Gene therapy for liver diseases: recent strategies for treatment of viral hepatitis and liver malignancies

Leveraging stem cells to combat hepatitis: a comprehensive review of recent studies

Hepatitis is a significant global public health concern, with viral infections being the most common cause of liver inflammation. Antiviral medications are the primary treatments used to suppress the virus and prevent liver damage. However, the high cost of these drugs and the lack of awareness and stigma surrounding the disease create challenges in managing hepatitis. Stem cell therapy has arisen as a promising therapeutic strategy for hepatitis by virtue of its regenerative and immunomodulatory characteristics. Stem cells have the exceptional capacity to develop into numerous cell types and facilitate tissue regeneration, rendering them a highly promising therapeutic avenue for hepatitis. In animal models, stem cell therapy has demonstrated worthy results by reducing liver inflammation and improving liver function. Furthermore, clinical trials have been undertaken to assess the safety and effectiveness of stem cell therapy in individuals with hepatitis. This review aims to explore the involvement of stem cells in treating hepatitis and highlight the findings from studies conducted on both animals and humans. The objective of this review is to primarily concentrate on the ongoing and future clinical trials that assess the application of stem cell therapy in the context of hepatitis, including the transplantation of autologous bone marrow-derived stem cells, human induced pluripotent stem cells, and other mesenchymal stem cells. In addition, this review will explore the potential merits and constraints linked to stem cell therapy for hepatitis, as well as its prospective implications in the management of this disease.

Glycosylated 4-methylumbelliferone as a targeted therapy for hepatocellular carcinoma

BACKGROUND & AIMS

Reaching efficacious drug delivery to target cells/tissues represents a major obstacle in the current treatment of solid malignancies including hepatocellular carcinoma (HCC). In this study, we developed a pipeline to selective add complex-sugars to the aglycone 4-methylumbelliferone (4MU) to help their bioavailability and tumour cell intake.

METHODS

The therapeutic efficacy of sugar-modified rutinosyl-4-methylumbelliferone (4MUR) and 4MU were compared in vitro and in an orthotopic HCC model established in fibrotic livers. The mechanistic bases of its selective target to liver tumour cells were evaluated by the interaction with asialoglycoprotein receptor (ASGPR), the mRNA expression of hyaluronan synthases (HAS2 or HAS3) and hyaluronan deposition.

RESULTS

4MUR showed a significant antiproliferative effect on liver tumoural cells as compared to non-tumoural cells in a dose-dependent manner. Further analysis showed that 4MUR is incorporated mostly into HCC cells by interaction with ASGPR, a receptor commonly overexpressed in HCC cells. 4MUR-treatment decreased the levels of HAS2 and HAS3 and the cytoplasmic deposition of hyaluronan. Moreover, 4MUR reduced CFSC-2G activation, hence reducing the fibrosis. In vivo efficacy showed that 4MUR treatment displayed a greater tumour growth inhibition and increased survival in comparison to 4MU. 4MUR administration was associated with a significant reduction of liver fibrosis without any signs of tissue damage. Further, 60% of 4MUR treated mice did not present macroscopically tumour mass post-treatment.

CONCLUSION

Our results provide evidence that 4MUR may be used as an effective HCC therapy, without damaging non-tumoural cells or other organs, most probably due to the specific targeting.

HSVtk/GCV system on hepatoma carcinoma cells: Construction of the plasmid pcDNA3.1‑pAFP-TK and targeted killing effect

Previous studies demonstrated that herpes simplex virus thymidine kinase (HSVtk) could phosphorylate non-toxic gancyclovir (GCV) efficiently to produce phosphorylated products that result in cell apoptosis, to kill tumor cells. The present study aimed to construct a plasmid vector, pcDNA3.1-pAFP-TK, carrying the suicide gene driven by the alpha-fetoprotein (AFP) promoter, to investigate the cytotoxicity of HSVtk/GCV suicide gene system on hepatoma carcinoma cells. Reverse transcription-polymerase chain reaction and western blotting results demonstrated that the HSVtk gene was effectively expressed in HepG2 hepatoma carcinoma cells transfected with pcDNA3.1-pAFP-TK plasmid, whereas HSVtk gene expression was not detected in normal HL-7702 liver cells. In addition, MTT assays indicated that cell viability of HepG2 cells with the plasmid pcDNA3.1-pAFP-TK decreased in a dose-dependent manner following treatment with GCV for 48 h. Flow cytometry also revealed that the cell apoptosis rate and mitochondrial membrane potential reduction rate in the HepG2 cells treated with HSVtk/GCV suicide gene system were significantly higher than in the control group. Apoptosis rates in the control group and the pcDNA3.1-pAFP-TK group were (1.00±0.62%) and (38.70±6.03%), respectively. Mitochondrial membrane potential reduction rates in the control group and the pcDNA3.1-pAFP-TK group were (0.57±0.11%) and (22.84±5.79%), respectively. Caspase-3 staining demonstrated that activated caspase-3 increased significantly in the HepG2 cells treated with HSVtk/GCV suicide gene system, whereas in the control group activated caspase-3 increase was not observed. The results of the present study, therefore, indicated that HSVtk suicide gene was obviously expressed in the HepG2 cells and that the HSVtk/GCV system was effective at killing HepG2 hepatoma carcinoma cells.

Evaluation of miR-122-regulated suicide gene therapy for hepatocellular carcinoma in an orthotopic mouse model

OBJECTIVE

Intratumoral administration of adenoviral vector encoding herpes simplex virus (HSV) thymidine kinase (TK) gene (Ad-TK) followed by systemic ganciclovir (GCV) is an effective approach in treating experimental hepatocellular carcinoma (HCC). However, hepatotoxicity due to unwanted vector spread and suicide gene expression limited the application of this therapy. miR-122 is an abundant, liver-specific microRNA whose expression is decreased in human primary HCC and HCC-derived cell lines. These different expression profiles provide an opportunity to induce tumor-specific gene expression by miR-122 regulation.

METHODS

By inserting miR-122 target sequences (miR-122T) in the 3' untranslated region (UTR) of TK gene, we constructed adenovirus (Ad) vectors expressing miR-122-regulated TK (Ad-TK-122T) and report genes. After intratumoral administration of Ad vectors into an orthotopic miR-122-deficient HCC mouse model, we observed the miR-122-regulated transgene expression and assessed the antitumor activity and safety of Ad-TK-122T.

RESULTS

Insertion of miR-122T specifically down-regulated transgene expression in vitro and selectively protected the miR-122-positive cells from killing by TK/GCV treatment. Insertion of miR-122T led to significant reduction of tansgene expression in the liver without inhibition of its expression in tumors in vivo, resulting in an 11-fold improvement of tumor-specific transgene expression. Intratumoral injection of Ad vectors mediated TK/GCV system led to a vector dosage-dependent regression of tumor. The insertion of miR-122T does not influence the antitumor effects of suicide gene therapy. Whereas mice administrated with Ad-TK showed severe lethal hepatotoxicity at the effective therapeutic dose, no liver damage was found in Ad-TK-122T group.

CONCLUSIONS

miR-122-regulated TK expression achieved effective anti-tumor effects and increased the safety of intratumoral delivery of adenovirus-mediated TK/GCV gene therapy for miR-122-deficient HCC.

Therapeutic vaccination in chronic hepatitis B: preclinical studies in the woodchuck

Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to a satisfactory result. Induction of HBV-specific T cells by therapeutic vaccination or immunotherapies may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients did not result in effective control of HBV infection, suggesting that new formulations of therapeutic vaccines are needed. The woodchuck (Marmota monax) is a useful preclinical model for developing the new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments with nucleos(t)ide analogues, DNA vaccines, and protein vaccines were tested in the woodchuck model. In this paper we summarize the available data concerning therapeutic immunization and gene therapy using recombinant viral vectors approaches in woodchucks, which show encouraging results. In addition, we present potential innovations in immunomodulatory strategies to be evaluated in this animal model.

Therapeutic effect of alpha-fetoprotein promoter-mediated tBid and chemotherapeutic agents on orthotopic liver tumor in mice

Previous studies have shown that the application of Ad/AFPtBid significantly and specifically killed hepatocellular carcinoma (HCC) cells in culture and subcutaneously implanted in mice. This study was to test the therapeutic efficacy of Ad/AFPtBid in an orthotopic hepatic tumor model. Four weeks after implantation of tumor cells into the liver, nude mice were treated with Ad/AFPtBid alone or in combination with 5-fluorouracil (5-FU). Serum alpha-fetoprotein (AFP) was measured as a marker for tumor progression. The results showed that Ad/AFPtBid significantly inhibited Hep3B tumor growth. Ad/AFPtBid and 5-FU in combination was more effective than either agent alone. Tumor tissues of Ad/AFPtBid alone or combination treatment groups showed a decrease in cells positive for proliferation cell nuclear antigen, but an increase in apoptosis. Ad/AFPtBid did not suppress the hepatic tumor formed by non-AFP-producing hepatoma SK-HEP-1 cells or colorectal adenocarcinoma DLD-1 cells. The survival rate was higher in mice treated with Ad/AFPtBid plus 5-FU than those treated with either agent alone. No acute toxic effect was observed in mice receiving Ad/AFPtBid. Collectively, Ad/AFPtBid can specifically target and effectively suppress the AFP-producing orthotopic liver tumor in mice without obvious toxicity, indicating that it is a promising tool in combination with chemotherapeutic agents for treatment of AFP-producing HCC.

Targeted RNA interference for hepatic fibrosis

Hepatic fibrosis is a common consequence in patients with chronic liver damage. To date, no agent has been approved for the treatment of hepatic fibrosis. RNA interference (RNAi) is known to be a powerful tool for post-transcriptional gene silencing and has opened new avenues in gene therapy. The problems of lack of cell specificity in vivo and subsequently the occurrence of side effects has hampered the development of hepatic fibrosis treatment. To overcome these shortcomings, several targeted strategies have been developed, such as hydrodynamics-based approaches, local administration, cell-type-selective ligands and cell-type-specific promoters or enhancers, etc. Here, we provide an overview of targeted strategies for the treatment of hepatic fibrosis, and particularly, targeted RNAi for hepatic fibrosis.

Biotinylated disulfide containing PEI/avidin bioconjugate shows specific enhanced transfection efficiency in HepG2 cells

Targeting of non-viral gene vectors to liver cells could offer the opportunity to cure liver diseases. In this paper, disulfide-containing polyethylenimine (PEI-SS) was synthesized from low molecular weight branched PEI and cystamine bisacrylamide (CBA), and then grafted with biotin. The obtained biotinylated PEI-SS was bioconjugated with avidin via the biotin-avidin interaction to form a novel gene vector, biotinylated PEI-SS/avidin bioconjugate (ABP-SS). Characteristics of ABP-SS and its pDNA complexes were evaluated in terms of acid-base titration, agarose gel electrophoresis, SEM morphology observation, particle size and zeta-potential measurements, and PEI-SS was used as the control. The acid-base titration results showed that ABP-SS exhibited comparable buffer capability to 25 kDa PEI. The results of gel electrophoresis indicated that ABP-SS was able to condense pDNA efficiently at an N/P ratio of 6 and could be degraded by reducing agent DTT. The ABP-SS/pDNA complexes had a mean particle size of 226 +/- 40 nm and surface charges of 25 mV. The SEM images showed that the complexes had compact structures with spherical or quadrate shapes. In vitro cell viability and transfection of ABP-SS and PEI-SS were compared in HepG2, 293T and H446 cells. Among the three different cell lines, compared with PEI-SS, ABP-SS exhibited much lower cytotoxicity and higher transfection efficacy in HepG2 cells due to the biocompatibility of avidin and the specific interactions between avidin and HepG2 cells. Molecular probes were used to reveal the cellular uptake of complexes, and the results demonstrated that ABP-SS contributes to more cellular uptake of complexes in HepG2 cells, which was consistent with the transfection results.

High Efficiency and Long-Term Foreign Gene Expression in Cultured Liver Sinusoidal Endothelial Cells by Retroviral Transduction

The liver sinusoidal endothelial cells (LSECs) constitute a very specialized endothelium. Due to their multiple functions and privileged location in the liver, these cells constitute an excellent target for gene therapy. In this work, the authors investigate the efficiency of retroviral gene transduction as a method for in vitro gene delivery into murine LSECs. Gene transduction into murine LSECs was performed using the PCMMP-eGFP/pIK-MLVgp retrovirus pseudotyped with the vesicular stomatitis virus G glycoprotein (VSV-g), containing eGFP as a reporter gene. Retroviral transduction resulted in a high efficiency of gene transfer (99%) and stable expression of eGFP in LSECs. The retroviral transduction protocol did not affect the morphology or expression of endothelial cell markers or the biological functions of LSECs. The authors have developed conditions for high-efficiency and stable retroviral gene transduction of LSECs. These results raise the possibility of liver gene therapy using LSECs as vehicle for the delivery of therapeutic proteins by means of retroviral vectors.

Management strategies for hepatitis C virus infection in children

Chronic hepatitis C virus (HCV) infection is a major cause of morbidity and mortality worldwide. Progression to cirrhosis and hepatocellular carcinoma occurs in 20% of infected adults. The natural history following childhood infection is less well defined, although cirrhosis in children is described. Since blood product screening for HCV infection was introduced in 1990, most children who acquire HCV do so by vertical transmission from an infected mother. Transmission to offspring occurs in approximately 5%. Most children with HCV infection are asymptomatic. Diagnosis is made by testing those at risk for HCV RNA by polymerase chain reaction (PCR) and HCV antibody (anti-HCV) by enzyme immunoassay (EIA). The clinical impact of HCV infection is assessed by monitoring symptoms and signs, blood testing of liver enzymes, ultrasound imaging, and by liver biopsy. Improved efficacy and tolerability of treatment strategies in adults have had a significant impact on the management of children with HCV infection. The emphasis is now on promoting awareness, early diagnosis, and treatment. Treatment strategies have evolved from monotherapy with interferon alfa (IFNalpha), to combination therapy with ribavirin. Pegylated IFNalpha is superior to conventional IFNalpha, and forms the basis of current recommendations. The genotype of HCV influences treatment efficacy. Treatment is generally well tolerated in children, although adverse effects are common. Preparation and support throughout treatment for the whole family is needed. A proportion of children with HCV infection have co-morbidity, including viral co-infection or hematologic disease. Although treatment may be contraindicated, risks and benefits must be considered before denying treatment. Anemia is more common in those with HIV co-infection, renal insufficiency, thalassemia, or cirrhosis, and may be aggravated by treatment. Children with thalassemia may have iron overload, and transfusion requirements may increase during treatment. Further refinements of combination therapy and development of new drugs are in progress. Vaccine candidates are undergoing phase I and II treatment trials.

Liver sinusoidal endothelial cells as possible vehicles for gene therapy: a comparison between plasmid-based and lentiviral gene transfer techniques

Liver sinusoidal endothelial cells (LSECs) constitute an attractive target for gene therapy of several liver and systemic diseases. However, there are few reports showing an efficient plasmid-based or viral methodology to deliver recombinant genes into these cells. In the present study, the authors evaluated in vitro gene transfer efficiency of standard plasmid-based techniques (i.e., electroporation, lipofection, and calcium phosphate) and lentiviral-mediated gene transduction into primary murine LSECs, using reporter genes. The results show that electroporation is the most effective in vitro plasmid-gene transfer method to deliver GFP into LSECs (31%), as compared with lipofection and calcium phosphate transfection (6% and 4%, respectively). However, lentiviral transduction resulted in higher, efficient, and stable gene transfer (70%) as compared with plasmid-based techniques.

CONCLUSIONS

The highly efficient gene expression obtained by lentiviral transduction and electroporation shows that these methodologies are highly reliable systems for gene transfer into LSECs.

Treatment of hepatocellular carcinoma by AdAFPep/rep, AdAFPep/p53, and 5-fluorouracil in mice

Although conditionally replicable adenovirus (CRAd) has been used in the clinical treatment of hepatocellular carcinoma (HCC), it suffers from the inherent drawback of having relatively low antitumor activity. Here, we have sought to overcome this drawback. First, we combined CRAd (AdAFPep/Rep) driven by alpha-fetoprotein enhancer/promoter (AFPep) with a replication-incompetent adenovirus carrying a p53 transgene that is also driven by AFPep. The synergism of this combination produced a significantly improved tumoricidal effect on the human HCC cell line Hep3B, which has a relatively short doubling time in comparison with other human HCC cell lines, through the transactivation of p53 by early region 1A transcribed by AdAFPep/Rep. This synergistic interaction was augmented by the addition of a subtumoricidal dose (0.5 microg/mL) of 5-fluorouracil (5-FU), which enhanced p53 expression and facilitated the release of virions from tumor cells. When relatively large (10-mm-diameter) Hep3B tumors grown in nude mice were injected with the two viruses in combination, they showed significantly impaired growth in comparison with those treated with each virus separately. The growth suppression effect of the virus combination was enhanced by a low dose (600 microg) of 5-FU. Survival of the tumor-bearing mice treated with these three agents was significantly longer than that of control mice. Moreover, the tumor completely disappeared with the repeated injection of these agents.

CONCLUSION

This combination strategy holds promise for the treatment of relatively large and rapidly growing HCCs that may be encountered clinically.

The chimeric cytokine Hyper-IL-6 enhances the efficiency of lentiviral gene transfer in hepatocytes both in vitro and in vivo

Lentiviral vectors have been used for gene transfer into the liver but their ability to efficiently transduce quiescent hepatocytes remains controversial. Lentivirus-mediated gene transfer is more efficient in cycling cells. We determine the effect of H-IL6 in the lentiviral transduction. The lentiviral vector was used to transduce HepG2 cells and mice liver cells, previously treated with H-IL6. The highest transduction level was observed in HepG2 cells treated with 30 ng/mL H-IL6 and in the mice that received 4 microg H-IL6. Our results suggest that H-IL6 is an inducer of lentiviral gene transfer into the liver cells without any toxicity.

Plasminogen fragment K1-5 improves survival in a murine hepatocellular carcinoma model

BACKGROUND

The prognosis of patients with hepatocellular carcinoma (HCC) remains poor, and new alternative treatments are needed.

AIMS

To comparatively test the angiostatic and antitumour effects of adenoviral gene transfer of angiostatin (PlgK1-4, amino acids 1-440) and full kringles 1-5 (PlgK1-5, amino acids 1-546) in a model of subcutaneously transferred HCC in mice.

METHODS

PlgK1-4 and PlgK1-5 were generated from human WtPlg cDNA and used for adenovirus construction. Vector function and angiostatic effects were confirmed in vitro and in vivo. Antitumoral efficacies of intratumoral vector injections were studied in a model of subcutaneously transferred HCC model.

RESULTS

Cell supernatants containing PlgK1-4 and PlgK1-5 reduced endothelial tube formation in vitro by about 30%, whereas WtPlg exerted no inhibitory effect. Endothelial cell infiltration in vivo was decreased by about 60%, but not in AdWtPlg-treated animals. Intratumoral treatment of subcutaneous HCC tumours inhibited growth by 40% for AdPlgK1-4 and 63% for AdPlgK1-5 in surviving mice 12 days after initiation of treatment, whereas treatment with AdWtPlg even led to accelerated growth. Although PlgK1-4 and PlgK1-5 have similar inhibitory effects on intratumoral microvessels, PlgK1-5 markedly improved the survival time compared with PlgK1-4.

CONCLUSION

PlgK1-5 and PlgK1-4 effectively inhibited HCC growth. As PlgK1-5 could also prolong the survival time, inducing complete tumour elimination in half of the AdPlgK1-5-treated mice, PlgK1-5 might be the most potential plasminogen fragment for treatment of experimental HCC.

Adenovirus-mediated tBid overexpression results in therapeutic effects on p53-resistant hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide with a very high mortality. Because the success of the conventional therapies is limited, gene therapy may represent an alternative for HCC management. Our earlier study has shown that Bid plays a role in the development of HCC. The aim of our study is to evaluate the possibility of using truncated Bid (tBid) as a novel therapy for HCC treatment. Two HCC cell lines, Hep3B and PLC/PRF/5, were used in the experiment. Hep3B was a p53-resistant while PLC/PRF/5 a p53-sensitive. A recombinant adenovirus-Ad/AFPtBid, which contained a tBid gene driven by an alpha-fetoprotein (AFP) promoter, was constructed. Both Hep3B and PLC/PRF/5 cells infected with Ad/AFPtBid showed a significant decrease in cell viability. The decrease in cell viability by Ad/AFPtBid resulted from apoptosis of HCC cells, evident by enhanced activity of caspases and increased release of cytochrome c. In vivo experiment was performed by the intratumor injection of Ad/AFPtBid in nude mice inoculated with Hep3B. Ad/AFPtBid injection significantly inhibited tumor growth, and tumor tissues showed a marked increase in TUNEL-positive cells. Our experiment also demonstrated that Ad/AFPtBid only targeted AFP-producing cells but not those non-AFP producing cells. In conclusion, these results indicate that the introduction of Ad/AFPtBid can not only significantly but specifically kill HCC cells that produce AFP. The cell death induced by Ad/AFPtBid in HCC cells is via an apoptotic pathway that can be independent of p53 status.

Therapeutic possibilities of plasmonically heated gold nanoparticles

Nanoparticles of gold, which are in the size range 10-100 nm, undergo a plasmon resonance with light. This is a process whereby the electrons of the gold resonate in response to incoming radiation causing them to both absorb and scatter light. This effect can be harnessed to either destroy tissue by local heating or release payload molecules of therapeutic importance. Gold nanoparticles can also be conjugated to biologically active moieties, providing possibilities for targeting to particular tissues. Here, we review the progress made in the exploitation of the plasmon resonance of gold nanoparticles in photo-thermal therapeutic medicine.

Promyelocytic leukemia protein-induced growth suppression and cell death in liver cancer cells

The promyelocytic leukemia protein (PML), involved in the pathogenesis of acute promyelocytic leukemia, is a coactivator of p53 tumor suppressive functions. The ability of PML to inhibit growth and induce cell death in solid tumor cells, however, has not been determined. We therefore assayed the tumor suppressor activities of PML and compared them with those of p53 in four liver cancer cell lines. Following infection of cells with replication-deficient recombinant PML adenovirus, the exogenous PML localized in the nucleus and formed abnormally enlarged PML-nuclear bodies after 24 hours. In vitro growth curve analysis showed that the overexpressed PML initially induced a substantial G1 cell cycle arrest and triggered massive cell death in all tested cell lines, irrespective of their p53 status. PML-induced cell death decreased by about 30% in the presence of a broad caspase inhibitor, zVAD. The cell death effect of PML was higher than that induced by p53 over a longer period of time. As with p53, overexpression of PML was closely related to upregulation of p21 and decrease of cyclin D1 expression. Unexpectedly, retinoic acid (RA) antagonized rather than enhanced PML-triggered cell death. RA enhanced the expression of adenovirus-cytomegalovirus-promoted PML at both transcription and protein levels within 12 hours after treatment; however, the PML protein was significantly degraded in the presence of RA at days 3-5 postinfection. PML degradation was also observed in SK-BR3 breast cancer cells treated with RA. Taken together, our findings strongly support the hypothesis that PML acts as a strong independent cell death inducer and that RA conversely abolishes the therapeutic effects of the PML proteins through proteasomal degradation of the protein.

Naked DNA for Liver Gene Transfer

The majority of acquired and inherited genetic disorders, including most inborn errors of metabolism, are manifested in the liver. Therefore, it is hardly any surprise to see a large number of Medline reports describing gene therapy efforts in preclinical settings directed toward this organ (Inoue et al., 2004; Oka and Chen, 2004). Of late, non-viral vectors have garnered a lot of attention from the biomedical research community engaged in liver gene therapy (Gupta et al., 2004). However, the first initiative toward gene transfer to the liver using a non-viral approach was taken by Hickman et al. (1994), who applied the technique of naked DNA injection pioneered by Wolff (1990) for skeletal muscle. Direct injection of naked DNA resulted in low, variable and localized gene expression in the rat liver. Consequently, several developments reported in the literature since then aimed to improve hepatic gene expression by employing both surgical and nonsurgical methods. These developments include the exploitation of the unique vasculature of liver as well as the use of electric and mechanical force as an adjunct to the systemic administration of the naked plasmid gene. This chapter focuses on these developments reported from various laboratories, including ours. In addition, the underlying mechanism responsible for the dramatic increase in gene expression using these latest approaches for non-viral gene transfer to the liver is also discussed.

Combined gene therapy of endostatin and interleukin 12 with polyvinylpyrrolidone induces a potent antitumor effect on hepatoma

AIM: To study the antitumor effect of combined gene therapy of endostatin and interleukin 12 (IL-12) with polyvinylpyrrolidone (PVP) on mouse transplanted hepatoma.

METHODS: Mouse endostatin eukaryotic plasmid (pSecES) with a mouse Igκ signal sequence inside and mouse IL-12 eukaryotic plasmid (pmIL-12) were transfected into BHK-21 cells respectively. Endostatin and IL-12 were assayed by ELISA from the supernant and used to culture endothelial cells and spleen lymphocytes individually. Proliferation of the latter was evaluated by MTT. H22 cells were inoculated into the leg muscle of mouse, which was injected intratumorally with pSecES/PVP, pmIL-12/PVP or pSecES + pmIL-12/PVP repeatedly. Tumor weight, serum endostatin and serum IL-12 were assayed. Tumor infiltrating lymphocytes, tumor microvessel density and apoptosis of tumor cells were also displayed by HE staining, CD31 staining and TUNEL.

RESULTS: Endostatin and IL-12 were secreted after transfection, which could inhibit the proliferation of endothelial cells or promote the proliferation of spleen lymphocytes. Tumor growth was highly inhibited by 91.8% after injection of pSecES + pmIL-12/PVP accompanied by higher serum endostatin and IL-12, more infiltrating lymphocytes, fewer tumor vessels and more apoptosis cells compared with injection of pSecES/PVP, pmIL-12/PVP or vector/PVP.

CONCLUSION: Mouse endostatin gene and IL-12 gene can be expressed after intratumoral injection with PVP. Angiogenesis of hepatoma can be inhibited synergisticly, lymphocytes can be activated to infiltrate, and tumor cells are induced to apoptosis. Hepatoma can be highly inhibited or eradiated.

Chimeric transcriptional control units for improved liver-specific transgene expression

Hepatocyte-directed delivery of therapeutic genes is a major field of gene therapy. An important issue in this context is the availability of promoters units providing for maximum transcriptional activity and specificity. Although a number of liver-specific promoters and transcriptional control elements have been identified and used for gene delivery, no systematic study has been performed to identify the best suitable combination of known liver-specific promoter and enhancer elements. We now report the results of a comparative investigation addressing this issue. We tested a total of 25 synthetic transcriptional control units consisting of either of the four core promoters from liver-specific genes linked in various combinations and configurations to hepatocyte-specific enhancer elements. These constructs were analyzed for transcriptional activity in different cell types in cell culture and in mouse liver in vivo. The data lead to the clear conclusion that a combination of the alcohol dehydrogenase 6 (ADH6) basal promoter linked to two tandem copies of an apoplipoprotein E enhancer element is the transcriptional control unit of choice for the liver-specific expression of transgenes.

Prolonged and inducible transgene expression in the liver using gutless adenovirus: a potential therapy for liver cancer

BACKGROUND AND AIMS

Gene therapy of liver diseases would benefit from systems allowing prolonged, regulable, and tissue-specific transgene expression. We attempted to produce a vector fulfilling these requirements.

METHODS

We generated gutless adenoviral vectors containing a mifepristone (RU486)-inducible system for controlled and liver-specific expression of human interleukin-12 (hIL-12) (GL-Ad/RUhIL-12) and mouse IL-12 (mIL-12) (GL-Ad/RUmIL-12). The properties of these vectors were tested both in vitro and in vivo.

RESULTS

Infection of cells with GL-Ad/RUhIL-12 resulted in high level of hIL-12 expression in the presence of RU486 only in hepatocytic cells. In animals injected with GL-Ad/RUhIL-12, the administration of RU486 induced a transient rise of serum hIL-12 that peaked at 10 hours and completely disappeared by 72 hours. The peak value of hIL-12 was dependent on the doses of the vector and the inducer. High and sustained serum levels of hIL-12 could be attained by continuing administration of RU486 every 12 or 24 hours. Repetitive induction of hIL-12 could be obtained over, at least, a period of 48 weeks after a single injection of GL-Ad/RUhIL-12. Although the vector was detected in many tissues after systemic injection, transcription of the transgene was only found in the liver. Treatment of liver metastases with 5 x 10(8) infectious units of GL-Ad/RUmIL-12 plus RU846 resulted in complete tumor regression in all animals.

CONCLUSION

Gutless adenoviral vectors allow liver-specific and regulable transgene expression for prolonged periods of time. These vectors are promising tools for gene therapy of liver cancer and could also be useful for other forms of hepatic disease.

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Construction of a regulable gene therapy vector targeting for hepatocellular carcinoma

AIM: To construct a gene modified hepatocellular carcinoma (HCC) specific EGFP expression vector regulated by abbreviated cis-acting element of AFP gene.

METHODS: The minimal essential DNA segments of AFP gene enhancer and promoter were synthesized through PCR from Genome DNA of HepG2 cells. Gene fragments were then cloned into the multiple cloning site of non-promoter EGFP vector pEGFP-1. Recombinant plasmid was transferred into positive or negative AFP cell lines by means of lipofectamine. The expression of EGFP was tested by fluorescence microscope and flow cytometry. The effect of all-trans retinoic acid (ATRA) on the expression of EGFP was tested in different concentrations.

RESULTS: By the methods of restriction digestion and sequence analyses we confirmed that the length, position and orientation of inserted genes of cis-acting element of AFP were all correct. The transcription of EGFP was under the control of AFP cis-acting element. The expressing EGFP can only been detected in AFP producing hepatoma cells. The expression rate of EGFP in G418 screened cell line was 34.9% ± 4.1%. 48 h after adding 1 × 10^-7 M retinoic acid, EGFP expression rate was 14.7% ± 3.5%. The activity of AFP gene promoter was significantly suppressed by addition of 1 × 10^-7 M retinoic acid (P < 0.05, P = 0.003, t = 6.488).

CONCLUSION: This recombinant expression vector can be used as a gene therapy vector for HCC. The expression of tumor killing gene will be confined within the site of tumor and the activity of which can be regulated by retinoic acid.

Gene Therapy Applications to Cancer Treatment

Over the past ten years significant advances have been made in the fields of gene therapy and tumour immunology, such that there now exists a considerable body of evidence validating the proof in the principle of gene therapy based cancer vaccines. While clinical benefit has so far been marginal, data from preclinical and early clinical trials of gene therapy combined with standard therapies are strongly suggestive of additional benefit. Many reasons have been proposed to explain the paucity of clinical responses to single agent vaccination strategies including the poor antigenicity of tumour cells and the development of tolerance through down-regulation of MHC, costimulatory, signal transduction, and other molecules essential for the generation of strong immune responses. In addition, there is now evidence from animal models that the growing tumour may actively inhibit the host immune response. Removal of the primary tumour prior to T cell transfer from the spleen of cancer bearing animals, led to effective tumour cell line specific immunity in the recipient mouse suggesting that there is an ongoing tumour-host interaction. This model also illustrates the potential difficulties of clinical vaccine trials in patients with advanced stage disease.

Intracellular immunization by hammerhead ribozyme against HCV

AIM: To evaluate the effect of hammerhead ribozyme 213 (Rz 213) against hepatitis C virus (HCV) infection.

METHODS: Rz213 cleaving 5'oncoding region (5'CR) of HCV was beforehand transfected in a human hepatic carcinoma cell (HHCC) line and selected for G418 resistance. Cells stably expressing Rz213 were retransfected with pCMVNCRluc containing 5扤CR-luc fusion genes by lipofectAMINE; luciferase activity in lysate of transfactant was measured in scintillation counter.

RESULTS: HHCC cells stably expressing Rz213 exhibited significant resistance to retransfection of targeting gene.

CONCLUSION: Stably transfected cells with Rz213 were selected and expressed in HHCC, and thus exerted the intracellular immunity against infection of HCV.

Hepatocellular carcinoma: systemic treatments

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, with increasing incidence in Western countries. Many pharmacologic treatments have been tested against HCC; most of them belong to three categories: chemotherapy, hormone therapy, and immunotherapy. Neither single agent nor combination chemotherapy have demonstrated a clear reproducible advantage in terms of overall survival; therefore, systemic or intraarterial chemotherapy should not be considered as standard strategies for patients with HCC. Tamoxifen and antiandrogen therapy were not effective in prolonging survival when tested in randomized, controlled trials. Promising results have been obtained with octreotide in a small randomized trial, but confirmation studies are needed. Although adoptive immunotherapy was effective in the adjuvant setting, interferon should be further investigated in this setting or investigated as a preventive strategy in cirrhotic patients. On the contrary, interferon does not seem to have a role in advanced disease, where it is tolerated poorly. In the future, innovative and promising therapeutic strategies will be tested in HCC, including new biologic target-based drugs, cyclooxygenase inhibitors, and gene therapy.

Noninvasive gene delivery to the liver by mechanical massage

With the recent completion of the human genome project and the tremendous growth of biotechnology, the desire to extract information concerning gene expression, protein level, subcellular localization, and functionality in the liver will demand the development of efficient gene transfer to this organ with minimal toxicity. In this report, we show that significant gene expression in the liver could be achieved by simple mechanical massage after intravenous injection of naked plasmid DNA into mice. This method is simple, highly reproducible, repeatable, and, more importantly, free of toxicity. Hepatic gene transfer with hepatocyte growth factor (HGF) plasmid DNA prevented endotoxin-induced lethal fulminant hepatic failure, leading to dramatically enhanced survival in mice.