ABSTRACT
Purpose@#This study aimed to investigate the potential systemic antitumor effects of stereotactic ablativeradiotherapy (SABR) and apatinib (a novel vascular endothelial growth factor receptor2 inhibitor) via reversing the immunosuppressive tumor microenvironment for lung carcinoma. @*Materials and Methods@#Lewis lung cancer cells were injected into C57BL/6 mice in the left hindlimb (primary tumor;irradiated) and in the right flank (secondary tumor; nonirradiated). When both tumors grewto the touchable size, mice were randomly divided into eight treatment groups. These groupsreceived normal saline or three distinct doses of apatinib (50 mg/kg, 150 mg/kg, and 200mg/kg) daily for 7 days, in combination with a single dose of 15 Gy radiotherapy or not tothe primary tumor. The further tumor growth/regression of mice were followed andobserved. @*Results@#For the single 15 Gy modality, tumor growth delay could only be observed at the primarytumor. When combining SABR and apatinib 200 mg/kg, significant retardation of both primaryand secondary tumor growth could be observed, indicated an abscopal effect wasinduced. Mechanism analysis suggested that programmed death-ligand 1 expressionincreased with SABR was counteract by additional apatinib therapy. Furthermore, whenapatinib was combined with SABR, the composition of immune cells could be changed.More importantly, this two-pronged approach evoked tumor antigen–specific immune responsesand the mice were resistant to another tumor rechallenge, finally, long-term survivalwas improved. @*Conclusion@#Our results suggested that the tumor microenvironment could be managed with apatinib,which was effective in eliciting an abscopal effect induced by SABR.