Tissue-specific gene therapy directed to tumor angiogenesis

Tumor-Associated Macrophages/Microglia in Glioblastoma Oncolytic Virotherapy: A Double-Edged Sword

Oncolytic virotherapy is a rapidly progressing field that uses oncolytic viruses (OVs) to selectively infect malignant cells and cause an antitumor response through direct oncolysis and stimulation of the immune system. Despite demonstrated pre-clinical efficacy of OVs in many cancer types and some favorable clinical results in glioblastoma (GBM) trials, durable increases in overall survival have remained elusive. Recent evidence has emerged that tumor-associated macrophage/microglia (TAM) involvement is likely an important factor contributing to OV treatment failure. It is prudent to note that the relationship between TAMs and OV therapy failures is complex. Canonically activated TAMs (i.e., M1) drive an antitumor response while also inhibiting OV replication and spread. Meanwhile, M2 activated TAMs facilitate an immunosuppressive microenvironment thereby indirectly promoting tumor growth. In this focused review, we discuss the complicated interplay between TAMs and OV therapies in GBM. We review past studies that aimed to maximize effectiveness through immune system modulation-both immunostimulatory and immunosuppressant-and suggest future directions to maximize OV efficacy.

A randomized controlled phase III study of VB-111 combined with bevacizumab vs bevacizumab monotherapy in patients with recurrent glioblastoma (GLOBE)

Background

Ofranergene obadenovec (VB-111) is an anticancer viral therapy that demonstrated in a phase II study a survival benefit for patients with recurrent glioblastoma (rGBM) who were primed with VB-111 monotherapy that was continued after progression with concomitant bevacizumab.

Methods

This pivotal phase III randomized, controlled trial compared the efficacy and safety of upfront combination of VB-111 and bevacizumab versus bevacizumab monotherapy. Patients were randomized 1:1 to receive VB-111 10¹³ viral particles every 8 weeks in combination with bevacizumab 10 mg/kg every 2 weeks (combination arm) or bevacizumab monotherapy (control arm). The primary endpoint was overall survival (OS), and secondary endpoints were objective response rate (ORR) by Response Assessment in Neuro-Oncology (RANO) criteria and progression-free survival (PFS).

Results

Enrolled were 256 patients at 57 sites. Median exposure to VB-111 was 4 months. The study did not meet its primary or secondary goals. Median OS was 6.8 versus 7.9 months in the combination versus control arm (hazard ratio, 1.20; 95% CI: 0.91–1.59; P = 0.19) and ORR was 27.3% versus 21.9% (P = 0.26). A higher rate of grades 3–5 adverse events was reported in the combination arm (67% vs 40%), mainly attributed to a higher rate of CNS and flu-like/fever events. Trends for improved survival with combination treatment were seen in the subgroup of patients with smaller tumors and in patients who had a posttreatment febrile reaction.

Conclusions

In this study, upfront concomitant administration of VB-111 and bevacizumab failed to improve outcomes in rGBM. Change of treatment regimen, with the lack of VB-111 monotherapy priming, may explain the differences from the favorable phase II results.

Clinical trials registration

NCT02511405

Utilizing an interim futility analysis of the OVAL study (VB-111-701/GOG 3018) for potential reduction of risk: A phase III, double blind, randomized controlled trial of ofranergene obadenovec (VB-111) and weekly paclitaxel in patients with platinum resistant ovarian cancer

OBJECTIVE

Report the results from a preplanned interim analysis of a phase III, double blind, randomized controlled study of ofranergene obadenovec (VB-111), a targeted anti-cancer gene therapy, in combination with paclitaxel in patients with platinum resistant ovarian cancer (PROC).

METHODS

The OVAL (NCT03398655) study is an on-going study where patients are randomly assigned in a 1:1 ratio to weekly paclitaxel 80 mg/m² with VB-111 or placebo. The protocol specifies a pre-planned unblinded futility interim analysis of CA-125 response per GCIG criteria in the first 60 evaluable patients. The futility rule determined for this analysis was that the response rate of VB-111 must be greater than the response rate of placebo by at least 10% in order to continue the study. Coincident with the interim analysis, the blinded CA-125 response rate was estimated as a proportion of the first 60 evaluable patients with CA-125 response per GCIG criteria. Post-treatment fever is provided as a possible surrogate marker of VB-111 therapy activity.

RESULTS

The median age of the evaluable patients was 62 years (range 41-82); 97% had high-grade serous cancer; 58% had been treated with 3 or more previous lines of therapy, 70% received prior anti-angiogenic treatment, 43% received prior PARP inhibitors. CA-125 response in the VB-111 and weekly paclitaxel treated arm met the pre-specified interim criterion of an absolute advantage of 10% or higher compared to the control. Blinded results show a 53% CA-125 response rate (32/60) with 15% complete response (n=9). Assuming balanced randomization and an absolute advantage of 10% or higher to the VB-111 arm, it may be deducted that the response in the VB-111 treatment arm is 58% or higher. Among patients with post-treatment fever, the CA-125 response rate was 69%.

CONCLUSIONS

At the time of the interim analysis, response rate findings are comparable to the responses seen in a similar patient population in the phase I/II study. The independent data and safety monitoring committee (iDSMC) recommended continuing the OVAL trial as planned. No new safety signals were identified.

Effects of oncolytic viruses and viral vectors on immunity in glioblastoma

Glioblastoma (GBM) is regarded as an incurable disease due to its poor prognosis and limited treatment options. Virotherapies were once utilized on cancers for their oncolytic effects. And they are being revived on GBM treatment, as accumulating evidence presents the immunogenic effects of virotherapies in remodeling immunosuppressive GBM microenvironment. In this review, we focus on the immune responses induced by oncolytic virotherapies and viral vectors in GBM. The current developments of GBM virotherapies are briefly summarized, followed by a detailed depiction of their immune response. Limitations and lessons inferred from earlier experiments and trials are discussed. Moreover, we highlight the importance of engaging the immune responses induced by virotherapies into the multidisciplinary management of GBM.

Safety and efficacy of VB-111, an anticancer gene therapy, in patients with recurrent glioblastoma: results of a phase I/II study

BACKGROUND

VB-111 is a non-replicating adenovirus carrying a Fas-chimera transgene, leading to targeted apoptosis of tumor vascular endothelium and induction of a tumor-specific immune response. This phase I/II study evaluated the safety, tolerability, and efficacy of VB-111 with and without bevacizumab in recurrent glioblastoma (rGBM).

METHODS

Patients with rGBM (n = 72) received VB-111 in 4 treatment groups: subtherapeutic (VB-111 dose escalation), limited exposure (LE; VB-111 monotherapy until progression), primed combination (VB-111 monotherapy continued upon progression with combination of bevacizumab), and unprimed combination (upfront combination of VB-111 and bevacizumab). The primary endpoint was median overall survival (OS). Secondary endpoints were safety, overall response rate, and progression-free survival (PFS).

RESULTS

VB-111 was well tolerated. The most common adverse event was transient mild-moderate fever. Median OS time was significantly longer in the primed combination group compared with both LE (414 vs 223 days; hazard ratio [HR], 0.48; P = 0.043) and unprimed combination (414 vs 141.5 days; HR, 0.24; P = 0.0056). Patients in the combination phase of the primed combination group had a median PFS time of 90 days compared with 60 in the LE group (HR, 0.36; P = 0.032), and 63 in the unprimed combination group (P = 0.72). Radiographic responders to VB-111 exhibited characteristic, expansive areas of necrosis in the areas of initial enhancing disease.

CONCLUSIONS

Patients with rGBM who were primed with VB-111 monotherapy that continued after progression with the addition of bevacizumab showed significant survival and PFS advantage, as well as specific imaging characteristics related to VB-111 mechanism of action. These results warrant further assessment in a randomized controlled study.

Ofranergene obadenovec (VB-111) in platinum-resistant ovarian cancer; favorable response rates in a phase I/II study are associated with an immunotherapeutic effect

OBJECTIVE

Report final results of a phase I/II study of VB-111, a targeted anti-cancer gene therapy with a dual mechanism: anti angiogenic/vascular disruption and induction of an anti-tumor directed immune response, in combination with paclitaxel in patients with platinum-resistant ovarian cancer.

METHODS

Study NCT01711970 was a prospective, open label, dose escalation study assessing combination treatment of VB-111 and weekly paclitaxel. In the Phase I part of the study, patients were treated with escalating doses of intravenous VB-111 and paclitaxel. In Phase 2, patients were treated with therapeutic doses of VB-111 and paclitaxel 80 mg/m². Assessments included safety, overall survival (OS), progression free survival (PFS), and tumor response (CA-125 and RECIST).

RESULTS

21 patients with recurrent platinum-resistant ovarian cancer were enrolled. 17/21 received the therapeutic dose. Patients had a median of 3 prior lines of therapy. Half of the subjects were platinum refractory, and half were previously treated with antiangiogenics. No DLTs were observed. VB-111 was well tolerated and associated with mild flu-like symptoms. In the therapeutic dose cohort, a 58% CA-125 GCIG response rate was seen in evaluable patients. The median OS was 16.6 months in patients treated with therapeutic dose compared to 5.8 months in sub-therapeutic dose (p = 0.028). Tumor specimens taken after treatment demonstrated tumor infiltrated with cytotoxic CD8 T-cells in regions of apoptotic cancer cells.

CONCLUSIONS

Treatment with VB-111 in combination with paclitaxel was safe and well tolerated. Favorable tumor responses and overall survival outcomes were associated with induction of an immunotherapeutic effect.

Specific overexpression of 15-lipoxygenase in endothelial cells promotes cancer cell death in an in vivo Lewis lung carcinoma mouse model

PURPOSE

Lipoxygenases (LOX) have been implicated in carcinogenesis, however both pro- and anti-carcinogenic effects have been reported in different cancer models. Using transgenic mice, which specifically overexpress human 15-lipoxygenase (ALOX15) in endothelial cells (EC), we previously demonstrated significant inhibition of tumor development. In the Lewis lung carcinoma (LLC) model, the primary tumor developed similarly in both wild type (WT) and ALOX15 overexpressing mice. However, metastases development was significantly inhibited in the transgenic mice. Here, we explored the molecular basis for the anti-metastatic effect of endothelial cell specific ALOX15 overexpression.

MATERIALS/METHODS

We used ALOX15 overexpressing mice, and in-vitro cell model to evaluate the molecular effect of ALOX15 on EC and LLC cells.

RESULTS

When LLC cells were injected in WT and ALOX15 overexpressing mice, we observed a higher degree of apoptosis and necrosis in primary and metastatic tumors of ALOX15 overexpressing animals. These anti-carcinogenic and anti-metastatic effects were paralleled by augmented expression of cyclin-dependent kinase inhibitor 1A (CDKN1A; p21) and of the peroxisome proliferators-activated receptor (PPAR)γ and by downregulation of the steady state concentrations of connexin26 mRNA. Consistent with these in vivo effects, ALOX15 overexpression in LLC and HeLa cancer cells in vitro significantly reduced cell viability in culture. In contrast, similar treatment of non-cancerous B2B epithelial cells did not impact cell viability.

CONCLUSIONS

Taken together, our data suggests that endothelial cell specific overexpression of ALOX15 promotes apoptosis and necrosis in primary and metastatic tumors in mice, by upregulation of P21 and PPARγ expression in adjacent cancer cells.

Liver to Pancreas Transdifferentiation

PURPOSE OF THE REVIEW

Here, we review recent findings in the field of generating insulin-producing cells by pancreatic transcription factor (pTF)-induced liver transdifferentiation (TD). TD is the direct conversion of functional cell types from one lineage to another without passing through an intermediate stage of pluripotency. We address potential reasons for the restricted efficiency of TD and suggest modalities to overcome these challenges, to bring TD closer to its clinical implementation in autologous cell replacement therapy for insulin-dependent diabetes.

RECENT FINDINGS

Liver to pancreas TD is restricted to cells that are a priori predisposed to undergo the developmental process. In vivo, the predisposition of liver cells is affected by liver zonation and hepatic regeneration. The TD propensity of liver cells is related to permissive epigenome which could be extended to TD-resistant cells by specific soluble factors. An obligatory role for active Wnt signaling in continuously maintaining a "permissive" epigenome is suggested. Moreover, the restoration of the pancreatic niche and vasculature promotes the maturation of TD cells along the β cell function. Future studies on liver to pancreas TD should include the maturation of TD cells by 3D culture, the restoration of vasculature and the pancreatic niche, and the extension of TD propensity to TD-resistant cells by epigenetic modifications. Liver to pancreas TD is expected to result in the generation of custom-made "self" surrogate β cells for curing diabetes.

Radioiodine refractory differentiated thyroid cancer

Differentiated thyroid cancer (DTC) is usually curable with surgery, radioactive iodine (RAI), and thyroid-stimulating hormone (TSH) suppression. However, local recurrence and/or distant metastases occur in approximately 15% of cases during follow-up, and nearly two-thirds of these patients will become RAI-refractory (RR-DTC) with a poor prognosis. This review focuses on the most challenging and rapidly evolving aspects of RR-DTC, and we discuss the considerable improvement in more accurately defining RR-DTC, more effective therapeutic strategies, and describe the diagnosis, pathogenesis, and future prospects of RR-DTC. Along with the detection of serum thyroglobulin and anatomic imaging modalities, such as ultrasound and computer tomography, radionuclide molecular imaging plays a vital role in the evaluation of RR-DTC. In addition, continual progress has been made in the management of RR-DTC, including watchful waiting under appropriate TSH suppression, local treatment approaches, and systemic therapies (molecular targeted therapy, redifferentiation therapy, gene therapy, and cancer immunotherapy). These all hold promise to change the natural history of RR-DTC.

Regulation of the hypoxic tumor environment in hepatocellular carcinoma using RNA interference

Objectives

Hypoxia is the condition where tumor cells have been deprived of oxygen and has been shown to have a role of tumor development in the hepatocellular carcinoma (HCC).

Methods

Using PubMed online database and Google scholar web site, the terms “angiogenesis”, “apoptosis”, “RNA interference” and/or “hepatocellular carcinoma (HCC)” were searched and analyzed.

Results

The hypoxia inducible factors (HIFs) are transcriptional regulators that affect a homeostatic response to oxidative stress and have been identified as a key transcription activator of angiogenesis, survival, and metabolism. Cytokines, such as IL-8, also controlled endothelia cells survival and angiogenesis. IL-8 was also overexpressed under hypoxia and induced tumor angiogenesis and growth.

Conclusion

Therefore, regulation of HIFs and IL-8 controlled the tumor microenvironment in terms of tumor angiogenesis and apoptosis. The review summarizes the results of regulation of the hypoxic tumor environment.

VB-111: a novel anti-vascular therapeutic for glioblastoma multiforme

Glioblastoma multiforme (GBM) is among the most highly vascularized of solid tumors, contributing to the infiltrative nature of the disease, and conferring poor outcome. Due to the critical dependency of GBM on growth of new endothelial vasculature, we evaluated the preclinical activity of a novel adenoviral gene therapy that targets the endothelium within newly formed blood vessels for apoptosis. VB-111, currently in phase II clinical trials, consists of a non-replicating Adenovirus 5 (El deleted) carrying a proapoptotic human Fas-chimera (transgene) under the control of a modified murine promoter (PPE-1-3×) which specifically targets endothelial cells within the tumor vasculature. Here we report that a single intravenous dose of 2.5 × 10(11) or 1 × 10(11) VPs was sufficient to extend survival in nude rats bearing U87MG-luc2 or nude mice bearing U251-luc, respectively. Bioluminescence imaging of nude rats showed that VB-111 effectively inhibited tumor growth within four weeks of treatment. This was confirmed in a select group of animals by MRI. In our mouse model we observed that 3 of 10 nude mice treated with VB-111 completely lost U251 luciferase signal and were considered long term survivors. To assess the antiangiogenic effects of VB-111, we evaluated the tumor-associated microvaculature by CD31, a common marker of neovascularization, and found a significant decrease in the microvessel density by IHC. We further assessed the neovasculature by confocal microscopy and found that VB-111 inhibits vascular density in two separate mouse models bearing U251-RFP xenografts. Collectively, this study supports the clinical development of VB-111 as a treatment for GBM.

The temporal and hierarchical control of transcription factors-induced liver to pancreas transdifferentiation

Lineage-specific transcription factors (TFs) display instructive roles in directly reprogramming adult cells into alternate developmental fates, in a process known as transdifferentiation. The present study analyses the hypothesis that despite being fast, transdifferentiation does not occur in one step but is rather a consecutive and hierarchical process. Using ectopic expression of Pdx1 in human liver cells, we demonstrate that while glugacon and somatostatin expression initiates within a day, insulin gene expression becomes evident only 2–3 days later. To both increase transdifferentiation efficiency and analyze whether the process indeed display consecutive and hierarchical characteristics, adult human liver cells were treated by three pancreatic transcription factors, Pdx1, Pax4 and Mafa (3pTFs) that control distinct hierarchical stages of pancreatic development in the embryo. Ectopic expression of the 3pTFs in human liver cells, increased the transdifferentiation yield, manifested by 300% increase in the number of insulin positive cells, compared to each of the ectopic factors alone. However, only when the 3pTFs were sequentially supplemented one day apart from each other in a direct hierarchical manner, the transdifferentiated cells displayed increased mature β-cell-like characteristics. Ectopic expression of Pdx1 followed by Pax4 on the 2^nd day and concluded by Mafa on the 3^rd day resulted in increased yield of transdifferentiation that was associated by increased glucose regulated c-peptide secretion. By contrast, concerted or sequential administration of the ectopic 3pTFs in an indirect hierarchical mode resulted in the generation of insulin and somatostatin co-producing cells and diminished glucose regulated processed insulin secretion. In conclusion transcription factors induced liver to pancreas transdifferentiation is a progressive and hierarchical process. It is reasonable to assume that this characteristic is general to wide ranges of tissues. Therefore, our findings could facilitate the development of cell replacement therapy modalities for many degenerative diseases including diabetes.

The temporal and hierarchical control of transcription factors-induced liver to pancreas transdifferentiation

Lineage-specific transcription factors (TFs) display instructive roles in directly reprogramming adult cells into alternate developmental fates, in a process known as transdifferentiation. The present study analyses the hypothesis that despite being fast, transdifferentiation does not occur in one step but is rather a consecutive and hierarchical process. Using ectopic expression of Pdx1 in human liver cells, we demonstrate that while glucagon and somatostatin expression initiates within a day, insulin gene expression becomes evident only 2-3 days later. To both increase transdifferentiation efficiency and analyze whether the process indeed display consecutive and hierarchical characteristics, adult human liver cells were treated by three pancreatic transcription factors, Pdx1, Pax4 and Mafa (3pTFs) that control distinct hierarchical stages of pancreatic development in the embryo. Ectopic expression of the 3pTFs in human liver cells, increased the transdifferentiation yield, manifested by 300% increase in the number of insulin positive cells, compared to each of the ectopic factors alone. However, only when the 3pTFs were sequentially supplemented one day apart from each other in a direct hierarchical manner, the transdifferentiated cells displayed increased mature β-cell-like characteristics. Ectopic expression of Pdx1 followed by Pax4 on the 2(nd) day and concluded by Mafa on the 3(rd) day resulted in increased yield of transdifferentiation that was associated by increased glucose regulated c-peptide secretion. By contrast, concerted or sequential administration of the ectopic 3pTFs in an indirect hierarchical mode resulted in the generation of insulin and somatostatin co-producing cells and diminished glucose regulated processed insulin secretion. In conclusion transcription factors induced liver to pancreas transdifferentiation is a progressive and hierarchical process. It is reasonable to assume that this characteristic is general to wide ranges of tissues. Therefore, our findings could facilitate the development of cell replacement therapy modalities for many degenerative diseases including diabetes.

Transcriptional targeting of primary and metastatic tumor neovasculature by an adenoviral type 5 roundabout4 vector in mice

New approaches targeting metastatic neovasculature are needed. Payload capacity, cellular transduction efficiency, and first-pass cellular uptake following systemic vector administration, motivates persistent interest in tumor vascular endothelial cell (EC) adenoviral (Ad) vector targeting. While EC transductional and transcriptional targeting has been accomplished, vector administration approaches of limited clinical utility, lack of tumor-wide EC expression quantification, and failure to address avid liver sequestration, challenged prior work. Here, we intravenously injected an Ad vector containing 3 kb of the human roundabout4 (ROBO4) enhancer/promoter transcriptionally regulating an enhanced green fluorescent protein (EGFP) reporter into immunodeficient mice bearing 786-O renal cell carcinoma subcutaneous (SC) xenografts and kidney orthotopic (KO) tumors. Initial experiments performed in human coxsackie virus and adenovirus receptor (hCAR) transgenic:Rag2 knockout mice revealed multiple ECs with high-level Ad5ROBO4-EGFP expression throughout KO and SC tumors. In contrast, Ad5CMV-EGFP was sporadically expressed in a few tumor vascular ECs and stromal cells. As the hCAR transgene also facilitated Ad5ROBO4 and control Ad5CMV vector EC expression in multiple host organs, follow-on experiments engaged warfarin-mediated liver vector detargeting in hCAR non-transgenic mice. Ad5ROBO4-mediated EC expression was undetectable in most host organs, while the frequencies of vector expressing intratumoral vessels and whole tumor EGFP protein levels remained elevated. In contrast, AdCMV vector expression was only detectable in one or two stromal cells throughout the whole tumor. The Ad5ROBO4 vector, in conjunction with liver detargeting, provides tractable genetic access for in-vivo EC genetic engineering in malignancies.

Adenoviral transduction of human acid sphingomyelinase into neo-angiogenic endothelium radiosensitizes tumor cure

These studies define a new mechanism-based approach to radiosensitize tumor cure by single dose radiotherapy (SDRT). Published evidence indicates that SDRT induces acute microvascular endothelial apoptosis initiated via acid sphingomyelinase (ASMase) translocation to the external plasma membrane. Ensuing microvascular damage regulates radiation lethality of tumor stem cell clonogens to effect tumor cure. Based on this biology, we engineered an ASMase-producing vector consisting of a modified pre-proendothelin-1 promoter, PPE1(3x), and a hypoxia-inducible dual-binding HIF-2α-Ets-1 enhancer element upstream of the asmase gene, inserted into a replication-deficient adenovirus yielding the vector Ad5H2E-PPE1(3x)-ASMase. This vector confers ASMase over-expression in cycling angiogenic endothelium in vitro and within tumors in vivo, with no detectable enhancement in endothelium of normal tissues that exhibit a minute fraction of cycling cells or in non-endothelial tumor or normal tissue cells. Intravenous pretreatment with Ad5H2E-PPE1(3x)-ASMase markedly increases SDRT cure of inherently radiosensitive MCA/129 fibrosarcomas, and converts radiation-incurable B16 melanomas into biopsy-proven tumor cures. In contrast, Ad5H2E-PPE1(3x)-ASMase treatment did not impact radiation damage to small intestinal crypts as non-dividing small intestinal microvessels did not overexpress ASMase and were not radiosensitized. We posit that combination of genetic up-regulation of tumor microvascular ASMase and SDRT provides therapeutic options for currently radiation-incurable human tumors.

Phase I dose-escalation study of VB-111, an antiangiogenic virotherapy, in patients with advanced solid tumors

PURPOSE

VB-111 is an antiangiogenic agent consisting of a nonreplicating adenovirus vector (Ad-5) with a modified murine pre-proendothelin promoter leading to apoptosis of tumor vasculature by expressing a Fas-chimera transgene in angiogenic endothelial cells. In a phase I dose-escalation study, pharmacokinetics, pharmacodynamics, safety, and efficacy of a single dose of VB-111 in patients with advanced solid tumors were evaluated.

EXPERIMENTAL DESIGN

VB-111 was administered as a single i.v. infusion at escalating doses from 1 × 10(10) (cohort 1) to 1 × 10(13) (cohort 7) viral particles (VP) in successive cohorts. Assessments included pharmacokinetic and pharmacodynamic profiles, tumor response, and overall survival.

RESULTS

Thirty-three patients were enrolled. VB-111 was safe and well-tolerated; self-limited fever and chills were seen at doses above 3 × 10(11) VPs. Transgene expression was not detected in blood but was detected in an aspirate from a subcutaneous metastasis after treatment. One patient with papillary thyroid carcinoma had a partial response.

CONCLUSIONS

VB-111 was safe and well tolerated in patients with advanced metastatic cancer at a single administration of up to 1 × 10(13) VPs. Evidence of transgene expression in tumor tissue and tumor response was observed.

Reduction of experimental diabetic vascular leakage and pericyte apoptosis in mice by delivery of αA-crystallin with a recombinant adenovirus

AIMS/HYPOTHESIS

The study aimed to evaluate the efficacy of recombinant adenovirus expressing αA-crystallin (Ad-αAc-Gfp) in reducing pericyte loss within retinal vasculature in early diabetes.

METHODS

Diabetes was induced by streptozotocin injection into C57BL/6 mice. Ad-αAc-Gfp was delivered by intravitreous injection to the right eyes of mice 2 weeks before induction of diabetes. Vascular leakage was determined by fluorescent angiography, Evans Blue leakage assay and leucocyte adhesion test. Production of αA-crystallin was analysed by immunoblotting and double immunostaining and pericyte loss was analysed by pericyte count.

RESULTS

Vessel leakage and pericyte loss were observed in the streptozotocin-induced diabetic retina. Decreased abundance of αA-crystallin in retinas 2 and 6 months after the induction of diabetes was confirmed by two-dimensional electrophoretic analysis, immunoblotting and RT-PCR. Double immunofluorescence staining for αA-crystallin and NG2 chondroitin sulphate proteoglycan revealed that αA-crystallin was predominantly produced in the retinal pericyte and that the number of αA-crystallin-producing pericytes decreased in the diabetic retina. Retinal infection with Ad-αAc-Gfp led to decreased pericyte loss and vascular leakage compared with control.

CONCLUSIONS/INTERPRETATION

Intravitreal delivery of Ad-αAc-Gfp protects against vascular leakage in the streptozotocin-induced model of diabetes. This effect is associated with the inhibition of diabetic retinal pericyte loss in early diabetes, suggesting that αA-crystallin has a role in preventing the pathogenesis of early diabetic retinopathy.

Antitumor Activity of VB-111, a Novel Antiangiogenic Virotherapeutic, in Thyroid Cancer Xenograft Mouse Models

VB-111 is an engineered antiangiogenic adenovirus that expresses Fas-c in angiogenic blood vessels and has previously been shown to have significant antitumor activity in vitro and in vivo in Lewis lung carcinoma, melanoma, and glioblastoma models. To evaluate the efficacy of VB-111 in thyroid cancer, we conducted in vivo xenograft nude mouse studies using multiple thyroid cancer-derived cell lines models. VB-111 treatment resulted in 26.6% (P = 0.0596), 34.4% (P = 0.0046), and 37.6% (P = 0.0249) inhibition of tumor growth in follicular, papillary and anaplastic thyroid cancer models, respectively. No toxicity was observed in any model. All tumor types showed a consistent and significant reduction of CD-31 staining (P < 0.05), reflecting a reduction of angiogenic activity in the tumors, consistent with the intended targeting of the virus. A phase 2 clinical trial of VB-111 in patients with advanced differentiated thyroid cancer is ongoing.

Construction of a novel expression cassette for increasing transgene expression in vivo in endothelial cells of large blood vessels

The success of gene therapy hinges on achievement of adequate transgene expression. To ensure high transgene expression, many gene-therapy vectors include highly active virus-derived transcriptional elements. Other vectors include tissue-specific eukaryotic transcriptional elements, intended to limit transgene expression to specific cell types, avoid toxicity and prevent immune responses. Unfortunately, tissue specificity is often accompanied by lower transgene expression. Here, we use eukaryotic (murine) transcriptional elements and a virus-derived posttranscriptional element to build cassettes designed to express a potentially therapeutic gene (interleukin (IL)-10) in large-vessel endothelial cells (ECs) at levels as high as obtained with the cytomegalovirus (CMV) immediate early promoter, while retaining EC specificity. The cassettes were tested by incorporation into helper-dependent adenoviral vectors, and transduction into bovine aortic EC in vitro and rabbit carotid EC in vivo. The murine endothelin-1 promoter showed EC specificity, but expressed only 3% as much IL-10 mRNA as CMV. Inclusion of precisely four copies of an EC-specific enhancer and a posttranscriptional regulatory element increased IL-10 expression to a level at or above the CMV promoter in vivo, while retaining--and possibly enhancing--EC specificity, as measured in vitro. The cassette reported here will likely be useful for maximizing transgene expression in large-vessel EC, while minimizing systemic effects.

Endothelial lineage cell as a vehicle for systemic delivery of cancer gene therapy

A major limitation of cancer gene therapy is the difficulty of delivering a therapeutic gene to distant sites of metastatic disease. A promising strategy to address this difficulty is to use expanded ex vivo cells to produce a therapeutic protein. As with other approaches to gene therapy, this strategy is attractive when the therapeutic protein is unstable ex vivo or has a short circulating half life in vivo. The initial step to develop a cancer gene therapy using autologous cell delivery is the identification of a cell type that migrates to the tumor site, is readily available for harvesting, and is manipulated easily ex vivo. Recent evidence suggests that endothelial progenitor, precursor, and blood outgrowth endothelial cells are attracted to the tumor vasculature by its angiogenic drive. Here, we review recent advances in the study of circulating endothelial cell-mediated tumor vasculogenesis and discuss the advantages and challenges of bringing endothelial lineage-based cancer gene therapy closer to clinical application.

Immuno- and gene-therapeutic strategies targeted against cancer (mainly focusing on pancreatic cancer)

Current treatment modalities of surgical resection and chemotherapy against cancers have improved survival. However, mortality from tumor recurrence remains high. Immunotherapy and gene therapy are potential additions to the treatment arsenal in the care of cancer patients. These novel therapeutic approaches need further investigation in in vitro and in vivo models as they are developed for potential use in humans. Here we reviewed immunotherapies and gene therapies that included clinical trials against cancers (mainly focusing on pancreatic cancer) suggesting the strong possibility of using these novel approaches.

Strategies for targeting tumors and tumor vasculature for cancer therapy

Effective cancer therapy remains a challenge despite recent advances in the identification of novel targets. A major limitation of most chemotherapeutic drugs is their systemic toxicity and the efficacy of cancer treatments is, by and large, determined by the ability to balance their benefits against their toxicity. Targeted treatments for cancer, especially those that target the tumor vasculature, have provided promising antitumor results with minimal systemic toxicity. To date significant progress has been made in developing a variety of delivery systems to target cancer and its vasculature ranging from isolated limb and organ perfusion to tumor targeted biological and nonbiological vectors.

Transcriptional targeting of tumor endothelial cells for gene therapy

It is well known that angiogenesis plays a critical role in the pathobiology of tumors. Recent clinical trials have shown that inhibition of angiogenesis can be an effective therapeutic strategy for patients with cancer. However, one of the outstanding issues in anti-angiogenic treatment for cancer is the development of toxicities related to off-target effects of drugs. Transcriptional targeting of tumor endothelial cells involves the use of specific promoters for selective expression of therapeutic genes in the endothelial cells lining the blood vessels of tumors. Recently, several genes that are expressed specifically in tumor-associated endothelial cells have been identified and characterized. These discoveries have enhanced the prospectus of transcriptionally targeting tumor endothelial cells for cancer gene therapy. In this manuscript, we review the promoters, vectors, and therapeutic genes that have been used for transcriptional targeting of tumor endothelial cells, and discuss the prospects of such approaches for cancer gene therapy.

The targeting expression of the vascular endothelial growth factor gene in endothelial cells regulated by HRE.ppET-1

The success of gene therapy depends largely on the efficacy of gene delivery vector systems that can deliver genes to target organs or cells selectively and efficiently with minimal toxicity. Here, we show that by using the HRE.ppET-1 regulatory element, we were able to restrict expression of the transgene of vascular endothelial growth factor (VEGF) to endothelial cells exclusively in hypoxic conditions. Eukaryotic expression vectors such as pEGFP-HRE.ppET-1, pcDNA3.1-VEGF+Pa, pcDNA3.1-ppET-1+ EGF+Pa, and pcDNA3.1-HRE.ppET-1+VEGF+Pa were constructed by using a series of nuclear molecule handling methods like PCR, enzyme digestion. The recombinant vectors were transfected into HUVEC cells and HL7702 cells by the lipofectin method. GFP expression was observed with a fluorescence microscope to validate the specificity of expression in endothelial cells under the regulation of HRE.ppET-1 element. Cobalt chloride (final concentration 100 mumol/L) was added to the medium to mimic hypoxia in vitro. After transfection of vectors, the expression of VEGF mRNA was detected by RT-PCR, and the expression of VEGF was detected by Western blotting and ELISA methods under normoxia and hypoxia, respectively. The cell proliferation rate was detected by the MTT test. The expression of GFP revealed that the exterior gene was transcripted effectively in endothelial cells regulated by the HRE.ppET-1 element, while the expression of GFP was very weak in nonendothelial cells. The results of RT-PCR, Western blotting and ELISA showed that VEGF gene expression in the pcDNA3.1-HRE.ppET-1+VEGF+Pa group and in the pcDNA3.1-ppET-1+VEGF+Pa group was higher in hypoxia than it was in normoxia (P<0.05). The MTT test showed that the proliferation rate of HUVEC transfected with HPVA under hypoxia exceeded that of the control group. We conclude that the HRE.ppET-1 element was expressed specifically in endothelial cells, and can increase the expression of VEGF in hypoxia and stimulate proliferation of endothelial cells. Taking advantage of these facts could greatly improve the efficiency of gene therapy. The vector would be valuable for various gene transfer studies targeting endothelial cells.

Antiangiogenic systemic gene therapy combined with doxorubicin administration induced caspase 8 and 9-mediated apoptosis in endothelial cells and an anti-metastasis effect

Ad-PPE-Fas-c is an adenovector that expresses Fas-c under the control of the modified pre-proendothelin-1 (PPE-1) promoter. Fas-c is a chimeric death receptor containing the extracellular portion of tumour necrosis factor 1 receptor (TNFR1) and the transmembrane and intracellular portion of Fas. We recently demonstrated that Ad-PPE-Fas-c induced Fas-receptor-mediated endothelial cell apoptosis. Previously, doxorubicin was shown to enhance Fas-receptor clustering and the induction of its cascade. Therefore, the goal of this work was to test whether doxorubicin augments the capacity of Ad-PPE-Fas-c to induce endothelial cell apoptosis and to elucidate whether either the death-receptor-mediated apoptotic cascade or the mitochondria-associated apoptotic cascade is involved in the combined treatment effect. We found that a combined treatment of Ad-PPE-Fas-c and doxorubicin synergistically induced a reduction in endothelial cell viability and apoptosis. z-IETD-FMK, a caspase-8 inhibitor, and z-LEHD-FMK, a caspase-9 inhibitor, significantly decreased apoptosis induced by the combined treatment. Systemically administered combined therapy significantly reduced the lung metastases burden (70%) in mice as compared to each treatment alone. Thus, a combined treatment of Ad-PPE-Fas-c gene therapy and chemotherapy may be effective in the treatment of metastatic diseases and both the Fas cascade and the mitochondria-associated cascade are essential for this effect.

Vascular Wall Maturation and Prolonged Angiogenic Effect by Endothelial-Specific Platelet-Derived Growth Factor Expression

BACKGROUND

The implementation of angiogenic gene therapy at clinics is hindered by the transience of the therapeutic effect. Recruiting vascular wall smooth muscle cells, a process termed 'maturation', can stabilize newly formed vessels.

OBJECTIVE

To induce angiogenesis followed by vessel maturation in a murine ischemic limb model by endothelial cell-specific promoter regulated expression of vascular endothelial growth factor (VEGF) and platelet-derived growth factor-BB (PDGF-BB).

METHODS

We constructed adenoviral vectors containing angiogenic factors VEGF and PDGF-B regulated by a modified preproendothelin-1 (PPE-1-3x) promoter and investigated their angiogenic effect in a murine ischemic limb model.

RESULTS

VEGF gene therapy increased perfusion and the vessel density in the limb shortly after expression with PPE-1-3x promoter or cytomegalovirus (CMV) promoter vectors, but only PPE-1-3xVEGF treatment exhibited a sustained effect. Expression of PDGF-B by PPE-1-3x promoter resulted in morphological maturation of the vasculature and further increased the perfusion, while nonspecific expression of PDGF-B with CMV promoter had no therapeutic effect. Regulation of dual therapy with VEGF and PDGF-B by PPE-1-3x promoter resulted in an early-onset, sustained angiogenic effect accompanied by vessel maturation.

CONCLUSIONS

Systemic gene therapy with the angiogenic factors VEGF and PDGF-B under angiogenic- endothelial cell-specific regulation was effective in inducing functionally and morphologically mature vasculature.

Plasmid engineering for controlled and sustained gene expression for nonviral gene therapy

Gene therapy requires the introduction of genetic material in diseased cells with the aim of treating or ultimately curing a disease. Since the start of gene therapy clinical trials in 1990, gene therapy has proven to be possible, but studies to date have highlighted the difficulty of achieving efficient, specific, and long-term transgene expression. Efforts to improve gene therapy strategies over the past years were mainly aimed at solving the problem of delivery, without paying much attention to the optimization of the expression cassette. With the current understanding of the eukaryotic transcription machinery and advanced molecular biology techniques at our disposition, it has now become possible to create custom-made transgene expression cassettes optimized for gene therapy applications. In this review, we will discuss several strategies that have been explored to improve the level and duration of transgene expression, to increase control over expression, or to restrict transgene expression to specific cell types or tissues. Although still in its infancy, such strategies will eventually lead to improvement of nonviral gene therapy and expansion of the range of possible therapeutic applications.

Sustained expression after nonviral ocular gene transfer using mammalian promoters

The CMV promoter drives high transgene expression and is one of the most commonly used promoters for gene transfer. Tissue-specific mammalian promoters provide an alternative, and it would be useful to have a system to directly compare them to viral promoters free from potential confounding vector-related effects. In this study, we describe how electroporation after subretinal injection of plasmid DNA can be used to perform comparative quantitative analysis of promoter activities. Luciferase assay of eyecup homogenates was carried out after coinjection/electroporation of pGL2, a plasmid containing the promoter fragment of interest coupled to the firefly luciferase gene, and pRL-CMV, a plasmid containing the CMV promoter coupled to the Renilla luciferase gene for normalization. This technique was used to compare activity of different fragments of the 5'-upstream region of the vitelliform macular dystrophy 2 (VMD2) gene, which is selectively expressed in the retinal pigmented epithelial (RPE) cells, and results indicated positive regulatory elements between -104 and -154 bp and between -424 and -585 bp. Addition of a fragment from intron 1 reduced the activity of the -585/+38 bp fragment by 75%. Deletion analysis implicated a 342 bp region near the 5'-end of intron 1 in the repression. Results of transient transfections in two cell lines that constitutively express VMD2 were similar, and results in transgenic mice were consistent, providing validation for promoter analysis by in vivo electroporation. We then explored the time course of expression of the -585/+38 VMD2 promoter fragment and found that compared to cassettes driven by CMV or SV40 promoters, which showed peak luciferase activity on day 2 followed by a rapid decrease in activity, the VMD2 promoter fragment showed lower activity initially, but the activity was sustained for up to 56 days (longest time point measured). A promoter fragment from another RPE-specific gene, Rpe65, showed a similar pattern of sustained expression for at least 112 days. These data indicate that nonviral gene transfer can be used to quantitatively evaluate the activity of promoter fragments independent of influence from viral vectors. A potentially important finding using this new technique is the demonstration that relatively sustained passenger gene expression can be achieved with nonviral gene transfer using mammalian rather than viral promoters.

Tumor vascular targeting therapy with viral vectors

Tumor angiogenesis is crucial for the progression and metastasis of cancer. The vasculature of tumor tissue is different from normal vasculature. Therefore, tumor vascular targeting therapy could represent an effective therapeutic strategy with which to suppress both primary tumor growth and tumor metastasis. The use of viral vectors for tumor vascular targeting therapy is a promising strategy based on the unique properties of viral vectors. In order to circumvent the potential problems of antiviral neutralizing antibodies, poor access to extravascular tumor tissue, and toxicities to normal tissue, viral vectors need to be modified to target the tumor endothelial cells. Viral vectors that could be used for tumor vascular targeting therapy include adenoviral vectors, adeno-associated viral vectors, retroviral vectors, lentiviral vectors, measles virus, and herpes simplex viral vectors. In this review, we will summarize the strategies available for targeting viral vectors for tumor vascular targeting therapy.

In vivo efficacy of HSV-TK transcriptionally targeted to the tumour vasculature is augmented by combination with cytotoxic chemotherapy

BACKGROUND

Retroviral vectors are suitable for targeting endothelial cells in the tumour neovasculature because of their intrinsic selectivity for proliferating cells. Previously, we inserted regulatory elements of the endothelial-specific prepro-endothelin-1 (ppET1) promoter in retroviral vectors to generate high-titre, replication-defective recombinant retroviruses that restricted gene expression to the vascular compartment of tumours.

METHODS

A retroviral vector was generated in which expression of herpes simplex virus thymidine kinase (HSV-TK) was transcriptionally restricted to endothelial cells, under the control of a hybrid ppET-1 LTR. Xenograft tumour models were used to determine the efficacy of targeting HSV-TK to the tumour vasculature. Subsequently, vascular-targeted gene therapy was combined with chemotherapeutic agents.

RESULTS

Breast or colorectal xenograft tumour growth was reduced and survival was increased in response to ganciclovir treatment. Treatment resulted in widespread vascular disruption and tumour cell apoptosis. In colorectal tumours, combination with irinotecan, a cytotoxic drug used to treat colorectal cancer, significantly increased survival compared to drug alone. No beneficial effect on survival was observed when combined with cisplatin, a cytotoxic drug not in clinical use for this tumour type. On the basis of their relative efficacies in vitro against tumour and endothelial cells, co-operativity with irinotecan likely derives from additionally targeting the peripheral tumour cells that survive the anti-vascular treatment.

CONCLUSIONS

We show that the ppET1-targeted vector is efficacious for therapeutic gene expression in vivo, validating a strategy targeted to tumour vasculature, and demonstrate that vascular targeting combined with appropriate chemotherapy is more effective than either therapy alone.

Inhibition of carcinogenesis in transgenic mouse models over-expressing 15-lipoxygenase in the vascular wall under the control of murine preproendothelin-1 promoter

Oxygenases are a family of enzymes that dioxygenate unsaturated fatty acids, thus initiating membrane oxidation and signaling molecule synthesis. The lipoxygenases (LOs), a family of lipid-peroxidizing enzymes that induce structural and metabolic changes in the cell in a number of pathophysiological conditions, belong to the oxygenases family. This class of enzymes has several subgroups, named 5-, 8-, 12- and 15-LOs, and these LO-isoforms are capable of oxygenating arachidonic and linoleic acid. 15-LOs were reported to play an inhibitory role in tumor angiogenesis and, consequently, they slow down carcinogenesis. It has been suggested that its anti-carcinogenic effect is conferred by promoting cell differentiation and apoptosis. Using transgenic mice that over-express 15-LO-1 in endothelial cells under the regulation of the murine preproendothelin-1 promoter, we studied its effect on tumor and metastasis growth. We found that 15-LO-1 inhibited tumor and metastasis growth in the transgenic mice in two different models of cancer (mammary gland and Lewis lung carcinoma). This inhibition was concomitant with a higher number of apoptotic cells in the metastases of the transgenic mice and with a complicated network of multiple small blood vessels. This finding targets 15-LO as a new candidate in the treatment of carcinogenesis.

The multiple uses of fluorescent proteins to visualize cancer in vivo

Naturally fluorescent proteins have revolutionized biology by enabling what was formerly invisible to be seen clearly. These proteins have allowed us to visualize, in real time, important aspects of cancer in living animals, including tumour cell mobility, invasion, metastasis and angiogenesis. These multicoloured proteins have allowed the colour-coding of cancer cells growing in vivo and enabled the distinction of host from tumour with single-cell resolution. Visualization of many aspects of cancer initiation and progression in vivo should be possible with fluorescent proteins.

Endothelin Axis Is a Target of the Lung Metastasis Suppressor Gene RhoGDI2

Half of patients treated for locally advanced bladder cancer relapse with often fatal metastatic disease to the lung. We have recently shown that reduced expression of the GDP dissociation inhibitor, RhoGDI2, is associated with decreased survival of patients with advanced bladder cancer. However, the effectors by which RhoGDI2 affects metastasis are unknown. Here we use DNA microarrays to identify genes suppressed by RhoGDI2 reconstitution in lung metastatic bladder cancer cell lines. We identify such RNAs and focus only on those that also increase with tumor stage in human bladder cancer samples to discover only clinically relevant targets of RhoGDI2. Levels of endothelin-1 (ET-1), a potent vasoconstrictor, were affected by both RhoGDI2 reconstitution and tumor stage. To test the hypothesis that the endothelin axis is important in lung metastasis, lung metastatic bladder carcinoma cells were injected in mice treated with the endothelin receptor-specific antagonist, atrasentan, thereby blocking engagement of the up-regulated ET-1 ligand with its cognate receptor. Endothelin antagonism resulted in a dramatic reduction of lung metastases, similar to the effect of reexpressing RhoGDI2 in these metastatic cells. Taken together, these experiments show a novel approach of identifying therapeutic targets downstream of metastasis suppressor genes. The data also suggest that blockade of the ET-1 axis may prevent lung metastasis, a new therapeutic concept that warrants clinical evaluation.

Vascular-targeted cancer gene therapy

As a consequence of the dramatic progress that has been made in recent years towards elucidating the diverse molecular events involved in the development and pathogenesis of malignant disease, there is now no shortage of genes that can be exploited or targeted in the context of cancer gene therapy. Many of these have been shown to be effective both in vitro and in various animal models, and a number have progressed to the clinic. The results of these later studies, although generally encouraging, are perhaps less dramatic than one might have hoped. Although a number of factors undoubtedly contribute to this finding, it is evident that a major reason relates to the difficulties implicit in achieving efficient in vivo gene transfer, particularly in a clinical context. Targeting gene therapy, not to the malignant population, but instead to the vasculature upon which the survival and growth of a tumour depends constitutes an alternative approach that overcomes some of the delivery problems associated with established tumour cell-directed strategies.

In vivo cell biology of cancer cells visualized with fluorescent proteins

This chapter describes a new cell biology where the behavior of individual cells can be visualized in the living animal. Previously it has been demonstrated that fluorescent proteins can be used for whole-body imaging of metastatic tumor growth, bacterial infection, and gene expression. An example of the new cell biology is dual-color fluorescence imaging using red fluorescent protein (RFP)-expressing tumors transplanted in green fluorescent protein (GFP)-expressing transgenic mice. These models show with great clarity the details of tumor-stroma interactions and especially tumor-induced angiogenesis, tumor-infiltrating lymphocytes, stromal fibroblasts, and macrophages. Another example is the color coding of cells with RFP or GFP such that both cell types can be simultaneously visualized in vivo. Stem cells can also be visualized and tracked in vivo. Mice in which the regulatory elements of the stem cell marker nestin drive GFP expression enable nascent vasculature to be visualized interacting with transplanted RFP-expressing cancer cells. Nestin-driven GFP expression can also be used to visualize hair follicle stem cells. Dual-color cells expressing GFP in the nucleus and RFP in the cytoplasm enable real-time visualization of nuclear-cytoplasm dynamics including cell cycle events and apoptosis. Highly elongated cancer cells in capillaries in living mice were observed within skin flaps. The migration velocities of the cancer cells in the capillaries were measured by capturing images of the dual-color fluorescent cells over time. The cells in the capillaries elongated to fit the width of these vessels. The use of the dual-color cancer cells differentially labeled in the cytoplasm and nucleus and associated fluorescent imaging provide a powerful tool to understand the mechanism of cancer cell migration and deformation in small vessels.

Tissue-specific promoters for cancer gene therapy

Adenoviral cancer gene therapy approaches have resulted in promising recent results. Following only a decade of intense development, some of the crucial obstacles are now being overcome. Insufficient transduction has been the main limitation of earlier approaches. A new approach for increasing transduction of tumour cells is utilisation of replication-competent oncolytic agents, such as conditionally replicating adenoviruses (CRADs). The anti-tumour effect is caused by replication of the virus per se and, thus, replication must be restricted to tumour cells to protect normal tissues from damage. Tissue-specific promoters (TSPs) represent a powerful tool for decreasing the toxicity of cancer gene therapy to normal tissues and have previously been utilised for specific mutation compensation or delivery of prodrug-converting enzymes. However, TSPs can also be used for controlling crucial viral replication regulators and consequent restriction of replication to tumour cells. Initial clinical trials have demonstrated the safety and suggested efficacy for TSP-controlled CRADs as a novel approach for cancer gene therapy.

Antiangiogenic gene therapy of cancer: recent developments

With the role of angiogenesis in tumor growth and progression firmly established, considerable effort has been directed to antiangiogenic therapy as a new modality to treat human cancers. Antiangiogenic agents have recently received much widespread attention but strategies for their optimal use are still being developed. Gene therapy represents an attractive alternative to recombinant protein administration for several reasons. This review evaluates the potential advantages of gene transfer for antiangiogenic cancer therapy and describes preclinical gene transfer work with endogenous angiogenesis inhibitors demonstrating the feasibility of effectively suppressing and even eradicating tumors in animal models. Additionally, we describe the advantages and disadvantages of currently available gene transfer vectors and update novel developments in this field. In conclusion, gene therapy holds great promise in advancing antiangiogenesis as an effective cancer therapy and will undoubtedly be evaluated in human clinical trials in the near future.

Transcription-controlled gene therapy against tumor angiogenesis

A major drawback of current approaches to antiangiogenic gene therapy is the lack of tissue-specific targeting. The aim of this work was to trigger endothelial cell-specific apoptosis, using adenoviral vector-mediated delivery of a chimeric death receptor derived from the modified endothelium-specific pre-proendothelin-1 (PPE-1) promoter. In the present study, we constructed an adenovirus-based vector that targets tumor angiogenesis. Transcriptional control was achieved by use of a modified endothelium-specific promoter. Expression of a chimeric death receptor, composed of Fas and TNF receptor 1, resulted in specific apoptosis of endothelial cells in vitro and sensitization of cells to the proapoptotic effect of TNF-alpha. The antitumoral activity of the vectors was assayed in two mouse models. In the model of B16 melanoma, a single systemic injection of virus to the tail vein caused growth retardation of tumor and reduction of tumor mass with central tumor necrosis. When the Lewis lung carcinoma lung-metastasis model was applied, i.v. injection of vector resulted in reduction of lung-metastasis mass, via an antiangiogenic mechanism. Moreover, by application of the PPE-1-based transcriptional control, a humoral immune response against the transgene was avoided. Collectively, these data provide evidence that transcriptionally controlled, angiogenesis-targeted gene therapy is feasible.

Antiangiogenesis: the fifth cancer treatment modality?

PURPOSE/OBJECTIVES

To describe the biologic process of angiogenesis and the potential role of antiangiogenesis therapy in cancer treatment.

DATA SOURCES

Published articles, conference proceedings, and computerized databases.

DATA SYNTHESIS

Angiogenesis is the development of blood vessels. Antiangiogenic agents prevent the development of blood vessels, therefore preventing one mode of cancer metastasis. Clinical trials must be conducted to ascertain the most powerful antiangiogenic therapies. Trials combine chemotherapy, biotherapy, and radiotherapy with antiangiogenic therapy.

CONCLUSIONS

Information from animal studies has revealed that antiangiogenesis is a viable option in treating cancer and preventing metastasis. Although human studies are rare, preliminary results are promising, especially when antiangiogenesis is used in combination with current cancer treatment modalities.

IMPLICATIONS FOR NURSING

Nurses are in a unique position to teach patients about new treatments for cancer. Nurses must be knowledgeable about angiogenesis and the availability of potential antiangiogenesis agents. Nurses will be vital in collecting data in clinical trials, considering the subjective data that will be obtained.

New organs from our own tissues: liver-to-pancreas transdifferentiation

Recent advances in pancreatic islet transplantation emphasize the potential of this approach for the long-term control of blood glucose levels in diabetic patients. However, tissue-replacement therapy will become widely available as a treatment for diabetes only when new sources of islets and insulin-producing cells are found. Here, we review recent evidence that documents the potential of mature liver as a source of tissue for generating a functional endocrine pancreas, by ectopic expression of pancreatic transcription and differentiation factors. When key events in the transconversion process have been identified, using the liver as a source of pancreatic tissue might provide a valuable approach for replacing impaired beta cell function in diabetics.

Optical imaging: bacteria, viruses, and mammalian cells encoding light-emitting proteins reveal the locations of primary tumors and metastases in animals

Early detection of tumors and their metastases is crucial for the prognosis of cancer treatment. Traditionally, tumor detection is achieved by various methods, including magnetic resonance imaging and computerized tomography. With the recent cloning, cellular expression, and real-time imaging of light-emitting proteins, such as Renilla luciferase (Ruc), bacterial luciferase (Lux), firefly luciferase (Luc), green fluorescent protein (GFP), or Ruc-GFP fusion protein, significant efforts have been focused on using these marker proteins for tumor detection. It has also been demonstrated that certain bacteria, viruses, and mammalian cells (BVMC), when administered systemically, are able to gain entry and replicate selectively in tumors. In addition, many tissue/tumor specific promoters have been cloned which allow transgene expression specifically in tumor tissues. Therefore, when light-emitting protein encoded BVMC are injected systemically into rodents, tumor-specific marker gene expression is achieved and is detected in real time based on light emission. Consequently, the locations of primary tumors and previously unknown metastases in animals are revealed in vivo. In the future it will likely be feasible to use engineered light-emitting BVMC as probes for tumor detection and as gene-delivery vehicles in vivo for cancer therapy.