PNPLA2 and lung cancer: Elevated levels of USP18 was reported to promote lipolysis, increase fatty acid oxidation and augment lung cancer growth; further investigation showed that USP18 directly stabilized adipose triglyceride lipase (ATGL) protein by removing Interferon-Stimulated Gene 15 (ISG15) from the conjugated complex, and stabilized Uncoupling Protein 1 (UCP1) via deubiquitination [53] (Fig. 3).