Molecular mechanisms of action of angiopreventive anti-oxidants on endothelial cells: microarray gene expression analyses

The anti-oxidants N-acetyl-l-cysteine (NAC) and (-)-epigallocatechin-3-gallate (EGCG) inhibit tumor vascularization by reducing endothelial cell migration and invasion in a similar, non additive and non synergistic manner but do not alter the growth of human umbilical vein endothelial cells. Here we address the effects of the two chemopreventive drugs on endothelial cell signaling by means of expression profiling and real-time PCR validation. We identify a series of angiogenesis related genes that are similarly regulated by the two drugs. Anti-oxidant treated endothelial cells show gene expression profiles compatible with a less activated, less apoptosis prone and less migratory phenotype. The anti-oxidants affect expression of several components of the TNFalpha response pathway including downstream genes that are regulated in the opposite direction in the absence of the inflammatory cytokine. The interference with the TNFalpha pathway is reflected by reduced NFkappaB activation in anti-oxidants treated cells but the compounds are not able to contrast TNFalpha mediated activation of NFkappaB. The chemopreventive action of these compounds thus relies on a reduction of basal levels of endothelial cell activation. Down-regulation of the TNFalpha responsive pro-metastatic, pro-inflammatory genes, urokinase plasminogen activator and selectin E, further implies anti-metastatic effects for these drugs.