. It is well appreciated that upon activation, T cells take on a metabolic profile profoundly distinct from that of their quiescent and anergic counterparts; however, a number of recent breakthroughs have greatly expanded our knowledge of how aspects of cellular metabolism can shape a T-cell response. Particularly important are findings that certain environmental cues can tilt the delicate balance between inflammation and immune tolerance by skewing T-cell fate decisions toward either the T-helper 17 (Th17) or T-regulatory (Treg) cell lineage. Recognizing the unappreciated immune-modifying potential of metabolic factors and particularly those involved in the generation of these functionally opposing T-cell subsets will likely add new and potent therapies to our repertoire for treating immune mediated pathologies. In this review, we summarize and discuss recent findings linking certain metabolic pathways, enzymes, and by-products to shifts in the balance between Th17 and Treg cell populations. These advances highlight numerous opportunities for immune modulation.

Hypoxia-inducible factors in T lymphocyte differentiation and function. A Review in the Theme: Cellular Responses to Hypoxia.

Low oxygen concentrations or hypoxia is a trait common to inflamed tissues. Therefore it is not surprising that pathways of hypoxic stress response, largely governed by hypoxia-inducible factors (HIF), are highly relevant to the proper function of immune cells. HIF expression and stabilization in immune cells can be triggered not only by hypoxia, but also by a variety of stimuli and pathological stresses associated with leukocyte activation and inflammation. In addition to its role as a sensor of oxygen scarcity, HIF is also a major regulator of immune cell metabolic function. Rapid progress is being made in elucidating the roles played by HIF in diverse aspects of both innate and adaptive immunity. Here we discuss a number of breakthroughs that have shed light on how HIF expression and activity impact the differentiation and function of diverse T cell populations. The insights gained from these findings may serve as the foundation for future therapies aimed at fine-tuning the immune response.

Critical role for phosphoinositide 3-kinase gamma in parasite invasion and disease progression of cutaneous leishmaniasis.

Obligate intracellular pathogens such as Leishmania specifically target host phagocytes for survival and replication. Phosphoinositide 3-kinase γ (PI3Kγ), a member of the class I PI3Ks that is highly expressed by leukocytes, controls cell migration by initiating actin polymerization and cytoskeletal reorganization, which are processes also critical for phagocytosis. In this study, we demonstrate that class IB PI3K, PI3Kγ, plays a critical role in pathogenesis of chronic cutaneous leishmaniasis caused by L. mexicana. Using the isoform-selective PI3Kγ inhibitor, AS-605240 and PI3Kγ gene-deficient mice, we show that selective blockade or deficiency of PI3Kγ significantly enhances resistance against L. mexicana that is associated with a significant suppression of parasite entry into phagocytes and reduction in recruitment of host phagocytes as well as regulatory T cells to the site of infection. Furthermore, we demonstrate that AS-605240 is as effective as the standard antileishmanial drug sodium stibogluconate in treatment of cutaneous leishmaniasis caused by L. mexicana. These findings reveal a unique role for PI3Kγ in Leishmania invasion and establishment of chronic infection, and demonstrate that therapeutic targeting of host pathways involved in establishment of infection may be a viable strategy for treating infections caused by obligate intracellular pathogens such as Leishmania.

Pentalinon andrieuxii root extract is effective in the topical treatment of cutaneous leishmaniasis caused by Leishmania mexicana.

Cutaneous leishmaniasis (CL) manifests as localized skin lesions, which lead to significant tissue destruction and disfigurement. In the Yucatan Peninsula, Mayan traditional healers use Pentalinon andrieuxii Muell.-Arg. (Apocynaceae) roots for the topical treatment of CL. Here, we studied the effect of P. andrieuxii root hexane extract (PARE) on the parasites and host cells in vitro and examined its efficacy in the topical treatment of CL caused by Leishmania mexicana. PARE exhibited potent antiparasitic activity in vitro against promastigotes as well as amastigotes residing in macrophages. Electron microscopy of PARE-treated parasites revealed direct membrane damage. PARE also activated nuclear factor kappaB and enhanced interferon-γ receptor and MHC class II expression and TNF-α production in macrophages. In addition, PARE induced production of the Th1 promoting cytokine IL-12 in dendritic cells as well as enhanced expression of the co-stimulatory molecules CD40, CD80, and CD86. In vivo studies showed that L. mexicana-infected mice treated by topical application of PARE resulted in the significant reduction in lesion size and parasite burden compared to controls. These findings indicate that PARE could be used as an alternative therapy for the topical treatment of CL.

A Senescence-Mimicking (Senomimetic) VEGFR TKI Side Effect Primes Tumor Immune Responses via IFN/STING Signaling.

Tyrosine kinase inhibitors (TKIs) that block the vascular endothelial growth factor receptors (VEGFRs) not only disrupt tumor angiogenesis but also have many unexpected side effects that impact tumor cells directly. This includes the induction of molecular markers associated with senescence, a form of cellular aging that typically involves growth arrest. We have shown that VEGFR TKIs can hijack these aging programs by transiently inducting senescence markers (SMs) in tumor cells to activate senescence-associated secretory programs that fuel drug resistance. Here we show that these same senescence-mimicking ("senomimetic") VEGFR TKI effects drive an enhanced immunogenic signaling that, in turn, can alter tumor response to immunotherapy. By using a live cell sorting method to detect ß-galactosidase, a commonly used SM, we found that subpopulations of SM-expressing (SM+) tumor cells have heightened IFN signaling and increased expression of IFN-stimulated genes (ISGs). These ISGs increase under the control of the STimulator of the INterferon Gene (STING) signaling pathway, which we found could be directly activated by several VEGFR TKIs. TKI-induced SM+ cells could stimulate or suppress CD8 T-cell activation depending on host-tumor cell contact while tumors grown from SM+ cells were more sensitive to PDL1 inhibition in vivo, suggesting that offsetting immune-suppressive functions of SM+ cells can improve TKI efficacy overall. Our findings may explain why some (but not all) VEGFR TKIs improve outcomes when combined with immunotherapy and suggest that exploiting senomimetic drug side effects may help identify TKIs that uniquely "prime" tumors for enhanced sensitivity to PDL1-targeted agents.

Sex-based Differences in the Lung Immune Microenvironment Are Associated with an Increased Risk of Lung Cancer in Women.

OBJECTIVE: Lung cancer remains a major cause of mortality worldwide, necessitating further understanding of carcinogenesis and its driving factors, including those impacted by sex-dependent variables. We hypothesized that sex-specific lung immune composition may contribute to a greater risk of lung cancer in females. METHODS: Data from 1056 lung cancer screenings were examined for an association between sex and lung cancer risk using time-to-event analyses. Immune profiling by flow cytometry was performed on male and female lungs of three independent mouse models: non-tumor bearing, K-ras mutated, and urethane-exposed carcinogenic. A comparable analysis was performed on human bronchoalveolar lavage samples (n = 81) from lung cancer patients. RESULTS: Of the high-risk screening cohort examined, 60 patients (5.7%) developed lung cancer during median follow-up of 43.4 months. Multivariable stepwise modeling retained female sex (hazard ratio 1.56, P < 0.01) and age (P < 0.01) as prognostic indicators for lung cancer development. Female lung immune profiles in patients included T cell phenotypes consistent with exhaustion (e.g., higher proportions of PD-1+ Ki67-; P = 0.02), an expanded pool of regulatory T cells (P = 0.03), reduced effector T cell frequencies (P = 0.008), and enhancements in suppressive myeloid populations (P = 0.02) versus males, and this is recapitulated in mouse studies. CONCLUSIONS: Female smokers display higher risk for lung cancer. In murine models and humans, female sex is associated with robust immunosuppression within the lung. Further examination of this link will be important in developing immune-based approaches to lung cancer interception and their optimal application across the sexes.

A senescence-mimicking (senomimetic) VEGFR TKI side-effect primes tumor immune responses via IFN/STING signaling.

Tyrosine kinase inhibitors (TKIs) that block the vascular endothelial growth factor receptors (VEGFRs) disrupt tumor angiogenesis but also have many unexpected side-effects that impact tumor cells directly. This includes the induction of molecular markers associated with senescence, a form of cellular aging that typically involves growth arrest. We have shown that VEGFR TKIs can hijack these aging programs by transiently inducting senescence-markers (SMs) in tumor cells to activate senescence-associated secretory programs that fuel drug resistance. Here we show that these same senescence-mimicking ('senomimetic') VEGFR TKI effects drive an enhanced immunogenic signaling that, in turn, can alter tumor response to immunotherapy. Using a live-cell sorting method to detect beta-galactosidase, a commonly used SM, we found that subpopulations of SM-expressing (SM+) tumor cells have heightened interferon (IFN) signaling and increased expression of IFN-stimulated genes (ISGs). These ISG increases were under the control of the STimulator of INterferon Gene (STING) signaling pathway, which we found could be directly activated by several VEGFR TKIs. TKI-induced SM+ cells could stimulate or suppress CD8 T-cell activation depending on host:tumor cell contact while tumors grown from SM+ cells were more sensitive to PD-L1 inhibition in vivo, suggesting that offsetting immune-suppressive functions of SM+ cells can improve TKI efficacy overall. Our findings may explain why some (but not all) VEGFR TKIs improve outcomes when combined with immunotherapy and suggest that exploiting senomimetic drug side-effects may help identify TKIs that uniquely 'prime' tumors for enhanced sensitivity to PD-L1 targeted agents.

Neurotrophic factor Neuritin modulates T cell electrical and metabolic state for the balance of tolerance and immunity.

The adaptive T cell response is accompanied by continuous rewiring of the T cell's electric and metabolic state. Ion channels and nutrient transporters integrate bioelectric and biochemical signals from the environment, setting cellular electric and metabolic states. Divergent electric and metabolic states contribute to T cell immunity or tolerance. Here, we report that neuritin (Nrn1) contributes to tolerance development by modulating regulatory and effector T cell function. Nrn1 expression in regulatory T cells promotes its expansion and suppression function, while expression in the T effector cell dampens its inflammatory response. Nrn1 deficiency causes dysregulation of ion channel and nutrient transporter expression in Treg and effector T cells, resulting in divergent metabolic outcomes and impacting autoimmune disease progression and recovery. These findings identify a novel immune function of the neurotrophic factor Nrn1 in regulating the T cell metabolic state in a cell context-dependent manner and modulating the outcome of an immune response.

Neoadjuvant therapy in non-small cell lung cancer: basis, promise, and challenges.

Introduction: Survival rates for early-stage non-small cell lung cancer (NSCLC) remain poor despite the decade-long established standard of surgical resection and systemic adjuvant therapy. Realizing this, researchers are exploring novel therapeutic targets and deploying neoadjuvant therapies to predict and improve clinical and pathological outcomes in lung cancer patients. Neoadjuvant therapy is also increasingly being used to downstage disease to allow for resection with a curative intent. In this review, we aim to summarize the current and developing landscape of using neoadjuvant therapy in the management of NSCLC. Methods: The PubMed.gov and the ClinicalTrials.gov databases were searched on 15 January 2023, to identify published research studies and trials relevant to this review. One hundred and seven published articles and seventeen ongoing clinical trials were selected, and relevant findings and information was reviewed. Results & Discussion: Neoadjuvant therapy, proven through clinical trials and meta-analyses, exhibits safety and efficacy comparable to or sometimes surpassing adjuvant therapy. By attacking micro-metastases early and reducing tumor burden, it allows for effective downstaging of disease, allowing for curative surgical resection attempts. Research into neoadjuvant therapy has necessitated the development of surrogate endpoints such as major pathologic response (MPR) and pathologic complete response (pCR) allowing for shorter duration clinical trials. Novel chemotherapy, immunotherapy, and targeted therapy agents are being tested at a furious rate, paving the way for a future of personalized systemic therapy in NSCLC. However, challenges remain that prevent further mainstream adoption of preoperative (Neoadjuvant) therapy. These include the risk of delaying curative surgical resection in scenarios of adverse events or treatment resistance. Also, the predictive value of surrogate markers of disease cure still needs robust verification. Finally, the body of published data is still limited compared to adjuvant therapy. Addressing these concerns with more large scale randomized controlled trials is needed.

Immunoprofiling bronchoalveolar lavage cells reveals multifaceted smoking-associated immune dysfunction.

Background: Bronchoalveolar lavage (BAL) is an underutilised tool in the search for pulmonary disease biomarkers. While leukocytes with effector and suppressor function play important roles in airway immunity and tumours, it remains unclear if frequencies and phenotypes of BAL leukocytes can be useful parameters in lung cancer studies and clinical trials. We therefore explored the utility of BAL leukocytes as a source of biomarkers interrogating the impact of smoking, a major lung cancer risk determinant, on pulmonary immunity. Methods: In this "test case" observational study, BAL samples from 119 donors undergoing lung cancer screening and biopsy procedures were evaluated by conventional and spectral flow cytometry to exemplify the comprehensive immune analyses possible with this biospecimen. Proportions of major leukocyte populations and phenotypic markers levels were found. Multivariate linear rank sum analysis considering age, sex, cancer diagnosis and smoking status was performed. Results: Significantly increased frequencies of myeloid-derived suppressor cells and PD-L1-expressing macrophages were found in current and former smokers compared to never-smokers. While cytotoxic CD8 T-cells and conventional CD4 helper T-cell frequencies were significantly reduced in current and former smokers, expression of immune checkpoints PD-1 and LAG-3 as well as Tregs proportions were increased. Lastly, the cellularity, viability and stability of several immune readouts under cryostorage suggested BAL samples are useful for correlative end-points in clinical trials. Conclusions: Smoking is associated with heightened markers of immune dysfunction, readily assayable in BAL, that may reflect a permissive environment for cancer development and progression in the airway.