Therapeutic antibody activation of the glucocorticoid-induced TNF receptor by a clustering mechanism.

GITR is a TNF receptor, and its activation promotes immune responses and drives antitumor activity. The receptor is activated by the GITR ligand (GITRL), which is believed to cluster receptors into a high-order array. Immunotherapeutic agonist antibodies also activate the receptor, but their mechanisms are not well characterized. We solved the structure of full-length mouse GITR bound to Fabs from the antibody DTA-1. The receptor is a dimer, and each subunit binds one Fab in an orientation suggesting that the antibody clusters receptors. Binding experiments with purified proteins show that DTA-1 IgG and GITRL both drive extensive clustering of GITR. Functional data reveal that DTA-1 and the anti-human GITR antibody TRX518 activate GITR in their IgG forms but not as Fabs. Thus, the divalent character of the IgG agonists confers an ability to mimic GITRL and cluster and activate GITR. These findings will inform the clinical development of this class of antibodies for immuno-oncology.

Inflammatory Components of the Thyroid Cancer Microenvironment: An Avenue for Identification of Novel Biomarkers.

The incidence of thyroid cancer in the United States is on the rise with an appreciably high disease recurrence rate of 20-30%. Anaplastic thyroid cancer (ATC), although rare in occurrence, is an aggressive form of cancer with limited treatment options and bleak cure rates. This chapter uses discussions of in vitro models that are representative of papillary, anaplastic, and follicular thyroid cancer to evaluate the crosstalk between specific cells of the tumor microenvironment (TME), which serves as a highly heterogeneous realm of signaling cascades and metabolism that are associated with tumorigenesis. The cellular constituents of the TME carry out varying characteristic immunomodulatory functions that are discussed throughout this chapter. The aforementioned cell types include cancer-associated fibroblasts (CAFs), endothelial cells (ECs), and cancer stem cells (CSCs), as well as specific immune cells, including natural killer (NK) cells, dendritic cells (DCs), mast cells, T regulatory (Treg) cells, CD8+ T cells, and tumor-associated macrophages (TAMs). TAM-mediated inflammation is associated with a poor prognosis of thyroid cancer, and the molecular basis of the cellular crosstalk between macrophages and thyroid cancer cells with respect to inducing a metastatic phenotype is not yet known. The dynamic nature of the physiological transition to pathological metastatic phenotypes when establishing the TME encompasses a wide range of characteristics that are further explored within this chapter, including the roles of somatic mutations and epigenetic alterations that drive the genetic heterogeneity of cancer cells, allowing for selective advantages that aid in their proliferation. Induction of these proliferating cells is typically accomplished through inflammatory induction, whereby chronic inflammation sets up a constant physiological state of inflammatory cell recruitment. The secretions of these inflammatory cells can alter the genetic makeup of proliferating cells, which can in turn, promote tumor growth.This chapter also presents an in-depth analysis of molecular interactions within the TME, including secretory cytokines and exosomes. Since the exosomal cargo of a cell is a reflection and fingerprint of the originating parental cells, the profiling of exosomal miRNA derived from thyroid cancer cells and macrophages in the TME may serve as an important step in biomarker discovery. Identification of a distinct set of tumor suppressive miRNAs downregulated in ATC-secreted exosomes indicates their role in the regulation of tumor suppressive genes that may increase the metastatic propensity of ATC. Additionally, the high expression of pro-inflammatory cytokines in studies looking at thyroid cancer and activated macrophage conditioned media suggests the existence of an inflammatory TME in thyroid cancer. New findings are suggestive of the presence of a metastatic niche in ATC tissues that is influenced by thyroid tumor microenvironment secretome-induced epithelial to mesenchymal transition (EMT), mediated by a reciprocal interaction between the pro-inflammatory M1 macrophages and the thyroid cancer cells. Thus, targeting the metastatic thyroid carcinoma microenvironment could offer potential therapeutic benefits and should be explored further in preclinical and translational models of human metastatic thyroid cancer.

Cyclophosphamide enhances the antitumor potency of GITR engagement by increasing oligoclonal cytotoxic T cell fitness.

Only a subset of cancer patients responds to checkpoint blockade inhibition in the clinic. Strategies to overcome resistance are promising areas of investigation. Targeting glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) has shown efficacy in preclinical models, but GITR engagement is ineffective in controlling advanced, poorly immunogenic tumors, such as B16 melanoma, and has not yielded benefit in clinical trials. The alkylating agent cyclophosphamide (CTX) depletes regulatory T cells (Tregs), expands tumor-specific effector T cells (Teffs) via homeostatic proliferation, and induces immunogenic cell death. GITR agonism has an inhibitory effect on Tregs and activates Teffs. We therefore hypothesized that CTX and GITR agonism would promote effective antitumor immunity. Here we show that the combination of CTX and GITR agonism controlled tumor growth in clinically relevant mouse models. Mechanistically, we show that the combination therapy caused tumor cell death, clonal expansion of highly active CD8+ T cells, and depletion of Tregs by activation-induced cell death. Control of tumor growth was associated with the presence of an expanded population of highly activated, tumor-infiltrating, oligoclonal CD8+ T cells that led to a diminished TCR repertoire. Our studies show that the combination of CTX and GITR agonism is a rational chemoimmunotherapeutic approach that warrants further clinical investigation.

CTLA-4 blockade drives loss of Treg stability in glycolysis-low tumours.

Limiting metabolic competition in the tumour microenvironment may increase the effectiveness of immunotherapy. Owing to its crucial role in the glucose metabolism of activated T cells, CD28 signalling has been proposed as a metabolic biosensor of T cells1. By contrast, the engagement of CTLA-4 has been shown to downregulate T cell glycolysis1. Here we investigate the effect of CTLA-4 blockade on the metabolic fitness of intra-tumour T cells in relation to the glycolytic capacity of tumour cells. We found that CTLA-4 blockade promotes metabolic fitness and the infiltration of immune cells, especially in glycolysis-low tumours. Accordingly, treatment with anti-CTLA-4 antibodies improved the therapeutic outcomes of mice bearing glycolysis-defective tumours. Notably, tumour-specific CD8+ T cell responses correlated with phenotypic and functional destabilization of tumour-infiltrating regulatory T (Treg) cells towards IFNγ- and TNF-producing cells in glycolysis-defective tumours. By mimicking the highly and poorly glycolytic tumour microenvironments in vitro, we show that the effect of CTLA-4 blockade on the destabilization of Treg cells is dependent on Treg cell glycolysis and CD28 signalling. These findings indicate that decreasing tumour competition for glucose may facilitate the therapeutic activity of CTLA-4 blockade, thus supporting its combination with inhibitors of tumour glycolysis. Moreover, these results reveal a mechanism by which anti-CTLA-4 treatment interferes with Treg cell function in the presence of glucose.

Ethanol Enhances Estrogen Mediated Angiogenesis in Breast Cancer.

Angiogenesis, a highly regulated process, is exploited by tumors like breast cancer to ensure a constant supply of oxygen and nutrients and is key for tumor survival and progression. Estrogen and alcohol independently have been observed to contribute to angiogenesis in breast cancer but their combinatorial effects have never been evaluated. The exact mechanism by which estrogen and alcohol contribute to breast cancer angiogenesis remains to be elucidated. In this study, we defined the in vitro effects of the combination of estrogen and alcohol in breast cancer angiogenesis using the tubulogenesis and scratch wound assays. Conditioned media, generated by culturing the murine mammary cancer cell line, TG1-1, in estrogen and ethanol, enhanced tubule formation and migration as well as modulated the MAP Kinase pathway in the murine endothelial cell line, SVEC4-10. Additionally, estrogen and ethanol in combination enhanced the expression of the pro-angiogenic factors VEGF, MMP-9, and eNOS, and modulated Akt activation. These observations suggest that TG1-1 cells secrete pro-angiogenic molecules in response to the combination of estrogen and ethanol that modulate the morphological and migratory properties of endothelial cells. The data presented in this study, is the first in attempting to link the cooperative activity between estrogen and ethanol in breast cancer progression, underscoring correlations first made by epidemiological observations linking the two.

Macrophage inflammatory factors promote epithelial-mesenchymal transition in breast cancer.

The majority of breast cancers (90-95%) arise due to mediators distinct from inherited genetic mutations. One major mediator of breast cancer involves chronic inflammation. M1 macrophages are an integral component of chronic inflammation and the breast cancer tumor microenvironment (TME). Previous studies have demonstrated that up to 50% of the breast tumor comprise of tumor-associated macrophages (TAMs) and increased TAM infiltration has been associated with poor patient prognosis. Furthermore, breast cancer associated deaths are predominantly attributed to invasive cancers and metastasis with epithelial-mesenchymal transition (EMT) being implicated. In this study, we investigated the effects of cellular crosstalk between TAMs and breast cancer using an in vitro model system. M1 polarized THP-1 macrophage conditioned media (CM) was generated and used to evaluate cellular and functional changes of breast cancer lines T47D and MCF-7. We observed that T47D and MCF-7 exhibited a partial EMT phenotype in the presence of activated THP-1 CM. Additionally, MCF-7 displayed a significant increase in migratory and invasive properties. We conclude that M1 secretory factors can promote a partial EMT of epithelial-like breast cancer cells. The targeting of M1 macrophages or their secretory components may inhibit EMT and limit the invasive potential of breast cancer.

Elevated 20-HETE in metabolic syndrome regulates arterial stiffness and systolic hypertension via MMP12 activation.

Arterial stiffness plays a causal role in development of systolic hypertension. 20-hydroxyeicosatetraeonic acid (20-HETE), a cytochrome P450 (CYP450)-derived arachidonic acid metabolite, is known to be elevated in resistance arteries in hypertensive animal models and loosely associated with obesity in humans. However, the role of 20-HETE in the regulation of large artery remodeling in metabolic syndrome has not been investigated. We hypothesized that elevated 20-HETE in metabolic syndrome increases matrix metalloproteinase 12 (MMP12) activation leading to increased degradation of elastin, increased large artery stiffness and increased systolic blood pressure. 20-HETE production was increased ~7 fold in large, conduit arteries of metabolic syndrome (JCR:LA-cp, JCR) vs. normal Sprague-Dawley (SD) rats. This correlated with increased elastin degradation (~7 fold) and decreased arterial compliance (~75% JCR vs. SD). 20-HETE antagonists blocked elastin degradation in JCR rats concomitant with blocking MMP12 activation. 20-HETE antagonists normalized, and MMP12 inhibition (pharmacological and MMP12-shRNA-Lnv) significantly improved (~50% vs. untreated JCR) large artery compliance in JCR rats. 20-HETE antagonists also decreased systolic (182 ±â€¯3 mmHg JCR, 145 ±â€¯3 mmHg JCR + 20-HETE antagonists) but not diastolic blood pressure in JCR rats. Whereas diastolic pressure was fully angiotensin II (Ang II)-dependent, systolic pressure was only partially Ang II-dependent, and large artery stiffness was Ang II-independent. Thus, 20-HETE-dependent regulation of systolic blood pressure may be a unique feature of metabolic syndrome related to high 20-HETE production in large, conduit arteries, which results in increased large artery stiffness and systolic blood pressure. These findings may have implications for management of systolic hypertension in patients with metabolic syndrome.