Apatinib Suppresses Gastric Cancer Stem Cells Properties by Inhibiting Sonic Hedgehog Pathway

Abstract Background Gastric cancer stem cells (GCSCs) are considered as the basis of gastric carcinoma onset. Sonic Hedgehog (SHH) pathway plays a crucial role in maintaining GCSCs characteristics. Apatinib, a highly selective vascular endothelial growth factor receptor 2 (VEGFR-2) inhibitor, has been approved in China for the treatment of advanced gastric cancer after the failure of second-line therapy. To data, the effects of apatinib on GCSCs and the underlying mechanisms have not been elucidated yet.Methods Tumorsphere formation assay was used to enrich GCSCs from BGC-823 and SGC-7901 cells and the number of CD133-positive cells was examined by flow cytometry. Western blotting, immunofluorescence and immunohistochemistry assays were used to determine protein expression. Cell proliferation and apoptosis of GCSCs after apatinib treatment were evaluated by CCK8, colony formation, flow cytometry and Hoechst 33258 assays. Transient transfection assay was used to upregulate Gli1 expression in GCSCs. Nude mouse xenograft was used to investigate the suppressive effects of apatinib in vivo. Results We revealed that the levels of GCSCs markers and the number of CD133-positive cells were significantly elevated in the sphere-forming cells. We further illustrated that apatinib efficiently abolished GCSCs traits, as manifested by inhibition of tumorsphere formation, decreased expression of GCSCs markers, reduced number of CD133-positive cells, drug resistance protein suppression as well as proliferation inhibition and apoptosis induction. Furthermore, we found that apatinib downregulated the activation of SHH pathway, while upregulation of SHH pathway attenuated the inhibitory effects of apatinib on GCSCs. Furthermore, apatinib treatment significantly delayed tumor growth and inhibited GCSCs characteristics in xenograft model. Conclusions Taken together, our data suggested that apatinib exhibited its inhibitory effects on GCSCs via suppression of SHH pathway. These findings could provide new insights into the therapeutic application of apatinib in GCSCs suppression and advanced gastric cancer treatment.