Molecular mechanism of the inhibitory effect of KS-5 on bFGF-induced angiogenesis in vitro and in vivo

Inhibition of angiogenesis controls the expansion and metastasis of many solid tumors and other related-diseases. KS-5 (1,7-dihydroxy-3-methoxyacridone), is an inactive analogue of the substituted 1-hydroxy acridone antiviral class. This study aimed at studying the effects of KS-5 on bFGF-induced angiogenesis in cultured human umbilical vein endothelial cells (HUVECs) in vitro and in vivo. KS-5 inhibited bFGF (10 ng/ml)-induced cell proliferation in a concentration-dependent manner, but did not exhibit significant cytotoxic effect examined by LDH release assay. KS-5 inhibited bFGF-induced angiogenesis was associated with decreasing DNA synthesis as evaluated by BrdU incorporation assay, and abrogating endothelial cell ERK1/2 and Akt protein phosphorylation, the major signaling pathways involved in cellular processes of angiogenesis. In addition, KS-5 also inhibited bFGF-induced phosphorylation of mTOR and the major downstream effectors, eIF4E and p70^S6K. Moreover, bFGF-induced protein synthesis was also inhibited by KS-5. Most importantly, KS-5 treatment in nude mice inhibited in vivo angiogenesis as revealed by Matrigel implant assay. In conclusion, the present study suggests that KS-5 has potential anti-angiogenetic effect for cancer therapy and other angiogenesis-dependent diseases.