Galectin‐3 disruption impaired tumoral angiogenesis by reducing VEGF secretion from TGFβ1‐induced macrophages

• Published in: Cancer medicine (Malden, MA) MA), 2014-04, Vol.3 (2), p.201-214
• Main Authors: Machado, Camila Maria Longo, Andrade, Luciana Nogueira Sousa, Teixeira, Verônica Rodrigues, Costa, Fabrício Falconi, Melo, Camila Morais, dos Santos, Sofia Nascimento, Nonogaki, Suely, Liu, Fu‐Tong, Bernardes, Emerson Soares, Camargo, Anamaria Aranha, Chammas, Roger
• Format: Article
• Language: English
• Subjects: Angiogenesis; Animals; DNA Methylation; Galectin 3 - genetics; Galectin 3 - metabolism; galectin‐3; Humans; Macrophages - metabolism; Male; melanoma; Melanoma - blood supply; Melanoma - genetics; Melanoma - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Neovascularization, Pathologic - genetics; Neovascularization, Pathologic - metabolism; Original Research; Promoter Regions, Genetic; Transforming Growth Factor beta1 - genetics; Tumor Microenvironment; Vascular Endothelial Growth Factor A - biosynthesis; Vascular Endothelial Growth Factor A - metabolism
• ISSN: 2045-7634; 2045-7634
• DOI: 10.1002/cam4.173

In order to study the role of galectin‐3 in tumor angiogenesis associated with tumor‐associated macrophages (TAM) and tumor parenchyma, the galectin‐3 expression was reconstituted in Tm1 melanoma cell line that lacks this protein. Galectin‐3‐expressing cells (Tm1G3) and mock‐vector transfected cells (Tm1N3) were injected into wild‐type (WT) and galectin‐3 knockout (KO) C57Bl/6 mice. Tumors originated from Tm1G3 were larger in tumor volume with enlarged functional vessels, decreased necrotic areas, and increased vascular endothelial growth factor (VEGF) protein levels. Galectin‐3‐nonexpressing‐cells injected into WT and KO showed increased levels of transforming growth factor beta 1 (TGFβ1) and, in WT animals this feature was also accompanied by increased VEGFR2 expression and its phosphorylation. In KO animals, tumors derived from galectin‐3‐expressing cells were infiltrated by CD68+‐cells, whereas in tumors derived from galectin‐3‐nonexpressing‐cells, CD68+ cells failed to infiltrate tumors and accumulated in the periphery of the tumor mass. In vitro studies showed that Tm1G3 secreted more VEGF than Tm1N3 cells. In the latter case, TGFβ1 induced VEGF production. Basal secretion of VEGF was higher in WT‐bone marrow‐derived macrophages (BMDM) than in KO‐BMDM. TGFβ1 induced secretion of VEGF only in WT‐BMDM. Tm1G3‐induced tumors had the Arginase I mRNA increased, which upregulated alternative macrophage (M2)/TAM induction. M2 stimuli, such as interleukin‐4 (IL4) and TGFβ1, increased Arginase I protein levels and galectin‐3 expression in WT‐ BMDM, but not in cells from KO mice. Hence, we report that galectin‐3 disruption in tumor stroma and parenchyma decreases angiogenesis through interfering with the responses of macrophages to the interdependent VEGF and TGFβ1 signaling pathways. We have compared melanoma growth rates according the expression level of galectin‐3 in both tumor cells (parenchyma) and in the tumor microenvironment (wild‐type vs. KO mice). Altogether, when galectin‐3 is present in both tissue compartments, tumors grew faster and larger due to sustained angiogenesis, associated with increased VEGF production in response to transforming growth factor beta 1 (TGF‐β1). In this manuscript, we provided evidence for a role for galectin‐3 in shaping up an M2‐biased response that favors melanoma‐associated angiogenesis, and therefore, it will be a suitable target for therapeutic intervention.