Ubiquitin-specific protease 22 (USP22), which plays an important role in the resistance to chemotherapy drugs in HCC and the prognosis of treated patients by virtue of its function as a key subunit of the Spt-Ada-Gcn5 acetyl transferase complex, deubiquitinates the sirtuin family member, SIRT1 (silent information regulator 1). The gene discussed is SIRT1; the disease is hepatocellular carcinoma.