CA9 and neoplasm: The hypoxia-stimulated hypoxia-inducible factor-1 (HIF-1) is a key transcriptional factor accounting for the hypoxic effects by upregulating glucose metabolism-related genes, such as glucose transporter 1 and carbonic anhydrase 9 to adapt the anaerobic metabolism in tumor, and its downstream pro-angiogenic genes, including vascular endothelial growth factor (VEGF) and VEGF-receptor-2 (VEGFR2), therefore promoting tumor angiogenesis and progression3, 4.