CA9 and hepatocellular carcinoma: Although CA9 exhibits the strongest relative importance, UCK2 and FABP5 also represent essential molecular drivers of HCC development and progression.UCK2 is a pyrimidine ribonucleotide kinase, catalyzing the phosphorylation of cytidine and uridine to produce uridine monophosphate and cytidine monophosphate, thereby participating in pyrimidine nucleotide metabolism (47).