Ppif deficiency promotes DEN-induced hepatocarcinogenesis by altering hepatocyte responses to carcinogenic stress.

Ppif (Cyclophilin D, CypD) is a key regulator of mitochondrial permeability transition pore (mPTP) opening and plays an important role in maintaining mitochondrial homeostasis by regulating mitochondrial calcium dynamics and redox balance. Although Ppif deficiency has been reported to alter basal mitochondrial function, its impact on hepatocyte responses to carcinogenic stress and hepatocarcinogenesis remains poorly understood. Here, we investigated how Ppif deficiency influences acute cellular responses to diethylnitrosamine (DEN) and the subsequent development of liver tumors. Primary hepatocytes isolated from Ppif -knockout mice exhibited increased basal oxygen consumption and elevated mitochondrial and cellular ROS levels compared with wild-type hepatocytes. Following DEN challenge, Ppif-deficient hepatocytes showed enhanced ROS, increased DNA damage, and greater HIF1α accumulation. Despite these enhanced stress responses, caspase-3 activation and hepatocyte death were attenuated in Ppif-deficient hepatocytes, suggesting altered cellular adaptation to DEN-induced injury. Consistent with these acute responses, chronic DEN treatment resulted in increased oxidative DNA damage, elevated Ki67-positive proliferating cells, and significantly enhanced liver tumor burden in Ppif-deficient mice. Collectively, our findings demonstrate that Ppif deficiency alters hepatocyte responses to carcinogenic stress by promoting the survival of damaged hepatocytes, thereby facilitating DEN-induced hepatocarcinogenesis. These findings identify Ppif as a critical regulator of hepatocyte responses to carcinogenic stress during liver tumor development.