As expected, FAM99B65-146 was able to downregulate the protein levels of DDX21, thereby inhibiting ribosome biogenesis and protein synthesis in HCC cells (Fig. 6H–J, Supplemental Fig. S7E–G), whereas FAM99B△65–146 showed no such effects (Fig. 6I, Supplemental Fig. S7F, G). Here, DDX21 is linked to hepatocellular carcinoma.