Generation of Fiber-Mutant Recombinant Adenoviruses for Gene Therapy of Malignant Glioma

Pretreatment tumor-related leukocytosis misleads positron emission tomography-computed tomography during lymph node staging in gynecological malignancies

The accuracy of fluorine-18-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG-PET/CT) can be influenced by the increased glycolytic activity of inflammatory lesions. Here, using clinical data obtained from gynecological cancer patients, tumor samples and animal models, we investigate the impact of pretreatment tumor-related leukocytosis (TRL) on the diagnostic performance of 18F-FDG-PET/CT in detecting pelvic and paraaortic lymph node metastasis. We demonstrate that pretreatment TRL misleads 18F-FDG-PET/CT during lymph node staging in gynecological malignancies. In the mechanistic investigations, we show that the false-positive 18F-FDG-PET/CT result for detecting nodal metastasis can be reproduced in animal models of TRL-positive cancer bearing G-CSF expressing cervical cancer cells. We also show that increased 18F-FDG uptake in non-metastatic nodes can be explained by the MDSC-mediated premetastatic niche formation in which proinflammatory factors, such as S100A8 or S100A9, are abundantly expressed. Together, our results suggest that the MDSC-mediated premetastatic niche created in the lymph node of TRL-positive patients misleads 18F-FDG-PET/CT for detecting nodal metastasis.

[Gene engineering of the adenovirus vector]

The adenovirus vector is very attractive tool not only for the gene therapy but also for the basic sciences. However, because a construction method of this vector had been complex, only limited scientists had constructed and enjoyed the benefits. Recently, various methods were developed and the researchers came to be able to choose an efficient method, which is the COS-TPC method, or a concise procedure, which is the intact-genome transfection method (in vitro ligation method). Here we described not only these methods but also new method to construct the various Ads simultaneously using the recombinase-mediated cassette exchange (RMCE) by the site-specific recombinase. And also we want to refer the possibility to the worth of the vector, especially the vector of the expression-switch.

Delivery of viral vectors to tumor cells: extracellular transport, systemic distribution, and strategies for improvement

It is a challenge to deliver therapeutic genes to tumor cells using viral vectors because (i) the size of these vectors are close to or larger than the space between fibers in extracellular matrix and (ii) viral proteins are potentially toxic in normal tissues. In general, gene delivery is hindered by various physiological barriers to virus transport from the site of injection to the nucleus of tumor cells and is limited by normal tissue tolerance of toxicity determined by local concentrations of transgene products and viral proteins. To illustrate the obstacles encountered in the delivery and yet limit the scope of discussion, this review focuses only on extracellular transport in solid tumors and distribution of viral vectors in normal organs after they are injected intravenously or intratumorally. This review also discusses current strategies for improving intratumoral transport and specificity of viral vectors.

Efficient Gene Transfer into Differentiated Human Trophoblast Cells with Adenovirus Vector Containing RGD Motif in the Fiber Protein

Previously we reported fiber-modified adenovirus (Ad) vectors containing the Arg-Gly-Asp (RGD) motif on the HI loop of the fiber knob (Ad-RGD vectors) have high gene transfer efficacy into some human trophoblast cell lines. In the current study, we investigate transgene activity of Ad-RGD during differentiation of human cytotrophoblast BeWo cells into syncytiotrophoblast-like cells. Although cellular differentiation into syncytiotrophoblast cells was followed by a decrease in the coxsackievirus and adenovirus receptor levels on the cell membrane, the alphaVbeta3 and alphaVbeta5 integrin levels did not change. Conventional adenovirus vector had lower transduction activity in the differentiated cells than non-differentiated cells. In contrast, Ad-RGD vector had no influence on differentiation and had a ca. 2-5 fold higher transduction activity than that of the conventional Ad vector. Thus, Ad-RGD vector can be a powerful tool for gene transfer experiments in syncytiotrophoblast cells.

Replicative oncolytic adenoviruses in multimodal cancer regimens

The use of replication-competent viruses that have a cytolytic cycle has emerged as a viable strategy (oncolytic virotherapy) to specifically kill tumor cells and the field has advanced to the point of clinical trials. A theoretical advantage of replicative oncolytic viruses is that their numbers should increase via viral replication within infected tumor cells and resulting viral progeny can then infect additional cells within the tumor mass. The life cycle of a virus involves multiple interactions between viral and cellular proteins/genes, which maximize the ability of the virus to infect and replicate within cells. Understanding such interactions has led to the design of numerous genetically engineered adenovirus (Ad) vectors that selectively kill tumor cells while sparing normal cells. These viruses have also been modified to function as therapeutic gene delivery vehicles, thus augmenting their anticancer capacity. In addition, the oncolytic mode of tumor killing differs from that of standard anticancer therapies, providing the possibility for synergistic interactions with other therapies in a multimodal antitumor approach. In this review, we describe the oncolytic Ad vectors tested in preclinical and clinical models and their use in combination with chemo-, radio-, and gene therapies.

Effective gene transfer to human melanomas via integrin-targeted adenoviral vectors

The utility of recombinant adenoviral vectors (Adv) for gene therapy is limited by their low transduction efficiency and lack of specificity for target cells. The low transduction efficiency is often recognized as due to deficiency of the primary adenoviral receptor, the coxsackievirus-adenovirus receptor (CAR). In this paper, studies of CAR levels on human melanoma cell lines confirmed that low transduction efficiency was closely related to deficiency of the adenoviral receptor. To achieve CAR-independent gene transfer via Adv, we modified viral tropism via genetic alteration of the adenovirus type 5 (Ad5) fiber protein. Insertion of an Arg-Gly-Asp (RGD)-containing peptide in the HI loop of the fiber knob domain allowed the virus to use an alternative receptor, the integrin receptor, during the cell entry process. With this modified vector (Adv-F/RGD) transduction was increased 5- to 96-fold relative to a vector containing wild-type fiber (Adv-F/wt) in five human melanoma cells expressing integrins of the alpha(v)beta(3), alpha(v)beta(5) class, which are recognized by the RGD peptide motif. In contrast, no significant difference in transduction efficiency between Adv-F/RGD and Adv-F/wt was observed in 293 cells, which show high-level expression of CAR. In this study, we attempted to apply Adv-F/RGD for gene therapy for malignant melanoma. At the same multiplicity of infection, melanoma cells infected with Adv-F/RGD carrying human interleukin 2 (AxCAhIL2-F/RGD) produced a higher level of cytokine than cells infected with AxCAhIL2-F/wt. Treatment by intratumoral injection of AxCAhIL2-F/RGD was more effective than intratumoral injection of AxCAhIL2-F/wt in regressing tumors in a melanoma xenograft model. These data suggest that integrin-targeted adenoviral vectors may be a powerful tool in gene therapy for CAR-deficient melanomas.

p53 Mutation in bladder cancer patients in Japan and inhibition of growth by in vitro adenovirus-mediated wild-type p53 transduction in bladder cancer cells

BACKGROUND

Altered expression of p53 has been described in nearly half of bladder cancers, and p53 mutations are presumed to play a role in the multistep progression of these tumors.

MATERIALS AND METHODS

The incidence of mutation in the p53 gene and its correlation with histopathologic findings and patient survival were evaluated in 105 Japanese patients with bladder cancer. Laboratory experiments were also performed to confirm the infectivity and efficacy in tumor growth inhibition of an adenovirus expressing wild-type p53 in EJ bladder cancer cells.

RESULTS

Mutations of p53 were observed in 38 bladder cancer specimens (36%), with a significantly higher incidence of mutation being seen in tumors of higher stage and grade. The overall survival was worse in patients with the p53 mutation. In laboratory experiments, adenoviral vectors infected bladder cancer cells in a dose- and cell density-dependent manner. The adenovirus-mediated transduction of wild-type p53 resulted in dose-dependent growth inhibition of bladder cancer cells in vitro. No significant cytotoxicity was observed after infection by a control adenovirus.

CONCLUSION

Transduction of wild-type p53 might be a potential therapeutic option for bladder cancer.

Targeting of high-capacity adenoviral vectors

High-capacity adenoviral (HC-Ad) vectors contain only the noncoding termini of the viral genome, can deliver large DNA fragments of up to 36 kb into target cells, and feature reduced toxicity and prolonged transgene expression in vivo. To enhance the potential of HC-Ad vectors to transduce specific cell types, we constructed a versatile infectious new helper virus plasmid that can be used readily to introduce peptide ligands into the HI loop of the fiber knob domain of Ad5-based HC-Ad vectors. Helper viruses with a 6x-His epitope or Arg-Gly-Asp (RGD) peptide insertion retained the full infectivity of the wild-type helper virus. The RGD-modified helper virus was used for production of a capsid-modified HC-Ad vector expressing beta-galactosidase. The RGD HC-Ad vector transduced the ovarian carcinoma cell lines SK-OV-3 and OVCAR-3 with 4- to 20-fold higher efficiency, compared to unmodified vectors. Transduction of both primary vascular smooth muscle cells as well as primary human endothelial cells was increased up to 15-fold with the RGD-modified vector. Competition experiments with recombinant knob protein and different RGD peptides indicated that the RGD-mediated transduction was Coxsackie and Adenovirus receptor (CAR)-independent and involved integrin alpha(v)beta(5). The use of fiber-modified helper viruses in the last amplification step of HC-Ad vector production allows for convenient and efficient targeting of these vectors towards different cell types. Targeting strategies will increase the spectrum of applications for HC-Ad vectors and will further add to their safety.

Protease-deleted adenovirus vectors and complementing cell lines: potential applications of single-round replication mutants for vaccination and gene therapy

A new kind of versatile adenoviral vector (AdV) has been constructed, one that is completely replication disabled in the absence of Ad-E1 proteins but is capable of a single round of replication when Ad-E1 is present. This was made possible by deletion of the Ad protease gene (PS), which is essential for many steps of the Ad life cycle. The PS-deleted virus can be propagated in 293-derived cell lines engineered to express PS. In these new complementing cells, the PS gene was expressed from a tetracycline-inducible promoter in a dicistronic vector coexpressing the green fluorescent protein (GFP). When induced, the best 293-PS stable clones produced the PS in amounts greater than the level reached after Ad infection. Biological activity was first demonstrated by the ability of 293-PS cells to support the replication of Ad2ts1, a mutant expressing a functionally defective PS. While overexpression of the Ad PS slightly affected cell growth, moderate expression at levels sufficient to fully complement Ad2ts1 was well tolerated in 293 cells. Two PS-deleted mutants, deleted or not deleted for E1/E3, were then generated and characterized. Despite their complete loss of infectivity after a single round of replication in permissive cells, the PS-deleted mutants produced as much viral protein as wildtype Ad. These new vectors should thus be both safer and more efficient for applications in which enhancement of transgene expression is desirable, as in the case of vaccination, in situ therapy for tumors, protein production, or the large-scale production of other viral vectors such as adeno-associated virus (AAV).

Adenovirus-mediated transfer of caspase-8 augments cell death in gliomas: implication for gene therapy

Caspase-8 is a member of the family of caspases, which are involved in the execution of apoptosis. To investigate whether caspase-8 can be used for gene therapy of gliomas, we transduced A-172 and U251 glioma cells with the caspase-8 gene via an adenoviral vector (Adv) controlled by the chicken beta-actin (CA) promoter (Advcaspase-8), and found that a similar level of caspase-8 protein induced A-172 cells to undergo necrotic cell death and U251 cells to undergo apoptotic cell death. Neither Bcl-XL nor Bcl-2, which play important roles in antiapoptotic mechanisms in gliomas, protected glioma cells from apoptosis induced by overexpression of caspase-8. Injection of Adv-caspase-8 suppressed the in vivo growth of U251 xenografts, in which apoptotic cell death remarkably increased as revealed by TUNEL analysis. Finally, we assessed whether gene therapy with a tissue-specific promoter, the myelin basic protein (MBP) promoter, is applicable to gliomas. Adv for caspase-8 controlled by the MBP promoter induced drastic apoptosis in U251 and U-373MG glioma cells, whereas it did not induce apoptosis in human endothelial cells, fibroblasts, and nerve growth factor-treated PC12 cells. These results indicate that Adv for caspase-8 effectively induced cell death in gliomas, and that this approach may be a useful modality for gene therapy of gliomas.

Effective gene therapy for pancreatic cancer by cytokines mediated by restricted replication-competent adenovirus

Pancreatic cancer has a poor prognosis even when surgical treatment can be accomplished. Studies have demonstrated that pancreatic cancer is associated with various genetic abnormalities in oncogenes and tumor suppressor genes including p53. New therapeutic approaches for pancreatic cancer can be developed by targeting these genetic alterations. Adenovirus (Adv) lacking the 55-kDa E1B protein (E1B55K) replicates preferentially in p53-deficient cancer cells. We constructed E1B55K-deleted Adv (AxE1AdB), and studied its replication and cytopathic effect on pancreatic cancer cells. AxE1AdB replicated in and caused cell death of the p53-deficient pancreatic cancer cell lines tested (e.g., PANC-1, MIAPaCa-2, SU.86.86, BxPC-3, and PK-1). To enhance its therapeutic effect, we examined the combination of coinfecting this restricted replication-competent adenovirus (RRCA) with other Adv. Coinfection of E1-deficient Adv expressing the reporter lacZ gene (AxCAlacZ) together with AxE1AdB resulted in the replication of both viruses and a marked increase in reporter gene expression. PANC-1 cells coinfected with AxE1AdB and the Adv for human IL-2 (AxCAhIL2), produced 110 times more IL-2 than those infected with AxCAhIL2 alone. Similarly, coinfection of AxE1AdB and Adv for human IL-12 augmented the IL-12 production by 370-fold. Injecting AxE1AdB into the PANC-1 tumor of severe combined immunodeficient mice (SCID mice) resulted in marked reduction of the volume of the tumor. Moreover, injecting AxE1AdB with AxCAhIL2 into the PANC-1 tumor resulted in complete regression of the established tumors. These data suggest that RRCA, which augments the antitumor effect of a viral transgene (i.e., cytokines), may be a powerful tool for treating p53-deficient pancreatic cancer.

Relative level of expression of Bax and Bcl-XL determines the cellular fate of apoptosis/necrosis induced by the overexpression of Bax

The Bax protein plays a critical role in the apoptosis of cancers induced by radiotherapy or chemotherapy, which induce both apoptosis and necrosis. We transduced various glioblastoma cells with the Bax gene via an adenoviral vector and found that A-172 cells led to necrotic cell death, while U251 cells apoptotic cell death, even though a similar level of Bax protein was introduced. A-172 cells displayed a much higher constitutive expression of the Bcl-XL protein compared with that of U251 cells. Upon simultaneous overexpression of the Bcl-XL and Bax proteins in the U251 cells, Bax-induced apoptosis of U251 cells was suppressed and an increase in the number of necrotic cells was seen. Moreover, induction of a higher amount of Bax protein in A-172 cells increased the percentage of apoptotic cells. In conclusion, if a cancerous cell expresses a high enough amount of Bax to undergo death, apoptosis will be induced. If a cancerous cell expresses a level of Bcl-XL which prevents Bax-induced apoptosis, the overexpression of Bax leads to necrotic cell death.