Characterization of the immune microenvironment in melanoma patients resistant to targeted and immunotherapies by a multidisciplinary approach

Most melanoma patients who develop resistance to targeted therapies do not respond to subsequent immunotherapy. Therefore, establishing which patients would derive clinical benefit from immunotherapy is a compelling clinical question. We performed a meta-analysis of published transcriptome datasets from melanoma biopsies before and after development of resistance to BRAFi or BRAFi/MEKi. We observed an increase in M2-macrophages infiltrate by CIBERSORT in relapsed biopsies as well as an increase in T-cell exhaustion markers and immunosuppressive cytokines. Our preliminary findings show changes in the galectin/glycan axis in melanoma resistance to BRAFi/MEKi. Particularly, we observed that the expression of Galectin-1 (Gal-1) is increased in human melanoma resistant cells. We analyzed single-cell and bulk RNA-Seq gene expression profiles from melanoma biopsies before and during treatment with anti-PD-1/anti-CTLA-4 and found that macrophages and CD8 T-cells of non-responders upregulate a specific glycosylation-related signature. Macrophages from non-responding patients show an immunosuppressive expression profile accompanied by the appearance of a novel sub-group during treatment associated with resistance. We hypothesize that there are Gal-1/glycan interactions that promote an M2 immunosuppressive microenvironment in resistant tumors preventing response to immunotherapy. Finally, we developed MIXTURE, a novel algorithm to infer the tumor immune infiltrate that overcomes CIBERSORT limitations. MIXTURE analysis revealed a differential immunosuppressive infiltrate in melanoma biopsies with high intratumoral heterogeneity and in biopsies from non-responding patients to anti PD-1 immunotherapy.

High intratumoural galectin-1 expression predicts adverse outcome in ALK- ALCL and CD30+ PTCL-NOS

Galectin-1 (Gal-1) has been associated with adverse prognosis in several cancers including lymphoma entities with CD30 expression. However, Gal-1 expression has not been systematically assessed in peripheral T-cell lymphomas (PTCL). Specimens from 169 nodal PTCL were assessed for intratumoural Gal-1 expression by immunohistochemistry. Overall survival (OS) in groups exhibiting high and low Gal-1 expression was compared in the cohort and in a subset analysis of CD30-positive PTCL only. Gal-1 expression was also correlated with biomarkers of the tumour microenvironment. No significant difference in OS based on Gal-1 expression was observed in the entire PTCL cohort. However, in the CD30-positive cohort, patients with high Gal-1 levels had significantly poorer outcome (5 years OS 10%, 95% confidence interval CI, 1-36) than their low Gal-1 counterparts (5 years OS 48%, 95% CI, 30-64, P = .021). In univariate analyses age 60 or younger, non-elevated lactate dehydrogenase (LDH), and performance score less than 2 correlated with superior survival but high Gal-1 expression significantly predicted adverse outcome at both univariate (HR 2.5, 95% CI, 1.1-5.7, P = .026) and multivariate levels (HR 3.2, 95% CI, 1.2-8.5, P = .017). Tumours with high Gal-1 had few cytotoxic T cells in the tumour microenvironment. High intratumoural Gal-1 expression before therapeutic intervention correlates with adverse outcome in nodal CD30⁺ , ALK^- PTCL patients.

An adipose tissue galectin controls endothelial cell function via preferential recognition of 3-fucosylated glycans

Upon overnutrition, adipocytes activate a homeostatic program to adjust anabolic pressure. An inflammatory response enables adipose tissue (AT) expansion with concomitant enlargement of its capillary network, and reduces energy storage by increasing insulin resistance. Galectin-12 (Gal-12), an endogenous lectin preferentially expressed in AT, plays a key role in adipocyte differentiation, lipolysis, and glucose homeostasis. Here, we reveal biochemical and biophysical determinants of Gal-12 structure, including its preferential recognition of 3-fucosylated structures, a unique feature among members of the galectin family. Furthermore, we identify a previously unanticipated role for this lectin in the regulation of angiogenesis within AT. Gal-12 showed preferential localization within the inner side of lipid droplets, and its expression was upregulated under hypoxic conditions. Through glycosylation-dependent binding to endothelial cells, Gal-12 promoted in vitro angiogenesis. Moreover, analysis of in vivo AT vasculature showed reduced vascular networks in Gal-12-deficient (Lgals12^-/-) compared to wild-type mice, supporting a role for this lectin in AT angiogenesis. In conclusion, this study unveils biochemical, topological, and functional features of a hypoxia-regulated galectin in AT, which modulates endothelial cell function through recognition of 3-fucosylated glycans. Thus, glycosylation-dependent programs may control AT homeostasis by modulating endothelial cell biology with critical implications in metabolic disorders and inflammation.

Growth hormone upregulates the pro-tumorigenic galectin 1 in mouse liver

Transgenic mice overexpressing growth hormone (GH) spontaneously develop liver tumors, including hepatocellular carcinoma (HCC), within a year. The preneoplastic liver pathology in these mice recapitulates that observed in humans at high risk of developing hepatic cancer. Although increased expression of galectin 1 (GAL1) in liver tissue is associated with HCC aggressiveness, a link between this glycan-binding protein and hormone-related tumor development has not yet been explored. In this study, we investigated GAL1 expression during liver tumor progression in mice continuously exposed to high levels of GH. GAL1 expression was determined by Western blotting, RT-qPCR and immunohistochemistry in the liver of transgenic mice overexpressing GH. Animals of representative ages at different stages of liver pathology were studied. GAL1 expression was upregulated in the liver of GH-transgenic mice. This effect was observed at early ages, when animals displayed no signs of liver disease or minimal histopathological alterations and was also detected in young adults with preneoplastic liver pathology. Remarkably, GAL1 upregulation was sustained during aging and its expression was particularly enhanced in liver tumors. GH also induced hepatic GAL1 expression in mice that were treated with this hormone for a short period. Moreover, GH triggered a rapid increment in GAL1 protein expression in human HCC cells, denoting a direct effect of the hormone on hepatocytes. Therefore, our results indicate that GH upregulates GAL1 expression in mouse liver, which may have critical implications in tumorigenesis. These findings suggest that this lectin could be implicated in hormone-driven liver carcinogenesis.

Abstract 1303: Targeted inhibition of galectin-1 suppresses glioblastoma growth

Background: Galectin-1 (Gal1), a carbohydrate-binding protein is implicated in cancer cell proliferation, invasion and tumor angiogenesis. An earlier report from our laboratory demonstrated that glioblastoma (GB) cells express high levels of Gal-1, which promotes tumor progression through upregulation of CXCR4 viaNF-κB in in vitro GB models. Recently, several Gal1-targeting compounds have emerged. OTX008 is a calixarene derivative designed to bind the Gal1 amphipathic β-sheet conformation. Our study aimed to validate the effect of the non-peptidic galectin-1 inhibitor OTX008 in human GB in relevant pre-clinical models.

Methods: In vitro cell culture and in vivo GL261 murine models of GB were utilized to assess efficacy of treatment with OTX008 via Alzet osmotic pumps. To investigate the mechanistic effect of OTX008 on GB cells, we used RT-PCR and western blots techniques. Magnetic resonance imaging (MRI), and immunohistochemistry (IHC)-staining methods were used to detect tumor growth in in vivo GL261 murine model following OTX008 treatments.

Results: In cultured human and mouse GB cells, OTX008 inhibited proliferation and invasion at micromolar concentrations. We also found that the anti-proliferative effects correlated with Gal1 expression in human and mouse GB cell lines. Furthermore, OTX008 inhibited Gal1 expression and AKT-dependent survival pathways, and decreased CXCR4 expression. In vivo, continued 100ng/kg OTX008 treatment via Alzet osmotic pumps over 14 days reduced tumor growth of GL261 murine model after 3 weeks of implantation. OTX008 treatment was associated with downregulation of Gal1 and Ki67 in treated tumors, as well as decreased micro-vessel density and VEGFR2 expression.

Conclusion: These findings suggest that targeting galectin-1 may be an effective approach in the treatment of GB patients.

Citation Format: David Cachia, Arindam Rano Chatterjee, William Alex Vandergrift, Sunil J. Patel, Gabriel A. Rabinovich, Arabinda Das. Targeted inhibition of galectin-1 suppresses glioblastoma growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1303.

Lack of galectin-1 exacerbates chronic hepatitis, liver fibrosis, and carcinogenesis in murine hepatocellular carcinoma model

Chronic liver inflammation (CLI) is a risk factor for development of hepatocellular carcinoma (HCC). Galectin-1 (Gal1) is involved in the regulation of inflammation, angiogenesis, and tumorigenesis, exhibiting multiple anti-inflammatory and protumorigenic activities. We aimed to explore its regulatory role in CLI and HCC progression using an established model of CLI-mediated HCC development, Abcb4 [multidrug-resistance 2 (Mdr2)]-knockout (KO) mice, which express high levels of Gal1 in the liver. We generated double-KO (dKO) Gal1-KO/Mdr2-KO mice on C57BL/6 and FVB/N genetic backgrounds and compared HCC development in the generated strains with their parental Mdr2-KO strains. Loss of Gal1 increased liver injury, inflammation, fibrosis, and ductular reaction in dKO mice of both strains starting from an early age. Aged dKO mutants displayed earlier hepatocarcinogenesis and increased tumor size compared with control Mdr2-KO mice. We found that osteopontin, a well-known modulator of HCC development, and oncogenic proteins Ntrk2 (TrkB) and S100A4 were overexpressed in dKO compared with Mdr2-KO livers. Our results demonstrate that in Mdr2-KO mice, a model of CLI-mediated HCC, Gal1-mediated protection from hepatitis, liver fibrosis, and HCC initiation dominates over its known procarcinogenic activities at later stages of HCC development. These findings suggest that anti-Gal1 treatments may not be applicable at all stages of CLI-mediated HCC.-Potikha, T., Pappo, O., Mizrahi, L., Olam, D., Maller, S. M., Rabinovich, G. A., Galun, E., Goldenberg, D. S. Lack of galectin-1 exacerbates chronic hepatitis, liver fibrosis, and carcinogenesis in murine hepatocellular carcinoma model.

Targeting TMEM176B Enhances Antitumor Immunity and Augments the Efficacy of Immune Checkpoint Blockers by Unleashing Inflammasome Activation

Although immune checkpoint blockers have yielded significant clinical benefits in patients with different malignancies, the efficacy of these therapies is still limited. Here, we show that disruption of transmembrane protein 176B (TMEM176B) contributes to CD8⁺ T cell-mediated tumor growth inhibition by unleashing inflammasome activation. Lack of Tmem176b enhances the antitumor activity of anti-CTLA-4 antibodies through mechanisms involving caspase-1/IL-1β activation. Accordingly, patients responding to checkpoint blockade therapies display an activated inflammasome signature. Finally, we identify BayK8644 as a potent TMEM176B inhibitor that promotes CD8⁺ T cell-mediated tumor control and reinforces the antitumor activity of both anti-CTLA-4 and anti-PD-1 antibodies. Thus, pharmacologic de-repression of the inflammasome by targeting TMEM176B may enhance the therapeutic efficacy of immune checkpoint blockers.

Dual knockdown of Galectin-8 and its glycosylated ligand, the activated leukocyte cell adhesion molecule (ALCAM/CD166), synergistically delays in vivo breast cancer growth

Galectin-8 (Gal-8), a 'tandem-repeat'-type galectin, has been described as a modulator of cellular functions including adhesion, spreading, growth arrest, apoptosis, pathogen recognition, autophagy, and immunomodulation. We have previously shown that activated leukocyte cell adhesion molecule (ALCAM), also known as CD166, serves as a receptor for endogenous Gal-8. ALCAM is a member of the immunoglobulin superfamily involved in cell-cell adhesion through homophilic (ALCAM-ALCAM) and heterophilic (i.e. ALCAM-CD6) interactions in different tissues. Here we investigated the physiologic relevance of ALCAM-Gal-8 association and glycosylation-dependent mechanisms governing these interactions. We found that silencing of ALCAM in MDA-MB-231 triple negative breast cancer cells decreases cell adhesion and migration onto Gal-8-coated surfaces in a glycan-dependent fashion. Remarkably, either Gal-8 or ALCAM silencing also disrupted cell-cell adhesion, and led to reduced tumor growth in a murine model of triple negative breast cancer. Moreover, structural characterization of endogenous ALCAM N-glycosylation showed abundant permissive structures for Gal-8 binding. Importantly, we also found that cell sialylation controls Gal-8-mediated cell adhesion. Altogether, these findings demonstrate a central role of either ALCAM or Gal-8 (or both) in controlling triple negative breast cancer.

Clinical Relevance of Galectin-1 and Galectin-3 in Rheumatoid Arthritis Patients: Differential Regulation and Correlation With Disease Activity

Galectins, a family of animal lectins, play central roles in immune system regulation, shaping both innate and adaptive responses in physiological and pathological processes. These include rheumatoid arthritis (RA), a chronic multifactorial autoimmune disease characterized by inflammatory responses that affects both articular and extra-articular tissues. Galectins have been reported to play central roles in RA and its experimental animal models. In this perspective article we present new data highlighting the regulated expression of galectin-1 (Gal-1) and galectin-3 (Gal-3) in sera from RA patients under disease-modifying anti-rheumatic drugs (DMARDs) and/or corticoid treatment in the context of a more comprehensive discussion that summarizes the roles of galectins in joint inflammation. We found that Gal-1 levels markedly increase in sera from RA patients and positively correlate with erythrocyte sedimentation rate (ERS) and disease activity score 28 (DAS-28) parameters. On the other hand, Gal-3 is downregulated in RA patients, but positively correlates with health assessment questionnaire parameter (HAQ). Finally, by generating receiver-operator characteristic (ROC) curves, we found that Gal-1 and Gal-3 serum levels constitute good parameters to discriminate patients with RA from healthy individuals. Our findings uncover a differential regulation of Gal-1 and Gal-3 which might contribute to the anti-inflammatory effects elicited by DMARDs and corticoid treatment in RA patients.

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Abstract 3559: Galectin-1 upregulates CXCR4 in glioblastoma through upregulation of CXCR4 via NF-κB activation

Background: Despite aggressive treatment, including surgical resection, radiation and chemotherapy, over 90% of glioblastoma (GB) patients experience tumor recurrence. This may be due to high migratory potential, abnormal angiogenesis, molecular heterogeneity and a strong immunosuppressive environment. An earlier report from our laboratory demonstrated that GB cells express high levels of carbohydrate-binding galectin protein: galectin-1 (Gal-1). However, the role of galectin-1 in GB remains elusive. The aim of this study was to evaluate whether galectin-1 promotes tumor progression through upregulation of CXCR4 via NF-κB in in vitro GB models. Methods: To investigate the molecular mechanisms of Gal-1 on tumor progression, we used RT-PCR and western blots techniques. Gal-1 was stably over-expressed in the U118 and U87MG cell line. Gal-1 (+/-) sub-clones were assayed for attachment, proliferation, migration, and tube formation. Results: Gal-1 protein expression was assessed in human GB cells. We found increased Gal-1 protein expression in human GB cells and tissue. To investigate the effects of Gal-1 silencing on angiogenesis in vitro, we collected conditioned media from Gal-1-knockdown U118 and U87MG cells then applied this to human umbilical vein endothelial cells (HUVEC) culture to analyze endothelial cell proliferation, migration, and tube formation. Proliferation rate, migrating capability, and tube formation decreased significantly when HUVECs were cultured with concentrated conditioned media from Gal-1-knockdown cells. This data suggests that Gal-1 in GB cells may promote tumor angiogenesis both in vitro and co-culture. Results showed that silencing of Gal-1 in U118 and U87MG cells significantly repressed CXCR4 expression at the mRNA level and protein levels. To further explore the role of CXCR4 in GB cells, CXCR4 knockdown resulted in significant inhibition of cell migration and clonogenic ability in vitro. Thus, Gal-1 might upregulate CXCR4 expression to promote tumor progression. A previous laboratory study indicated that NF-κB promotes cancer cell motility by upregulating CXCR4 expression. Luciferase reporter assay was used to determine the involvement of NF-κB in Gal-1-induced CXCR4 expression in U118 and U87MG cells. NF-κB luciferase activity was significantly decreased in Gal-1-knockdown cells. Moreover, decreased CXCR4 promoter activity and protein expression in Gal-1-knockdown cells were observed. This data indicates that Gal-1 might modulate CXCR4 expression via NF-κB activation. Conclusion: Our in vitro cell culture results suggest that upregulation of galectin-1 and CXCR4 might at least in part explain the aggressive infiltrative biology of GB and the Gal-1-CXCR4 axis may serve as a therapeutic target. Further studies in different animal models are warranted.

Citation Format: David Cachia, Rachel Malley, William A. Vandergrift, Sunil Patel, Gabriel A. Rabinovich, Arabinda Das. Galectin-1 upregulates CXCR4 in glioblastoma through upregulation of CXCR4 via NF-κB activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3559.

Galectins: Multitask signaling molecules linking fibroblast, endothelial and immune cell programs in the tumor microenvironment

Tumor cells corrupt surrounding normal cells instructing them to support proliferative, pro-angiogenic and immunosuppressive networks that favor tumorigenesis and metastasis. This dynamic cross-talk is sustained by a range of intracellular signals and extracellular mediators produced by both tumoral and non-tumoral cells. Galectins -whether secreted or intracellularly expressed- play central roles in the tumorigenic process by delivering regulatory signals that contribute to reprogram fibroblasts, endothelial and immune cell programs. Through glycosylation-dependent or independent mechanisms, these endogenous lectins control a variety of cellular events leading to tumor cell proliferation, survival, migration, inflammation, angiogenesis and immune escape. Here we discuss the role of galectin-driven pathways, particularly those activated in non-tumoral stromal cells, in modulating tumor progression.

Galectins in Intestinal Inflammation: Galectin-1 Expression Delineates Response to Treatment in Celiac Disease Patients

Galectins, a family of animal lectins characterized by their affinity for N-acetyllactosamine-enriched glycoconjugates, modulate several immune cell processes shaping the course of innate and adaptive immune responses. Through interaction with a wide range of glycosylated receptors bearing complex branched N-glycans and core 2-O-glycans, these endogenous lectins trigger distinct signaling programs thereby controling immune cell activation, differentiation, recruitment and survival. Given the unique features of mucosal inflammation and the differential expression of galectins throughout the gastrointestinal tract, we discuss here key findings on the role of galectins in intestinal inflammation, particularly Crohn’s disease, ulcerative colitis, and celiac disease (CeD) patients, as well as in murine models resembling these inflammatory conditions. In addition, we present new data highlighting the regulated expression of galectin-1 (Gal-1), a proto-type member of the galectin family, during intestinal inflammation in untreated and treated CeD patients. Our results unveil a substantial upregulation of Gal-1 accompanying the anti-inflammatory and tolerogenic response associated with gluten-free diet in CeD patients, suggesting a major role of this lectin in favoring resolution of inflammation and restoration of mucosal homeostasis. Thus, a coordinated network of galectins and their glycosylated ligands, exerting either anti-inflammatory or proinflammatory responses, may influence the interplay between intestinal epithelial cells and the highly specialized gut immune system in physiologic and pathologic settings.

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

Abstract P4-03-08: Withdrawn

This abstract was withdrawn by the authors.

Glycans Pave the Way for Immunotherapy in Triple-Negative Breast Cancer

The clinical efficacy of therapies targeting the PD-1/PD-L1 pathway is still limited. In this issue of Cancer Cell, Li and colleagues identify a PD-L1 glycosylation-based mechanism in triple-negative breast cancer that fosters immunosuppression by enhancing interactions with PD-1. Targeting glycosylated PD-L1 with a drug-conjugated antibody opens new avenues for treatment.

[Immunotherapy in cancer. Current prospects, challenges and new horizons]

Recent understanding of the mechanisms that control immune system homeostasis and orchestrate antitumor responses has prompted the development of novel immunotherapeutic modalities. These include antibodies that target immune checkpoints such as PD-1/PD-L1 and CTLA-4, agonistic antibodies of costimulatory molecules such as CD137 and OX-40 and the adoptive transfer of genetically-modified antitumor T cells. However, a large number of patients do not respond to these therapies and develop resistance as a result of activation of compensatory circuits. Rational combination of immunotherapeutic modalities will help overcome resistance and will increase the number of patients who will benefit from these treatments. Moreover, identification of predictive biomarkers will allow selection of patients responding to these treatments. Emerging clinical trials and pre-clinical studies have shown exciting results anticipating new horizons in the design and implementation of cancer immunotherapeutic modalities.

Peripheral Neuroimmunoendocrine Interactions: Contribution of TNFRp55 to the Circadian Synchronization of Progesterone and Cytokine Production in Joints of Mice in Late Pregnancy

OBJECTIVE

Circadian rhythms are generated by the suprachiasmatic nucleus of the hypothalamus and involve rhythmic expression of clock genes and proteins. This rhythmicity is transferred to peripheral tissues by neural and hormonal signals. Late pregnancy is considered a state of inflammation which impacts on peripheral tissues such as joints. Tumor necrosis factor (TNF) mediates inflammatory and circadian responses through its p55 receptor (TNFRp55). Neuroimmunoendocrine interactions in joints have not been studied completely. The purpose of this study was to analyze these interactions, investigating the circadian rhythms of progesterone (Pg) and pro- and anti-inflammatory cytokines in the joints at the end of pregnancy (gestational day 18). Moreover, the impact of TNFRp55 deficiency on these temporal oscillations was explored.

METHODS

Wild-type and TNFRp55-deficient (KO) C57BL/6 mice were kept under constant darkness in order to study their endogenous circadian rhythms. The expression of the clock genes Bmal1 and Per1 at circadian time 7 was studied by reverse transcription polymerase chain reaction in the ankle joints of nonpregnant and pregnant (gestational day 18) mice. In late pregnancy, Pg and the cytokines interleukin 17 (IL-17), IL-6, and IL-10 were measured in the joints throughout a 24-h period by radioimmunoassay and enzyme-linked immunosorbent assay, respectively.

RESULTS

A significant increase in Bmal1 and Per1 mRNA expression was detected in the joints of pregnant KO mice. Furthermore, KO mice displayed a desynchronization of articular Pg and cytokine production.

CONCLUSIONS

Our results show that TNF, via TNFRp55 signaling, modulates articular Pg and cytokine circadian rhythms in late pregnancy. These findings suggest a temporal neuroimmunoendocrine association in peripheral tissues in late pregnancy.

Immune-Mediated and Hypoxia-Regulated Programs: Accomplices in Resistance to Anti-angiogenic Therapies

In contrast to mechanisms taking place during resistance to chemotherapies or other targeted therapies, compensatory adaptation to angiogenesis blockade does not imply a mutational alteration of genes encoding drug targets or multidrug resistance mechanisms but instead involves intrinsic or acquired activation of compensatory angiogenic pathways. In this article we highlight hypoxia-regulated and immune-mediated mechanisms that converge in endothelial cell programs and preserve angiogenesis in settings of vascular endothelial growth factor (VEGF) blockade. These mechanisms involve mobilization of myeloid cell populations and activation of cytokine- and chemokine-driven circuits operating during intrinsic and acquired resistance to anti-angiogenic therapies. Particularly, we focus on findings underscoring a role for galectins and glycosylated ligands in promoting resistance to anti-VEGF therapies and discuss possible strategies to overcome or attenuate this compensatory pathway. Finally, we highlight emerging evidence demonstrating the interplay between immunosuppressive and pro-angiogenic programs in the tumor microenvironment (TME) and discuss emerging combinatorial anticancer strategies aimed at simultaneously potentiating antitumor immune responses and counteracting aberrant angiogenesis.

Galectin-1 is essential for efficient liver regeneration following hepatectomy

Galectin-1 (Gal1) is a known immune/inflammatory regulator which acts both extracellularly and intracellularly, modulating innate and adaptive immune responses. Here, we explored the role of Gal1 in liver regeneration using 70% partial hepatectomy (PHx) of C57BL/6 wild type and Gal1-knockout (Gal1-KO, Lgals1−/−) mice. Gene or protein expression, in liver samples collected at time intervals from 2 to 168 hours post-operation, was tested by either RT-PCR or by immunoblotting and immunohistochemistry, respectively. We demonstrated that Gal1 transcript and protein expression was induced in the liver tissue of wild type mice upon PHx. Liver regeneration following PHx was significantly delayed in the Gal1-KO compared to the control liver. This delay was accompanied by a decreased Akt phosphorylation, and accumulation of the hepatocyte nuclear p21 protein in the Gal1-KO versus control livers at 24 and 48 hours following PHx. Transcripts of several known regulators of inflammation, cell cycle and cell signaling, including some known PHx-induced genes, were aberrantly expressed (mainly down-regulated) in Gal1-KO compared to control livers at 2, 6 and 24 hours post-PHx. Transient steatosis, which is imperative for liver regeneration following PHx, was significantly delayed and decreased in the Gal1-KO compared to the control liver and was accompanied by a significantly decreased expression in the mutant liver of several genes encoding lipid metabolism regulators. Our results demonstrate that Gal1 protein is essential for efficient liver regeneration following PHx through the regulation of liver inflammation, hepatic cell proliferation, and the control of lipid storage in the regenerating liver.

Galectin-1: A Jack-of-All-Trades in the Resolution of Acute and Chronic Inflammation

Regulatory signals provide negative input to immunological networks promoting resolution of acute and chronic inflammation. Galectin-1 (Gal-1), a member of a family of evolutionarily conserved glycan-binding proteins, displays broad anti-inflammatory and proresolving activities by targeting multiple immune cell types. Within the innate immune compartment, Gal-1 acts as a resolution-associated molecular pattern by counteracting the synthesis of proinflammatory cytokines, inhibiting neutrophil trafficking, targeting eosinophil migration and survival, and suppressing mast cell degranulation. Likewise, this lectin controls T cell and B cell compartments by modulating receptor clustering and signaling, thus serving as a negative-regulatory checkpoint that reprograms cellular activation, differentiation, and survival. In this review, we discuss the central role of Gal-1 in regulatory programs operating during acute inflammation, autoimmune diseases, allergic inflammation, pregnancy, cancer, and infection. Therapeutic strategies aimed at targeting Gal-1-glycan interactions will contribute to overcome cancer immunosuppression and reinforce antimicrobial immunity, whereas stimulation of Gal-1-driven immunoregulatory circuits will help to mitigate exuberant inflammation.

Driving CARs into Sweet Roads: Targeting Glycosylated Antigens in Cancer

Engineering T cells with chimeric antigen receptors (CARs) has demonstrated remarkable success in eradicating hematological malignancies. In this issue of Immunity, June and colleagues demonstrate the broad antitumor efficacy of a newly-designed CAR targeting the O-linked hypoglycosylated epitopes Tn and sialyl-Tn on cancer-associated MUC-1.

In Vivo Hemin Conditioning Targets the Vascular and Immunologic Compartments and Restrains Prostate Tumor Development

Purpose: Conditioning strategies constitute a relatively unexplored and exciting opportunity to shape tumor fate by targeting the tumor microenvironment. In this study, we assessed how hemin, a pharmacologic inducer of heme oxygenase-1 (HO-1), has an impact on prostate cancer development in an in vivo conditioning model.Experimental Design: The stroma of C57BL/6 mice was conditioned by subcutaneous administration of hemin prior to TRAMP-C1 tumor challenge. Complementary in vitro and in vivo assays were performed to evaluate hemin effect on both angiogenesis and the immune response. To gain clinical insight, we used prostate cancer patient-derived samples in our studies to assess the expression of HO-1 and other relevant genes.Results: Conditioning resulted in increased tumor latency and decreased initial growth rate. Histologic analysis of tumors grown in conditioned mice revealed impaired vascularization. Hemin-treated human umbilical vein endothelial cells (HUVEC) exhibited decreased tubulogenesis in vitro only in the presence of TRAMP-C1-conditioned media. Subcutaneous hemin conditioning hindered tumor-associated neovascularization in an in vivo Matrigel plug assay. In addition, hemin boosted CD8⁺ T-cell proliferation and degranulation in vitro and antigen-specific cytotoxicity in vivo A significant systemic increase in CD8⁺ T-cell frequency was observed in preconditioned tumor-bearing mice. Tumors from hemin-conditioned mice showed reduced expression of galectin-1 (Gal-1), key modulator of tumor angiogenesis and immunity, evidencing persistent remodeling of the microenvironment. We also found a subset of prostate cancer patient-derived xenografts and prostate cancer patient samples with mild HO-1 and low Gal-1 expression levels.Conclusions: These results highlight a novel function of a human-used drug as a means of boosting the antitumor response. Clin Cancer Res; 23(17); 5135-48. ©2017 AACR.

Galectin-1 circumvents lysolecithin-induced demyelination through the modulation of microglial polarization/phagocytosis and oligodendroglial differentiation

Galectin-1 (Gal-1), a member of a highly conserved family of animal lectins, binds to the common disaccharide [Galβ(1-4)-GlcNAc] on both N- and O-glycans decorating cell surface glycoconjugates. Current evidence supports a role for Gal-1 in the pathophysiology of multiple sclerosis (MS), one of the most prevalent chronic inflammatory diseases. Previous studies showed that Gal-1 exerts neuroprotective effects by promoting microglial deactivation in a model of autoimmune neuroinflammation and induces axonal regeneration in spinal cord injury. Seeking a model that could link demyelination, oligodendrocyte (OLG) responses and microglial activation, here we used a lysolecithin (LPC)-induced demyelination model to evaluate the ability of Gal-1 to preserve myelin without taking part in T-cell modulation. Gal-1 treatment after LPC-induced demyelination promoted a significant decrease in the demyelinated area and fostered more efficient remyelination, concomitantly with an attenuated oligodendroglial progenitor response reflecting less severe myelination damage. These results were accompanied by a decrease in the area of microglial activation with a shift toward an M2-polarized microglial phenotype and diminished astroglial activation. In vitro studies further showed that, mechanistically, Gal-1 targets activated microglia, promoting an increase in their myelin phagocytic capacity and their shift toward an M2 phenotype, and leads to oligodendroglial differentiation. Therefore, this study supports the use of Gal-1 as a potential treatment for demyelinating diseases such as MS.

Challenges for Scientists in Latin America

Despite political turmoil and economical crisis, research in Latin America has considerably advanced over recent decades. The present 'Point of View' outlines our perspectives on the working conditions, successes, difficulties, limitations, and challenges of biomedical scientific communities in four Latin American countries: Argentina (G.A.R.), Brazil (M.L.), Chile (A.K.), and Mexico (Y.R.).

Lack of galectin-3 increases Jagged1/Notch activation in bone marrow-derived dendritic cells and promotes dysregulation of T helper cell polarization

Galectin-3, an endogenous glycan-binding protein, is abundantly expressed at sites of inflammation and immune cell activation. Although this lectin has been implicated in the control of T helper (Th) polarization, the mechanisms underlying this effect are not well understood. Here, we investigated the role of endogenous galectin-3 during the course of experimental Leishmania major infection using galectin-3-deficient (Lgals3(-/-)) mice in a BALB/c background and the involvement of Notch signaling pathway in this process. Lgals3(-/-) mice displayed an augmented, although mixed Th1/Th2 responses compared with wild-type (WT) mice. Concomitantly, lymph node and footpad lesion cells from infected Lgals3(-/-) mice showed enhanced levels of Notch signaling components (Notch-1, Jagged1, Jagged2 and Notch target gene Hes-1). Bone marrow-derived dendritic cells (BMDCs) from uninfected Lgals3(-/-) mice also displayed increased expression of the Notch ligands Delta-like-4 and Jagged1 and pro-inflammatory cytokines. In addition, activation of Notch signaling in BMDCs upon stimulation with Jagged1 was more pronounced in Lgals3(-/-) BMDCs compared to WT BMDCs; this condition resulted in increased production of IL-6 by Lgals3(-/-) BMDCs. Finally, addition of exogenous galectin-3 to Lgals3(-/-) BMDCs partially reverted the increased sensitivity to Jagged1 stimulation. Our results suggest that endogenous galectin-3 regulates Notch signaling activation in BMDCs and influences polarization of T helper responses, thus increasing susceptibility to L. major infection.

Ligand-mediated Galectin-1 endocytosis prevents intraneural H2O2 production promoting F-actin dynamics reactivation and axonal re-growth

Axonal growth cone collapse following spinal cord injury (SCI) is promoted by semaphorin3A (Sema3A) signaling via PlexinA4 surface receptor. This interaction triggers intracellular signaling events leading to increased hydrogen peroxide levels which in turn promote filamentous actin (F-actin) destabilization and subsequent inhibition of axonal re-growth. In the current study, we demonstrated that treatment with galectin-1 (Gal-1), in its dimeric form, promotes a decrease in hydrogen peroxide (H2O2) levels and F-actin repolimerization in the growth cone and in the filopodium of neuron surfaces. This effect was dependent on the carbohydrate recognition activity of Gal-1, as it was prevented using a Gal-1 mutant lacking carbohydrate-binding activity. Furthermore, Gal-1 promoted its own active ligand-mediated endocytosis together with the PlexinA4 receptor, through mechanisms involving complex branched N-glycans. In summary, our results suggest that Gal-1, mainly in its dimeric form, promotes re-activation of actin cytoskeleton dynamics via internalization of the PlexinA4/Gal-1 complex. This mechanism could explain, at least in part, critical events in axonal regeneration including the full axonal re-growth process, de novo formation of synapse clustering, axonal re-myelination and functional recovery of coordinated locomotor activities in an in vivo acute and chronic SCI model.

SIGNIFICANCE STATEMENT

Axonal regeneration is a response of injured nerve cells critical for nerve repair in human spinal cord injury. Understanding the molecular mechanisms controlling nerve repair by Galectin-1, may be critical for therapeutic intervention. Our results show that Galectin-1; in its dimeric form, interferes with hydrogen peroxide production triggered by Semaphorin3A. The high levels of this reactive oxygen species (ROS) seem to be the main factor preventing axonal regeneration due to promotion of actin depolymerization at the axonal growth cone. Thus, Galectin-1 administration emerges as a novel therapeutic modality for promoting nerve repair and preventing axonal loss.

Galectin-1 is essential for the induction of MOG35-55 -based intravenous tolerance in experimental autoimmune encephalomyelitis

In experimental autoimmune encephalomyelitis (EAE), intravenous (i.v.) injection of the antigen, myelin oligodendrocyte glycoprotein-derived peptide, MOG35-55 , suppresses disease development, a phenomenon called i.v. tolerance. Galectin-1, an endogenous glycan-binding protein, is upregulated during autoimmune neuroinflammation and plays immunoregulatory roles by inducing tolerogenic dendritic cells (DCs) and IL-10 producing regulatory type 1 T (Tr1) cells. To examine the role of galectin-1 in i.v. tolerance, we administered MOG35-55 -i.v. to wild-type (WT) and galectin-1 deficient (Lgals1(-/-) ) mice with ongoing EAE. MOG35-55 suppressed disease in the WT, but not in the Lgals1(-/-) mice. The numbers of Tr1 cells and Treg cells were increased in the CNS and periphery of tolerized WT mice. In contrast, Lgals1(-/-) MOG-i.v. mice had reduced numbers of Tr1 cells and Treg cells in the CNS and periphery, and reduced IL-27, IL-10, and TGF-β1 expression in DCs in the periphery. DCs derived from i.v.-tolerized WT mice suppressed disease when adoptively transferred into mice with ongoing EAE, whereas DCs from Lgals1(-/-) MOG-i.v. mice were not suppressive. These findings demonstrate that galectin-1 is required for i.v. tolerance induction, likely via induction of tolerogenic DCs leading to enhanced development of Tr1 cells, Treg cells, and downregulation of proinflammatory responses.

Impact of human galectin-1 binding to saccharide ligands on dimer dissociation kinetics and structure

Endogenous lectins can control critical biological responses, including cell communication, signaling, angiogenesis and immunity by decoding glycan-containing information on a variety of cellular receptors and the extracellular matrix. Galectin-1 (Gal-1), a prototype member of the galectin family, displays only one carbohydrate recognition domain and occurs in a subtle homodimerization equilibrium at physiologic concentrations. Such equilibrium critically governs the function of this lectin signaling by allowing tunable interactions with a preferential set of glycosylated receptors. Here, we used a combination of experimental and computational approaches to analyze the kinetics and mechanisms connecting Gal-1 ligand unbinding and dimer dissociation processes. Kinetic constants of both processes were found to differ by an order of magnitude. By means of steered molecular dynamics simulations, the ligand unbinding process was followed monitoring water occupancy changes. By determining the water sites in a carbohydrate binding place during the unbinding process, we found that rupture of ligand-protein interactions induces an increase in energy barrier while ligand unbinding process takes place, whereas the entry of water molecules to the binding groove and further occupation of their corresponding water sites contributes to lowering of the energy barrier. Moreover, our findings suggested local asymmetries between the two subunits in the dimer structure detected at a nanosecond timescale. Thus, integration of experimental and computational data allowed a more complete understanding of lectin ligand binding and dimerization processes, suggesting new insights into the relationship between Gal-1 structure and function and renewing the discussion on the biophysics and biochemistry of lectin-ligand lattices.

Turning-Off Signaling by Siglecs, Selectins, and Galectins: Chemical Inhibition of Glycan-Dependent Interactions in Cancer

Aberrant glycosylation, a common feature associated with malignancy, has been implicated in important events during cancer progression. Our understanding of the role of glycans in cancer has grown exponentially in the last few years, concurrent with important advances in glycomics and glycoproteomic technologies, paving the way for the validation of a number of glycan structures as potential glycobiomarkers. However, the molecular bases underlying cancer-associated glycan modifications are still far from understood. Glycans exhibit a natural heterogeneity, crucial for their diverse functional roles as specific carriers of biologically relevant information. This information is decoded by families of proteins named lectins, including sialic acid-binding immunoglobulin (Ig)-like lectins (siglecs), C-type lectin receptors (CLRs), and galectins. Siglecs are primarily expressed on the surface of immune cells and differentially control innate and adaptive immune responses. Among CLRs, selectins are a family of cell adhesion molecules that mediate interactions between cancer cells and platelets, leukocytes, and endothelial cells, thus facilitating tumor cell invasion and metastasis. Galectins, a family of soluble proteins that bind β-galactoside-containing glycans, have been implicated in diverse events associated with cancer biology such as apoptosis, homotypic cell aggregation, angiogenesis, cell migration, and tumor-immune escape. Consequently, individual members of these lectin families have become promising targets for the design of novel anticancer therapies. During the past decade, a number of inhibitors of lectin–glycan interactions have been developed including small-molecule inhibitors, multivalent saccharide ligands, and more recently peptides and peptidomimetics have offered alternatives for tackling tumor progression. In this article, we review the current status of the discovery and development of chemical lectin inhibitors and discuss novel strategies to limit cancer progression by targeting lectin–glycan interactions.

Glycosylation-dependent binding of galectin-8 to activated leukocyte cell adhesion molecule (ALCAM/CD166) promotes its surface segregation on breast cancer cells

BACKGROUND

We previously demonstrated that the activated leukocyte cell adhesion molecule (ALCAM/CD166) can interact with galectin-8 (Gal-8) in endothelial cells. ALCAM is a member of the immunoglobulin superfamily that promotes homophilic and heterophilic cell-cell interactions. Gal-8 is a "tandem-repeat"-type galectin, known as a matricellular protein involved in cell adhesion. Here, we analyzed the physical interaction between both molecules in breast cancer cells and the functional relevance of this phenomenon.

METHODS

We performed binding assays by surface plasmon resonance to study the interaction between Gal-8 and the recombinant glycosylated ALCAM ectodomain or endogenous ALCAM from MDA-MB-231 breast cancer cells. We also analyzed the binding of ALCAM-silenced or control breast cancer cells to immobilized Gal-8 by SPR. In internalization assays, we evaluated the influence of Gal-8 on ALCAM surface localization.

RESULTS

We showed that recombinant glycosylated ALCAM and endogenous ALCAM from breast carcinoma cells physically interacted with Gal-8 in a glycosylation-dependent fashion displaying a differential behavior compared to non-glycosylated ALCAM. Moreover, ALCAM-silenced breast cancer cells exhibited reduced binding to Gal-8 relative to control cells. Importantly, exogenously added Gal-8 provoked ALCAM segregation, probably trapping this adhesion molecule at the surface of breast cancer cells.

CONCLUSIONS

Our data indicate that Gal-8 interacts with ALCAM at the surface of breast cancer cells through glycosylation-dependent mechanisms.

GENERAL SIGNIFICANCE

A novel heterophilic interaction between ALCAM and Gal-8 is demonstrated here, suggesting its physiologic relevance in the biology of breast cancer cells.

Glyco-nano-oncology: Novel therapeutic opportunities by combining small and sweet

Recent efforts toward defining the molecular features of the tumor microenvironment have revealed dramatic changes in the expression of glycan-related genes including glycosyltransferases and glycosidases. These changes affect glycosylation of proteins and lipids not only in cancer cells themselves, but also in cancer associated-stromal, endothelial and immune cells. These glycan alterations including increased frequency of β1,6-branched N-glycans and bisecting N-glycans, overexpression of tumor-associated mucins, preferred expression of T, Tn and sialyl-Tn antigen and altered surface sialylation, may contribute to tumor progression by masking or unmasking specific ligands for endogenous lectins, including members of the C-type lectin, siglec and galectin families. Differential expression of glycans or glycan-binding proteins could be capitalized for the identification of novel biomarkers and might provide novel opportunities for therapeutic intervention. This review focuses on the biological relevance of lectin-glycan interactions in the tumor microenvironment (mainly illustrated by the immunosuppressive and pro-angiogenic activities of galectin-1) and the design of functionalized nanoparticles for pharmacological delivery of multimeric glycans, lectins or selective inhibitors of lectin-glycan interactions with antitumor activity.

A galectin-specific signature in the gut delineates Crohn's disease and ulcerative colitis from other human inflammatory intestinal disorders

Inflammatory bowel diseases (IBD) are chronic and relapsing inflammatory conditions of the gastrointestinal tract including Crohn's disease (CD) and ulcerative colitis (UC). Galectins, defined by shared consensus amino acid sequence and affinity for β-galactosides, are critical modulators of the inflammatory response. However, the relevance of the galectin network in the pathogenesis of human IBD has not yet been explored. Here, we analyzed the expression of relevant members of the galectin family in intestinal biopsies, and identified their contribution as novel mucosal markers in IBD. Colonic biopsies were obtained from 59 IBD patients (22 CD and 37 UC), 9 patients with gut rejection after transplantation, 8 adult celiac patients, and 32 non-IBD donors. Galectin mRNA expression was analyzed by RT-PCR and qPCR using specific primers for individual galectins. A linear discriminant analysis (LDA) was used to analyze galectin expression in individual intestinal samples. Expression of common mucosal-associated galectins (Gal-1, -3, -4, -9) is dysregulated in inflamed tissues of IBD patients compared with non-inflamed IBD or control samples. LDA discriminated between different inflammation grades in active IBD and showed that remission IBD samples were clusterized with control samples. Galectin profiling could not distinguish CD and UC. Furthermore, inflamed IBD was discriminated from inflamed tissue of rejected gut in transplanted patients and duodenum of celiac patients, which could not be distinguished from control duodenum samples. The integrative analysis of galectins discriminated IBD from other intestinal inflammatory conditions and could be used as potential mucosal biomarker.

Melatonin Contributes to the Seasonality of Multiple Sclerosis Relapses

Seasonal changes in disease activity have been observed in multiple sclerosis, an autoimmune disorder that affects the CNS. These epidemiological observations suggest that environmental factors influence the disease course. Here, we report that melatonin levels, whose production is modulated by seasonal variations in night length, negatively correlate with multiple sclerosis activity in humans. Treatment with melatonin ameliorates disease in an experimental model of multiple sclerosis and directly interferes with the differentiation of human and mouse T cells. Melatonin induces the expression of the repressor transcription factor Nfil3, blocking the differentiation of pathogenic Th17 cells and boosts the generation of protective Tr1 cells via Erk1/2 and the transactivation of the IL-10 promoter by ROR-α. These results suggest that melatonin is another example of how environmental-driven cues can impact T cell differentiation and have implications for autoimmune disorders such as multiple sclerosis.

Galectin-1 Controls the Proliferation and Migration of Liver Sinusoidal Endothelial Cells and Their Interaction With Hepatocarcinoma Cells

Galectin-1 (Gal1), a β-galactoside-binding protein elevated in hepatocellular carcinoma (HCC), promotes epithelial-mesenchymal transition (EMT) and its expression correlates with HCC growth, invasiveness, and metastasis. During the early stages of HCC, transforming growth factor β1 (TGF-β1 ) acts as a tumor suppressor; however in advanced stages, HCC cells lose their cytostatic response to TGF-β1 and undergo EMT. Here, we investigated the role of Gal1 on liver endothelial cell biology, and the interplay between Gal1 and TGF-β1 in HCC progression. By Western blot and immunofluorescence, we analyzed Gal1 expression, secretion and localization in HepG2 and HuH-7 human HCC cells, and in SK-HEP-1 human liver sinusoidal endothelial cells (SECs). We used loss-of-function and gain-of-function experiments to down- or up-regulate Gal1 expression, respectively, in HepG2 cells. We cultured SK-HEP-1 cells with conditioned media from HCC cells secreting different levels of Gal1, and demonstrated that Gal1 derived from tumor hepatocytes induced its own expression in SECs. Colorimetric and scratch-wound assays revealed that secretion of Gal1 by HCC cells induced SEC proliferation and migration. Moreover, by fluorescence microscopy we demonstrated that Gal1 promoted glycan-dependent heterotypic adhesion of HepG2 cells to SK-HEP-1 SECs. Furthermore, TGF-β1 induced Gal1 expression and secretion by HCC cells, and promoted HepG2 cell adhesion to SK-HEP-1 SECs through a Gal1-dependent mechanism. Finally, Gal1 modulated HepG2 cell proliferation and sensitivity to TGF-β1 -induced growth inhibition. Our results suggest that Gal1 and TGF-β1 might function coordinately within the HCC microenvironment to regulate tumor growth, invasion, metastasis, and angiogenesis.

Trypanosoma cruzi extracts elicit protective immune response against chemically induced colon and mammary cancers

Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, has anticancer effects mediated, at least in part, by parasite-derived products which inhibit growth of tumor cells. We investigated whether immunity to T. cruzi antigens could induce antitumor activity, using two rat models which reproduce human carcinogenesis: colon cancer induced by 1,2-dimethylhydrazine (DMH), and mammary cancer induced by N-nitroso-N-methylurea (NMU). We found that vaccination with T. cruzi epimastigote lysates strongly inhibits tumor development in both animal models. Rats immunized with T. cruzi antigens induce activation of both CD4(+) and CD8(+) T cells and splenocytes from these animals showed higher cytotoxic responses against tumors as compared to rats receiving adjuvant alone. Tumor-associated immune responses included increasing number of CD11b/c(+) His48(-) MHC II(+) cells corresponding to macrophages and/or dendritic cells, which exhibited augmented NADPH-oxidase activity. We also found that T. cruzi lysate vaccination developed antibodies specific for colon and mammary rat cancer cells, which were capable of mediating antibody-dependent cellular cytotoxicity (ADCC) in vitro. Anti-T. cruzi antibodies cross-reacted with human colon and breast cancer cell lines and recognized 41/60 (68%) colon cancer and 38/63 (60%) breast cancer samples in a series of 123 human tumors. Our results suggest that T. cruzi antigens can evoke an integrated antitumor response involving both the cellular and humoral components of the immune response and provide novel insights into the understanding of the intricate relationship between parasite infection and tumor growth.

The thyroid status reprograms T cell lymphoma growth and modulates immune cell frequencies

In spite of considerable evidence on the regulation of immunity by thyroid hormones, the impact of the thyroid status in tumor immunity is poorly understood. Here, we evaluated the antitumor immune responses evoked in mice with different thyroid status (euthyroid, hyperthyroid, and hypothyroid) that developed solid tumors or metastases after inoculation of syngeneic T lymphoma cells. Hyperthyroid mice showed increased tumor growth along with increased expression of cell cycle regulators compared to hypothyroid and control tumor-bearing mice. However, hypothyroid mice showed a higher frequency of metastases than the other groups. Hyperthyroid mice bearing tumors displayed a lower number of tumor-infiltrating T lymphocytes, lower percentage of functional IFN-γ-producing CD8(+) T cells, and higher percentage of CD19(+) B cells than euthyroid tumor-bearing mice. However, no differences were found in the distribution of lymphocyte subpopulations in tumor-draining lymph nodes (TDLNs) or spleens among different experimental groups. Interestingly, hypothyroid TDLN showed an increased percentage of regulatory T (Treg) cells, while hyperthyroid mice displayed increased number and activity of splenic NK cells, which frequency declined in spleens from hypothyroid mice. Moreover, a decreased number of splenic myeloid-derived suppressor cells (MDSCs) were found in tumor-bearing hyperthyroid mice as compared to hypothyroid or euthyroid mice. Additionally, hyperthyroid mice showed increased cytotoxic activity, which declined in hypothyroid mice. Thus, low levels of intratumoral cytotoxic activity would favor tumor local growth in hyperthyroid mice, while regional and systemic antitumor response may contribute to tumor dissemination in hypothyroid animals. Our results highlight the importance of monitoring the thyroid status in patients with T cell lymphomas.

KEY MESSAGES

T cell lymphoma phenotype is paradoxically influenced by thyroid status. Hyperthyroidism favors tumor growth and hypothyroidism rises tumor dissemination. Thyroid status affects the distribution of immune cell types in the tumor milieu. Thyroid status also modifies the nature of local and systemic immune responses.

Galectin-1 Prevents Infection and Damage Induced by Trypanosoma cruzi on Cardiac Cells

BACKGROUND

Chronic Chagas cardiomyopathy caused by Trypanosoma cruzi is the result of a pathologic process starting during the acute phase of parasite infection. Among different factors, the specific recognition of glycan structures by glycan-binding proteins from the parasite or from the mammalian host cells may play a critical role in the evolution of the infection.

METHODOLOGY AND PRINCIPAL FINDINGS

Here we investigated the contribution of galectin-1 (Gal-1), an endogenous glycan-binding protein abundantly expressed in human and mouse heart, to the pathophysiology of T. cruzi infection, particularly in the context of cardiac pathology. We found that exposure of HL-1 cardiac cells to Gal-1 reduced the percentage of infection by two different T. cruzi strains, Tulahuén (TcVI) and Brazil (TcI). In addition, Gal-1 prevented exposure of phosphatidylserine and early events in the apoptotic program by parasite infection on HL-1 cells. These effects were not mediated by direct interaction with the parasite surface, suggesting that Gal-1 may act through binding to host cells. Moreover, we also observed that T. cruzi infection altered the glycophenotype of cardiac cells, reducing binding of exogenous Gal-1 to the cell surface. Consistent with these data, Gal-1 deficient (Lgals1-/-) mice showed increased parasitemia, reduced signs of inflammation in heart and skeletal muscle tissues, and lower survival rates as compared to wild-type (WT) mice in response to intraperitoneal infection with T. cruzi Tulahuén strain.

CONCLUSION/SIGNIFICANCE

Our results indicate that Gal-1 modulates T. cruzi infection of cardiac cells, highlighting the relevance of galectins and their ligands as regulators of host-parasite interactions.

Galectin-8 promotes regulatory T-cell differentiation by modulating IL-2 and TGFβ signaling

Galectins have emerged as potent immunoregulatory molecules that control chronic inflammation through distinct mechanisms. Galectin-8 (Gal-8), a tandem-repeat type galectin with unique preference for α2,3-sialylated glycans, is ubiquitously expressed, but little is known about its role in T cell differentiation. Here, we report that Gal-8 promotes the polyclonal differentiation of primary mouse Treg cells in vitro. We further show that Gal-8 also facilitates antigen-specific differentiation of regulatory T (Treg) cells, and that Treg cells polarized in the presence of Gal-8 express cytotoxic T lymphocyte antigen-4 (CTLA-4) and IL-10 at a higher frequency than control Treg cells, and efficiently inhibit proliferation of activated T cells in vitro. Investigation of the mechanism by which Gal-8 promotes Treg conversion revealed that Gal-8 activates TGFβ signaling and promotes sustained IL-2R signaling. Taken together, these data suggest that Gal-8 promotes the differentiation of highly suppressive Treg cells, which has implications for the treatment of inflammatory and autoimmune diseases.

Abstract 453: Engineering the tumor microenvironment: Hemin conditioning in vivo impairs tumor growth and reprograms the immune-modulatory response in prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer death in men in the United States, and inflammation is recognized as a risk factor. In this regard we have previously shown that Heme Oxygenase-1 (HO-1) over-expression plays a critical role in prostate tumor cells per se by impairing cell proliferation, invasion and migration in vitro and tumor growth in vivo. In the present study, we aimed to assess the role of stromal HO-1 in PCa. The stroma was conditioned by subcutaneously (s.c.) injecting C57BL/6 mice with 200μl of hemin (30μM; HO-1 pharmacological inducer) or its vehicle PBS on days 8, 5 and 1 prior to tumor challenge. TRAMP-C1 cells (T-C1; 2×106 isogenic murine PCa cells) were s.c. injected on the same flank in Matrigel®. Hemin pre-treated animals showed a significant increase in tumor latency (12-day delay when compared to control mice; Mantel-Cox test, P<0.01) and a significant decrease in tumor growth rate (Student t test, P <0.05). In vitro lymphocyte proliferation assays showed that hemin was able to enhance αCD3-mediated T cell proliferation and its administration was sufficient to revert T-C1-mediated immunosuppresion. Immunophenotyping of the tumor infiltrate, draining and contralateral lymph nodes and spleen samples obtained from mice after euthanasia was carried out using flow cytometry. Significant differences were detected in the frequency and activation state of both CD8+ T lymphocytes (P<0.05) and myeloid Gr-1+ cells (P <0.01). These phenomena were observed not only in the tumor infiltrate but also in other organs, suggesting hemin treatment had systemic effects on the immune compartment. The expression levels of several neovascularization-related genes was assessed by RT-q-PCR, and no significant differences were observed for VEGF, FGFβ, TIMP-1, CD142, uPA and TSP-1. Collectively, these data suggest that hemin does not affect vascularization and acts through an immune-based mechanism. Interestingly, tumors from hemin-conditioned mice showed reduced Galectin-1 (Gal-1) expression (2.6 fold; Student t test, P <0.01), evidencing a clear and long-term effect on lectin/glycan interactions on tumor cells. This in turn, may impact upon host immunosurveillance, as Gal-1 has been widely recognized as a central tumor escape mechanism. Altogether, these results showcase how HO-1 pharmacological modulation in the stroma dramatically affects PCa tumor progression in vivo and postulate lectin/glycan interactions as potential mediators of these observations.

Citation Format: Felipe M. Jaworski, Geraldine G. Gueron, Lucas D. Gentilini, Daiana B. Leonardi, Ignacio González Pérez, Geraldine Contrufo, Gabriel A. Rabinovich, Daniel G. Compagno, Diego J. Laderach, Elba S. Vazquez. Engineering the tumor microenvironment: Hemin conditioning in vivo impairs tumor growth and reprograms the immune-modulatory response in prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 453. doi:10.1158/1538-7445.AM2015-453