Tumor suppressor protein p53 mRNA and subcellular localization are altered by changes in cellular copper in human Hep G2 cells

Abstract

Copper toxicity causes hepatic damage that can lead to the development of hepatocarcinoma. Similarly, copper deficiency has been reported to increase hepatocyte tumorigenesis. Thus, the objective of this work was to explore the role of copper toxicity and deficiency in the regulation of the tumor suppressor protein p53. Using Northern analysis, Western analysis, immunocytochemistry and the human hepatoma cell line Hep G2, this work showed that elevations in hepatocyte copper consistent with Wilson's disease (5.7-fold increase) induced p53 mRNA and confirmed that copper toxicity is correlated with apoptotic cell death. However, Western analysis and immunocytochemistry showed that post-transcriptional mechanisms are a significant part of the process, with p53 translocation from the cytosol into the nucleus of copper-treated cells. Treatment of Hep G2 cells with increasing concentrations of the copper chelator tetraethylenepentamine (TEPA, 0-50 μmol/L, 48 h) reduced cellular copper and increased mean p53 mRNA abundance by over fourfold with nuclear translocation of the wild-type protein. However, TEPA treatment did not result in a loss of cell viability or appear to induce apoptosis.