Immunohistochemical Study of the Angiogenetic Network of VEGF, HIF1α, VEGFR-2 and Endothelial Nitric Oxide Synthase (eNOS) in Human Breast Cancer

The role of Nitric Oxide (NO) in angiogenesis has not been fully clarified yet. A dual role for NO, either inductive or inhibitory, has been proposed on the basis of different effects that high or low concentrations of NO may exert on the angiogenic process. Additionally, it has been referred that NO may induce VEGF production, while VEGF may induce NO production via up-regulation of the endothelial nitric oxide synthase (eNOS), the two pathways being reverse. The aim of the current study was to investigate the expression of key molecules involved in these opposite pathways in primary breast cancer. Representative tumor samples from 242 patients with early-stage breast cancer (invasive ductal breast carcinomas) were investigated for the expression of VEGF, VEGFR-2, HIF1 alpha, iNOS, and eNOS using immunohistochemistry. Endothelial NOS was found in 159 cases, VEGF in 131 cases, HIF-1 alpha in 139 cases, VEGFR2 in 185 cases and inducible NOS (iNOS) in 22 cases. There was a significant correlation between the expression of VEGF and VEGFR-2, eNOS and VEGF, eNOS and VEGFR-2, eNOS and HIF1 alpha. No statistically significant correlation was found between iNOS and the rest of the studied molecules. In breast cancer cases, the major molecules regulating NO and VEGF production can be co-expressed in the individual carcinomas implying a possibility for the relevant pathways to be active; however appropriate functional experiments remain to be conducted to prove such a hypothesis.