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

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.

In vitro gene targeting in human hepatoblastoma

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

A trial of somatic gene targeting in vivo with an adenovirus vector

Background

Gene targeting in vivo provides a potentially powerful method for gene analysis and gene therapy. In order to sensitively detect and accurately measure designed sequence changes, we have used a transgenic mouse system, MutaMouse, which has been developed for detection of mutation in vivo. It carries bacteriophage lambda genome with lacZ⁺ gene, whose change to lacZ-negative allele is detected after in vitro packaging into bacteriophage particles. We have also demonstrated that gene transfer with a replication-defective adenovirus vector can achieve efficient and accurate gene targeting in vitro.

Methods

An 8 kb long DNA corresponding to the bacteriophage lambda transgene with one of two lacZ-negative single-base-pair-substitution mutant allele was inserted into a replication-defective adenovirus vector. This recombinant adenovirus was injected to the transgenic mice via tail-vein. Twenty-four hours later, genomic DNA was extracted from the liver tissue and the lambda::lacZ were recovered by in vitro packaging. The lacZ-negative phage was detected as a plaque former on agar with phenyl-beta-D-galactoside.

Results

The mutant frequency of the lacZ-negative recombinant adenovirus injected mice was at the same level with the control mouse (~1/10000). Our further restriction analysis did not detect any designed recombinant.

Conclusion

The frequency of gene targeting in the mouse liver by these recombinant adenoviruses was shown to be less than 1/20000 in our assay. However, these results will aid the development of a sensitive, reliable and PCR-independent assay for gene targeting in vivo mediated by virus vectors and other means.

Liver-directed gene expression employing synthetic transcriptional control units

AIM: To generate and characterize the synthetic transcriptional control units for transcriptional targeting of the liver, thereby compensating for the lack of specificity of currently available gene therapeutic vector systems.

METHODS: Synthetic transcriptional control unit constructs were generated and analyzed for transcriptional activities in different cell types by FACS quantification, semi-quantitative RT-PCR, and Western blotting.

RESULTS: A new bifunctionally-enhanced green fluorescent protein (EGFP)/neo^r fusion gene cassette was generated, and could flexibly be used both for transcript quantification and for selection of stable cell clones. Then, numerous synthetic transcriptional control units consisting of a minimal promoter linked to “naturally” derived composite enhancer elements from liver-specific expressed genes or binding sites of liver-specific transcription factors were inserted upstream of this reporter cassette. Following liposome-mediated transfection, EGFP reporter protein quantification by FACS analysis identified constructs encoding multimerized composite elements of the apolipoprotein B100 (ApoB) promoter or the ornithin transcarbamoylase (OTC) enhancer to exhibit maximum transcriptional activities in liver originating cell lines, but only background levels in non-liver originating cell lines. In contrast, constructs encoding only singular binding sites of liver-specific transcription factors, namely hepatocyte nuclear factor (HNF)1, HNF3, HNF4, HNF5, or CAAT/enhancer binding protein (C/EBP) only achieved background levels of EGFP expression. Finally, both semi-quantitative RT-PCR and Western blotting analysis of Hep3B cells demonstrated maximum transcriptional activities for a multimeric 4xApoB cassette construct, which fully complied with the data obtained by initial FACS analysis.

CONCLUSION: Synthetic transcriptional control unit constructs not only exhibit a superb degree of structural compactness, but also provide new means for liver-directed expression of therapeutic genes.

Low-dose adenoviral immunotherapy of rat hepatocellular carcinoma using single-chain interleukin-12

Generation of antitumor immunity by adenoviral gene transfer of interleukin-12 (IL-12) is a very promising concept in cancer gene therapy. Systemically, IL-12 has provoked toxic side effects at therapeutically relevant doses. Native IL-12 lacks effectiveness in clinical trials even when expressed intratumorally from adenoviral vectors. Our strategy was to increase the therapeutic efficacy of IL-12 by expressing a fusion protein of its two subunits (scIL-12) in an adenoviral vector and to evaluate the effects after intratumoral administration. In a rat model of hepatocellular carcinoma, this vector revealed antitumor effects even at a low dosage of 4.6 x 10(5) i.u. in a dose-dependent manner. Long-term antitumor effects were determined at 2.3 x 10(6) and 2.3 x 10(7) i.u. per animal, resulting in 82% and 90% surviving animals, respectively. Magnetic resonance imaging (MRI) enabled individual tumor size follow-up and revealed the scIL-12 effects on large tumors. Treating one hepatic lesion also led to tumor elimination in a second non-treated hepatic lesion. Animals rechallenged with tumor cells remained tumor-free. Compared to studies applying native IL-12, our data show that the fusion of IL-12 subunits provides approximately 1000-fold higher biological activity. As a consequence of the observed gain in activity, scIL12 promises a substantially improved antitumor efficacy and safety profile of intratumoral adenoviral IL-12 immunotherapy, supporting its clinical use.

The sphincter of Oddi: understanding its control and function

The most common functional disorders of the biliary tract and pancreas are associated with disordered motility of the sphincter of Oddi (SO). The SO is a neuromuscular structure located at the junction of the bile and pancreatic ducts with the duodenum. The primary functions of the SO are to regulate the delivery of bile and pancreatic juice into the duodenum, and to prevent the reflux of duodenal contents into the biliary and pancreatic systems. Disordered motility of the SO leads to the common and painful clinical conditions of SO dysfunction and acute pancreatitis. In order to understand normal SO motility, studies have been performed addressing SO function, control of spontaneous SO activity, responses to bioactive agents, SO innervation, and reflexes with other gastrointestinal organs. These studies have led to the current understanding of how the SO functions and may permit the development of targeted therapy for SO dysfunction and acute pancreatitis. This review summarizes the current knowledge regarding the control and regulation of SO motility, highlighting laboratory based and clinical research performed over the last 5 years.

Gene therapy of liver diseases

Many liver diseases lack satisfactory treatment and alternative therapeutic options are urgently needed. Gene therapy is a new mode of treatment for both inherited and acquired diseases, based on the transfer of genetic material to the tissues. Genes are incorporated into appropriate vectors in order to facilitate their entrance and function inside the target cells. Gene therapy vectors can be constructed on the basis of viral or non-viral molecular structures. Viral vectors are frequently used, due to their higher transduction efficiency. Both the type of vector and the expression cassette determine the duration, specificity and inducibility of gene expression. A considerable number of preclinical studies indicate that a great variety of liver diseases, including inherited metabolic defects, chronic viral hepatitis, liver cirrhosis and primary and metastatic liver cancer, are amenable to gene therapy. Gene transfer to the liver can also be used to convert this organ into a factory of secreted proteins needed to treat conditions that do not affect the liver itself. Clinical trials of gene therapy for the treatment of inherited diseases and liver cancer have been initiated but human gene therapy is still in its infancy. Recent progress in vector technology and imaging techniques, allowing in vivo assessment of gene expression, will facilitate the development of clinical applications of gene therapy.

Signaling pathways mediating gastrointestinal smooth muscle contraction and MLC20 phosphorylation by motilin receptors

The signaling cascades initiated by motilin receptors in gastric and intestinal smooth muscle cells were characterized. Motilin bound with high affinity (IC(50) 0.7 +/- 0.2 nM) to receptors on smooth muscle cells; the receptors were rapidly internalized via G protein-coupled receptor kinase 2 (GRK2). Motilin selectively activated G(q) and G(13), stimulated G alpha(q)-dependent phosphoinositide (PI) hydrolysis and 1,4,5-trisphosphate (IP(3))-dependent Ca(2+) release, and increased cytosolic free Ca(2+). PI hydrolysis was blocked by expression of G alpha(q) minigene and augmented by overexpression of dominant negative RGS4(N88S) or GRK2(K220R). Motilin induced a biphasic, concentration-dependent contraction (EC(50) = 1.0 +/- 0.2 nM), consisting of an initial peak followed by a sustained contraction. The initial Ca(2+)-dependent contraction and myosin light-chain (MLC)(20) phosphorylation were inhibited by the PLC inhibitor U-73122 and the MLC kinase inhibitor ML-9 but were not affected by the Rho kinase inhibitor Y27632 or the PKC inhibitor bisindolylmaleimide. Sustained contraction and MLC(20) phosphorylation were RhoA dependent and mediated by two downstream messengers: PKC and Rho kinase. The latter was partly inhibited by expression of G alpha(q) or G alpha(13) minigene and abolished by coexpression of both minigenes. Sustained contraction and MLC(20) phosphorylation were partly inhibited by Y27632 and bisindolylmaleimide and abolished by a combination of both inhibitors. The inhibition reflected phosphorylation of two MLC phosphatase inhibitors: CPI-17 via PKC and MYPT1 via Rho kinase. We conclude that motilin initiates a G alpha(q)-mediated cascade involving Ca(2+)/calmodulin activation of MLC kinase and transient MLC(20) phosphorylation and contraction as well as a sustained G alpha(q)- and G alpha(13)-mediated, RhoA-dependent cascade involving phosphorylation of CPI-17 by PKC and MYPT1 by Rho kinase, leading to inhibition of MLC phosphatase and sustained MLC(20) phosphorylation and contraction.

Transfection of IL-2 and/or IL-12 genes into spleen in treatment of rat liver cancer

AIM: To test the efficacy of gene therapy in rat liver tumor.

METHODS: A retroviral vector GCIL12EIL2PN encoding human IL-2 (hIL-2) and mouse IL-12 (mIL-12) fused gene and its packaging cell were constructed. The packaging cell lines contained of IL-2 and/or IL-12 genes were injected intrasplenically to transfect splenocyte at different time. The therapeutic effect, immune function and toxic effect were evaluated.

RESULTS: The average survival times of the 4 groups using IL genes at days 1, 3, 5 and 7 after tumor implantation were 53.3 ± 3.7, 49.3 ± 4.2, 31.0 ± 2.1 and 24.3 ± 1.4 d respectively in IL-2/IL-12 fused gene group, 25.0 ± 2.5, 23.5 ± 2.0, 18.3 ± 2.4 and 12.0 ± 1.8 d respectively in IL-2 gene treatment group, and 39.0 ± 4.8, 32.0 ± 3.9, 23.0 ± 2.5 and 19.4 ± 2.1 d respectively in IL-12 gene treatment group (P < 0.01, n = 10). In the IL-12/IL-2 fused gene treatment group, 30% of rats treated at days 1 and 3 survived more than 60 d and serum mIL-12 and hIL-2 levels were still high at day 3 after treatment. Compared with IL alone, NK cell activity was strongly stimulated by IL-2/IL-12 gene. Microscopy showed that livers were infiltrated by a number of lymphocytes.

CONCLUSION: IL-2 and/or IL-12 genes injected directly into spleen increase serum IL-2 and IL-12 levels and enhance the NK cell activity, which may inhibit the liver tumor growth. The therapy of fused gene IL-2/IL-12 is of low toxicity and relatively high NK cell activity. Our data suggest that IL-2/IL-12 fused gene may be a safe and efficient gene therapy for liver tumor. The gene therapy should be administrated as early as possible.