Kristen L. Dennis

T-Regulatory Cells Shift from a Protective Anti-Inflammatory to a Cancer-Promoting Proinflammatory Phenotype in Polyposis

T-regulatory (Treg) cells play a major role in cancer by suppressing protective antitumor immune responses. A series of observations (from a single laboratory) suggest that Treg cells are protective in cancer by virtue of their ability to control cancer-associated inflammation in an interleukin (IL)-10-dependent manner. Here, we report that the ability of Treg cells to produce IL-10 and control inflammation is lost in the course of progressive disease in a mouse model of hereditary colon cancer. Treg cells that expand in adenomatous polyps no longer produce IL-10 and instead switch to production of IL-17. Aberrant Treg cells from polyp-ridden mice promote rather than suppress focal mastocytosis, a critical tumor-promoting inflammatory response. The cells, however, maintain other Treg characteristics, including their inability to produce IL-2 and ability to suppress proliferation of stimulated CD4 T cells. By promoting inflammation and suppressing T-helper functions, these cells act as a double-edged knife propagating tumor growth.

The significant role of mast cells in cancer

Mast cells (MC) are a bone marrow-derived, long-lived, heterogeneous cellular population that function both as positive and negative regulators of immune responses. They are arguably the most productive chemical factory in the body and influence other cells through both soluble mediators and cell-to-cell interaction. MC are commonly seen in various tumors and have been attributed alternatively with tumor rejection or tumor promotion. Tumor-infiltrating MC are derived both from sentinel and recruited progenitor cells. MC can directly influence tumor cell proliferation and invasion but also help tumors indirectly by organizing its microenvironment and modulating immune responses to tumor cells. Best known for orchestrating inflammation and angiogenesis, the role of MC in shaping adaptive immune responses has become a focus of recent investigations. MC mobilize T cells and antigen-presenting dendritic cells. They function as intermediaries in regulatory T cells (Treg)-induced tolerance but can also modify or reverse Treg-suppressive properties. The central role of MC in the control of innate and adaptive immunity endows them with the ability to tune the nature of host responses to cancer and ultimately influence the outcome of disease and fate of the cancer patient.

Gene expression patterns in the hippocampus and amygdala of endogenous depression and chronic stress models

The etiology of depression is still poorly understood, but two major causative hypotheses have been put forth: the monoamine deficiency and the stress hypotheses of depression. We evaluate these hypotheses using animal models of endogenous depression and chronic stress. The endogenously depressed rat and its control strain were developed by bidirectional selective breeding from the Wistar–Kyoto (WKY) rat, an accepted model of major depressive disorder (MDD). The WKY More Immobile (WMI) substrain shows high immobility/despair-like behavior in the forced swim test (FST), while the control substrain, WKY Less Immobile (WLI), shows no depressive behavior in the FST. Chronic stress responses were investigated by using Brown Norway, Fischer 344, Lewis and WKY, genetically and behaviorally distinct strains of rats. Animals were either not stressed (NS) or exposed to chronic restraint stress (CRS). Genome-wide microarray analyses identified differentially expressed genes in hippocampi and amygdalae of the endogenous depression and the chronic stress models. No significant difference was observed in the expression of monoaminergic transmission-related genes in either model. Furthermore, very few genes showed overlapping changes in the WMI vs WLI and CRS vs NS comparisons, strongly suggesting divergence between endogenous depressive behavior- and chronic stress-related molecular mechanisms. Taken together, these results posit that although chronic stress may induce depressive behavior, its molecular underpinnings differ from those of endogenous depression in animals and possibly in humans, suggesting the need for different treatments. The identification of novel endogenous depression-related and chronic stress response genes suggests that unexplored molecular mechanisms could be targeted for the development of novel therapeutic agents.

Expression of RORγt Marks a Pathogenic Regulatory T Cell Subset in Human Colon Cancer

Tregs that expand in human colon cancer have proinflammatory properties and contribute to tumor progression. A Treg Melting Pot Some things are not what they seem. Like the allegorical wolf in sheep’s clothing, cell populations that may seem homogeneous may actually contain subsets with different functions. Indeed, such hidden subpopulations may result in contradictory findings in different systems. Blatner et al. now find a subset of regulatory T cells (Tregs) in human colon cancer that may explain disparate clinical outcomes between studies. The authors found preferential expansion in human colon cancer of Tregs that can suppress T cells but are not anti-inflammatory like more classic Tregs. They then looked in a mouse model of hereditary polyposis and found that these cells, which express Foxp3 and RORγt, express the proinflammatory cytokine IL-17 and are directly associated with inflammation and disease progression. The balance between anti-inflammatory Tregs and these “pathogenic” proinflammatory Tregs may play a role in regulating cancer inflammation. Targeting these RORγt+ Tregs may influence disease outcome in colon cancer. The role of regulatory T cells (Tregs) in human colon cancer (CC) remains controversial: high densities of tumor-infiltrating Tregs can correlate with better or worse clinical outcomes depending on the study. In mouse models of cancer, Tregs have been reported to suppress inflammation and protect the host, suppress T cells and protect the tumor, or even have direct cancer-promoting attributes. These different effects may result from the presence of different Treg subsets. We report the preferential expansion of a Treg subset in human CC with potent T cell–suppressive, but compromised anti-inflammatory, properties; these cells are distinguished from Tregs present in healthy donors by their coexpression of Foxp3 and RORγt. Tregs with similar attributes were found to be expanded in mouse models of hereditary polyposis. Indeed, ablation of the RORγt gene in Foxp3+ cells in polyp-prone mice stabilized Treg anti-inflammatory functions, suppressed inflammation, improved polyp-specific immune surveillance, and severely attenuated polyposis. Ablation of interleukin-6 (IL-6), IL-23, IL-17, or tumor necrosis factor–α in polyp-prone mice reduced polyp number but not to the same extent as loss of RORγt. Surprisingly, loss of IL-17A had a dual effect: IL-17A–deficient mice had fewer polyps but continued to have RORγt+ Tregs and developed invasive cancer. Thus, we conclude that RORγt has a central role in determining the balance between protective and pathogenic Tregs in CC and that Treg subtype regulates inflammation, potency of immune surveillance, and severity of disease outcome.

Adenomatous polyps are driven by microbe-instigated focal inflammation and are controlled by IL-10-producing T cells.

Interleukin (IL)-10 is elevated in cancer and is thought to contribute to immune tolerance and tumor growth. Defying these expectations, the adoptive transfer of IL-10-expressing T cells to mice with polyposis attenuates microbial-induced inflammation and suppresses polyposis. To gain better insights into how IL-10 impacts polyposis, we genetically ablated IL-10 in T cells in APC(Δ468) mice and compared the effects of treatment with broad-spectrum antibiotics. We found that T cells and regulatory T cells (Treg) were a major cellular source of IL-10 in both the healthy and polyp-bearing colon. Notably, T cell-specific ablation of IL-10 produced pathologies that were identical to mice with a systemic deficiency in IL-10, in both cases increasing the numbers and growth of colon polyps. Eosinophils were found to densely infiltrate colon polyps, which were enriched similarly for microbiota associated previously with colon cancer. In mice receiving broad-spectrum antibiotics, we observed reductions in microbiota, inflammation, and polyposis. Together, our findings establish that colon polyposis is driven by high densities of microbes that accumulate within polyps and trigger local inflammatory responses. Inflammation, local microbe densities, and polyp growth are suppressed by IL-10 derived specifically from T cells and Tregs.

Current status of interleukin-10 and regulatory T-cells in cancer.

Purpose of review Tumor growth elicits antigen-specific cytotoxic as well as immune suppressive responses. Interleukin-10 (IL-10) is a key immune-suppressive cytokine produced by regulatory T-cells and by helper T-cells. Here, we review pleiotropic functions of IL-10 that impact the immune pathology of cancer. Recent findings The role of IL-10 in cancer has become less certain with the knowledge of its immune stimulatory functions. IL-10 is needed for T-helper cell functions, T-cell immune surveillance, and suppression of cancer-associated inflammation. By promoting tumor-specific immune surveillance and hindering pathogenic inflammation, IL-10 is emerging as a key cytokine in the battle of the host against cancer. Summary IL-10 functions at the cross-roads of immune stimulation and immune suppression in cancer. Immunological mechanisms of action of IL-10 can be ultimately exploited to develop novel and effective cancer therapies.

Discovery of blood transcriptomic markers for depression in animal models and pilot validation in subjects with early-onset major depression

Early-onset major depressive disorder (MDD) is a serious and prevalent psychiatric illness in adolescents and young adults. Current treatments are not optimally effective. Biological markers of early-onset MDD could increase diagnostic specificity, but no such biomarker exists. Our innovative approach to biomarker discovery for early-onset MDD combined results from genome-wide transcriptomic profiles in the blood of two animal models of depression, representing the genetic and the environmental, stress-related, etiology of MDD. We carried out unbiased analyses of this combined set of 26 candidate blood transcriptomic markers in a sample of 15–19-year-old subjects with MDD (N=14) and subjects with no disorder (ND, N=14). A panel of 11 blood markers differentiated participants with early-onset MDD from the ND group. Additionally, a separate but partially overlapping panel of 18 transcripts distinguished subjects with MDD with or without comorbid anxiety. Four transcripts, discovered from the chronic stress animal model, correlated with maltreatment scores in youths. These pilot data suggest that our approach can lead to clinically valid diagnostic panels of blood transcripts for early-onset MDD, which could reduce diagnostic heterogeneity in this population and has the potential to advance individualized treatment strategies.

Mast cell 5-lipoxygenase activity promotes intestinal polyposis in APC Δ468 mice

Arachidonic acid metabolism has been implicated in colon carcinogenesis, but the role of hematopoietic 5-lipoxygenase (5LO) that may impact tumor immunity in development of colon cancer has not been explored. Here we show that tissue-specific deletion of the 5LO gene in hematopoietic cells profoundly attenuates polyp development in the APC(Δ468) murine model of colon polyposis. In vitro analyses indicated that mast cells in particular utilized 5LO to limit proliferation of intestinal epithelial cells and to mobilize myeloid-derived suppressor cells (MDSCs). Mice lacking hemapoietic expression of 5LO exhibited reduced recruitment of MDSCs to the spleen, mesenteric lymph nodes, and primary tumor site. 5LO deficiency also reduced the activity in MDSCs of arginase-1, which is thought to be critical for MDSC function. Together, our results establish a pro-tumorigenic role of hematopoietic 5LO in the immune microenvironment and suggest 5LO inhibition as an avenue for future investigation in treatment of colorectal polyposis and cancer.

Context and strain-dependent behavioral response to stress

BackgroundThis study posed the question whether strain differences in stress-reactivity lead to differential behavioral responses in two different tests of anxiety. Strain differences in anxiety-measures are known, but strain differences in the behavioral responses to acute prior stress are not well characterized.MethodsWe studied male Fisher 344 (F344) and Wistar Kyoto (WKY) rats basally and immediately after one hour restraint stress. To distinguish between the effects of novelty and prior stress, we also investigated behavior after repeated exposure to the test chamber. Two behavioral tests were explored; the elevated plus maze (EPM) and the open field (OFT), both of which are thought to measure activity, exploration and anxiety-like behaviors. Additionally, rearing, a voluntary behavior, and grooming, a relatively automatic, stress-responsive stereotyped behavior were measured in both tests.ResultsPrior exposure to the test environment increased anxiety-related measures regardless of prior stress, reflecting context-dependent learning process in both tests and strains. Activity decreased in response to repeated testing in both tests and both strains, but prior stress decreased activity only in the OFT which was reversed by repeated testing. Prior stress decreased anxiety-related measures in the EPM, only in F344s, while in the OFT, stress led to increased freezing mainly in WKYs.ConclusionData suggest that differences in stressfulness of these tests predict the behavior of the two strains of animals according to their stress-reactivity and coping style, but that repeated testing can overcome some of these differences.

CCL22 regulates experimental autoimmune encephalomyelitis by controlling inflammatory macrophage accumulation and effector function

EAE is a demyelinating disease of the CNS and serves as a mouse model of MS. Expression of CCL22 in the draining LNs and spinal cord correlated with the onset of clinical EAE development and remained elevated. Administration of anti‐CCL22 at the time of autoantigen immunization delayed the initiation of clinical disease and dampened the severity of peak initial disease and relapses. Reduced EAE severity correlated with the reduction of pathology and leukocytes in the CNS, particularly, activated CD11b+Ly6Chi macrophages. There were no differences in effector T cell‐proliferative responses or effector T cell IFN‐γ or IL‐17 responses. However, treatment at the onset of disease did not reduce disease progression. Treatment of adoptive T cell transfer recipient mice with anti‐CCL22 resulted in decreased clinical disease development accompanied by a decrease in CNS accumulation of CD11b+Ly6Chi macrophages. Neutralization of CCL22 resulted in a macrophage population whose effector cytokine expression consisted of decreased TNF and increased IL‐10, a phenotype more consistent with M2 macrophages. This was corroborated by in vitro cultures of macrophages with CCL22. These results suggest that CCL22 functions to regulate development of EAE through macrophage chemoattraction and effector function.