Combination of cytosine deaminase suicide gene expression with DR5 antibody treatment increases cancer cell cytotoxicity

Flura-seq identifies organ-specific metabolic adaptations during early metastatic colonization

Metastasis-initiating cells dynamically adapt to the distinct microenvironments of different organs, but these early adaptations are poorly understood due to the limited sensitivity of in situ transcriptomics. We developed fluorouracil-labeled RNA sequencing (Flura-seq) for in situ analysis with high sensitivity. Flura-seq utilizes cytosine deaminase (CD) to convert fluorocytosine to fluorouracil, metabolically labeling nascent RNA in rare cell populations in situ for purification and sequencing. Flura-seq revealed hundreds of unique, dynamic organ-specific gene signatures depending on the microenvironment in mouse xenograft breast cancer micrometastases. Specifically, the mitochondrial electron transport Complex I, oxidative stress and counteracting antioxidant programs were induced in pulmonary micrometastases, compared to mammary tumors or brain micrometastases. We confirmed lung metastasis-specific increase in oxidative stress and upregulation of antioxidants in clinical samples, thus validating Flura-seq's utility in identifying clinically actionable microenvironmental adaptations in early metastasis. The sensitivity, robustness and economy of Flura-seq are broadly applicable beyond cancer research.

Extracellular Vesicles as Carriers of Suicide mRNA and/or Protein in Cancer Therapy

Gene therapy involves the introduction of genes (termed transgenes) into cells to compensate for a deficiency or to make a beneficial protein. Gene therapy can used as a form of cancer treatment. A particularly attractive paradigm in this regard involves the selective introduction of transgenes into cancer cells that converts inactive prodrugs into active chemotherapeutic agents, thereby triggering the death of cancer cells. Since prodrugs are inactive, they tend not to cause significant side-effects and are well-tolerated by patients relative to conventional chemotherapy. Several viral and nonviral vectors have been used as delivery tools for suicide gene therapy. Extracellular vesicles (EVs) are now recognized as a promising class of nonviral delivery vectors. Here, we describe a method in which a suicide fusion gene construct is loaded into EVs derived from a non-tumorigenic cell line. Delivery of these modified EVs to glioblastoma cell lines and spheroids decreases glioblastoma cell viability, induces apoptotic cell death, and inhibits tumor growth in vivo.

An intracellular protein delivery platform based on glutathione-responsive protein nanocapsules

We reported an efficient strategy for the intracellular delivery of proteins based on assembling proteins with a self-crosslinkable polymer. The disulfide-crosslinking structure enhances the stability of the protein–polymer assembly, and also allows effective dissociation of the assembly in response to glutathione.

Selective and augmented β-glucuronidase expression combined with DOX-GA3 application elicits the potent suppression of prostate cancer

The present study was carried out to evaluate the specific and amplified β-glucuronidase (βG) expression in prostate cancer cells by using a prostate‑specific antigen (PSA) promoter-controlled bicistronic adenovirus and to evaluate the specific killing of prostate cancer cells after the application of the prodrug DOX‑GA3. Bicistronic adenoviral expression vectors were constructed, and the effectiveness of specific and amplified expression was evaluated using luciferase and EGFP as reporter genes. βG expression was detected in LNCaP cells after they were infected with the βG‑expressing PSA promoter-controlled bicistronic adenovirus. MTT assays were conducted to evaluate the cytoxicity on the infected cells after the application of the prodrug DOX‑GA3. Tumor growth inhibition was also evaluated in nude mice after treatment with the βG‑expressing adenovirus and DOX‑GA3. Selective and amplified expression was observed in the PSA-producing LNCaP cells, but not in the PSA‑non‑producing DU145 cells. Potent cytotoxity and a strong bystander effect were observed in the LNCaP cells after infection with the βG‑expressing adenovirus and the application of DOX‑GA3. Intravenous injection of a GAL4 regulated bicistronic adenovirus vector constructed to express βG under the control of the PSA promoter (Ad/PSAP‑GV16‑βG) and the application of DOX‑GA3 strongly inhibited tumor growth and prolonged the survival time of tumor‑bearing nude mice. Selective and amplified βG expression together with the prodrug DOX‑GA3 had an increased antitumor effect, showing great potential for prostate cancer therapy.

Engineered adenoviruses combine enhanced oncolysis with improved virus production by mesenchymal stromal carrier cells

Oncolytic viruses have demonstrated in pre-clinical and clinical studies safety and a unique pleiotropic activity profile of tumor destruction. Yet, their delivery suffers from virus inactivation by blood components and sequestration to healthy tissues. Therefore, mesenchymal stromal cells (MSCs) have been applied as carrier cells for shielded virus delivery to tumors after ex vivo infection with oncolytic viruses. However, infection and particle production by MSCs have remained unsatisfying. Here, we report engineered oncolytic adenoviruses (OAds) for improved virus production and delivery by MSCs. OAds are uniquely amenable to molecular engineering, which has facilitated improved tumor cell destruction. But for MSC-mediated regimens, OAd engineering needs to achieve efficient infection and replication in both MSCs and tumor cells. We show that an Ad5/3 chimeric OAd capsid, containing the adenovirus serotype 3 cell-binding domain, strongly increases the entry into human bone marrow-derived MSCs and into established and primary pancreatic cancer cells. Further, we reveal that OAd with engineered post-entry functions-by deletion of the anti-apoptotic viral gene E1B19K or expression of the death ligand TRAIL--markedly increased virus titers released from MSCs, while MSC migration was not hampered. Finally, these virus modifications, or viral expression of FCU1 for local 5-FC prodrug activation, improved tumor cell killing implementing complementary cytotoxicity profiles in a panel of pancreatic cancer cell cultures. Together, our study establishes post-entry modification of OAd replication for improving virus delivery by carrier cells and suggests a panel of optimized OAds for future clinical development in personalized treatment of pancreatic cancer.

Gene therapy in pancreatic cancer

Pancreatic cancer (PC) is a highly lethal disease and notoriously difficult to treat. Only a small proportion of PC patients are eligible for surgical resection, whilst conventional chemoradiotherapy only has a modest effect with substantial toxicity. Gene therapy has become a new widely investigated therapeutic approach for PC. This article reviews the basic rationale, gene delivery methods, therapeutic targets and developments of laboratory research and clinical trials in gene therapy of PC by searching the literature published in English using the PubMed database and analyzing clinical trials registered on the Gene Therapy Clinical Trials Worldwide website (http://www. wiley.co.uk/genmed/ clinical). Viral vectors are main gene delivery tools in gene therapy of cancer, and especially, oncolytic virus shows brighter prospect due to its tumor-targeting property. Efficient therapeutic targets for gene therapy include tumor suppressor gene p53, mutant oncogene K-ras, anti-angiogenesis gene VEGFR, suicide gene HSK-TK, cytosine deaminase and cytochrome p450, multiple cytokine genes and so on. Combining different targets or combination strategies with traditional chemoradiotherapy may be a more effective approach to improve the efficacy of cancer gene therapy. Cancer gene therapy is not yet applied in clinical practice, but basic and clinical studies have demonstrated its safety and clinical benefits. Gene therapy will be a new and promising field for the treatment of PC.

Simultaneous RGB emitting Au nanoclusters in chitosan nanoparticles for anticancer gene theranostics

Advanced theranostic materials hold promise for targeted delivery of drugs, with the ability to follow the transport as well as its consequences. This should, ideally, be possible with minimum invasive surgery and having no or minimum cytotoxicity of the materials. It requires development of newer materials whose physical properties would allow for easy probe, which could carry the therapeutic molecules, which will be stable under physiological conditions, and at the same time would be able to permeate barriers to the target. We report the development of a composite consisting of highly fluorescent Au nanoclusters and the biopolymer chitosan, which could easily be converted into nanoparticles and would form a stable polyplex with suicide gene for induction of apoptosis in cervical cancer cells. The simultaneous red, green, and blue fluorescence from the nanoclusters provided convenient optical imaging and flow cytometry probes, without having to use additional dyes. Moreover, the colloidal nanocluster-polymer composite could be converted into solid film and be stored with the retention of optical properties. The pH tunable optical properties in the medium were also intact in the films that quickly dissolved in water with retention of properties.

A novel intracellular protein delivery platform based on single-protein nanocapsules

An average cell contains thousands of proteins that participate in normal cellular functions, and most diseases are somehow related to the malfunctioning of one or more of these proteins. Protein therapy, which delivers proteins into the cell to replace the dysfunctional protein, is considered the most direct and safe approach for treating disease. However, the effectiveness of this method has been limited by its low delivery efficiency and poor stability against proteases in the cell, which digest the protein. Here, we show a novel delivery platform based on nanocapsules consisting of a protein core and a thin permeable polymeric shell that can be engineered to either degrade or remain stable at different pHs. Non-degradable capsules show long-term stability, whereas the degradable ones break down their shells, enabling the core protein to be active once inside the cells. Multiple proteins can be delivered to cells with high efficiency while maintaining low toxicity, suggesting potential applications in imaging, therapy and cosmetics fields.

The use of folate-PEG-grafted-hybranched-PEI nonviral vector for the inhibition of glioma growth in the rat

Combined treatment using nonviral agent-mediated enzyme/prodrug therapy and immunotherapy had been proposed as a powerful alternative method of cancer therapy. The present study was aimed to evaluate the cytotoxicity in vitro and the therapeutic efficacy in vivo when the cytosine deaminase/5-fluorocytosine (CD/5-FC) and TNF-related apoptosis-inducing ligand (TRAIL) genes were jointly used against rat C6 glioma cells. The potency of the FA-PEG-PEI used as a nonviral vector was tested in the FR-expressed C6 glioma cells and Wistar rats. The C6 glioma cells and animal model were treated by the combined application of FA-PEG-PEI/pCD/5-FC and FA-PEG-PEI/pTRAIL. The antitumor effect was evaluated by survival assays and tumor volume. This study revealed a significant increase of cytotoxicity in vitro following the combined application of FA-PEG-PEI/pCD/5-FC and FA-PEG-PEI/pTRAIL treatments in C6 glioma cells. Animal studies showed a significant growth inhibition of the C6 glioma xenografts using the combined treatment. These results demonstrated that the combined treatment generated additive cytotoxic effect in C6 glioma cells in both in vitro and in vivo conditions, and indicated that such treatment method using both enzyme/prodrug therapy and TRAIL immunotherapy might be a promising therapeutic strategy in treating glioma.

Molecular chemotherapy of pancreatic cancer using novel mutant bacterial cytosine deaminase gene

The combination of molecular chemotherapy with radiation therapy has the potential to become a powerful approach for treatment of pancreatic cancer. We have developed an adenoviral vector (AdbCD-D314A) encoding a mutant bacterial cytosine deaminase (bCD) gene, which converts the prodrug 5-fluorocytosine (5-FC) into the active drug 5-fluorouracil. The aim of this study was to investigate AdbCD-D314A/5-FC-mediated cytotoxicity in vitro and therapeutic efficacy in vivo alone and in combination with radiation against human pancreatic cancer cells and xenografts. AdbCD-D314A/5-FC-mediated cytotoxicity alone and in combination with radiation was analyzed using crystal violet inclusion and clonogenic survival assays. CD enzyme activity was determined by measuring conversion of [3H]5-FC to [3H]5-fluorouracil after adenoviral infection of pancreatic cancer cells in vitro and pancreatic tumor xenografts by TLC. S.c. pancreatic tumor xenografts were used to evaluate the therapeutic efficacy of AdbCD-D314A/5-FC molecular chemotherapy in combination with radiation therapy. AdbCD-D314A infection resulted in increased 5-FC-mediated pancreatic cancer cell killing that correlated with significantly enhanced CD enzyme activity compared with AdbCDwt encoding wild-type of bCD. Animal studies showed significant inhibition of growth of human pancreatic tumors treated with AdbCD-D314A/5-FC in comparison with AdbCDwt/5-FC. Also, a significantly greater inhibition of growth of Panc2.03 and MIA PaCA-2 tumor xenografts was produced by the combination of AdbCD-D314A/5-FC with radiation compared with either agent alone. The results indicate that the combination of AdbCD-D314A/5-FC molecular chemotherapy with radiation therapy significantly enhanced cytotoxicity of pancreatic cancer cells in vitro and increased therapeutic efficacy against human pancreatic tumor xenografts.

Mutation of Escherichia coli cytosine deaminase significantly enhances molecular chemotherapy of human glioma

Combined treatment using adenoviral (Ad)-directed enzyme/prodrug therapy and radiation therapy has the potential to become a powerful method of cancer therapy. We have developed an Ad vector encoding a mutant bacterial cytosine deaminase (bCD) gene (AdbCD-D314A), which has a higher affinity for cytosine than wild-type bCD (bCDwt). The purpose of this study was to evaluate cytotoxicity in vitro and therapeutic efficacy in vivo of the combination of AdbCD-D314A with the prodrug 5-fluorocytosine (5-FC) and ionizing radiation against human glioma. The present study demonstrates that AdbCD-D314A infection resulted in increased 5-FC-mediated cell killing, compared with AdbCDwt. Furthermore, a significant increase in cytotoxicity following AdbCD-D314A and radiation treatment of glioma cells in vitro was demonstrated as compared to AdbCDwt. Animal studies showed significant inhibition of subcutaneous or intracranial tumor growth of D54MG glioma xenografts by the combination of AdbCD-D314A/5-FC with ionizing radiation as compared with either agent alone, and with AdbCDwt/5-FC plus radiation. The results suggest that the combination of AdbCD-D314A/5-FC with radiation produces markedly increased cytotoxic effects in cancer cells in vitro and in vivo. These data indicate that combined treatment with this novel mutant enzyme/prodrug therapy and radiotherapy provides a promising approach for cancer therapy.

Cytosine deaminase/5-fluorocytosine gene therapy and Apo2L/TRAIL cooperate to kill TRAIL-resistant tumor cells

The death ligand Apo2L/TRAIL (Apo2 ligand/tumor necrosis factor-related apoptosis-inducing ligand) eradicates many tumor types while sparing most normal tissues. However, some tumors are resistant to TRAIL. We therefore determined if TRAIL cooperates with cytosine deaminase/5-fluorocytosine (CD/5-FC) gene therapy and investigated the mechanisms involved. Transfection of human LAN-5 neuroblastoma cells with CD rendered the cells (LAN-5-CD) sensitive to 5-FC-induced, caspase-dependent apoptosis. Mediated by caspase-3, CD/5-FC and TRAIL cooperated to induce apoptosis in these TRAIL-resistant cells and to cleave X-linked inhibitor of apoptosis protein (XIAP). In established LAN-5-CD tumors growing subcutaneously in mice, intratumorally applied TRAIL did not decrease tumor growth and systemically administered 5-FC only attenuated tumor growth. In contrast, 5-FC together with TRAIL dramatically decreased tumor growth and eradicated a tumor. Assuming sufficient gene transfer of CD in situ, CD/5-FC with TRAIL may be useful for the therapy of tumors resistant to TRAIL.

Theoretical basis, experimental design, and computerized simulation of synergism and antagonism in drug combination studies

The median-effect equation derived from the mass-action law principle at equilibrium-steady state via mathematical induction and deduction for different reaction sequences and mechanisms and different types of inhibition has been shown to be the unified theory for the Michaelis-Menten equation, Hill equation, Henderson-Hasselbalch equation, and Scatchard equation. It is shown that dose and effect are interchangeable via defined parameters. This general equation for the single drug effect has been extended to the multiple drug effect equation for n drugs. These equations provide the theoretical basis for the combination index (CI)-isobologram equation that allows quantitative determination of drug interactions, where CI < 1, = 1, and > 1 indicate synergism, additive effect, and antagonism, respectively. Based on these algorithms, computer software has been developed to allow automated simulation of synergism and antagonism at all dose or effect levels. It displays the dose-effect curve, median-effect plot, combination index plot, isobologram, dose-reduction index plot, and polygonogram for in vitro or in vivo studies. This theoretical development, experimental design, and computerized data analysis have facilitated dose-effect analysis for single drug evaluation or carcinogen and radiation risk assessment, as well as for drug or other entity combinations in a vast field of disciplines of biomedical sciences. In this review, selected examples of applications are given, and step-by-step examples of experimental designs and real data analysis are also illustrated. The merging of the mass-action law principle with mathematical induction-deduction has been proven to be a unique and effective scientific method for general theory development. The median-effect principle and its mass-action law based computer software are gaining increased applications in biomedical sciences, from how to effectively evaluate a single compound or entity to how to beneficially use multiple drugs or modalities in combination therapies.

Treatment with gemcitabine and TRA-8 anti-death receptor-5 mAb reduces pancreatic adenocarcinoma cell viability in vitro and growth in vivo

Gemcitabine is a first line agent for pancreatic cancer, but yields minimal survival benefit. This study evaluated in vitro and in vivo effects of a monoclonal antibody (TRA-8) to human death receptor 5, combined with gemcitabine, using two human pancreatic cancer cell lines, S2VP10 and MIA PaCa-2. A subcutaneous model of pancreatic cancer was employed to test in vivo efficacy. S2VP10 and MIA PaCa-2 cells were treated with varying doses of gemcitabine and TRA-8. Cell viability and apoptosis were determined with an adenosine triphosphate assay and annexin V staining, respectively. Mitochondrial membrane destabilization was evaluated with fluorescence-activated cell sorting analysis of JC-1 stained cells. Caspase activation was evaluated by Western blot analysis. MIA PaCa-2 subcutaneous xenografts in athymic nude mice were evaluated for response to treatment with 200 mug of TRA-8 (intraperitoneal on days 9, 13, 16, 20, 23, and 27 postimplant) and 120 mg/kg gemcitabine (I.P. on days 10, 17, and 24). Tumor growth was measured with calipers. MIA PaCa-2 and S2VP10 cells receiving combination treatment with TRA-8 and gemcitabine demonstrated enhanced cytotoxicity, annexin V staining, and mitochondrial destabilization compared to either agent alone. Combination treatment produced enhanced caspase-3 and -8 activation in both cell lines compared with either agent alone. In vivo studies demonstrated mean subcutaneous tumor surface area (produce of two largest diameters) doubling times of 38 days untreated, 32 days gemcitabine, 49 days TRA-8, and 64 days combination treatment. TRA-8 is an apoptosis-inducing agonistic monoclonal antibody that produced synergistic cytotoxicity in combination with gemcitabine in vitro through enhanced caspase activation. These findings, with substantial inhibition of tumor growth in a mouse pancreatic cancer xenograft model receiving combination therapy, are encouraging for anti-death receptor therapy in the treatment of pancreatic cancer.

Effective antitumoral immune responses are not induced by cytosine deaminase suicide gene transfer in a syngeneic rat pancreatic carcinoma model

BACKGROUND

Experimental gene transfer can make tumors more immunogenic, leading to local regression and inducing immunological memory sufficient to permit resistance to a tumor rechallenge. However, this rarely had any significant impact on large established tumors.

METHODS

To analyze potential immunological effects, we used weakly immunogenic pancreatic carcinomas in syngeneic, immunocompetent Lewis rats and performed in situ adenoviral mediated cytosine deaminase (CD) gene transfer followed by administration of the prodrug, 5-fluorocytosine (5FC). In order to reflect the clinical situation, such treated tumors were surgically resected and animals were rechallenged with parental DSL6A pancreatic tumor cells. Tumor growth and cytotoxic activity of immune cells were determined.

RESULTS

CD/5FC treatment of the DSL6A cells revealed significant induction of apoptosis in vitro and slowed down tumor progression in syngeneic hosts. Furthermore, we observed neither significant change in tumor growth nor protective immunity in the rechallenged animals. Analysis of T lymphocytes showed no specific cytotoxic activity against DSL6A cells. There was only a trend towards a minor NK cell activation.

CONCLUSIONS

Albeit the present study failed to induce protective antitumor immunity, the initial finding of reduced tumor growth argues for the development of multimodal therapeutic options to overcome negative impacts of advanced malignant disease or chemotherapy-related anergy and immunosuppression.

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