A Tenascina-C e a sinalização celular na diferenciação tubulogênica endotelial

Abstract

The extracellular matrix (ECM) modulates both strong cell adhesion by inducing junctional complexes - and intermediate states of adhesion, where cells can differentiate, migrate and proliferate, depending on the signaling pathways activated by adhesion receptors. Tenascin-C is a matricellular protein widely secreted by glioma cells. It has a significant anti-adhesive activity and is involved in proliferation and tumor angiogenesis. Alves et al., 2011 observed that endothelial cells seeded on ECM of the U373 adhere less and are deficient in the ability to form tubes when compared with those plated on ECM of the HUVECs. This phenotype was reproducible with substrates for TN-C/FN mimetic of native tumor matrix composition. We also investigated whether the blockage of different domains of TN-C in glioma-derived matrix could revert this poor angiogenic phenotype. Pre-treatment of glioma-derived matrix with antibodies against FNIII-type 1-3 repeats, FNIII-type 4-5 repeats and the EGF-like N-terminal domain of TN-C partially rescued endothelial cell ability to form tubes. PKC-alpha activation has been previously implicated in the induction of tubulogenesis in Matrigel. By western blotting, we observed an increase in the phosphorylation of a threonin 638 - a possible inhibitory site PKC alpha protein - and in the threonine 505 of PKC delta leading to its inactivation - in tubulogenesis-defective endothelial cells previously incubated with ECM of gliomas. The antagonistic effect of these isoforms of PKC was demonstrated when we used selective inhibitors and activators of the PKCs. When HUVECs were incubated with ECM U373 MG in the presence of PMA, they rescued their ability to form tubes; pre-treatment of HUVECs with inhibitor of PKC δ (rottlerin) also partially rescued the tubulogenic ability of these cells. However, pre-treatment of HUVECs were seeded on the HUVEC ECM (which form tubes normally) with an inhibitor of PKC α (RO320432) led to impairment of tubulogenesis. Moreover, this matrix also induces activation of ERK and AKT. Our data suggest a role for TN-C-induced aberrant vascular phenotypes often observed in malignant gliomas can have the possible contribution of PKC-alpha inhibition, as well as of ERK and Akt activation, in endothelial cells exposed to tumor ECM.