Bcl-2 gene silencing in pediatric epithelial liver tumors

Background. Proteins of the Bcl-2 family prevent cells of various tumor types from undergoing apoptosis and thus contribute to their chemotherapy resistance. The phenotype of multidrug resistance is a major factor for poor treatment results of advanced epithelial liver tumors in children. The role of Bcl-2 proteins in these tumors is yet unclear. The purpose of this study was to analyze the influence of Bcl-2 on the chemotherapy resistance of hepatoblastoma (HB) and pediatric hepatocellular carcinoma (HCC). Materials and methods. Bcl-2 expression was analyzed in the HB cell lines HUH6 and HepT1 as well as in the HCC cell line HepG2 before and after treatment with cisplatin, doxorubicin, taxol, and etoposid. Silencing of the Bcl-2 gene was performed via RNA interference using specific siRNA. Treatment efficiencies of cytotoxic agents were assessed against original and Bcl-2 siRNA transfected tumor cells. Results. The mixed HB cell line HUH6 showed a relevant amount of Bcl-2 expression, which increased after chemotherapy. In these cells Bcl-2 appeared within the nuclei and the cytosol. Treatment with all cytotoxic agents was significantly improved through Bcl-2 siRNA (P < 0.001-0.0054) in this cell line. There was no effect of Bcl-2 siRNA in HepT1 and HepG2 cells. Conclusions. Bcl-2 seems to play a role in antiapoptotic mechanisms of some HB subtypes. Thus, this gene might serve as target for a gene-directed adjuvant therapy. Further studies seem necessary to clear the susceptibility of pediatric epithelial liver tumors toward the described approach. (c) 2008 Elsevier Inc. All rights reserved.