CA9 and cancer: Previous studies have shown that lncRNA-low expression in tumors (lncRNA-LET) is involved in the inhibition of cell proliferation and cancer and metastasis suppression [99,100,214], while an opposite correlation was found between CA IX (an endogenous hypoxia marker and metabolism reprogramming factor) and lncRNA-LET during hypoxia in hepatocellular carcinoma [101,215].