CA IX

Carbonic Anhydrase IX (CA IX) is a transmembrane protease in hypoxic microenvironments that can exert acid-base regulation by catalyzing the hydration of carbon dioxide to produce bicarbonate and protons. CA IX can be expressed in various organ tumors such as thyroid, lung, colon, breast, cervix, and ovary. Some research found that the hypoxic condition in high-density solid tumors can stimulate CAIX expression. The subsequently produced bicarbonate is transported into the cell to alkalize the internal environment and avoid cancer acidosis, while protons are expelled from the cell to activate protease degradation of the extracellular matrix and promote cancer infiltration and metastasis. Meanwhile, CA IX can enhance cell adhesion and promote tumor angiogenesis. In summary, CA IX plays an important role in the assessment of tumor malignancy. In addition, CA IX can serve as a specific diagnostic biomarker for renal clear cell carcinoma, but some scholars pointed out that patients with low expression of CA IX have shorter survival time and higher recurrence rate, so the prognostic value of CA IX still needs further research.