Transcriptional targeting of RGD fiber-mutant adenovirus vectors can improve the safety of suicide gene therapy for murine melanoma

Targeted gene therapy of the HSV-TK/hIL-12 fusion gene controlled by the hSLPI gene promoter of human non-small cell lung cancer in vitro

The incidence of lung cancer and lung cancer-associated mortality have markedly increased worldwide, and gene-targeted therapy has emerged as a promising treatment strategy. The present study aimed to explore the targeted antitumor effect of the herpes simplex virus-thymidine kinase/human interleukin-12 (HSV-TK/hIL-12) fusion gene regulated by the human secretory leukocyte protease inhibitor (hSLPI) promoter of human non-small cell lung cancer (hNSCLC). There were four recombinant eukaryotic expression vectors: pcDNA3.1-CMV-TK, pcDNA3.1-CMV-TK/hIL-12, pcDNA3.1-phSLP-TK and pcDNA3.1-phSLP-TK/hIL-12. These were constructed and transfected into the A549, SPC-A1 and HepG2 cell lines in vitro. The expression of the HSV-TK/hIL-12 fusion gene was detected with reverse transcription-polymerase chain reaction (RT-PCR), and the content of hIL-12 was measured using an ELISA. The antitumor effect of the fusion gene on the A549, SPC-A1 and HepG2 cell lines was determined using an MTT assay. Analysis of the experimental data demonstrated that genes regulated by the cytomegalovirus promoter were expressed at the same level in three different tumor cell lines. Genes regulated by the hSLPI promoter were expressed in the A549 and SPC-A1 cell lines, but not in the HepG2 cell line. Coincidentally, the hIL-12 expression levels were similar to those observed in previous RT-PCR findings. In the Pcmv-TK/Pcmv-TK-hIL-12 group for all three cell lines, as well as in the PSLPI-TK/PSLPI-TK-hIL-12 group for the A549 and SPC-A1 cell lines, the cell survival rate declined significantly and the fusion gene transfection group indicated a lower cell survival rate, when compared with single gene transfection group. The present study indicated that the fusion gene regulated by the hSLPI promoter had a targeted antitumor effect on hNSCLC, and that the combined suicide gene and immune gene therapy had a stronger antitumor effect, compared with single gene therapy.

Expression of HIF-1α ODD domain fused canine caspase 3 by EGFR promoter-driven adenovirus vector induces cytotoxicity in canine breast tumor cells under hypoxia

Adenovirus (Ad) vectors are widely used in cancer gene therapies. However, compared to human patients, relatively limited information is available on gene transduction efficiency or cell-specific cytotoxicity in canine tumor cells transduced with Ad vectors. Since epidermal growth factor receptor (EGFR) is highly expressed on canine breast tumor cells, we sought to develop an Ad vector based on the RGD fiber-mutant adenovirus vector (AdRGD) that expresses canine caspase 3 under the control of EGFR promoter. The aims of this study were to achieve high transduction efficiency with transgene expression restricted to canine breast tumor cells. Using EGFR promoter-driven AdRGD, we were able to restrict transgene expression to canine breast tumor cells with no evidence of expression in normal cells. Canine breast tumor cells transduced with EGFR promoter-driven AdRGD carrying canine caspase 3 gene showed cytotoxic activity. We constructed a second AdRGD vector that expressed oxygen-dependent degradation (ODD)-caspase 3 under the control of the EGFR promoter; the fusion protein contains a core part of the ODD domain of hypoxia inducible factor-1 alpha (HIF-1α) fused to caspase 3. Transduction of canine breast tumor cells with EGFR promoter-driven AdRGD expressing ODD-caspase 3 induced a higher rate of cell death under hypoxic conditions compared with under normoxia. The results indicate that the EGFR promoter-driven AdRGD vectors will be of value for tumor-specific transgene expression and safe cancer gene therapy in dogs.

Trojan horse at cellular level for tumor gene therapies

Among innovative strategies developed for cancer treatments, gene therapies stand of great interest despite their well-known limitations in targeting, delivery, toxicity or stability. The success of any given gene-therapy is highly dependent on the carrier efficiency. New approaches are often revisiting the mythic trojan horse concept to carry therapeutic nucleic acid, i.e. DNAs, RNAs or small interfering RNAs, to pathologic tumor site. Recent investigations are focusing on engineering carrying modalities to overtake the above limitations bringing new promise to cancer patients. This review describes recent advances and perspectives for gene therapies devoted to tumor treatment, taking advantage of available knowledge in biotechnology and medicine.

Chapter two--Adenovirus strategies for tissue-specific targeting

Cancer gene therapy approaches have benefited greatly from the utilization of molecular-based therapeutics. Of these, adenovirus-based interventions hold much promise as a platform for targeted therapeutic delivery to tumors. However, a barrier to this progression is the lack of native adenovirus receptor expression on a variety of cancer types. As such, any adenovirus-based cancer therapy must take into consideration retargeting the vector to nonnative cellular surface receptors. Predicated upon the knowledge gained in native adenovirus biology, several strategies to transductionally retarget adenovirus have emerged. Herein, we describe the biological hurdles as well as strategies utilized in adenovirus transductional targeting, covering the progress of both adapter-based and genetic manipulation-based targeting. Additionally, we discuss recent translation of these targeting strategies into a clinical setting.

In vivo bioluminescent imaging of α-fetoprotein-producing hepatocellular carcinoma in the diethylnitrosamine-treated mouse using recombinant adenoviral vector

BACKGROUND

The in vivo molecular imaging method is a useful tool for monitoring carcinogenesis in various hepatocellular carcinoma (HCC) models, such as xenografted-, chemical induced- and transgenic mice. The tumor-specific gene expression strategy, such as transcriptional targeting, is essential for achieving a lower toxicity for normal liver tissue in therapy and the monitoring of tumor progression in diagnosis, respectively. The present study aimed to visualize spontaneously developing α-fetoprotein (AFP)-producing HCC through targeted gene expression in tumors using recombinant adenoviral vector.

METHODS

The recombinant adenovirus vector, AdAFPfLuc (containing firefly luciferase gene driven by human AFP enhancer/promoter) was prepared. After in vitro infection by adenovirus, gene expression was confirmed using the luciferase assay, semi-quantitative reverse transcriptase-polymerase chain reaction and western blotting in AFP-producing and nonproducing cells. Tumor-bearing mice were intravenously injected with adenovirus, and bioluminescent images were obtained.

RESULTS

The expression of fLuc was efficiently demonstrated by the luciferase assay in AFP-producing cells but not in AFP-nonproducing cells. AFP-producing HCC targeted gene expression was confirmed at the mRNA and protein levels. After being injected intravenously in HuH-7 xenografts and HCC-bearing diethylnitrosamine-treated mice using adenovirus, functional reporter gene expression was confirmed in tumors by in vivo bioluminescent imaging (BLI).

CONCLUSIONS

The recombinant adenovirus vector system can be used to monitor spontaneously developing AFP-producing HCC and to evaluate targeted gene expression in tumors by in vivo BLI in a small animal model.

Systemic administration of a PEGylated adenovirus vector with a cancer-specific promoter is effective in a mouse model of metastasis

Cancer gene therapy by adenovirus vectors (Advs) for metastatic cancer is limited because systemic administration of Adv produces low therapeutic effect and severe side effects. In this study, we generated a dual cancer-specific targeting vector system by using PEGylation and the telomere reverse transcriptase (TERT) promoter and attempted to treat experimental metastases through systemic administration of the vectors. We first optimized the molecular size of PEG and modification ratios used to create PEG-Ads. Systemic administration of PEG-Ad with 20-kDa PEG at a 45% modification ratio (PEG[20K/45%]-Ad) resulted in higher tumor-selective transgene expression than unmodified Adv. Next, we examined the effectiveness against metastases and side effects of a TERT promoter-driven PEG[20K/45%]-Ad containing the herpes simplex virus thymidine kinase (HSVtk) gene (PEG-Ad-TERT/HSVtk). Systemic administration of PEG-Ad-TERT/HSVtk showed superior antitumor effects against metastases with negligible side effects. A cytomegalovirus (CMV) promoter-driven PEG[20K/45%]-Ad also produced antimetastatic effects, but these were accompanied by side effects. Combining PEG-Ad-TERT/HSVtk with etoposide or 5-fluorouracil enhanced the therapeutic effects with negligible side effects. These results suggest that modification with 20-kDa PEG at a 45% modification ratio is the optimal condition for PEGylation of Adv, and PEG-Ad-TERT/HSVtk is a prototype Adv for systemic cancer gene therapy against metastases.

Direct cell entry of gold/iron-oxide magnetic nanoparticles in adenovirus mediated gene delivery

Gold/iron-oxide MAgnetic Nanoparticles (GoldMAN) imparts useful magnetic properties to various biomolecules. Gold nanoparticles immobilized on the surface of magnetic nanoparticles allow for the conjugation of biomolecules via an Au-S bond. Here, we present a practical application by utilizing GoldMAN and a magnetic field to induce intracellular transduction. This method has great potential for application of the adenovirus gene delivery vector (Ad), widely used for in vitro/in vivo gene transfer, to Ad-resistant cells. We demonstrated that Ad was easily immobilized on GoldMAN and the Ad/GoldMAN complex was introduced into the cell by the magnetic field, which increased gene expression over 1000 times that of Ad alone. The GoldMAN penetrated the plasma membrane directly, independent of the cell-surface virus receptors and endocytosis pathway. This mechanism will contribute to improve the gene expression efficiency of Ad. This technology is a useful tool for extending Ad tropism and enhancing transduction efficiency. GoldMAN also makes possible the effective use of various biomolecules within the cell because of its interesting cell-entry mechanism.

Factors determining the efficacy of nuclear delivery of antisense oligonucleotides by gold nanoparticles

The present study investigates the applicability of nanoparticle delivery vectors for two-stage targeting that involves both cell entry by endocytosis and nuclear targeting using viral peptide signals. A nanoparticle vector consists of four components: a carrier nanoparticle, a stabilizer, targeting peptides, and a therapeutic cargo. Extensive study of bovine serum albumin (BSA)-peptide stabilized nanoparticle conjugates demonstrated limitations of these systems due to colloidal instability when oligonucleotides and multiple peptides were attached to the BSA protein. We found that the widely used protein streptavidin (SA) was an appropriate alternative to BSA for cell-targeting experiments. Targeting peptides and gene splicing oligonucleotides were attached to SA-nanoparticles using biotin labels. The present study uses a gene-splicing assay as a test for oligonucleotide delivery to the cell nucleus. Successful modification of gene splicing by an antisense oligonucleotide indicates that the latter must have crossed the plasma membrane, entered the nucleus, found the target sequence in the newly transcribed pre-mRNA, and hybridized to it in the spliceosome strongly enough to displace the splicing factors designed to interact with the target sequence. Targeting nanoparticles that carry gene-splicing oligonucleotides were compared with a control experiment that used lipofectamine (LF). While enhanced activity was observed in the control experiment, in the presence of LF, no gene splicing was observed for the nanoparticle targeting vectors without LF. We conclude that sequestration of cargo from the harsh conditions of the endosome is a desirable strategy for cell-targeting nanoparticles.

CC-chemokine ligand 17 gene therapy induces tumor regression through augmentation of tumor-infiltrating immune cells in a murine model of preexisting CT26 colon carcinoma

Chemokines, which regulate leukocyte trafficking and infiltration of local sites, are attractive candidates for improving the efficacy of cancer immunotherapy by enhancing the accumulation of immune cells in tumor tissue. Herein, we evaluated the antitumor effects of intratumoral injection of RGD fiber-mutant adenoviral vectors (AdRGDs) encoding the chemokines CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1 or CX3CL1 in a murine model of preexisting CT26 colon carcinoma. Among these 8 chemokine-expressing AdRGDs, injection of AdRGD-CCL17 most effectively induced tumor regression and generated specific immunity in rechallenge experiments. Tumor elimination activity by intratumoral injection of AdRGD-CCL17 depended on both the vector dose and the number of injections, and mainly required CD8+ CTLs in an effector phase as confirmed by analysis using BALB/c nude mice and an in vivo depletion assay. In addition, CCL17 gene transduction induced significant increases in the number of infiltrating macrophages and CD8+ T cells in CT26 tumors, and changed the tumor microenvironment to an immunologic activation state in which there was enhanced expression of lymphocyte activation markers and cell adhesion molecules. Thus, our data provide evidence that CCL17 gene transduction of local tumor sites is a promising approach for the development of a cancer immunogene therapy that can recruit activated tumor-infiltrating immune effector cells.

Evaluation of twenty-one human adenovirus types and one infectivity-enhanced adenovirus for the treatment of malignant melanoma

Advanced melanoma is associated with poor prognosis warranting the development of new therapeutics, such as oncolytic adenoviruses for immunovirotherapy. Since this approach critically depends on efficient transduction of targeted tumor cells, we screened a panel of 22 different adenovirus types for their internalization efficiency in melanoma cells. We demonstrated that the virions of Ad35, Ad38, and Ad3 have significantly higher internalization efficiency in melanoma cells than Ad5, so far the only adenovirus type used in clinical trials for melanoma. Therefore, we developed a conditionally replication-competent Ad5-based vector with the Ad35 fiber shaft and knob domains (Ad5/35) and compared its therapeutic efficacy with the homologous vector carrying the native Ad5 fiber. To further enhance virotherapy, we combined the oncolytic adenovirus vectors with intratumoral expression of measles virus fusogenic membrane glycoproteins H and F (MV-H/F) and dacarbazine chemotherapy. In a human melanoma xenograft model, established from a short-term culture of primary melanoma cells, we demonstrated that the Ad5/35-based therapy had a significantly greater anti-neoplastic effect than the homologous Ad5-based therapy. Furthermore, the combination of virotherapy, intratumoral expression of MV-H/F, and chemotherapy was clearly superior to single- or double-agent therapy. In conclusion, Ad35-based vectors are promising for the treatment of melanoma.

TERT promoter-driven adenovirus vector for cancer gene therapy via systemic injection

Adenovirus vectors (Adv) are used widely in cancer gene therapy research. However, the clinical application of Adv currently is limited to local, intratumoral administration; systemic administration leads to redundant transgene expression in the liver and subsequent hepatotoxicity. Here we replaced the conventional cytomegalovirus (CMV) promoter of Adv with a tumor-specific telomere reverse transcriptase (TERT) promoter, to restrict expression of the Adv-transduced transgene to tumor tissue alone. We evaluated the therapeutic and side effects after systemic administration of Adv expressing herpes simplex virus thymidine kinase (Ad-HSVtk) in mice bearing Meth-A tumors. Although systemically injected CMV promoter-driven Ad-HSVtk lacked therapeutic effect, mice injected with 2x10(11) viral particles containing TERT promoter-driven Ad-HSVtk showed inhibited tumor growth and prolonged survival with minimal side effects. Our results suggest that Adv in which transgene expression is driven by the TERT promoter are a promising prototype of tumor-targeting vectors for effective and safe cancer gene therapy.

Effective tumor targeted gene transfer using PEGylated adenovirus vector via systemic administration

Conjugation of polyethylene glycol to protein or particles (PEGylation) prolongs their plasma half-lives and promotes their accumulation in tumors due to enhanced permeability and retention (EPR) effect. Although PEGylation of adenovirus vectors (Ads) is an attractive strategy to improve the in vivo kinetics of conventional Ads, the EPR effect of PEGylated Ad (PEG-Ad) had not previously been reported. In this study, we prepared PEG-Ads with PEG at various modification ratios, injected them intravenously into tumor-bearing mice, and determined the blood kinetics, viral distribution, and gene expression patterns, respectively. In addition, we conducted a cancer therapeutic study of PEG-Ad encoding tumor necrosis factor (TNF)-alpha. The plasma half-life of PEG-Ad was longer than that of unmodified-Ad, and accumulation of PEG-Ad in tumor tissue increased as the PEG modification ratio increased. In particular, PEG-Ad with about 90% modification ratio showed higher (35 times) gene expression in tumor and lower (6%) in liver, compared with values for unmodified Ad. Moreover, PEG-Ad encoding TNF-alpha demonstrated not only stronger tumor-suppressive activity but also fewer hepatotoxic side effects compared with unmodified-Ad. PEGylation of Ad achieved tumor targeting through the EPR effect, and these attributes suggest that systemic injection of PEG-Ad has great potential as an anti-tumor treatment.

Tumor suppressive efficacy through augmentation of tumor-infiltrating immune cells by intratumoral injection of chemokine-expressing adenoviral vector

Our goal in the present study was to evaluate antitumor effects and frequency of tumor-infiltrating immune cells upon intratumoral injection of RGD fiber-mutant adenoviral vector (AdRGD) encoding the chemokines CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1, and CX3CL1. Among eight kinds of chemokine-expressing AdRGDs, AdRGD-CCL19 injection most efficiently induced infiltration of T cells into established B16BL6 tumor parenchyma, whereas most of these T cells were perforin-negative in immunohistochemical analysis. Additionally, the growth of AdRGD-CCL19-injected tumors decreased only slightly as well as that of other tumors treated with each chemokine-expressing AdRGD, which indicated that accumulation of naive T cells in tumor tissue does not effectively damage the tumor cells. Tumor-bearing mice, in which B16BL6-specific T cells were elicited by dendritic cell-based immunization, demonstrated that intratumoral injection of AdRGD-CCL17, -CCL22, or -CCL27 could considerably suppress tumor growth and attract activated T cells. On the other hand, AdRGD-CCL19-injection in the immunized mice showed slight increase of tumor-infiltrating T cells compared to treatment using control vector. Collectively, although AdRGD-mediated chemokine gene transduction into established tumors would be very useful for augmentation of tumor-infiltrating immune cells, a combinational treatment that can systemically induce tumor-specific effector T cells is necessary for satisfactory antitumor efficacy.

Cotransduction of CCL27 gene can improve the efficacy and safety of IL-12 gene therapy for cancer

Interleukin-12 (IL-12) is a potent antitumoral cytokine, but high doses are toxic. Herein, we demonstrate that combinational transduction of IL-12 and CC-chemokine ligand-27 (CCL27) genes into pre-existing murine OV-HM ovarian carcinoma and Meth-A fibrosarcoma, by using RGD fiber-mutant adenoviral vectors, could induce tumor regression and relieve systemic side effects more effectively than either treatment alone. The antitumor activity of the IL-12 and CCL27 combination treatment was T-cell-dependent, and development of long-term specific immunity was confirmed in rechallenge experiments. Immunohistochemical analysis of tumors transduced with CCL27 gene alone or cotransduced with IL-12 and CCL27 genes showed significant increases in numbers of infiltrating CD3(+) T cells, which included both CD4(+) and CD8(+) cells. Additionally, cotransduction with IL-12 and CCL27 genes could more efficiently activate tumor-infiltrating immune cells than transduction with CCL27 alone, as determined by the frequency of perforin-positive cells and expression levels of IFN-gamma. Furthermore, mice treated with the IL-12 and CCL27 combination compared with those treated with IL-12 alone showed milder pathological changes, for example, lymphocyte infiltration and extramedullary hematopoiesis, in lung, liver and spleen. Our data provide evidence that combinational in vivo transduction with IL-12 and CCL27 genes is a promising approach for the development of cancer immunogene therapy that can simultaneously recruit and activate tumor-infiltrating immune cells.

Gene therapy progress and prospects: the skin – easily accessible, but still far away

Significant progress has been made in corrective gene therapy of inherited skin diseases. This includes advances in vector technology, targeted gene expression, gene replacement, and the availability of appropriate animal models for a variety of candidate diseases. In addition, an increased understanding of the uptake and trafficking mechanisms inside keratinocytes has evolved. Topical application facilitates DNA vaccination through the skin, albeit clinical benefits have not yet materialized. However, the translation into clinical trials has only been partially mastered. The latter and the control of immune responses represent challenges for the research community.

Adenoviral vectors--how to use them in cancer gene therapy?

Gene therapy is most often described as a technique for introducing the foreign genetic material into cells with a correction of a dysfunctional gene as its final goal. Today, it is well known that cancer is one of the leading causes of mortality in the world. Besides classical methods for cancer treatment new strategies against cancer are needed. Although originally being designed as a treatment for monogenetic illness, soon after, gene therapy appeared as a potential new strategy in cancer therapy. One of the widely used vectors for cancer gene therapy is adenovirus. In this review we have described molecular biology of adenoviruses and basis for construction of adenoviral vectors. We have also described concepts for cancer gene therapy including their in vitro and in vivo application. Special attention is drawn toward retargeting of adenovirus as a new approach in vector design for cancer gene therapy, in order to restrict transgene expression in tumor tissue. This approach uses biophysical as well as genetic characteristics of tumor itself and its supporting tissue, allowing new "bypass" in cancer gene therapy.

Cell Delivery System: A Novel Strategy to Improve the Efficacy of Cancer Immunotherapy by Manipulation of Immune Cell Trafficking and Biodistribution

Tumor cells that generally accumulate mutations in the genome express molecules different both qualitatively and quantitatively from normal cells. An immunosurveillance system for these molecules, known as the tumor-associated antigens (TAAs), plays an important role in the elimination of cancer cells during the initial stage. Although cancer immunotherapy targeting TAAs has progressed steadily with the development of various vaccine strategies, satisfactory efficacy, such as marked tumor regression and complete response, has not been previously reported in a clinical setting. To improve the therapeutic effects of cancer immunotherapy, the application of chemokine-chemokine receptor coupling, which controls the trafficking and biodistribution of immune cells in the living body, is an attractive potential approach. This review introduces our novel "cell delivery system," which employs an Arg-Gly-Asp (RGD) fiber-mutant adenovirus vector encoding the chemokine or chemokine receptor gene in cancer immunotherapy.