Noriyuki Kasahara

Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, United States

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Publications (120)555.85 Total impact

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    ABSTRACT: Autologous human induced pluripotent stem cells (hiPSCs) should allow cellular therapeutics without an associated immune response. This concept has been controversial since the original report that syngeneic mouse iPSCs elicited an immune response after transplantation. However, an investigative analysis of any potential acute immune responses in hiPSCs and their derivatives has yet to be conducted. In the present study, we used correlative gene expression analysis of two putative mouse "immunogenicity" genes, ZG16 and HORMAD1, to assay their human homologous expression levels in human pluripotent stem cells and their derivatives. We found that ZG16 expression is heterogeneous across multiple human embryonic stem cell and hiPSC-derived cell types. Additionally, ectopic expression of ZG16 in antigen-presenting cells is insufficient to trigger a detectable response in a peripheral blood mononuclear cell coculture assay. Neither of the previous immunogenicity-associated genes in the mouse currently appears to be relevant in a human context. ©AlphaMed Press.
    STEM CELLS TRANSLATIONAL MEDICINE 01/2015; DOI:10.5966/sctm.2014-0117 · 3.60 Impact Factor
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    ABSTRACT: We report a novel adaptation of the Radial Monolayer Cell Migration assay, first reported to measure the radial migration of adherent tumor cells on extracellular matrix proteins, for measuring the motility of fluorescently-labeled, non-adherent human or murine effector immune cells. This technique employs a stainless steel manifold and 10-well Teflon slide to focally deposit non-adherent T cells into wells prepared with either confluent tumor cell monolayers or extracellular matrix proteins. Light and/or multi-channel fluorescence microscopy is used to track the movement and behavior of the effector cells over time. Fluorescent dyes and/or viral vectors that code for fluorescent transgenes are used to differentially label the cell types for imaging. This method is distinct from similar-type in vitro assays that track horizontal or vertical migration/invasion utilizing slide chambers, agar or transwell plates. The assay allows detailed imaging data to be collected with different cell types distinguished by specific fluorescent markers; even specific subpopulations of cells (i.e., transduced/nontransduced) can be monitored. Surface intensity fluorescence plots are generated using specific fluorescence channels that correspond to the migrating cell type. This allows for better visualization of the non-adherent immune cell mobility at specific times. It is possible to gather evidence of other effector cell functions, such as cytotoxicity or transfer of viral vectors from effector to target cells, as well. Thus, the method allows researchers to microscopically document cell-to-cell interactions of differentially-labeled, non-adherent with adherent cells of various types. Such information may be especially relevant in the assessment of biologically-manipulated or activated immune cell types, where visual proof of functionality is desired with tumor target cells before their use for cancer therapy.
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    ABSTRACT: Toca 511 (vocimagene amiretrorepvec), a nonlytic, amphotropic retroviral replicating vector (RRV), encodes and delivers a functionally optimized yeast cytosine deaminase (CD) gene to tumors. In orthotopic glioma models treated with Toca 511 and 5-fluorocytosine (5-FC) the CD enzyme within infected cells converts 5-FC to 5-fluorouracil (5-FU), resulting in tumor killing. Toca 511, delivered locally either by intratumoral injection or by injection into the resection bed, in combination with subsequent oral extended-release 5-FC (Toca FC), is under clinical investigation in patients with recurrent high-grade glioma (HGG). If feasible, intravenous administration of vectors is less invasive, can easily be repeated if desired, and may be applicable to other tumor types. Here, we present preclinical data that support the development of an intravenous administration protocol. First we show that intravenous administration of Toca 511 in a preclinical model did not lead to widespread or uncontrolled replication of the RVV. No, or low, viral DNA was found in the blood and most of the tissues examined 180 days after Toca 511 administration. We also show that RRV administered intravenously leads to efficient infection and spread of the vector carrying the green fluorescent protein (GFP)-encoding gene (Toca GFP) through tumors in both immune-competent and immune-compromised animal models. However, initial vector localization within the tumor appeared to depend on the mode of administration. Long-term survival was observed in immune-competent mice when Toca 511 was administered intravenously or intracranially in combination with 5-FC treatment, and this combination was well tolerated in the preclinical models. Enhanced survival could also be achieved in animals with preexisting immune response to vector, supporting the potential for repeated administration. On the basis of these and other supporting data, a clinical trial investigating intravenous administration of Toca 511 in patients with recurrent HGG is currently open and enrolling.
    Human Gene Therapy 11/2014; DOI:10.1089/hum.2014.100 · 3.62 Impact Factor
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    ABSTRACT: Cellular immunity is pivotal in HIV-1 pathogenesis, but hampered by viral sequence diversity. An approach to minimize this diversity is to focus immunity on conserved proteome sequences; therefore we selected four relatively conserved regions (Gag amino acids 148-214 and 250-335, Env 521-606, and Nef 106-148), each created in three mosaics to provide better coverage of M-group HIV-1 sequences. A conserved region vaccine (CRV) delivering genes for these four regions as equal mixtures of three mosaics (each region at a separate injection site) was compared to a whole protein vaccine (WPV) delivering equimolar amounts of genes for whole Gag, Env, and Nef as clade B consensus sequences (separate injection sites). Three rhesus macaques were vaccinated via three DNA primes and a recombinant adenovirus-5 boost (weeks 0, 4, 8, and 24 respectively). Although CRV inserts were about a fifth that of WPV, the CRV generated comparable magnitude blood CD4(+) and CD8(+) T lymphocyte responses against Gag, Env, and Nef. WPV responses preferentially targeted proteome areas outside the selected conserved regions in direct proportion to sequence lengths, indicating similar immunogenicities for the conserved regions versus the outside regions. The CRV yielded conserved region targeting density that was approximately five-fold that of the WPV. A similar pattern was seen in bronchoalveolar lymphocytes, but quadruple the magnitudes in blood. Overall, these findings demonstrated that the selected conserved regions are highly immunogenic, and that anatomically isolated vaccinations with these regions focuses immunodominance compared to full-length protein vaccination. IMPORTANCE HIV-1 sequence diversity is a major barrier limiting the capability of cellular immunity to contain infection and the ability of vaccines to match circulating viral sequences. To date, vaccines tested in humans have delivered whole proteins or genes for whole proteins, and it is unclear whether including only conserved sequences would yield sufficient cellular immunogenicity. We tested a vaccine delivering genes for four small conserved HIV-1 regions compared to a control vaccine with genes for whole Gag, Env, and Nef. Although the conserved regions ranged from 43 to 86 amino acids and comprised less than one fifth of whole Gag/Env/Nef, the vaccines elicited equivalent total magnitudes of both CD4(+) and CD8(+) T lymphocyte responses. These data demonstrate immunogenicity of these small conserved regions, and the potential for a vaccine to steer immunodominance towards conserved epitopes.
    Journal of Virology 11/2014; 89(2). DOI:10.1128/JVI.02370-14 · 4.65 Impact Factor
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    ABSTRACT: A tumor-selective non-lytic retroviral replicating vector (RRV), Toca 511, and an extended-release formulation of 5-fluorocytosine (5-FC), Toca FC, are currently being evaluated in clinical trials in patients with recurrent high-grade glioma (NCT01156584, NCT01470794 and NCT01985256). Tumor-selective propagation of this RRV enables highly efficient transduction of glioma cells with cytosine deaminase (CD), which serves as a prodrug activator for conversion of the anti-fungal prodrug 5-FC to the anti-cancer drug 5-fluorouracil (5-FU) directly within the infected cells. We investigated whether, in addition to its direct cytotoxic effects, 5-FU generated intracellularly by RRV-mediated CD/5-FC prodrug activator gene therapy could also act as a radiosensitizing agent. Efficient transduction by RRV and expression of CD were confirmed in the highly aggressive, radioresistant human glioblastoma cell line U87EGFRvIII and its parental cell line U87MG (U87). RRV-transduced cells showed significant radiosensitization even after transient exposure to 5-FC. This was confirmed both in vitro by a clonogenic colony survival assay and in vivo by bioluminescence imaging analysis. These results provide a convincing rationale for development of tumor-targeted radiosensitization strategies utilizing the tumor-selective replicative capability of RRV, and incorporation of radiation therapy into future clinical trials evaluating Toca 511 and Toca FC in brain tumor patients.Cancer Gene Therapy advance online publication, 10 October 2014; doi:10.1038/cgt.2014.38.
    Cancer Gene Therapy 10/2014; 21(10). DOI:10.1038/cgt.2014.38 · 2.55 Impact Factor
  • 06/2014; 1:14024. DOI:10.1038/mtm.2014.24
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    ABSTRACT: We are developing a retroviral replicating vector (RRV) encoding cytosine deaminase (CD) as an anticancer agent for gliomas. Despite its demonstrated natural selectivity for tumors, and other safety features, such a virus could potentially cause off-target effects by productively infecting healthy tissues. Here, we investigated whether incorporation of a hematopoietic lineage-specific microRNA target sequence in RRVs further restricts replication in hematopoietic lineage-derived human cells in vitro and in murine lymphoid tissues in vivo. One or four copies of a sequence perfectly complementary to the guide strand of microRNA 142 3p were inserted into the 3'UTR of the RRV genome expressing the transgene GFP. Viral spread and GFP expression of these vectors in hematopoietic-lineage cells in vitro and in vivo were measured by qPCR, qRT-PCR and flow cytometry. In hematopoietic lineage-derived human cell lines and primary human stimulated PBMCs, vectors containing 142 3pT sequence showed a remarkable decrease in GFP expression relative to the parental vector, and viral spread was not observed over time. In a syngeneic subcutaneous mouse tumor model, RRV with and without the 142 3pT sequences spread equally well in tumor cells, were strongly repressed in blood, bone marrow and spleen, and generated antiviral immune responses. In an immune-deficient mouse model, RRV with 142 3pT sequences were strongly repressed in blood, bone marrow and spleen compared to unmodified RRV. Tissue-specific MicroRNA-based selective attenuation of retroviral replication can maintain antiviral immunity, and if needed, provide an additional safeguard to this delivery platform for gene therapy applications.
    Human gene therapy 05/2014; 25(8). DOI:10.1089/hum.2012.216 · 4.20 Impact Factor
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    ABSTRACT: Therapeutic gene transfer is currently being evaluated as a potential therapy for inflammatory bowel disease. This study investigates the safety and therapeutic benefit of a locally administered lentiviral vector encoding murine interleukin-10 in altering the onset and relapse of dextran sodium sulfate induced murine colitis. Lentiviral vectors encoding the reporter genes firefly-luciferase and murine interleukin-10 were administered by intrarectal instillation, either once or twice following an ethanol enema to facilitate mucosal uptake, on Days 3 and 20 in Balb/c mice with acute and relapsing colitis induced with dextran sulfate sodium (DSS). DSS colitis was characterized using clinical disease activity, macroscopic, and microscopic scores. Bioluminescence optical imaging analysis was employed to examine mucosal lentiviral vector uptake and transgene expression. Levels of tumor necrosis factor-alpha and interleukin-6 in homogenates of rectal tissue were measured by ELISA. Biodistribution of the lentiviral vector to other organs was evaluated by real time quantitative PCR. Mucosal delivery of lentiviral vector resulted in significant transduction of colorectal mucosa, as shown by bioluminescence imaging analysis. Lentiviral vector-mediated local expression of interleukin-10 resulted in significantly increased levels of this cytokine, as well as reduced levels of tumor necrosis factor-alpha and interleukin-6, and significantly reduced the clinical disease activity, macroscopic, and microscopic scores of DSS colitis. Systemic biodistribution of locally instilled lentiviral vector to other organs was not detected. Topically-delivered lentiviral vectors encoding interleukin-10 safely penetrated local mucosal tissue and had therapeutic benefit in this DSS model of murine colitis.
    BMC Gastroenterology 04/2014; 14(1):68. DOI:10.1186/1471-230X-14-68 · 2.11 Impact Factor
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    ABSTRACT: Despite recent advances in molecular classification, surgery, radiotherapy, and targeted therapies, the clinical outcome of patients with malignant brain tumors remains extremely poor. In this study, we have identified the tetraspan protein epithelial membrane protein-2 (EMP2) as a potential target for glioblastoma (GBM) killing. EMP2 had low or undetectable expression in normal brain, but was highly expressed in GBM as 95% of patients showed some expression of the protein. In GBM cells, EMP2 enhanced tumor growth in vivo in part by upregulating αvβ3 integrin surface expression, activating FAK and Src kinases, and promoting cell migration and invasion. Consistent with these findings, EMP2 expression significantly correlated with activated Src kinase in patient samples and promoted tumor cell invasion using intracranial mouse models. As a proof of principle to determine if EMP2 could serve as a target for therapy, cells were treated using specific anti-EMP2 antibody reagents. These reagents were effective in killing GBM cells in vitro and in reducing tumor load in subcutaneous mouse models. These results support the role of EMP2 in the pathogenesis of GBM and suggest that anti-EMP2 treatment may be a novel therapeutic treatment.
    Journal of Biological Chemistry 03/2014; 289(20). DOI:10.1074/jbc.M113.543728 · 4.60 Impact Factor
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    Molecular Cancer Therapeutics 01/2014; 12(11_Supplement):B225-B225. DOI:10.1158/1535-7163.TARG-13-B225 · 6.11 Impact Factor
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    ABSTRACT: Hepatocellular carcinoma (HCC) occurs predominantly in patients with liver cirrhosis. Here, we show an innovative RNA-based targeted approach to enhance endogenous albumin production whilst reducing liver tumour burden. We designed short-activating RNAs (saRNA) to enhance expression of C/EBPα (CCAAT/enhancer-binding protein-α), a transcriptional regulator and activator of albumin gene expression. Increased levels of both C/EBPα and albumin mRNA in addition to a 3-fold increase in albumin secretion and 50% decrease in cell proliferation was observed in C/EBPα-saRNA transfected HepG2 cells. Intravenous injection of C/EBPα-saRNA in a cirrhotic rat model with multifocal liver tumours increased circulating serum albumin by over 30% showing evidence of improved liver function. Tumour burden decreased by 80% (p = 0.003) with a 40% reduction in a marker of pre-neoplastic transformation. Since C/EBPα has known anti-proliferative activities via retinoblastoma, p21 and cyclins; we used mRNA expression liver cancer specific microarray in C/EBPα-saRNA transfected HepG2 cells to confirm down-regulation of genes strongly enriched for negative regulation of apoptosis, angiogenesis and metastasis. Up-regulated genes were enriched for tumour suppressors and positive regulators of cell differentiation. A quantitative PCR and Western-blot analysis of C/EBPα-saRNA transfected cells suggested that in addition to the known anti-proliferative targets of C/EBPα, we also observed suppression of IL6R, c-Myc and reduced STAT3 phosphorylation. Conclusion: We demonstrate for the first time that a novel injectable saRNA-oligonucleotide that enhances C/EBPα expression successfully reduces tumour burden and simultaneously improves liver function in a clinically relevant liver cirrhosis/HCC model. (Hepatology 2013;).
    Hepatology 01/2014; 59(1). DOI:10.1002/hep.26669 · 11.19 Impact Factor
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    ABSTRACT: Retroviral replicating vectors (RRVs) have been shown to achieve efficient tumor transduction and enhanced therapeutic benefit in a wide variety of cancer models. Here we evaluated two different RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV), in human malignant mesothelioma cells. In vitro, both RRVs expressing the green fluorescent protein gene efficiently replicated in most mesothelioma cell lines tested, but not in normal mesothelial cells. Notably, in ACC-MESO-1 mesothelioma cells that were not permissive for AMLV-RRV, the GALV-RRV could spread efficiently in culture and in mice with subcutaneous xenografts by in vivo fluorescence imaging. Next, GALV-RRV expressing the cytosine deaminase prodrug activator gene showed efficient killing of ACC-MESO-1 cells in a prodrug 5-fluorocytosine dose-dependent manner, compared with AMLV-RRV. GALV-RRV-mediated prodrug activator gene therapy achieved significant inhibition of subcutaneous ACC-MESO-1 tumor growth in nude mice. Quantitative reverse transcription PCR demonstrated that ACC-MESO-1 cells express higher PiT-1 (GALV receptor) and lower PiT-2 (AMLV receptor) compared with normal mesothelial cells and other mesothelioma cells, presumably accounting for the distinctive finding that GALV-RRV replicates much more robustly than AMLV-RRV in these cells. These data indicate the potential utility of GALV-RRV-mediated prodrug activator gene therapy in the treatment of mesothelioma.Cancer Gene Therapy advance online publication, 8 November 2013; doi:10.1038/cgt.2013.67.
    Cancer gene therapy 11/2013; DOI:10.1038/cgt.2013.67 · 3.13 Impact Factor
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    ABSTRACT: New treatments are needed for brain metastasis, which is associated with high morbidity and mortality. Two novel cellular and gene therapy modalities were evaluated in xenograft models for human breast cancer. The individual and especially the combined treatments with alloreactive cytotoxic T lymphocytes and replicating retroviral vectors coding for prodrug activating enzymes followed later with nontoxic prodrug demonstrated efficacy without off-target effects.
    OncoImmunology 10/2013; 2(10):e25989. DOI:10.4161/onci.25989 · 6.28 Impact Factor
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    ABSTRACT: Several studies have focused on the impact of bone morphogenetic protein (BMP) on prostate cancer homing and growth at distant metastatic sites, but very little on impact at the primary site. Here we used two cell lines, one (E8) isolated from a primary tumor and the other (cE1) from a recurrent tumor arising at the primary site, both from the conditional Pten deletion mouse model of prostatic adenocarcinoma. Over-expression of the BMP antagonist Noggin inhibited proliferation of cE1 cells in vitro while enhancing their ability to migrate. On the other hand cE1/Noggin grafts grown in vivo showed a greater mass and a higher proliferation index than the cE1/Control grafts. For suppression of BMP activity in the context of cancer associated fibroblasts (CAFs), we used Noggin-transduced CAFs from the same mouse model to determine their effect on E8 or cE1 induced tumor growth. CAF/Noggin led to increased tumor mass and greater de-differentiation of the E8 cell as compared to tumors formed in the presence of CAF/Control cells. A trend in increase in the size of the tumor was also noted for cE1 cells when inoculated with CAF/Noggin. Together, the results may point to a potential inhibitory role of BMP in the growth or re-growth of prostate tumor at the primary site. Additionally, results for cE1/Noggin, and cE1 mixed with CAF/Noggin suggested that suppression of BMP activity in the cancer cells may have a stronger growth enhancing effect on the tumor than its suppression in the fibroblastic compartment of the tumor microenvironment.
    Endocrine Related Cancer 09/2013; DOI:10.1530/ERC-13-0100 · 5.26 Impact Factor
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    ABSTRACT: Despite the progress in our understanding of genes essential for stem cell regulation and development, little is known about the factors secreted by stem cells and their effect on tissue regeneration. In particular, the factors secreted by human CD34+ cells remain to be elucidated. We have approached this challenge by performing a cytokine/growth factor microarray analysis of secreted soluble factors in medium conditioned by adherent human CD34+ cells. Thirty-two abundantly secreted factors have been identified, all of which are associated with cell proliferation, survival, tissue repair, and wound healing. The cultured CD34+ cells expressed known stem cell genes such as Nanog, Oct4, Sox2, c-Kit and HoxB4. The conditioned medium containing the secreted factors prevented cell death in liver cells exposed to liver toxin in vitro via inhibition of the caspase-3 signalling pathway. More importantly, in vivo studies using animal models of liver damage demonstrated that injection of the conditioned medium could repair damaged liver tissue (significant reduction in the necroinflammatory activity), as well as enable the animals to survive. Thus, we demonstrate that medium conditioned by human CD34+ cells has the potential for therapeutic repair of damaged tissue in vivo.Molecular Therapy (2013); doi:10.1038/mt.2013.194.
    Molecular Therapy 08/2013; DOI:10.1038/mt.2013.194 · 6.43 Impact Factor
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    ABSTRACT: Toca 511 (vocimagene amiretrorepvec), an amphotropic retroviral replicating vector (RRV), can successfully and safely deliver a functional, optimized cytosine deaminase (CD) gene to tumors in orthotopic glioma models. This agent, in conjunction with subsequent oral extended-release 5-fluorocytosine (5-FC) (Toca FC), is currently under investigation in patients with recurrent high-grade glioma . Temozolomide (TMZ) with radiation is the most frequently used first-line treatment for patients with glioblastoma, the most common and aggressive form of primary brain cancer in adults. However, subsets of patients with certain genetic alterations do not respond well to TMZ treatment and the overall median survival for patients who respond remains modest, suggesting that combinatorial approaches may be necessary to significantly improve outcomes. We show that in vitro TMZ delays but does not prevent RRV spread, nor interfere with Toca 511+5-FC-mediated cell killing in glioma tumor cells, and in vivo there is no significant hematologic effect from the combination of 5-FC and the clinically relevant dose of TMZ. A synergistic long-term survival advantage is observed in mice bearing an orthotopic TMZ-sensitive glioma after Toca 511 administration followed by coadministration of TMZ and 5-FC. These results provide support for the investigation of this novel combination treatment strategy in patients with newly diagnosed malignant glioma.Cancer Gene Therapy advance online publication, 23 August 2013; doi:10.1038/cgt.2013.51.
    Cancer gene therapy 08/2013; DOI:10.1038/cgt.2013.51 · 3.13 Impact Factor
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    ABSTRACT: Oncolytic virotherapy using adenoviruses has potential for therapeutic benefits in malignant mesothelioma. However, the downregulation of coxsackievirus/adenovirus receptor (CAR) expression is frequently a critical rate-limiting factor that impedes the effectiveness of adenovirus serotype 5 (Ad5)-based vectors in many cancer types. We evaluated CAR (Ad5 receptor) and CD46 [adenovirus serotype 35 (Ad35) receptor] expression in 6 human malignant mesothelioma cell lines. Very low CAR expression was observed in MSTO-211H and NCI-H2052 cells, whereas the other cell lines showed strong expression. In contrast, CD46 was highly expressed in all mesothelioma cell lines. On this basis, we replaced the CAR binding sequence of Ad5 with the CD46 binding sequence of Ad35 in the replication-defective adenoviruses and the tumor-specific midkine promoter-regulated oncolytic adenoviruses. By this fiber modification, the infectivity, virus progeny production, and in vitro cytocidal effect of the adenoviruses were significantly enhanced in low CAR-expressing MSTO-211H and NCI-H2052 cells, resulting in similar or even higher levels in high CAR-expressing mesothelioma cell lines. In MSTO-211H xenograft models, the fiber-modified oncolytic adenovirus significantly enhanced antitumor effect compared to its equivalent Ad5-based vector. Our data demonstrate that Ad35 fiber modification of binding tropism in a midkine promoter-regulated oncolytic Ad5 vector confers transductional targeting to oncolytic adenoviruses, thereby facilitating more effective treatment of malignant mesothelioma. This article is protected by copyright. All rights reserved.
    Cancer Science 08/2013; DOI:10.1111/cas.12267 · 3.53 Impact Factor
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    ABSTRACT: PURPOSE: Individual or combined strategies of cellular therapy with alloreactive cytotoxic T lymphocytes (alloCTL) and gene therapy employing retroviral replicating vectors (RRV) encoding a suicide prodrug activating gene were explored for the treatment of breast tumors metastatic to the brain. EXPERIMENTAL DESIGN: AlloCTL, sensitized to the human leukocyte antigens of MDA-MB-231 breast cancer cells, were examined in vitro for anti-tumor functionality toward breast cancer targets. RRV encoding the yeast cytosine deaminase (CD) gene was tested in vivo for virus spread, ability to infect, and kill breast cancer targets when exposed to 5-fluorocytosine (5-FC). Individual and combination treatments were tested in subcutaneous and intracranial xenograft models with 231BR, a brain tropic variant. RESULTS: AlloCTL preparations were cytotoxic, proliferated and produced interferon-gamma when coincubated with target cells displaying relevant HLA. In vivo, intratumorally-placed alloCTL trafficked through one established intracranial 231BR focus to another in contralateral brain and induced tumor cell apoptosis. RRV-CD efficiently spread in vivo, infected 231BR and induced their apoptosis upon 5-FC exposure. Subcutaneous tumor volumes were significantly reduced in alloCTL and/or gene therapy treated groups compared to control groups. Mice with established intracranial 231BR tumors treated with combined alloCTL and RRV-CD had a median survival of 97.5 days compared with single modalities (50-83 days); all experimental treatment groups survived significantly longer than sham-treated groups (median survivals 31.5 or 40 days) and exhibited good safety/toxicity profiles. CONCLUSION: The results indicate combining cellular and suicide gene therapies is a viable strategy for the treatment of established breast tumors in the brain.
    Clinical Cancer Research 06/2013; 19(15). DOI:10.1158/1078-0432.CCR-12-3735 · 8.19 Impact Factor
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    ABSTRACT: We have recently developed a novel and highly efficient strategy that exclusively uses the purine analog 6-thioguanine (6TG) for both pretransplantation conditioning and post-transplantation chemoselection of hypoxanthine-guanine phosphoribosyltransferase (HPRT)-deficient bone marrow (BM). In a mouse BM transplantation model, combined 6TG preconditioning and in vivo chemoselection consistently achieved >95% engraftment of HPRT-deficient donor BM and long-term reconstitution of histologically and immunophenotypically normal hematopoiesis in both primary and secondary recipients, without significant toxicity and in the absence of any other cytotoxic conditioning regimen. To translate this strategy for combined 6TG conditioning and chemoselection into a clinically feasible approach, it is necessary to develop methods for genetic modification of normal hematopoietic stem cells (HSC) to render them HPRT-deficient and thus 6TG-resistant. Here we investigated a strategy to reduce HPRT expression and thereby confer protection against 6TG myelotoxicity to primary murine BM cells by RNA interference (RNAi). Accordingly, we constructed and validated a lentiviral gene transfer vector expressing short-hairpin RNA (shRNA) that targets the murine HPRT gene. Our results showed that lentiviral vector-mediated delivery of HPRT-targeted shRNA could achieve effective and long-term reduction of HPRT expression. Furthermore, in both an established murine cell line as well as in primary murine BM cells, lentiviral transduction with HPRT-targeted shRNA was associated with enhanced resistance to 6TG cytotoxicity in vitro. Hence this represents a translationally feasible method to genetically engineer HSC for implementation of 6TG-mediated preconditioning and in vivo chemoselection.
    Transplantation Proceedings 06/2013; 45(5):2040-4. DOI:10.1016/j.transproceed.2013.01.020 · 0.95 Impact Factor
  • International Journal of Antimicrobial Agents 06/2013; 42:S128-S129. DOI:10.1016/S0924-8579(13)70515-6 · 4.26 Impact Factor

Publication Stats

2k Citations
555.85 Total Impact Points


  • 2006–2014
    • Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center
      • Department of Medicine
      Torrance, California, United States
    • Children's Hospital Los Angeles
      Los Angeles, California, United States
  • 2004–2014
    • University of California, Los Angeles
      • • Department of Molecular and Medical Pharmacology
      • • Department of Medicine
      • • Division of Digestive Diseases
      Los Ángeles, California, United States
  • 2009
    • University of Southampton
      Southampton, England, United Kingdom
  • 2008
    • Molecular and Cellular Biology Program
      Seattle, Washington, United States
  • 2003–2007
    • Memorial Sloan-Kettering Cancer Center
      New York City, New York, United States
  • 2001–2006
    • University of Southern California
      • • Keck School of Medicine
      • • Institute for Genetic Medicine
      • • Department of Pathology
      Los Angeles, California, United States