Selective gene delivery toward gastric and esophageal adenocarcinoma cells via EpCAM-targeted adenoviral vectors

Interferon Alpha-Expressing Oncolytic Adenovirus for Treatment of Esophageal Adenocarcinoma

INTRODUCTION

Esophageal adenocarcinoma (EAC) has increased in incidence in Western countries, and its poor prognosis necessitates the development of novel therapeutics. We previously reported the potential of conditionally replicative adenoviruses (CRAd) as a novel therapeutic treatment for this disease. To further augment the therapeutic effectiveness of our cyclooxygenase-2 (Cox2) controlled CRAd in EAC, we inserted an interferon alpha (IFN) transgene into the viral genome that is expressed upon viral replication. In this manuscript, we analyze the cytotoxic and oncolytic effects of an IFN-expressing oncolytic adenovirus in EAC and the role of the Cox2 promoter in providing for selective replication in human tissues.

METHODS

An infectivity-enhanced IFN-expressing CRAd (5/3 Cox2 CRAd ΔE3 ADP IFN) and other control viruses were first tested in vitro with cell lines. For the in vivo study, EAC xenografts in nude mice were treated with a single intratumoral dose of virus. An ex vivo analysis with live tissue slices was conducted using surgically resected EAC patient specimens.

RESULTS

Expression of IFN significantly enhanced the cytotoxic and oncolytic effect of a Cox2-promoter controlled CRAd. This virus showed significant tumor growth suppression in a xenograft model. Furthermore, in human EAC samples, the promoter-controlled virus demonstrated selective replication in cancerous tissues, leaving normal esophageal tissue unaffected.

CONCLUSION

An IFN-expressing CRAd driven by the Cox2 promoter has strong oncolytic effects as well as cancer-specific replication. Our novel vector possesses critical characteristics that make it a potential candidate for clinical translation to treat EAC.

Sticking to the Problem: Engineering Adhesion in Molecular Endoscopic Imaging

Cancers of the digestive tract cause nearly one quarter of the cancer deaths worldwide, and nearly half of these are due to cancers of the esophagus and colon. Early detection of cancer significantly increases the rate of survival, and thus it is critical that cancer within these organs is detected early. In this regard, endoscopy is routinely used to screen for transforming/cancerous (i.e. dysplastic to fully cancerous) tissue. Numerous studies have revealed that the biochemistry of the luminal surface of such tissue within the colon and esophagus becomes altered throughout disease progression. Molecular endoscopic imaging (MEI), an emerging technology, seeks to exploit these changes for the early detection of cancer. The general approach for MEI is as follows: the luminal surface of an organ is exposed to molecular ligands, or particulate probes bearing a ligand, cognate to biochemistry unique to pre-cancerous/cancerous tissue. After a wash, the tissue is imaged to determine the presence of the probes. Detection of the probes post-washing suggests pathologic tissue. In the current review we provide a succinct, but extensive, review of ligands and target moieties that could be, or are currently being investigated, as possible cognate chemistries for MEI. This is followed by a review of the biophysics that determines, in large part, the success of a particular MEI design. The work draws an analogy between MEI and the well-advanced field of cell adhesion and provides a road map for engineering MEI to achieve assays that yield highly selective recognition of transforming/cancerous tissue in situ.

Relationship between epithelial cell adhesion molecule (EpCAM) overexpression and gastric cancer patients: A systematic review and meta-analysis

OBJECTIVES

The epithelial cell adhesion molecule (EpCAM) is one of the most commonly used markers of cancer stem cells (CSCs), but the clinical and prognostic significance of EpCAM in gastric cancer (GC) remains disputable. Motivated by heterogeneous and inconclusive results, we conducted a systematic review and meta-analysis to systematically summarize and elucidate the association between EpCAM overexpression and GC patients.

METHODS

The PubMed, Cochrane Library, Medline, Web of Knowledge and the China National Knowledge Infrastructure (CNKI) databases were searched to identify relevant studies. The RevMan 5.3 software was used for the meta-analysis. Fixed-effects or random-effects models were applied depending on the presence of heterogeneity. The pooled odds ratio (ORs) and 95% confidence intervals (CIs) were applied to estimate the associations between EpCAM and gastric cancer. For the significant heterogeneity studies, sensitivity analyses were applied based on the population to test the robustness of the pooled results and identify possible sources of heterogeneity.

RESULTS

A total of 11 studies including 1960 GC patients met our inclusion criteria. The results of the meta-analyses revealed that there were significant differences in EpCAM overexpression and tumour size (OR = 2.97, 95% CI: 2.13~4.13, P < 0.00001), the nature of the tissue (OR = 80.30, 95% CI: 29.21~220.81, P < 0.00001), lymph node metastasis (OR = 2.78, 95% CI: 1.23~6.27, P = 0.01), and the cumulative 5-year overall survival rate (OR = 0.54, 95% CI:0.29~0.99, P = 0.05). No significant associations were identified between EpCAM overexpression and gender (OR = 0.89, 95% CI: 0.66~1.19, P = 0.43), age (OR = 1.13, 95% CI: 0.58~2.20, P = 0.73), tumour stage (OR = 2.26, 95% CI: 0.79~6.45, P = 0.13), distant metastasis (OR = 2.15, 95% CI: 0.20~22.69, P = 0.52), TNM stage (OR = 5.14, 95% CI: 0.77~34.37, P = 0.09), Lauren type (OR = 1.18, 95% CI: 0.08~16.45, P = 0.9), differentiation (OR = 1.88, 95% CI: 0.65~5.41, P = 0.24). However, due to significant heterogeneity in tumor stage, lymph node metastasis, TNM stage, differentiation and Lauren type, these results should be taken carefully.

CONCLUSIONS

The meta-analysis demonstrated that the expression of EpCAM in the gastric cancer group was greater than that in the control group. Moreover, EpCAM overexpression was associated with larger tumour size, lymphnode metastasis and worse prognosis in gastric cancer. Due to significant heterogeneity, the sensitivity analysis suggests that population factor may be an important source of heterogeneity, and these results should be treated with caution. EpCAM may be useful as a novel prognostic factor, and large-scale and well-designed studies are needed to validate our results in the future.

Targeted Adenoviral Vectors I

Human adenovirus (Ad) has been used extensively to develop gene transfer vectors for vaccine and gene therapy applications. A major factor limiting the efficacy of the current generation of Ad vectors is their inability to accomplish specific gene delivery to the cells of interest. Transductional targeting strategies seek to redirect virus binding to the appropriate cellular receptor to increase infection efficiency in selected cell types to achieve therapeutic intervention. These efforts mainly focused on incorporating targeting ligands by means of chemical conjugation or genetic modification of Ad capsid proteins and using bispecific adapter molecules to mediate virus recognition of target cells. This review summarizes current progress in Ad tropism modification maneuvers that embody genetic capsid modification and adapter-based approaches that have encouraging implications for further development of advanced vectors suitable for clinical translation.

EpCAM is overexpressed in local and metastatic prostate cancer, suppressed by chemotherapy and modulated by MET-associated miRNA-200c/205

Background:

Expression of epithelial cell adhesion molecule (EpCAM) is deregulated in epithelial malignancies. Beside its role in cell adhesion, EpCAM acts as signalling molecule with tumour-promoting functions. Thus, EpCAM is part of the molecular network of oncogenic receptors and considered an interesting therapeutic target.

Methods:

Here, we thoroughly characterised EpCAM expression on mRNA and protein level in comprehensive tissue studies including non-cancerous prostate specimens, primary tumours of different grades and stages, metastatic lesions, and therapy-treated tumour specimens, as well as in prostate cancer cell lines.

Results:

Epithelial cell adhesion molecule was overexpressed at mRNA and at protein level in prostate cancer tissues and cell lines. Altered EpCAM expression was an early event in prostate carcinogenesis with an upregulation in low-grade cancers and further induction in high-grade tumours and metastatic lesions. Interestingly, EpCAM was repressed upon induction of epithelial-to-mesenchymal transition (EMT) following chemotherapeutic treatment with docetaxel. Oppositely, re-induction of the epithelial phenotype through miRNAs miR-200c and miR-205, two inducers of mesenchymal-to-epithelial transition (MET), led to re-induction of EpCAM in chemoresistant cells. Furthermore, we prove that EpCAM cleavage, the first step of EpCAM signalling takes place in prostate cancer cells but in contrast to other cancer entities, EpCAM has no measurable impact on the proliferative behaviour of prostate cells, in vitro.

Conclusions:

In conclusion, our data confirm that EpCAM overexpression is an early event during prostate cancer progression. Epithelial cell adhesion molecule displays a dynamic, heterogeneous expression and associates with epithelial cells rather than mesenchymal, chemoresistant cells along with processes of EMT and MET.

Presence of the coxsackievirus and adenovirus receptor (CAR) in human neoplasms: a multitumour array analysis

Background:

The Coxsackie- and Adenovirus Receptor (CAR) has been assigned two crucial attributes in carcinomas: (a) involvement in the regulation of growth and dissemination and (b) binding for potentially therapeutic adenoviruses. However, data on CAR expression in cancer types are conflicting and several entities have not been analysed to date.

Methods:

The expression of CAR was assessed by immunohistochemical staining of tissue microarrays (TMA) containing 3714 specimens derived from 100 malignancies and from 273 normal control tissues.

Results:

The expression of CAR was detected in all normal organs, except in the brain. Expression levels, however, displayed a broad range from being barely detectable (for example, in the thymus) to high abundance expression (for example, in the liver and gastric mucosa). In malignancies, a high degree of variability was notable also, ranging from significantly elevated CAR expression (for example, in early stages of malignant transformation and several tumours of the female reproductive system) to decreased CAR expression (for example, in colon and prostate cancer types).

Conclusion:

Our results provide a comprehensive insight into CAR expression in neoplasms and indicate that CAR may offer a valuable target for adenovirus-based therapy in a subset of carcinomas. Furthermore, these data suggest that CAR may contribute to carcinogenesis in an entity-dependent manner.

Biological delivery approaches for gene therapy: strategies to potentiate efficacy and enhance specificity

Nowadays many therapeutic agents such as suicide genes, anti-angiogenesis agents, cytokines, chemokines and other therapeutic genes were delivered to cancer cells. Various biological delivery systems have been applied for directing therapeutic gene to target cells. Some of these successful preclinical studies, steps forward to clinical trials and a few are examined in phase III clinical trials. In this review, the biological gene delivery systems were categorized into microorganism and cell based delivery systems. Viral, bacterial, yeast and parasite are among microorganism based delivery systems which are expanded in this review. In cell based approach, different strategies such as tumor cells, stem cells, dendritic cells and sertoli cells will be discussed. Different drawbacks are associated with each delivery system; therefore, many strategies have been improved and potentiated their direction toward specific target cells. Herein, further to the principle of each delivery system, the progresses of these approaches for development of newer generation are discussed.

Effect of increased viral replication and infectivity enhancement on radioiodide uptake and oncolytic activity of adenovirus vectors expressing the sodium iodide symporter

Our laboratory has investigated replicating adenovirus-human sodium iodide symporter (Ad-hNIS) vectors in a combinatorial oncolytic approach known as radiovirotherapy. However, hNIS-mediated iodide sequestration requires an intact cell membrane, and the enhancement of infectivity may alter the radioiodide accumulation in vivo. To assess these effects, we constructed Ad-NIS vectors expressing NIS from the major late promoter. Viral tropism was altered using a hybrid Ad5/3 fiber, and rates of viral spread altered through expression of the Ad death protein (ADP). The hybrid 5/3 fiber enhanced Ad-mediated cytolysis and radioisotope uptake in vitro. Replicating ADP-lacking viral vectors showed levels of uptake similar to non-replicating vectors that declined as cells lysed. ADP expression enhanced the rate of cell lysis and viral release, but reduced the peak and duration of radioiodide uptake. SPECT-computed tomography imaging showed the Ad5/3-noADP-hNIS vector induced significantly more isotope uptake than other vector structures, indicating that viral spread may not always make up for the reduced NIS expression as in our work with prostate cancer. These results indicate that replicating, infectivity-enhanced Ad-NIS vectors provide superior overall efficacy, but also indicate that the effect of replication speed requires tumor and model-specific testing.

Epithelial cell adhesion molecule-targeted drug delivery for cancer therapy

INTRODUCTION

The epithelial cell adhesion molecule (EpCAM) is abundantly expressed in epithelial tumors, on cancer stem cells and circulating tumor cells. Together with its role in oncogenic signaling, this has sparked interest in its potential for tumor targeting with antibodies and drug conjugates for safe and effective cancer therapy. Recent advances in protein engineering, linker design and drug formulations have provided a multitude of EpCAM-targeting anticancer agents, several of them with good perspectives for clinical development.

AREAS COVERED

This article reviews the biological, therapeutic and technical aspects of EpCAM-targeted drug delivery for cancer therapy. The authors discuss seminal findings, which distinguish EpCAM as a target with oncogenic function and abundant expression in epithelial tumors. Moreover, recent trends in engineering improved anti-EpCAM antibodies, binding proteins that are not derived from immunoglobulins and drug conjugates derived from them are highlighted and their therapeutic potential based on reported preclinical and clinical data, originality of design and perspectives are critically assessed.

EXPERT OPINION

EpCAM has shown promise for safe and efficient targeting of solid tumors using antibodies, alternative binding molecules and novel drug conjugates. Among the myriad of EpCAM-targeting drug delivery systems investigated so far, several could demonstrate therapeutic benefit, other formulations engineered to become tailor-made missiles are on the brink.

Therapeutic potential of amanitin-conjugated anti-epithelial cell adhesion molecule monoclonal antibody against pancreatic carcinoma

BACKGROUND

Human epithelial cell adhesion molecule (EpCAM) is overexpressed in many cancers. Anti-EpCAM antibodies have shown promise in preclinical studies, but showed no tumor regression in a recent phase II clinical trial. Therefore, we generated a novel anti-EpCAM antibody-drug conjugate and assessed whether it showed enhanced antitumor effects.

METHODS

Chemical cross-linking was conducted to covalently conjugate α-amanitin, a toxin known to inhibit DNA transcription, with chiHEA125, a chimerized anti-EpCAM monoclonal antibody, to generate the antibody-drug conjugate α-amanitin-glutarate-chiHEA125 (chiHEA125-Ama). Antiproliferative activity of chiHEA125-Ama was tested in human pancreatic (BxPc-3 and Capan-1), colorectal (Colo205), breast (MCF-7), and bile duct (OZ) cancer cell lines in vitro using [(3)H]-thymidine incorporation assay. Antitumor activity of chiHEA125-Ama was assessed in vivo in immunocompromised mice bearing subcutaneous human BxPc-3 pancreatic carcinoma xenograft tumors (n = 66 mice). Cell proliferation and apoptosis were evaluated in xenograft tumors by immunohistochemistry. All statistical tests were two-sided.

RESULTS

In all cell lines, chiHEA125-Ama reduced cell proliferation (mean half maximal inhibitory concentration [IC(50)] = 2.5 × 10(-10) to 5.4 × 10(-12) M). A single dose of chiHEA125-Ama inhibited BxPc-3 xenograft tumor growth (chiHEA125 [control, n = 4 mice] vs. chiHEA125-Ama [n = 6 mice], dose of 15 mg/kg with respect to IgG and 50 μg/kg with respect to α-amanitin, mean relative increase in tumor volume on day 16 = 884% vs. -79%, difference = 963%, 95% CI = 582% to 1344%, P = .019). Two higher doses of chiHEA125-Ama (100 μg/kg with respect to α-amanitin), administered 1 week apart (n = 10 mice per group), led to complete tumor regression in nine of 10 (90%) mice compared with chiHEA125, during the observation period of 16 days; increased apoptosis and reduced cell proliferation were observed in mice treated with chiHEA125-Ama.

CONCLUSION

This preclinical study suggests that anti-EpCAM antibody conjugates with α-amanitin have the potential to be highly effective therapeutic agents for pancreatic carcinomas and various EpCAM-expressing malignancies.

Retargeting of viruses to generate oncolytic agents

Oncolytic virus therapy is based on the ability of viruses to effectively infect and kill tumor cells without destroying the normal tissues. While some viruses seem to have a natural preference for tumor cells, most viruses require the modification of their tropism to specifically enter and replicate in such cells. This review aims to describe the transductional targeting strategies currently employed to specifically redirect viruses towards surface receptors on tumor cells. Three major strategies can be distinguished; they involve (i) the incorporation of new targeting specificity into a viral surface protein, (ii) the incorporation of a scaffold into a viral surface protein to allow the attachment of targeting moieties, and (iii) the use of bispecific adapters to mediate targeting of a virus to a specified moiety on a tumor cell. Of each strategy key features, advantages and limitations are discussed and examples are given. Because of their potential to cause sustained, multiround infection—a desirable characteristic for eradicating tumors—particular attention is given to viruses engineered to become self-targeted by the genomic expression of a bispecific adapter protein.

Impact of the coxsackievirus and adenovirus receptor on the adenoma-carcinoma sequence of colon cancer

Background:

Coxsackie and adenovirus receptor (CAR) has been suggested to function as a tumour suppressor. Its impact on the adenoma–carcinoma sequence of the colon, however, is unclear.

Methods:

Coxsackie and adenovirus receptor was analysed in non-cancerous and neoplastic colon samples using immunohistochemistry and quantitative RT–PCR. The function of CAR in colon cancer cell lines was determined following application of CAR siRNA or ectopic expression of a human full-length CAR cDNA.

Results:

Compared with healthy mucosa, increased CAR-mRNA expression was found in adenomas, whereas primary cancers and metastases displayed a marked decline. At the plasma membrane, CAR was present in normal mucosa samples (93%), adenomas, and metastases (100% ea.), whereas in colon cancers, it was found less frequently (49%, P<0.0001). Cytoplasmic CAR immunopositivity increased from normal mucosa (22%), to adenomas (73%, P=0.0006), primary cancers (83%, P<0.0001), and metastases (67%, P=0.0019). In cancer cell lines, CAR inhibition resulted in increased proliferation, whereas enforced ectopic CAR expression led to opposite results. Blocking the extracellular portion of CAR increased cell invasion in vitro. In mice, xenotransplants of colon cancer cells with enforced CAR expression formed significantly smaller tumours, whereas CAR inhibition increased the formation of liver metastases.

Conclusion:

We conclude that CAR facilitates complex effects during colon carcinogenesis, potentially mediated by its stage-dependent subcellular distribution; high CAR expression potentially prevents apoptosis in adenomas, loss of CAR at the plasma membrane promotes growth, and dissemination of primary cancers, and high membranous CAR presence may support the establishment of distant metastases.

EpCAM- and EGFR-targeted selective gene therapy for biliary cancers using Z33-fiber-modified adenovirus

A critical issue in adenovirus (Ad)-based cancer gene therapy is to improve the specificity of gene delivery to cancer cells for better efficacy and safety. We explored methods of retargeting Ad vectors for selective gene therapy of human biliary cancers using the Ad incorporating an IgG Fc-binding motif (Z33) from the Staphylococcus protein A (Ad-FZ33) combined with tumor-specific antibodies. Flow cytometry analysis revealed high-expression levels of epithelial cell adhesion molecule (EpCAM) and epidermal growth factor receptor (EGFR) on human biliary cancer cells. Ad-FZ33 expressing LacZ combined with antibodies against EpCAM or EGFR, followed by β-gal assay, demonstrated highly efficient gene transduction in these biliary cancer cells, compared to the treatment with control antibody or without antibody. Ad-FZ33 expressing uracil phosphoribosyl transferase (UPRT), an enzyme which greatly enhances the toxicity of 5-fluorouracil (FU), combined with antibodies against EpCAM or EGFR, remarkably enhanced the sensitivity of biliary cancer cells to 5-FU. By contrast, the treatment did not affect the 5-FU sensitivity of the cells not expressing EpCAM or EGFR including normal hepatocytes. Finally, treatments with the UPRT-expressing Ad-FZ33 with antibodies against EpCAM or EGFR, followed by 5-FU administration, significantly suppressed the growth of biliary cancer xenografts in nude mice. These results indicate that the gene therapy mediated by the Z33 fiber modified Ad with anti-EpCAM or anti-EGFR antibodies offers a potentially effective therapeutic modality against biliary cancers.

Adenoviral oncolytic suicide gene therapy for a peritoneal dissemination model of gastric cancer in mice

BACKGROUND

Peritoneal dissemination of gastric cancer is often refractory to systemic therapies. Although adenoviral gene therapy has been reported to be a potentially useful therapeutic modality, the adenovirus itself has a dose-limiting toxicity. A novel system was constructed using adenoviral oncolytic suicide gene therapy targeting carcinoembryonic antigen (CEA), and its therapeutic effect and the possibility to reduce the total viral dose while still preserving the antitumor effect were assessed.

METHODS

Three types of adenoviruses were prepared for this novel system: (A) Ad/CEA-Cre, (B) Ad/lox-CD::UPRT for a Cre/loxP system, and (C) Ad/CEA-E1 for conditionally replicating adenovirus. The antitumor effect of the oncolytic suicide gene therapy (A + B + C) was then evaluated in vitro. Mice bearing peritoneal dissemination of human gastric cancer were treated with either this system (A + B + C) or with a tenfold viral dose of suicide gene therapy (A + B). The adverse effects in terms of hepatotoxicity were then evaluated between the two groups.

RESULTS

The current system (A + B + C) demonstrated significantly better cytotoxic effect for CEA-producing cell lines than did suicide gene therapy (A + B) at the same viral dose in vitro. The effect of oncolytic suicide gene therapy was almost equal to that of the tenfold viral dose of suicide gene therapy in vivo. The hepatotoxicity of the two treated groups was also found to be equivalent.

CONCLUSION

It was possible to reduce the total adenoviral dose of oncolytic suicide gene therapy while still preserving the antitumor effect.

Downregulation of the coxsackie and adenovirus receptor in cancer cells by hypoxia depends on HIF-1alpha

Loss of the coxsackie and adenovirus receptor (CAR) has been found in various human cancers. Underlying mechanisms, however, are still poorly understood. Therefore, the objective of this study was to investigate the function of hypoxia, a ubiquitous phenomenon in carcinomas, in CAR regulation. In our approach, hypoxia and treatment with cobalt-(II)-chloride (CoCl(2)) induced a downregulation of CAR protein and mRNA expression, as well as a suppression of CAR gene promoter activity in AGS (gastric), SW480 (colon) and PC3 (prostate) cancer cells. In line with these findings we noted a decreased adenoviral uptake under hypoxic conditions. Aiming to further elucidate the molecular basis of this observation, a full-length hypoxia-inducible factor-1alpha (HIF-1alpha) cDNA was ectopically overexpressed in the AGS cell line diminishing CAR expression and CAR gene promoter activity. In line with these findings, exposure of HIF-1alpha-deficient AGS cells to hypoxia did not alter CAR mRNA expression level. On the basis of these data, it may be suggested that loss of CAR in human cancer cell lines under hypoxic conditions occurs in an HIF-1alpha-dependent manner.

Effectiveness of HSV-tk suicide gene therapy driven by the Grp78 stress-inducible promoter in esophagogastric junction and gastric adenocarcinomas

BACKGROUND

The thymidine kinase gene of the herpes simplex virus (HSV-tk) is a suicide gene when administrated with the prodrug ganciclovir (GCV). This study investigated the effectiveness of HSV-tk activation as gene therapy for gastroesophageal junction and gastric adenocarcinomas using either the stress-inducible Grp78 promoter or the murine leukemia virus long-terminal repeat (LTR) promoter.

METHODS

The HSV-tk gene, controlled by either the Grp78 promoter or the LTR promoter, was transduced into the gastroesophageal junction adenocarcinoma cell line SK-GT-5 and the gastric adenocarcinoma cell line MKN-74. Cell viability after exposure to varying concentrations of GCV was compared. The same cell lines were used to develop a nude mouse model for studies of the HSV-tk/GCV effect in vivo. The effect of intraperitoneal GCV injection on growth of the subcutaneous tumors was measured. HSV-TK expression was measured by Western blot and reverse transcription polymerase chain reaction.

RESULTS

Cell viability in vitro was significantly lower in the HSV-tk expressing (HSV-tk+) cells compared to control (no HSV-tk) cells after exposure to GCV. MKN-74tk+ cells were more sensitive to GCV killing than SK-GT-5tk+ cells. After culture with 1 microg/ml GCV for 10 days, MKN-74/tk cells were totally killed, whereas most SK-GT-5/tk cells survived. Cell viability was significantly lower under glucose starvation conditions when HSV-tk expression was regulated by the Grp78 promoter compared with the LTR promoter. MKN-74 tumors formed with HSV-tk+ cells in nude mice were eliminated after administration of GCV for 3 weeks, but GCV had no effect on tumors formed from HSV-tk- cells. Eradication of tumor formed with Grp78-tk cells was faster than that with LTR-tk cells. HSV-TK protein and mRNA were expressed in the transduced, but not the non-transduced tumors.

CONCLUSION

HSV-tk xwith ganciclovir suicide gene therapy results in significant cell killing in gastroesophageal junction and gastric adenocarcinoma cells both in vitro and in vivo, but complete tumor elimination only occurred with the gastric adenocarcinoma cell tumors. The most effective approach in this study used the Grp78 promoter in glucose-starvation stress conditions.

Adenoviral vector-based strategies for cancer therapy

Definitive treatment of cancer has eluded scientists for decades. Current therapeutic modalities like surgery, chemotherapy, radiotherapy and receptor-targeted antibodies have varied degree of success and generally have moderate to severe side effects. Gene therapy is one of the novel and promising approaches for therapeutic intervention of cancer. Viral vectors in general and adenoviral (Ad) vectors in particular are efficient natural gene delivery systems and are one of the obvious choices for cancer gene therapy. Clinical and preclinical findings with a wide variety of approaches like tumor suppressor and suicide gene therapy, oncolysis, immunotherapy, anti-angiogenesis and RNA interference using Ad vectors have been quite promising, but there are still many hurdles to overcome. Shortcomings like increased immunogenicity, prevalence of preexisting anti-Ad immunity in human population and lack of specific targeting limit the clinical usefulness of Ad vectors. In recent years, extensive research efforts have been made to overcome these limitations through a variety of approaches including the use of conditionally-replicating Ad and specific targeting of tumor cells. In this review, we discuss the potential strengths and limitations of Ad vectors for cancer therapy.

Loss of the coxsackie and adenovirus receptor contributes to gastric cancer progression

Loss of the coxsackie and adenovirus receptor (CAR) has previously been observed in gastric cancer. The role of CAR in gastric cancer pathobiology, however, is unclear. We therefore analysed CAR in 196 R₀-resected gastric adenocarcinomas and non-cancerous gastric mucosa samples using immunohistochemistry and immunofluorescence. Coxsackie and adenovirus receptor was found at the surface and foveolar epithelium of all non-neoplastic gastric mucosa samples (n=175), whereas only 56% of gastric cancer specimens showed CAR positivity (P<0.0001). Loss of CAR correlated significantly with decreased differentiation, increased infiltrative depths, presence of distant metastases, and was also associated with reduced carcinoma-specific survival. To clarify whether CAR impacts the tumorbiologic properties of gastric cancer, we subsequently determined the role of CAR in proliferation, migration, and invasion of gastric cancer cell lines by application of specific CAR siRNA or ectopic expression of a human full-length CAR cDNA. These experiments showed that RNAi-mediated CAR knock down resulted in increased proliferation, migration, and invasion of gastric cancer cell lines, whereas enforced ectopic CAR expression led to opposite effects. We conclude that the association of reduced presence of CAR in more severe disease states, together with our findings in gastric cancer cell lines, suggests that CAR functionally contributes to gastric cancer pathogenesis, showing features of a tumour suppressor.

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.

Exploration of target molecules for prostate cancer gene therapy

BACKGROUND

Focusing on Adv-FZ33, a modified adenovirus in which a synthetic 33-amino-acid immunoglobulin G-binding domain was inserted into the adenoviral fiber protein, we tried to identify suitable target molecules for prostate cancer-specific gene therapy.

METHODS

Hybridomas were established from mice immunized with prostate cancer cell lines. The hybridomas were screened using Adv-FZ33 to create monoclonal antibodies (mAbs) that induced high gene transfer efficiency for PC-3 cells. Furthermore, we identified target antigens of the mAbs by immunoprecipitation and mass spectrometry, and investigated the expression of target molecules by flow cytometry and immunocytochemistry.

RESULTS

Using Adv-FZ33, we established four different mouse mAbs that increased transduction efficiency for PC-3. The target antigens identified were Ep-CAM, CD155, HAI-1, and Na,K-ATPase beta1. These antigens were expressed in several cancer cell lines, including prostate cancer. Human prostatic myofibroblast cells lacked expression of Ep-CAM and HAI-1.

CONCLUSIONS

We established anti-Ep-CAM mAb and anti- HAI-1 mAbs. Gene transduction via Ep-CAM and HAI-1 may be a novel strategy for treatment of prostate cancer.

Novel system uses probasin-based promoter, transcriptional silencers and amplification loop to induce high-level prostate expression

Background

Despite several effective treatment options available for prostate cancer, it remains the second leading cause of cancer death in American men. Thus, there is a great need for new treatments to improve outcomes. One such strategy is to eliminate cancer through the expression of cytotoxic genes specifically in prostate cells by gene therapy vectored delivery. To prevent systemic toxicity, tissue- and/or cancer-specific gene expression is required. However, the use of tissue- or cancer-specific promoters to target transgene expression has been hampered by their weak activity.

Results

To address this issue, we have developed a regulation strategy that includes feedback amplification of gene expression along with a differentially suppressible tetracycline regulated expression system (DiSTRES). By differentially suppressing expression of the tetracycline-regulated transcriptional activator (tTA) and silencer (tTS) genes based on the cell origin, this leads to the activation and silencing of the TRE promoter, respectively. In vitro transduction of LNCaP cells with Ad/GFP_DiSTRES lead to GFP expression levels that were over 30-fold higher than Ad/CMV-GFP. Furthermore, Ad/FasL-GFP_DiSTRES demonstrated cytotoxic effects in prostate cancer cells known to be resistant to Fas-mediated apoptosis.

Conclusion

Prostate-specific regulation from the DiSTRES system, therefore, serves as a promising new regulation strategy for future applications in the field of cancer gene therapy and gene therapy as a whole.

Expression of coxsackie and adenovirus receptor reduces the lung metastatic potential of murine tumor cells

The coxsackie and adenovirus receptor (CAR) is involved in the epithelial cell tight junction, the downregulated expression of which is observed in different cancer types. In the present study, we examined CAR's role in tumor metastasis using a B16 melanoma and CT26 colon adenocarcinoma model of experimental metastasis. In lung metastasis, the colony number of B16 cells stably expressing CAR (B16CAR) was significantly lower than that of the control CAR-negative B16 cells. B16 and CT26 cells transiently expressing CAR, which were transduced with adenovirus (Ad) vector expressing CAR, also reduced lung metastasis, suggesting that CAR plays a role in the early stage of metastasis. CAR expression significantly decreased the accumulation of B16 cells in the lung after i.v. injection and the migration in vitro. CAR expression reduced expression of alpha(v), alpha(4), beta(3) and beta(1) integrin, which play important roles in attachment to cells or basement membrane. Thus, CAR expression likely acts as a metastatic suppressor.

Highly efficient and carcinoma-specific adenoviral replication restricted by the EGP-2 promoter

Although some successes have been reported using adenoviral vectors for the treatment of cancer, adenoviral cancer gene therapy is still hampered by the lack of sufficient tumor cell killing. To increase the efficiency, adenoviruses have been modified to replicate specifically in tumor tissues by using tumor specific promoters controlling genes essential for adenoviral replication. However, many conditionally replicating adenoviral vectors replicate in one tumor type only, which limits their application. The epithelial glycoprotein-2 (EGP-2) promoter is active in a broad variety of carcinomas, the most common type of cancer. We utilized this promoter to restrict adenoviral replication. In this report we demonstrate that the potency of the replication-competent adenovirus AdEGP-2-E1 to specifically lyse EGP-2 positive cells is comparable to wild-type adenovirus (AdWT). In addition, we show that in vivo AdEGP-2-E1 replicates as efficient as AdWT in EGP-2 positive tumor cells. On the contrary, in EGP-2 negative cell lines as well as in primary human liver samples, the replication was attenuated up to 4-log in comparison to wild-type virus. This report clearly shows the potency of the EGP-2 promoter to mediate highly efficient and specific adenoviral replication for carcinoma gene therapy.

The carcinoma-specific epithelial glycoprotein-2 promoter controls efficient and selective gene expression in an adenoviral context

Adenoviral vectors are widely used in cancer gene therapy. After systemic administration however, the majority of the virus homes to the liver and the expressed transgene may cause hepatotoxicity. To restrict transgene expression to tumor cells, tumor- or tissue-specific promoters are utilized. The tumor antigen epithelial glycoprotein-2 (EGP-2), also known as Ep-CAM, is expressed in many cancers from different epithelial origins. In this study, the EGP-2 promoter was shown to restrict the expression of luciferase and thymidine kinase in an adenoviral context in different cell lines. In vivo, the EGP-2 promoter mediated efficient expression of luciferase in tumors but showed a 3-log lower activity in liver tissue when compared with the cytomegalovirus (CMV) promoter. Similarly, the EGP-2 promoter mediated specific cell killing after ganciclovir treatment in EGP-2-positive cells. Moreover, in vivo, this treatment regiment did not cause any rise in the liver enzymes aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT), demonstrating absence of liver toxicity. In contrast, CMV-mediated expression of thymidine kinase in combination with ganciclovir treatment resulted in high ASAT and ALAT values. This study demonstrates the value of the EGP-2 promoter to restrict transgene expression to a broad range of tumor types, thereby preventing liver toxicity.

EpCAM Overexpression in Thyroid Carcinomas

Epithelial cell adhesion molecule (EpCAM) is expressed by a broad variety of carcinoma cells. It is recognized by the monoclonal antibody 17-1A, which has already been applied for immunotherapy of several carcinoma types in preclinical and small clinical studies. In the present study the immunohistochemical properties of 17-1A were evaluated in 121 cases of thyroid carcinomas of follicular cell origin, comprising of 75 differentiated (DTC; 35 papillary and 40 follicular carcinomas), 24 poorly differentiated (PDTC) and 22 anaplastic thyroid carcinomas. Overexpression of EpCAM, as recently defined, was found with a distinct membranous staining pattern in 81.3% of DTCs and in 66.6% of PDTCs. In contrast, all anaplastic thyroid carcinomas (0%) completely lacked EpCAM expression. Normal thyroid tissue presented with weak and heterogeneous EpCAM staining. This study demonstrates EpCAM overexpression as a common finding in DTCs and PDTCs, and thus these tumors as possible novel targets for EpCAM-directed immunotherapy. Our findings suggest that patients with recurrent or advanced tumor disease and metastatic spread could benefit from this modern therapeutic regime, especially after insufficient radioiodine therapy.

Transductional targeting of adenovirus vectors for gene therapy

Cancer gene therapy approaches will derive considerable benefit from adenovirus (Ad) vectors capable of self-directed localization to neoplastic disease or immunomodulatory targets in vivo. The ablation of native Ad tropism coupled with active targeting modalities has demonstrated that innate gene delivery efficiency may be retained while circumventing Ad dependence on its primary cellular receptor, the coxsackie and Ad receptor. Herein, we describe advances in Ad targeting that are predicated on a fundamental understanding of vector/cell interplay. Further, we propose strategies by which existing paradigms, such as nanotechnology, may be combined with Ad vectors to form advanced delivery vehicles with multiple functions.

Coxsackie and adenovirus receptor promotes adenocarcinoma cell survival and is expressionally activated after transition from preneoplastic precursor lesions to invasive adenocarcinomas

PURPOSE

The cell adhesion protein, coxsackie and adenovirus receptor (CAR), is differentially expressed in various human adenocarcinomas. We analyzed the role of differential CAR expression during tumorigenesis and in cell survival of adenocarcinomas.

EXPERIMENTAL DESIGN

In a murine mammary cancer model, a syngenic preneoplastic mammary tissue was implanted into the mammary fat pads of syngenic female BALB/c mice. CAR expression was determined by semiquantitative reverse transcription-PCR in the preneoplastic noninvasive precursor lesions and the developing invasive adenocarcinomas. Cell clones overexpressing CAR were generated and tested for their response to apoptotic factors and for the expression of apoptosis relevant proteins by reverse transcription-PCR and Western blot analysis.

RESULTS

In comparison of preneoplastic precursor lesions with established adenocarcinomas, CAR expression was enhanced 2- to 5-fold in all six tissues which had survived and transformed into invasive adenocarcinomas. When stable CAR-overexpressing cell clones of the human cancer cell lines HeLa, CaSki, and A2780 were compared with the parental cell lines, 1.5- to 6-fold more cells survived application of tumor necrosis factor-related apoptosis-inducing ligand or growth factor withdrawal. CAR-enhanced cell survival was accompanied by reduced activation of caspase 3 and enhanced expression of bcl-2 or bcl-XL, depending on the cell type tested. Up-regulation of bcl-2 was found in all CAR-expressing adenocarcinomas of the murine cancer model.

CONCLUSIONS

CAR expression is enhanced after transition from preneoplastic precursor lesions to neoplastic mammary cancer outgrowths. Enhanced CAR expression can promote cancer cell survival. These data suggest differential expression of CAR as a new factor in tumorigenesis.

Overexpression of cathepsin B in gastric cancer identified by proteome analysis

We aimed to validate an analytical approach based on proteomics on gastric cancer specimens for the identification of new putative diagnostic or prognostic markers. Primary screening was performed on gastrectomy specimens obtained from ten consecutive patients with gastric cancer. Gastric epithelial cells were obtained with an epithelial cell enrichment technique, homogenized and then separated by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The differential protein expression pattern was verified stepwise by Western blotting and immunohistochemistry on samples from 28 and 46 cancer patients, respectively. The putative clinical applicability and prognostic use were tested by an enzyme-linked immunoabsorbent assay on serum samples obtained from 149 cancer patients. One hundred-ninety-one differentially expressed protein spots were found by 2-D PAGE and identified by mass spectrometry, including cathepsin B, which was over-expressed in six (60%) patients. Western blotting confirmed that the active form of cathepsin B is over-expressed, while immunohistochemistry showed strong cytoplasmic staining in cancer tissues of 45 (98%) patients. The serum level of cathepsin B was increased in patients with gastric cancer compared to healthy controls (P = 0.0026) and correlated with T-category and the presence of distant metastases (P < 0.05). Serum levels above 129 pmol x L(-1) were associated with a reduced survival rate (P = 0.0297). Proteome analysis is a valuable tool for the identification of prognostic markers in gastric cancer: Increased cathepsin B serum levels are associated with advanced tumor stages and progressive disease, which enables the classification of some gastric cancer patients into a subgroup that should undergo aggressive therapy.

Evaluation of tumor-specific promoter activities in melanoma

Gene therapy is a novel therapy for melanoma. To date, however, there is still no powerful tumor specific promoter (TSP) to restrict the transgene expression in melanoma cells. In order to define a useful TSP for targeting in the context of melanoma gene therapy, four promoters, the cyclooxygenase-2 (Cox-2), alpha-chemokine SDF-1 receptor (CXCR4), epithelial glycoprotein 2 (EGP-2), and survivin, were tested in both established melanoma cell lines and primary melanoma cells. We employed recombinant adenoviral vectors (reAds) each with a candidate TSP (the Cox-2, CXCR4, EGP-2, or survivin), a reporter luciferase gene, and a poly-A signal, all of which were inserted into the E1-deleted region. A reAdGL3Bcytomegalovirus (CMV), containing the CMV promoter and luciferase gene, was used as a positive control to normalize the luciferase activity. Luciferase activity was measured in multiple tumor cell lines and two primary melanoma cell cultures after infection with reAds. Human epithelial melanocytes, HEM, were used as normal control. In contrast to three other promoters, the survivin promoter exhibited the highest activities within both melanoma cell lines and primary melanoma cells, but not in HEMs. Additionally, the survivin promoter exhibited very low activities in major mouse organs including the liver, in vivo. EGP-2 is not active in melanoma; messenger RNA expressions were correlated to promoter activities both in melanoma cell lines and primary cell cultures. Thus, these data suggest that the survivin promoter achieved a 'tumor-on/liver-off' profile, and thus represents a potentially useful tumor-specific promoter with applications for transcriptional targeting of Ad vector-based cancer gene therapy or oncolysis to melanoma.

Expression patterns of potential therapeutic targets in prostate cancer

Androgen withdrawal is the only effective therapy for patients with advanced prostate cancer, but progression to androgen independence ultimately occurs in almost all patients. Novel therapeutic strategies targeting molecular mechanisms that mediate resistance to hormonal and chemotherapeutic treatment are highly warranted. Here, we aimed to evaluate the expression of potential therapeutic targets in advanced prostate cancer. A tissue microarray (TMA) containing samples from 535 tissue blocks was constructed, including benign prostatic hyperplasia as controls (n = 65), prostatic intraepithelial neoplasia (PIN; n = 78), clinically localized prostate cancers (n = 181), as well as hormone-refractory local recurrences (n = 120) and distant metastases (n = 91). The expression of 13 different proteins was analyzed using immunohistochemistry (Bcl-2, p53, ILK, Syndecan-1, MUC-1, EGFR, HER2/neu, HSP-90, Ep-CAM, MMP-2, CD-10, CD-117 and Ki67). Significant overexpression in hormone-refractory prostate cancer and metastatic tissue compared to localized prostate cancer was found for Ki67 (64% vs. 9%), Bcl-2 (11% vs. 1%), p53 (35% vs. 4%), Syndecan-1 (38% vs. 3%), EGFR (16% vs. 1%) and HER2/neu (16% vs. 0%). Overexpression of CD-117 was restricted to 1 single metastasis. All other markers did not show relevant differences in expression between subgroups. Taken together, p53, Bcl-2, Syndecan-1, EGFR and HER2/neu are preferentially expressed in hormone-refractory and metastatic prostate cancer. Selected inhibition of these targets might offer a strategy to treat advanced tumors and prevent further progression. Treatment decisions should not be based on findings in primary tumors but rather on tissues from recurrent or metastatic lesions.

Highly specific transgene expression mediated by a complex adenovirus vector incorporating a prostate-specific amplification feedback loop

Development of novel therapeutic agents is needed to address the problems of locally recurrent, metastatic, and advanced hormone-refractory prostate cancer. We have constructed a novel complex adenovirus (Ad) vector regulation system that incorporates both the prostate-specific ARR2PB promoter and a positive feedback loop using the TRE promoter to enhance gene expression. This regulation strategy involves the incorporation of the TRE upstream of the prostate-specific ARR2PB promoter to enhance its activity with Tet regulation. The expressions of both GFP and tTA were placed under the control of these TRE-ARR2PB promoters, so that in the cells of prostate origin a positive feedback loop would be generated. This design greatly enhanced GFP reporter expression in prostate cancer cells, while retaining tight control of expression in nonprostate cancer cells, even at an MOI as high as 1000. This novel positive feedback loop with prostate specificity (PFLPS) regulation system we have developed may have broad applications for expressing not only high levels of toxic proteins in cancer cells, but alternatively could also be manipulated to regulate essential genes in a highly efficient conditionally replicative adenovirus vector specifically directed to prostate cancer cells. The PFLPS regulation system, therefore, serves as a promising new approach in the development of both a specific and effective vector for cancer gene therapy.

Transcriptional targeting of adenoviral vector through the CXCR4 tumor-specific promoter

Adenoviral vectors are considered to be good gene delivery vectors for cancer gene therapy due to their wide host tissue range and cell cycle-independent infectivity. However, the disadvantages include the lack of specificity for cancer cells and the high liver accumulation in vivo. The human CXCR4 gene is expressed at high levels in many types of cancers, but is repressed in the liver. We explored the CXCR4 promoter as a candidate to restrict adenoviral transgene expression to tumor cells with a low expression in host tissues. The luciferase activities in multiple cancer cell lines infected with recombinant adenovirus reAdGL3BCXCR4 or the control vector reAdGL3BCMV revealed that the CXCR4 promoter exhibited relatively high transcriptional activity in a breast cancer cell line, MDA-MB-361, and two ovarian cancer cell lines, OVCAR-3 and SKOV3. ip1, 65% (P=0.0087), 16.7% (P=0.1) and 20% (P=0.0079) compared to that of the CMV promoter, respectively, and low expression, 4.9 and 0.1%, respectively, in both normal cell lines HFBC and HMEC. In addition, CXCR4 had a low expression of luciferase (0.32%) compared to that of the CMV promoter in mouse liver in vivo. The data also revealed that the CXCR4 promoter was a stronger tumor-specific promoter (TSP) than the Cox-2M promoter in primary melanomas obtained from two patients. The CXCR4 promoter is shown to have a 'tumor-on' and 'liver-off' status in vitro and in vivo, and CXCR4 may prove to be a good candidate TSP for cancer gene therapy approaches for melanoma and breast cancers.

Use of the EGP-2/Ep-CAM promoter for targeted expression of heterologous genes in carcinoma derived cell lines

EGP-2, also known as Ep-CAM, is expressed at high levels on the surface of most carcinomas and is therefore considered an attractive target for anticancer strategies. To explore the mechanisms regulating the expression of EGP-2, sequences 3.4 kb upstream of the transcription start site were isolated and assayed for their ability to control the expression of the EGP-2 cDNA, the green fluorescent protein, the luciferase reporter gene and the thymidine kinase and cytosine deaminase suicide genes. Expression of these chimeric constructs as assessed in a range of different cell lines was restricted to cell lines expressing EGP-2. In addition, only cells expressing EGP-2 were sensitive for gancyclovir after being transiently transfected with EGP-2 promoter-driven thymidine kinase. Deletion analyses defined 687 bp upstream as the basic proximal promoter region, which could confer epithelial-specific expression to the GFP reporter gene in vitro. As these EGP-2 sequences can confer promoter activity to reporter and suicide genes in an EGP-2 restricted manner, they may be useful for gene therapy of EGP-2 expressing carcinomas.

The Coxsackie-Adenovirus Receptor—A New Receptor in the Immunoglobulin Family Involved in Cell Adhesion

The physiological and cell biological aspects of the Coxsackie-Adenovirus Receptor (CAR) is discussed in this review. The receptor obviously recognizes the group C adenoviruses in vivo, but also fibers from other groups except group B in vitro. The latter viruses seem to utilize a different receptor. The receptor accumulates at, or close to, the tight junction in polarized epithelial cells and probably functions as a cell-cell adhesion molecule. The cytoplasmic tail of the receptor is not required for virus attachment and uptake. Although there is a correlation between CAR and uptake of adenoviruses in several human tumor cells, evidence of an absolute requirement for integrins has not been forthcoming. The implication of these findings for adenovirus gene therapy is discussed.

Gene therapy and virotherapy of gastric cancer: preclinical results and clinical developments

Despite advances in current treatment modalities, the clinical outcome of gastric cancer remains dismal. New treatment modalities are urgently required to improve the prognosis of patients with gastric cancer. Cancer gene therapy and virotherapy comprise a potential category of new therapeutics and will be discussed in this review. To date, various gene therapy strategies have been developed, but first clinical trials reported only limited therapeutic efficacy as a result of limited gene transfer efficiency. Consequently, targeted viral vectors for enhanced delivery of transgenes to tumor cells and replicative viral systems designed to replicate selectively in malignant tissue were developed. Replication-selective oncolytic viral vectors have the advantage over non-replicative systems to cause pronounced bystander effect via self-perpetuating infection of adjacent cells after cytolysis of primary targeted cells. So far, clinical studies on virotherapy showed encouraging results; especially promising are combinations of virotherapy with current modes of treatment like chemo- and radiotherapy, or insertion of therapeutic genes in the viral genome such as combination with enzyme-prodrug therapy. Further research aiming to enhance anti-tumor efficacy and to improve selectivity of infection and replication, will eventually lead to full realization of the therapeutic potential of (replicating) viral vector systems for gastric cancer.

Pilot trial of intravenous infusion of a replication-selective adenovirus (ONYX-015) in combination with chemotherapy or IL-2 treatment in refractory cancer patients

ONYX-015 is an adenovirus that selectively replicates in p53 dysfunctional or mutated malignant cells. We performed a pilot trial to determine the safety and feasibility of treatment with ONYX-015 delivered intravenously in patients with advanced malignancy. One cohort of five patients received ONYX-015 once a week for 6 weeks at a dose of 2 x 10(12) particles per infusion in combination with weekly infusions of irinotecan (CPT11, 125 mg per week) and 5-fluorouracil (5FU, 500 mg per week). A second cohort of five patients received the combination of ONYX-015 at a dose of 2 x 10(11) particles per week for 6 weeks in combination with interleukin 2 (IL 2, 1.1 x 10(6) units daily via subcutaneous injection for 5 days each week for 4 weeks). Toxicity attributable to ONYX-015 was limited to transient fever. All patients demonstrated elevations in neutralizing antibody titers within 4 weeks of the infusion of ONYX-015. Serum levels of IL-6, IL-10, tumor necrosis factor-alpha, and interferon-gamma increased within 6 hours of viral infusion, suggesting immune activation. This response was more pronounced in the cohort of patients who received 2 x 10(12) particles per infusion. Two patients demonstrated uptake of viral particles in malignant tissue by quantitative PCR. Electron microscopy confirmed selective cytoplasmic viral particles within malignant cells but not within adjacent normal tissue in a third patient. In conclusion ONYX-015 can be administered safely in combination with CPT11, 5FU or low-dose IL 2 and is able to access malignant tissue following intravenous infusion. Further investigation of ONYX-015, possibly with agents that may modulate replication activity, or duration of virus survival, is indicated.

Targeted cancer gene therapy: the flexibility of adenoviral gene therapy vectors

Recombinant adenoviral vectors are promising reagents for therapeutic interventions in humans, including gene therapy for biologically complex diseases like cancer and cardiovascular diseases. In this regard, the major advantage of adenoviral vectors is their superior in vivo gene transfer efficiency on a wide spectrum of both dividing and non-dividing cell types. However, this broad tropism at the same time represents an important limitation for their use in therapeutic applications where specific gene transfer is required. This limitation may be overcome by using targeting approaches. In this regard, targeting may be achieved at three levels: transductional targeting, translational targeting and targeting of the expressed transgene. Here we describe our research efforts towards cancer specific gene therapy using these different targeting approaches. The results show that targeting of adenoviral vectors may be achieved using cancer specific cell surface molecules for transductional and transgene targeting or cancer specific promoters for transcriptional targeting. Combinations of these targeting approaches should result in optimized cancer specific gene therapy.

Selective gene transfer into primary human gastric tumors using epithelial cell adhesion molecule-targeted adenoviral vectors with ablated native tropism

Currently, application of adenoviral vectors (AdV) in gastric cancer gene therapy would be improved by increases in the specificity of transduction. Previously, we found that epithelial cell adhesion molecule (EpCAM) was expressed on gastric tumors but not on gastric epithelium. In this study, we evaluated doubly-ablated AdV lacking native binding ability together with bispecific single-chain antibodies targeted toward EpCAM for gene therapy of gastric cancer. Specific binding to EpCAM augmented the gene transfer efficiency of doubly-ablated AdV on gastric cancer cell lines up to 144-fold, reaching levels similar to or exceeding those achieved with native AdV. In contrast, EpCAM-targeted doubly-ablated AdV-mediated gene transfer into an EpCAM-negative cell line was reduced 38-fold compared with transduction by native AdV. Most importantly, EpCAM-targeted doubly-ablated AdV showed selectivity for primary human gastric tumors versus the surrounding nonneoplastic gastric mucosa of the same patients and normal liver tissue samples. Targeting these doubly-ablated AdV toward EpCAM resulted in similar transduction efficiency as obtained with native AdV for EpCAM-expressing primary human gastric tumors, whereas transduction of gastric epithelium and liver tissue was reduced at least 10-fold. This study thus indicates that application of EpCAM-targeted doubly-ablated AdV for gastric cancer gene therapy results in a favorable tumor-over-normal tissue transduction ratio.

Epidermal growth factor receptor targeting of replication competent adenovirus enhances cytotoxicity in bladder cancer

PURPOSE

We evaluated the delivery and oncolytic potential of targeted replication competent adenoviruses in bladder cancer lines.

MATERIALS AND METHODS

Seven established human bladder cancer tumor lines (5637, SW800, TCCsup, J82, Scaber, T24 and 253J) were studied for the expression of integrins alpha(v)beta3, alpha(v)beta5, Coxsackievirus and adenovirus receptor, epidermal growth factor receptor (EGF-R) and epithelial cell adhesion molecule antigens using flow cytometry analysis. Bispecific single chain Fv fragments were used to target replication deficient luciferase reporter adenovirus to EGF-R (425-s11) or to epithelial cell adhesion molecule (C28-s11) antigens. Moreover, a fiber modified adenovirus targeting alpha(v)-integrins was studied. Replication competent serotype-5 adenoviruses attenuated to replicate specifically in retinoblastoma pRb (Ad5-d24) or p53 deficient (Ad5-d55K) cells were tested in vitro for oncolytic properties.

RESULTS

Low to absent Coxsackievirus and adenovirus receptor expression was found in 5 of the 7 tumor lines (SW800, J82, T24, 5637 and Scaber). EGF-R expression was found in all cell lines, whereas elevated epithelial cell adhesion molecule expression was seen in 3 (5637, Scaber and TCCsup), alpha(v)beta3-integrin was found in 1 (Scaber) and alpha(v)beta5-integrin was found in 3 (TCCsup, 253J and T24). EGF-R targeting using 425-s11 improved transgene expression in all cell lines from 2.1 to 12.5 times over nontargeted viruses. Epithelial cell adhesion molecule and integrin targeting was inferior to EGF-R targeting with a maximal increase in transgene expression of 2 times for epithelial cell adhesion molecule in 5637cells and 1.6 times for integrin targeting in T24 cells. Comparison of the wild-type replication competent virus with conditionally replicating adenoviruses (Ad5-d55K and Ad5-d24) showed superior oncolytic activity for the latter 2 in all lines. Furthermore, improved cytotoxicity (29% to 33%) was obtained in 4 of the 7 lines after pre-incubation of Ad5-d24 with 425-s11.

CONCLUSIONS

EGF-R directed bispecific single chain antibodies enhance adenovirus mediated transgene expression and oncolysis in bladder cancer lines.

Epidermal growth factor receptor targeting of replication competent adenovirus enhances cytotoxicity in bladder cancer

PURPOSE

We evaluated the delivery and oncolytic potential of targeted replication competent adenoviruses in bladder cancer lines.

MATERIALS AND METHODS

Seven established human bladder cancer tumor lines (5637, SW800, TCCsup, J82, Scaber, T24 and 253J) were studied for the expression of integrins alpha(v)beta3, alpha(v)beta5, Coxsackievirus and adenovirus receptor, epidermal growth factor receptor (EGF-R) and epithelial cell adhesion molecule antigens using flow cytometry analysis. Bispecific single chain Fv fragments were used to target replication deficient luciferase reporter adenovirus to EGF-R (425-s11) or to epithelial cell adhesion molecule (C28-s11) antigens. Moreover, a fiber modified adenovirus targeting alpha(v)-integrins was studied. Replication competent serotype-5 adenoviruses attenuated to replicate specifically in retinoblastoma pRb (Ad5-d24) or p53 deficient (Ad5-d55K) cells were tested in vitro for oncolytic properties.

RESULTS

Low to absent Coxsackievirus and adenovirus receptor expression was found in 5 of the 7 tumor lines (SW800, J82, T24, 5637 and Scaber). EGF-R expression was found in all cell lines, whereas elevated epithelial cell adhesion molecule expression was seen in 3 (5637, Scaber and TCCsup), alpha(v)beta3-integrin was found in 1 (Scaber) and alpha(v)beta5-integrin was found in 3 (TCCsup, 253J and T24). EGF-R targeting using 425-s11 improved transgene expression in all cell lines from 2.1 to 12.5 times over nontargeted viruses. Epithelial cell adhesion molecule and integrin targeting was inferior to EGF-R targeting with a maximal increase in transgene expression of 2 times for epithelial cell adhesion molecule in 5637cells and 1.6 times for integrin targeting in T24 cells. Comparison of the wild-type replication competent virus with conditionally replicating adenoviruses (Ad5-d55K and Ad5-d24) showed superior oncolytic activity for the latter 2 in all lines. Furthermore, improved cytotoxicity (29% to 33%) was obtained in 4 of the 7 lines after pre-incubation of Ad5-d24 with 425-s11.

CONCLUSIONS

EGF-R directed bispecific single chain antibodies enhance adenovirus mediated transgene expression and oncolysis in bladder cancer lines.

Targeted adenoviral vectors

Replication-defective vectors based on human adenovirus serotypes 2 and 5 (Ad2 and Ad5) possess a number of attributes which favor their use as gene delivery vehicles in gene therapy applications. However, the widespread distribution of the primary cellular receptor for Ad, the coxsackievirus and adenovirus receptor (CAR), allows Ad vectors to infect a broad range of cells in the host. Conversely, a number of tissues which represent important targets for gene therapy, such as the airway epithelium and cancer cells, are refractory to Ad infection due a paucity of CAR. Thus, there is a strong rationale for the development of CAR-independent Ad vectors capable of enhanced specificity and efficiency of gene transfer to target cells. In this article we review the approaches which have been employed to generate tropism-modified Ad vectors. These targeting strategies have led to improvements in the safety and efficacy of Ad vectors and have the potential to yield an increased therapeutic benefit in the human clinical context.

Spectrum of genetic changes in gastro-esophageal cancer cell lines determined by an integrated molecular cytogenetic approach

Adenocarcinomas arising around the gastro-esophageal junction (GEJ) are highly malignant, and their incidence has risen rapidly in the last decades. Cell lines are the basic in vitro system for functional and therapeutic studies in GEJ tumors, but only a small number of cell lines are currently available, and none of them has been fully karyotyped. We analyzed 5 GEJ tumor cell lines using a combination of 24-color fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH) and genomic microarrays. Using CGH we demonstrated that these cell lines present imbalances similar to those we had previously observed in primary GEJ tumors, namely gains on 1q, 7q, 8q, 17q, 19q, 20, and X, and losses on 3p, 4, 5q, 9p, 18q, and 21. Multicolor FISH karyotyping revealed multiple structural rearrangements involving chromosomes 1, 5, 6, 7, 8, 9, 13, 17, 18, and 22. Rearrangements of chromosome 8 involved 10 different chromosomes, while rearrangements of chromosome 17 involved 5. Different rearrangements resulted in imbalances of similar chromosome regions, suggesting that similar genomic imbalances are constitutively important but are achieved through different pathways. The use of a commercially available genomic array excluded TOP2A (17q), and MYBL2, PTPT1, CSE1L, and ZNF217 (20q) as candidate genes for frequently amplified areas on these chromosomes, and contributed to refining the limits of chromosome regions involved in genomic imbalances.