CA9 and neoplasm: HIF-1 is able to promote the growth of endothelial cells after radiotherapy by inducing the expression of key downstream genes, including vascular endothelial cell growth factor (VEGF) (Ahn et al., 2014), carbonic anhydrase (CA9) (Chiche et al., 2009; Logsdon et al., 2016), and glucose transporter (GLUT1) (Dungwa et al., 2011), thus promoting the overall tumor radioresistance.