New trends in tumor biology: transfection of a human hepatoblastoma cell line with green fluorescent protein

Current and future management strategies for relapsed or progressive hepatoblastoma

Hepatoblastoma is the most common primary malignant neoplasm of the liver in children. Improvements in chemotherapy and surgical techniques have increased survival rates for those with localized disease. The prognosis for patients with progressive or relapsed disease continues to be dismal. Complete resection by surgery or liver transplantation is necessary for cure. Few conventional chemotherapy agents have demonstrated activity in progressive or relapsed hepatoblastoma. Irinotecan has shown activity in relapsed and progressive hepatoblastoma. The efficacy of high-dose chemotherapy in this setting is unknown. Newer targeted agents that 'selectively' interfere with pathway targets involved in tumor growth and progression such as insulin-like growth factor, phosphatidylinositol 3-kinase (PI3K), Akt, and mammalian target of rapamycin (mTOR) are currently under development. Because of the rarity of hepatoblastoma, only a small minority of these agents will ever be evaluated in children with this disorder. Gene-directed therapy and immunotherapy have shown promising results in the preclinical setting, and should be investigated as future treatment options for advanced hepatoblastoma.

Optimizing vector application for gene transfer into human hepatoblastoma cells

Gene targeting is currently of distinct interest as an innovative additive treatment option in various malignancies. Its role in pediatric liver tumors has not yet been evaluated thoroughly. For the first time the authors systematically analyzed both lipid-based transfection as well as transduction with adenovirus vectors (Ad) and Sendai virus vectors (SeVV) in order to optimize gene transfer into hepatoblastoma (HB) cells. Two HB cell lines were infected with Ad or SeVV coding for green fluorescent protein (Ad-GFP, SeVV-GFP); transduction efficiencies and apoptosis were assessed using flow cytometry. Furthermore, lipofection of HB cell lines with plasmid-constructs comprising liver-specific promoters was performed using Lipofectamine 2000 and FuGENE 6; lipofection efficiency was monitored by flow cytometry, microscopy, and luciferase activity. The Ad-GFP showed higher transduction rates (61-86%) than the SeVV-GFP (4-24%) depending on the HB cell line used. Infections with first generation SeVV vectors (SeVV-GFP) led to increased target cell apoptosis (7-43%) compared to Ad-GFP (4-16%). The Lipofectamine 2000 revealed a higher transfection efficiency than the FuGENE 6 for both HB cell lines tested. The liver-specific promoters were found to be differently active in the HB cell lines. This study delineates recombinant adenovirus vectors as a promising tool for gene transduction in the HB cells. Furthermore, enhanced activity of the liver-specific promoters in HUH6 cells compared to HepT1 cells supports the observation of varying biological behavior in histologically differing HB tissues.

Visualization of xenotransplanted human rhabdomyosarcoma after transfection with red fluorescent protein

BACKGROUND/AIMS

Discosoma sp red fluorescent protein (DsRed2) is a newly developed marker for in vivo labeling studies in different biologic systems. After vector transfection, DsRed2 is expressed in mammalian cells and can be detected by fluorescence microscopy. The aims of this study were to establish a DsRed2-transfected human rhabdomyosarcoma (RMS) cell line and to perform a xenotransplantation on nude mice to use imaging as a tool for further basic research studies on this neoplasm.

PROCEDURE

The human alveolar RMS cell line Rh30 was transfected with the pDsRed2-N1 vector by lipofection. The DsRed2-positive cells were sorted out by fluorescence-activated cell sorting analysis 96 hours after transfection and selected in culture with G418. Expression of DsRed2 messenger RNA was assessed using single-cell reverse transcriptase polymerase chain reaction after laser microdissection. Transfected and parental cells were characterized cytologically, cytogenetically, immunohistochemically, and in vivo after subcutaneous injection in NMRI (nu/nu) nude mice.

RESULTS

After vector transfection, a pure and stable DsRed2-positive cell line was established by monoclonal growth of the cells. Reverse transcriptase polymerase chain reaction revealed constant expression of DsRed2 messenger RNA in fluorescencing cells. There was no difference between transfected and parental cells by means of cell morphology and desmin expression. Clonal cells (1 x 10(6)) were used for xenotransplantation. Tumors were visualized noninvasively through the skin of the mice using specific emission and excitation filters. Tumor vascularization and vessel growth could be discriminated from tumor tissue using this imaging system.

CONCLUSION

This is the first report on successful transfection of an RMS cell line with red fluorescent protein followed by xenotransplantation into nude mice. This model can serve as an imaging tool for in vivo studies investigating tumor biology and metastases of human RMS.

In vitro gene targeting in human hepatoblastoma

Poor treatment results in advanced hepatoblastoma (HB) made alternative treatment approaches desirable. Gene-directed tumor therapy is increasingly investigated in different malignancies. The aim of this study was to analyze possible alternatives of gene transfer into HB cells and to study therapeutic applications based on different strategies. Liposomal transfection of HB cells was assessed using liver-specific promoters, and adenovirus and Sendai virus transductions were performed in vitro. Transfer efficiencies were measured via flow cytometry determining expression of vector-encoded marker gene green fluorescent protein. Gene silencing of the anti-apoptotic bcl-2 gene in HUH6 cells was performed using lipofection of small interfering RNA (siRNA). Additionally, suicide gene therapy was carried out through a yeast-derived cytosine deaminase (YCD)-combined yeast uracil phosphoribosyltransferase (YUPRT)-based adenovirus-mediated gene transfer, leading to a potent intracellular prodrug transformation of 5-fluorocytosine into 5-fluorouracil. Treatment efficiencies were monitored via MTT viability assay. Highest gene transfer rates (86%) were observed using adenovirus transduction. We furthermore observed a significant therapeutic effect of adenovirus-mediated YCD::YUPRT suicide gene transfer. Liposomal-mediated anti-bcl-2 siRNA transfer led to a significant improvement of cisplatin treatment in HUH6 cells. Liver-specific promoters were found to be strongly active in HUH6 cells (mixed HB-derived), but less active in HepT1 cells (embryonal HB-derived). Liposomal transfection and viral transduction are effective approaches to genetically manipulate HB cells in vitro. For the first time, we demonstrate a positive effect of siRNA gene silencing in this malignancy. Additionally, we successfully investigated a model of adenovirus-based suicide gene therapy in HB cell cultures. Our data strongly encourage further studies assessing these alternative treatment approaches.