NF-kappa B: a new player in angiostatic therapy.

Angiogenesis is considered a promising target in the treatment of cancer. Most of the angiogenesis inhibitors in late-stage clinical testing or approved for the treatment of cancer act indirectly on endothelial cells. They either neutralize angiogenic growth factors from the circulation or block the signaling pathways activated by these growth factors. Another group of angiogenesis inhibitors are the direct angiostatic compounds. These agents have a direct effect on the endothelium, affecting cellular regulatory pathways, independently of the tumor cells. The reason that this category of agents is lagging behind regarding their translation to the clinic may be the lack of sufficient knowledge on the mechanism of action of these compounds. The transcription factor NF-kappaB has been recently connected with multiple aspects of angiogenesis. In addition, several recent studies report that angiogenesis inhibition is associated to NF-kappaB activation. This is of special interest since in tumor cells NF-kappaB activation has been associated to inhibition of apoptosis and currently novel treatment strategies are being developed based on inhibition of NF-kappaB. The paradigm that systemic NF-kappaB inhibition can serve as an anti-cancer strategy, therefore, might need to be re-evaluated. Based on recent data, it might be speculated that NF-kappaB activation, when performed specifically in endothelial cells, could be an efficient strategy for the treatment of cancer.