Abstract #4591: Synergistic antiangiogenic and antitumoral effects of the combination of the flavonoid fisetin and cyclophosphamide in Lewis lung carcinoma bearing mice

In a research program aimed at finding new and non toxic antiangiogenic agents, we recently identified the natural flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) as a lead compound possessing a unique mechanism of action on endothelial cells involving microtubule stabilization (Touil et al., Nutrition and Cancer, in press). The purpose of the present study was to further investigate the antiproliferative and antiangiogenic properties of fisetin in vitro and in tumor bearing mice. In vitro, fisetin presented a dose-dependent decrease in viability of Lewis lung carcinoma cells (LLC) and EAhy 926 endothelial cells (EC) with an IC₅₀ of 28 µM for both cell lines (48 h). Compared to LLC and EC, the normal NIH 3T3 cells were interestingly less sensitive to fisetin (IC₅₀ = 136 µM). With regard to in vitro antiangiogenic properties, fisetin could decrease the EC migration and the capillary-like structure formation in a dose-dependent fashion. In vivo, fisetin could inhibit angiogenesis in the Matrigel plug assay. In LLC bearing mice, fisetin alone caused a 67% tumor growth inhibition when administered at non toxic dosage (223 mg/kg, i.p., days 4-8 and 11, 12, 14, post tumor implantation), whereas low dose cyclophosphamide alone (CPA, 30 mg/kg, s.c., days 4, 5, 7, 8) could induce a 66% tumor growth inhibition (day 15 post tumor implantation). When fisetin was combined with CPA (same dose and schedule as above), an interesting synergistic antitumoral action was observed with a 92% tumor growth inhibition on day 15 post tumor implantation. Histological examination of tumors showed a significant decrease in vessel density caused either by fisetin or CPA alone, whereas the tumors treated with the drug combination presented a dramatic and significant decrease of tumor microvessel density. In conclusion, fisetin alone was shown to inhibit tumor growth in vivo through an antiangiogenic mechanism and its combination with low dose CPA led to a synergistic tumor growth inhibition, without significant added toxicity (less than 5% body weight change). In conclusion, we have shown that the combination of the natural flavonoid fisetin with CPA was synergistic through their dual antiangiogenic and cytotoxic actions, and this relatively non toxic drug combination could advantageously be used in the treatment of solid tumors (supported by Inserm, CNRS, and INCa).

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 4591.