Galectin-3 in mechanotransduction: implications for galectin-3 pro-angiogenic role

Abstract

The identification of multifunctional protein, present in the tumor and in microenvironment, may help the development of more specific cancer therapies. Many studies have shown that Galectin-3 (gal-3) plays an important role in tumor growth, progression, angiogenesis and metastasis. Modulation of gal-3 expression was described in different cancer cells and is showed to control extracellular matrix adhesion. Our group showed that the subcutaneously injected murine melanoma expressing gal-3 cells on wild type mice had lower necrotic areas and higher tumoral growth and vascularization compared to tumors derived from cells devoid of gal-3 expression. Recent data showed enhanced gal-3 expression around necrotic regions and tumor cell emboli from both primary tumors and metastatic lesions. The presence of tumor cells on vascular wall has already been reported. Tubulogenesis refers to the ability of endothelial cells to form tube-like structures while vasculogenic mimicry refers to tumor cells ability to mimic those tube-like structures. Silencing of gal-3 in HUVEC resulted in reduced tubulogenesis. Similar investigation on gal-3 silencing melanoma cells resulted in loss of tumor cell invasiveness and vasculogenic mimicry. Since signaling by mechanotransduction is very important for endothelial cells exposed to shear stress we postulate that it could be also important for tumor cells in contact with this flow. Shear stress effect on extracellular matrix and specifically gal-3 expression on melanoma cells remains elusive. Therefore, the hypothesis of this work consists on the effect of shear stress on melanoma cells that may induce changes on extracellular matrix and more specifically on secreted gal-3 expression, considering also the idea that those changes are responsible for the induction of vasculogenic mimicry in melanoma cells or tubulogenesis in endothelial cells. The aim of this project is to investigate the role of secreted gal-3 after mecanotransduction (by shear stress), as well as the importance of gal-3 on tumoral vasculogenic mimicry and endothelial tubulogenesis. The specific aims of this project are: i) to investigate gal-3 expression after extracellular matrix reorganization (by shear stress) on melanoma; ii) to investigate if extracellular matrix reorganization (induced by shear stress) induces vasculogenic mimicry or tubulogenisis by melanoma or endothelial cells (respectively); iii) to investigate the effect of gal-3 inhibition (GR-MD-02 ou shRNA) on melanoma or endothelial cells on the induction of vasculogenic mimicry or tubulogenisis (respectively); iv) to investigate if extracellular matrix reorganization (induced by shear stress) induce integrin cluster formation and FAK/SHP-2 signaling pathway on melanoma cells; v) to investigate if extracellular matrix reorganization induces melanoma cell migration; vi) to investigate tumoral angiogenic and vasculogenic mimicry protein expression (VE-cadherin; IL-8; VEGF; VEGFR2), after shear stress. Our preliminary results showed significant increase in gal-3 protein expression in culture medium and on extracellular matrix after shear stress (10dinas/cm2, 18h ). Interestingly, there was no change in gal-3 protein expression from total cell homogenate. Confocal microscopy analysis showed more fusiform morphology on cells submitted to shear stress. Overall, these data suggest that secretion of gal-3 protein is modulated by mechanotransduction and might be an interesting pathway to investigate pro-angiogenic mechanisms on tumor microenvironment.