Concurrent administration of bevacizumab and radiation inhibits in vivo tumor vascularization To investigate the anti-angiogenic effect of bevacizumab in combination with radiation, we performed an in vivo angiogenesis assay in 4 groups of mice with H226 tumor xenografts growing in matrigel plugs (Figure 5): control IgG, bevacizumab alone (1 mg/kg twice a week x 4 doses), radiation alone of 8 Gy (2 Gy/fraction twice a week x 4 doses), and concurrent bevacizumab and radiation. There was a reduction of tumor blood vessels observed in find more mice treated with either bevacizumab or radiation alone. However, the
greatest reduction in tumor vascularization was observed in animals receiving both bevacizumab and radiation. The mean quantitative fluorescence of the tumor vasculature was significantly lower in the combined treatment group (22.9) in comparison to bevacizumab alone (34.8), radiation alone (35.2), and control group (47). This experiment suggested a synergistic interaction between bevacizumab and radiation (p = 0.0054). Figure 5 Activity of bevacizumab with and without radiation on blood vessel formation in tumor xenograft models. Four groups of mice with H226 tumors in Matrigel plugs were treated with: IgG (control), bevacizumab (B), radiation (X), and combined bevacizumab and radiation (B/X). Pictures depict the matrigel plugs with visible tumors and blood vessels (green signal of FITC-Dextran).
Bevacizumab augments tumor response MTMR9 to radiation In this experiment, four groups of mice bearing SCC1 or RG-7388 H226 xenografts (n = 8 tumors/treatment group/cell line) were treated with: control IgG, bevacizumab alone (1 mg/kg twice a week), radiation alone (twice a week with 2.5 Gy/fraction in SCC1 and 2 Gy/fraction in H226 models), or concurrent bevacizumab and radiation (Figure 6A). The SCC1 and H226 groups were treated for 4.5
weeks (9 treatments with a total irradiation dose of 22.5 Gy) and 2 weeks (4 treatments with a total dose of 8 Gy), respectively. The irradiation dose and treatment schedule was chosen based on our previous experience with the two cancer models. We have observed that the H226 xenograft model is significantly more sensitive to the anti-tumor effect from radiation than the SCC1 model. The results demonstrated that monotherapy with either bevacizumab or radiation inhibited tumor growth (Figure 6B and C). However, the MK5108 strongest inhibitory effect was observed with the concurrent administration of bevacizumab and radiation. Figure 6 Anti-tumor activity of bevacizumab and radiation given concurrently in SCC1 and H226 xenograft models. Four groups of mice with SCC1 and H226 tumors were treated with: IgG (control), bevacizumab (B), radiation (X), and concurrent bevacizumab and radiation (B/X). (A) Treatment schedule, and tumor growth inhibition in (B) SCC1 and (C) H226 models (n = 8 tumors per treatment group for each cell line).