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

Riboswitch-controlled IL-12 gene therapy reduces hepatocellular cancer in mice

Hepatocellular carcinoma (HCC) and solid cancers with liver metastases are indications with high unmet medical need. Interleukin-12 (IL-12) is a proinflammatory cytokine with substantial anti-tumor properties, but its therapeutic potential has not been realized due to severe toxicity. Here, we show that orthotopic liver tumors in mice can be treated by targeting hepatocytes via systemic delivery of adeno-associated virus (AAV) vectors carrying the murine IL-12 gene. Controlled cytokine production was achieved in vivo by using the tetracycline-inducible K19 riboswitch. AAV-mediated expression of IL-12 led to STAT4 phosphorylation, interferon-γ (IFNγ) production, infiltration of T cells and, ultimately, tumor regression. By detailed analyses of efficacy and tolerability in healthy and tumor-bearing animals, we could define a safe and efficacious vector dose. As a potential clinical candidate, we characterized vectors carrying the human IL-12 (huIL-12) gene. In mice, bioactive human IL-12 was expressed in a vector dose-dependent manner and could be induced by tetracycline, suggesting tissue-specific AAV vectors with riboswitch-controlled expression of highly potent proinflammatory cytokines as an attractive approach for vector-based cancer immunotherapy.

Immunochemotherapy against colon cancer by gene transfer of interleukin-12 in combination with oxaliplatin

Using a murine model of liver metastases, we found that oxaliplatin can enhance the immunostimulatory effect of interleukin-12 delivered by an adenoviral vector. A shift toward a favorable immune microenvironment was observed in tumors, with a relative increase in CD8+ T cells vs. T regulatory and myeloid-derived suppressor cells.

Local administration of IL-12 with an HC vector results in local and metastatic tumor control in pediatric osteosarcoma

Osteosarcoma is the most frequent and aggressive bone tumor in children and adolescents, with a long-term survival rate of 30%. Interleukin-12 (IL-12) is a potent cytokine that bridges innate and adaptive immunity, triggers antiangiogenic responses, and achieves potent antitumor effects. In this work, we evaluated the antisarcoma effect of a high-capacity adenoviral vector encoding mouse IL-12. This vector harbored a mifepristone-inducible system for controlled expression of IL-12 (High-Capacity adenoviral vector enconding the EF1α promoter [HCA-EFZP]-IL-12). We found that local administration of the vector resulted in a reduction in the tumor burden, extended overall survival, and tumor eradication. Moreover, long-term survivors exhibited immunological memory when rechallenged with the same tumor cells. Treatment with HCA-EFZP-IL-12 also resulted in a significant decrease in lung metastasis. Immunohistochemical analyses showed profound remodeling of the osteosarcoma microenvironment with decreases in angiogenesis and macrophage and myeloid cell numbers. In summary, our data underscore the potential therapeutic value of IL-12 in the context of a drug-inducible system that allows controlled expression of this cytokine, which can trigger a potent antitumor immune response in primary and metastatic pediatric osteosarcoma.

Externally-Controlled Systems for Immunotherapy: From Bench to Bedside

Immunotherapy is a very promising therapeutic approach against cancer that is particularly effective when combined with gene therapy. Immuno-gene therapy approaches have led to the approval of four advanced therapy medicinal products (ATMPs) for the treatment of p53-deficient tumors (Gendicine and Imlygic), refractory acute lymphoblastic leukemia (Kymriah) and large B-cell lymphomas (Yescarta). In spite of these remarkable successes, immunotherapy is still associated with severe side effects for CD19+ malignancies and is inefficient for solid tumors. Controlling transgene expression through an externally administered inductor is envisioned as a potent strategy to improve safety and efficacy of immunotherapy. The aim is to develop smart immunogene therapy-based-ATMPs, which can be controlled by the addition of innocuous drugs or agents, allowing the clinicians to manage the intensity and durability of the therapy. In the present manuscript, we will review the different inducible, versatile and externally controlled gene delivery systems that have been developed and their applications to the field of immunotherapy. We will highlight the advantages and disadvantages of each system and their potential applications in clinics.

An in silico exploration of combining Interleukin-12 with Oxaliplatin to treat liver-metastatic colorectal cancer

Background

Combining anti-cancer therapies with orthogonal modes of action, such as direct cytotoxicity and immunostimulatory, hold promise for expanding clinical benefit to patients with metastatic disease. For instance, a chemotherapy agent Oxaliplatin (OXP) in combination with Interleukin-12 (IL-12) can eliminate pre-existing liver metastatic colorectal cancer and protect from relapse in a murine model. However, the underlying dynamics associated with the targeted biology and the combinatorial space consisting of possible dosage and timing of each therapy present challenges for optimizing treatment regimens. To address some of these challenges, we developed a predictive simulation platform for optimizing dose and timing of the combination therapy involving Mifepristone-induced IL-12 and chemotherapy agent OXP.

Methods

A multi-scale mathematical model comprised of impulsive ordinary differential equations was developed to describe the interaction between the immune system and tumor cells in response to the combined IL-12 and OXP therapy. An ensemble of model parameters were calibrated to published experimental data using a genetic algorithm and used to represent three different phenotypes: responders, partial-responders, and non-responders.

Results

The multi-scale model captures tumor growth patterns of the three phenotypic responses observed in mice in response to the combination therapy against a tumor re-challenge and was used to explore the impacts of changing the dose and timing of the mixed immune-chemotherapy on tumor growth subjected to a tumor re-challenge in mice. An increased ratio of CD8 + T effectors to regulatory T cells during and after treatment was key to improve tumor control in the responder cohort. Sensitivity analysis indicates that combined OXP and IL-12 therapy worked more efficiently in responders by increased priming of T cells, enhanced CD8 + T cell-mediated killing, and functional inhibition of regulatory T cells. In a virtual cohort that mimics non-responders and partial-responders, simulations show that an increased dose of OXP alone would improve the response. In addition, enhanced IL-12 expression alone or an increased number of treatment cycles of the mixed immune-chemotherapy can barely improve tumor control for non-responders and partial responders.

Conclusions

Overall, this study illustrates how mechanistic models can be used for in silico screening of the optimal therapeutic dose and timing in combined cancer treatment strategies.

In-Depth Characterization of a Mifepristone-Regulated Expression System for AAV5-Mediated Gene Therapy in the Liver

Gene therapy is being developed for the treatment of inherited diseases, whereby a therapeutic gene is continuously expressed in patients after delivery via viral vectors such as adeno-associated virus (AAV). Depending on the transgene, there could be a limited therapeutic window, and regulating timing and levels of transgene expression is advantageous. To control transgene transcription, the regulatory system GeneSwitch (GS) was evaluated in detail both in vitro and in vivo. The classical two-plasmid mifepristone (MFP)-inducible GS system was put into one plasmid or a single AAV5 vector. Our data demonstrate the inducibility of multiple transgenes and the importance of promoter and regulatory elements within the GS system. Mice injected with AAV5 containing the GS system transiently expressed mRNA and protein after MFP induction. The inducer MFP could be measured in plasma and liver tissue, and assessment of MFP and its metabolites showed rapid clearance from murine plasma. In a head-to-head comparison, our single vector outclassed the classical two-vector GS system. Finally, we show repeated inducibility of the transgene that also translated into a dynamic phenotypic change in mice. Taken together, this in-depth analysis of the GS system shows its applicability for regulated gene therapy.

Adaptation of vectors and drug-inducible systems for controlled expression of transgenes in the tumor microenvironment

Biological therapies based on recombinant proteins such as antibodies or cytokines are continuously improving the repertoire of treatments against cancer. However, safety and efficacy of this approach is often limited by inappropriate biodistribution and pharmacokinetics of the proteins when they are administered systemically. Local administration of gene therapy vectors encoding these proteins would be a feasible alternative if they could mediate long-term and controlled expression of the transgene after a single intratumoral administration. We describe a new vector platform specially designed for this purpose. Different combinations of transactivators and promoters were evaluated to obtain a fully humanized inducible system responsive to the well-characterized drug mifepristone. The optimal transactivator conformation was based on DNA binding domains from the chimeric protein ZFHD1 fused to the progesterone receptor ligand binding domain and the NFkb p65 activation domain. The expression of this hybrid transactivator under the control of the elongation factor 1α (EF1α) or the chimeric CAG promoters ensured functionality of the system in a variety of cancer types. Expression cassettes with luciferase as a reporter gene were incorporated into High-Capacity adenoviral vectors (HC-Ad) for in vivo evaluation. Systemic administration of the vectors into C57BL/6 mice revealed that the vector based on the EF1α promoter (HCA-EF-ZP) allows tight control of transgene expression and remains stable for at least two months, whereas the CAG promoter suffers a progressive inactivation. Using an orthotopic pancreatic cancer model in syngeneic C57BL/6 mice we show that the local administration of HCA-EF-ZP achieves better tumor/liver ratio of luciferase production than the intravenous route. However, regional spread of the vector led to substantial transgene expression in peritoneal organs. We reduced this leakage through genetic modification of the vector capsid to display RGD and poly-lysine motifs in the fiber knob. Safety and antitumor effect of this gene therapy platform was demonstrated using interleukin-12 as a therapeutic gene. In conclusion, we have developed a new tool that allows local, sustained and controlled production of therapeutic proteins in tumors.

Progress in surgical and nonsurgical approaches for hepatocellular carcinoma treatment

BACKGROUND

Hepatocellular carcinoma (HCC) is a complex and heterogeneous malignancy, frequently occurs in the setting of a chronically diseased organ, with multiple confounding factors making its management challenging. HCC represents one of the leading causes of cancer-related mortality globally with a rising trend of incidence in some of the developed countries, which indicates the need for better surgical and nonsurgical management strategies.

DATA SOURCES

PubMed database was searched for relevant articles in English on the issue of HCC management.

RESULTS

Surgical resection represents a potentially curative option for appropriate candidates with tumors detected at earlier stages and with well-preserved liver function. The long-term outcome of surgery is impaired by a high rate of recurrence. Surgical approaches are being challenged by local ablative therapies such as radiofrequency ablation and microwave ablation in selected patients. Liver transplantation offers potential cure for HCC and also correction of underlying liver disease, and minimizes the risk of recurrence, but is reserved for patients within a set of criteria proposed for a prudent allocation in the shortage of donor organs. Transcatheter locoregional therapies have become the palliative standard allowing local control for intermediate stage patients with noninvasive multinodular or large HCC who are beyond the potentially curative options. The significant survival benefit with the multikinase inhibitor sorafenib for advanced HCC has shifted the direction of research regarding systemic treatment toward molecular therapies targeting the disregulated pathways of hepatocarcinogenesis. Potential benefit is suggested from simultaneous or sequential multimodal therapies, and optimal combinations are being investigated. Despite the striking progress in preclinical studies of HCC immunotherapy and gene therapy, extensive clinical trials are required to achieve successful clinical applications of these innovative approaches.

CONCLUSION

Treatment decisions have become increasingly complex for HCC with the availability of multiple surgical and nonsurgical therapeutic options and require a comprehensive, multidisciplinary approach.

Gene therapy approaches against cancer using in vivo and ex vivo gene transfer of interleukin-12

IL-12 is an immunostimulatory cytokine with strong antitumor properties. Systemic administration of IL-12 in cancer patients led to severe toxic effects, prompting the development of gene therapy vectors able to express this cytokine locally in tumors. Both nonviral and viral vectors have demonstrated a high antitumor efficacy in preclinical tumor models. Some of these vectors, including DNA electroporation, adenovirus and ex vivo transduced dendritic cells, were tested in patients, showing low toxicity and moderate antitumor efficacy. IL-12 activity can be potentiated by molecules with immunostimulatory, antiangiogenic or cytotoxic activity. These combination therapies are of clinical interest because they could lower the threshold for IL-12 efficacy, increasing the therapeutic potential of gene therapy and preventing the toxicity mediated by this cytokine.

Safety and antitumor effect of oncolytic and helper-dependent adenoviruses expressing interleukin-12 variants in a hamster pancreatic cancer model

Gene transfer of potent immunostimulatory cytokines such as interleukin-12 (IL-12) is a potential treatment for advanced cancer. Different vectors and IL-12 modifications have been developed to avoid side effects associated with high serum levels of the cytokine, while preserving its antitumor properties. Here we have evaluated two alternative strategies using the Syrian hamster as a model for pancreatic cancer metastatic to the liver. Local administration of an oncolytic adenovirus (OAV) expressing a single-chain version of IL-12 caused transient, very intense elevations of IL-12 in serum, resulting in severe toxicity at sub-therapeutic doses. Anchoring IL-12 to the membrane of infected cells by fusion with the transmembrane domain of CD4 reduced systemic exposure to IL-12 and increased the tolerance to the OAV. However, only a modest increase in the therapeutic range was achieved because antitumor potency was also reduced. In contrast, systemic administration of a helper-dependent adenoviral vector (HDAd) equipped with a Mifepristone-inducible expression system allowed sustained and controlled IL-12 production from the liver. This treatment was well tolerated and inhibited the progression of hepatic metastases. We conclude that HDAds are safer than OAVs for the delivery of IL-12, and are promising vectors for immunogene therapy approaches against pancreatic cancer.

A novel approach for addressing diseases not yielding to effective vaccination? Immunization by replication-competent controlled virus

Vaccination involves inoculation of a subject with a disabled disease-causing microbe or parts thereof. While vaccination has been highly successful, we still lack sufficiently effective vaccines for important infectious diseases. We propose that a more complete immune response than that elicited from a vaccine may be obtained from immunization with a disease-causing virus modified to subject replication-essential genes to the control of a gene switch activated by non-lethal heat in the presence of a drug-like compound. Upon inoculation, strictly localized replication of the virus would be triggered by a heat dose administered to the inoculation site. Activated virus would transiently replicate with an efficiency approaching that of the disease-causing virus and express all viral antigens. It may also vector heterologous antigens or control co-infecting microbes.

Short-term intratumoral interleukin-12 expressed from an alphaviral vector is sufficient to induce an efficient antitumoral response against spontaneous hepatocellular carcinomas

Interleukin-12 (IL-12) is an immunostimulatory cytokine that has shown strong antitumor effects in animal models of liver cancer. In order to overcome the severe toxicity associated with its systemic administration, we had previously tested different strategies based on IL-12 gene transfer to tumor cells or to the surrounding liver tissue. We obtained promising results both with a recombinant Semliki Forest virus (SFV) vector expressing high levels of IL-12 (SFV-IL-12) after intratumoral injection and with a plasmid vector [pTonL2(T)-mIL12] that allows liver-specific and inducible IL-12 expression. The aim of the present study was to compare the antitumor responses induced by both systems in a clinically relevant animal model of hepatocellular carcinoma (HCC) developed in L-PK/c-myc transgenic mice. These animals overexpress the c-myc oncogene in their livers, giving rise to spontaneous hepatic tumors with latency, histopathology, and genetic characteristics similar to human HCCs. We observed that intratumoral inoculation of SFV-IL-12 induced growth arrest in most tumors, providing 100% survival rate, in contrast to no survival in control animals. Similar results were obtained with hydrodynamic injection of pTonL2(T)-mIL12 after long-term induction of IL-12 expression in the liver. However, tumor arrest was less evident in plasmid-treated mice and the survival rate was slightly lower, despite higher and more sustained levels of IL-12 and IFN-γ in serum. The fact that SFV-IL-12 was able to induce both apoptosis and a type-I IFN response specifically in the tumor could explain why short-term IL-12 expression from this vector was sufficient to mediate an antitumoral response comparable with long-term IL-12 expression driven by pTonL2(T)-mIL12. Since SFV-IL-12 could reduce the possible toxicity associated with long-term IL-12 expression, we believe that this vector could have a potential application for HCC gene therapy.

Target-mediated disposition model describing the dynamics of IL12 and IFNγ after administration of a mifepristone-inducible adenoviral vector for IL-12 expression in mice

Interleukin-12 (IL12) is a cytokine with potential applications in the treatment of cancer given the potent immune response that it triggers, in part due to its ability to stimulate expression of interferon-γ (IFNγ). To avoid the toxicity associated with systemic exposure to IL12, a high-capacity adenoviral vector carrying a liver-specific, mifepristone-inducible IL12 expression system (HC-Ad/RUmIL12) has been developed. However, the maintenance of IL12 expression at therapeutic levels is compromised by the inhibitory effect of IFNγ on inducible systems. The aim of this work is to develop a semi-mechanistic model to characterize the relationship between IL12 and IFNγ in wild-type and knock-out mice for the IFNγ receptor treated with HC-Ad/RUmIL12 under different dosing regimens in order to better understand the key mechanisms controlling the system. Rapid binding was considered to account for target-mediated disposition exhibited by both cytokines (equilibrium dissociation constant were 18 and 2.28 pM for IL12 and IFNγ, respectively). The final model included: (1) IFNγ receptor turnover, (2) irreversible free cytokine elimination from the serum compartment, (3) internalization of the IL12 receptor complex, (4) IL12 expression upregulated by the co-administration of the adenoviral vector and mifepristone and downregulated by the IFNγ receptor, and (5) synthesis of IFNγ controlled by the relative increments in the bound IL12. In conclusion, a model simultaneously describing the kinetics of IL12 and IFNγ in the context of gene therapy was developed and validated with additional data. The model was applied to design an experimental dosing protocol intended to maintain sustained therapeutic IL12 levels.

Induction of interleukin 2 expression in the liver for the treatment of H22 hepatoma in mice

BACKGROUND AND AIMS

We designed this study to evaluate the ability of a plasmid carrying an RU486 regulatory system to induce expression of interleukin-2 (IL-2) gene and to examine the antitumour efficacy of the induced IL-2 gene.

METHODS

The plasmid pRS-mIL-2,which contains an RU486 inducible system and IL-2 gene was injected into mice. Sera and tissues from liver, spleen, lungs and kidneys were taken to test the properties of the plasmid. To examine the antitumour efficacy of pRS-mIL-2, tumours were established in the liver by direct inoculation of H22 hepatoma cells.

RESULTS

The IL-2 levels in serum correlated with the dose of plasmid and RU486. High and sustained IL-2 levels could be achieved by administration of RU486 every day. The mRNA of transgene IL-2 was found only in the liver. Treatment of mice with pRS-mIL-2 plus RU486 resulted in the significant reduction in tumour volume compared with control groups.

CONCLUSIONS

Tight temporal and spatial control of transgene IL-2 expression can be achieved by a plasmid containing an RU486 inducible system driven by liver specific promoter. pRS-mIL-2 exhibited strong antitumour efficacy following consecutive induction with RU486.

Modulation of regulatory T-cell activity in combination with interleukin-12 increases hepatic tolerogenicity in woodchucks with chronic hepatitis B

Regulatory T cells (Treg) play a critical role in the modulation of immune responses to viral antigens in chronic viral hepatitis. Woodchucks (Marmota monax) infected with the woodchuck hepatitis virus (WHV) represent the best animal model for chronic hepatitis B virus (HBV) infection. Examination of intrahepatic and peripheral Treg in uninfected and WHV chronically infected woodchucks showed a significant increase of intrahepatic Treg numbers in chronically infected animals, whereas no differences were found in peripheral blood. In agreement with these data, higher expression levels of Forkhead box P3 (Foxp3), interleukin (IL)-10, transforming growth factor beta (TGF-β) were detected in the liver of chronic WHV carriers in comparison to uninfected animals. Furthermore, treatment of WHV-infected animals with an adenovirus encoding IL-12 failed to reduce viral load, a finding that was associated with lymphocyte unresponsiveness to IL-12 stimulation in vitro. We observed that TGF-β and Treg play a major role in the lack of lymphocyte response to IL-12 stimulation, as TGF-β inhibition and Treg depletion allowed recovery of T-cell responsiveness to this cytokine. Based on these results, woodchucks were treated with IL-12 in combination with a TGF-β inhibitory peptide or Treg depletion. However, no antiviral effect was achieved and, instead, an enhancement of the intrahepatic tolerogenic environment was observed.

CONCLUSION

Our data show that TGF-β inhibition or Treg depletion had no added benefit over IL-12 therapy in chronic WHV infection. IL-12 immunostimulation induces a strong immunosuppressive reaction in the liver of chronic WHV carriers that counteracts the antiviral effect of the treatment.

Recombinant adenovirus Ad-RUNrf2 reduces paraquat-induced A549 injury

OBJECTIVE

An RU486-inducible recombinant adenovirus-Nrf2 construct (Ad-RUNrf2) was constructed and expressed in H460 cells to determine whether Nrf2 gene expression can be regulated and to observe the effect of the adenovirus Ad-RUNrf2 on inflammatory cytokines, oxidative stress and apoptotic factors that mediate paraquat (PQ)-induced A549 cell injury.

METHODS

The Nrf2 gene within the RU486 (mifepristone)-inducible system was introduced into an adenovirus vector. A549 cells were transfected with Ad-RUNrf2, and Nrf2 expression was detected using Western blotting and real time-polymerase chain reaction (RT-PCR). RT-PCR, Western blots and enzyme-linked immunosorbent assay were used for observing the effect of RU486-induced Nrf2 expression on the inflammatory cytokines (interleukin-6 (IL-6), IL-10 and tumor necrosis factor-α (TNF-α)), oxidative stress factors (catalase (CAT) and malondialdehyde (MDA)) and apoptosis factors (caspase-3, caspase-9 and cytochrome C) that mediated PQ-induced A549 cell injury.

RESULTS

After infection of H460 cells by Ad-RUNrf2, RT-PCR and Western blot analyses showed that Nrf2 expression increased with additional RU486 doses. IL-6 and TNF-α protein and gene expression levels were significantly reduced, and IL-10 protein levels were significantly increased. Although IL-10 expression increased, it remained significantly lower than that of noninduced adenovirus infection and the simple virus exposure group. RU486 induced a significant reduction in MDA expression and increased CAT protein levels. Caspase-9 and caspase-3 protein and gene expression levels decreased in the RU486 induction group (p < 0.05). Cytochrome C protein levels were not significantly reduced, but its gene expression was significantly decreased (p < 0.05).

CONCLUSION

Ad-RUNrf2 adenovirus was successfully constructed and can be stably expressed and regulated in cells. Ad-RUNrf2 can reduce PQ-induced inflammation, oxidative stress and apoptosis in A549 cells.

Long-term culture and cryopreservation of interstitial cells of Cajal

OBJECTIVE

Interstitial cells of Cajal (ICCs) in the gastrointestinal tract generate and propagate slow waves and mediate neuromuscular neurotransmission. Damage to ICCs has been described in several gastrointestinal motor disorders, and although many studies have examined ICCs in culture, they have been largely limited to freshly dissociated cells or short-term cultures. An efficient and reliable method to establish a source of ICCs is much needed. The aim of this study was to investigate methods for culturing, subculturing, cryopreservation, and recovery of ICCs.

METHODS

ICCs were derived from intestinal segments of domestic rabbits, and immunohistochemistry for c-Kit was used to identify ICCs in culture and after recovery. Recovered ICCs were also examined for motilin receptor expression.

RESULTS

Optimal conditions for ICC culture and cryopreservation were based on cell growth curves and MTT assay. On the basis of these findings, recovered cells were cultured for 7 days and then sorted via flow cytometry based on c-Kit immunoreactivity. The percent of c-Kit positive cells was 64.3%, and the number of ICCs sorted was 6.7 × 10(5). Reverse-transcription polymerase chain reaction and western blotting verified motilin receptor expression in c-Kit-positive ICCs.

CONCLUSIONS

This is the first study to describe the culture, passage, and recovery of ICCs and to show motilin receptor expression. Our results suggest that ICCs play an important role, at least in some species, in initiating the migrating myoelectric complex induced by motilin.

Gene therapy of liver diseases: a 2011 perspective

Liver diseases including inherited metabolic disorders, chronic viral hepatitis, liver cirrhosis and primary and metastatic liver cancer constitute a formidable health problem because of their high prevalence and the important limitations of current therapies. Gene therapy, a procedure based on the transfer of therapeutic genes to tissues, has been used since the 1990s as a new approach to treating a number of incurable conditions. After a period of lights and shades recent success in treating several devastating diseases like inherited immune deficiency disorders, beta-thalassemia, or inherited blindness appear to herald a new era where gene therapy can be listed among standard therapy options for a wide variety of human conditions. In this review, we provide information illustrating the potentiality of gene therapy in the management of liver diseases lacking other effective therapies.

Self-inactivating helper virus for the production of high-capacity adenoviral vectors

Standard methods for producing high-capacity adenoviral vectors (HC-Ads) are based on co-infection with a helper adenovirus (HV). To avoid HV encapsidation, its packaging signal (Ψ) is flanked by recognition sequences for recombinases expressed in the producing cells. However, accumulation of HV and low yield of HC-Ad are frequently observed, due in part to insufficient recombinase expression. We describe here a novel HV (AdTetCre) in which Ψ is flanked by loxP sites that can be excised by a chimeric MerCreMer recombinase encoded in the same viral genome. Efficient modulation of cleavage was obtained by simultaneous control of MerCreMer expression using a tet-on inducible system, and translocation to the nucleus by 4-hydroxytamoxifen (TAM). Encapsidation of AdTetCre was strongly inhibited by TAM plus doxycicline. Using AdTetCre and 293Cre4 cells for the production of HC-Ads, we found that cellular and virus-encoded recombinases cooperate to minimize HV contamination. The method was highly reproducible and allowed the routine production of different HC-Ads in a medium-scale laboratory setting in adherent cells, with titers >10¹⁰ infectious units and <0.1% HV contamination. The residual HVs lacked Ψ and were highly attenuated. We conclude that self-inactivating HVs based on virally encoded recombinases are promising tools for the production of HC-Ads.

Development of a liver-specific Tet-on inducible system for AAV vectors and its application in the treatment of liver cancer

Recombinant adeno-associated virus (rAAV) are effective gene delivery vehicles that can mediate long-lasting transgene expression. However, tight regulation and tissue-specific transgene expression is required for certain therapeutic applications. For regulatable expression from the liver we designed a hepatospecific bidirectional and autoregulatory tetracycline (Tet)-On system (Tet(bidir)Alb) flanked by AAV inverted terminal repeats (ITRs). We characterized the inducible hepatospecific system in comparison with an inducible ubiquitous expression system (Tet(bidir)CMV) using luciferase (luc). Although the ubiquitous system led to luc expression throughout the mouse, luc expression derived from the hepatospecific system was restricted to the liver. Interestingly, the induction rate of the Tet(bidir)Alb was significantly higher than that of Tet(bidir)CMV, whereas leakage of Tet(bidir)Alb was significantly lower. To evaluate the therapeutic potential of this vector, an AAV-Tet(bidir)-Alb-expressing interleukin-12 (IL-12) was tested in a murine model for hepatic colorectal metastasis. The vector induced dose-dependent levels of IL-12 and interferon-γ (IFN-γ), showing no significant toxicity. AAV-Tet(bidir)-Alb-IL-12 was highly efficient in preventing establishment of metastasis in the liver and induced an efficient T-cell memory response to tumor cells. Thus, we have demonstrated persistent, and inducible in vivo expression of a gene from a liver-specific Tet-On inducible construct delivered via an AAV vector and proved to be an efficient tool for treating liver cancer.

Generation of full-length functional antibody against preS2 of hepatitis B virus in hepatic cells in vitro from bicistrons mediated by gutless adenovirus

BACKGROUND

Monoclonal antibodies (mAbs) have been developed as effective therapeutics for a wide variety of diseases. Delivery of mAbs by gene transfer provides an option for overcoming the difficulties in mAb production and manufacturing processes. However, for the polymeric structure of full-length mAbs, it is important to design an optimal gene transfer system for mAb generation.

METHODS

Gutless adenovirus and liver-specific promoter transthyretin (TTR) were combined to deliver bicistronic mAb genes in human hepatic cell lines. In order to optimize the bicistrons for mAb generation, four bicistrons were designed and compared, and the most efficient one was selected. ELISA and Western blot were conducted to evaluate mAb products in the supernatants.

RESULTS

Our data showed that all of four gutless adenoviruses elicited liver-specific mAb production in HepG2 and Hep3B hepatic cell lines. It was observed that the L2AH bicistron construct (comprising an immunoglobulin light-chain cDNA situated 5' of a heavy-chain cDNA, with a foot-and-mouth disease virus 2A cleavage site in the middle, subcloned into the helper-dependent adenovirus plasmid pGL) could induce the highest level expression of mAb (about 5.0 microg/mL in Hep3B) among these four constructs. Importantly, the mAb products by gene transfer methods retained specific antigen-binding activity.

CONCLUSION

Our studies gave further evidence that it was feasible to produce active full-length mAb in human hepatic cell lines in vitro by a special gene delivery system. Moreover, we developed an optimized bicistron gene transfer system for future gene therapy research, which may also be of use in industrial mAb production.

Construction and application of an inducible system for homogenous expression levels in bulk cell lines

Stringently controlled conditional expressing systems are crucial for the functional characterization of genes. Currently, screening of multiple clones to identify the tightly controlled ones is necessary but time-consuming. Here, we describe a system fusing Tet (tetracycline)-inducible elements, BAC (bacterial artificial chromosome) and Gateway technology together to allow tight control of gene expression in BAC-transfected eukaryotic bulk cell cultures. Recombinase cloning into the shuttle vector and the BAC facilitates vector construction. An EGFP (enhanced green fluorescent protein) allows FACS (fluorescence activated cell sorting) and the BAC technology ensures tight control of gene expression that is independent of the integrating site. In the current first application, our gene of interest encodes a beta-catenin-ERalpha fusion protein. Tested by luciferase assay and western blotting, in HTB56 lung cancer cells the final BAC E11-IGR-beta-catenin-ERalpha vector demonstrated sensitive inducibility by Tet or Dox (doxycycline) in a dose-dependent manner with low background, and the EGFP was an effective selection marker by FACS in bulk culture HTB56 and myeloblastic 32D cells. This is a highly efficient tool for the rapid generation of stringently controlled Tet-inducible systems in cell lines.

Evaluation of bioluminescent imaging for noninvasive monitoring of colorectal cancer progression in the liver and its response to immunogene therapy

Background

Bioluminescent imaging (BLI) is based on the detection of light emitted by living cells expressing a luciferase gene. Stable transfection of luciferase in cancer cells and their inoculation into permissive animals allows the noninvasive monitorization of tumor progression inside internal organs. We have applied this technology for the development of a murine model of colorectal cancer involving the liver, with the aim of improving the pre-clinical evaluation of new anticancer therapies.

Results

A murine colon cancer cell line stably transfected with the luciferase gene (MC38Luc1) retains tumorigenicity in immunocompetent C57BL/6 animals. Intrahepatic inoculation of MC38Luc1 causes progressive liver infiltration that can be monitored by BLI. Compared with ultrasonography (US), BLI is more sensitive, but accurate estimation of tumor mass is impaired in advanced stages. We applied BLI to evaluate the efficacy of an immunogene therapy approach based on the liver-specific expression of the proinflammatory cytokine interleukin-12 (IL-12). Individualized quantification of light emission was able to determine the extent and duration of antitumor responses and to predict long-term disease-free survival.

Conclusion

We show that BLI is a rapid, convenient and safe technique for the individual monitorization of tumor progression in the liver. Evaluation of experimental treatments with complex mechanisms of action such as immunotherapy is possible using this technology.

Treatment of chronic viral hepatitis in woodchucks by prolonged intrahepatic expression of interleukin-12

Chronic hepatitis B is a major cause of liver-related death worldwide. Interleukin-12 (IL-12) induction accompanies viral clearance in chronic hepatitis B virus infection. Here, we tested the therapeutic potential of IL-12 gene therapy in woodchucks chronically infected with woodchuck hepatitis virus (WHV), an infection that closely resembles chronic hepatitis B. The woodchucks were treated by intrahepatic injection of a helper-dependent adenoviral vector encoding IL-12 under the control of a liver-specific RU486-responsive promoter. All woodchucks with viral loads below 10(10) viral genomes (vg)/ml showed a marked and sustained reduction of viremia that was accompanied by a reduction in hepatic WHV DNA, a loss of e antigen and surface antigen, and improved liver histology. In contrast, none of the woodchucks with higher viremia levels responded to therapy. The antiviral effect was associated with the induction of T-cell immunity against viral antigens and a reduction of hepatic expression of Foxp3 in the responsive animals. Studies were performed in vitro to elucidate the resistance to therapy in highly viremic woodchucks. These studies showed that lymphocytes from healthy woodchucks or from animals with low viremia levels produced gamma interferon (IFN-gamma) upon IL-12 stimulation, while lymphocytes from woodchucks with high viremia failed to upregulate IFN-gamma in response to IL-12. In conclusion, IL-12-based gene therapy is an efficient approach to treat chronic hepadnavirus infection in woodchucks with viral loads below 10(10) vg/ml. Interestingly, this therapy is able to break immunological tolerance to viral antigens in chronic WHV carriers.

Lethality in an anti-angiogenic tumor gene therapy model upon constitutive but not inducible expression of the soluble vascular endothelial growth factor receptor 1

BACKGROUND

Neoangiogenesis is essential for tumor growth. The present study aimed to test the hypothesis that vector-mediated expression of sflt1 at high levels would result in the blockade of vascular endothelial growth factor (VEGF) function and therefore the inhibition of tumor growth.

METHODS

To sequester VEGF, we tested, in a subcutaneous LLC tumor model, 'gutless' high-capacity adenovirus vectors expressing the soluble VEGF receptor 1 (sflt1) in a liver-specific manner, either in a constitutive or in a RU486 induced manner.

RESULTS

High serum levels of sflt1 were observed upon in vivo injection of both vectors. Despite the differences in expression kinetics, both modes of sflt1 expression resulted in significant though transient suppression of tumor growth. Unexpectedly, constitutive but not intermittent sflt1 expression resulted in ascites and death of all animals. Morphological analyses by light and electron microscopy indicated that the animals had died from a nephropathy, which apparently was due to the blockade of VEGF function.

CONCLUSIONS

Although confirming earlier results of toxic effects of prolonged VEGF sequestration, the present study suggests that therapeutic anti-tumor effects can be achieved without side-effects with intermittent VEGF blockade or the use of drugs with short half-lives, as shown by the use of an inducible gene expression system.

Gene therapy: Regulations, ethics and its practicalities in liver disease

Gene therapy is a new and promising approach which opens a new door to the treatment of human diseases. By direct transfer of genetic materials to the target cells, it could exert functions on the level of genes and molecules. It is hoped to be widely used in the treatment of liver disease, especially hepatic tumors by using different vectors encoding the aim gene for anti-tumor activity by activating primary and adaptive immunity, inhibiting oncogene and angiogenesis. Despite the huge curative potential shown in animal models and some pilot clinical trials, gene therapy has been under fierce discussion since its birth in academia and the public domain because of its unexpected side effects and ethical problems. There are other challenges arising from the technique itself like vector design, administration route test and standard protocol exploration. How well we respond will decide the fate of gene therapy clinical medical practice.

Interleukin-15 liver gene transfer increases the number and function of IKDCs and NK cells

The surface phenotype CD3-NK1.1+DX5+CD11c(int)B220+GR1- has been recently ascribed to a novel subset of mouse leukocytes termed interferon (IFN)-producing killer dendritic cells (IKDCs) that shares functions with natural killer (NK) cells and DCs. Interleukin-15 (IL-15) is critical for NK cells but its relationship with IKDC remained unexplored. An expression cassette encoding human IL-15 (hIL-15) has been transferred by hydrodynamic injection into the liver of mice, resulting in transient expression of the cytokine that is detectable during the first 48 h. hIL-15 hydrodynamic gene transfer resulted in an expansion of NK cells and IKDCs. Relative expansions of IKDCs were more dramatic in the IL-15 gene-transferred hepatic tissue than in the spleen. Adoptively transferred DX5+ cells comprising both NK cells and IKDCs proliferated in response to hydrodynamic injection of hIL-15, indicating that quantitative increases are at least in part the result of proliferation from already differentiated cells. Expansion is accompanied by enhanced cytolytic activity and increased expression of TRAIL and CD137 (4-1BB), without augmenting interferon-gamma production. The effects of a single hydrodynamic injection surpassed those of two intraperitoneal doses of the recombinant protein. The novel functional link between circulating IL-15 and IKDCs opens new possibilities to study the biology and applications of this minority cell subset.

Induction of immunosuppressive molecules and regulatory T cells counteracts the antitumor effect of interleukin-12-based gene therapy in a transgenic mouse model of liver cancer

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) often lacks curative treatment; therefore new efficient therapies are needed. In this work we aimed at evaluating the antitumor effect of interleukin-12 (IL-12)-based gene therapy on HCC occurring spontaneously in mice.

METHODS

A plasmid-vector expressing IL-12 in a liver-specific and doxycycline (Dox)-inducible manner was transferred by hydrodynamic injection to the liver of L-PK/c-myc mice with HCC. IL-12 expression was induced by administering Dox (3 cycles of 1 month duration separated by 1 month rest).

RESULTS

Dox administration increased serum IL-12 and IFN-gamma and induced tumor lymphocytic infiltration in all treated mice which was accompanied by tumor stabilization or regression in 40% of animals. The antitumor effect did not correlate with levels of IL-12 or IFN-gamma nor with the intensity of tumor mononuclear infiltration. However, tumors from non-responder mice showed more abundance of Foxp3+ regulatory T cells and higher expression of the immunosuppressive molecules PD-1, PD-L1, VEGF, CTLA-4, IDO, and IL-10 than those that responded to therapy.

CONCLUSIONS

Although long-term induction of IL-12 expression in the liver can inhibit HCC growth, the efficacy of the treatment appears to be limited by the activation of immunosuppressive mechanisms.

Interleukin-12 inhibits liver-specific drug-inducible systems in vivo

Drug-inducible systems allow modulation of the duration and intensity of cytokine expression in liver immuno-based gene therapy protocols. However, the biological activity of the transgene may influence their function. We have analyzed the kinetics of interleukin-12 (IL-12) expression controlled by the doxycycline (Dox)- and the mifepristone (Mif)-dependent systems using two long-term expressing vectors directed to liver: a plasmid administered by hydrodynamic injection and a high-capacity adenoviral vector. Daily administration of Dox or Mif was associated with a progressive loss of inducibility and a decrease of murine IL-12 production. This inhibition occurred at the transcriptional level and was probably caused by an interferon (IFN)-gamma-mediated downmodulation of liver-specific promoters that control the expression of transactivators in these systems. Genome-wide expression microarrays studies revealed a parallel downregulation of liver-specific genes in mice overexpressing murine IL-12. However, a promoter naturally induced by IL-12 was also inhibited by this cytokine when placed in a plasmid vector. Interestingly, treatment with sodium butyrate, a class I/II histone deacetylase inhibitor, was able to rescue liver-specific promoter activity solely in the vector. We conclude that biologically active IL-12 can transiently inhibit the function of drug-inducible systems in non-integrative DNA vectors by reducing promoter activity, probably through IFN-gamma and protein deacetylation-dependent mechanisms.

Application of doxorubicin-induced rAAV2-p53 gene delivery in combined chemotherapy and gene therapy for hepatocellular carcinoma

p53 gene transfer has been proposed as a potential therapeutic option for treatment of hepatocellular carcinoma (HCC). Compared to other commonly used gene transfer vectors such as adenovirus and retrovirus, recombinant adeno-associated virus serotype 2 (rAAV2) has shown promising results in human clinical trials. Significant enhancement in the gene transfer efficiency is needed, however, for HCC applications. In the present study, we applied chemotherapy drug Doxorubicin (DOX) to induce rAAV2 transduction of hepatomas. Using reporter assays, we showed that the DOX-treated hepatomas became more susceptible to rAAV2 infection in comparison to untreated controls: the permissiveness increased >350-fold and >120-fold for HepG2 (p53 wild-type) and Hep3B (p53 null) hepatomas, respectively. Using the induced permissiveness, we applied rAAV2-p53 transduction to restore p53 expression in the p53-null Hep3B hepatomas. Compared to rAAV2-p53 transduction alone, rAAV2-p53 transduction with DOX resulted in a >16-fold induction of p53 expression. The transduced Hep3B expressed as much as 380% more immunoreactive p53 in comparison to the wild-type p53 expression in the HepG2 hepatomas. Significantly, when Hep3B cells were treated with 0.5 muM of DOX and rAAV2-p53 (MOI = 10) for twelve hours, the cell viability dropped to 66% four days after the administration. This decrease in cell viability was similar to that of treatment with 1 microM of DOX alone in the absence of rAAV2. The 50% reduction in DOX administration--from 1 microM to 0.5 microM--revealed the antitumor property of the rAAV2-p53 transduction as well as the joint cytotoxicity of DOX and rAAV2-p53 against the p53-null hepatomas. We conclude that DOX mediates the enhancement effect on rAAV2 transduction of human hepatomas. Combined DOX and rAAV2-p53 administration may facilitate more efficient treatment for the HCC caused by p53 mutations.

Long-Term toxicity studies in Canine of E10A, an adenoviral vector for human endostatin gene

E10A, a recombinant adenovirus type 5 vector carrying the human endostatin gene, may be a promising gene therapy drug in the treatment of solid tumors by antiangiogenesis, but a preclinical safety evaluation of E10A has not yet been performed. With high and low doses equivalent to 30 and 7.5 times the human curative dose, respectively, intramuscular injections of E10A were given once daily, 6 days/week, for 3 months, followed by a 1-month recovery period. As of 4 months, all experimental animals appeared generally healthy: normal behavior and eating habits, no nausea, vomiting, or salivation, no abnormal changes in urination or defecation, and increased body weight with the time of experiment. Urinalysis, hemogram, blood biochemistry, electrocardiogram, macroscopic and microscopic studies of organs and tissues were done before treatment, at month 3 of treatment, and 1 month posttreatment. At all time points, no significant abnormal toxic effects were noted. Preliminary investigation of E10A immunotoxicity in dogs indicated that anti-adenoviral antibodies were generated, in a dose- and time-independent manner, after E10A injection. Our data demonstrated that, long term, high-dose intramuscular administration of recombinant human endostatin-carrying adenovirus (E10A) was not notably toxic and might be safe for clinical therapeutic use, although additional long-term toxicity studies by other administration routes are still necessary.

Engineering targeted viral vectors for gene therapy

Translating knowledge of genetic disease mechanisms into gene therapies has been slow with limited clinical success. One major reason is that the transfer vectors, which are most often of viral origin, are not targeted sufficiently towards the cells of interest.

To achieve successful delivery of genetic material, transductional targeting is often essential to enter the target cell and to avoid side effects from the transduction of non-target cells.

Many techniques to target viral vectors to specific cells have been developed. They can be divided into three types: systems that use adaptor proteins from other viruses (pseudotyping); systems that use adaptors to couple the targeting ligand to the vector; and systems that genetically incorporate the targeting moiety into the viral genome.

Whereas systems involving adaptor proteins are highly useful in preclinical evaluations, systems that make use of genetically incorporated targeting ligands are advantageous for clinical applications.

Combinations of several targeting principles (including ablation of natural tropism, pseudotyping and adaptors) and novel combinations (such as the adeno-associated virus (AAV) genome in a phage vector) allow systemic vector application.

An initial clinical study with a targeted retrovirus showed feasibility to transfer laboratory success to patient application, underlining that there are no principal regulatory barriers for targeted vectors.

Systemic vector applications will be facilitated by enabling the vector to move beyond the vascular endothelium at specific sites, using transcytosis or cellular vehicles. The application of existing targeting techniques to new viral vector serotypes and new vector classes is extending the therapeutic capabilities further.

Obstacles to systemic application of vectors are found in the blood as immune reactions against the vector and as binding of blood proteins to the vector. Some targeting approaches might have the potential to circumvent these obstacles.

To preclinically evaluate new targeting strategies, several models that reflect the human situation to varying degrees are available. The use of primary cells, tissue-slice systems and transgenic animals seems to be especially promising.

Imaging technologies provide the ability to monitor the vector in vivo in real time without sacrificing the animal model. These techniques facilitate vector targeting and biodistribution studies.

A key challenge in gene therapy is vector targeting to specific cells, while avoiding effects on other tissues. Several strategies have been developed recently to enable targeting of the main viral vectors, moving them a step closer to clinical use.

To achieve therapeutic success, transfer vehicles for gene therapy must be capable of transducing target cells while avoiding impact on non-target cells. Despite the high transduction efficiency of viral vectors, their tropism frequently does not match the therapeutic need. In the past, this lack of appropriate targeting allowed only partial exploitation of the great potential of gene therapy. Substantial progress in modifying viral vectors using diverse techniques now allows targeting to many cell types in vitro. Although important challenges remain for in vivo applications, the first clinical trials with targeted vectors have already begun to take place.

Genetics in liver diseases

In recent years, few fields in medicine have witnessed discoveries as momentous as those pertaining to the liver. Dramatic advances have been made, particularly in the areas of molecular biology and genetics. A joint EASL/AASLD Monothematic Conference was held on June 23rd-24th, 2006, in Modena, Italy, to bring the latest breakthroughs in different fields of genetics to hepatologists. This article reports the highlights of the conference and summarizes the main conclusions and implications for clinical and experimental hepatology.

Regulatable gutless adenovirus vectors sustain inducible transgene expression in the brain in the presence of an immune response against adenoviruses

In view of recent serious adverse events and advances in gene therapy technologies, the use of regulatable expression systems is becoming recognized as indispensable adjuncts to successful clinical gene therapy. In the present work we optimized high-capacity adenoviral (HC-Ad) vectors encoding the novel tetracycline-dependent (TetOn)-regulatory elements for efficient and regulatable gene expression in the rat brain in vivo. We constructed two HC-Ad vectors encoding beta-galactosidase (beta-gal) driven by a TetOn system containing the rtTAS(s)M2 transactivator and the tTS(Kid) repressor under the control of the murine cytomegalovirus (mCMV) (HC-Ad-mTetON-beta-Gal) or the human CMV (hCMV) promoter (HC-Ad-hTetON-beta-Gal). Expression was tightly regulatable by doxycycline (Dox), reaching maximum expression in vivo at 6 days and returning to basal levels at 10 days following the addition or removal of Dox, respectively. Both vectors achieved higher transgene expression levels compared to the expression from vectors encoding the constitutive mCMV or hCMV promoter. HC-Ad-mTetON-beta-Gal yielded the highest transgene expression levels and expressed in both neurons and astrocytes. Antivector immune responses continue to limit the clinical use of vectors. We thus tested the inducibility and longevity of HC-Ad-mediated transgene expression in the brain of rats immunized against adenovirus by prior intradermal injections of RAds. Regulated transgene expression from HC-Ad-mTetON-beta-Gal remained active even in the presence of a significant systemic immune response. Therefore, these vectors display two coveted characteristics of clinically useful vectors, namely their regulation and effectiveness even in the presence of prior immunization against adenovirus.

Suppression of colorectal tumor growth by regulated survivin targeting

A major goal in cancer gene therapy is to develop efficient gene transfer protocols that allow tissue-specific and tightly regulated expression of therapeutic genes. The ideal vector should efficiently transduce cancer cells with minimal toxicity on normal tissues and persistently express foreign genes. One of the most promising regulatory systems is the mifepristone/RU486-regulated system, which has much lower basal transcriptional activity and high inducibility. In this work, we modified this system by incorporating a cancer-specific promoter, the human telomerase reverse transcriptase (hTERT) promoter. By utilizing hTERT promoter to control the regulator, RU486 could specifically induce the expression of foreign genes in cancer cells but not in normal cells. In the context of this system, a dominant negative mutant of survivin (surDN) was controllably expressed in colorectal tumor cells. The surDN expression induced by RU486 showed a dosage- and time-dependent pattern. Regulated expression of surDN caused caspase-dependent apoptosis in colorectal tumor cells but had little effect on normal cells. Analysis of cell viability showed that RU486-induced expression of surDN suppressed colorectal tumor cell growth and had synergic effect in combination with chemotherapeutic agents. The potential of this system in cancer therapy was evaluated in experimental animals. Tumor xenograft models were established in nude mice with colorectal tumor cells, and RU486 was intraperitoneally administered. The results showed that conditional expression of surDN efficiently inhibited tumor growth in vivo and prolonged the life of tumor-burdened mice. Synergized with the chemotherapeutic drug cisplatin, regulated surDN expression completely suppressed tumor growth. These results indicated that this modified RU486-regulated system could be useful in cancer-targeting therapy.

Gene therapy of liver cancer

The application of gene transfer technologies to the treatment of cancer has led to the development of new experimental approaches like gene directed enzyme/pro-drug therapy (GDEPT), inhibition of oncogenes and restoration of tumor-suppressor genes. In addition, gene therapy has a big impact on other fields like cancer immunotherapy, anti-angiogenic therapy and virotherapy. These strategies are being evaluated for the treatment of primary and metastatic liver cancer and some of them have reached clinical phases. We present a review on the basis and the actual status of gene therapy approaches applied to liver cancer.

Potent antitumor efficacy of XAF1 delivered by conditionally replicative adenovirus vector via caspase-independent apoptosis

XAF1 is a newly identified tumor-suppressor gene that can antagonize XIAP and sensitize cells to other cell death triggers. In this study, we utilized ZD55, a conditionally replicative adenovirus (CRAd) similar to ONYX-015 as the vector to transfer XAF1 into the tumor cells to evaluate its antitumor efficacy in vitro and in vivo. Potent and specific cytopathic effect (CPE) was observed upon infection with ZD55-XAF1 in tumor cell lines. Importantly, ZD55-XAF1 exhibited a superior suppression of tumor growth in an animal model of colorectal carcinoma in nude mice compared with Ad-XAF1 (E1-deleted replication-defective viral) and ONYX-015. Complete eradication of the established tumors was observed in four of eight mice. Our data also showed that infection with ZD55-XAF1 resulted in caspase-independent apoptosis. Although caspase-3, poly(ADP-ribose) polymerase were mildly activated in response to ZD55-XAF1 infection, pretreatment with pan-caspase inhibitor hardly influence its apoptosis-inducing activity. In summary, our study strongly suggested that ZD55-XAF1 could serve as an effective gene-virotherapy strategy and has highly potential against human cancers.

Intrahepatic injection of adenovirus reduces inflammation and increases gene transfer and therapeutic effect in mice

Recombinant adenoviruses (Ad) are among the most extensively used vectors for liver gene transfer. One of the major limitations for the clinical application of these vectors is the inflammatory immune response associated with systemic administration of high dose of virus. We evaluated the effect of Ad administration route on the inflammatory immune response and liver transgene expression. We compared direct intrahepatic injection (IH) with the systemic administration via tail vein (IV). IH injection of Ad resulted in a lower inflammatory response and a higher transgene expression. When a relatively low dose of virus was used, IV administration resulted in no detectable protein expression but production of proinflammatory cytokines. In contrast, IH administration induced high levels of transgene expression and no inflammation, although we detected a transient hypertransaminemia, which fully resolved within days. Furthermore, IH injection resulted in a faster protein expression being more intense at the site of injection, whereas IV administration caused slower but diffuse liver expression. IH injection also reduced the spreading of the virus to other organs. Independently of the route, depletion of Kupffer cells significantly enhanced the transduction efficiency of Ad. This effect was stronger when using IV injection, indicating that IH injection partially overcomes Kupffer cell phagocytic activity. Moreover, the antitumor efficacy of high-capacity-Ad encoding murine interleukin-12 (IL-12) was significantly greater when the vector was administered by IH injection than when given IV. In conclusion, IH injection of adenovirus represents a safe and efficient administration route for clinical applications of gene therapy targeting the liver.

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.

[New therapies for hepatitis C]

Hepatitis C virus is an important public health threat, not only because of the high prevalence of this infection in western and third world countries, but also because of the high rate of resistance to the available antiviral therapy that consists on the use of pegylated interferon plus ribavirin. Currently, new forms of therapy are being developed based on a more precise knowledge of the structure and function of the viral proteins and of the strategies used by the virus to escape the immune and interferon systems. The new therapeutic approaches aim at different objectives: a) the inhibition of viral replication by blocking the viral protease and/or replicase; b) the use of other types of interferon with more potent antiviral effect, c) the induction of a specific anti-viral immune response by means of immunomodulatory compounds or therapeutic vaccination, d) the blockade of "de novo" infection of other cells with neutralizing antibodies, e) the induction of a antiviral state in the liver by transferring to this organ the gene of interferon and/or immunostimulating cytokines.

Therapy of cancer by cytokines mediated by gene therapy approach

Gene therapy offers a new approach for treatment of cancer. Transfer of genes encoding immunostimulatory cytokines has been used with remarkable success to eliminate cancer in animals. However, clinical trials in patients with this strategy had limited efficacy. Therefore, improvement of gene transfer vector system is necessary. A hybrid viral vector, consisting of SFV replicon with either murine IL-12 or reporter LacZ gene, was constructed. This hybrid vector showed specificity and high level of expression in HCC both in vitro and in vivo. In a rat orthotropic liver tumor model, treatment of established tumors by the hybrid vector with mIL-12 gene resulted in a strong anti-tumor activity without accompanying toxicity. Subsequently, a helper-dependent adenovirus vectors containing a mifepristone (RU486) inducible system was constructed for controlled and liver-specific expression of human interleukin 12 (hIL-12) (HD-Ad/RUhIL-12) and mouse IL-12 (mIL-12) (HD-Ad/RUmIL-12). Data showed that high and sustained serum levels of hIL-12 could be attained by continuing administration of RU486 every 12 or 24 h. Repetitive induction of hIL-12 could be obtained over, at least, a period of 48 weeks after a single injection of HD-Ad/RUhIL-12. Treatment of liver metastases with of HD-Ad/RUmIL-12 plus RU846 resulted in complete tumor regression in all animals. Then, different cytokine genes were inserted into conditional replicative adenoviruses vectors (also called oncolytic adenovirus). Replication of adenovirus in tumor cells would kill tumor cells and release viruses, which infect surrounding tumor cells. The combination of cytopathic effect by oncolytic adenovirus and biological effect of transgene would exert strong antitumor activity. These new types of vectors may provide a potent and safe tool for cancer gene therapy.