CISD2 Haploinsufficiency Disrupts Calcium Homeostasis, Causes Nonalcoholic Fatty Liver Disease, and Promotes Hepatocellular Carcinoma

CISD2 is located within the chromosome 4q region frequently deleted in hepatocellular carcinoma (HCC). Mice with Cisd2 heterozygous deficiency develop a phenotype similar to the clinical manifestation of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Cisd2 haploinsufficiency causes a low incidence (20%) of spontaneous HCC and promotes HBV-associated and DEN-induced HCC; conversely, 2-fold overexpression of Cisd2 suppresses HCC in these models. Mechanistically, Cisd2 interacts with Serca2b and mediates its Ca2+ pump activity via modulation of Serca2b oxidative modification, which regulates ER Ca2+ uptake and maintains intracellular Ca2+ homeostasis in the hepatocyte. CISD2 haploinsufficiency disrupts calcium homeostasis, causing ER stress and subsequent NAFLD and NASH. Hemizygous deletion and decreased expression of CISD2 are detectable in a substantial fraction of human HCC specimens. These findings substantiate CISD2 as a haploinsufficient tumor suppressor and highlights Cisd2 as a drug target when developing therapies to treat NAFLD/NASH and prevent HCC.