N-acetylcysteine inhibits endothelial cell invasion and angiogenesis

The thiol N-acetylcysteine (NAG) is a chemopreventive agent that acts throu gh a variety of mechanisms and can prevent in vivo carcinogenesis. We have previously shown that NAG inhibits invasion and metastasis of malignant cel ls as well as tumor take. Neovascularization is critical for tumor mass exp ansion and metastasis formation. We investigated whether a target of the an ti-cancer activity of NAG could be the inhibition of the tumor angiogenesis -associated phenotype in vitro and in vivo using the potent angiogenic mixt ure of Kaposi's sarcoma cell products as a stimulus. Two endothelial (EAhy9 26 and human umbilical vein endothelial [HUVE]) cell lines were utilized in a panel of assays to test NAG ability in inhibiting chemotaxis, invasion, and gelatinolytic activity in vitro. NAG treatment of EAhy926 and HUVE cell s in vitro dose-dependently reduced their ability to invade a reconstituted basement membrane, an indicator of endothelial cell activation. Invasion o f HUVE cells was inhibited with an ID50 of 0.24 mM NAG, whereas inhibition of chemotaxis required a 10 fold higher doses, indicating that invasion is a preferential target. NAG inhibited the enzymatic activity and conversion to active forms of the gelatinase produced by endothelial cells. The matrig el in vivo assay was used for the evaluation of angiogenesis; NAC strongly inhibited neovascularization of the matrigel sponges in response to Kaposi' s sarcoma cell products. NAC prevented angiogenesis while preserving endoth elial cells, implying that it could be safely used as an anti-angiogenic tr eatment.