When hypoxic environment advances, HIF1A is overexpressed and promoting upregulation of various target genes, including carbonic anhydrase IX (CAIX), a transmembrane glycoprotein to prevent intracellular acidosis, allowing breast cancer cells to undergo metabolic adaptation to hypoxia (Chen et al., 2010; Choi et al., 2013). Here, CA9 is linked to breast carcinoma.