Jeffrey A Medin

University of Toronto, Toronto, Ontario, Canada

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Publications (155)709.98 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Suicide gene therapy of cancer (SGTC) entails the introduction of a cDNA sequence into tumor cells whose polypeptide product is capable of either directly activating apoptotic pathways itself or facilitating the activation of pharmacologic agents that do so. The latter class of SGTC approaches is of the greater utility in cancer therapy owing to the ability of some small, activated cytotoxic compounds to diffuse from their site of activation into neighboring malignant cells, where they can also mediate destruction. This phenomenon, termed "bystander killing", can be highly advantageous in driving significant tumor regression in vivo without the requirement of transduction of each and every tumor cell with the suicide gene. We have developed a robust suicide gene therapy enzyme/prodrug system based on an engineered variant of the human thymidylate kinase (TMPK), which has been endowed with the ability to drive azidothymidine (AZT) activation. Delivery of this suicide gene sequence into tumors by means of recombinant lentivirus-mediated transduction embodies an SGTC strategy that successfully employs bystander cell killing as a mechanism to achieve significant ablation of solid tumors in vivo. Thus, this engineered TMPK/AZT suicide gene therapy axis holds great promise for clinical application in the treatment of inoperable solid tumors in the neoadjuvant setting. Here we present detailed procedures for the preparation of recombinant TMPK-based lentivirus, transduction of target cells, and various approaches for the evaluation of bystander cell killing effects in SGCT in both in vitro and in vivo models.
    Methods in molecular biology (Clifton, N.J.) 06/2015; 1317:55-67. DOI:10.1007/978-1-4939-2727-2_4 · 1.29 Impact Factor
  • Robyn Aa Oldham · Elliot M Berinstein · Jeffrey A Medin ·
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    ABSTRACT: Basic science advances in cancer immunotherapy have resulted in various treatments that have recently shown success in the clinic. Many of these therapies require the insertion of genes into cells to directly kill them or to redirect the host's cells to induce potent immune responses. Other analogous therapies work by modifying effector cells for improved targeting and enhanced killing of tumor cells. Initial studies done using γ-retroviruses were promising, but safety concerns centered on the potential for insertional mutagenesis have highlighted the desire to develop other options for gene delivery. Lentiviral vectors (LVs) have been identified as potentially more effective and safer alternative delivery vehicles. LVs are now in use in clinical trials for many different types of inherited and acquired disorders, including cancer. This review will discuss current knowledge of LVs and the applications of this viral vector-based delivery vehicle to cancer immunotherapy.
    Immunotherapy 03/2015; 7(3):271-84. DOI:10.2217/imt.14.108 · 2.07 Impact Factor
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    ABSTRACT: - Copyright © 2015, Ferrata Storti Foundation.
    Haematologica 02/2015; 100(5). DOI:10.3324/haematol.2014.108530 · 5.81 Impact Factor

  • Molecular Genetics and Metabolism 02/2015; 114(2):S38-S39. DOI:10.1016/j.ymgme.2014.12.070 · 2.63 Impact Factor

  • Molecular Genetics and Metabolism 02/2015; 114(2):S127-S128. DOI:10.1016/j.ymgme.2014.12.293 · 2.63 Impact Factor

  • Clinical Biochemistry 10/2014; 47(15):151-151. DOI:10.1016/j.clinbiochem.2014.07.079 · 2.28 Impact Factor

  • Clinical Biochemistry 10/2014; 47(15):141-141. DOI:10.1016/j.clinbiochem.2014.07.049 · 2.28 Impact Factor
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    Michael J Ricci · Jeffrey A Medin · Ronan S Foley ·
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    ABSTRACT: Allogeneic bone marrow transplant is a life-saving procedure for adults and children that have high-risk or relapsed hematological malignancies. Incremental advances in the procedure, as well as expanded sources of donor hematopoietic cell grafts have significantly improved overall rates of success. Yet, the outcomes for patients for whom suitable donors cannot be found remain a significant limitation. These patients may benefit from a hematopoietic cell transplant wherein a relative donor is fully haplotype mismatched. Previously this procedure was limited by graft rejection, lethal graft-versus-host disease, and increased treatment-related toxicity. Recent approaches in haplo-identical transplantation have demonstrated significantly improved outcomes. Based on years of incremental pre-clinical research into this unique form of bone marrow transplant, a range of approaches have now been studied in patients in relatively large phase II trials that will be summarized in this review.
    09/2014; 6(4):380-90. DOI:10.4252/wjsc.v6.i4.380
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    ABSTRACT: Inciting the cellular arm of adaptive immunity has been the fundamental goal of cancer immunotherapy strategies, specifically focusing on inducing tumour antigen-specific responses by CD8+ cytotoxic T lymphocytes (CTLs). However, there is an emerging appreciation that the cytotoxic function of CD4+ T cells can be effective in a clinical setting. Harnessing this potential will require an understanding of how such cells arise. In this study we use an IL-12 transduced variant of the 70Z/3 leukemia cell line in a B6D2F1 (BDF1) murine model system to reveal a novel cascade of cells and soluble factors that activate anti-cancer CD4+ killer cells. We show that natural killer T (NKT) cells play a pivotal role by activating dendritic cells (DCs) in a contact-dependent manner; soluble products of this interaction, including MCP-1, propagate the activation signal culminating in development of CD4+CTL that directly mediate an anti-leukemia response while also orchestrating a multi-pronged attack by other effector cells. A more complete picture of the conditions that induce such a robust response will allow us to capitalize on CD4+ T cell plasticity for maximum therapeutic effect.
    08/2014; 2(11). DOI:10.1158/2326-6066.CIR-13-0208
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    ABSTRACT: A novel MALDI-FTICR imaging mass spectrometry (MALDI-IMS) workflow is described for on-tissue detection, spatial localization and structural confirmation of low abundance bioactive ceramides and other sphingolipids. Increasingly, altered or elevated levels of sphingolipids, sphingolipid metabolites, and sphingolipid metabolizing enzymes have been associated with a variety of disorders such as diabetes, obesity, lysosomal storage disorders, and cancer. Ceramide, which serves as a metabolic hub in sphingolipid metabolism, has been linked to cancer signaling pathways and to metabolic regulation with involvement in autophagy, cell-cycle arrest, senescence, and apoptosis. Using kidney tissues from a new Farber disease mouse model in which ceramides of all acyl chain lengths and other sphingolipid metabolites accumulate in tissues, specific ceramides and sphingomyelins were identified by on-tissue isolation and fragmentation, coupled with an on-tissue digestion by ceramidase or sphingomyelinase. Multiple glycosphingolipid species were also detected. The newly generated library of sphingolipid ions was then applied to MALDI-IMS of human lung cancer tissues. Multiple tumor specific ceramide and sphingomyelin species were detected and confirmed by on-tissue enzyme digests and structural confirmation. High-resolution MALDI-IMS in combination with novel on-tissue ceramidase and sphingomyelinase enzyme digestions makes it now possible to rapidly visualize the distribution of bioactive ceramides and sphingomyelin in tissues.
    Analytical Chemistry 07/2014; 86(16). DOI:10.1021/ac501937d · 5.64 Impact Factor

  • Molecular Genetics and Metabolism 02/2014; 111(2):S39. DOI:10.1016/j.ymgme.2013.12.075 · 2.63 Impact Factor

  • Molecular Genetics and Metabolism 02/2014; 111(2):S56-S57. DOI:10.1016/j.ymgme.2013.12.123 · 2.63 Impact Factor

  • Molecular Genetics and Metabolism 02/2014; 111(2):S87-S88. DOI:10.1016/j.ymgme.2013.12.212 · 2.63 Impact Factor

  • Molecular Genetics and Metabolism 02/2014; 111(2):S93. DOI:10.1016/j.ymgme.2013.12.227 · 2.63 Impact Factor
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    ABSTRACT: Interleukin (IL)-12 is the key cytokine in the initiation of a Th1 response and has shown promise as an anti-cancer agent; however, clinical trials involving IL-12 have been unsuccessful due to toxic side-effects. To address this issue, lentiviral vectors were used to transduce tumour cell lines that were injected as an autologous tumour cell vaccine. The focus of the current study was to test the efficacy of this approach in a solid tumour model. SCCVII cells that were transduced to produce IL-12 at different concentrations were then isolated. Subcutaneous injection of parental SCCVII cells results in tumour development, while a mixture of IL-12-producing and non-producing cells results in tumour clearance. Interestingly, when comparing mice injected a mixture of SCCVII and either high IL-12-producing tumour cells or low IL-12-producing tumour cells, we observed that mixtures containing small amounts of high producing cells lead to tumour clearance, whereas mixtures containing large amounts of low producing cells fail to elicit protection, despite the production of equal amounts of total IL-12 in both mixtures. Furthermore, immunizing mice with IL-12-producing cells leads to the establishment of both local and systemic immunity against challenge with SCCVII. Using depletion antibodies, it was shown that both CD4(+) and CD8(+) cells are crucial for therapy. Lastly, we have established cell clones of other solid tumour cell lines (RM-1, LLC1 and moto1.1) that produce IL-12. Our results show that the delivery of IL-12 by cancer cells is an effective route for immune activation.
    Journal of Cellular and Molecular Medicine 11/2013; 17(11). DOI:10.1111/jcmm.12121 · 4.01 Impact Factor
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    ABSTRACT: We previously described a novel suicide (or 'cell fate control') gene therapy enzyme/prodrug system based on an engineered variant of human thymidylate kinase (TMPK) that potentiates azidothymidine (AZT) activation. Delivery of a suicide gene sequence into tumors by lentiviral transduction embodies a cancer gene therapy that could employ bystander cell killing as a mechanism driving significant tumor regression in vivo. Here we present evidence of a significant bystander cell killing in vitro and in vivo mediated by the TMPK/AZT suicide gene axis that is reliant on the formation of functional gap-junctional intercellular communications (GJICs). Potentiation of AZT activation by the engineered TMPK expressed in the human prostate cancer cell line, PC-3, resulted in effective bystander killing of PC-3 cells lacking TMPK expression - an effect that could be blocked by the GJIC inhibitor, carbenoxolone. Although GJICs are mainly formed by connexins, a new family of GJIC molecules designated pannexins has been recently identified. PC-3 cells expressed both connexin43 (Cx43) and Pannexin1 (Panx1), but Panx1 expression predominated at the plasma membrane, whereas Cx43 expression was primarily localized to the cytosol. The contribution of bystander effects to the reduction of solid tumor xenografts established by the PC-3 cell line was evaluated in an animal model. We demonstrate the contribution of bystander cell killing to tumor regression in a xenograft model relying on the delivery of expression of the TMPK suicide gene into tumors via direct intratumoral injection of recombinant therapeutic lentivirus. Taken together, our data underscore that the TMPK/AZT enzyme-prodrug axis can be effectively utilized in suicide gene therapy of solid tumors, wherein significant tumor regression can be achieved via bystander effects mediated by GJICs.
    PLoS ONE 10/2013; 8(10):e78711. DOI:10.1371/journal.pone.0078711 · 3.23 Impact Factor
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    ABSTRACT: Dendritic cells (DCs) are promising mediators of anti-tumor immune responses due to their potent antigen-presentation capacity. Unfortunately, cancer cells can often disarm differentiated DCs by rendering them incapable of maturation or by promoting their apoptosis. DC vaccine regimens attempt to generate functional DCs and preload them with Tumor-Associated Antigens (TAAs) to target various malignancies. Despite these efforts, the efficacy of DC vaccines in clinical trials is still rather disappointing to date. In addition to undergoing cancer-induced apoptosis, it is well established that DCs are intrinsically short-lived cell types. It is likely that a significant portion of infused DCs undergo apoptosis prior to locating and activating naive TAA-reactive T-cells. In our current study, we constructed and investigated novel bicistronic lentivectors (LVs) encoding the cDNA for the xeno-TAA, rat HER-2/neu (rHER-2), along with five candidate mouse DC survival factors (c-FLIPS, c-FLIPL, Bcl-XL, M11L, and AKT-1) that operate in both the extrinsic and intrinsic cycle of apoptosis. The murine DC cell line, DC2.4 was transduced separately with each novel LV construct. Infected cells were enriched via flow cytometric methods based on rHER-2 expression. Transduced DC2.4 cell lines were then exposed to Fetal Calf Serum (FCS) withdrawal and to specific pharmacological apoptosis-inducing agents. DC2.4 cell death was assayed based on Annexin V and PI double-positive staining via flow cytometry. The phenotype and function of transduced DC2.4 cells and primary bone marrow-derived DCs were then assessed via expression and secretion of DC markers and cytokines, respectively. DC2.4 cells transduced with LVs encoding cDNAs for c-FLIPS, c-FLIPL, Bcl-XL, and M11L were protected from apoptosis when exposed to low FCS-containing culture media. When treated with an anti-CD95 antibody, only DC2.4 cells transduced with LVs encoding c-FLIPS and c-FLIPL were protected from apoptosis. In contrast, only DC2.4 cells transduced with LVs encoding Bcl-XL and M11L were protected from effects of staurosporine (STS) treatment. Also, LV-modified DCs maintained their original phenotype and function. We present evidence that by employing novel recombinant bicistronic LVs we can simultaneously load DCs with a relevant TAA and block apoptosis; thereby confirming the usage of such LVs in the modulation of DC lifespan and function.
    Virology Journal 07/2013; 10(1):240. DOI:10.1186/1743-422X-10-240 · 2.18 Impact Factor
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    ABSTRACT: Farber disease (FD) is a severe inherited disorder of lipid metabolism characterized by deficient lysosomal acid ceramidase (ACDase) activity, resulting in ceramide accumulation. Ceramide and metabolites have roles in cell apoptosis and proliferation. We introduced a single-nucleotide mutation identified in human FD patients into the murine Asah1 gene to generate the first model of systemic ACDase deficiency. Homozygous Asah1P361R/P361R animals showed ACDase defects, accumulated ceramide, demonstrated FD manifestations and died within 7–13 weeks. Mechanistically, MCP-1 levels were increased and tissues were replete with lipid-laden macrophages. Treatment of neonates with a single injection of human ACDase-encoding lentivector diminished the severity of the disease as highlighted by enhanced growth, decreased ceramide, lessened cellular infiltrations and increased lifespans. This model of ACDase deficiency offers insights into the pathophysiology of FD and the roles of ACDase, ceramide and related sphingolipids in cell signaling and growth, as well as facilitates the development of therapy. →See accompanying article
    EMBO Molecular Medicine 06/2013; 5(6). DOI:10.1002/emmm.201202301 · 8.67 Impact Factor
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    ABSTRACT: The purpose of the study was to examine the effect of lentivirus-mediated IL-10 gene therapy to target lung allograft rejection in a mouse orthotopic left lung transplantation model. IL-10 may regulate posttransplant immunity mediated by IL-17. Lentivirus-mediated trans-airway luciferase gene transfer to the donor lung resulted in persistent luciferase activity up to 6 months posttransplant in the isograft (B6 to B6); luciferase activity decreased in minor-mismatched allograft lungs (B10 to B6) in association with moderate rejection. Fully MHC-mismatched allograft transplantation (BALB/c to B6) resulted in severe rejection and complete loss of luciferase activity. In minor-mismatched allografts, IL-10-encoding lentivirus gene therapy reduced the acute rejection score compared with the lentivirus-luciferase control at posttransplant day 28 (3.0 ± 0.6 vs. 2.0 ± 0.6 (mean ± SD); p = 0.025; n = 6/group). IL-10 gene therapy also significantly reduced gene expression of IL-17, IL-23, and retinoic acid-related orphan receptor (ROR)-γt without affecting levels of IL-12 and interferon-γ (IFN-γ). Cells expressing IL-17 were dramatically reduced in the allograft lung. In conclusion, lentivirus-mediated IL-10 gene therapy significantly reduced expression of IL-17 and other associated genes in the transplanted allograft lung and attenuated posttransplant immune responses after orthotopic lung transplantation.
    American Journal of Transplantation 04/2013; 13(6). DOI:10.1111/ajt.12230 · 5.68 Impact Factor
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    ABSTRACT: We hypothesized that rapamycin, through induction of autophagy and promotion of an antiapoptotic phenotype, would permit lentiviral (LV)-based transgene delivery to human T-Rapa cells, which are being tested in phase II clinical trials in the setting of allogeneic hematopoietic cell transplantation. Manufactured T-Rapa cells were exposed to supernatant enriched for a LV vector encoding a fusion protein consisting of truncated CD19 (for cell surface marking) and DTYMK/TMPKΔ, which provides "cell-fate control" due to its ability to phosphorylate (activate) AZT prodrug. LV-transduction in rapamycin-treated T-Rapa cells: (1) resulted in mitochondrial autophagy and a resultant antiapoptotic phenotype, which was reversed by the autophagy inhibitor 3-MA; (2) yielded changes in MAP1LC3B and SQSTM1 expression, which were reversed by 3-MA; and (3) increased T-Rapa cell expression of the CD19-DTYMKΔ fusion protein, despite their reduced proliferative status. Importantly, although the transgene-expressing T-Rapa cells expressed an antiapoptotic phenotype, they were highly susceptible to cell death via AZT exposure both in vitro and in vivo (in a human-into-mouse xenogeneic transplantation model). Therefore, rapamycin induction of T cell autophagy can be used for gene therapy applications, including the CD19-DTYMKΔ cell-fate control axis to improve the safety of T cell immuno-gene therapy.
    Autophagy 04/2013; 9(7). DOI:10.4161/auto.24639 · 11.75 Impact Factor

Publication Stats

3k Citations
709.98 Total Impact Points


  • 2002-2015
    • University of Toronto
      • • Institute of Medical Sciences
      • • Department of Medical Biophysics
      Toronto, Ontario, Canada
  • 2014
    • McMaster University
      • Department of Pathology and Molecular Medicine
      Hamilton, Ontario, Canada
  • 2004-2014
    • University Health Network
      • Division of Experimental Therapeutics
      Toronto, Ontario, Canada
  • 2013
    • Okayama Rosai Hospital
      Okayama, Okayama, Japan
  • 2012
    • The Princess Margaret Hospital
      Toronto, Ontario, Canada
  • 2004-2011
    • Ontario Institute for Cancer Research
      Toronto, Ontario, Canada
  • 2010
    • University of Alberta
      • Department of Pediatrics
      Edmonton, Alberta, Canada
  • 2007
    • University of Guelph
      • Department of Biomedical Sciences
      Guelph, Ontario, Canada
  • 2006
    • University of California, San Diego
      • Division of Cardiology
      San Diego, California, United States
  • 1999-2006
    • University of Illinois at Chicago
      • Section of Hematology and Oncology
      Chicago, IL, United States
  • 1993-1998
    • National Institutes of Health
      • • Laboratory of Cell Biology
      • • Laboratory of Molecular Immunoregulation
      베서스다, Maryland, United States
  • 1993-1997
    • National Institute of Child Health and Human Development
      Maryland, United States
  • 1992-1995
    • University of North Carolina at Chapel Hill
      • Department of Biochemistry and Biophysics
      Chapel Hill, NC, United States
  • 1990
    • University of Kentucky
      • Department of Biochemistry
      Lexington, Kentucky, United States