The tumor microenvironment regulates
cancer initiation, progression and response to treatment. In particular, the immature
tumor vasculature may impede drugs from reaching
tumor cells at a lethal concentration. We and others have shown that
radiation therapy (RT) induces pericyte recruitment, resembling vascular normalization. Here, we asked whether radiation-induced
vascular remodeling translates into improved tissue distribution and efficacy of
chemotherapy. First, RT induced
vascular remodeling, accompanied by decreased
hypoxia and/or increased Hoechst perfusion in prostate PC3 and LNCaP and
Lewis lung carcinoma. These results were independent of the RT regimen, respectively 10 × 2 Gy and 2 × 12 Gy, suggesting a common effect. Next, using
doxorubicin as a fluorescent reporter, we observed that RT improves intra-tumoral
chemotherapy distribution. These effects were not hindered by anti-angiogenic
sunitinib. Moreover, sub-optimal doses of
doxorubicin had almost no effect alone, but significantly delayed
tumor growth after RT. These data demonstrate that RT favors the efficacy of
chemotherapy by improving tissue distribution, and could be an alternative chemosensitizing strategy.