TNF-alpha induced DNA damage in primary murine hepatocytes

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, usually arising from a background of chronic inflammatory disease. Tumor necrosis factor alpha (TNF-alpha) is a pro-inflammatory cytokine produced in response to tissue injury, endotoxin exposure or infection and TNF-alpha signalling in hepatocytes is associated with an increase in oxidative stress. DNA is vulnerable to reactive oxygen species (ROS)-induced damage, which is highly mutagenic. Cells respond to DNA damage through the stabilisation of the tumor suppressor p53, which maintains genomic fidelity through induction of a cell cycle arrest in order to allow repair or elimination of the damaged cell through apoptosis. This study was carried out to determine if TNF-alpha caused oxidative DNA damage in primary cultures of murine hepatocytes and whether any damage would result in the induction of the tumor suppressor p53 and cell-cycle arrest. Using a modified Comet assay, to measure DNA damage we have demonstrated that TNF-alpha causes the formation of 8-oxo-deoxyguanosine (8-oxodG), an established marker of oxidative DNA damage, and a lesion associated with chronic hepatitis in human livers. In addition, the increase in DNA damage did not result in p53 stabilisation and TNF-alpha caused an increase in cell-cycle progression. We believe that this study indicates a possible putative role for TNF-alpha in the early stages of malignant transformation of hepatocytes.