Even reduced chemotherapeutic regimen with cisplatin monotherapy was recently proven to be as effective as cisplatin-doxorubicin combination in children with standard risk tumors. High risk hepatoblastoma, defined as tumor growth in all liver sections, vascular invasion, intra-abdominal extrahepatic extension, metastatic disease, a-fetoprotein less than 100 ng/mL at diagnosis is reported to have an event-free 3-year-survival of 65%, needing more extensive therapeutic strategies. In contrast to the continuously improving results of the standard group no landmarks in cases of high risk HB are made. Experimental anti-tumor therapies are frequently tested for efficacy in murine subcutaneous tumor models. Established HB cell lines that are currently used include the mixed HB cell line HuH6 and the embryonal HB cell line HepT1. For example studies of blockade of VEGF, or of modulation of multidrug resistance are carried out using these models. Tumor tumor volume can be assessed by calculation of xenograft measurement. However, the skin and subcutaneous tissue display a high inherent immunogenicity due to the abundant presence of antigen presenting cells and therefore subcutaneous tumors do not adequately mirror orthotopic tumour growth. Human tumors injected subcutaneously into mice usually grow as encapsulated masses with little evidence of local invasion or distant metastases. Orthotopic CT99021 252917-06-9 injection of tumors frequently enhances their tumorigenic and/or malignant properties. For intrahepatic growth of hepatic tumors some methods are described. If the cells do not spread after intraperitoneal or intravenous injection they can be injected into the liver, portal vein or spleen. Formation of hepatic metastases subsequent to intrasplenic injection of tumor cells was first described by Leduc in 1959. In case of hepatoblastoma Schnater et al. first described an intrahepatic growth of intrasplenically injected HuH6 cell-lines in 25% of treated NMRI nu/nu mice. These models were not used for testing of new therapeutic approaches, because of low tumor uptake. Our aim was to establish an improved model of orthotopic HB through alteration of essential parameters. The application of orthotopic tumor models in the liver implies a need for non-invasive techniques of tumor evaluation. For non-invasive tumor monitoring we used cell transfection with luciferase-genes for in vivo bioluminescence measurement and MRI. Models for hepatoblastoma are limited to three existing cell lines: HuH6 originating from an embryonal hepatoblastoma of a Japanese patient.