A novel gene expression system strongly enhances the anticancer effects of a REIC/Dkk-3-encoding adenoviral vector

Enhanced design of pCMViR-TSC plasmid vector for sustainably high cargo gene expression in mammalian cells

The first-generation pCMViR-TSC, implemented through the promoter sandwich rule, yields 10- to 100-fold higher gene expression than the standard plasmid used with the CMV (cytomegalovirus) or CAG promoter. However, the vector's shortcomings limit its utility to transient expression only, as it is not suitable for establishing stable transformants in mammalian cells. To overcome this weakness, we here introduce the improved plasmid vector pSAKA-4B, derived from pCMViR-TSC as a second-generation chromosome-insertable vector. This vector facilitates the linear entry of the expression unit into the TTAA site of DNA universally with transposase assistance. The vector is helpful for the indefinite expression of our target gene. The new vector system is proven here to be efficient in establishing stable transformants with a high likelihood of positive clones that exhibit significantly elevated expression levels of the delivered foreign gene. This system, alongside the first-generation vector, is therefore instrumental for diverse basic research endeavors concerning genes, proteins, cells, and animals, and potentially for clinical applications such as gene therapy.

Molecular design of controllable recombinant adeno-associated virus (AAV) expression systems for enhanced vector production

Recombinant adeno-associated virus (rAAV) is the leading vector for the delivery of gene therapies. However, low viral genome (VG) titers are common and the proportion of "full" capsids containing the therapeutic gene payload can be highly variable. The coordinated molecular design of plasmids encoding viral components and Helper functions remains a major challenge for rAAV manufacturing. Here we present the design of improved Rep/Cap and Helper plasmids for rAAV2/8 production, (i) a Rep/Cap expression vector harboring independently controllable rep and cap genes and (ii) an improved Helper plasmid harboring E4 gene deletion variants. First, an optimized Rep/Cap vector utilized a truncated p5 promoter, a p5 cis-regulatory element at the 3' end in combination with a heterologous promoter to drive Cap expression and an additional copy of the rep52/40 gene to overexpress short Rep proteins. We demonstrate that Rep78 is essential for efficient rAAV2/8 production in HEK293 cells, and a higher ratio of short Rep to long Rep proteins enhances genome packaging. Second, we identified regulators and open reading frames within the Helper plasmid that contribute to increased rAAV2/8 production. While L4-33k/22k is integral to optimal production, the use of E4orf6-6/7 subset significantly enhanced VG titer. Together, an optimal combination of engineered Rep/Cap and Helper plasmid variants increased VG titer by 3.1-fold. This study demonstrates that configuring and controlling the expression of the different AAV genetic elements contributes toward high rAAV production and product quality (full/empty capsid ratio).

Suitable Promoter for DNA Vaccination Using a pDNA Ternary Complex

In this study, we evaluated the effect of several promoters on the transfection activity and immune-induction efficiency of a plasmid DNA (pDNA)/polyethylenimine/γ-polyglutamic acid complex (pDNA ternary complex). Model pDNAs encoding firefly luciferase (Luc) were constructed with several promoters, such as simian virus 40 (SV40), eukaryotic elongation factor 1 alpha (EF1), cytomegalovirus (CMV), and chicken beta actin hybrid (CBh) (pSV40-Luc, pEF1-Luc, pCMV-Luc, and pCBh-Luc, respectively). Four types of pDNA ternary complexes, each with approximately 145-nm particle size and -30-mV ζ-potential, were stably constructed. The pDNA ternary complex containing pSV40-Luc showed low gene expression, but the other complexes containing pEF1-Luc, pCMV-Luc, and pCBh-Luc showed high gene expression in DC2.4 cells and spleen after intravenous administration. After immunization using various pDNA encoding ovalbumin (OVA) such as pEF1-OVA, pCMV-OVA, and pCBh-OVA, only the pDNA ternary complex containing pCBh-OVA showed significant anti-OVA immunoglobulin G (IgG) induction. In conclusion, our results showed that the CBh promoter is potentially suitable for use in pDNA ternary complex-based DNA vaccination.

PD-1 blockade augments CD8+ T cell dependent antitumor immunity triggered by Ad-SGE-REIC in Egfr-mutant lung cancer

OBJECTIVES

No immunotherapeutic protocol has yet been established in never-smoking patients with lung cancer harboring driver oncogenic mutations, such as epidermal growth factor receptor (EGFR) mutations. The immunostimulatory effect of Ad-REIC, a genetically engineered adenovirus vector expressing a tumor suppressor gene, reduced expression in immortalized cells (REIC), has been investigated in clinical trials for various solid tumors. However, the immunostimulatory effect of the Ad-REIC in EGFR-mutant lung cancer with a non-inflamed tumor microenvironment (TME) has not been explored.

MATERIALS AND METHODS

We used a syngeneic mouse model developed by transplanting Egfr-mutant lung cancer cells into single or double flanks of C57BL/6J mice. Ad-SGE-REIC, a 2nd-generation vector with an enhancer sequence, was injected only into the tumors from one flank, and its antitumor effects were assessed. Tumor-infiltrating cells were evaluated using immunohistochemistry or flow cytometry. The synergistic effects of Ad-SGE-REIC and PD-1 blockade were also examined.

RESULTS

Injection of Ad-SGE-REIC into one side of the tumor induced not only a local antitumor effect but also a bystander abscopal effect in the non-injected tumor, located on the other flank. The number of PD-1⁺CD8⁺ T cells increased in both injected and non-injected tumors. PD-1 blockade augmented the local and abscopal antitumor effects of Ad-SGE-REIC by increasing the number of CD8⁺ T cells in the TME of Egfr-mutant tumors. Depletion of CD8⁺ cells reverted the antitumor effect, suggesting they contribute to antitumor immunity.

CONCLUSION

Ad-SGE-REIC induced systemic antitumor immunity by modifying the TME status from non-inflamed to inflamed, with infiltration of CD8⁺ T cells. Additionally, in Egfr-mutant lung cancer, this effect was enhanced by PD-1 blockade. These findings pave the way to establish a novel combined immunotherapy strategy with Ad-SGE-REIC and anti-PD-1 antibody for lung cancer with a non-inflamed TME.

Combination of Ad-SGE-REIC and bevacizumab modulates glioma progression by suppressing tumor invasion and angiogenesis

Reduced expression in immortalized cells/Dickkopf-3 (REIC/Dkk-3) is a tumor suppressor and its overexpression has been shown to exert anti-tumor effects as a therapeutic target gene in many human cancers. Recently, we demonstrated the anti-glioma effects of an adenoviral vector carrying REIC/Dkk-3 with the super gene expression system (Ad-SGE-REIC). Anti-vascular endothelial growth factor treatments such as bevacizumab have demonstrated convincing therapeutic advantage in patients with glioblastoma. However, bevacizumab did not improve overall survival in patients with newly diagnosed glioblastoma. In this study, we examined the effects of Ad-SGE-REIC on glioma treated with bevacizumab. Ad-SGE-REIC treatment resulted in a significant reduction in the number of invasion cells treated with bevacizumab. Western blot analyses revealed the increased expression of several endoplasmic reticulum stress markers in cells treated with both bevacizumab and Ad-SGE-REIC, as well as decreased β-catenin protein levels. In malignant glioma mouse models, overall survival was extended in the combination therapy group. These results suggest that the combination therapy of Ad-SGE-REIC and bevacizumab exerts anti-glioma effects by suppressing the angiogenesis and invasion of tumors. Combined Ad-SGE-REIC and bevacizumab might be a promising strategy for the treatment of malignant glioma.

Tumor suppressor REIC/Dkk-3 and its interacting protein SGTA inhibit glucocorticoid receptor to nuclear transport

REIC/Dkk-3 is a tumor suppressor, and its expression is significantly downregulated in a variety of human cancer types. A previous study performed yeast two-hybrid screening and identified the small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA), known as a negative modulator of cytoplasmic androgen receptor (AR) signaling, which is a novel interacting partner of REIC/Dkk-3. The previous study also indicated that the REIC/Dkk-3 protein interferes with the dimerization of SGTA and then upregulates the AR transport and signaling in human prostate cancer PC3 cells. Since the transport of some steroid receptors to nucleus is conducted similarly by dynein motor-dependent way, the current study aimed to investigate the role of SGTA and REIC/Dkk-3 in the transport of other glucocorticoid receptors (GR). In vitro reporter assays for the cytoplasmic GR transport were performed in human prostate cancer PC3 cells and 293T cells. As for the SGTA protein, a suppressive effect on the GR transport to the nucleus was observed in the cells. As for the REIC/Dkk-3 protein, an inhibitory effect was observed for the GR transport in PC3 cells. Under the depleted condition of SGTA by short-hairpin (sh)RNA, the downregulation of GR transport by REIC/Dkk-3 was significantly enhanced compared with the non-depleted condition in PC3 cells, suggesting a compensatory role of REIC/Dkk-3 in the SGTA mediated inhibition of GR transport. The current study therefore demonstrated that SGTA inhibited the cytoplasmic transport of GR in 293T and PC3 cells, and REIC/Dkk-3 also inhibited the cytoplasmic transport of GR in PC3 cells. These results may be used to gain novel insight into the GR transport and signaling in normal and cancer cells.

MiR-425 Promotes Migration and Invasion in Bladder Cancer by Targeting Dickkopf 3

Background: Bladder cancer (BC) is a common malignancy with high morbidity and mortality. MicroRNAs (miRNAs) are critical post-transcriptional regulators in various cancers. This study aimed to investigate the effect of miR-425 on the migration and invasion of BC.

Methods: The expression of miR-425 and Dickkopf 3 (DKK3) was examined in clinical BC specimens. T24 and 5637 BC cell lines were employed and transfected with miR-425 inhibitors. The correlation between miR-425 and DKK3 was determined by a luciferase reporter assay. Cell migration and invasion capacity were measured by wound healing and Transwell assays. The expression levels of DKK3, E-cadherin, N-cadherin and vimentin were analysed by Western blotting and qRT-PCR.

Results: miR-425 was negatively correlated with the expression of DKK3 in clinical BC specimens. Further studies identified DKK-3 as a direct target of miR-425. Moreover, knockdown of miR-425 promoted the expression of DKK3 and suppressed cell migration and invasion capacity. miR-425 silencing increased E-cadherin levels but decreased vimentin and N-cadherin protein levels in T24 and 5637 cells.

Conclusion: Our study indicated that miR-425 promoted the migration and invasion of BC via targeting DKK3.

Study protocol of a Phase I/IIa clinical trial of Ad-SGE-REIC for treatment of recurrent malignant glioma

Malignant glioma is one of the most common brain cancers in humans, which is very devastating. The expression of reduced expression in immortalized cells/Dickkopf-3 (REIC/Dkk-3) is decreased in various human cancers. Lately, we have developed a novel second-generation adenoviral vector that expresses REIC/Dkk-3 (Ad-SGE-REIC) and revealed its antiglioma efficacy. The present investigator-initiated clinical trial is a single-arm, prospective, nonrandomized, noncomparative, open-label, single-center trial performed at Okayama University Hospital, Okayama, Japan. The primary end points are dose-limiting toxicities and the incidence of adverse events. The secondary end points are the objective response rate and immunological assessment. Use of Ad-SGE-REIC will help to improve the prognosis of patients with malignant brain tumors.

Regulatory elements in vectors containing the ctEF-1α first intron and double enhancers for an efficient recombinant protein expression system

To establish a stable and scalable transient protein production system, we modified the EF-1 first intron size and verified the order of two recombinant enhancers downstream of the SV40 polyA sequence. This new vector was named pHH-Gemini (pHH-GM1) and was used to express alpha kinase 1 (ALPK1) and various other proteins, NLRP3, F-actin, Camodulin, PP2A, URAT1, Rab11a and myosin IIA. The results showed that, compared with six commercial plasmids, pHH-GM1 significantly enhanced His-HA-ALPK1 expression in a western blot analysis of transfected HEK293T cells. The expression of various other genes was also successful using the pHH-GM1 vector. In addition, we inserted turbo green florescence protein (tGFP) into the pHH-GM1 vector, and an improvement in fluorescence intensity was observed after transient transfection of HEK293T cells. For large-scale production, protein production was tested by standard supplementation with one volume of medium, and volumetric yields of 2 and 2.3 mg/L were achieved with pHH-GM1-ALPK1 in HEK293-F and CHO-S cells, respectively. We found that cell viability was more than 70% 11 days after cells were transfected with the pHH-GM1 vector. The pHH-GM1 vector with the ctEF-1α first intron and double enhancers, Simian virus 40 and Cytomegalovirus (SV40 and CMV) is an efficient CMV promoter-based gene expression system that can potentially be applied to study genes of interest and improve protein production.

Promising therapeutic efficacy of a novel reduced expression in immortalized cells/dickkopf-3 expressing adenoviral vector for hepatocellular carcinoma

BACKGROUND AND AIM

Reduced expression in immortalized cells (REIC)/dickkopf-3 (Dkk-3) is a tumor suppressor gene that is downregulated in various cancers. In our previous study of prostate cancer, the REIC/Dkk-3-expressing adenoviral vector (Ad-REIC) was found to induce cancer-selective apoptosis. This study recently developed a novel super gene expression (SGE) system and used this system to re-construct an Ad-REIC vector, termed the Ad-SGE-REIC, to achieve more effective therapeutic outcomes. In this study, the therapeutic effects of Ad-SGE-REIC on hepatocellular carcinoma (HCC) was assessed.

METHODS

Human HCC cell lines (HLE, Huh7, HepG2, HLF, SK-Hep1, and PLC), human HCC tissues, and mouse HCC cell line (Hepa1-6) were used in this study. REIC/Dkk-3 expression was assessed by immunoblotting and immunohistochemistry. The relative cell viability and the apoptotic effect were examined in vitro, and the anti-tumor effects of Ad-SGE-REIC treatment were analyzed in the mouse xenograft model. This study additionally assessed anti-tumor immunological effects on the immunocompetent mice.

RESULTS

REIC/Dkk-3 expression was decreased in HCC cell lines and HCC tissues. Ad-SGE-REIC reduced cell viability and induced apoptosis in HCC cell lines (HLE and Huh7), inhibited tumor growth in the mouse xenograft model, and demonstrated in vivo anti-cancer immunostimulatory effects on the HCC cell line (Hepa1-6).

CONCLUSIONS

Ad-SGE-REIC treatment not only enhanced cell killing effects in vitro but also elicited significant therapeutic effects, with tumor growth suppression, in vivo. REIC/Dkk-3 gene therapy using Ad-SGE-REIC potentially represents an innovative new therapeutic tool for HCC.

Expression of tumor suppressor REIC/Dkk-3 by a newly improved adenovirus vector with insertion of a hTERT promoter at the 3'-side of the transgene

Reduced expression in immortalized cells (REIC)/Dickkopf-3 (Dkk-3) overexpression, induced using an adenovirus (Ad)-REIC, has been revealed to have a dramatic therapeutic effect on multiple types of cancer. To achieve an improved therapeutic effect from Ad-REIC on cancer, our group previously developed an enhanced gene expression system, the C-TSC cassette [cytomegalovirus (CMV)-RU5' located upstream (C); another promoter unit composed of triple tandem promoters, human telomerase reverse transcriptase (hTERT), simian virus 40 and CMV, located downstream of the cDNA (TSC); plus a polyadenylation (polyA) signal]. When applied to the conventional Ad-REIC, this novel system induced the development of an enhanced product, Ad-C-TSC-REIC, which exhibited a noticeable anticancer effect. However, there were difficulties in terms of Ad-C-TSC-REIC productivity in HEK293 cells, which are a widely used donor cell line for viral production. Productivity of Ad-C-TSC-REIC was significantly reduced compared with the conventional Ad-REIC, as the Ad-C-TSC-REIC had a significantly higher ability to induce apoptotic cell death of not only various types of cancer cell, but also HEK293 cells. The present study aimed to overcome this problem by modifying the C-TSC structure, resulting in an improved candidate: A C-T cassette (C: CMV-RU5' located upstream; T: another promoter unit composed of a single hTERT promoter, located downstream of the cDNA plus a polyA signal), which demonstrated gene expression comparable to that of the C-TSC system. The improved adenovirus REIC/Dkk-3 product with the C-T cassette, named Ad-C-T-REIC, exhibited a higher expression level of REIC/Dkk3, similar to that of Ad-C-TSC-REIC. Notably, the vector mitigated the cell death of donor HEK293 cells, resulting in a higher rate of production of its adenovirus. These results indicated that Ad-C-T-REIC has the potential to be a useful tool for application in cancer gene therapy.

Overexpression of REIC/Dkk-3 suppresses the expression of CD147 and inhibits the proliferation of human bladder cancer cells

Our group previously developed an adenoviral vector encoding the REIC/Dkk-3 gene (Ad-REIC), a tumor suppressor, for cancer gene therapy. The Ad-REIC agent induces apoptosis and inhibits invasion in a number of cancer cell lines; however, the molecular mechanisms underlying its effects remain unclear. Cluster of differentiation 147 (CD147), also known as extracellular matrix metalloproteinase inducer (EMMPRIN), is a key molecule that promotes cancer proliferation and invasion. In order to elucidate the therapeutic mechanism of Ad-REIC, its effect on the expression of CD147 in human bladder cancer KK47 cells was investigated. Treatment with Ad-REIC markedly downregulated the expression of CD147 and significantly inhibited cellular proliferation. Since the expression of CD147 is reported to be under the positive control of mitogen-activated protein kinase (MAPK) signaling and the c-Myc protein, the correlations between the expression of CD147 and the activation of MAPKs or the expression of c-Myc were examined. Unexpectedly, no positive correlation was observed between the level of CD147 and the potential regulators that were assessed, indicating that another signaling pathway is responsible for the downregulation of CD147. The results from the present study demonstrate that Ad-REIC treatment can significantly downregulate the expression of CD147 in bladder cancer cells. Downregulation of the cancer-progression factor CD147 may be a novel mechanism that underlies the therapeutic effects of Ad-REIC treatment.

Robust cancer-specific gene expression by a novel cassette with hTERT and CMV promoter elements

We developed and validated a novel hTERT/CMV promoter element-driven gene expression cassette that can robustly enhance cancer-specific gene expression. The following gene expressional elements were located in tandem within the plasmid construct: [hTERT core promoter, cytomegalovirus (CMV) minimized promoter, RU5' sequence, an inserted gene, BGH polyA, hTERT enhancer]; this is hereafter referred to as the hT/Cm-R-hT construct. Using various human cancer cell lines and normal cells, the cancer-specific transcription of the green fluorescent protein (GFP) gene was examined by western blotting and fluorescence microscopy. Cancer-specific gene expression was robustly achieved in the hT/Cm-R-hT plasmid in comparison to the other control hT/Cm-driven construct. Notably, the expression level of GFP observed in the hT/Cm-R-hT-driven construct was superior to that of the control plasmid with the conventional CMV promoter in HEK293 cells, which are known to possess higher hTERT activity than normal cells. We next examined the availability of hT/Cm-R-hT in detecting the target GFP expressing cancer cells from human peripheral blood mononuclear cells (PBMCs). The hT/Cm-R-hT plasmid successfully induced cancer-specific gene expression; the robust expression of GFP was observed in target HeLa cancer cells, whereas GFP was not visibly expressed in normal PBMCs. The plasmid allowed for the selective visualization of viable HeLa cancer cells in mixed cell cultures containing up to 10000-fold more PBMCs. These findings indicate that the hT/Cm-R-hT expressional system is a valuable tool for detecting viable cancer cells mixed with normal cells. The current system can therefore be applied to the in vitro detection of cancer cells that are disseminated in the blood and other types of body fluid in vivo. Since the current system can also be applied to other types of vectors, including virus vectors, this approach using the hTERT promoter-based construct is expected to become a valuable tool for enhancing cancer-specific gene expression.

Canine REIC/Dkk-3 interacts with SGTA and restores androgen receptor signalling in androgen-independent prostate cancer cell lines

Background

The pathological condition of canine prostate cancer resembles that of human androgen-independent prostate cancer. Both canine and human androgen receptor (AR) signalling are inhibited by overexpression of the dimerized co-chaperone small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA), which is considered to cause the development of androgen-independency. Reduced expression in immortalised cells (REIC/Dkk-3) interferes with SGTA dimerization and rescues AR signalling. This study aimed to assess the effects of REIC/Dkk-3 and SGTA interactions on AR signalling in the canine androgen-independent prostate cancer cell line CHP-1.

Results

Mammalian two-hybrid and Halo-tagged pull-down assays showed that canine REIC/Dkk-3 interacted with SGTA and interfered with SGTA dimerization. Additionally, reporter assays revealed that canine REIC/Dkk-3 restored AR signalling in both human and canine androgen-independent prostate cancer cells. Therefore, we confirmed the interaction between canine SGTA and REIC/Dkk-3, as well as their role in AR signalling.

Conclusions

Our results suggest that this interaction might contribute to the development of a novel strategy for androgen-independent prostate cancer treatment. Moreover, we established the canine androgen-independent prostate cancer model as a suitable animal model for the study of this type of treatment-refractory human cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1094-4) contains supplementary material, which is available to authorized users.

Tumor suppressor REIC/DKK-3 and co-chaperone SGTA: Their interaction and roles in the androgen sensitivity

REIC/DKK-3 is a tumor suppressor, however, its intracellular physiological functions and interacting molecules have not been fully clarified. Using yeast two-hybrid screening, we found that small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA), known as a negative modulator of cytoplasmic androgen receptor (AR) signaling, is a novel interacting partner of REIC/DKK-3. Mammalian two-hybrid and pull-down assay results indicated that the SGTA-REIC/DKK-3 interaction involved the N-terminal regions of both REIC/DKK-3 and SGTA and that REIC/DKK-3 interfered with the dimerization of SGTA, which is a component of the AR complex and a suppressor of dynein motor-dependent AR transport and signaling. A reporter assay in human prostate cancer cells that displayed suppressed AR signaling by SGTA showed recovery of AR signaling by REIC/DKK-3 expression. Considering these results and our previous data that REIC/DKK-3 interacts with the dynein light chain TCTEX-1, we propose that the REIC/DKK-3 protein interferes with SGTA dimerization, promotes dynein-dependent AR transport and then upregulates AR signaling.

Adenovirus vector carrying REIC/DKK-3 gene: neoadjuvant intraprostatic injection for high-risk localized prostate cancer undergoing radical prostatectomy

As the First-In-Human study of in situ gene therapy using an adenovirus vector carrying the human REIC (reduced expression in immortalized cell)/Dkk-3 gene (Ad-REIC), we conducted neoadjuvant intraprostatic injections in patients with high-risk localized prostate cancer undergoing radical prostatectomy (RP). Patients with recurrence probability of 35% or more within 5 years following RP, as calculated by Kattan's nomogram, were enrolled. Patients received two ultrasound-guided intratumoral injections at 2-week intervals, followed by RP 6 weeks after the second injection. After confirming the safety of the therapeutic interventions with initially planned three escalating doses of 1.0 × 10¹⁰, 1.0 × 10¹¹ and 1.0 × 10¹² viral particles (vp) in 1.0-1.2 ml (n=3, 3 and 6), an additional higher dose of 3.0 × 10¹² vp in 3.6 ml (n=6) was further studied. All four DLs including the additional dose level-4 (DL-4) were feasible with no adverse events, except for grade 1 or 2 transient fever. Laboratory toxicities were grade 1 or 2 elevated aspartate transaminase/alanine transaminase (n=4). Regarding antitumor activities, cytopathic effects (tumor degeneration with cytolysis and pyknosis) and remarkable tumor-infiltrating lymphocytes in the targeted tumor areas were detected in a clear dose-dependent manner. Consequently, biochemical recurrence-free survival in DL-4 was significantly more favorable than in patient groups DL-1+2+3.

A super gene expression system enhances the anti-glioma effects of adenovirus-mediated REIC/Dkk-3 gene therapy

Reduced expression in immortalized cells/Dickkopf-3 (REIC/Dkk-3) is a tumor suppressor and therapeutic gene in many human cancers. Recently, an adenovirus REIC vector with the super gene expression system (Ad-SGE-REIC) was developed to increase REIC/Dkk-3 expression and enhance therapeutic effects compared with the conventional adenoviral vector (Ad-CAG-REIC). In this study, we investigated the in vitro and in vivo effects of Ad-SGE-REIC on malignant glioma. In U87ΔEGFR and GL261 glioma cells, western blotting confirmed that robust upregulation of REIC/Dkk-3 expression occurred in Ad-SGE-REIC-transduced cells, most notably after transduction at a multiplicity of infection of 10. Cytotoxicity assays showed that Ad-SGE-REIC resulted in a time-dependent and significant reduction in the number of malignant glioma cells attaching to the bottom of culture wells. Xenograft and syngeneic mouse intracranial glioma models treated with Ad-SGE-REIC had significantly longer survival than those treated with the control vector Ad-LacZ or with Ad-CAG-REIC. This study demonstrated the anti-glioma effect of Ad-SGE-REIC, which may represent a promising strategy for the treatment of malignant glioma.

Novel REIC/Dkk-3-encoding adenoviral vector as a promising therapeutic agent for pancreatic cancer

Reduced expression in immortalized cells (REIC)/dickkopf-3 (Dkk-3), a tumor suppressor gene, is downregulated in various cancers. We previously reported the tumor-inhibitory effects of the REIC/Dkk-3 gene, delivered by a conventional adenoviral vector (Ad-CAG-REIC) in pancreatic cancer. Here, we developed an Ad-REIC vector with a novel gene expression system, termed the super gene expression (SGE) system, and assessed its therapeutic effects relative to those of Ad-CAG-REIC in pancreatic cancer cells. Human pancreatic cancer cell lines ASPC1 and MIAPaCa2 were used. REIC/Dkk-3 expression was assessed by western blot analysis. Relative cell viability and apoptotic effects were examined in vitro. The anti-tumor effects of Ad-REIC treatment were assessed in the mouse xenograft model. Compared with Ad-CAG-REIC, Ad-SGE-REIC elicited a significant increase in REIC protein expression in the cells studied. Relative to Ad-CAG-REIC, Ad-SGE-REIC reduced cell viability and induced apoptosis in the ASPC1 and MIAPaCa2 cell lines in vitro, and achieved superior tumor growth inhibition in the mouse xenograft model. Compared with conventional Ad-REIC agents, Ad-SGE-REIC provided enhanced inhibitory effects against tumor growth. Our results indicate that Ad-SGE-REIC is an innovative therapeutic tool for pancreatic cancer.

A novel in situ permeation system and its utility in cancer tissue ablation

Focal ablation therapy is an emerging treatment modality for localized cancer lesions. It is an attractive strategy for inhibiting tumor progression and preventing morbidity associated with open surgery. As for intratissue drug delivery systems for use in local therapy, the convection-enhanced delivery (CED) of liquid drugs has been utilized, particularly for the treatment of malignant brain tumors. Although the conventional CED system is useful for providing drug/vehicle-based local therapy, there are several reported disadvantages in terms of the ability to control the extent of drug diffusion. We herein developed and validated a novel in situ permeation (ISP)-MW-1 system for achieving intratissue drug diffusion. The ISP system includes a perfusion catheter connected to an injector and aspirator, which enables intratissue perfusion of the solute diluted in the vehicle in the tip-inserted cavity. We subsequently evaluated the utility of the ISP-MW-1 system for in situ permeation in a subcutaneous tumor model in hamsters. Dehydrated ethanol, saline and 50% acetic acid were evaluated as the vehicle, and methylene blue was used as a dissolved substance for evaluating the diffusion of the agent. As a result, almost all of the tumor tissue within the capsule (tumor size: ~3 cm) was permeated with the dehydrated ethanol and 50% acetic acid and partially with the saline. We further demonstrated that ISP treatment with 50% acetic acid completely ablated the subcutaneous tumors in all of the treated hamsters (n=3). Therefore, the ISP-MW-1 system is a promising approach for controlling the intratissue diffusion of therapeutic agents and for providing local ablation therapy for cancer lesions. We believe that this system may be applicable to a broad range of medicinal and industrial fields, such as regenerative medicine, drug delivery systems, biochemistry and material technologies as well as cancer therapy.

Killing of cancer cells through the use of eukaryotic expression vectors harbouring genes encoding nucleases and ribonuclease inhibitor

Cancer gene therapy vectors are promising tools for killing cancer cells with the purpose of eradicating malignant tumours entirely. Different delivery methods of vectors into the cancer cells, including both non-viral and viral, as well as promoters for the targeted expression of genes encoding anticancer proteins were developed for effective and selective killing of cancer cells without harming healthy cells. Many vectors have been created to kill cancer cells, and some vectors suppress malignant tumours with high efficiency. This review is focused on vectors bearing genes for nucleases such as deoxyribonucleases (caspase-activated DNase, deoxyribonuclease I-like 3, endonuclease G) and ribonucleases (human polynucleotide phosphorylase, ribonuclease L, α-sarcin, barnase), as well as vectors harbouring gene encoding ribonuclease inhibitor. The data concerning the functionality and the efficacy of such vectors are presented.

The cysteine-rich core domain of REIC/Dkk-3 is critical for its effect on monocyte differentiation and tumor regression

Reduced expression in immortalized cells (REIC)/Dickkopf (Dkk)-3 is a tumor-suppressor gene and has been studied as a promising therapeutic gene for cancer gene therapy. Intratumoral injection of an adenovirus vector carrying the human REIC/Dkk-3 gene (Ad-REIC) elicits cancer cell-specific apoptosis and anticancer immune responses. The cytokine-like effect of secretory REIC/Dkk-3 on the induction of dendritic cell (DC)-like cell differentiation from monocytes plays a role in systemic anticancer immunity. In the present study, we generated recombinant full-length and N-terminally truncated REIC/Dkk-3 to characterize the biological activity of the protein. During the purification procedure, we identified a 17 kDa cysteine-rich stable product (C17-REIC) showing limited degradation. Further analysis showed that the C17-REIC domain was sufficient for the induction of DC-like cell differentiation from monocytes. Concomitant with the differentiation of DCs, the REIC/Dkk-3 protein induced the phosphorylation of glycogen synthase kinase 3β (GSK-3β) and signal transducers and activators of transcription (STAT) at a level comparable to that of granulocyte/macrophage colony-stimulating factor. In a mouse model of subcutaneous renal adenocarcinoma, intraperitoneal injection of full-length and C17-REIC proteins exerted anticancer effects in parallel with the activation of immunocompetent cells such as DCs and cytotoxic T lymphocytes in peripheral blood. Taken together, our results indicate that the stable cysteine-rich core region of REIC/Dkk-3 is responsible for the induction of anticancer immune responses. Because REIC/Dkk-3 is a naturally circulating serum protein, the upregulation REIC/Dkk-3 protein expression could be a promising option for cancer therapy.

Ad-REIC Gene Therapy: Promising Results in a Patient with Metastatic CRPC Following Chemotherapy

A 63-year-old man with metastatic castration-resistant prostate cancer (CRPC) was successfully treated for two years with in situ gene therapy using an adenovirus vector carrying the human REIC/Dkk-3 gene (Ad-REIC), following chemotherapy. Ad-REIC mediates simultaneous induction of cancer-selective apoptosis and augmentation of antitumor immunity, and a Phase I/IIa clinical study on Ad-REIC has been conducted at Okayama University Hospital since January 2011. At the time of enrollment in December 2012, the patient presented with rapid progression of lymph node (LN) metastases. Two scheduled Ad-REIC injections and 10 additional Ad-REIC injections into metastatic pelvic and para-aortic LNs under CT guidance, with an average four weeks' interval, exhibited the potent direct and indirect effects of Ad-REIC as a therapeutic cancer vaccine. During the next 12 months, three additional injections into para-aortic LNs showing regrowth achieved adequate control of all metastatic LNs with prostate-specific antigen (PSA) decline, without any particular adverse events.

A vaccine strategy with multiple prostatic acid phosphatase-fused cytokines for prostate cancer treatment

Immunotherapy is one of the attractive treatment strategies for advanced prostate cancer. The US Food and Drug Administration (FDA) previously approved the therapeutic vaccine, sipuleucel-T, which is composed of autologous antigen-presenting cells cultured with a fusion protein [prostatic acid phosphatase (PAP) and granulocyte-macrophage colony-stimulating factor (GMCSF)]. Although sipuleucel-T has been shown to prolong the median survival of patients for 4.1 months, more robust therapeutic effects may be expected by modifying the vaccination protocol. In the present study, we aimed to develop and validate a novel vaccination strategy using multiple PAP-fused cytokines for prostate cancer treatment. Using a super gene expression (SGE) system that we previously established to amplify the production of a recombinant protein, significant amounts of PAP-fused cytokines [human GMCSF, interleukin-2 (IL2), IL4, IL7 and mouse GMCSF and IL4] were obtained. We examined the activity of the fusion proteins in vitro to validate their cytokine functions. A significant upregulation of dendritic cell differentiation from monocytes was achieved by PAP-GMCSF when used with the other PAP-fused cytokines. The PAP-fused human IL2 significantly increased the proliferation of lymphocytes, as determined by flow cytometry. We also investigated the in vivo therapeutic effects of multiple PAP-fused cytokines in a mouse prostate cancer model bearing prostate-specific antigen (PSA)- and PAP-expressing tumors. The simultaneous intraperitoneal administration of PAP-GMCSF, -IL2, -IL4 and -IL7 significantly prevented tumor induction and inhibited the tumor growth in the PAP-expressing tumors, yet not in the PSA-expressing tumors. The in vivo therapeutic effects with the multiple PAP-fused cytokines were superior to the effects of PAP-GMCSF alone. We thus demonstrated the advantages of the combined use of multiple PAP-fused cytokines including PAP-GMCSF, and propose a promising prostatic antigen-vaccination strategy to enhance the therapeutic effects.

Molecular-genetic imaging of cancer

Molecular-genetic imaging of cancer using nonviral delivery systems has great potential for clinical application as a safe, efficient, noninvasive tool for visualization of various cellular processes including detection of cancer, and its attendant metastases. In recent years, significant effort has been expended in overcoming technical hurdles to enable clinical adoption of molecular-genetic imaging. This chapter will provide an introduction to the components of molecular-genetic imaging and recent advances on each component leading to safe, efficient clinical applications for detecting cancer. Combination with therapy, namely, generating molecular-genetic theranostic constructs, will provide further impetus for clinical translation of this promising technology.