Low- dose Apatinib promotes vascular normalization and hypoxia reduction and sensitizes radiotherapy in lung cancer

Background and Purpose Abnormal vascular network of tumor can create a hypoxic microenvironment, and reduce radiotherapy sensitivity. Normalization of tumor vasculature can be a new therapeutic strategy for sensitizing radiotherapy. This study aimed to explore the effect of apatinib on vascular normalization, as well as the syngeneic effect with radiotherapy on lung cancer. Materials and Methods Lewis lung carcinoma (LLC) xenograft-bearing female C57BL/6 mice were treated with different doses of apatinib (30, 60, and 120 mg/kg per day) and/or radiation therapy (8 Gy/1F) and then sacrificed to harvest tumor tissue for immunohistochemical test. Further F-18-FMISO micro- PET in vivo explored the degree of hypoxia. Results Immunohistochemistry of CD31 and alpha-smooth muscle actin (alpha-SMA) proved that low-dose apatinib can normalize vasculature in tumor, especially on Day 10. Tissue staining of hypoxyprobe-1 and F-18-FMISO micro- PET in vivo showed that 60 mg/kg/day of apatinib significantly alleviates hypoxia. Moreover, this study further proved that low-dose apatinib (60 mg/kg/day) can enhance the radio-response of LLC xenograft mice. Conclusion Our data suggested that low- dose apatinib can successfully induce a vascular normalization window and function as a radio- sensitizer in the lung cancer xenografts model.