Translation of the radio- and chemo-inducible TNFerade vector to the treatment of human cancers

Apoptosis-Inducing TNF Superfamily Ligands for Cancer Therapy

Cancer is a complex disease with apoptosis evasion as one of its hallmarks; therefore, apoptosis induction in transformed cells seems a promising approach as a cancer treatment. TNF apoptosis-inducing ligands, which are naturally present in the body and possess tumoricidal activity, are attractive candidates. The most studied proteins are TNF-α, FasL, and TNF-related apoptosis-inducing ligand (TRAIL). Over the years, different recombinant TNF family-derived apoptosis-inducing ligands and agonists have been designed. Their stability, specificity, and half-life have been improved because most of the TNF ligands have the disadvantages of having a short half-life and affinity to more than one receptor. Here, we review the outlook on apoptosis-inducing ligands as cancer treatments in diverse preclinical and clinical stages and summarize strategies of overcoming their natural limitations to improve their effectiveness.

Feasibility of Bone Marrow Mesenchymal Stem Cell-Mediated Synthetic Radiosensitive Promoter-Combined Sodium Iodide Symporter for Radiogenetic Ovarian Cancer Therapy

Ovarian cancer is the most lethal gynecological cancer, most patients relapse within 12-24 months, and eventually die, especially platinum-resistant patients. Gene therapy has been one of the most potential methods for tumor treatment. Bone marrow mesenchymal stem cells (BMSCs) have been used for systemic delivery of therapeutic genes to solid tumors. Sodium iodide symporter (NIS) is an intrinsic membrane glycoprotein and can concentrate ¹³¹I, which is important for radionuclide therapy and nuclear medicine imaging in recent years. However, the rapid iodine efflux has become a bottleneck for NIS-mediated radionuclide gene therapy. Our previous studies found that the early growth response-1 (Egr1) promoter containing CC(A/T)6GG (CArG) elements had an ¹³¹I radiation-positive feedback effect on the NIS gene. Other research showed the synthesized Egr1 promoter containing four CArG elements, E4, was nearly three times as sensitive as the Egr1 promoter. In our study, BMSC-E4-NIS was engineered to express NIS under the control of E4 promoter using lentivirial vectors. After BMSC-E4-NIS implantation, no tumors were seen in BALB/c nude mice and BMSC-E4-NIS did not promote the growth of SKOV3 tumor. BMSCs migrated toward ovarian cancer samples in chemotaxis assays and to ovarian tumors in mice. Using micro-single-photon emission computed tomography/computed tomography (SPECT/CT) imaging, we found that E4 promoter produced a notable increase in ¹²⁵I uptake after ¹³¹I irradiation, the radionuclide uptake is almost three and six times more than Egr1 and cytomegalovirus (CMV) promoters. These studies confirmed the feasibility of using BMSCs as carriers for lentivirus-mediated E4-NIS gene therapy for ovarian cancer. Further research on BMSC-E4-NIS gene therapy for ovarian cancer in vivo will also be carried on, and if successful, this might provide a new adjuvant therapeutical option for platinum-resistant ovarian cancer patients and provide a new method for dynamic evaluation of curative effect.

Lentiviral vector with a radiation-inducible promoter, carrying the ING4 gene, mediates radiosensitization controlled by radiotherapy in cervical cancer cells

The presence of hypoxia in solid tumors is considered one of the major factors that contribute to radiation resistance. The aim of the present study was to establish a therapeutic system, which can be controlled by radiation itself, to enhance radiosensitivity. For this purpose, a lentiviral gene therapy vector containing the human inhibitor of growth 4 (ING4) and its upstream promoter, human early growth response factor-1 (EGR1), which possesses the radiation-inducible characteristics to activate the transcription of its downstream genes, was constructed. Downstream fluorescence proteins were investigated to ensure that the EGR1 promoter was induced by irradiation. Furthermore, ING4 open reading frame (ORF) expression was detected by western blotting. The cell cycle was analyzed by fluorescence-activated cell sorting analysis 48 h after the cells were exposed to X-rays ranging between 0 and 8 Gy. In cells stably and transiently transfected with reporter plasmids, the EGR1-driver gene was sensitive to ionizing irradiation. Furthermore, irradiation-induced ING4 gene expression was observed. The enhanced ING4 expression increased the number of cells in the G₂/M phase and decreased the proportion of cells in the G₁/S phase. Therefore, ING4 expression inhibited cell proliferation and was associated with less colonies being formed. Furthermore, ING4 suppressed hypoxia-inducible factor 1α expression under hypoxic conditions and promoted cell apoptosis. Overall, these results revealed that combining the EGR1 promoter and ING4 ORF using a lentivirus system may be a promising therapeutic strategy with which to enhance radiosensitivity controlled by radiation. However, further studies using in vivo models are required to confirm these findings.

GADD45α-targeted suicide gene therapy driven by synthetic CArG promoter E9NS sensitizes NSCLC cells to cisplatin, resveratrol, and radiation regardless of p53 status

Background: GADD45α is a tumor suppressor protein often upregulated by environmental stresses and DNA-damage agents to cause growth arrest, apoptosis, tumor growth inhibition, and anti-angiogenesis. A novel suicide gene therapy vector pE9NS.G45α was engineered by cloning GADD45α opening reading frame downstream to the synthetic CArG promoter E9NS, which contains nine repeats of CArG element with modified core A/T sequence and functions as a molecular switch to drive the expression of GADD45α. The current study aims to determine the efficacy of this suicide gene therapy vector in combination with cisplatin, resveratrol, and radiation in NSCLC cell lines with various p53 statuses. Methods: Three NSCLC cell lines, H1299 (deleted p53), A549 (wild-type p53), and H23 (mutated p53), were examined in the present investigation to represent NSCLC with different p53 functions. MTT assay was conducted to select suitable doses of cisplatin, resveratrol, and radiation for gene therapy, and dual luciferase assay was performed to validate the activation of promoter E9NS. The efficacy of gene therapy combinations was evaluated by the amount of GADD45α expression, cell survival, and apoptosis. Results: All the combinations successfully activated promoter E9NS to elevate intracellular GADD45α protein levels and subsequently enhanced cell viability reduction and apoptosis induction regardless of p53 status. Conclusion: Our study demonstrates that GADD45α-targeted suicide gene therapy controlled by synthetic promoter E9NS sensitizes NSCLC cells to cisplatin, resveratrol, and radiation and is effective against NSCLC at least in vitro.

Stimulating Innate Immunity to Enhance Radiation Therapy-Induced Tumor Control

Novel ligands that target Toll-like receptors and other innate recognition pathways represent a potent strategy for modulating innate immunity to generate antitumor immunity. Although many of the current clinically successful immunotherapies target adaptive T-cell responses, both preclinical and clinical studies suggest that adjuvants have the potential to enhance the scope and efficacy of cancer immunotherapy. Radiation may be a particularly good partner to combine with innate immune therapies, because it is a highly efficient means to kill cancer cells but may fail to send the appropriate inflammatory signals needed to act as an efficient endogenous vaccine. This may explain why although radiation therapy is a highly used cancer treatment, true abscopal effects-regression of disease outside the field without additional systemic therapy-are extremely rare. This review focuses on efforts to combine innate immune stimuli as adjuvants with radiation, creating a distinct and complementary approach from T cell-targeted therapies to enhance antitumor immunity.

Systemic delivery of the tumor necrosis factor gene to tumors by a novel dual DNA-nanocomplex in a nanoparticle system

Many cancers fail to respond to immunotherapy as a result of immune suppression by the tumor microenvironment. The exogenous expression of immune cytokines to reprogram the tumor microenvironment represents an approach to circumvent this suppression. The present studies describe the development of a novel dual nanoparticle (DNP) system for driving DNA expression vectors encoding inflammatory cytokines in tumor cells. The DNP system consists of a DNA expression vector-cationic peptide nanocomplex (NC) surrounded by a diblock polymeric NP. Tumor necrosis factor alpha (TNF) was selected as the prototype cytokine for this system, based on its pleotropic inflammatory and anti-cancer activities. Our results demonstrate that the DNP system is highly effective in driving expression of TNF in tumor cells. We also demonstrate that the DNPs are effective in inducing apoptosis and anti-tumor activity. These findings support a novel immunotherapeutic approach for the intratumoral delivery of DNA vectors that express inflammatory cytokines.

TNFerade, an innovative cancer immunotherapeutic

Tumor necrosis factor-α (TNF-α) is a chemokine with effective tumoricidal properties. However, severe systemic toxicity limits its use of as anticancer agent. TNFerade is a novel replication deficient adenovector based gene therapy, which enables the radiation inducible translation of human TNF-α gene specifically in cancer cells. When injected intratumorally, it has least systemic distribution. Consequently, it lacks TNF-α related systemic toxicity. Evidence suggests that it has superior tumoricidal activity and tolerability with minimum adverse effects. It has demonstrated its beneficial role in the treatment of a variety of cancers in terms of improving the disease free and overall survival, delaying tumor progression, and inducing tumor regression when used with concurrent radiotherapy or chemotherapy.

CArG-driven GADD45α activated by resveratrol inhibits lung cancer cells

We report anticarcinogenic effects of suicide gene therapy that relies on the use of resveratrol-responsive CArG elements from the Egr-1 promoter to induce GADD45α. In A549 lung cancer cells, endogenous GADD45α was not induced upon resveratrol treatment. Therefore, induction of exogenous GADD45α resulted in growth inhibition. Resveratrol transiently induced Egr-1 through ERK/JNK-ElK-1. Hence, we cloned natural or synthetic Egr-1 promoter upstream of GADD45α cDNA to create a suicide gene therapy vector. Since natural promoter may have antagonized effects, we tested synthetic promoter that contains either five, six or nine repeats of CArG elements essential in the Egr-1 promoter to drive the expression of GADD45α upon resveratrol treatment. Further analysis confirmed that both synthetic promoter and natural Egr-1 promoter were able to “turn on” the expression of GADD45α when combined with resveratrol, and subsequently led to suppression of cell proliferation and apoptosis.

Immunological effects of a tumor necrosis factor alpha-armed oncolytic adenovirus

For long it has been recognized that tumor necrosis factor alpha (TNFa) has anticancer characteristics, and its use as a cancer therapeutic was proposed already in the 1980s. However, its systemic toxicity has limited its usability. Oncolytic viruses, selectively cancer-killing viruses, have shown great potency, and one of their most useful aspects is their ability to produce high amounts of transgene products locally, resulting in high local versus systemic concentrations. Therefore, the overall magnitude of tumor cell killing results from the combination of oncolysis, transgene-mediated direct effect such as TNFa-mediated apoptosis, and, perhaps most significantly, from activation of the host immune system against the tumor. We generated a novel chimeric oncolytic adenovirus expressing human TNFa, Ad5/3-D24-hTNFa, whose efficacy and immunogenicity were tested in vitro and in vivo. The hTNFa-expressing adenovirus showed increased cancer-eradicating potency, which was shown to be because of elevated apoptosis and necrosis rates and induction of various immune responses. Interestingly, we saw increase in immunogenic cell death markers in Ad5/3-d24-hTNFa-treated cells. Moreover, tumors treated with Ad5/3-D24-hTNFa displayed enhanced presence of OVA-specific cytotoxic T cells. We thus can conclude that tumor eradication and antitumor immune responses mediated by Ad5/3-d24-hTNFa offer a new potential drug candidate for cancer therapy.

Dual‑sensitive HRE/Egr1 promoter regulates Smac overexpression and enhances radiation‑induced A549 human lung adenocarcinoma cell death under hypoxia

The aim of this study was to construct an expression vector carrying the hypoxia/radiation dual‑sensitive chimeric hypoxia response element (HRE)/early growth response 1 (Egr‑1) promoter in order to overexpress the therapeutic second mitochondria‑derived activator of caspases (Smac). Using this expression vector, the present study aimed to explore the molecular mechanism underlying radiotherapy‑induced A549 human lung adenocarcinoma cell death and apoptosis under hypoxia. The plasmids, pcDNA3.1‑Egr1‑Smac (pE‑Smac) and pcDNA3.1‑HRE/Egr-1‑Smac (pH/E‑Smac), were constructed and transfected into A549 human lung adenocarcinoma cells using the liposome method. CoCl2 was used to chemically simulate hypoxia, followed by the administration of 2 Gy X‑ray irradiation. An MTT assay was performed to detect cell proliferation and an Annexin V‑fluorescein isothiocyanate apoptosis detection kit was used to detect apoptosis. Quantitative polymerase chain reaction and western blot analyses were used for the detection of mRNA and protein expression, respectively. Infection with the pE‑Smac and pH/E‑Smac plasmids in combination with radiation and/or hypoxia was observed to enhance the expression of Smac. Furthermore, Smac overexpression was found to enhance the radiation‑induced inhibition of cell proliferation and promotion of cycle arrest and apoptosis. The cytochrome c/caspase‑9/caspase‑3 pathway was identified to be involved in this regulation of apoptosis. Plasmid infection in combination with X‑ray irradiation was found to markedly induce cell death under hypoxia. In conclusion, the hypoxia/radiation dual‑sensitive chimeric HRE/Egr‑1 promoter was observed to enhance the expression of the therapeutic Smac, as well as enhance the radiation‑induced inhibition of cell proliferation and promotion of cycle arrest and apoptosis under hypoxia. This apoptosis was found to involve the mitochondrial pathway.

Efficacy and safety of dendrimer nanoparticles with coexpression of tumor necrosis factor-α and herpes simplex virus thymidine kinase in gene radiotherapy of the human uveal melanoma OCM-1 cell line

Human uveal melanoma is the most common primary intraocular tumor, and brachytherapy is one of the most common and effective treatment strategies. In order to find a safer and more effective way to increase the radio sensitivity of the tumor, we tried to use the dendrimer nanoparticle performing coexpression gene radiotherapy. In this study, we constructed recombinant DNA plasmids (early growth response-1 tumor necrosis factor-α [pEgr1-TNFα], pEgr1 thymidine kinase [TK], and pEgr1-TNFα-TK) according to the Egr1 promoter sequence. The sequences of human TNFα and herpes simplex virus (HSV) TK that were published by GenBank. Agarose gel electrophoresis and DNA sequencing had proven that we constructed the double-gene recombined plasmids pEgr1-TNF-TK correctly, as well as the plasmids pEgr1-TNFα and pEgr1-TK. The dendrimer nanoparticles combined with plasmid DNA as dendriplexes were verified with agarose gel electrophoresis and observed by transmission electron microscopy (TEM) and scanning electron microscopy to define size and shape. Zeta potential was measured using a Zetasizer analyzer. Optimal size and neutral zeta-potential characteristics of dendriplexes were achieved for the transfection studies. DNase I examination proved that the dendriplexes could protect plasmid DNA for at least 6 hours. The recombinant plasmids were transfected with dendrimer nanoparticles into the human choroidal melanoma OCM-1 cell line, followed by exposure to iodine-125 ((125)I) after transfection. After transfection with dendrimer nanoparticles and the irradiation of (125)I, the gene expressions of TNFα and HSV1-TK were significantly increased at the protein level by enzyme-linked immunosorbent assay and Western blot analysis in OCM-1 cells. The cellular morphology of OCM-1 cells altering was observed by TEM, and a decrease in cell proliferation was revealed in cell-growth curves. Flow cytometry of annexin V/propidium iodide double-dyeing apoptosis and caspase-3 fluorescence staining showed that this treatment method could turn transfected OCM-1 cells into apoptosis and necrosis by the effects of the gene expression. This study indicated that the dendrimer nanoparticles with coexpression of TNF-α and HSV1-TK gene therapy are effective and safe and can provide us with a novel strategy to treat human uveal melanoma in the future.

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.

New paradigms and future challenges in radiation oncology: an update of biological targets and technology

Radiation oncology exploits the biological interaction of radiation within tissue to promote tumor death while minimizing damage to surrounding normal tissue. The clinical delivery of radiation relies on principles of radiation physics that define how radiation energy is deposited in the body, as well as technology that facilitates accurate tumor targeting. This review will summarize the current landscape of recent biological and technological advances in radiation oncology, describe the challenges that exist, and offer potential avenues for improvement.

A phase I dose escalation study of Ad GV.EGR.TNF.11D (TNFerade™ Biologic) with concurrent chemoradiotherapy in patients with recurrent head and neck cancer undergoing reirradiation

BACKGROUND

AdGV.EGR.TNF.11D (TNFerade™ Biologic) is a replication-deficient adenoviral vector expressing human tumor necrosis factor alpha (TNF-α) under the control of the chemoradiation-inducible EGR-1 promoter. TNF-α has been shown to function as a radiation sensitizer. We conducted a phase I dose escalation study to determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of TNFerade™ Biologic, when added to chemoradiotherapy in poor prognosis patients with recurrent, previously irradiated head and neck cancer (HNC).

METHODS

TNFerade™ Biologic was injected intratumorally on day 1 of each 14-day cycle and dose-escalated in log increments from 4 × 10(9) to 4 × 10(11) PU. Daily radiation, infusional 5-fluorouracil (5-FU), and hydroxyurea were given on days 1-5 for seven cycles (FHX). Tumor biopsies were obtained before, during, and after treatment.

RESULTS

Fourteen patients were treated. DLT was reached at a dose level of 3 (4 × 10(11) PU) with three thrombotic events. The response rate was 83.3%. The median survival was 9.6 months. One patient (7.1%) remained alive 3 years after treatment. Biopsies were obtained in 90% of patients. Nearly all tumors expressed adenovirus receptors, TNF-α, and TNF-α receptors. Adenoviral DNA was detected in three biopsies from one patient.

CONCLUSIONS

TNFerade™ Biologic can be safely integrated with FHX chemoradiotherapy at an MTD of 4 × 10(10) PU. Monitoring for thrombotic events is indicated.

Nucleic acid therapeutics: concepts for targeted delivery to solid tumors

Solid tumors form a heterogeneous group of diseases, although common features such as hyperproliferation, overexpression of certain growth factor receptors and deregulated vessel formation including leaky vasculature give the opportunity to target macromolecular drug and nucleic acid carriers to tumor tissue. Similar to other macromolecular drugs, nucleic acid carriers have to be designed to enable tumor targeting after systemic injection. Chemical modification of nucleic acids makes them resistant towards enzymatic degradation. Cationic lipids or polycations condense nucleic acids into small, virus-like structures and the surface modification with hydrophilic polymers allows passive accumulation in tumor tissue; tumor cell binding ligands allow cellular targeting. To avoid toxic side effects, biodegradable and biocompatible carriers were designed. The design of thermoresponsive gene carriers allowed their selective tumor accumulation by locoregional hyperthermia. As a therapeutic concept, tumor-specific delivery of antitumoral RNA was realized in an orthotopic brain tumor model. The combination of gene- and radio-therapy enabled selective accumulation of radionuclides in tumors and boosted antitumoral effects. Hence, combining a smart delivery concept for nucleic acids with a suitable therapeutic strategy will allow successful treatment of otherwise incurable malignant diseases.

Strategies to optimize radiotherapy based on biological responses of tumor and normal tissue

Rapid developments in radiation oncology are currently taking place. Radiation-induced responses are being increasingly used for radiotherapy modification based on advancements in radiobiology. In the process of radiation treatment, radiobiological responses of tumor and normal tissue in patients are monitored non-invasively by a variety of techniques including imaging, biological methods and biochemical assays. Information collected using these methods and data on responses are further incorporated into radiotherapy optimization approaches, which not only include the optimization of radiation treatment planning, such as dose distributions in targets and treatment delivery, but also include radiation sensitivity modification and gene radiotherapy of the tumor and normal tissue. Hence, the highest tumor control rate is obtained with the utmost protection being afforded to normal tissue under this treatment modality.

Inhibition of glycogen synthase kinase-3 activity triggers an apoptotic response in pancreatic cancer cells through JNK-dependent mechanisms

Recent evidences suggest that the activity of glycogen synthase kinase-3 (GSK3) contributes to the tumorigenic potential of pancreatic cancer cells through modulation of cell proliferation and survival. However, further investigations are needed to identify GSK3-dependent mechanisms involved in the control of pancreatic cancer cell proliferation and survival. This study was undertaken to provide further support for a role of GSK3 in pancreatic cancer cell growth as well as to identify new cellular and molecular mechanisms involved. Herein, we demonstrate that prolonged inhibition of GSK3 triggers an apoptotic response only in human pancreatic cancer cells but not in human non-transformed pancreatic epithelial cells. We show that prolonged inhibition of GSK3 activity increases Bim messenger RNA and protein expressions. Moreover, we provide evidence that activation of the c-jun N-terminal kinase (JNK) pathway is necessary for the GSK3 inhibition-mediated increase in Bim expression and apoptotic response. Finally, we demonstrate that concomitant inhibition of GSK3 potentiates the death ligand-induced apoptotic response in pancreatic cancer cells but not in non-transformed pancreatic epithelial cells and that this effect also requires JNK activity. Considering that different approaches leading to stimulation of death receptor signaling are under clinical trials for treatment of unresectable or metastatic pancreatic cancer, inhibition of GSK3 could represent an attractive new avenue to improve their effectiveness.

Mesothelin confers pancreatic cancer cell resistance to TNF-α-induced apoptosis through Akt/PI3K/NF-κB activation and IL-6/Mcl-1 overexpression

Background

Previous studies showed that mesothelin (MSLN) plays important roles in survival of pancreatic cancer (PC) cells under anchorage dependent/independent conditions as well as resistance to chemotherapy. The recent success of intratumorally-injected adeno-encoded, chemo/radiation-inducible-promoter driven hTNF-α, (TNFerade) + gemcitabine in pre-clinical models of PC have renewed interest in use of TNF-α as a therapeutic component. To help find additional factors which might affect the therapy, we examined the resistance of MSLN-overexpressing pancreatic cancer cell lines to TNF-α-induced growth inhibition/apoptosis.

Methods

Stable MSLN overexpressing MIA PaCa-2 cells (MIA-MSLN), stable MSLN-silenced AsPC-1 cells (AsPC-shMSLN) and other pancreatic cells (MIA-PaCa2, Panc 28, Capan-1, BxPC3, PL 45, Hs 766T, AsPC-1, Capan-2, Panc 48) were used. NF-κB activation was examined by western blots and luciferase reporter assay. TNF-α induced growth inhibition/apoptosis was measured by MTT, TUNEL assay and caspase activation. IL-6 was measured using luminex based assay.

Results

Compared to low endogenous MSLN-expressing MIA PaCa-2 and Panc 28 cells, high endogenous MSLN-expressing Capan-1, BxPC3, PL 45, Hs 766T, AsPC-1, Capan-2, Panc 48 cells were resistant to TNF-α induced growth inhibition. Stable MSLN overexpressing MIA-PaCa2 cells (MIA-MSLN) were resistant to TNF-α-induced apoptosis while stable MSLN-silenced AsPC1 cells (AsPC-shMSLN) were sensitive. Interestingly, TNF-α-treated MIA-MSLN cells showed increased cell cycle progression and cyclin A induction, both of which were reversed by caspase inhibition. We further found that MIA-MSLN cells showed increased expression of anti-apoptotic Bcl-XL and Mcl-1; deactivated (p-Ser⁷⁵) BAD, and activated (p-Ser⁷⁰) Bcl-2. Constitutively activated NF-κB and Akt were evident in MIA-MSLN cells that could be suppressed by MSLN siRNA with a resultant increase in sensitivity of TNF-α induced apoptosis. Blocking NF-κB using IKK inhibitor wedelolactone also increased sensitivity to TNF-α-mediated cytotoxicity with concomitant decrease in Mcl-1. Blocking Akt using PI3K inhibitor also had a likewise effect presumably affecting cell cycle. MIA-MSLN cells produced increased IL-6 and were increased furthermore by TNF-α treatment. SiRNA-silencing of IL-6 increased TNF-α sensitivity of MIA-MSLN cells.

Conclusions

Our study delineates a MSLN-Akt-NF-κB-IL-6-Mcl-1 survival axis that may be operative in PC cells, and might help cancer cells' survival in the highly inflammatory milieu evident in PC. Further, for the success of TNFerade + gemcitabine to be successful, we feel the simultaneous inhibition of components of this axis is also essential.

Assessment of the evolution of cancer treatment therapies

Cancer therapy has been characterized throughout history by ups and downs, not only due to the ineffectiveness of treatments and side effects, but also by hope and the reality of complete remission and cure in many cases. Within the therapeutic arsenal, alongside surgery in the case of solid tumors, are the antitumor drugs and radiation that have been the treatment of choice in some instances. In recent years, immunotherapy has become an important therapeutic alternative, and is now the first choice in many cases. Nanotechnology has recently arrived on the scene, offering nanostructures as new therapeutic alternatives for controlled drug delivery, for combining imaging and treatment, applying hyperthermia, and providing directed target therapy, among others. These therapies can be applied either alone or in combination with other components (antibodies, peptides, folic acid, etc.). In addition, gene therapy is also offering promising new methods for treatment. Here, we present a review of the evolution of cancer treatments, starting with chemotherapy, surgery, radiation and immunotherapy, and moving on to the most promising cutting-edge therapies (gene therapy and nanomedicine). We offer an historical point of view that covers the arrival of these therapies to clinical practice and the market, and the promises and challenges they present.

Harnessing tumor necrosis factor receptors to enhance antitumor activities of drugs

Cancer is the second-leading cause of death in the U.S. behind heart disease and over stroke. The hallmarks of cancer comprise six biological capabilities acquired during the multistep development of human tumors. The inhibition of cell death pathways is one of these tumor characteristics which also include sustained proliferative signaling, evading growth suppressor signaling, replicative immortality, angiogenesis, and promotion of invasion and metastasis. Cell death is mediated through death receptor (DR) stimulation initiated by specific ligands that transmit signaling to the cell death machinery or through the participation of mitochondria. Cell death involving DR is mediated by the superfamily of tumor necrosis factor receptor (TNF-R) which includes TNF-R type I, CD95, DR3, TNF-related apoptosis-inducing ligand (TRAIL) receptor-1 (TRAIL-R1) and -2 (TRAIL-R2), DR6, ectodysplasin A (EDA) receptor (EDAR), and the nerve growth factor (NGF) receptor (NGFR). The expression of these receptors in healthy and tumor cells induces treatment side effects that limit the systemic administration of cell death-inducing therapies. The present review is focused on the different therapeutic strategies such as targeted antibodies or small molecules addressed to selective stimulated DR-mediated apoptosis or reduce cell proliferation in cancer cells.

A pilot feasibility study of TNFerade™ biologic with capecitabine and radiation therapy followed by surgical resection for the treatment of rectal cancer

OBJECTIVE

The purpose of this pilot study was to evaluate the feasibility and tolerability of weekly intratumoral TNFerade™ injections combined with concurrent capecitabine and radiotherapy in the treatment of patients with locally advanced rectal cancer.

METHODS

Patients with T3, T4, or N+ rectal cancer received radiotherapy to a total dose of 50.4-54 Gy in combination with capecitabine 937.5 mg/m(2) p.o. b.i.d. TNFerade™ at a dose of 4 × 10(10) particle units was injected into the rectal tumor on the first day of radiotherapy and weekly for a total of 5 injections. Surgery was performed 5-10 weeks after the completion of chemoradiation.

RESULTS

Nine patients were enrolled in this pilot trial. The stage was cT2 in 2 patients, cT3 in 6 patients, cT4 in 1 patient, N- in 7 patients and N+ in 2 patients. Eight patients completed all treatments. Grade 3 hematologic toxicity was observed in 2 patients. There was no toxicity directly attributable to the injection procedure. A complete pathologic response was observed in 2 of 9 patients.

CONCLUSIONS

This study demonstrates the feasibility of weekly intratumoral TNFerade™ injections during chemoradiotherapy for locally advanced rectal cancer. Pathologic responses with this combination compare favorably to published rates.

Combining radiation therapy with interstitial radiation-inducible TNF-α expression for locoregional cancer treatment

Brachytherapy (BRT) is used in the treatment of human cancers, including the cervix, breast, prostate and head and neck cancers. The primary advantage of BRT lies in the spatial conformation of the radiation deposition. Previously, we have shown that similar techniques (using hollow metallic cylinders) may be used to deliver gene-therapy vectors capable of expressing the radiation-sensitizing cytokine, tumor necrosis factor (TNF)-α, within a restricted volume of tissue. Herein, we report radiation sensitization of cancer cells using a TNF-α expressing vector driven by the radiation-inducible immediate-early gene-1 (IEX-1) promoter (pIEX-TNF-α). TNF-α, determined by ELISA assays using culture medium, increased between 5 and 10 fold, 48 h following exposure to radiation, and radiation sensitization was comparable with that observed in cells in which TNF-α was constitutively expressed under cytomegalo viral (CMV) promoter using the plasmid vector (pCMV-TNF-α). This efficiency of induced TNF-α radiation sensitization was also observed in cervix (SW756) and prostate tumor (PC-3) xenograft models. IEX-1-driven TNF-α expression following external radiation exposure resulted in enhanced regression of tumor xenografts as compared with radiation alone. A feasibility of using radioactive Pd-103 seeds with GeneSeeds was further examined using PC-3 xenograft models. The data showed substantial tumor growth suppression following co-implantation with a metal seed containing Pd-103. Taken together, these results show the enhanced effect on tumor regression by treatment with radiation-inducible TNF-α expression in combination with radiation and support for the IEX-1 promoter as a useful regulator for temporal activation of radiation-sensitizing gene expression.

TNFalpha gene delivery therapy for solid tumors

IMPORTANCE OF THE FIELD

Multimodality therapy, including adjuvant and neoadjuvant chemotherapy and radiotherapy, is now the mainstay of treatment for the majority of non-hematologic cancers. Host toxicity can, however, be significant, which may contribute to local and/or systemic failures. Novel adjunctive treatments that can limit systemic exposure while synergizing with standard therapy hold promise in the fight against an increasing number of cancers.

AREAS COVERED IN THIS REVIEW

We discuss a TNFalpha gene delivery system used to generate high levels of intratumoral TNFalpha, while limiting systemic exposure. The delivery system utilizes a replication-deficient adenoviral vector. When injected intratumorally and activated by external beam radiation, infected cells synthesize and locally secrete large amounts of TNFalpha.

WHAT THE READER WILL GAIN

This review will provide the reader with a thorough understanding of the gene-based TNFalpha delivery system with special emphasis on product characteristics, mechanisms of action, clinical efficacy, safety and tolerability.

TAKE HOME MESSAGE

The TNFalpha gene delivery system holds promise as an adjunctive agent for improved local control and increasing resectability rates for many solid tumors. The completion of several ongoing randomized trials will help to better define the role for TNFalpha gene delivery therapy in the treatment of solid tumors.

SNAI2 as a novel radioprotector of normal tissue by gene transfer using a lentiviral bicistronic SIN vector

Tumor radiotherapy with large-field irradiation results in an increase of p53-dependent apoptosis of the radiosensitive hematopoietic stem cells. Proapoptotic PUMA is a transcriptional target of p53. Thus suppression of PUMA expression by gene therapy with the transcription repressor SNAI2 as transgene might be a potential approach for normal tissue protection during radiotherapy. SNAI2 cDNA was cloned in a lentiviral SIN vector in a bicistronic expression cassette followed by a floxed IRES-EMCV linker and EGFP as selection gene. Wild-type p53 TK6 cells were used as the cellular model system. We could demonstrate the significant radioprotective effect of SNAI2 overexpression in a cytotoxicity assay after irradiation with 0-5 Gy compared with untransduced or control vector (inverse oriented SNAI2 cDNA)-transduced cells. Additionally, TK6-SNAI2 compared to TK6-SNAI2inv cells showed a survival advantage in a clonogenic assay after irradiation with 0-3 Gy. Determination of the proportion of sub-G(1) cells in TK6-SNAI2 cells revealed an approximately 50% reduction in apoptosis compared with both control entities. In this study using a bicistronic lentiviral vector, we were able to provide proof of principle that lentiviral overexpression of SNAI2 might be used for radioprotective gene therapy to widen the therapeutic range in radiotherapy.

Enhanced radiosensitivity of EC109 cells by inhibition of HDAC1 expression

Histone deacetylase (HDAC) activity plays the role of deacetylation of histone and non-histone proteins, which can alter gene expression patterns and cell behavior potentially associated with malignant transformation. Aberrant expression of HDAC1 has been found in various types of cancers, which indicated that it might be a target for cancer therapy. In this study, overexpression of HDAC1 was found in esophageal cancer samples by real-time RT-PCR, compared with adjacent non-cancerous tissues. To further verify the possibility of anticancer treatment by silencing the increased HDAC1 in esophageal carcinoma cells, HDAC1 expression was knockdown using plasmid-based RNA interference (RNAi). Results showed the HDAC1 expression was efficiently inhibited and the acetylation of histone H3 was significantly increased by RNAi in EC109 cells. Increased apoptotic cell death was observed when HDAC1 expression was knockdown, which indicated that cells were more sensitive to radiation. Moreover, the results also showed DNA was more easily broken by radiation in EC109 cells when HDAC1 expression was knockdown, as measured by γH2AX foci and single-cell electrophoresis. Our data suggested that targeting the increased HDAC1 expression might be feasible for esophageal cancer therapy.

Ad.Egr-TNF and local ionizing radiation suppress metastases by interferon-beta-dependent activation of antigen-specific CD8+ T cells

Ad.Egr-TNF is a radioinducible adenovector currently in phase 3 trials for inoperable pancreatic cancer. The combination of Ad.Egr-TNF and ionizing radiation (IR) contributes to local tumor control through the production of tumor necrosis factor-alpha (TNFalpha) in the tumor microenvironment. Moreover, clinical and preclinical studies with Ad.Egr-TNF/IR have suggested that this local approach suppresses the growth of distant metastatic disease; however, the mechanisms responsible for this effect remain unclear. These studies have been performed in wild-type (WT) and TNFR1,2(-/-) mice to assess the role of TNFalpha-induced signaling in the suppression of draining lymph node (DLN) metastases. The results demonstrate that production of TNFalpha in the tumor microenvironment induces expression of interferon (IFNbeta). In turn, IFNbeta stimulates the production of chemokines that recruit CD8(+) T cells to the tumor. The results further demonstrate that activation of tumor antigen-specific CD8(+) CTLs contributes to local antitumor activity and suppression of DLN metastases. These findings support a model in which treatment of tumors with Ad.Egr-TNF and IR is mediated by local and distant immune-mediated antitumor effects that suppress the development of metastases.

Development of a gene therapy virus with a glucocorticoid-inducible MMP1 for the treatment of steroid glaucoma

PURPOSE

To design a glucocorticoid-inducible virus vector overexpressing recombinant matrix metalloproteinase 1 (MMP1) and counteract extracellular matrix deposition in the trabecular meshwork only when steroid is present.

METHODS

Endogenous MMP1 expression was measured in primary human trabecular meshwork cells (HTM) treated with dexamethasone (DEX), triamcinolone acetate, and prednisolone acetate by TaqMan PCR. Wild-type and mutant MMP1 cDNAs were cloned downstream of a glucocorticoid response element (GRE) and P(TAL) promoter. Adenoviruses AdhGRE.MMP1 and AdhGRE.mutMMP1 were generated by homologous recombination. HTM cells and perfused human anterior segments were infected with the viruses, with and without DEX. MMP1 mRNA and protein were analyzed by TaqMan PCR, Western blot analysis, and ELISA. Activity of secreted MMP1 was evaluated by FRET and rat tail collagen type I assays. Immunohistochemistry was performed by double-labeling with anti-human MMP1 and collagen type I antibodies.

RESULTS

Endogenous MMP1 expression was greatly downregulated by the steroids. DEX-treated cells and perfused organ cultures infected with AdhGRE.MMP1 secreted high levels of MMP1. Induction of MMP1 cycled on and off with the addition or removal of DEX. Secreted wild-type MMP1 degraded collagen type I after activation, whereas secreted mutMMP1 did not. Immunohistochemistry showed faint staining of collagen type I in areas of trabecular meshwork with high MMP1 transgene expression.

CONCLUSIONS

The authors have developed a novel glucocorticoid-inducible adenovirus vector that overproduces MMP1 only in the presence of DEX. The availability of this vector sets up the foundation for the development of gene therapy drugs for the potential treatment of ocular hypertension in steroid-responsive patients.