Cytosine Deaminase Uracil Phosphoribosyltransferase Research Articles

Neuroprotective effects of genome-edited human iPS cell-derived neural stem/progenitor cells on traumatic brain injury.

Despite developing neurosurgical procedures, few treatment options have achieved functional recovery from traumatic brain injury (TBI). Neural stem/progenitor cells (NS/PCs) may produce a long-term effect on neurological recovery. Although induced pluripotent stem cells (iPSCs) can overcome ethical and practical issues of human embryonic or fetal-derived tissues in clinical applications, the tumorigenicity of iPSC-derived populations remains an obstacle to their safe use in regenerative medicine. We herein established a novel treatment strategy for TBI using iPSCs expressing the enzyme-prodrug gene yeast cytosine deaminase-uracil phosphoribosyl transferase (yCD-UPRT). NS/PCs derived from human iPSCs displayed stable and high transgene expression of yCD-UPRT following CRISPR/Cas9-mediated genome editing. In vivo bioluminescent imaging and histopathological analysis demonstrated that NS/PCs concentrated around the damaged cortex of the TBI mouse model. During the subacute phase, performances in both beam walking test and accelerating rotarod test were significantly improved in the treatment group transplanted with genome-edited iPSC-derived NS/PCs compared with the control group. The injury area visualized by extravasation of Evans blue was smaller in the treatment group compared with the control group, suggesting the prevention of secondary brain injury. During the chronic phase, cerebral atrophy and ventricle enlargement were significantly less evident in the treatment group. Furthermore, after 5-fluorocytosine (5-FC) administration, 5-fluorouracil converted from 5-FC selectively eliminated undifferentiated NS/PCs while preserving the adjacent neuronal structures. NS/PCs expressing yCD-UPRT can be applied for safe regenerative medicine without the concern for tumorigenesis.

MicroRNA-sensitive oncolytic measles virus for chemovirotherapy of pancreatic cancer

Advanced pancreatic cancer is characterized by few treatment options and poor outcomes. Oncolytic virotherapy and chemotherapy involve complementary pharmacodynamics and could synergize to improve therapeutic efficacy. Likewise, multimodality treatment may cause additional toxicity, and new agents have to be safe. Balancing both aims, we generated an oncolytic measles virus for 5-fluorouracil-based chemovirotherapy of pancreatic cancer with enhanced tumor specificity through microRNA-regulated vector tropism. The resulting vector encodes a bacterial prodrug convertase, cytosine deaminase-uracil phosphoribosyl transferase, and carries synthetic miR-148a target sites in the viral F gene. Combination of the armed and targeted virus with 5-fluorocytosine, a prodrug of 5-fluorouracil, resulted in cytotoxicity toward both infected and bystander pancreatic cancer cells. In pancreatic cancer xenografts, a single intratumoral injection of the virus induced robust in vivo expression of prodrug convertase. Based on intratumoral transgene expression kinetics, we devised a chemovirotherapy regimen to assess treatment efficacy. Concerted multimodality treatment with intratumoral virus and systemic prodrug administration delayed tumor growth and prolonged survival of xenograft-bearing mice. Our results demonstrate that 5-fluorouracil-based chemovirotherapy with microRNA-sensitive measles virus is an effective strategy against pancreatic cancer at a favorable therapeutic index that warrants future clinical translation.

Luciferase-based reporting of suicide gene activity in murine mesenchymal stem cells.

Due to their ease of isolation, gene modification and tumor-homing properties, mesenchymal stem cells (MSCs) are an attractive cellular vehicle for the delivery of toxic suicide genes to a variety of cancers in pre-clinical models. In addition, the incorporation of suicide genes in stem cell-derived cell replacement therapies improves their safety profile by permitting graft destruction in the event of unexpected tumorigeneses or unwanted differentiation. Due to the functional requirement of ATP for the Firefly luciferase gene Luc2 to produce light, luciferase-based reporting of cytotoxicity can be engineered into potential cell therapies. Consequently, we nucleofected mammalian expression plasmids containing both the Luc2 and the yeast fusion cytosine deaminase uracil phosphoribosyltransferase (CDUPRT) genes for expression in murine MSCs to assess luciferase as a reporter of suicide gene cytotoxicity, and MSC as vehicles of suicide gene therapy. In vitro bioluminescence imaging (BLI) showed that following the addition of the non-toxic prodrug fluorocytosine (5-FC), CDUPRT-expressing MSCs displayed enhanced cytotoxicity in comparison to Luc2 reporter MSC controls. This study demonstrates the utility of luciferase as a reporter of CDUPRT-mediated cytotoxicity in murine MSC using BLI.

Prodrug encapsulated albumin nanoparticles as an alternative approach to manifest anti-proliferative effects of suicide gene therapy

Conventional anticancer agents are associated with limited therapeutic efficacy and substantial nonspecific cytotoxicity. Thus, there is an imminent need for an alternative approach that can specifically annihilate the cancer cells with minimal side effects. Among such alternative approaches, CD::UPRT (cytosine deaminase uracil phosphoribosyl transferase) suicide gene therapy has tremendous potential due to its high efficacy. Prodrug 5-Fluorocytosine (5-FC) used in combination with CD::UPRT suicide gene suffers from limited solubility which subsequently leads to decline in therapeutic efficacy. In order to overcome this, 5-FC encapsulated bovine serum albumin nanoparticles (BSA-5-FC NPs) were prepared in this work by desolvation method. Physico-chemical characterizations studies revealed amorphous nature of BSA-5-FC NPs with uniform spherical morphology. Apart from increase in solubility, encapsulated 5-FC followed slow and sustained release profile. Suicide gene expressing stable clone of L-132 cells were adapted for investigating therapeutic potential of BSA-5-FC NPs. These nanoparticles were readily taken up by the cells in a concentration dependent manner and subsequently manifested apoptosis, which was further confirmed by morphological examination and gene expression analysis. These findings clearly illustrate that CD::UPRT suicide gene therapy can be efficiently utilized in combination with this nanosystem for improved suicide gene therapy and tumor eradication.

Combined treatment, based on lysomustine administration with mesenchymal stem cells expressing cytosine deaminase therapy, leads to pronounced murine Lewis lung carcinoma growth inhibition.

The combination of stem cell-based gene therapy with chemotherapy comprises an advantageous strategy that results in a reduction of system toxicity effects and an improvement in the general efficacy of treatment. In the present study, we estimated the efficacy of adipose tissue-derived mesenchymal stem cells (AT-MSCs) expressing cytosine deaminase (CDA) combined with lysomustine chemotherapy in mice bearing late stage Lewis lung carcinoma (LLC). Adipose tissue-derived mesenchymal stem cells were transfected with non-insert plasmid construct transiently expressing fused cytosine deaminase-uracil phosphoribosyltransferase protein (CDA/UPRT) or the same construct fused with Herpes Simplex Virus Type1 tegument protein VP22 (CDA/UPRT/VP22). Systemic administration of 5-fluorocytosine (5FC) and lysomustine was implemented after a single intratumoral injection of transfected AT-MSCs. We demonstrated that direct intratumoral transplantation of AT-MSCs expressing CDA/UPRT or CDA/UPRT/VP22 followed by systemic administration of 5FC resulted in a significant tumor growth inhibition. There was a 56% reduction in tumor volume in mice treated by AT-MSCs-CDA/UPRT + 5FC or with AT-MSCs-CDA/UPRT/VP22 + 5FC compared to control animals grafted with lung carcinoma alone. Transplantation of AT-MSCs-CDA/UPRT + 5FC and AT-MSCs-CDA/UPRT/VP22 + 5FC prolonged the life span of mice bearing LLC by 27% and 31%, respectively. Co-administration of lysomustine and AT-MSCs-CDA/UPRT + 5FC led to tumor growth inhibition (by 86%) and life span extension (by 60%) compared to the control group. Our data indicate that a combination CDA/UPRT-expressing AT-MSCs with lysomustine has a superior antitumor effect in the murine lung carcinoma model compared to monotherapies with transfected AT-MSCs or lysomustine alone, possibly because of a synergistic effect of the combination therapy. Copyright © 2016 John Wiley & Sons, Ltd.

Bioactive Core-Shell Nanofiber Hybrid Scaffold for Efficient Suicide Gene Transfection and Subsequent Time Resolved Delivery of Prodrug for Anticancer Therapy.

Nanofiber scaffold's ability to foster seemingly nonexistent interface with the cells enables them to effectively deliver various bioactive molecules to cells in the vicinity. Among such bioactive molecules, therapeutically active nucleic acid has been the most common candidate. In spite of such magnanimous efforts in this field, it remains a paradox that suicide gene delivery by nanofibers has never been sought for anticancer application. To investigate such a possibility, in the present work, a composite core-shell nanofiberous scaffold has been realized which could efficiently transfect suicide gene into cancer cells and simultaneously deliver prodrug, 5-Fluorocytosine (5-FC) in a controlled and sustained manner. The scaffold's ability to instigate apoptosis by suicide gene therapy in nonsmall lung cancer cells (A549) was ascertained at both phenotypic and genotypic levels. A cascade of events starting from suicide gene polyplex release from nanofibers, transfection, and expression of cytosine deaminase-uracil phosphoribosyltransferase (CD::UPRT) suicide gene by A549; subsequent prodrug release; and its metabolic conversion into toxic intermediates which finally culminates in host cells apoptosis has been monitored in a time-dependent manner. This work opens up new application avenues for nanofiber-based scaffolds which can effectively manage cancer prognosis.

3D multicellular models reflect the efficiency of MSC-directed enzyme/prodrug treatment.

Mesenchymal stromal cells (MSC) exhibit beneficial properties to serve as cellular vehicles for enzyme/prodrug cancer gene therapy approaches. We have previously shown that engineered human adipose tissue-derived MSC in combination with non-toxic prodrug mediated substantial cytotoxic and antitumor effect. The aim of this study was to develop advanced 3D cultivation method to serve for modelling of the therapeutic outcome in vitro. We have used engineered MSC expressing fusion transgene cytosine deaminase::uracilphosphoribosyltransferase (CD-MSC) in combination with prodrug 5-fluorocytosine (5FC). This therapeutic regimen designated CD-MSC/5FC was combined with the human melanoma cells A375 or EGFP-A375 in both standard monolayer culture and 3-dimensional (3D) multicellular nodules. The extent of cytotoxicity was evaluated by standard viability assay MTS, ATP-based luminescence assay, fluorimetric test, measurement of Caspase-3/7 activation and DNA laddering. The data have shown that the extent of cytotoxic bystander effect mediated by CD-MSC/5FC is significantly lower in 3D culture conditions. However, these data better recapitulate the therapeutic efficiency as observed previously in vivo. We suggest here to use the 3D multicellular culture conditions for better prediction of the therapeutic outcome in mouse xenograft models.

Abstract 713: Utilizing a potent and selective nonreplicating adenoviral mutant (Ad5-TV-CU), with gene expression controlled by androgen receptor-dependent activation domains in the TMPRSS2 gene, as a novel prodrug-converting enzyme therapy for prostate cancer

Abstract Prostate cancer (PCa) progression is dependent on transcriptional activation of the androgen receptor (AR) in the majority of cases. Therefore, therapies include anti-androgens, which decrease levels of circulating androgens and inhibit AR activity. However, resistance inevitably develops, resulting in more aggressive, incurable late-stage disease with intact or constitutively active AR signaling. There is currently no cure for castration-resistant metastatic PCa and novel therapies are needed. A major AR-regulated gene is TMPRSS2, which is commonly expressed at higher levels in cancer than normal prostate. In 50% of PCa cases the TMPRSS2 promoter is fused to the oncogenic transcriptional regulator ERG. We generated TMPRSS2 promoter and enhancer constructs to drive the prodrug-converting chimeric enzyme cytosine deaminase uracil phosphoribosyl transferase (CD/UPRT) from an adenoviral vector to investigate the therapeutic efficacy in various PCa models. The selectivity and transcriptional efficiency of various promoter and enhancer regions containing Androgen response elements (ARE's) were investigated after cloning TMPRSS2 constructs driving Luciferase (Luc) expression into the versatile expression vector ‘VISA’ (VP16-GAL4-WPRE integrated systemic amplifier) (Professor Hung, M.D Anderson, TX,USA) to enhance promoter activity. Comparison with the traditional PSA promoter and the chimeric PSA promoter/enhancer in the VISA vector demonstrated the TMPRSS2 construct to be superior by inducing 3.5 fold and 2.3 fold levels of luciferase expression, respectively. When the Luc-gene was replaced with CD/UPRT, specific and dose-dependent cell killing was observed in 22RV1 (AR+) cells when the non-toxic prodrug 5-flourocytosine (5-FC) was administered. No cell death was observed in primary prostate epithelial cells (PrEC), or immortalized prostate cell lines PNT1A or PNT2 (AR-). To increase transfection efficiency of the CD/UPRT gene, the TMPRSS2-VISA-CD/UPRT expression cassette was inserted into a non-replicating adenovirus (Ad5-TV-C/U) replacing the E1-genes. Ad5-TV-C/U was characterized and protein expression of the CD/UPRT gene was detected at high levels post infection in 22RV1, LNCaP, and VCaP cells (AR+). Dose-dependent decreases in EC50-values were observed upon infection with Ad5-TV-C/U in combination with low doses of 5-FC in a number of cell lines, for example 22RV1 cells, where EC50-values decreased from 571ppc ±55 to 174ppc ±30. These results demonstrate that Ad5-TV-C/U is both selective and efficacious in killing AR-positive PCa cells in combination with non-toxic 5-FC. Verification of these findings in preclinical in vivo models is in progress. Citation Format: Emma J. Mercer, Ahmet Imrali, Kevin Sharpe, Gunnel Hallden, Yong-Jie Lu. Utilizing a potent and selective nonreplicating adenoviral mutant (Ad5-TV-CU), with gene expression controlled by androgen receptor-dependent activation domains in the TMPRSS2 gene, as a novel prodrug-converting enzyme therapy for prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 713. doi:10.1158/1538-7445.AM2014-713

Single agent‐ and combination treatment with two targeted suicide gene therapy systems is effective in chemoresistant small cell lung cancer cells

Transcriptional targeted suicide gene (SG) therapy driven by the insulinoma-associated 1 (INSM1) promoter makes it possible to target suicide toxin production and cytotoxicity exclusively to small cell lung cancer (SCLC) cells and tumors. It remains to be determined whether acquired chemoresistance, as observed in the majority of SCLC patients, desensitizes SCLC cells to INSM1 promoter-driven SG therapy. A panel of SCLC cell lines resistant to clinically relevant chemotherapeutics was characterized regarding the expression of proteins involved in response to chemotherapy and regarding INSM1 promoter activity. Sensitivity towards INSM1 promoter-driven SG therapy was tested using different systems: Yeast cytosine deaminase-uracil phosphoribosyl transferase (YCD-YUPRT) in combination with the prodrug 5-fluorocytosine (5-FC) or Escherichia coli nitroreductase (NTR) together with the bromomustard prodrug SN27686. The chemoresistant cell lines displayed heterogeneous expression profiles of molecules involved in multidrug resistance, apoptosis and survival pathways. Despite this, the INSM1 promoter activity was found to be unchanged or increased in SCLC chemoresistant cells and xenografts compared to chemosensitive variants. INSM1 promoter-driven SG therapy with YCD-YUPRT/5-FC or NTR/SN27686, was found to induce high levels of cytotoxicity in both chemosensitive and chemoresistant SCLC cells. Moreover, the combination of INSM1 promoter-driven YCD-YUPRT/5-FC therapy and chemotherapy, as well as the combination of INSM1 promoter-driven YCD-YUPRT/5-FC and NTR/SN27686 therapy, was observed to be superior to single agent therapy in chemoresistant SCLC cells. Collectively, the present study demonstrates that targeted SG therapy is a potent therapeutic approach for chemoresistant SCLC patients, with the highest efficacy achieved when applied as combination SG therapy or in combination with standard chemotherapy.

Chemovirotherapy for head and neck squamous cell carcinoma with EGFR-targeted and CD/UPRT-armed oncolytic measles virus

First-line treatment of recurrent and/or refractory head and neck squamous cell carcinoma (HNSCC) is based on platinum, 5-fluorouracil (5-FU) and the monoclonal antiEGFR antibody cetuximab. However, in most cases this chemoimmunotherapy does not cure the disease, and more than 50% of HNSCC patients are dying because of local recurrence of the tumors. In the majority of cases, HNSCC overexpress the epidermal growth factor receptor (EGFR), and its presence is associated with a poor outcome. In this study, we engineered an EGFR-targeted oncolytic measles virus (MV), armed with the bifunctional enzyme cytosine deaminase/uracil phosphoribosyltransferase (CD/UPRT). CD/UPRT converts 5-fluorocytosine (5-FC) into the chemotherapeutic 5-FU, a mainstay of HNSCC chemotherapy. This virus efficiently replicates in and lyses primary HNSCC cells in vitro. Arming with CD/UPRT mediates efficient prodrug activation with high bystander killing of non-infected tumor cells. In mice bearing primary HNSCC xenografts, intratumoral administration of MV-antiEGFR resulted in statistically significant tumor growth delay and prolongation of survival. Importantly, combination with 5-FC is superior to virus-only treatment leading to significant tumor growth inhibition. Thus, chemovirotherapy with EGFR-targeted and CD/UPRT-armed MV is highly efficacious in preclinical settings with direct translational implications for a planned Phase I clinical trial of MV for locoregional treatment of HNSCC.

Functional chitosan nanocarriers for potential applications in gene therapy

Functional chitosan nanocarriers for suicide gene therapy have been developed. Folic acid conjugated chitosan (FA-chitosan) was used to synthesize zinc sulphide quantum dots (ZnS QDs), which was further converted to chitosan nanocarriers, where the integrated FA acts as targeting, and the embedded QDs as imaging functionalities, respectively. The synthesized nanocarriers were almost spherical with sizes of ~75nm and were nontoxic to the mammalian cell lines. Fluorescence of the QDs was exploited to image the cellular uptake of the nanocarriers. Binding of the plasmid DNA, containing the suicide genes encoding for cytosine deaminase-uracil phosphoribosyltransferase (pCD-UPRT) with the nanocarriers, was investigated by gel retardation assay. DNAse protection assay proved the stability of the nanocarrier–DNA complex. The functional effect of the nanocarriers to sensitize cell death represents a safe non-viral vector system for gene therapy.

Selectivity and Efficiency of Late Transgene Expression by Transcriptionally Targeted Oncolytic Adenoviruses Are Dependent on the Transgene Insertion Strategy

Key challenges facing cancer therapy are the development of tumor-specific drugs and potent multimodal regimens. Oncolytic adenoviruses possess the potential to realize both aims by restricting virus replication to tumors and inserting therapeutic genes into the virus genome, respectively. A major effort in this regard is to express transgenes in a tumor-specific manner without affecting virus replication. Using both luciferase as a sensitive reporter and genetic prodrug activation, we show that promoter control of E1A facilitates highly selective expression of transgenes inserted into the late transcription unit. This, however, required multistep optimization of late transgene expression. Transgene insertion via internal ribosome entry site (IRES), splice acceptor (SA), or viral 2A sequences resulted in replication-dependent expression. Unexpectedly, analyses in appropriate substrates and with matching control viruses revealed that IRES and SA, but not 2A, facilitated indirect transgene targeting via tyrosinase promoter control of E1A. Transgene expression via SA was more selective (up to 1,500-fold) but less effective than via IRES. Notably, we also revealed transgene-dependent interference with splicing. Hence, the prodrug convertase FCU1 (a cytosine deaminase-uracil phosphoribosyltransferase fusion protein) was expressed only after optimizing the sequence surrounding the SA site and mutating a cryptic splice site within the transgene. The resulting tyrosinase promoter-regulated and FCU1-encoding adenovirus combined effective oncolysis with targeted prodrug activation therapy of melanoma. Thus, prodrug activation showed potent bystander killing and increased cytotoxicity of the virus up to 10-fold. We conclude that armed oncolytic viruses can be improved substantially by comparing and optimizing strategies for targeted transgene expression, thereby implementing selective and multimodal cancer therapies.

Yeast dihydroorotate dehydrogenase as a new selectable marker for Plasmodium falciparum transfection

Genetic manipulation of Plasmodium falciparum in culture through transfection has provided numerous insights into the molecular and cell biology of this parasite. The procedure is rather cumbersome, and is limited by the number of drug-resistant markers that can be used for selecting transfected parasites. Here we report a new selectable marker that could allow multiple transfections. We have taken advantage of our finding that a critical function of the mitochondrial electron transport chain (mtETC) in the erythrocytic stages of P. falciparum is the regeneration of ubiquinone as co-substrate of dihydroorotate dehydrogenase (DHODH), and that transgenic P. falciparum expressing ubiquinone-independent DHODH from yeast (yDHODH) are resistant to all mtETC inhibitors. We assessed the possibility of using yDHODH as a positive selectable marker for transfections of P. falciparum, including its use in gene disruption strategies. We constructed a transfection vector designed for gene disruption, termed pUF-1, containing the yDHODH gene as the positive selection marker in combination with a previously described fused yeast cytosine deaminase-uracil phosphoribosyl transferase gene as a negative selection marker. Transfection of the D10 strain followed by selection with atovaquone yielded positively selected parasites containing the plasmid, demonstrating that yDHODH can be used as a selective marker. Atovaquone, however, could not be used for such selection with the Dd2 strain of P. falciparum. On the other hand, we demonstrated that yDHODH transgenic parasites could be selected in both strains by Plasmodium DHODH-specific triazolopyrimidine-based inhibitors. Thus, selection with DHODH inhibitors was superior in that it successfully selected transgenic Dd2 parasites, as well as yielded transgenic parasites after a shorter period of selection. As a proof of concept, we have successfully disrupted the type II vacuolar proton-pumping pyrophosphatase gene (PfVP2) in P. falciparum by double crossover recombination, showing that this gene is not essential for the survival of blood stage parasites.

Incorporation of gene therapy vector in chitosan stabilized Mn 2+-doped ZnS quantum dot

Chitosan stabilized and water soluble (pH ≤ 6.5) ZnS:Mn 2+ quantum dots (QDs) of ca. 3.6 nm having a strong orange fluorescence have been synthesized in an environment friendly method. Binding of plasmid DNA containing the bifunctional cytosine deaminase-uracilphosphoribosyl transferase (pCD-UPRT) gene with therapeutic importance in suicide gene therapy has been investigated and shown to follow the Langmuir reversible adsorption model. The biocompatibility of the composite on HT29 cells was confirmed by the viability assay. The chitosan stabilized ZnS:Mn 2+ QDs synthesized in the present study could be a promising alternative to conventional organic fluorophore-tagged gene delivery systems for real-time monitoring in gene therapy applications.

Targeted Cytosine Deaminase-Uracil Phosphoribosyl Transferase Suicide Gene Therapy Induces Small Cell Lung Cancer–Specific Cytotoxicity and Tumor Growth Delay

Small cell lung cancer (SCLC) is a highly malignant cancer for which there is no curable treatment. Novel therapies are therefore in great demand. In the present study we investigated the therapeutic effect of transcriptionally targeted suicide gene therapy for SCLC based on the yeast cytosine deaminase (YCD) gene alone or fused with the yeast uracil phosphoribosyl transferase (YUPRT) gene followed by administration of 5-fluorocytosine (5-FC) prodrug. The YCD gene or the YCD-YUPRT gene was placed under regulation of the SCLC-specific promoter insulinoma-associated 1 (INSM1). Therapeutic effect was evaluated in vitro in SCLC cell lines and in vivo in SCLC xenografted nude mice using the nonviral nanoparticle DOTAP/cholesterol for transgene delivery. INSM1-YCD/5-FC and INSM1-YCD-YUPRT/5-FC therapy induced high cytotoxicity in a range of SCLC cell lines. The highest therapeutic effect was obtained from the YCD-YUPRT fusion gene strategy. No cytotoxicity was induced after treatment of cell lines of other origin than SCLC. In addition the INSM1-YCD-YUPRT/5-FC therapy was superior to an established suicide gene system consisting of the herpes simplex virus thymidine kinase (HSVTK) gene and the prodrug ganciclovir. The superior effect was in part due to massive bystander cytotoxicity of YCD-YUPRT-produced toxins. Finally, INSM1-YCD-YUPRT/5-FC therapy induced significant tumor growth delay in SCLC xenografts compared with control-treated xenografts. The current study is the first to test cytosine deaminase-based suicide gene therapy for SCLC and the first to show an antitumor effect from the delivery of suicide gene therapeutics for SCLC in vivo.

Abstract C185: Head and neck squamous carcinoma cells are susceptible to the attenuated vesicular stomatitis virus expressing suicide genes

Abstract Background: The predominant loco-regional progression of Head and Neck Squamous Cell Carcinoma (HNSCC) makes it suitable for testing oncolytic viruses. Recent work from several laboratories including ours has focused on developing vesicular stomatitis virus (VSV) as a replication-competent anticancer viral vector. Attenuated strains, such as M protein mutant VSV (M51R) are more likely to be promoted in clinical research. The major shortcoming of viral therapy is related to the large proportion of tumor cells remaining uninfected. We are addressing this limitation in two ways: the expression of the cytosine deaminase-uracil phosphoribosyltransferase (C:U) suicide gene by the rVSV vector, expected to produce a strong bystander effect and the exploitation of the radiosensitizing potential of the 5-fluorouracil (5-FU) chemo-drug produced intratumorally, as well as of the VSV virus itself. Methods: We determined the susceptibility to oncolytic VSV in a collection of HNSCC cell lines and in patient HN primary tumor cells by measuring: 1) the level of GFP expression after infection with rVSV-GFP and M51R-GFP; 2) the viral production by plaque assay and 3) cell death by Trypan blue exclusion. The extent of defectiveness in interferon pathways was tested by employing pre-treatment with IFN and INF-blocking antibodies before the infection with the oncolytic VSV. We have generated the rVSV-C:U and M51R-C:U viruses and we tested our collection of HNSCC cell models to infection with these viruses in the presence and absence of 5-fluorocytosine. SQ20B cell line is a model of radiation resistant HNSCC. Regular SQ20B and SQ20B infected with low-dose M51R-VSV were evaluated by clonogenic assay. Results: 1) All HNSCC cell models tested are susceptible to the infection with the rVSV but many present a degree of resistance to the attenuated M51R-VSV. 2) Human Primary HNSCC cells are more resistant than the HNSCC cell lines to the M51R-VSV; 3) The activation of IFN pathways is contributing to the resistance to M51R-VSV. 4) Addition of the suicide gene C:U to the attenuated VSV model significantly increased the oncolytic effect in vitro; 5) HNSCC cells infected with M51R-VSV become more radiation sensitive. Conclusions: The decreased oncolytic effect of the attenuated M51R-VSV can be overcome by the expression of suicide genes such as the yeast C:U fusion model. The demonstrated radiosensiting potential of the M51R-VSV virus as well as the known radiosensitizing effect of the generated chemotherapeutic 5-FU can be further exploited against the loco-regional HNSCC tumors. Finally, we have important new information, both from cell lines and patient tissues, for proof-of-principle that cancers can down-regulate antiviral responses. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C185.

Susceptibility of head and neck cancer to an attenuated model of the oncolytic vesicular stomatitis virus expressing suicide genes

e14604 Background: The predominant loco-regional progression of head and neck squamous cell carcinoma (HNSCC) makes it suitable for testing oncolytic viruses. Recent work from several laboratories including ours has focused on developing vesicular stomatitis virus (VSV) as a replication-competent anticancer viral vector. Attenuated strains, such as M protein mutant VSV (M51R) are more likely to be promoted in clinical research. The major shortcoming of viral therapy is related to the large proportion of tumor cells remaining uninfected. We are addressing this limitation in two ways: the expression of the cytosine deaminase-uracil phosphoribosyltransferase (C:U) suicide gene by the rVSV vector, expected to produce a strong bystander effect and the exploitation of the radiosensitizing potential of the 5-FU chemo-drug produced intratumorally, as well as of the VSV virus itself. Methods: We determined the extent of defectiveness in interferon pathways and susceptibility to oncolytic VSV in a collection of HNSCC cell lines and in patient HN primary tumor cells. We employed gene array to screen for differences in gene expression in sensitive and resistant models. We have generated the rVSV-C:U and M51R-C:U viruses and we tested our collection of HNSCC cell models to infection with these viruses in the presence and absence of 5-FC. In vivo experiments were performed on a localized and on a metastatic SQ-20B model of HNSCC in nude mice. Results: 1) the primary patient HNC cells are more resistant than the HNC cell lines to the M51R-VSV; 2) the activation of IFN pathways and /or alterations of AKT pathway is contributing to resistance to VSVs. 3) Addition of the suicide gene to the attenuated VSV provided significantly more oncolytic effect in vitro and in vivo. The efficacy and the radiosensitizing potential of M51R- C:U on a nude mice model of HNSCC (SQ-20B) will be presented. Conclusions: M51R-VSV has increased efficiency and radiosensitizing effect on HNSCC models. We can define an optimal approach to testing VSV vectors for treatment of HNSCC, with a clinical trial in HNSCC patients as our next goal. Finally, we have important new information, both from cell lines and patient tissues, for proof-of-principle that cancers can down-regulate antiviral responses. No significant financial relationships to disclose.

Cytosine Deaminase-Uracil Phosphoribosyltransferase and Interleukin (IL)-12 and IL-18: A Multimodal Anticancer Interface Marked by Specific Modulation in Serum Cytokines

To test the effects of a new combination, cytosine deaminase (CD) + uracil phosphoribosyltransferase (UPRT)-mediated gene-directed enzyme prodrug therapy (GDEPT) with interleukin (IL)-12 and IL-18, on (a) growth of murine prostate and remote tumor deposits, (b) mouse survival, and (c) T helper (Th) 1/Th2 serum cytokine balance with a special focus to assess correlation with tumor burden/survival. Efficacy of intraprostatic administration of adenovirally delivered murine IL-12 and IL-18 against orthotopic RM1 tumors and lung pseudometastases was assessed in C57BL/6 mice. At necropsy, tumor growth, lung colony counts, effects on immune cell infiltration, vasculature, apoptosis, and proliferation were estimated. Next, CDUPRT-GDEPT + cytokines were tested at suboptimal doses in mice with RM1CDUPRT prostate tumors/RM1 lung deposits and analyzed as above. Effects on mouse survival were also assessed. Host immune responses to different treatments were assessed by monitoring 11 serum cytokines using Luminex technology. Our data show that IL-12 and IL-18, when combined with CDUPRT-GDEPT, caused significant reduction in local RM1 tumors and lung colonies with enhanced long-term survival versus individual treatments. A dramatic enhancement of tumor infiltration by a wider repertoire of immune cells and disruption of vasculature implied the combination to be more immunostimulatory and antiangiogenic. Remarkably, lowering of serum IL-4 and monocyte chemoattractant protein-1 (MCP-1) was consistently associated with lower tumor burden (local and systemic), and this, rather than an increase in Th1 cytokines, better predicted treatment efficacy. In addition, mouse survival correlated with substantially higher cytokine (Th1/Th2) levels after treatment. Locoregional application of CDUPRT-GDEPT and IL-12/IL-18 was effective against local and systemic prostate cancer and improved survival. Monitoring serum levels of IL-4 and MCP-1 may accurately reflect tumor burden and, hence, host response to therapy.

Understanding apoptotic signaling pathways in cytosine deaminase-uracil phosphoribosyl transferase-mediated suicide gene therapy in vitro

Cytosine deaminase-uracil phosphoribosyl transferase (CD-UPRT) fusion gene is known to exhibit therapeutic effect by inducing apoptosis in vitro. However, bystander effects of 5-flurocytosine (5-FC)/CD-UPRT and the molecular mechanism for apoptosis are yet to be established. In the present study, we have generated BHK21 cell line expressing both CD-UPRT and green fluorescent protein (GFP) from two separate transcripts, where GFP was used as a noninvasive probe to monitor the therapeutic effect of CD-UPRT. Enzyme activity of CD-UPRT in the stable cell line was measured by the reverse phase high-performance liquid chromatography analysis. Inhibition of cell growth and strong bystander effects of 5-FC/CD-UPRT were established, whereas characteristic surface morphology of apoptotic cell death was identified by AFM analysis. Involvement of various apoptotic signaling genes using semi-quantitative RT-PCR has been explored to substantiate the potential application of 5-FC/CD-UPRT suicide gene in therapy.

Implication of functional activity for determining therapeutic efficacy of suicide genes in vitro

Gene-Directed Enzyme Prodrug Therapy (GDEPT), commonly known as suicide gene therapy, provides a selective approach to eradicate tumor cells that is currently considered as an alternate approach to conventional therapy for cancers due to its high efficacy. Herein, we have demonstrated functional activity of the cytosine deaminase (CD) and the hybrid cytosine deaminase-uracil phosphoribosyltransferase (CD-UPRT) suicide genes in transfected cell lines. We have monitored retention profiles of various metabolites that were formed during enzymatic conversion of the prodrug 5-flurocytosine (5-FC) using reverse phase HPLC method. Therapeutic effect of suicide genes was established by cell viability and toxicity assay, whereas apoptotic induction was confirmed by DNA fragmentation ELISA. Our results demonstrated that 5-FC/CD-UPRT-mediated apoptotic cell death was more than 5-FC/CD, which could be further potentiated with anticancer compound curcumin. Such results corroborated 5-FC/CD-UPRT in combination with curcumin as a better chemosensitization method.