Galectin-1 (Gal1), an evolutionarily conserved glycan-binding protein, contributes to the creation of an immunosuppressed microenvironment at sites of tumor growth. In spite of considerable progress in elucidating its role in tumor-immune escape, the mechanisms underlying the inhibitory functions of Gal1 remain obscure. Here, we investigated the contribution of tumor Gal1 to tumor growth, metastasis, and immunosuppression in breast cancer. We found that the frequency of Gal1 þ cells in human breast cancer biopsies correlated positively with tumor grade, while specimens from patients with benign hyperplasia showed negative or limited Gal1 staining. To examine the pathophysiologic relevance of Gal1 in breast cancer, we used the metastatic mouse mammary tumor 4T1, which expresses and secretes substantial amounts of Gal1. Silencing Gal1 expression in this model induced a marked reduction in both tumor growth and the number of lung metastases. This effect was abrogated when mice were inoculated with wild-type 4T1 tumor cells in their contralateral flank, suggesting involvement of a systemic modulation of the immune response. Gal1 attenuation in 4T1 cells also reduced the frequency of CD4cells within the tumor, draining lymph nodes, spleen, and lung metastases. Further, it abrogated the immunosuppressive function of T reg cells and selectively lowered the expression of the T-cell regulatory molecule LAT (linker for activation of T cells) on these cells, disarming their suppressive activity. Taken together, our results offer a preclinical proof of concept that therapeutic targeting of Gal1 can overcome breast cancer-associated immunosuppression and can prevent metastatic disease. Cancer Res; 73(3); 1107-17. Ó2012 AACR.

Galectin-1 (Gal-1), an evolutionarily conserved β-galactoside-binding lectin, plays essential roles in the control of inflammation and neovascularization. Although identified as a major component of the contractile apparatus of cardiomyocytes, the potential role of Gal-1 in modulating heart pathophysiology is uncertain. Here, we aimed to characterize Gal-1 expression and function in the infarcted heart. Expression of Gal-1 was substantially increased in the mouse heart 7 days after acute myocardial infarction (AMI) and in hearts from patients with end-stage chronic heart failure. This lectin was localized mainly in cardiomyocytes and inflammatory infiltrates in peri-infarct areas, but not in remote areas. Both simulated hypoxia and proinflammatory cytokines selectively up-regulated Gal-1 expression in mouse cardiomyocytes, whereas anti-inflammatory cytokines inhibited expression of this lectin or had no considerable effect. Compared with their wild-type counterpart, Gal-1-deficient (Lgals1(-/-)) mice showed enhanced cardiac inflammation, characterized by increased numbers of macrophages, natural killer cells, and total T cells, but reduced frequency of regulatory T cells, leading to impaired cardiac function at baseline and impaired ventricular remodeling 7 days after nonreperfused AMI. Treatment of mice with recombinant Gal-1 attenuated cardiac damage in reperfused AMI. Taken together, our results indicate a protective role for Gal-1 in normal cardiac homeostasis and postinfarction remodeling by preventing cardiac inflammation. Thus, Gal-1 treatment represents a potential novel strategy to attenuate heart failure in AMI.

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.