Figure 7. Prolonged treatment with cephalexin is not required to enhance radiosensitizarion and suppress the growth of B16.SIY tumors.

A. Five day treatment of cephalexin (30 mg/kg twice daily) combined with 20 or 40 Gy (20 Gy + 20 Gy) suppressed tumor growth (n = 5 per group). B. Scatter plot of individual tumors in corresponding treatment groups at day 12 showing the distribution of tumor volumes and the presence of experimental outliers. Mean ± SEM are shown. C. Combined treatment with cephalexin + IR increased DNA damage, decreased tumor cell proliferation and enhanced senescence compared to treatment with 20 Gy or 20 Gy + 20 Gy in B16.SIY tumors. Representative images of γ-H2AX, Ki-67 and SA-β-Gal staining are shown. Scale bar 100 μm. D. Modeling the integration of cephalexin treatment with hypofractionated therapy indicates feasibility and potential efficacy. One to three cycles of a 3 day course of cephalexin (30 mg/kg twice daily) combined with 15 Gy suppressed tumor growth (10 groups, n = 6-7 per group, control, n = 5). Mean ± SEM are shown. E. Scatter plot of individual tumors in corresponding treatment groups at day 15 showing the distribution of tumor volumes and the presence of experimental outliers. Cycles of cephalexin alone had no significant effect on tumor growth. Significant tumor growth suppression (p < 0.05) was observed for IR treatment alone and all combined treatments, except for one outlier in the two cycle group (2 x cephalexin + 15 Gy, p = 0.06). Of note for each treatment cycle of cephalexin + IR the number of animals bearing tumor volumes smaller than 1000 mm³ was increased compare to all cycles of IR alone.