Adenovirus-mediated transfer of BAX driven by the vascular endothelial growth factor promoter induces apoptosis in lung cancer cells

In vitro cytotoxicity evaluation of a CMC-SA edible packaging film for migration and safety assessment

Edible raw materials have gained attention as sustainable food packaging films, which are often considered a priori safe for human consumption. However, cytotoxicity issues may arise due to the incorporation of additives or modifications of film functionality during the manufacturing process. This study introduces an integrated methodology for the evaluation of potential migration of cytotoxic substances from materials used for the development of conventional and biodegradable food packaging. Carboxymethyl cellulose (CMC) and sodium alginate (SA) were tested as raw materials of an edible (CMC-SA) film, while a low-density-polyethylene (LDPE) film was tested as a conventional material. The CMC-SA film exhibited higher water vapor transmission rate and water vapor permeability, and lower hydrophobicity compared to LDPE (WVTRCMC-SA=1457.87 vs. WVTRLDPE=3.43 g×m-2×day-1, WVPCMC-SA=43.24 vs. WVPLDPE=0.0048 g×m-2×mm×day-1×kPa-1 and CACMC-SA=52.05 vs. CALDPE=94.28°, respectively). An analytical protocol based on EU Regulation 10/2011 was introduced, to evaluate the potential migration of cytotoxic packaging substances into food simulants, using different human cells. Caco2 cells were used to simulate human intestine, whereas Huh7 and Immortalized Human Hepatocytes (IHH) cells simulated human liver. Cell viability assays and gene expression results indicated that substances migrating from the tested packaging materials neither produced cell cytotoxicity, nor induced oxidative stress to Caco2 cells.

circRACGAP1 Promotes Proliferation of Non-Small Cell Lung Cancer Cells through the miR-1296/CDK2 Pathway

Circular RNAs (circRNAs) have played an essential role in cancer development. This study aimed to illustrate the impact and potential mechanism of circRACGAP1 action in NSCLC development. The expression patterns of circRACGAP1, miR-1296, and CDK2 in NSCLC tissues and cell lines were analysed by RT-qPCR. The function of circRACGAP1 in NSCLC cell proliferation and apoptosis was investigated using the CCK-8 assay, flow cytometry, TUNEL staining, and Western blot. The interaction among circRACGAP1, miR-1296, and CDK2 was clarified by dual-luciferase reporter assay while the correlation was confirmed by the Pearson correlation coefficient. The expression of circRACGAP1 and CDK2 was up-regulated in NSCLC tissues, while the expression of miR-1296 was down-regulated. Cell function studies further revealed that circRACGAP1 could promote NSCLC cell proliferation, accelerate the cell cycle process, up-regulate B-cell lymphoma 2 (Bcl2) expression, and down-regulate Bcl2-associated X (Bax) expression. miR-1296 was identified as a downstream target to reverse circRACGAP1-mediated cell proliferation. miR-1296 directly targeted the 3'-UTR of CDK2 to regulate proliferation and apoptosis of NSCLC cells. Additionally, the dual-luciferase reporter assay and Pearson correlation coefficient analysis proved that circRACGAP1 acted in NSCLC cells by negatively regulating miR-1296 expression and positively regulating CDK2 expression. In summary, our study revealed that circRACGAP1 promoted NSCLC cell proliferation by regulating the miR-1296/CDK2 pathway, providing potential diagnostic and therapeutic targets for NSCLC.

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

Downregulation of TMPRSS4 Enhances Triple-Negative Breast Cancer Cell Radiosensitivity Through Cell Cycle and Cell Apoptosis Process Impairment

Background:

Radioresistance remains a challenge for cancer radiotherapy. The present study aims to investigate the role of TMPRSS4 in triple negative breast cancer (TNBC) cell radiosensitivity.

Materials and Methods:

After transfection of MDA-MD-468 triple negative breast cancer cells line by using the lentivirus vector, the effect of TMPRSS4 down-regulation on TNBC radiosensitivity was evaluated by using cloning assay and CCK-8 assay. The CCK-8 assay was also used for performing cell proliferation analysis. Western blot was carried out to detect the expression of certain proteins related to cell cycle pathways (cyclin D1), cell apoptosis pathways (Bax, Bcl2, and Caspase3), DNA damage and DNA damage repair (TRF2, Ku80 , ˠH2AX) . The cell cycle and cell apoptosis were also investigated using flow cytometer analysis.

Results:

TMPRSS4 expression was down-regulated in MDA-MB-468 cells which enhanced MDA-MB-468 cells radiosensitivity. TMPRSS4 silencing also improved IR induced cell proliferation ability reduction and promoted cell arrested at G2/M phase mediated by 6 Gy IR associated with cyclin D1 expression inhibition. Moreover, TMPRSS4 inhibition enhanced TNBC apoptosis induced by 6 Gy IR following by over-expression of (Bax, Caspase3) and down-regulation of Bcl2 as the pro-apoptotic and anti-apoptotic proteins, respectively. Otherwise, TMPRSS4 down-regulation increases DNA damage induced by 6 Gy IR and delays DNA damage repair respectively illustrated by downregulation of TRF2 and permanent increase of Ku80 and ˠH2AX expression at 1 h and 10 h post-IR.

Conclusion:

Down-regulation of TMPRSS4 increases triple negative breast cancer cell radiosensitivity and the use of TMPRSS4 inhibitor can be encouraged for improving radiotherapy effectiveness in TNBC radioresistant patients.

Hypoxia-inducible tumour-specific promoters as a dual-targeting transcriptional regulation system for cancer gene therapy

Transcriptional targeting is the best approach for specific gene therapy. Hypoxia is a common feature of the tumour microenvironment. Therefore, targeting gene expression in hypoxic cells by placing transgene under the control of a hypoxia-responsive promoter can be a good strategy for cancer-specific gene therapy. The hypoxia-inducible gene expression system has been investigated more in suicide gene therapy and it can also be of great help in knocking down cancer gene therapy with siRNAs. However, this system needs to be optimised to have maximum efficacy with minimum side effects in normal tissues. The combination of tissue-/tumour-specific promoters with HRE core sequences has been found to enhance the specificity and efficacy of this system. In this review, hypoxia-inducible gene expression system as well as gene therapy strategies targeting tumour hypoxia will be discussed. This review will also focus on hypoxia-inducible tumour-specific promoters as a dual-targeting transcriptional regulation systems developed for cancer-specific gene therapy.

Survivin a radiogenetic promoter for glioblastoma viral gene therapy independently from CArG motifs

Background

Radiogenetic therapy is a novel approach in the treatment of cancer, which employs genetic modification to alter the sensitivity of tumor cells to the effect of applied radiation.

Aim

To select a potent radiation inducible promoter in the context of brain tumors and to investigate if CArG radio responsive motifs or other elements in the promoter nucleotide sequences can correlate to its response to radiation.

Methods

To select initial candidates for promoter inducible elements, the levels of mRNA expression of six different promoters were assessed using Quantitative RTPCR in D54 MG cells before and after radiation exposure. Recombinant Ad/reporter genes driven by five different promoters; CMV, VEGF, FLT-1, DR5 and survivin were constructed. Glioma cell lines were infected with different multiplicity of infection of the (promoter) Ad or CMV Ad. Cells were then exposed to a range of radiation (0–12 Gy) at single fraction. Fluorescent microscopy, Luc assay and X-gal staining was used to detect the level of expression of related genes. Different glioma cell lines and normal astrocytes were infected with Ad survivin and exposed to radiation. The promoters were analyzed for presence of CArG radio-responsive motifs and CCAAT box consensus using NCBI blast bioinformatics software.

Results

Radiotherapy increases the expression of gene expression by 1.25–2.5 fold in different promoters other than survivin after 2 h of radiation. RNA analysis was done and has shown an increase in copy number of tenfold for survivin. Most importantly cells treated with RT and Ad Luc driven by survivin promoter showed a fivefold increase in expression after 2 Gy of radiation in comparison to non-irradiated cells. Presence or absence of CArG motifs did not correlate with promoter response to radiation. Survivin with the best response to radiation had the lowest number of CCAAT box.

Conclusion

Survivin is a selective potent radiation inducible promoter for glioblastoma viral gene therapy and this response to radiation could be independent of CArG motifs.

Chapter seven--Cancer treatment with gene therapy and radiation therapy

Radiation therapy methods have evolved remarkably in recent years which have resulted in more effective local tumor control with negligible toxicity of surrounding normal tissues. However, local recurrence and distant metastasis often occur following radiation therapy mostly due to the development of radioresistance through the deregulation of the cell cycle, apoptosis, and inhibition of DNA damage repair mechanisms. Over the last decade, extensive progress in radiotherapy and gene therapy combinatorial approaches has been achieved to overcome resistance of tumor cells to radiation. In this review, we summarize the results from experimental cancer therapy studies on the combination of radiation therapy and gene therapy.

Adenovirus-mediated hypoxia-targeted gene therapy using HSV thymidine kinase and bacterial nitroreductase prodrug-activating genes in vitro and in vivo

Hypoxia is an important factor in tumor growth. It is associated with resistance to conventional anticancer treatments. Gene therapy targeting hypoxic tumor cells therefore has the potential to enhance the efficacy of treatment of solid tumors. Transfection of a panel of tumor cell lines with plasmid constructs containing hypoxia-responsive promoter elements from the genes, vascular endothelial growth factor (VEGF) and erythropoietin, linked to the minimal cytomegalovirus (mCMV) or minimal interleukin-2 (mIL-2) promoters showed optimum hypoxia-inducible luciferase reporter gene expression with five repeats of VEGF hypoxic-response element linked to the mCMV promoter. Adenoviral vectors using this hypoxia-inducible promoter to drive therapeutic transgenes produced hypoxia-specific cell kill of HT1080 and HCT116 cells in the presence of prodrug with both herpes simplex virus thymidine kinase/ganciclovir and nitroreductase (NTR)/CB1954 prodrug-activating systems. Significant cytotoxic effects were also observed in patient-derived human ovarian cancer cells. The NTR/CB1954 system provided more readily controllable transgene expression and so was used for in vivo experiments of human HCT116 xenografts in nude mice. Subjects treated intratumorally with Ad-VEGFmCMV-NTR and intraperitoneal injection of CB1954 demonstrated a statistically significant reduction in tumor growth. Immunohistochemistry of treated xenografts showed a good correlation between transgene expression and hypoxic areas. Further investigation of these hypoxia-inducible adenoviral vectors, alone or in combination with existing modalities of cancer therapy, may aid in the future development of successful Gene-Directed Enzyme Prodrug Therapy systems, which are much needed for targeting solid tumors.

The HIF-1-active microenvironment: an environmental target for cancer therapy

Solid tumors possess unique microenvironments that are exposed to chronic hypoxic conditions, so-called tumor hypoxia. Although more than half a century has passed since it was suggested that tumor hypoxia correlated with bad treatment outcomes and contributed to the recurrence of cancer, no fundamental solution to this problem has yet been found. Hypoxia-inducible factor HIF-1 is the main transcription factor that regulates the cellular response to hypoxia. It induces various genes, whose function is strongly associated with the malignant alteration of the entire tumor. The cellular changes induced by HIF-1 are extremely important therapeutic targets of cancer therapy, particularly in the therapy against refractory cancers. Therefore targeting strategies to overcome the HIF-1-active microenvironment are important for cancer therapy.

Apoptotic pathways in tumor progression and therapy

Apoptosis is a cell suicide program that plays a critical role in development and tissue homeostasis. The ability of cancer cells to evade this programmed cell death (PCD) is a major characteristic that enables their uncontrolled growth. The efficiency of chemotherapy in killing such cells depends on the successful induction of apoptosis, since defects in apoptosis signaling are a major cause of drug resistance. Over the past decades, much progress has been made in our understanding of apoptotic signaling pathways and their dysregulation in cancer progression and therapy. These advances have provided new molecular targets for proapoptotic cancer therapies that have recently been used in drug development. While most of those therapies are still at the preclinical stage, some of them have shown much promise in the clinic. Here, we review our current knowledge of apoptosis regulation in cancer progression and therapy, as well as the new molecular targeted molecules that are being developed to reinstate cancer cell death.

Vascular endothelial growth factor promoter-based conditionally replicative adenoviruses for pan-carcinoma application

Treatment of advanced lung cancer is one of the major challenges in current medicine because of the high morbidity and mortality of the disease. Advanced stage lung cancer is refractory to conventional therapies and has an extremely poor prognosis. Thus, new therapeutic approaches are needed. Lung tumor formation depends on angiogenesis in which the vascular endothelial growth factor (VEGF) produced by cancer cells plays a pivotal role. Neutralizing VEGF with a soluble VEGF receptor suppresses tumor growth; however, the anticancer effect with this therapy is weakened after the intratumoral vascular network is completed. In this study, we turned the expression of VEGF by tumors to therapeutic advantage using a conditionally replication-competent adenovirus (CRAd) in which the expression of E1 is controlled by the human VEGF promoter. This virus achieved good levels of viral replication in lung cancer cells and induced a substantial anticancer effect in vitro and in vivo. As a further enhancement, the cancer cell killing effect was improved with tropism modification of the virus to express the knob domain of Ad3, which improved infectivity for cancer cells. These VEGF promoter-based CRAds also showed a significant cell killing effect for various types of cancer lines other than lung cancer. Conversely, the VEGF promoter has low activity in normal tissues, and the CRAd caused no damage to normal bronchial epithelial cells. Since tumor-associated angiogenesis via VEGF signalling is common in many types of cancers, these CRAds may be applicable to a wide range of tumors. We concluded that VEGF promoter-based CRAds have the potential to be an effective strategy for cancer treatment.

Prevention of posterior capsule opacification by the induction of therapeutic apoptosis of residual lens cells

Posterior capsule opacification (PCO) is a common complication of cataract surgery. Using adenovirus(Ad)-mediated gene transfer, we overexpressed the proapoptotic molecules p53, procaspase 3, Bax, and TRAIL to induce therapeutic programmed cell death of residual lens cells to prevent PCO. Overexpressed TRAIL did not induce apoptosis in cultured rabbit lens cells or in human lens cells. Overexpressed p53 induced apoptosis of lens cells in vitro and ex vivo, but was unable to prevent PCO in vivo. Overexpressed procaspase 3 was associated with engagement of many components of the apoptotic pathway, including cleavage of intracellular caspase targets such as PARP and inter-nucleosome DNA fragmentation. Even when only slightly overexpressed, Bax caused apoptosis of transduced rabbit and human lens cells by engaging the mitochondrial pathway, including catalytic activation of the caspases. A single in vivo injection of Ad vectors expressing either Bax or procaspase 3 into the capsular bag at the end of phacoemulsification prevented PCO in rabbits. These experiments show that Ad-mediated Bax or procaspase 3 overexpression is capable of inducing therapeutic programmed cell death in vitro and in vivo in residual lens cells and preventing PCO in a rabbit model of PCO. Manipulation of proapoptotic molecule expression could be a novel gene therapy approach for prevention of PCO.

Development and characterization of a synthetic promoter for selective expression in proliferating endothelial cells

BACKGROUND

Systemic administration of non-viral gene therapy provides better access to tumors than local administration. Development of a promoter that restricts expression of cytotoxic proteins to the tumor vasculature will increase the safety of the system by minimizing expression in the non-dividing endothelial cells of the vasculature of non-target tissues.

METHODS

Cell cycle promoters were tested for selective expression in dividing cells vs. non-dividing cells in vitro and promoter strength was compared to the cytomegalovirus (CMV) promoter. Successful promoter candidates were tested in vivo using two proliferating endothelium mouse models. Ovarectomized mice were injected with estradiol prior to lipoplex administration and expression levels were measured in the lungs and uterus 4 days after administration. The second model was a subcutaneous tumor model and expression levels were measured in the lungs and tumors. For both animal models, expression levels from the proliferating endothelium promoter were compared to that obtained from a CMV promoter.

RESULTS

The results showed that the Cdc6 promoter yielded higher expression in proliferating vs. non-proliferating cells. Secondly, promoter strength could be selectively increased in endothelial cells by the addition of a multimerized endothelin enhancer (ET) to the Cdc6 promoter. Thirdly, comparison of expression levels in the lungs vs. uterus in the ovarectomized mouse model and lungs vs. tumor in the mouse tumor model showed expression was much higher in the uterus and the tumor than in the lungs for the ET/Cdc6 promoter, and expression levels were comparable to that of the CMV promoter in the hypervascularized tissues.

CONCLUSIONS

These results demonstrate that the combination of the endothelin enhancer with the Cdc6 promoter yields selective expression in proliferating endothelium and can be used to express cytotoxic proteins to treat vascularized tumors.

Cancer-specific gene therapy

Cancer cells transcriptionally activate many genes that are important for uncontrolled proliferation and cell death. Deregulated transcriptional machinery in tumor cells usually consists of increased expression/activity of transcription factors. Ideally, cancer-specific killing can be achieved by delivering a therapeutic gene under the control of the DNA elements that can be activated by transcription factors that are overexpressed and/or constitutively activated in cancer cells. Additionally, tumor-specific translation of tumor-killing genes has been also exploited in cancer gene therapy. Based on these rationales, cancer-specific expression of a therapeutic gene has emerged as a potentially successful approach for cancer gene therapy. To achieve tumor-specific expression, cancer-specific vectors are generally composed of promoters, enhancers, and/or 5'-UTR that are responsive to tumor-specific transcription factors. A number of cancer-specific promoters have been reported, such as those of probasin, human telomerase reverse transcriptase, survivin, ceruloplasmin, HER-2, osteocalcin, and carcinoembryonic antigen. Evidences suggest that the enhancer element targeted by beta-catenin can be useful to target colon cancer cells. The 5'-UTR of the basic fibroblast growth factor-2 has been reported to provide tumor specificity. Moreover, a variety of therapeutic genes demonstrated direct antitumor effects such as those encoding proapoptotic proteins p53, E1A, p202, PEA3, BAX, Bik, and prodrug metabolizing enzymes, namely thymidine kinase and cytosine deaminase. As cancerous cells of different origins vary significantly in their genetic, transcriptional/translational, and cellular profiles, the success of a cancer gene therapy will not be promised unless it is carefully designed based on the biology of a specific tumor type. Thus, tremendous research efforts have been focused on the development of non-viral vectors that selectively target various tumors resulting in minimal toxicity in the normal tissues. Significant progresses were also made in the exploitation of various novel apoptotic, cytotoxic genes as therapeutic tools that suppress the growth of different tumors. Together, these recent advances provide rationales for future clinical testing of transcriptionally targeted non-viral vectors in cancer patients.

Effect of hypoxia on Ad5 infection, transgene expression and replication

Oxygen deprivation (hypoxia) is a common feature of various human maladies, including cardiovascular diseases and cancer; however, the effect of hypoxia on Ad-based gene therapies has not been described. In this study, we evaluated how hypoxia (1% pO(2)) affects different aspects of Ad-based therapies, including attachment and uptake, transgene expression, and replication, in a series of cancer cell lines and primary normal cells. We found that hypoxia had no significant effect on the expression or function of the Ad5 attachment (Coxsackievirus and Adenovirus Receptor) and internalization (alpha(v) integrins) proteins, nor on the human cytomegalovirus-driven expression of an exogenous gene carried by a replication-incompetent Ad. Viral replication, however, was compromised by hypoxic conditions. Our studies revealed hypoxia-induced reductions in E1A levels that were mediated at the post-transcriptional level. E1A drives cells into the viral replication optimal S phase of the cell cycle; consequently, the combination of reduced E1A protein and hypoxia-induced G1 arrest of cells may be responsible for the lack of efficient viral replication under hypoxic conditions. Consequently, while traditional replication-incompetent Ad-based vectors appear to be viable delivery systems for hypoxia-associated disease indications, our studies suggest that Oncolytic Ads may need additional factors to efficiently treat hypoxic regions of human tumors.

Optical Imaging of Tumor Hypoxia and Evaluation of Efficacy of a Hypoxia-Targeting Drug in Living Animals

Solid tumors containing more hypoxic regions show a more malignant phenotype by increasing the expression of genes encoding angiogenic and metastatic factors. Hypoxia-inducible factor-1 (HIF-1) is a master transcriptional activator of such genes, and thus, imaging and targeting hypoxic tumor cells where HIF-1 is active are important in cancer therapy. In the present study, HIF-1 activity was monitored via an optical in vivo imaging system by using a luciferase reporter gene under the regulation of an artificial HIF-1-dependent promoter, 5HRE. To monitor tumor hypoxia, we isolated a stable reporter-transfectant, HeLa/5HRE-Luc, which expressed more than 100-fold luciferase in response to hypoxic stress, and observed bioluminescence from its xenografts. Immunohistochemical analysis of the xenografts with a hypoxia marker, pimonidazole, confirmed that the luciferase-expressing cells were hypoxic. Evaluation of the efficacy of a hypoxia-targeting prodrug, TOP3, using this optical imaging system revealed that hypoxic cells were significantly diminished by TOP3 treatment. Immunohistochemical analysis of the TOP3-treated xenografts confirmed that hypoxic cells underwent apoptosis and were removed after TOP3 treatment. These results demonstrate that this model system using the 5HRE-luciferase reporter construct provides qualitative information (hypoxic status) of solid tumors and enables one to conveniently evaluate the efficacy of cancer therapy on hypoxia in malignant solid tumors.

Replacement and Suicide Gene Therapy for Targeted Treatment of Lung Cancer

Lung cancer is the leading cause of cancer-related death in the developed world; consequently, novel therapeutic strategies are in high demand. A major problem with the present treatment modalities is the lack of tumor specificity giving rise to dose-limiting toxicity and side effects. Gene therapy constitutes an experimental approach gaining increased attention as a putative future cancer therapeutic strategy. Using this strategy, cancer cytotoxicity can be obtained by replacing mutated genes with functional analogues or introducing a suicide gene into the malignant cells. Insight into the molecular biology of cancer cells has identified a number of regulatory gene sequences, which can be used to selectively activate the therapeutic gene specifically in cancer cells, thereby reducing nonspecific toxicity. Although further improvements are necessary, recent encouraging results have shown promise for future clinical application of gene therapy. This article presents an update on the experimental and clinical results obtained within the field of lung cancer gene therapy, concentrating on strategies to specifically activate expression of the therapeutic gene in cancer cells. Furthermore, status of the development of delivery vector constructs for lung cancer gene therapy will be presented.

Combined ionizing radiation and sKDR gene delivery for treatment of prostate carcinomas

Overexpression of vascular endothelial growth factor (VEGF) and its cognate receptor KDR has been linked to a more aggressive phenotype of human prostate carcinomas. The importance of signal transduction through the VEGF receptor 2 is illustrated by use of soluble KDR, which binds to VEGF and sequesters this ligand before its binding to cellular receptor. Treatment with recombinant adenovirus AdVEGF-sKDR, encoding sKDR under control of the human VEGF promoter, significantly inhibited the proliferation of human vascular endothelial cells and prostate cancer cells. AdVEGF-sKDR infection decreased migration of endothelial 1P-1B cells (61% reduction) and DU145 prostate carcinoma cells (47%) in comparison with AdCMV-Luc-infected control cells. Ionizing radiation upregulated VEGF promoter activity in prostate carcinoma and endothelial cells. AdVEGF-sKDR infection significantly reduced human vascular endothelial and prostate cancer cell proliferation and sensitized cancer cells to ionizing radiation. In vivo tumor therapy studies demonstrated significant inhibition of DU145 tumor growth in mice that received combined AdVEGF-sKDR infection and ionizing radiation versus AdVEGF-sKDR alone or radiation therapy alone. These results suggest that selective transcriptional targeting of sKDR gene expression employing a radiation inducible promoter can effectively inhibit tumor growth and demonstrate the advantage of combination radiotherapy and gene therapy for the treatment of prostate cancer.

Adenovirus-mediated FLT1-targeted proapoptotic gene therapy of human prostate cancer

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is of particular interest in the development of prostate carcinoma therapeutics as it preferentially induces apoptosis of tumor cells. To employ adenoviral vectors for highly efficient and specific TRAIL gene transfer into cancer cells could overcome some potential problems for recombinant TRAIL. The vascular endothelial growth factor receptor FLT-1 is involved in regulation of angiogenesis and tumor growth, invasion, and metastasis of prostate carcinoma. FLT-1 expression is observed in both tumor endothelial cells and prostate cancer cells. We developed an adenoviral vector encoding the TRAIL gene under control of the FLT1 promoter (AdFlt-TRAIL), which produced endothelial and prostate cancer cell death. The combination of ionizing radiation and adenovirus-driven TRAIL expression overcame human prostate cancer cell resistance to TRAIL. Furthermore, in vivo administration of AdFlt-TRAIL at the site of tumor growth in combination with radiation treatment produced significant suppression of the growth of DU145 human prostate tumor xenografts in athymic nude mice. Our results suggest that specific TRAIL delivery employing the FLT1 promoter can effectively inhibit tumor growth and demonstrate the advantage of combination radiotherapy and gene therapy for the treatment of prostate cancer.

Enhanced apoptosis following treatment with TRA-8 anti-human DR5 monoclonal antibody and overexpression of exogenous Bax in human glioma cells

Specific activation of apoptosis in tumor cells offers a promising approach for cancer therapy. Induction of apoptosis leads to activation of specific proteases. Two major pathways for caspase activation in mammalian cells have been described. One apoptotic pathway involves members of the tumor necrosis factor family of cytokine receptors (eg death receptor 5 (DR5)). The other pathway is controlled by the Bcl-2 family of proteins. The purpose of this study was to investigate whether increased apoptosis occurs in human glioma cells following infection with a recombinant adenoviral vector encoding the human Bax gene under the control of human vascular endothelial growth factor (VEGF) promoter element (AdVEGFBax) in combination with an anti-human DR5 monoclonal antibody (TRA-8). Specific overexpression of exogenous Bax protein induced apoptosis and cell death in glioma cell lines, through activation of both caspase-8 and -9, leading to activation of downstream caspase-3. The relative sensitivity to AdVEGFBax for the glioma cell lines was U251MG>U373MG>U87MG>D54MG. The recently characterized TRA-8 monoclonal antibody induces apoptosis of most TRAIL-sensitive tumor cells by specific binding to DR5 receptors on the cellular membrane. TRA-8 induced rapid apoptosis and cell death in glioma cells, but did not demonstrate detectable cytotoxicity of primary normal human astrocytes. The efficiency of TRA-8-induced apoptosis was variable in different glioma cell lines. The relative sensitivity to TRA-8 was U373MG>U87MG>U251MG>D54MG. The combination of TRA-8 treatment and overexpression of Bax overcame TRA-8 resistance of glioma cells in vitro. Cell viability of U251MG cells was 71.1% for TRA-8 (100 ng/ml) alone, 75.9% for AdVEGFBax (5 MOI) alone and 41.1% for their combination as measured by MTS assay. Similar enhanced apoptosis results were obtained for the other glioma cell lines. In vivo studies demonstrated that the combined treatment significantly (P<0.05) suppressed the growth of U251MG xenografts and produced 60% complete tumor regressions without recurrence. These data suggest that the combination of TRA-8 treatment with specific overexpression of Bax using AdVEGFBax may be an effective approach for the treatment of human malignant gliomas.

The role of bcl-2 family members in non-small cell lung cancer

The treatment of advanced nonsmall cell lung cancer (NSCLC) continues to pose great challenges for the thoracic surgeon. Current therapeutic strategies with chemotherapy and radiation are often ineffective adjuncts to surgery. Accordingly, preclinical research concentration has turned to molecular targets that may prove to be more effective. The Bcl-2 family consists of a homologous network of genes that regulate apoptosis or programmed cell death. Altered expression of members in this family leads to aberrant cell proliferation and malignant growth. This review will discuss the expression and significance of Bcl-2 family members in NSCLC and consider potential methods of intervention that are currently being tested and may have clinical applicability. In addition, the current experience with clinical trials involving Bcl-2 down-regulation in solid organ tumors will be summarized.

An adenovirus encoding proapoptotic Bax synergistically radiosensitizes malignant glioma

PURPOSE

We explore the utility of the adenovirus-mediated delivery of proapoptotic Bax for enhancing the cytotoxicity of radiotherapy (RT) in RT-refractory glioma cells.

MATERIALS AND METHODS

Cell lines D54 MG and U87 MG (p53 wild-type), and U251 MG and U373 MG (p53 mutant), and patient-derived astrocytes were evaluated. Cells were irradiated and infected with an inducible adenovirus encoding Bax. Cell proliferation, colony formation assay, quantification of early apoptotic alteration in the plasma membrane by fluorescence-activated cell sorter using annexin V, and nuclear staining with H33258 were used to evaluate apoptosis. The capacity of the combined treatment to induce regression of subcutaneous D54 MG tumors was tested in nude mice. A dose of 5 Gy was administered every other day, four times, for a total dose of 20 Gy. One day after each irradiation, tumors were injected with 1 x 10(9) plaque-forming units (PFU).

RESULTS

Apoptotic death was enhanced by the combination of Ad/Bax and RT. In D54 MG, levels of apoptosis after RT alone, Ad/Bax alone, or the combination were, respectively, 12.3%, 32.1%, and 78.5%. In contrast, treatment of astrocytes did not significantly induce apoptosis. A colony-formation assay showed a 2-log inhibition with respect to controls after combined treatment, irrespective of the endogenous levels of p53. The other apoptosis assays also showed the defining characteristics of apoptosis in the combination group. Remarkably, combined treatment induced regression of tumors in mice.

CONCLUSIONS

Ad/Bax synergistically radiosensitizes glioma, with a seemingly favorable therapeutic index.