Galectin-7 reprograms skin carcinogenesis by fostering innate immune evasive programs.

Non-melanoma skin cancer (NMSC) has risen dramatically as a result of chronic exposure to sunlight ultraviolet (UV) radiation, climatic changes and clinical conditions associated with immunosuppression. In spite of considerable progress, our understanding of the mechanisms that control NMSC development and their associated molecular and immunological landscapes is still limited. Here we demonstrated a critical role for galectin-7 (Gal-7), a ß-galactoside-binding protein preferentially expressed in skin tissue, during NMSC development. Transgenic mice (Tg46) overexpressing Gal-7 in keratinocytes showed higher number of papillomas compared to WT mice or mice lacking Gal-7 (Lgals7-/-) when subjected to a skin carcinogenesis protocol, in which tumor initiator 7,12-dimethylbenz[a]anthracene (DMBA) and tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were sequentially administered. RNAseq analysis of Tg46 tumor lesions revealed a unique profile compatible with cells of the myelomonocytic lineage infiltrating these tumors, an effect that was substantiated by a higher number of CD11b+Gr1+ cells in tumor-draining lymph nodes. Heightened c-Met activation and Cxcl-1 expression in Tg46 lesions suggested a contribution of this pathway to the recruitment of these cells. Remarkably, Gal-7 bound to the surface of CD11b+Ly6ChiLy6Glo monocytic myeloid cells and enhanced their immunosuppressive activity, as evidenced by increased IL-10 and TGF-ß1 secretion, and higher T-cell inhibitory activity. In vivo, carcinogen-treated Lgals7-/- animals adoptively transferred with Gal-7-conditioned monocytic myeloid cells developed higher number of papillomas, whereas depletion of these cells in Tg46-treated mice led to reduction in the number of tumors. Finally, human NMSC biopsies showed increased LGALS7 mRNA and Gal-7 protein expression and displayed transcriptional profiles associated with myeloid programs, accompanied by elevated CXCL1 expression and c-Met activation. Thus, Gal-7 emerges as a critical mediator of skin carcinogenesis and a potential therapeutic target in human NMSC.

Galectin-1 impacts on glucose homeostasis by modulating pancreatic insulin release.

Type-2 diabetes mellitus (T2DM) is an expanding global health problem, involving defective insulin secretion by pancreatic ß-cells and peripheral insulin resistance, leading to impaired glucose regulation. Galectin-1-an endogenous lectin with affinity for N-acetyllactosamine (LacNAc)-containing glycans-has emerged as a regulator of inflammatory and metabolic disorders. However, the role of galectin-1 in glucose homeostasis and pancreatic ß-cell function, independently of hypercaloric diets, has not been explored. Here, we identified a phenotype compatible with T2DM, involving alterations in glucose metabolism and pancreatic insulin release, in female but not male mice lacking galectin-1 (Lgals1-/-). Compared with age-matched controls, Lgals1-/- female mice exhibited higher body weight and increased food intake ad libitum as well as after fasting and acute re-feeding. Although fasted serum insulin levels and insulin sensitivity were similar in both genotypes, Lgals1-/- female mice presented altered glucose tolerance and higher basal glucose levels depending on the fasting period. Insulin response to glucose overload was impaired, while pancreatic insulin content was enhanced in the absence of galectin-1. Accordingly, recombinant galectin-1 enhanced glucose-stimulated insulin release in vitro. Our study identifies a role for galectin-1 in regulating glucose metabolism through modulation of pancreatic insulin secretion, highlighting novel opportunities to control T2DM.

Galectin-1 fosters an immunosuppressive microenvironment in colorectal cancer by reprogramming CD8+ regulatory T cells.

Colorectal cancer (CRC) represents the third most common malignancy and the second leading cause of cancer-related deaths worldwide. Although immunotherapy has taken center stage in mainstream oncology, it has shown limited clinical efficacy in CRC, generating an urgent need for discovery of new biomarkers and potential therapeutic targets. Galectin-1 (Gal-1), an endogenous glycan-binding protein, induces tolerogenic programs and contributes to tumor cell evasion of immune responses. Here, we investigated the relevance of Gal-1 in CRC and explored its modulatory activity within the CD8+ regulatory T cell (Treg) compartment. Mice lacking Gal-1 (Lgals1-/- ) developed a lower number of tumors and showed a decreased frequency of a particular population of CD8+CD122+PD-1+ Tregs in the azoxymethane-dextran sodium sulfate model of colitis-associated CRC. Moreover, silencing of tumor-derived Gal-1 in the syngeneic CT26 CRC model resulted in reduced number and attenuated immunosuppressive capacity of CD8+CD122+PD-1+ Tregs, leading to slower tumor growth. Moreover, stromal Gal-1 also influenced the fitness of CD8+ Tregs, highlighting the contribution of both tumor and stromal-derived Gal-1 to this immunoregulatory effect. Finally, bioinformatic analysis of a colorectal adenocarcinoma from The Cancer Genome Atlas dataset revealed a particular signature characterized by high CD8+ Treg score and elevated Gal-1 expression, which delineates poor prognosis in human CRC. Our findings identify CD8+CD122+PD-1+ Tregs as a target of the immunoregulatory activity of Gal-1, suggesting a potential immunotherapeutic strategy for the treatment of CRC.

Characterization of a neutralizing anti-human galectin-1 monoclonal antibody with angioregulatory and immunomodulatory activities.

Galectins, a family of highly conserved ß-galactoside-binding proteins, control tumor progression by modulating different hallmarks of cancer. Galectin-1 (Gal-1), a proto-type member of this family, plays essential roles in tumor angiogenesis and immunosuppression by cross-linking glycosylated receptors on the surface of endothelial and immune cells. Targeted disruption of Gal-1 suppresses tumor growth by counteracting aberrant angiogenesis and reinforcing antitumor immunity in several experimental settings. Given the multiple therapeutic benefits associated with Gal-1 blockade, several Gal-1 inhibitors, including glycan-based competitors, antagonistic peptides, aptamers and neutralizing monoclonal antibodies, have been designed and evaluated in pre-clinical tumor models. Here we report the biochemical and functional characterization of a newly developed neutralizing anti-human Gal-1 monoclonal antibody (Gal-1-mAb3), which specifically recognizes a unique epitope in Gal-1 protein and exerts both angioregulatory and immunomodulatory activities. Blockade of Gal-1 function using Gal-1-mAb3, might be relevant not only in cancer but also in other pathologic conditions characterized by aberrant angiogenesis and uncontrolled immunosuppression.

Suppression of age-related salivary gland autoimmunity by glycosylation-dependent galectin-1-driven immune inhibitory circuits.

Aging elicits quantitative and qualitative changes in different immune components, leading to disruption of tolerogenic circuits and development of autoimmune disorders. Galectin-1 (Gal1), an endogenous glycan-binding protein, has emerged as a regulator of immune cell homeostasis by shaping the fate of myeloid and lymphoid cells. Here, we demonstrate that aged Gal1-null mutant (Lgals1-/- ) mice develop a spontaneous inflammatory process in salivary glands that resembles Sjögren's syndrome. This spontaneous autoimmune phenotype was recapitulated in mice lacking ß1,6N-acetylglucosaminyltransferase V (Mgat5), an enzyme responsible for generating ß1,6-branched complex N-glycans, which serve as a major ligand for this lectin. Lack of Gal1 resulted in CD11c+ dendritic cells (DCs) with higher immunogenic potential, lower frequency of Foxp3+ regulatory T cells (Tregs), and increased number of CD8+ T cells with greater effector capacity. Supporting its tolerogenic activity, Gal1 expression decreased with age in autoimmunity-prone nonobese diabetic (NOD) mice. Treatment with recombinant Gal1 restored tolerogenic mechanisms and reduced salivary gland inflammation. Accordingly, labial biopsies from primary Sjögren's syndrome patients showed reduced Gal1 expression concomitant with higher number of infiltrating CD8+ T cells. Thus, endogenous Gal1 serves as a homeostatic rheostat that safeguards immune tolerance and prevents age-dependent development of spontaneous autoimmunity.