Papel da fucana sulfatada FucSulf I na interação entre células tumorais e o endotélio in vitro

Abstract

To form metastasis, tumor cells must detach from primary tumor and migrate through the endothelial cell monolayer in direction of the bloodstream (intravasation). Once in the circulation, tumor cells must be able to adhere and migrate across the endothelium (extravasation) towards the target organ, where they will proliferate. Interaction between endothelial and tumor cells is mediated by selectins, followed by the interaction with integrins. Cancer cells frequently exhibit abnormal glycosylation patterns, resulting in the expression of selectins ligands formed by fucosylated polysaccharides, such as sialyl Lewis a/x. During metastatic process, tumor cells secrete several growth factors which can modulate different cell types that are present in the tumor microenvironment. These growth factors can also mediate autocrine signaling and activate signaling pathways involved in tumor cell proliferation and migration. Sulfated polysaccharides, as heparin, may act as P and E-selectin inhibitors as they may also bind to growth factors and interfere in their receptor activation. In this present work, we evaluated the role of sulfated fucans extracted from different marine invertebrates species (L. variegates, S. franciscanus, S. pallidus, A. lixula e S. droebachiensis) in the modulation of the interaction between tumor and endothelial cells in vitro and compared their effect with heparin. We also investigated the role of these molecules in the proliferation of tumor cells. For that, we used two prostate tumor cell lines (DU-145 and PC-3) and a primary culture of human umbilical vein endothelial cells (HUVECs). We first evaluated the effect of the fucans in the tumor cell adhesion to HUVECs. All fucans tested were able to inhibit the interaction between DU-145 and the endothelial cells, while only fucans extracted from L. variegates (FucSulf I) and S. franciscanus were able to inhibit the adhesion of PC-3. FucSulf I showed one of the most striking inhibitory effects in both cell lines and was the only one that inhibited adhesion of DU-145 to subendothelial matrix. It didn´t interfere with the adhesion of PC-3 to subendothelial matrix. FucSulf I was also able to decrease transendothelial migration of DU-145 and PC-3. Heparin had significant effect only in the transmigration assays, showing a similar inhibitory potencial in comparison with FucSulf I. VEGF increases endothelial permeability, thus facilitating the migration of tumor cells through the endothelial barrier. We observed that both tumor cell lines secrete VEGF and FucSulf I binds to this factor. These data suggest that the interaction between FucSulf I and VEGF may interfere in endothelial cell´s response to VEGF, and decrease transendothelial migration of tumor cells. We also showed that FucSulf I inhibits tumor cell proliferation in the absence of exogenous growth factors or in the presence of fetal bovine serum or VEGF. At least, we showed that FucSulf I interfered in the activation of specific proteins involved in signaling pathways triggered by growth factors. FucSulf I inhibited the activation of AKT in PC-3 tumor cell line, while inhibited the activation of ERK in DU-145 tumor cell line. These results indicate that FucSulf I modulates several steps of tumor progression and may be a potential candidate for use in antitumor therapies.