An optimal therapeutic expression level is crucial for suicide gene therapy for hepatic metastatic cancer in mice

Applications of tissue-specific and cancer-selective gene promoters for cancer diagnosis and therapy

Current treatment of solid tumors with standard of care chemotherapies, radiation therapy and/or immunotherapies are often limited by severe adverse toxic effects, resulting in a narrow therapeutic index. Cancer gene therapy represents a targeted approach that in principle could significantly reduce undesirable side effects in normal tissues while significantly inhibiting tumor growth and progression. To be effective, this strategy requires a clear understanding of the molecular biology of cancer development and evolution and developing biological vectors that can serve as vehicles to target cancer cells. The advent and fine tuning of omics technologies that permit the collective and spatial recognition of genes (genomics), mRNAs (transcriptomics), proteins (proteomics), metabolites (metabolomics), epiomics (epigenomics, epitranscriptomics, and epiproteomics), and their interactomics in defined complex biological samples provide a roadmap for identifying crucial targets of relevance to the cancer paradigm. Combining these strategies with identified genetic elements that control target gene expression uncovers significant opportunities for developing guided gene-based therapeutics for cancer. The purpose of this review is to overview the current state and potential limitations in developing gene promoter-directed targeted expression of key genes and highlights their potential applications in cancer gene therapy.

Adenovirus Biology, Recombinant Adenovirus, and Adenovirus Usage in Gene Therapy

Gene therapy is currently in the public spotlight. Several gene therapy products, including oncolytic virus (OV), which predominantly replicates in and kills cancer cells, and COVID-19 vaccines have recently been commercialized. Recombinant adenoviruses, including replication-defective adenoviral vector and conditionally replicating adenovirus (CRA; oncolytic adenovirus), have been extensively studied and used in clinical trials for cancer and vaccines. Here, we review the biology of wild-type adenoviruses, the methodological principle for constructing recombinant adenoviruses, therapeutic applications of recombinant adenoviruses, and new technologies in pluripotent stem cell (PSC)-based regenerative medicine. Moreover, this article describes the technology platform for efficient construction of diverse "CRAs that can specifically target tumors with multiple factors" (m-CRAs). This technology allows for modification of four parts in the adenoviral E1 region and the subsequent insertion of a therapeutic gene and promoter to enhance cancer-specific viral replication (i.e., safety) as well as therapeutic effects. The screening study using the m-CRA technology successfully identified survivin-responsive m-CRA (Surv.m-CRA) as among the best m-CRAs, and clinical trials of Surv.m-CRA are underway for patients with cancer. This article also describes new recombinant adenovirus-based technologies for solving issues in PSC-based regenerative medicine.

Optimization of adenoviral gene transfer in human pluripotent stem cells

Human pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem cells, have the potential to differentiate into a wide variety of cells in vitro and have applications in basic developmental biology research and regenerative medicine. To understand the process of differentiation from pluripotent stem cells to functional cells, it is necessary to efficiently and safely transfer and express exogenous genes. We attempted to optimize the efficient transfer of genes into pluripotent stem cells using adenoviral vectors. Comparative study of the activities of three representative ubiquitously active promoters revealed that only the CA promoter allowed robust transgene expression in human pluripotent stem cells. In addition, we established a protocol that allowed us to efficiently introduce target genes and ensure their expression even in small numbers of cells. Adenoviral vector infection of pluripotent stem cells in single-cell suspension culture yielded high gene transfer efficiency with low cytotoxicity, without losing the undifferentiated state of the pluripotent stem cells. This optimized system will facilitate developmental biology research and regenerative medicine using pluripotent stem cells.

Metabolic engineering generates a transgene-free safety switch for cell therapy

Safeguard mechanisms can ameliorate the potential risks associated with cell therapies but currently rely on the introduction of transgenes. This limits their application owing to immunogenicity or transgene silencing. We aimed to create a control mechanism for human cells that is not mediated by a transgene. Using genome editing methods, we disrupt uridine monophosphate synthetase (UMPS) in the pyrimidine de novo synthesis pathway in cell lines, pluripotent cells and primary human T cells. We show that this makes proliferation dependent on external uridine and enables us to control cell growth by modulating the uridine supply, both in vitro and in vivo after transplantation in xenograft models. Additionally, disrupting this pathway creates resistance to 5-fluoroorotic acid, which enables positive selection of UMPS-knockout cells. We envision that this approach will add an additional level of safety to cell therapies and therefore enable the development of approaches with higher risks, especially those that are intended for limited treatment durations.

Cancer-type organic anion transporting polypeptide 1B3 is a target for cancer suicide gene therapy using RNA trans-splicing technology

Cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3) has been identified as a cancer-specific transcript in various solid cancers, including colorectal cancer. Given its excellent cancer-specific expression profile, we hypothesized that Ct-OATP1B3 could represent a promising target for cancer-specific expression of the suicide gene, herpes simplex virus 1 thymidine kinase (HSV-tk), via a spliceosome-mediated RNA trans-splicing (SMaRT) approach. SMaRT technology is used to recombine two RNA molecules to generate a chimeric transcript. In this study, we engineered an RNA trans-splicing molecule carrying a translation-defective HSV-tk sequence (RTM44), which was capable of inducing its own trans-splicing to the desired Ct-OATP1B3 pre-mRNA target. RTM44 expression in LS180 cells resulted in generation of Ct-OATP1B3/HSV-tk fusion mRNA. A functional translation start site contributed by the target pre-mRNA restored HSV-tk protein expression, rendering LS180 cells sensitive to ganciclovir treatment in vitro and in xenografted mice. The observed effects are ascribed to accurate and efficient trans-splicing, as they were absent in cells carrying a splicing-deficient mutant of RTM44. Collectively, our data highlights Ct-OATP1B3 as an ideal target for the HSV-tk SMaRT suicide system, which opens up new translational avenues for Ct-OATP1B3-targeted cancer therapy.

A Novel Construction of Lentiviral Vectors for Eliminating Tumorigenic Cells from Pluripotent Stem Cells

The risk of tumor formation poses a challenge for human pluripotent stem cell (hPSC)-based transplantation therapy. Specific and total elimination of tumorigenic hPSCs by suicide genes (SGs) has not been achieved because no methodology currently exists for testing multiple candidate transgene constructs. Here, we present a novel method for efficient generation of tumorigenic cell-targeting lentiviral vectors (TC-LVs) with diverse promoters upstream of a fluorescent protein and SGs. Our two-plasmid system achieved rapid and simultaneous construction of different TC-LVs with different promoters. Ganciclovir (GCV) exerted remarkable cytotoxicity in herpes simplex virus thymidine kinase-transduced hPSCs, and high specificity for undifferentiated cells was achieved using the survivin promoter (TC-LV.Surv). Moreover, GCV treatment completely abolished teratoma formation by TC-LV.Surv-infected hPSCs transplanted into mice, without harmful effects. Thus, TC-LV can efficiently identify the best promoter and SG for specific and complete elimination of tumorigenic hPSCs, facilitating the development of safe regenerative medicine.

Viral Vector-Based Innovative Approaches to Directly Abolishing Tumorigenic Pluripotent Stem Cells for Safer Regenerative Medicine

Human pluripotent stem cells (hPSCs) are a promising source of regenerative material for clinical applications. However, hPSC transplant therapies pose the risk of teratoma formation and malignant transformation of undifferentiated remnants. These problems underscore the importance of developing technologies that completely prevent tumorigenesis to ensure safe clinical application. Research to date has contributed to establishing safe hPSC lines, improving the efficiency of differentiation induction, and indirectly ensuring the safety of products. Despite such efforts, guaranteeing the clinical safety of regenerative medicine products remains a key challenge. Given the intrinsic genome instability of hPSCs, selective growth advantage of cancer cells, and lessons learned through failures in previous attempts at hematopoietic stem cell gene therapy, conventional strategies are unlikely to completely overcome issues related to hPSC tumorigenesis. Researchers have recently embarked on studies aimed at locating and directly treating hPSC-derived tumorigenic cells. In particular, novel approaches to directly killing tumorigenic cells by transduction of suicide genes and oncolytic viruses are expected to improve the safety of hPSC-based therapy. This article discusses the current status and future perspectives of methods aimed at directly eradicating undifferentiated tumorigenic hPSCs, with a focus on viral vector transduction.

Heparin-binding epidermal growth factor-like growth factor and hepatocyte growth factor inhibit cholestatic liver injury in mice through different mechanisms

In contrast to hepatocyte growth factor (HGF), the therapeutic potential and pathophysiologic roles of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in liver diseases remain relatively unknown. To address the lack of effective pharmacologic treatments for cholestatic liver injuries, as well as to clarify the biologic features of these growth factors, we explored the effects of HB-EGF and HGF in mice with cholestatic liver injury induced by bile duct ligation (BDL). The mice were assessed 3, 5 and/or 14 days after BDL (acute, subacute and/or chronic phases, respectively) and intravenous injection of adenoviral vector expressing LacZ (control), HB-EGF, HGF, or HB-EGF and HGF. HB-EGF, HGF, or a combination of the growth factors exerted potent antioncotic (antinecrotic), antiapoptotic, anticholestatic, and regenerative effects on hepatocytes in vivo, whereas no robust antiapoptotic or regenerative effects were detected in interlobular bile ducts. Based on serum transaminase levels, the acute protective effects of HB-EGF on hepatocytes were greater than those of HGF. On the other hand, liver fibrosis and cholestasis during the chronic phase were more potently inhibited by HGF compared with HB-EGF. Compared with either growth factor alone, combining HB-EGF and HGF produced greater anticholestatic and regenerative effects during the chronic phase. Taken together, these findings suggest that HB-EGF and HGF inhibited BDL-induced cholestatic liver injury, predominantly by exerting acute cytoprotective and chronic antifibrotic effects, respectively; combining the growth factors enhanced the anticholestatic effects and liver regeneration during the chronic phase. Our results contribute to a better understanding of the pathophysiologic roles of HB-EGF and HGF, as well as to the development of novel effective therapies for cholestatic liver injuries.

Conditionally replicating adenovirus prevents pluripotent stem cell-derived teratoma by specifically eliminating undifferentiated cells

Incomplete abolition of tumorigenicity creates potential safety concerns in clinical trials of regenerative medicine based on human pluripotent stem cells (hPSCs). Here, we demonstrate that conditionally replicating adenoviruses that specifically target cancers using multiple factors (m-CRAs), originally developed as anticancer drugs, may also be useful as novel antitumorigenic agents in hPSC-based therapy. The survivin promoter was more active in undifferentiated hPSCs than the telomerase reverse transcriptase (TERT) promoter, whereas both promoters were minimally active in differentiated normal cells. Accordingly, survivin-responsive m-CRA (Surv.m-CRA) killed undifferentiated hPSCs more efficiently than TERT-responsive m-CRAs (Tert.m-CRA); both m-CRAs exhibited efficient viral replication and cytotoxicity in undifferentiated hPSCs, but not in cocultured differentiated normal cells. Pre-infection of hPSCs with Surv.m-CRA or Tert.m-CRA abolished in vivo teratoma formation in a dose-dependent manner following hPSC implantation into mice. Thus, m-CRAs, and in particular Surv.m-CRAs, represent novel antitumorigenic agents that could facilitate safe clinical applications of hPSC-based regenerative medicine.

Noninvasive theranostic imaging of HSV-TK/GCV suicide gene therapy in liver cancer by folate-targeted quantum dot-based liposomes

We have successfully developed folate-targeting liposomes for effective and safe HSV-TK suicide gene theranostics.

Survivin-responsive conditionally replicating adenovirus kills rhabdomyosarcoma stem cells more efficiently than their progeny

Background

Effective methods for eradicating cancer stem cells (CSCs), which are highly tumorigenic and resistant to conventional therapies, are urgently needed. Our previous studies demonstrated that survivin-responsive conditionally replicating adenoviruses regulated with multiple factors (Surv.m-CRAs), which selectively replicate in and kill a broad range of cancer-cell types, are promising anticancer agents. Here we examined the therapeutic potentials of a Surv.m-CRA against rhabdomyosarcoma stem cells (RSCs), in order to assess its clinical effectiveness and usefulness.

Methods

Our previous study demonstrated that fibroblast growth factor receptor 3 (FGFR3) is a marker of RSCs. We examined survivin mRNA levels, survivin promoter activities, relative cytotoxicities of Surv.m-CRA in RSC-enriched (serum-minus) vs. RSC-exiguous (serum-plus) and FGFR3-positive vs. FGFR3-negative sorted rhabdomyosarcoma cells, and the in vivo therapeutic effects of Surv.m-CRAs on subcutaneous tumors in mice.

Results

Both survivin mRNA levels and survivin promoter activities were significantly elevated under RSC-enriched relative to RSC-exiguous culture conditions, and the elevation was more prominent in FGFR3-positive vs. FGFR3-negative sorted cells than in RSC-enriched vs. RSC-exiguous conditions. Although Surv.m-CRA efficiently replicated and potently induced cell death in all populations of rhabdomyosarcoma cells, the cytotoxic effects were more pronounced in RSC-enriched or RSC-purified cells than in RSC-exiguous or progeny-purified cells. Injections of Surv.m-CRAs into tumor nodules generated by transplanting RSC-enriched cells induced significant death of rhabdomyosarcoma cells and regression of tumor nodules.

Conclusions

The unique therapeutic features of Surv.m-CRA, i.e., not only its therapeutic effectiveness against all cell populations but also its increased effectiveness against CSCs, suggest that Surv.m-CRA is promising anticancer agent.

Diffuse encephaloventriculitis and substantial leukoencephalopathy after intraventricular administration of recombinant adenovirus

OBJECTIVES

The use of recombinant adenovirus as a vehicle for gene transfer into ependymal cells is a potential therapeutic tool for the treatment of various neural disorders. However, gene transfer into the ependymal cells of the ventricular wall is associated with high-level expression of the transferred gene, which declines rapidly. The purpose of this study is to understand the cause of this early decline in gene expression.

METHODS

Different doses of adenovirus-expressing beta-galactosidase (Ad-beta-gal) were injected into the lateral brain ventricle of C57BL/6 mice, and the brains were observed histologically and with magnetic resonance (MR) imaging for a month.

RESULTS

Inoculation of the lateral ventricle with more than 1 x 10(8) viral particles (2.6 x 10(6) pfu) resulted in a rapid decline of beta -gal expression. MR imaging indicated gradual ventriculomegaly and histological analysis showed the loss of the ependymal cells from the ventricular wall, lymphocytes infiltration near the wall, degeneration of myelinated fibers and apoptosis in the external capsule. Reactive astrocytes proliferated in the external capsule 17 days following inoculation. To avoid this irreversible brain atrophy, the inoculated adenovirus should be reduced to less than 1 x 10(7) particles (2.6 x 10(5) pfu) in mice.

DISCUSSION

Our results indicate the presence of a unique and diffuse immune response of the brain; therefore, the clinical use of recombinant virus for intraventricular gene transfer must be carefully evaluated.

A programmable NOR-based device for transcription profile analysis

An autonomous synthetic programmable device that can diagnose a cell's state according to predefined markers and produce a corresponding therapeutic output may be the basis of future programmable drugs. Motivated to increase diagnosis precision, devices that integrate multiple disease markers have been implemented based on various molecular tools. As simplicity is key to future in-vivo applications, we sought a molecular device that a) integrates multiple inputs without requiring pairwise interactions, and b) harnesses only mechanisms that cells natively use. Here we show a synthetic NOR-based programmable device, operating via a biochemical obstructing approach rather than on a constructive approach, capable of differentiating between prokaryotic cell strains based on their unique expression profile. To demonstrate our system's strengths we further implemented the NOT, OR and AND gates. The device's programmability allows context-dependent selection of the inputs being sensed, and of the expressed output, thus, holding great promise in future biomedical applications.

Improved retroviral suicide gene transfer in colon cancer cell lines after cell synchronization with methotrexate

Background

Cancer gene therapy by retroviral vectors is mainly limited by the level of transduction. Retroviral gene transfer requires target cell division. Cell synchronization, obtained by drugs inducing a reversible inhibition of DNA synthesis, could therefore be proposed to precondition target cells to retroviral gene transfer. We tested whether drug-mediated cell synchronization could enhance the transfer efficiency of a retroviral-mediated gene encoding herpes simplex virus thymidine kinase (HSV-tk) in two colon cancer cell lines, DHDK12 and HT29.

Methods

Synchronization was induced by methotrexate (MTX), aracytin (ara-C) or aphidicolin. Gene transfer efficiency was assessed by the level of HSV-TK expression. Transduced cells were driven by ganciclovir (GCV) towards apoptosis that was assessed using annexin V labeling by quantitative flow cytometry.

Results

DHDK12 and HT29 cells were synchronized in S phase with MTX but not ara-C or aphidicolin. In synchronized DHDK12 and HT29 cells, the HSV-TK transduction rates were 2 and 1.5-fold higher than those obtained in control cells, respectively. Furthermore, the rate of apoptosis was increased two-fold in MTX-treated DHDK12 cells after treatment with GCV.

Conclusions

Our findings indicate that MTX-mediated synchronization of target cells allowed a significant improvement of retroviral HSV-tk gene transfer, resulting in an increased cell apoptosis in response to GCV. Pharmacological control of cell cycle may thus be a useful strategy to optimize the efficiency of retroviral-mediated cancer gene therapy.

Assessment of an altered E1B promoter on the specificity and potency of triple-regulated conditionally replicating adenoviruses: implications for the generation of ideal m-CRAs

Although previous studies modified two components of conditionally replicating adenoviruses (CRAs), which selectively replicate in and kill cancer cells, the most accurate ways to achieve increased cancer specificity (that is, safety) without reducing the anticancer (that is, therapeutic) effects are unknown. Here, we generated two types of survivin-responsive m-CRAs (Surv.m-CRAs), Surv.m-CRA-CMVp and Surv.m-CRA-OCp, which use two and three different mechanisms to target cancer, that is, early region 1A (E1A) regulated by the survivin promoter and mutated E1BΔ55K regulated by the ubiquitously active cytomegalovirus promoter and cancer/tissue-specific osteocalcin promoter, respectively, and carefully examined their safety and anticancer effects. Endogenous osteocalcin mRNA was expressed and further enhanced by vitamin D(3) in all osteosarcoma and prostate cancer cell lines and human osteoblasts, but not in human fibroblasts. The osteocalcin promoter activity was weak even with vitamin D(3) treatment in these osteocalcin-expressing cancers, leading to low E1BΔ55K expression after Surv.m-CRA-OCp infection. Nevertheless, Surv.m-CRA-OCp had significantly increased cancer specificity without reduced anticancer effects in both in vitro and in vivo experiments. The unexpected but favorable fact that strong activity of an altered E1B promoter is unnecessary indicates that the majority of cancer/tissue-specific promoters may be used to generate ideal m-CRAs and will advance the development of m-CRA-based cancer therapies.

Leptin gene therapy in the fight against diabetes

IMPORTANCE OF THE FIELD

The incidence of diabetes is increasing worldwide, yet current treatments are not always effective for all patient or disease types.

AREAS COVERED IN THIS REVIEW

Here, we summarize the biologic and clinical roles of leptin in diabetes, and discuss candidate viral vectors that may be employed in the clinical use of central leptin gene therapy for diabetes.

WHAT THE READER WILL GAIN

We discuss how studies on leptin, a regulator of the insulin-glucose axis, have significantly advanced our understanding of the roles of energy homeostasis and insulin resistance in the pathogeneses of metabolic syndrome and diabetes. Recent studies have demonstrated the long-term therapeutic effects of central leptin gene therapy in obesity and diabetes via decreased insulin resistance and increased glucose metabolism. Many of these studies have employed viral vectors, which afford high in vivo gene transduction efficiencies compared with non-viral vectors.

TAKE HOME MESSAGE

Adeno-associated viral vectors are particularly well suited for central leptin gene therapy owing to their low toxicity and ability to drive transgene expression for extended periods.

Polymeric nanoparticles containing conjugated phospholipase A2 for nonviral gene delivery

Polyethylenimine (PEI) was conjugated to phospholipase A(2) (PLA(2)) in an effort to improve transfection efficiency. PLA(2) was conjugated to PEI using EDC as a coupling reagent. The activity of enzyme in the conjugate was measured. DNA condensation ability of the conjugate to polymer was determined. The resultant nanoparticles were characterized by dynamic and electrophoretic light scattering. Two reporter genes were used to evaluate transfection efficiency in human embryonic kidney (HEK293) and human hepatoma (HepG2) cell lines. Conjugate was shown to retain PLA(2) activity and its ability to condense plasmid DNA, resulting in nanoparticles of a similar size to native PEI. The results demonstrated at N/P ratios of 15 and 20 showed 13- and 8-fold increase in transfection efficiency, respectively, compared to the maximum transfection efficiency of PEI (N/P ratio of 5) in the whole range of N/P ratios tested, from 5 to 60 in HepG2 cells. Toxicity studies in HepG2 cells showed uncomplexed conjugate had similar toxicity as PEI, and when complexed with DNA the conjugate had a significantly reduced toxicity. The results clearly indicate the potential for this approach to improve efficiencies of nonviral gene delivery vectors.

Differences in gene expression between sonoporation in tumor and in muscle

BACKGROUND

Ultrasound (US) is a novel and effective tool for the local delivery of genes into target tissues. US can temporarily change the permeability of a cell membrane and thus enhance the delivery of naked DNA into cells. In the present study, the efficiencies of gene expression mediated by US delivery in orthotopic liver tumor, subcutaneous tumor and muscle tissue were evaluated by changing the contrast agent concentrations and US exposure durations.

METHODS

Plasmid DNA coding for luciferase, interleukin-12 or enhanced green fluorescence protein was mixed with SonoVue and injected intratumorally or intramuscularly. The injection sites were then exposed to US (20% duty cycle and 0.4 W/cm(2) intensity).

RESULTS

The results obtained showed that the optimal condition was 50% SonoVue for tumors and 30% for muscle, with 10 min of US exposure. The expression levels of the transfected DNAs were in the order: muscle > subcutaneous tumor > orthotopic liver tumor.

CONCLUSIONS

The present study indicates that muscle tissue is a good target site for producing large amounts of gene products for the purpose of gene therapy.

Gene transfer: the challenge of regulated gene expression

Gene therapy is expected to have a major impact on human healthcare in the future. However, precise regulation of therapeutic gene expression in vivo is still a challenge. Natural and synthetic enhancer-promoters (EPs) can be utilized to drive gene transcription in a temporal, spatial or environmental signal-inducible manner in response to heat shock, hypoxia, radiation, chemotherapy, epigenetic agents or viral infection. To allow tightly regulated expression, a regulatable gene-expression system can also be implemented. Most of these systems are based on small molecule (drug)-responsive artificial transactivators. In this review, we aim to provide a brief overview of the classes of EPs and regulatable systems, along with lessons learned from these studies. We highlight the potential applications in gene transfer, gene therapy for cancer and genetic disease and the future challenges for clinical applications.

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.

Adenoviral gene therapy in gastric cancer: A review

Gastric cancer is one of the most common malignancies worldwide. With current therapeutic approaches the prognosis of gastric cancer is very poor, as gastric cancer accounts for the second most common cause of death in cancer related deaths. Gastric cancer like almost all other cancers has a molecular genetic basis which relies on disruption in normal cellular regulatory mechanisms regarding cell growth, apoptosis and cell division. Thus novel therapeutic approaches such as gene therapy promise to become the alternative choice of treatment in gastric cancer. In gene therapy, suicide genes, tumor suppressor genes and anti-angiogenesis genes among many others are introduced to cancer cells via vectors. Some of the vectors widely used in gene therapy are Adenoviral vectors. This review provides an update of the new developments in adenoviral cancer gene therapy including strategies for inducing apoptosis, inhibiting metastasis and targeting the cancer cells.

Adenovirus tumor targeting and hepatic untargeting by a coxsackie/adenovirus receptor ectodomain anti-carcinoembryonic antigen bispecific adapter

Adenovirus vectors have a number of advantages for gene therapy. However, because of their lack of tumor tropism and their preference for liver infection following systemic administration, they cannot be used for systemic attack on metastatic disease. Many epithelial tumors (e.g., colon, lung, and breast) express carcinoembryonic antigen (CEA). To block the natural hepatic tropism of adenovirus and to "retarget" the virus to CEA-expressing tumors, we used a bispecific adapter protein (sCAR-MFE), which fuses the ectodomain of the coxsackie/adenovirus receptor (sCAR) with a single-chain anti-CEA antibody (MFE-23). sCAR-MFE untargets adenovirus-directed luciferase transgene expression in the liver by >90% following systemic vector administration. Moreover, sCAR-MFE can "retarget" adenovirus to CEA-positive epithelial tumor cells in cell culture, in s.c. tumor grafts, and in hepatic tumor grafts. The sCAR-MFE bispecific adapter should, therefore, be a powerful agent to retarget adenovirus vectors to epithelial tumor metastases.

Local delivery system of cytotoxic agents to tumors by focused sonoporation

Recently, ultrasound-targeting microbubble destruction has been employed in molecular gene therapy, and a new potent nonviral gene transfer method known as 'sonoporation' has been developed. We investigated the efficiency of sonoporation toward growth inhibition of human gingival squamous carcinoma cell line, Ca9-22, in vitro and in vivo. The cytotoxicity of bleomycin (BLM) was investigated using flow-cytometric analysis and Hoechst's staining in vitro assay systems. We found that the delivery of BLM by sonoporation induced cytotoxic effect toward Ca9-22 cells in vitro. Our in vivo results showed that tumors nearly disappeared in Ca9-22 cell-implanted nude KSN/slc mice treated with a low dose of BLM followed by sonoporation during the 4-week experimental period. Histological analysis revealed that the cytotoxic effect was mainly apoptosis. We previously reported that the cytolethal distending toxin B (cdtB) from Actinobacillus actinomycetemcomitans, a periodontopathic bacterium, is responsible for cell cycle arrest and apoptosis in vitro. Thus, we used sonoporation to transfect a cdtB-expressing plasmid into Ca9-22 cells and examined cell viability in vitro and in vivo. We found that an administration of cdtB-expressing plasmid followed by sonoporation-induced marked growth inhibition of Ca9-22 cells and apoptotic cells were also observed in vitro and in vivo. These findings suggest that local administration of cytotoxic agents with sonoporation is a useful method for molecular cancer therapy.

Identification and isolation of embryonic stem cell-derived target cells by adenoviral conditional targeting

The technical limitations of isolating target cells have restricted the utility of pluripotent embryonic stem (ES) cells. For example, early cardiac (i.e., precontractile) cells have not been isolated from ES cells. Here, we find that direct expression of reporter genes under cell-specific promoters-the currently available strategy for isolating cells lacking cell-specific surface markers-is ineffective for isolating progenitor cells. This was due to the weak activity of cell-specific promoters, particularly in ES cells at early stages. We show that adenoviral conditional targeting efficiently isolates viable ES cell-derived target cells without harmful effects. In this strategy, we employ the alpha-myosin heavy chain and Nkx2.5 promoter to visualize and purify efficiently differentiated and primitive cells of the cardiac lineage, respectively. While the former cells predominantly expressed sarcomeric proteins and maintained contractile function, the latter demonstrated neither of these features, but rather exhibited expression patterns characteristic of a mixture of primitive cells and cardiomyocytes. Interestingly, smooth muscle actin was predominantly expressed in the latter cells, and both functionally known and unknown genes were systematically identified, demonstrating the benefits of this system. Thus, our method facilitates molecular and cellular studies of development and ES cell-derived cell therapy.

In vivo hepatic HB-EGF gene transduction inhibits Fas-induced liver injury and induces liver regeneration in mice: a comparative study to HGF

BACKGROUND/AIMS

It is unknown whether heparin-binding EGF-like growth factor (HB-EGF) can be a therapeutic agent, although previous studies suggested that HB-EGF might be a hepatotrophic factor. This study explores the potential of hepatic HB-EGF gene therapy in comparison with HGF.

METHODS

Mice received an intraperitoneal injection of the agonistic anti-Fas antibody 72 h after an intravenous injection of either adenoviral vector (1x10(11) particles) expressing human HB-EGF (Ad.HB-EGF), human HGF (Ad.HGF) or no gene (Ad.dE1.3), and were sacrificed 24 or 36 h later to assess liver injury and regeneration.

RESULTS

Exogenous HB-EGF was predominantly localized on the membrane, suggesting the initial synthesis of proHB-EGF in hepatocytes. The control Ad.dE1.3-treated mice represented remarkable increases in serum ALT and AST levels and histopathologically severe liver injuries with numerous apoptosis, but a limited number of mitogenic hepatocytes. In contrast, the liver injuries and apoptotic changes were significantly inhibited, but the mitogenic hepatocytes remarkably increased, in both the Ad.HB-EGF- and Ad.HGF-treated mice. More mitogenic hepatocytes and milder injuries were observed in the Ad.HB-EGF-treated mice.

CONCLUSIONS

HB-EGF has more potent protective and mitogenic effects for hepatocytes than HGF, at least for the present conditions. In vivo hepatic HB-EGF gene transduction is therapeutic for Fas-induced liver injury.

An efficient construction of conditionally replicating adenoviruses that target tumor cells with multiple factors

Despite the enormous potential of conditionally replicating adenoviruses (CRAs), the time-consuming and laborious methods required to construct CRAs have hampered both the development of CRAs that can specifically target tumors with multiple factors (m-CRA) and the efficient analysis of diverse candidate CRAs. Here, we present a novel method for efficiently constructing diverse m-CRAs. Elements involving viral replication, therapeutic genes, and adenoviral backbones were separately introduced into three plasmids of P1, P2, and P3, respectively, which comprised different antibiotic resistant genes, different ori, and a single loxP (H) sequence. Independently constructed plasmids were combined at 100% accuracy by transformation with originally prepared Cre and specific antibiotics in specific Escherichia coli; transfection of the resulting P1+2+3 plasmids into 293 cells efficiently generated m-CRAs. Moreover, the simultaneous generation of diverse m-CRAs was achieved at 100% accuracy by handling diverse types of P1+2 and P3. Alternatively, co-transfection of P1+3 and P2 plasmids into Cre-expressing 293 cells directly generated m-CRA with therapeutic genes. Thus, our three-plasmid system, which allows unrestricted construction and efficient fusion of individual elements, should expedite the process of generating, modifying, and testing diverse m-CRAs for the development of the ideal m-CRA for tumor therapy.

Cancer-specific gene therapy

Cancer cells transcriptionally activate many genes that are important for uncontrolled proliferation and cell death. Deregulated transcriptional machinery in tumor cells usually consists of increased expression/activity of transcription factors. Ideally, cancer-specific killing can be achieved by delivering a therapeutic gene under the control of the DNA elements that can be activated by transcription factors that are overexpressed and/or constitutively activated in cancer cells. Additionally, tumor-specific translation of tumor-killing genes has been also exploited in cancer gene therapy. Based on these rationales, cancer-specific expression of a therapeutic gene has emerged as a potentially successful approach for cancer gene therapy. To achieve tumor-specific expression, cancer-specific vectors are generally composed of promoters, enhancers, and/or 5'-UTR that are responsive to tumor-specific transcription factors. A number of cancer-specific promoters have been reported, such as those of probasin, human telomerase reverse transcriptase, survivin, ceruloplasmin, HER-2, osteocalcin, and carcinoembryonic antigen. Evidences suggest that the enhancer element targeted by beta-catenin can be useful to target colon cancer cells. The 5'-UTR of the basic fibroblast growth factor-2 has been reported to provide tumor specificity. Moreover, a variety of therapeutic genes demonstrated direct antitumor effects such as those encoding proapoptotic proteins p53, E1A, p202, PEA3, BAX, Bik, and prodrug metabolizing enzymes, namely thymidine kinase and cytosine deaminase. As cancerous cells of different origins vary significantly in their genetic, transcriptional/translational, and cellular profiles, the success of a cancer gene therapy will not be promised unless it is carefully designed based on the biology of a specific tumor type. Thus, tremendous research efforts have been focused on the development of non-viral vectors that selectively target various tumors resulting in minimal toxicity in the normal tissues. Significant progresses were also made in the exploitation of various novel apoptotic, cytotoxic genes as therapeutic tools that suppress the growth of different tumors. Together, these recent advances provide rationales for future clinical testing of transcriptionally targeted non-viral vectors in cancer patients.

Survivin-responsive conditionally replicating adenovirus exhibits cancer-specific and efficient viral replication

Although a conditionally replicating adenovirus (CRA) exhibiting cancer-selective replication and induction of cell death is an innovative potential anticancer agent, current imperfections in cancer specificity and efficient viral replication limit the usefulness of this technique. Here, we constructed survivin-responsive CRAs (Surv.CRAs), in which expression of the wild-type or mutant adenoviral early region 1A (E1A) gene is regulated by the promoter of survivin, a new member of the inhibitor of apoptosis gene family. We explored the cancer specificity and effectiveness of viral replication of Surv.CRAs, evaluating their potential as a treatment for cancer. The survivin promoter was strongly activated in all cancers examined at levels similar to or even higher than those seen for representative strong promoters; in contrast, low activity was observed in normal cells. Surv.CRAs efficiently replicated and potently induced cell death in most types of cancer. In contrast, minimal viral replication in normal cells did not induce any detectable cytotoxicity. A single injection of Surv.CRAs into a preestablished tumor expressing survivin, even at relatively low levels, induced significant tumor death and inhibition of tumor growth. Furthermore, Surv.CRAs were superior to telomerase-dependent CRAs, one of the most effective CRAs that have been examined to date, both in terms of cancer specificity and efficiency. Thus, Surv.CRAs are an attractive potential anticancer agent that could effectively and specifically treat a variety of cancers.

Local overexpression of HB-EGF exacerbates remodeling following myocardial infarction by activating noncardiomyocytes

Insulin-like growth factor (IGF), hepatocyte growth factor (HGF), and heparin-binding epidermal growth factor-like growth factor (HB-EGF) are cardiogenic and cardiohypertrophic growth factors. Although the therapeutic effects of IGF and HGF have been well demonstrated in injured hearts, it is uncertain whether natural upregulation of HB-EGF after myocardial infarction (MI) plays a beneficial or pathological role in the process of remodeling. To answer this question, we conducted adenoviral HB-EGF gene transduction in in vitro and in vivo injured heart models, allowing us to highlight and explore the HB-EGF-induced phenotypes. Overexpressed HB-EGF had no cytoprotective or additive death-inducible effect on Fas-induced apoptosis or oxidative stress injury in primary cultured mouse cardiomyocytes, although it significantly induced hypertrophy of cardiomyocytes and proliferation of cardiac fibroblasts. Locally overexpressed HB-EGF in the MI border area in rabbit hearts did not improve cardiac function or exhibit an angiogenic effect, and instead exacerbated remodeling at the subacute and chronic stages post-MI. Namely, it elevated the levels of apoptosis, fibrosis, and the accumulation of myofibroblasts and macrophages in the MI area, in addition to inducing left ventricular hypertrophy. Thus, upregulated HB-EGF plays a pathophysiological role in injured hearts in contrast to the therapeutic roles of IGF and HGF. These results imply that regulation of HB-EGF may be a therapeutic target for treating cardiac hypertrophy and fibrosis.

Gene therapy for hepatocellular carcinoma using sonoporation enhanced by contrast agents

We examined whether sonoporation enhanced by a contrast agent (BR14) was effective in gene therapy for hepatocelluar carcinoma (HCC). Human hepatic cancer cells (SK-Hep1) and plasmid cDNAs expressing green fluorescent protein (GFP), interferonbeta (IFNbeta), and LacZ were used. In vitro, SK-Hep1 cell suspensions with DNA and BR14 were sonoporated. Expressions of every plasmid cDNA and the antitumor effect of IFNbeta were analyzed. In vivo, GFP and IFNbeta genes with BR14 were directly injected into subcutaneous tumors using SK-Hep1 in nude mice, and transcutaneous sonoporation of the tumors was performed. GFP gene transfections and tumor diameters after IFNbeta gene transfection were examined. In vitro, no SK-Hep1 cells were transfected without sonication, whereas transfections were successful after sonication with BR14. Antitumor effect of IFNbeta gene transfection by ultrasound (US) and with BR14 was revealed. In vivo, the SK-Hep1 cells expressed GFP, and the IFNbeta gene transfection by US with BR14 reduced tumor size significantly. In conclusion, gene therapy with sonoporation enhanced by a contrast agent may become a new treatment option for HCC.

Biochemical and Structural Characterization of (South)-Methanocarbathymidine That Specifically Inhibits Growth of Herpes Simplex Virus Type 1 Thymidine Kinase-transduced Osteosarcoma Cells

Two analogs of the natural nucleoside dT featuring a pseudosugar with fixed conformation in place of the deoxyribosyl residue (carbathymidine analogs) were biochemically and structurally characterized for their acceptance by both human cytosolic thymidine kinase isoenzyme 1 (hTK1) and herpes simplex virus type 1 thymidine kinase (HSV1 TK) and subsequently tested in cell proliferation assays. 3'-exo-Methanocarbathymidine ((South)-methanocarbathymidine (S)-MCT), which is a substrate for HSV1 TK, specifically inhibited growth of HSV1 TK-transduced human osteosarcoma cells with an IC(50) value in the range of 15 microM without significant toxicity toward both hTK1-negative (TK(-)) and non-transduced cells. 2'-exo-Methanocarbathymidine ((North)-methanocarbathymidine (N)-MCT), which is a weak substrate for hTK1 and a substantial one for HSV1 TK, induced a specific growth inhibition in HSV1 TK-transfected cells comparable to that of (S)-MCT and ganciclovir. A growth inhibition activity was also observed with (N)-MCT and ganciclovir in non-transduced cells in a cell line-dependent manner, whereas TK(-) cells were not affected. The presented 1.95-A crystal structure of the complex (S)-MCT.HSV1 TK explains both the more favorable binding affinity and catalytic turnover of (S)-MCT for HSV1 TK over the North analog. Additionally the plasticity of the active site of the enzyme is addressed by comparing the binding of (North)- and (South)-carbathymidine analogs. The presented study of these two potent candidate prodrugs for HSV1 TK gene-directed enzyme prodrug therapy suggests that (S)-MCT may be even safer to use than its North counterpart (N)-MCT.

Recent advances in molecular diagnosis and therapy of gastric cancer

Gastric cancer is the fourth most common malignancy and the second most frequent cause of cancer-related death in the world. It is often diagnosed in advanced stages when treatment options are limited, leading to a poor prognosis. During the past 15 years, much has been learnt about the molecular mechanisms of gastric carcinogenesis and the development of metastases. This coincided with the development of new techniques for functional genomics, including both transcriptomics and proteomics, which significantly improve the ability to explore new molecular alterations involved in carcinogenesis and tumor progression. An improved understanding of the molecular pathology and pathogenesis of gastric cancer may lead to a more rapid development of molecular diagnostic and patient tailored therapeutic targets.