Intracavitary liposome-mediated p53 gene transfer into glioblastoma with endogenous wild-type p53 in vivo results in tumor suppression and long-term survival

A review of predictive, prognostic and diagnostic biomarkers for brain tumours: towards personalised and targeted cancer therapy

Background:

Brain tumours are relatively rare disease but present a large medical challenge as there is currently no method for early detection of the tumour and are typically not diagnosed until patients have progressed to symptomatic stage which significantly decreases chances of survival and also minimises treatment efficacy. However, if brain cancers can be diagnosed at early stages and also if clinicians have the potential to prospectively identify patients likely to respond to specific treatments, then there is a very high potential to increase patients’ treatment efficacy and survival. In recent years, there have been several investigations to identify biomarkers for brain cancer risk assessment, early detection and diagnosis, the likelihood of identifying which group of patients will benefit from a particular treatment and monitoring patient response to treatment.

Materials and methods:

This paper reports on a review of 21 current clinical and emerging biomarkers used in risk assessment, screening for early detection and diagnosis, and monitoring the response of treatment of brain cancers.

Conclusion:

Understanding biomarkers, molecular mechanisms and signalling pathways can potentially lead to personalised and targeted treatment via therapeutic targeting of specific genetic aberrant pathways which play key roles in malignant brain tumour formation. The future holds promising for the use of biomarker analysis as a major factor for personalised and targeted brain cancer treatment, since biomarkers have the potential to measure early disease detection and diagnosis, the risk of disease development and progression, improved patient stratification for various treatment paradigms, provide accurate information of patient response to a specific treatment and inform clinicians about the likely outcome of a brain cancer diagnosis independent of the treatment received.

The temporal–spatial expression of VEGF, angiopoietins-1 and 2, and Tie-2 during tumor angiogenesis and their functional correlation with tumor neovascular architecture

Angiopoietins play a pivotal role in tumor angiogenesis by modulating vascular endothelial proliferation and survival. The expression of angiopoietins 1 and 2 (Ang-1 and Ang-2) and vascular endothelial growth factor (VEGF) has been documented in human malignant glioma. The expression of Ang-1, Ang-2, VEGF, and Tie-2, a member of the receptor tyrosine kinases and the natural receptor for both Ang-1 and Ang-2, follows a distinct transcriptional profile in vivo. Ang-2 and VEGF were expressed early in tumor formation and their levels increased throughout tumor growth. Their expression coincided with the expansion of the tumor mass and the formation of the vascular tree. There was no significant change in the expression of Tie-2 and Ang-1. The expression of Ang-1 and Tie-2 was more noticeable at the periphery of the tumor. The expression of Ang-2 was more robust at the periphery and within the tumor mass, and VEGF was more concentrated within the center of the tumor. This distinct expression profile may explain the morphology of the newly formed vessels at various times and regions of the tumor. The lack of concomitant expression of Ang-1 may underscore the unopposed endovascular induction by Ang-2 and VEGF resulting in the chaotic appearance and fragility of tumor vessels.

Sitimagene ceradenovec: a gene-based drug for the treatment of operable high-grade glioma

The field of gene therapy for malignant glioma has made important advances since the first gene transfer studies were performed 20 years ago. Multiple Phase I/II trials and two Phase III trials have been performed and have demonstrated the feasibility and safety of intratumoral vector delivery in the brain. Sitimagene ceradenovec is an adenoviral vector encoding the herpes simplex thymidine kinase gene, developed by Ark Therapeutics Group plc (UK and Finland) for the treatment of patients with operable high-grade glioma. In preclinical and Phase I/II clinical studies, sitimagene ceradenovec exhibited a significant increase in survival. Although the preliminary results of a Phase III clinical study demonstrated a significant positive effect of sitimagene ceradenovec treatment on time to reintervention or death when compared with standard care treatment (hazard ratio: 1.43; 95% CI: 1.06-1.93; p < 0.05), the European Committee for Medicinal Products for Human Use did not consider the data to provide sufficient evidence of clinical benefit. Further clinical evaluation, powered to demonstrate a benefit on a robust end point, is required. This article focuses on sitimagene ceradenovec and provides an overview of the developments in the field of gene therapy for malignant glioma.

Electrogene therapy with p53 of murine sarcomas alone or combined with electrochemotherapy using cisplatin

The aim of our study was to evaluate feasibility and therapeutic potential of electrogene therapy with p53 alone or combined with electrochemotherapy using cisplatin on two murine sarcomas with different p53 status. Antitumor effectiveness of three consecutive electrogene treatments with p53 was more effective in wild-type LPB tumors than mutated SA-1 tumors, resulting in 21.4% of tumor cures in LPB tumors and 12.5% in SA-1 tumors. Pretreatment of tumors with electrogene therapy with p53 enhanced chemosensitivity of both tumor models treated by electrochemotherapy with cisplatin. After only one application of this treatment combination in the LPB tumor model, specific tumor growth delay was prolonged in the combined treatment group compared to electrogene therapy with p53 or electrochemotherapy with cisplatin alone, whereas in SA-1 tumors this treatment combination resulted in 31.6% of cured animals. Results of our study show that electrogene therapy with p53 alone or combined with electrochemotherapy is feasible and effective treatment of tumors. The combination of electrogene therapy and electrochemotherapy after only one application resulted in complete regression of tumors.

Regulatable gene expression systems for gene therapy

It is feasible to restrict transgene expression to a tissue or region in need of therapy by using promoters that respond to focusable physical stimuli. The most extensively investigated promoters of this type are radiation-inducible promoters and heat shock protein gene promoters that can be activated by directed, transient heat. Temporal regulation of transgenes can be achieved by various two- or three-component gene switches that are triggered by an appropriate small molecule inducer. The most commonly considered gene switches that are reviewed herein are based on small molecule-responsive transactivators derived from bacterial tetracycline repressor, insect or mammalian steroid receptors, or mammalian FKBP12/FRAP. A new generation of gene switches combines a heat shock protein gene promoter and a small molecule-responsive gene switch and can provide for both spatial and temporal regulation of transgene activity.

p53 and brain tumors: from gene mutations to gene therapy

The p53 tumor suppressor gene (TP53) is the most frequently altered gene in human cancer and is also found mutated in several types of brain tumors. Loss of p53 function plays a central role in the development of cancer. The characterization of the biochemical pathways by which p53 alteration triggers tumorigenesis is the foundation for the design of novel therapeutic approaches. Investigations of the intracellular mechanisms at the origin of p53 tumor suppressive functions have shown that p53 is a transcription factor able to sense a variety of cellular insults and induce a dual response: cell growth arrest/senescence or apoptosis. Less well studied are p53's influences on extracellular events such as tumor angiogenesis, immunology and invasion. Here, we review these findings and specifically discuss their implications for brain tumor genesis, molecular diagnosis and prognosis. Of clinical importance are the findings that brain tumors with wild type (wt) or mutant p53 status may respond differently to radiation therapy and that novel therapeutic strategies using TP53 gene transfer or specifically targeting tumor cells with mutated p53 are being evaluated in clinical trials.

Regulatable gene expression systems for gene therapy applications: progress and future challenges

Gene therapy aims to revert diseased phenotypes by the use of both viral and nonviral gene delivery systems. Substantial progress has been made in making gene transfer vehicles more efficient, less toxic, and nonimmunogenic and in allowing long-term transgene expression. One of the key issues in successfully implementing gene therapies in the clinical setting is to be able to regulate gene expression very tightly and consistently as and when it is needed. The regulation ought to be achievable using a compound that should be nontoxic, be able to penetrate into the desired target tissue or organ, and have a half-life of a few hours (as opposed to minutes or days) so that when withdrawn or added (depending on the regulatable system used) gene expression can be turned "on" or "off" quickly and effectively. Also, the genetic switches employed should ideally be nonimmunogenic in the host. The ability to switch transgenes on and off would be of paramount importance not only when the therapy is no longer needed, but also in the case of the development of adverse side effects to the therapy. Many regulatable systems are currently under development and some, i.e., the tetracycline-dependent transcriptional switch, have been used successfully for in vivo preclinical applications. Despite this, there are no examples of switches that have been employed in a human clinical trial. In this review, we aim to highlight the main regulatable systems currently under development, the gene transfer systems employed for their expression, and also the preclinical models in which they have been used successfully. We also discuss the substantial challenges that still remain before these regulatable switches can be employed in the clinical setting.

Paclitaxel/Taxol® sensitivity in human renal cell carcinoma is not determined by the p53 status

In this study, we analyzed the role of the p53 status for paclitaxel/Taxol sensitivity in renal cell carcinomas (RCCs) of the clear cell type. Using immunohistochemistry, nuclear p53 accumulation could not be correlated to the paclitaxel/Taxol sensitivity. DNA sequencing detected a p53 gene mutation in two out of eight RCC cell lines, i.e. in exon 8 (cell line clearCa-6), and in exon 9 (cell line clearCa-5). No correlation, however, was found between the p53 status of our RCC cell lines and their paclitaxel/Taxol sensitivity as indicated by the IC50 values. However, paclitaxel-induced growth inhibition in paclitaxel-sensitive RCC cell lines was accompanied by an increase in apoptosis, irrespective of their p53 status. Although CD95 up-regulation was observed in renal cell carcinoma with wild-type p53 upon paclitaxel treatment, paclitaxel-induced apoptosis itself is triggered independently from the CD95 system. In conclusion, the p53 status cannot predict paclitaxel/Taxol sensitivity in RCC cell lines of the clear cell type.

Current strategies in cancer gene therapy

Cancer gene therapy is the most studied application of gene therapy. Many genetic alterations are involved in the transformation of a normal cell into a neoplastic one. The two main gene groups involved in cancer development are oncogenes and tumor suppressor genes. While the latter eliminates cancerous cells via apoptosis, the former enhances cell proliferation. Therefore, apoptotic genes and anti-oncogenes are widely used in cancer gene therapy. In addition to oncogenes and tumor suppressor genes, chemotherapy and gene therapy can be combined through suicide gene strategy. A suicide gene encodes for a non-mammalian enzyme; this enzyme is used to convert a non-toxic prodrug into its active cytotoxic metabolite within the cancerous cells. Tumor suppressor genes, anti-oncogenes and suicide genes target cancer cells on the molecular level. On the other hand, cancer is immunogenic in nature; therefore, it can also be targeted on the immunological level. Boosting the immune response against cancerous cells is usually achieved via genes encoding for cytokines. Interleukin-12 gene, for example, is one of the most studied cytokine genes for cancer gene therapy applications. DNA vaccines are also used after conventional treatments to eliminate remnant malignant cells. All these therapeutic strategies and other strategies namely anti-angiogenesis and drug resistant genes are briefly reviewed and highlighted in this article.

Sensitizing glioma cells to cisplatin by abrogating the p53 response with antisense oligonucleotides

Most gene therapy strategies related to p53 concentrate on the restoration of the activity of mutant p53, as several observations indicate that tumors and cell lines having the mutant gene are resistant to chemotherapy. However, as there is also some evidence to the contrary, we studied the relationship of the p53 status to the cellular response of glioma cells that were exposed to cisplatin. At a concentration of 2.5 microg/ml (which is about half the peak pharmacological blood level reached during chemotherapy), U373MG glioma cells, which had a mutant p53 gene, were more sensitive to the drug as compared to U87MG glioma cells (with normal p53). The U373MG cells responded with apoptosis while U87MG cells responded with a G2-M arrest. In U87MG cells, blocking the p53 response by antisense oligonucleotides also sensitized the cells to 2.5 microg/ml cisplatin, and shifted the cellular response from arrest to caspase 3-mediated apoptosis. A sensitive, p53-independent, mechanism for chemotherapy-induced apoptosis suggests that, in some cases, p53 abrogation by gene therapy or small molecule-based strategies could be a viable therapeutic strategy.

Locoregional immunotherapy of malignant effusion from colorectal cancer using the streptococcal preparation OK-432 plus interleukin-2: induction of autologous tumor-reactive CD4+ Th1 killer lymphocytes

In total, 16 patients with cytologically proven malignant effusion from colorectal cancer were treated by locoregional administration of the streptococcal preparation OK-432 alone or OK-432 plus the T-cell growth factor interleukin (IL)-2, and the action mechanism of the treatment was studied. A positive clinical response, showing a cytologic disappearance of cancer cells and decrease of effusion, was observed in nine of 11 (82%) patients treated with OK-432 alone and in all five patients treated with OK-432 plus IL-2. Flow cytometric analysis revealed that OK-432 plus IL-2 locally induced acute inflammation-like responses, including serial cellular infiltrations of granulocyte migration within a matter of hours, and activation of macrophages and T lymphocyte involvement within the following days, and that a predominant expansion of CD3+CD4+ lymphocytes (CD: cluster of differentiation) was induced by in vitro stimulation with IL-2 of locoregional cells after the OK-432 administration (OK/IL-2AK cells). The OK/IL-2AK cells produced tumour necrosis factor-α and interferon-γ, but these cells did not produce IL-4 and IL-6. The OK/IL-2AK cells expressed potent killing activity against autologous tumour cells. This activity was abrogated by treatment of the lymphocytes with anti-CD3, -CD4, -TCRαβ antibody, and by the treatment of target cells with anti-human leukocyte antigen (HLA)-DR antibody. The OK/IL-2AK cells expressed Fas-L gene, and flow cytometric analysis demonstrated HLA-DR expression in approximately 75% of CEA+ or cytokeratin+ effusion cells. TCRVβ gene analysis of the OK/IL-2AK cells showed an oligoclonal usage of TCRβ20, which was also involved in the cytotoxic mechanism of the OK/IL-2AK cells. Single-strand conformational polymorphism analysis demonstrated the clonotypes for the TCRVβ20 gene, and the CDR3s of the gene were sequenced. The clonotypic PCR using the TCRVβ20-CDR3 sequences could detect the CDR3-identical TCRs in effusion lymphocytes from the other patients. Taken together, it is suggested that locoregional administration of OK-432 plus IL-2 is highly effective for the management of malignant effusion from colorectal cancer. OK-432 plus IL-2 induces autologous tumour-reactive CD4+ Th1 killer lymphocytes, which recognise tumour antigen(s) presented with HLA class II molecules on effusion tumour cells by means of preferential usage of TCRVβ20. The clonotypic PCR using the TCRVβ20-CDR3 sequences may be informative for treating malignant effusion from colorectal cancer using OK-432 plus IL-2.

Sp1 and Sp3 are oxidative stress-inducible, antideath transcription factors in cortical neurons

Neuronal cell death in response to oxidative stress may reflect the failure of endogenous adaptive mechanisms. However, the transcriptional activators induced by oxidative stress in neurons that trigger adaptive genetic responses have yet to be fully elucidated. We report that basal DNA binding of the zinc finger transcription factors Sp1 and Sp3 is unexpectedly low in cortical neurons in vitro and is significantly induced by glutathione depletion-induced or hydrogen peroxide-induced oxidative stress in these cells. The increases in Sp1/Sp3 DNA binding reflect, in part, increased levels of Sp1 and Sp3 protein in the nuclei of cortical neurons. Similar induction of Sp1 and Sp3 protein is also observed in neurons in vivo in a chemical or a genetic model of Huntington's disease, two rodent models in which neuronal loss has been attributed to oxidative stress. Sustained high-level expression of full-length Sp1 or full-length Sp3, but not the Sp1 zinc finger DNA-binding domain alone, prevents death in response to oxidative stress, DNA damage, or both. Taken together, these results establish Sp1 and Sp3 as oxidative stress-induced transcription factors in cortical neurons that positively regulate neuronal survival.

Histone deacetylase inhibitors prevent oxidative neuronal death independent of expanded polyglutamine repeats via an Sp1-dependent pathway

Oxidative stress is believed to be an important mediator of neurodegeneration. However, the transcriptional pathways induced in neurons by oxidative stress that activate protective gene responses have yet to be fully delineated. We report that the transcription factor Sp1 is acetylated in response to oxidative stress in neurons. Histone deacetylase (HDAC) inhibitors augment Sp1 acetylation, Sp1 DNA binding, and Sp1-dependent gene expression and confer resistance to oxidative stress-induced death in vitro and in vivo. Sp1 activation is necessary for the protective effects of HDAC inhibitors. Together, these results demonstrate that HDAC inhibitors inhibit oxidative death independent of polyglutamine expansions by activating an Sp1-dependent adaptive response.

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.

Establishment of red fluorescent protein-tagged HeLa tumor metastasis models: determination of DsRed2 insertion effects and comparison of metastatic patterns after subcutaneous, intraperitoneal, or intravenous injection

Metastasis is the leading cause of death in patients with cervical cancer. In this report, we establish novel fluorescent HeLa tumor metastasis models to determine whether HeLa transfected with the enhanced red fluorescent protein (DsRed2) gene in vitro and xenotransplanted through subcutaneous, intraperitoneal, or intravenous route into SCID mice would permit the detection of tumor micro-metastasis in vivo. Our results showed that DsRed2 insertions did not interfere the tumorigenic properties of HeLa cells. We also demonstrated that DsRed2-transduced HeLa cells maintained stable high-level DsRed2 expressions during their growth in vivo. DsRed2 fluorescence clearly demarcated the primary seeding place and readily allowed for the visualization of distant micro-metastasis and local invasion at the single-cell level. Lung metastasis, the major cause of cervical carcinoma related death, was found in all three models. However, intravenous injections of the HeLa-DsRed2 cells established tumor foci in the lung, while subcutaneous and intraperitoneal injections only established lung metastasis at single-cell levels. The DsRed2 tagged HeLa cancer model allowed detection and investigation of physiologically relevant patterns of cancer invasion and metastasis in vivo.

Preclinical studies of gene transfer for the treatment of desmoid disease in familial adenomatous polyposis

BACKGROUND

Familial adenomatous polyposis (FAP) arises following mutation or loss of the adenomatous polyposis coli (APC) gene. Desmoid tumours are proliferations of fibroblasts and occur as an extracolonic manifestation of FAP. They are a leading cause of death after colectomy. The aim of this study was to assess the potential for APC gene transfer into fibroblasts in vitro and in vivo as a basis for consideration of gene therapy in the prevention or treatment of desmoid tumours.

METHODS

The APC gene was transferred by lipofection into fibroblasts in tissue culture and into peritoneum and small bowel mesentery in vivo. Reverse transcriptase-polymerase chain reaction was used to determine whether or not transfection was successful.

RESULTS

Transgene expression was recorded in vitro to 7 days after transfection. High levels of transgene expression were also seen in samples of peritoneum (all eight mice), small bowel mesentery (seven of eight), liver (seven of eight) and intestinal tissues (five to six of eight) following intraperitoneal treatment. Interestingly, transgene expression in gonadal tissues was occasionally noted.

CONCLUSION

Liposomal transfection of APC gave prolonged high-level expression of the transgene, an important basis for gene therapy. No adverse effects were recorded. Further work is needed in animal models of desmoid disease to assess the clinical effects of gene therapy.

Growth suppression and immunogenicity enhancement of Hep-2 or primary laryngeal cancer cells by adenovirus-mediated co-transfer of human wild-type p53, granulocyte-macrophage colony-stimulating factor and B7-1 genes

Co-transfer of immunomodulatory and antiproliferative genes may be the basis for new strategies to potentiate tumor regression. In this study, we evaluated the in vitro effect of the introduction of human wild-type p53, granulocyte-macrophage colony-stimulating factor (GM-CSF), and B7-1 genes via recombinant adenovirus on the growth and immunogenicity of Hep-2 or primary laryngeal cancer cells. By the introduction of wild-type p53 gene, the growth of Hep-2 cells was inhibited via enhanced apoptosis. By the introduction of GM-CSF and B7-1 genes, the immunogenicity of cancer cells was enhanced. Significant proliferation of tumor infiltrating lymphocytes (TILs) and tumor-specific cytotoxicity of cytotoxic T lymphocytes (CTLs) were induced in vitro. Furthermore, the combinative effect of GM-CSF and B7-1 was even more evident than that of any one of them singly. These results suggest that the co-transfer of human wild-type p53, GM-CSF and B7-1 genes into tumor cells via recombinant adenovirus may be further developed into a potential combination gene therapy strategy for cancer.

Intraperitoneal gene delivery mediated by a novel cationic liposome in a peritoneal disseminated ovarian cancer model

We have previously synthesized a new cationic liposome that displays high efficiency and low toxicity, 3 beta[l-ornithinamide-carbamoyl] cholesterol (O-Chol), using solid-phase synthesis. In this study, O-Chol was applied to in vitro and in vivo models of ovarian cancer. Intraperitoneal gene delivery for peritoneal disseminated ovarian cancer in nude mice was achieved using a stable chloramphenicol acetyl transferase (CAT)-expressing ovarian cancer cell line (OV-CA-2774/CAT), which allowed us to quantify the exact tumor burden of organs. When luciferase and beta-galactosidase genes were used as reporter genes, O-Chol showed better efficiency than other commercial transfection reagents such as lipofectin, lipofectAMINE, DC-Chol, and FuGENE 6, both in vitro and in vivo. Moreover, the transfection efficiency of this new cationic lipid reagent remained high in serum-containing medium and under serum-free conditions. Furthermore, in vivo transfection with O-Chol showed high levels of gene expression specific to peritoneal tumor cells. Consequently, the O-Chol:DNA lipoplex appears to offer potential advantages over other commercial transfection reagents because of (1) its higher level of gene expression in vitro and in vivo; (2) its reduced susceptibility to serum inhibition; and (3) its highly selective transfection into tumor cells. These results suggest that the O-Chol:DNA lipoplex is a promising tool in gene therapy for patients with peritoneal disseminated ovarian cancer.

Comparisons of tumor suppressor p53, p21, and p16 gene therapy effects on glioblastoma tumorigenicity in situ

The mutation and/or deletion of tumor suppressor genes have been postulated to play a major role in the genesis and the progression of gliomas. In this study, the functional expression and efficacy in tumor suppression of 3 tumor suppressor genes (p53, p21, and p16) were tested and compared in a rat GBM cell line (RT-2) after retrovirus mediated gene delivery in vitro and in vivo. Significant reductions in tumor cell growth rate were found in p16 and p21 infected cells (60 +/- 12% vs 66 +/- 15%) compared to p53 (35 +/- 9%). In vitro colony formation assay also showed significant reductions after p16 and p21 gene delivery (98 +/- 5% vs 91 +/- 10%) compared to p53 (50 +/- 18%). In addition, the tumor suppression efficacy were investigated and compared in vivo. Retroviral mediated p16 and p21 gene deliveries in glioblastomas resulted in more than 90% reductions in tumor growth (92 +/- 26% vs 90 +/- 22%) compared to p53 (62 +/- 18%). Tumor suppressor gene insertions in situ further prolonged animal survival. Overall p16 and p21 genes showed more powerful tumor suppressor effects than p53. The results were not surprising, as p16 and p21 are more downstream in the cell cycle regulatory pathway compared to p53. Moreover, the mechanism involved in each of their suppressor effects is different. This study demonstrates the feasibility of using tumor suppressor genes in regulating the growth of glioma in vitro and in situ.

Growth suppression of established human osteosarcoma lung metastases in mice by aerosol gene therapy with PEI-p53 complexes

Lung metastases are a frequent complication of osteosarcoma and a treatment that would reduce the severity of this complication would be of great benefit to patients. We have used a formulation consisting of polyethyleneimine (PEI) and a p53 gene administered in aerosol to treat established lung micrometastases as a model of human osteosarcoma in nude mice. The SAOS-LM6 cell line, a metastatic derivative of the p53 null SAOS-2 line, expresses high levels of p53 protein after in vitro transfection with PEI-p53 complexes as determined by ELISA, and transfection with both p53wt and the p53 variant, p53-CD(1-366) in vitro, results in a marked inhibition of SAOS-LM6 cell proliferation. Aerosol delivery of plasmid DNA containing either the p53 gene or a p53-CD(1-366) variant gene formulated with PEI to mice resulted in highly significant reductions in the numbers and size of tumors (P<.001), the total number of tumor foci in the lungs (P<.001) and the size of individual tumor nodules in treated animals compared to untreated, PEI only-treated and PEI-CAT-treated control animals. The different tissues examined did not reveal any signs of toxicity or inflammation after repeated exposure to PEI-DNA. The aerosol delivery of PEI-based formulations of p53 or synthetic p53 variant genes represents a promising new strategy for the treatment of established human osteosarcoma lung metastases. The noninvasive nature of aerosol delivery coupled with low toxicity also make this therapeutic approach potentially appropriate for combination therapy with either radio- or chemotherapy.

Targeting tumor angiogenesis with gene therapy

A recent target of cancer gene therapy is tumor angiogenesis. An appealing feature of gene therapy targeting the tumor vasculature is that it is readily accessible, particularly when the carrier and its gene are administered systemically. Several gene-based viral and nonviral therapies that target tumor angiogenesis have demonstrated the "proof of principle" of antiangiogenic therapy in preclinical models. The utility of antiangiogenic gene therapy in a clinical setting will depend in large part on developing vectors with minimal toxicity and with increased in vivo transfection efficiency. In this review, we discuss the current status and future directions of antiangiogenic gene therapy.

Caspase-9 transduction overrides the resistance mechanism against p53-mediated apoptosis in U-87MG glioma cells

OBJECTIVE

Conflicting reports have been published with regard to the relationship between the efficacy of p53 gene therapy and the p53 status of gliomas. In this study, we evaluated whether U-87MG glioma cells harboring wild-type p53 and U251 and U-373MG glioma cells harboring mutated p53 demonstrate different sensitivities to p53-induced apoptosis. In addition, we tested whether transduction of Bax or caspase-9, which are downstream components of p53-induced apoptosis, can override the resistance mechanism of U-87MG cells to apoptosis.

METHODS

We transduced U-87MG, U251, and U-373MG glioma cells with p53, Bax, or caspase-9 genes via adenovirus (Adv) vectors, to induce the same level of respective proteins, and evaluated the degree of apoptosis.

RESULTS

U-87MG cells were highly resistant to Adv for p53 (Adv-p53)-mediated apoptosis, whereas U251 and U-373 cells underwent extensive apoptosis after Adv-p53 infection. In U-87MG cells, the elevation of Bax and Fas was not as marked as that observed in U251 and U-373MG cells after Adv-p53 infection. Endogenous expression of Bcl-XL and Bcl-2 in U-87MG cells was greater than that in U251 and U-373MG cells. U-87MG cells were more resistant to Bax-mediated apoptosis than were U251 or U-373MG cells. In contrast, U-87MG cells were more sensitive to caspase-9-mediated apoptosis than were U251 or U-373MG cells, suggesting that transduction of caspase-9 may override the resistance mechanism of U-87MG to p53-mediated apoptosis.

CONCLUSION

These results demonstrate that proapoptotic function induced by p53 transduction in U-87MG cells was repressed at several steps and that induction of caspase-9 may circumvent this resistance mechanism.

Co-transfer of human wild-type p53 and granulocyte-macrophage colony-stimulating factor genes via recombinant adenovirus induces apoptosis and enhances immunogenicity in laryngeal cancer cells

Co-transfer of immunomodulatory and anti-proliferative genes may be the basis for new strategies to enhance tumor regression. The purpose of this study was to develop a combination gene therapy strategy for the treatment of laryngeal cancer. Human wild-type p53 and granulocyte-macrophage colony-stimulating factor (GM-CSF) genes were transferred into human laryngeal cancer cells mediated by adenovirus type 5 vector co-expressing human wild-type p53 and GM-CSF (Ad-p53/GM-CSF). By the introduction of the wild-type p53 gene, the growth of human laryngeal cancer Hep-2 cells was inhibited and their apoptosis was induced. By the introduction of the GM-CSF gene, the immunogenicity of cancer cells was enhanced. Significant proliferation of tumor infiltrating lymphocytes and tumor-specific cytotoxicity of cytotoxic T lymphocytes were induced by Ad-p53/GM-CSF-infected cancer cells in vitro. The results suggest that the co-transfer of human wild-type p53 and GM-CSF genes into tumor cells via recombinant adenovirus may be further developed into an effective and practical combination gene therapy strategy for laryngeal cancer.

A Novel mRNA-cDNA interference phenomenon for silencing bcl-2 expression in human LNCaP cells

The templates required for inducing posttranscriptional gene silencing (PTGS) effects have been investigated in human prostate cancer LNCaP cells. Transfection of a mRNA-cDNA hybrid construct was found to result in a relatively long-term interference of specific gene expression. Androgen-stimulated expression of bcl-2 has been reported to increase the tumorigenic and metastatic potentials of human prostate cancer LNCaP cells, as well as their resistance to many apoptotic stimuli. The addition of bcl-2 antisense oligonucleotides, however, restored apoptosis. Our studies demonstrate gene silencing effects of the mRNA-cDNA transfection that is similar to those of PTGS/RNAi in this in vitro prostate cancer cell model. A potential RNA-directed RNA polymerase activity was also detected which is alpha-amanitin-sensitive. These findings indicate that a novel gene silencing system may exist in mammalian cells.

Gene therapy for high grade gliomas

High grade gliomas in adults are devastating diseases, with very poor survival despite their lack of distant metastases. Local treatments, such as surgical resection and stereotactic radiosurgery, have been most successful, whereas systemic therapy (for example, chemotherapy and immunotherapy) have been rather disappointing. Several gene therapy systems have been successful in controlling or eradicating these tumours in animal models and are now being tested as a logical addition to current clinical management. This review describes the gene therapy clinical protocols that have been completed or that are ongoing for human gliomas. These include the prodrug activating system, herpes simplex thymidine kinase (HSVtk)/ganciclovir (GCV), utilising either retrovirus vector producer cells or adenovirus vectors; adenovirus mediated p53 gene transfer; adenovirus mediated IFN-beta gene transfer and oncolytic herpes virus and adenovirus vectors. To date, all of the clinical studies have used direct injection of the vector into the glioma. The Phase I clinical studies have demonstrated low to moderate toxicity and variable levels of gene transfer and in some cases anti-tumour effect. Future directions will rely upon improvements in gene delivery as well as gene therapies and combinations of gene therapy with other treatment modalities.

Successful treatment of primary and disseminated human lung cancers by systemic delivery of tumor suppressor genes using an improved liposome vector

Delivery of therapeutic genes to disseminated tumor sites has been a major challenge in the field of cancer gene therapy due to lack of an efficient vector delivery system. Among the various vectors currently available, liposomes have shown promise for the systemic delivery of genes to distant sites with minimal toxicity. In this report, we describe an improved extruded DOTAP:cholesterol (DOTAP:Chol) cationic liposome that efficiently delivers therapeutic tumor suppressor genes p53 and FHIT, which are frequently altered in lung cancer, to localized human primary lung cancers and to experimental disseminated metastases. Transgene expression was observed in 25% of tumor cells per tumor in primary tumors and 10% in disseminated tumors. When treated with DOTAP:Chol-p53 and -FHIT complex, significant suppression was observed in both primary (P < 0.02) and metastatic lung tumor growth (P < 0.007). Furthermore, repeated multiple treatments revealed a 2.5-fold increase in gene expression and increased therapeutic efficacy compared to single treatment. Finally, animal survival experiments revealed prolonged survival (median survival time: 76 days, P < 0.001 for H1299; and 96 days, P = 0.04 for A549) when treated with liposome-p53 DNA complex. Our findings may be of importance in the development of treatments for primary and disseminated human lung cancers.

Inhibition of experimental lung metastasis by aerosol delivery of PEI-p53 complexes

Mutations in the p53 tumor suppressor gene and the pathways mediated by the p53 protein are common in many human cancers. Replacement of functional p53 by gene therapy is a potential way of combating these cancers and the associated drug resistance and tumor growth. Aerosol delivery of genes is a noninvasive way of targeting genes to the lung for gene therapy. Here we demonstrate, using a murine melanoma lung metastasis model, that aerosol delivery of polyethyleneimine-p53 (PEI-p53) complexes inhibits the growth of lung metastasis. A significantly reduced number of visible foci were observed in C57BL/6 mice injected with B16-F10 melanoma and treated with PEI-p53 complexes by aerosol for 3 weeks at twice a week. Fifty percent of the mice in the PEI-p53-treated group exhibited no visible tumor foci. There was a significant reduction in the lung weights of p53-treated mice (P < 0.01) compared to control groups. The tumor burden was also significantly lower (P < 0.001) in mice treated with PEI-p53 complexes. No extrapulmonary metastasis was observed in the groups treated with PEI-p53 complexes compared to 50% of the mice in control groups, which showed metastasis to lymph nodes in the neck or abdomen. Treatment with PEI-p53 aerosol also led to about a 50% increase in the mean length of survival of the mice injected with B16-F10 cells. These data suggest that delivery of the p53 gene by aerosol using PEI as the gene delivery vector can inhibit the growth of lung metastasis.

Norcantharidin-induced post-G(2)/M apoptosis is dependent on wild-type p53 gene

Norcantharidin (NCTD), a synthetic analogue of phosphatase type 2A inhibitors, cantharidin, was shown to have limited effects in treating human and animal tumors. The tumor cell killing mechanisms by norcantharidin, however, remain unclear. In this report, we wished to investigate the mechanisms of norcantharidin-mediated cytotoxicity. Effort was made to investigate whether norcantharidin exerted its cytotoxicity through a p53-dependent or -independent mechanism. RT-2 (wtp53) and U251 (mutant p53) glioblastoma cell lines were exposed to norcantharidin at different dosages. Time-course fluorescent-activated cell sorting (FACS) analysis showed that high doses of norcantharidin arrested the cells at the G(2)/M phase and subsequent post-G(2)/M apoptosis in RT-2 cell line. In comparison, the U251 cell line was found resistant to norcantharidin-induced cytotoxicity. Restoring wild-type p53 gene function in the U251 cell line after adenoviral infections induced tumor cell cytotoxicity after exposure to norcantharidin. These results showed that norcantharidin kills tumor cells efficiently corresponding to their endogenous p53 gene status. The results also showed the feasibility of using adenoviral p53 gene therapy to enhance chemosensitivity of tumor cells to norcantharidin.

Genetic basis of intramedullary spinal cord tumors and therapeutic implications

The advent of molecular biology has provided tools to delineate genetic mutations that cause disease. Recently, several genetic mutations have been associated with intramedullary spinal cord tumors. Concurrently, advances in micro-neurosurgical techniques have significantly decreased the morbidity of surgical resection. In this review, we describe the current understanding of genetic mutations in sporadic and familial intramedullary spinal cord tumors. The future success of innovative gene therapy protocols may depend upon establishing a cause and effect relationship between these genetic mutations and disease progression. Successful gene therapy will also depend upon increasing the efficiency of gene therapy vector delivery.

Gene therapy of brain tumors: problems presented by physiological barriers

The explosion of molecular techniques for gene discovery and their application to a variety of diseases has uncovered numerous gene abnormalities that can result in disease. These discoveries have provided the needed understanding and genetic materials to apply gene therapy approaches in the treatment of several diseases, including those of the central nervous system. A variety of different anticancer complementary DNAs (cDNA) have been shown to possess biological efficacy when used in the appropriate experimental setting. However, efficient and effective delivery of these cDNAs remains a major obstacle for future clinical applications. The focus of this review will be to describe the obstacles that impede the process of gene therapy and oncolytic viral therapy of brain tumors and to describe how important new discoveries derived from other disciplines are being used to address problems encountered in the gene/ viral therapy of this disease.

Antiangiogenic Gene Therapy in Cancer

One of the most recent and exciting approaches in cancer gene therapy is the ability to target the developing blood supply of the tumor. An appealing feature of antiangiogenic gene therapy is that the tumor vasculature is a readily accessible target, particularly when the carrier and its gene are administered systemically. This is in contrast to several other gene therapy approaches in which the tumor vasculature represents a major obstacle to achieving high levels of transfection of the tumor cells. Several gene-based viral or non-viral therapies that target tumor angiogenesis have shown efficacy in pre-clinical models. Genes that encode antiangiogenic polypeptides such as angiostatin and endostatin have significantly inhibited tumor growth, inducing a microscopic dormant state. The products of these genes are thought to act extracellularly to inhibit angiogenesis. An alternative approach that investigators have used successfully in tumor-bearing mice is to target angiogenic growth factors or their receptors that are essential for tumor growth. Levels of angiogenic factors such as vascular endothelial growth factor (VEGF) have been reduced by either antisense methods or the use of genes encoding truncated angiogenic decoy receptors. Despite these promising findings of tumor reduction with antiangiogenic gene therapy, advances in the viral and/or non-viral delivery systems are essential for this therapy to have clinical utility. In this review, we will discuss the mechanisms of angiogenesis/antiangiogenesis, and the current status and future directions of antiangiogenic gene therapy.

Suppression of activin-induced apoptosis by novel antisense strategy in human prostate cancer cells

Apoptosin, a novel gene encoding a mitotic kinase-motif protein, is stimulated by activin, a member of TGF-beta family, in human LNCaP prostate cancer cells and in patient tissues. We employed a gene knockout methodology based on the covalent bonding of chemically modified antisense probes to apoptosin mRNAs in LNCaP cells. The mRNA-antisense hybrid duplexes were neither translated nor post-transcriptionally modified, resulting in no protein synthesis. Introducing antisense apoptosin into activin-induced apoptotic LNCaP cells prevented apoptosis, interfered with genomic DNA fragmentation and released cell cycle checkpoint. These findings suggest that the apoptosin, in addition to p53, is important in apoptotic regulation of human prostate cancers.

Evaluation of cationic liposome suitable for gene transfer into pregnant animals

Cationic liposome-mediated in vivo gene transfer represents a promising approach for somatic gene therapy. To assess the most suitable liposome for gene delivery into a wide range of organs and fetuses in mice, we have explored several types of cationic liposomes conjugated with plasmid DNA carrying the beta-galactosidase gene through intravenous injection into pregnant animals. Transduction efficiency was assessed by Southern blot analysis and expression of the transferred gene was evaluated by enzymatic demonstration of beta-galactosidase activity. Through the analysis of several types of recently synthesized cationic liposome/lipid formulations, DMRIE-C reagent, a liposome formulation of the cationic lipid DMRIE (1, 2-dimyristyloxypropyl-3-dimethyl-hydroxy ethyl ammonium bromide) and cholesterol in membrane-filtered water met our requirements. When the plasmid DNA/DMRIE-C complexes were administered intravenously into pregnant mice at day 11.5 post coitus (p.c.), transferred genes were observed in several organs in dams and were expressed. Furthermore, although the copy numbers transferred into embryos were low, we observed reporter gene expression in the progeny.

Gene transfer technologies for malignant gliomas

Although early clinical gene therapy trials for recurrent central nervous system neoplasms showed the proof-of-principle, they did not fulfill the high expectations suggested by the preclinical experimental data. Insufficient distribution of vectors in human brain tumors and very low transduction efficiency require that we reevaluate gene transfer concepts for brain tumor treatment. Major steps to improve gene transfer into the central nervous system and the efficacy of gene therapy for malignant brain tumors include: 1) the design of more effective vector systems; 2) the development of new or improved prodrug/suicide systems, gene replacement approaches, or strategies targeting the immune response or tumor angiogenesis; 3) the study of new techniques to enhance delivery of genetic vectors into brain tumors and for monitoring gene delivery into tumors; and 4) assessment of the role of gene therapy as part of a combined treatment approach.

Cationic liposome mediated transgene expression in the guinea pig cochlea

Sensorineural hearing loss affects nearly 10% of the American population that is refractory to conventional therapy. Gene therapy represents an intervention with potential therapeutic efficacy. We studied the feasibility of cationic liposome mediated gene transfer within the guinea pig cochlea in vivo following direct microinjection into the cochlea. Transgene expression was persistent up to 14 days in the neurosensory epithelia and surrounding tissue without toxicity and inflammation in the target organ. This study represents the first successful use of cationic liposomes for cochlear gene transfer thus providing a safe and rapid alternative to the use of recombinant viral vectors in gene therapy for inner ear disorders.

A DNA controlled-release coating for gene transfer: transfection in skeletal and cardiac muscle

In this paper we report a novel technique of DNA-polymer coating for gene transfer. A proprietary DNA polymer solution was used for thin-layer coating on a chromic gut suture as a model study. The coated sutures were characterized for physical properties such as coating thickness, mass of the DNA deposited on the suture, surface characteristics as determined by scanning electron microscopy, and in vitro DNA release characteristics under simulated physiologic conditions. The in vivo gene transfection using DNA-coated sutures was demonstrated in rat skeletal muscle and in canine atrial myocardium. A heat-stable human placental alkaline phosphatase (AP) plasmid was used as a marker gene. Incisions of 1 to 1.5 cm were made in the rat skeletal muscles or the canine atrial myocardium. The sites were closed with either the DNA-coated sutures or control sutures. Two weeks after the surgery, the tissue samples adjacent to the suture lines were retrieved and analyzed for AP activity. The DNA-coated sutures demonstrated a sustained release of the DNA under in vitro conditions, with an approximately 84% cumulative DNA release occurring in 26 days. An agarose gel electrophoresis of the DNA samples released from the suture demonstrated two bands, with the lower band corresponding to the input DNA (supercoiled). It seems that there was a partial transformation of the DNA from a supercoiled to an open circular form due to the polymer coating. The tissue sites, which received the DNA-coated sutures, demonstrated a significantly higher AP activity compared with the tissue sites that received control sutures. In the rat studies, the mean AP activity (square root of cpm/microgram protein) was 43.6 +/- 3.3 vs 20.6 +/- 2.1 (p = 0.001) at the control sites. Similarly, in the canine studies, the AP activity was 73.6 +/- 7.4 Vs 21.6 +/- 1.4 (p = 0.0009) at the control sites. Thus, our studies demonstrated a successful gene transfer using our DNA-polymer coating technique. This technique could be useful for coating sutures used in vascular and general surgery, and also for coating medical devices, such as stents, catheters, or orthopedic devices, to achieve a site-specific gene delivery.

Application of lipids and plasmid design for gene delivery to mammalian cells

Cationic lipids are widely used for in vitro gene transfer due to their efficiency. The major challenges for the improvement of in vivo cationic lipid-mediated gene delivery reside in the design of more biocompatible lipoplexes mimicking viral-mediated gene delivery and in understanding the fate of the lipoplexes within the cells.

Gene therapy for malignant gliomas

Malignant gliomas are attractive targets for gene therapy because of their relatively well-localized distribution. Several new strategies have been devised that target different aspects of glioma biology. Gene transfer can be used to synthesize chemotherapy drugs that block DNA synthesis within these highly mitotic tumors. New genes can be introduced that restore the functions of mutated tumor suppressor genes or block the molecular pathways needed for tumor angiogenesis. Alternatively, the immune response to these tumors can be augmented by the local production of cytokines. Finally, viruses themselves can be used as tumoricidal agents by designing viruses that selectively replicate and destroy tumor cells. The advantages and limitations of these approaches are discussed in the context of their possible application to the treatment of these highly lethal malignancies.

Combination therapy with interleukin-2 and wild-type p53 expressed by adenoviral vectors potentiates tumor regression in a murine model of breast cancer

Although cytokine gene transfer for cancer treatment can stimulate immune recognition and tumor regression in animal models, there is still a need for improvements to these strategies. In this study, we examined the efficacy of a combination gene therapy using adenovirus (Ad) 5 vectors expressing human interleukin-2 and the wild-type (wt) human p53 gene under control of the human cytomegalovirus immediate early promoter (AdIL-2 and Adp53wt, respectively). Infected murine cell lines and primary mouse tumor cells secreted high levels of IL-2 and over expressed the p53 protein for at least 9 days. After infection of cells with Adp53wt, DNA synthesis was significantly inhibited and apoptosis was induced within 3-5 days. Both vectors were tested in a transgenic mouse mammary adenocarcinoma model for antitumor response. Following a single intratumoral injection of mice bearing PyMT induced tumors, the combination of Adp53wt (1 x 10(9) pfu) plus a relatively low dose of AdIL-2 (1.5 x 10(8) pfu) caused regressions in 65% of the treated tumors without toxicity. Fifty percent of the treated mice remained tumor free and were immune to rechallenge with fresh tumor cells. In contrast, injection of either vector alone at this does resulted in only a delay in tumor growth. Only mice co-injected with Adp53wt and AdIL-2 showed specific antitumor cytolytic T lymphocyte (CTL) activity, indicating that the immune response involved in tumor regression was promoted by the combination therapy. These results suggest that cancer treatment strategies involving combined delivery of immunomodulatory and antiproliferative genes may be highly effective.