Bio

Professional Education


  • Doctor of Philosophy, Dalhousie University (2018)
  • Bachelor of Science, Dalhousie University (2012)

Stanford Advisors


Publications

All Publications


  • Trial Watch: oncolytic viro-immunotherapy of hematologic and solid tumors Oncolmmunology Pol, J. G., Levesque, S., Workenhe, S. T., Gujar, S., Le Boeuf, F., Clements, D. R., Fahrner, J., Fend, L., Bell, J. C., Mossman, K. L., Fucikova, J., Spisek, R., Zitvogel, L., Kroemer, G., Galluzi, L. 2018
  • Quantitative Temporal in Vivo Proteomics Deciphers the Transition of Virus-Driven Myeloid Cells into M2 Macrophages. Journal of proteome research Clements, D. R., Murphy, J. P., Sterea, A., Kennedy, B. E., Kim, Y., Helson, E., Almasi, S., Holay, N., Konda, P., Paulo, J. A., Sharif, T., Lee, P. W., Weekes, M. P., Gygi, S. P., Gujar, S. 2017; 16 (9): 3391–3406

    Abstract

    Myeloid cells play a central role in the context of viral eradication, yet precisely how these cells differentiate throughout the course of acute infections is poorly understood. In this study, we have developed a novel quantitative temporal in vivo proteomics (QTiPs) platform to capture proteomic signatures of temporally transitioning virus-driven myeloid cells directly in situ, thus taking into consideration host-virus interactions throughout the course of an infection. QTiPs, in combination with phenotypic, functional, and metabolic analyses, elucidated a pivotal role for inflammatory CD11b+, Ly6G-, Ly6Chigh-low cells in antiviral immune response and viral clearance. Most importantly, the time-resolved QTiPs data set showed the transition of CD11b+, Ly6G-, Ly6Chigh-low cells into M2-like macrophages, which displayed increased antigen-presentation capacities and bioenergetic demands late in infection. We elucidated the pivotal role of myeloid cells in virus clearance and show how these cells phenotypically, functionally, and metabolically undergo a timely transition from inflammatory to M2-like macrophages in vivo. With respect to the growing appreciation for in vivo examination of viral-host interactions and for the role of myeloid cells, this study elucidates the use of quantitative proteomics to reveal the role and response of distinct immune cell populations throughout the course of virus infection.

    View details for DOI 10.1021/acs.jproteome.7b00425

    View details for PubMedID 28768414

    View details for PubMedCentralID PMC5648240

  • All that glitters is not gold: the need to consider desirable and undesirable immune aspects of oncolytic virus therapy ONCOIMMUNOLOGY Clements, D. R., Kim, Y., Gujar, S. A., Lee, P. W. 2016; 5 (1)

    Abstract

    Oncolytic viruses (OVs), a novel class of anticancer therapeutic agents, can overturn cancer-mediated immunosuppression and initiate antitumor immunity. Contrary to this paradigm, our recent study illustrates that oncolytic reovirus transiently augments cancer-associated immunosuppression immediately following its therapeutic administration. To achieve the optimum efficacy for OV-based anticancer therapies, the pathophysiological as well as clinical implications of this phenomenon need to be considered.

    View details for DOI 10.1080/2162402X.2015.1057674

    View details for Web of Science ID 000373383600002

    View details for PubMedID 26942069

    View details for PubMedCentralID PMC4760287

  • Dendritic Cells in Oncolytic Virus-Based Anti-Cancer Therapy VIRUSES-BASEL Kim, Y., Clements, D. R., Sterea, A. M., Jang, H. W., Gujar, S. A., Lee, P. W. 2015; 7 (12): 6506-6525

    Abstract

    Dendritic cells (DCs) are specialized antigen-presenting cells that have a notable role in the initiation and regulation of innate and adaptive immune responses. In the context of cancer, appropriately activated DCs can induce anti-tumor immunity by activating innate immune cells and tumor-specific lymphocytes that target cancer cells. However, the tumor microenvironment (TME) imposes different mechanisms that facilitate the impairment of DC functions, such as inefficient antigen presentation or polarization into immunosuppressive DCs. These tumor-associated DCs thus fail to initiate tumor-specific immunity, and indirectly support tumor progression. Hence, there is increasing interest in identifying interventions that can overturn DC impairment within the TME. Many reports thus far have studied oncolytic viruses (OVs), viruses that preferentially target and kill cancer cells, for their capacity to enhance DC-mediated anti-tumor effects. Herein, we describe the general characteristics of DCs, focusing on their role in innate and adaptive immunity in the context of the TME. We also examine how DC-OV interaction affects DC recruitment, OV delivery, and anti-tumor immunity activation. Understanding these roles of DCs in the TME and OV infection is critical in devising strategies to further harness the anti-tumor effects of both DCs and OVs, ultimately enhancing the efficacy of OV-based oncotherapy.

    View details for DOI 10.3390/v7122953

    View details for Web of Science ID 000367536700027

    View details for PubMedID 26690204

    View details for PubMedCentralID PMC4690876

  • Newly Recruited CD11b(+), GR-1(+), Ly6C(high) Myeloid Cells Augment Tumor-Associated Immunosuppression Immediately following the Therapeutic Administration of Oncolytic Reovirus JOURNAL OF IMMUNOLOGY Clements, D. R., Sterea, A. M., Kim, Y., Helson, E., Dean, C. A., Nunokawa, A., Coyle, K. M., Sharif, T., Marcato, P., Gujar, S. A., Lee, P. W. 2015; 194 (9): 4397-4412

    Abstract

    Tumor-associated immunosuppression aids cancer cells to escape immune-mediated attack and subsequent elimination. Recently, however, many oncolytic viruses, including reovirus, have been reported to overturn such immunosuppression and promote the development of a clinically desired antitumor immunity, which is known to promote favorable patient outcomes. Contrary to this existing paradigm, in this article we demonstrate that reovirus augments tumor-associated immunosuppression immediately following its therapeutic administration. Our data show that reovirus induces preferential differentiation of highly suppressive CD11b(+), Gr-1(+), Ly6C(high) myeloid cells from bone marrow hematopoietic progenitor cells. Furthermore, reovirus administration in tumor-bearing hosts drives time-dependent recruitment of CD11b(+), Gr-1(+), Ly6C(high) myeloid cells in the tumor milieu, which is further supported by virus-induced increased expression of numerous immune factors involved in myeloid-derived suppressor cell survival and trafficking. Most importantly, CD11b(+), Gr-1(+), Ly6C(high) myeloid cells specifically potentiate the suppression of T cell proliferation and are associated with the absence of IFN-γ response in the tumor microenvironment early during oncotherapy. Considering that the qualitative traits of a specific antitumor immunity are largely dictated by the immunological events that precede its development, our findings are of critical importance and must be considered while devising complementary interventions aimed at promoting the optimum efficacy of oncolytic virus-based anticancer immunotherapies.

    View details for DOI 10.4049/jimmunol.1402132

    View details for Web of Science ID 000353727400038

    View details for PubMedID 25825443

  • Gemcitabine enhances the efficacy of reovirus-based oncotherapy through anti-tumour immunological mechanisms BRITISH JOURNAL OF CANCER Gujar, S. A., CLEMENTS, D., Dielschneider, R., Helson, E., Marcato, P., Lee, P. W. 2014; 110 (1): 83-93

    Abstract

    Reovirus preferentially infects and kills cancer cells and is currently undergoing clinical trials internationally. While oncolysis is the primary mode of tumour elimination, increasing evidence illustrates that reovirus additionally stimulates anti-tumour immunity with a capacity to target existing and possibly relapsing cancer cells. These virus-induced anti-tumour immune activities largely determine the efficacy of oncotherapy. On the other hand, anti-viral immune responses can negatively affect oncotherapy. Hence, the strategic management of anti-tumour and anti-viral immune responses through complementary therapeutics is crucial to achieve the maximum anti-cancer benefits of oncotherapy.Intra-peritoneal injection of mouse ovarian surface epithelial cells (ID8 cells) into wild-type C57BL/6 mice was treated with a therapeutic regimen of reovirus and/or gemcitabine and then analysed for prolonged survival, disease pathology, and various immunological parameters. Furthermore, in vitro analyses were conducted to assess apoptosis, viral spread, and viral production during reovirus and/or gemcitabine treatment.We demonstrate that reovirus and gemcitabine combination treatment postpones peritoneal carcinomatosis development and prolongs the survival of cancer-bearing hosts. Importantly, these anti-cancer benefits are generated through various immunological mechanisms, including: (1) inhibition of myeloid-derived suppressor cells recruitment to the tumour microenvironment, (2) downmodulation of pro-MDSC factors, and (3) accelerated development of anti-tumour T-cell responses.The complementation of reovirus with gemcitabine further potentiates virus-initiated anti-cancer immunity and enhances the efficacy of oncotherapy. In the context of ongoing clinical trials, our findings represent clinically relevant information capable of enhancing cancer outcomes.

    View details for DOI 10.1038/bjc.2013.695

    View details for Web of Science ID 000329493700013

    View details for PubMedID 24281006

    View details for PubMedCentralID PMC3887295

  • Two is better than one Complementing oncolytic virotherapy with gemcitabine to potentiate antitumor immune responses ONCOIMMUNOLOGY Gujar, S. A., Clements, D., Lee, P. W. 2014; 3 (1)

    Abstract

    Oncolytic viruses (OVs) preferentially infect and kill cancer cells. Additionally, OV-induced immune responses subvert cancer-associated immunosuppression and promote antitumor immunity. We have recently demonstrated that the complementation of oncolytic virotherapy with gemcitabine accentuates its immunostimulatory effects, hence exerting superior antineoplastic activity.

    View details for DOI 10.4161/onci.27622

    View details for Web of Science ID 000339952700045

    View details for PubMedID 24804161

    View details for PubMedCentralID PMC4010537

  • Reovirus in cancer therapy: an evidence-based review. Oncolytic virotherapy Clements, D., Helson, E., Gujar, S. A., Lee, P. W. 2014; 3: 69-82

    Abstract

    Reovirus, a double-stranded ribonucleic acid virus and benign human pathogen, preferentially infects and kills cancer cells in its unmodified form, and is one of the leading oncolytic viruses currently undergoing clinical trials internationally. With 32 clinical trials completed or ongoing thus far, reovirus has demonstrated clinical therapeutic applicability against a multitude of cancers, including but not limited to breast cancer, prostate cancer, pancreatic cancer, malignant gliomas, advanced head and neck cancers, and metastatic ovarian cancers. Phase I trials have demonstrated that reovirus is safe to use via both intralesional/intratumoral and systemic routes of administration, with the most common adverse reactions being grade I/II toxicities, such as flu-like illness (fatigue, nausea, vomiting, headache, fever/chills, dizziness), diarrhea, and lymphopenia. In subsequent Phase II trials, reovirus administration was demonstrated to successfully decrease tumor size and promote tumor necrosis, thereby complementing compelling preclinical evidence of tumor destruction by the virus. Importantly, reovirus has been shown to be effective as a monotherapy, as well as in combination with other anticancer options, including radiation and chemotherapeutic agents, such as gemcitabine, docetaxel, paclitaxel, and carboplatin. Of note, the first Phase III clinical trial using reovirus in combination with paclitaxel and carboplatin for the treatment of head and neck cancers is under way. Based on the evidence from clinical trials, we comprehensively review the use of reovirus as an anticancer agent, acknowledge key obstacles, and suggest future directions to ultimately potentiate the efficacy of reovirus oncotherapy.

    View details for DOI 10.2147/OV.S51321

    View details for PubMedID 27512664

    View details for PubMedCentralID PMC4918368

  • TRPM2 ion channel promotes gastric cancer migration, invasion and tumor growth through the AKT signaling pathway. Scientific reports Almasi, S., Sterea, A. M., Fernando, W., Clements, D. R., Marcato, P., Hoskin, D. W., Gujar, S., El Hiani, Y. 2019; 9 (1): 4182

    Abstract

    Transient Receptor Potential Melastatin-2 (TRPM2) ion channel is emerging as a great therapeutic target in many types of cancer, including gastric cancer - a major health threat of cancer related-death worldwide. Our previous study demonstrated the critical role of TRPM2 in gastric cancer cells bioenergetics and survival; however, its role in gastric cancer metastasis, the major cause of patient death, remains unknown. Here, using molecular and functional assays, we demonstrate that TRPM2 downregulation significantly inhibits the migration and invasion abilities of gastric cancer cells, with a significant reversion in the expression level of metastatic markers. These effects were concomitant with decreased Akt and increased PTEN activities. Finally, TRPM2 silencing resulted in deregulation of metastatic markers and abolished the tumor growth ability of AGS gastric cancer cells in NOD/SCID mice. Taken together, our results provide compelling evidence on the important function of TRPM2 in the modulation of gastric cancer cell invasion likely through controlling the PTEN/Akt pathway.

    View details for PubMedID 30862883

  • RTN4 Knockdown Dysregulates the AKT Pathway, Destabilizes the Cytoskeleton, and Enhances Paclitaxel-Induced Cytotoxicity in Cancers MOLECULAR THERAPY Pathak, G. P., Shah, R., Kennedy, B. E., Murphy, J., Clements, D., Konda, P., Giacomantonio, M., Xu, Z., Schlaepfer, I. R., Gujar, S. 2018; 26 (8): 2019–33

    Abstract

    Reticulon-4 (RTN4), commonly known as a neurite outgrowth inhibitor (Nogo), is emerging as an important player in human cancers. Clinically, we found lower RTN4 expression in patient-derived tumors was associated with significantly better survival in lung, breast, cervical, and renal cancer patients. To identify the role of RTN4 in cancer biology, we performed mass spectrometry-based quantitative proteomic analysis on cancer cells following RTN4 knockdown and found its link with pro-survival as well as cytoskeleton-related processes. Subsequent mechanistic investigations revealed that RTN4 regulates lipid homeostasis, AKT signaling, and cytoskeleton modulation. In particular, downregulation of RTN4 reduced sphingomyelin synthesis and impaired plasma membrane localization of AKT, wherein AKT phosphorylation, involved in many cancers, was significantly reduced without any comparable effect on AKT-related upstream kinases, in a sphingolipid-dependent manner. Furthermore, knockdown of RTN4 retarded proliferation of cancer cells in vitro as well as tumor xenografts in mice. Finally, RTN4 knockdown affected tubulin stability and promoted higher cytotoxic effects with chemotherapeutic paclitaxel in cancer cells both in vitro and in vivo. In summary, RTN4 is involved in carcinogenesis and represents a molecular candidate that may be targeted to achieve desired antitumor effects in clinics.

    View details for DOI 10.1016/j.ymthe.2018.05.026

    View details for Web of Science ID 000441547500019

    View details for PubMedID 30078441

    View details for PubMedCentralID PMC6094397

  • Epigenetic Silencing of TAP1 in Aldefluor+ Breast Cancer Stem Cells Contributes to Their Enhanced Immune Evasion. Stem cells (Dayton, Ohio) Sultan, M., Vidovic, D., Paine, A. S., Huynh, T. T., Coyle, K. M., Thomas, M. L., Cruickshank, B. M., Dean, C. A., Clements, D. R., Kim, Y., Lee, K., Gujar, S. A., Weaver, I. C., Marcato, P. 2018; 36 (5): 641–54

    Abstract

    Avoiding detection and destruction by immune cells is key for tumor initiation and progression. The important role of cancer stem cells (CSCs) in tumor initiation has been well established, yet their ability to evade immune detection and targeting is only partly understood. To investigate the ability of breast CSCs to evade immune detection, we identified a highly tumorigenic population in a spontaneous murine mammary tumor based on increased aldehyde dehydrogenase activity. We performed tumor growth studies in immunocompetent and immunocompromised mice. In immunocompetent mice, growth of the spontaneous mammary tumor was restricted; however, the Aldefluor+ population was expanded, suggesting inherent resistance mechanisms. Gene expression analysis of the sorted tumor cells revealed that the Aldefluor+ tumor cells has decreased expression of transporter associated with antigen processing (TAP) genes and co-stimulatory molecule CD80, which would decrease susceptibility to T cells. Similarly, the Aldefluor+ population of patient tumors and 4T1 murine mammary cells had decreased expression of TAP and co-stimulatory molecule genes. In contrast, breast CSCs identified by CD44+ CD24- do not have decreased expression of these genes, but do have increased expression of C-X-C chemokine receptor type 4. Decitabine treatment and bisulfite pyrosequencing suggests that DNA hypermethylation contributes to decreased TAP gene expression in Aldefluor+ CSCs. TAP1 knockdown resulted in increased tumor growth of 4T1 cells in immunocompetent mice. Together, this suggests immune evasion mechanisms in breast CSCs are marker specific and epigenetic silencing of TAP1 in Aldefluor+ breast CSCs contributes to their enhanced survival under immune pressure. Stem Cells 2018;36:641-654.

    View details for DOI 10.1002/stem.2780

    View details for PubMedID 29341428

  • The NAD+ Salvage Pathway Supports PHGDH-Driven Serine Biosynthesis Cell Reports Murphy, J. P., Giacomantonio, M., Paulo, J. A., Everley, R. A., Kennedy, B. E., Pathak, G. P., Clements, D. R., Kim, Y., Dai, C., Sharif, T., Gygi, S. P., Gujar, S. 2018
  • Surfen, a proteoglycan binding agent, reduces inflammation but inhibits remyelination in murine models of Multiple Sclerosis. Acta neuropathologica communications Warford, J. R., Lamport, A. C., Clements, D. R., Malone, A., Kennedy, B. E., Kim, Y., Gujar, S. A., Hoskin, D. W., Easton, A. S. 2018; 6 (1): 4

    Abstract

    Proteoglycans are promising therapeutic targets in Multiple Sclerosis (MS), because they regulate many aspects of the immune response. This was studied using surfen, an agent that binds both heparan sulphate proteoglycans (HSPGs) and chondroitin sulphate proteoglycans (CSPGs). Initial cell culture work on bone marrow derived macrophages (BMDMs) found that surfen reduced concentrations of the chemokines CCL2, CCL4 and CCL5, with reduced messenger (m)RNA expression for Tumor Necrosis Factor, IL-6, IL-1β and inducible nitric oxide synthase. These data were further explored using Experimental Autoimmune Encephalomyelitis (EAE) in mice. Surfen reduced clinical signs during EAE when administered from disease onset, and reduced infiltration by CD4 positive T cells and macrophages into the central nervous system. These mice also showed reduced mRNA expression for the chemokines CCL3 and CCL5, with reduced concentrations of CCL2, CCL3 and CCL5. During EAE, surfen treatment induced a persistent increase in Interleukin (IL)-4 concentrations which may enhance T helper 2 responses. During EAE, surfen treatment reduced mRNA expression for HSPGs (NDST1, agrin, syndecan-4, perlecan, serglycin, syndecan-1) and the CSPG versican. By contrast, surfen increased mRNA expression for the CSPG aggrecan, with no effect on neurocan. During EAE, significant positive correlations were found between mRNA expression and clinical score for syndecan-4, serglycin and syndecan-1 and a significant negative correlation for aggrecan. These correlations were absent in surfen treated mice. Repair in the later stages of MS involves remyelination, which was modeled by injecting lysolecithin (lysophosphatidylcholine, LPC) into mouse corpus callosum to create regions of demyelination. When surfen was injected 2 days after LPC, it delayed remyelination of the lesions, but had no effect when injected 7 days after LPC. The delayed remyelination was associated with local increases in CSPG expression. Therefore surfen suppresses inflammation but inhibits remyelination in these models. A mechanism in common may be increased CSPG expression.

    View details for DOI 10.1186/s40478-017-0506-9

    View details for PubMedID 29301568

    View details for PubMedCentralID PMC5755315

  • MHC-I Ligand Discovery Using Targeted Database Searches of Mass Spectrometry Data: Implications for T-Cell Immunotherapies JOURNAL OF PROTEOME RESEARCH Murphy, J. P., Konda, P., Kowalewski, D. J., Schuster, H., Clements, D., Kim, Y., Cohen, A. M., Sharif, T., Nielsen, M., Stevanovic, S., Lee, P. W., Gujar, S. 2017; 16 (4): 1806-1816

    Abstract

    Class I major histocompatibility complex (MHC-I)-bound peptide ligands dictate the activation and specificity of CD8+ T cells and thus are important for devising T-cell immunotherapies. In recent times, advances in mass spectrometry (MS) have enabled the precise identification of these MHC-I peptides, wherein MS spectra are compared against a reference proteome. Unfortunately, matching these spectra to reference proteome databases is hindered by inflated search spaces attributed to a lack of enzyme restriction in the searches, limiting the efficiency with which MHC ligands are discovered. Here we offer a solution to this problem whereby we developed a targeted database search approach and accompanying tool SpectMHC, that is based on a priori-predicted MHC-I peptides. We first validated the approach using MS data from two different allotype-specific immunoprecipitates for the C57BL/6 mouse background. We then developed allotype-specific HLA databases to search previously published MS data sets of human peripheral blood mononuclear cells (PBMCs). This targeted search strategy improved peptide identifications for both mouse and human ligandomes by greater than 2-fold and is superior to traditional "no enzyme" searches of reference proteomes. Our targeted database search promises to uncover otherwise missed novel T-cell epitopes of therapeutic potential.

    View details for DOI 10.1021/acs.jproteome.6b00971

    View details for Web of Science ID 000398985700038

    View details for PubMedID 28244318

  • Autophagic homeostasis is required for the pluripotency of cancer stem cells AUTOPHAGY Sharif, T., Martell, E., Dai, C., Kennedy, B. E., Murphy, P., Clements, D. R., Kim, Y., Lee, P. W., Gujar, S. A. 2017; 13 (2): 264-284

    Abstract

    Pluripotency is an important feature of cancer stem cells (CSCs) that contributes to self-renewal and chemoresistance. The maintenance of pluripotency of CSCs under various pathophysiological conditions requires a complex interaction between various cellular pathways including those involved in homeostasis and energy metabolism. However, the exact mechanisms that maintain the CSC pluripotency remain poorly understood. In this report, using both human and murine models of CSCs, we demonstrate that basal levels of autophagy are required to maintain the pluripotency of CSCs, and that this process is differentially regulated by the rate-limiting enzyme in the NAD+ synthesis pathway NAMPT (nicotinamide phosphoribosyltransferase) and the transcription factor POU5F1/OCT4 (POU class 5 homeobox 1). First, our data show that the pharmacological inhibition and knockdown (KD) of NAMPT or the KD of POU5F1 in human CSCs significantly decreased the expression of pluripotency markers POU5F1, NANOG (Nanog homeobox) and SOX2 (SRY-box 2), and upregulated the differentiation markers TUBB3 (tubulin β 3 class III), CSN2 (casein β), SPP1 (secreted phosphoprotein 1), GATA6 (GATA binding protein 6), T (T brachyury transcription factor) and CDX2 (caudal type homeobox 2). Interestingly, these pluripotency-regulating effects of NAMPT and POU5F1 were accompanied by contrasting levels of autophagy, wherein NAMPT KD promoted while POU5F1 KD inhibited the autophagy machinery. Most importantly, any deviation from the basal level of autophagy, either increase (via rapamycin, serum starvation or Tat-beclin 1 [Tat-BECN1] peptide) or decrease (via ATG7 or ATG12 KD), strongly decreased the pluripotency and promoted the differentiation and/or senescence of CSCs. Collectively, these results uncover the link between the NAD+ biosynthesis pathway, CSC transcription factor POU5F1 and pluripotency, and further identify autophagy as a novel regulator of pluripotency of CSCs.

    View details for DOI 10.1080/15548627.2016.1260808

    View details for Web of Science ID 000395125200005

    View details for PubMedID 27929731

    View details for PubMedCentralID PMC5324853

  • Breast cancer subtype dictates DNA methylation and ALDH1A3-mediated expression of tumor suppressor RARRES1 ONCOTARGET Coyle, K. M., Murphy, J. P., Vidovic, D., Vaghar-Kashani, A., Dean, C. A., Sultan, M., Clements, D., Wallace, M., Thomas, M. L., Hundert, A., Giacomantonio, C. A., Helyer, L., Gujar, S. A., Lee, P. W., Weaver, I. C., Marcato, P. 2016; 7 (28): 44096-44112

    Abstract

    Breast cancer subtyping, based on the expression of hormone receptors and other genes, can determine patient prognosis and potential options for targeted therapy. Among breast cancer subtypes, tumors of basal-like and claudin-low subtypes are typically associated with worse patient outcomes, are primarily classified as triple-negative breast cancers (TNBC), and cannot be treated with existing hormone-receptor-targeted therapies. Understanding the molecular basis of these subtypes will lead to the development of more effective treatment options for TNBC. In this study, we focus on retinoic acid receptor responder 1 (RARRES1) as a paradigm to determine if breast cancer subtype dictates protein function and gene expression regulation. Patient tumor dataset analysis and gene expression studies of a 26 cell-line panel, representing the five breast cancer subtypes, demonstrate that RARRES1 expression is greatest in basal-like TNBCs. Cell proliferation and tumor growth assays reveal that RARRES1 is a tumor suppressor in TNBC. Furthermore, gene expression studies, Illumina HumanMethylation450 arrays, and chromatin immunoprecipitation demonstrate that expression of RARRES1 is retained in basal-like breast cancers due to hypomethylation of the promoter. Additionally, expression of the cancer stem cell marker, aldehyde dehydrogenase 1A3, which provides the required ligand (retinoic acid) for RARRES1 transcription, is also specific to the basal-like subtype. We functionally demonstrate that the combination of promoter methylation and retinoic acid signaling dictates expression of tumor suppressor RARRES1 in a subtype-specific manner. These findings provide a precedent for a therapeutically-inducible tumor suppressor and suggest novel avenues of therapeutic intervention for patients with basal-like breast cancer.

    View details for DOI 10.18632/oncotarget.9858

    View details for Web of Science ID 000385395700092

    View details for PubMedID 27286452

    View details for PubMedCentralID PMC5190082

  • The NAD(+) salvage pathway modulates cancer cell viability via p73 CELL DEATH AND DIFFERENTIATION Sharif, T., Ahn, D., Liu, R., Pringle, E., Martell, E., Dai, C., NUNOKAWA, A., Kwak, M., CLEMENTS, D., Murphy, J. P., Dean, C., Marcato, P., McCormick, C., Godbout, R., Gujar, S. A., Lee, P. W. 2016; 23 (4): 669-680

    Abstract

    The involvement of the nicotinamide adenine dinucleotide (NAD(+)) salvage pathway in cancer cell survival is poorly understood. Here we show that the NAD(+) salvage pathway modulates cancer cell survival through the rarely mutated tumour suppressor p73. Our data show that pharmacological inhibition or knockdown of nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in the NAD(+) salvage pathway, enhances autophagy and decreases survival of cancer cells in a p53-independent manner. Such NAMPT inhibition stabilizes p73 independently of p53 through increased acetylation and decreased ubiquitination, resulting in enhanced autophagy and cell death. These effects of NAMPT inhibition can be effectively reversed using nicotinamide mononucleotide (NMN), the enzymatic product of NAMPT. Similarly, knockdown of p73 also decreases NAMPT inhibition-induced autophagy and cell death, whereas overexpression of p73 alone enhances these effects. We show that the breast cancer cell lines (MCF-7, MDA-MB-231 and MDA-MB-468) harbour significantly higher levels of NAMPT and lower levels of p73 than does the normal cell line (MCF-10A), and that NAMPT inhibition is cytotoxic exclusively to the cancer cells. Furthermore, data from 176 breast cancer patients demonstrate that higher levels of NAMPT and lower levels of p73 correlate with poorer patient survival, and that high-grade tumours have significantly higher NAMPT/p73 mRNA ratios. Therefore, the inverse relationship between NAMPT and p73 demonstrable in vitro is also reflected from the clinical data. Taken together, our studies reveal a new NAMPT-p73 nexus that likely has important implications for cancer diagnosis, prognosis and treatment.

    View details for DOI 10.1038/cdd.2015.134

    View details for Web of Science ID 000374126800012

    View details for PubMedID 26586573

    View details for PubMedCentralID PMC4986639

  • Aldehyde dehydrogenase 1A3 influences breast cancer progression via differential retinoic acid signaling. Molecular oncology Marcato, P., Dean, C. A., Liu, R., Coyle, K. M., Bydoun, M., Wallace, M., Clements, D., Turner, C., Mathenge, E. G., Gujar, S. A., Giacomantonio, C. A., Mackey, J. R., Godbout, R., Lee, P. W. 2015; 9 (1): 17-31

    Abstract

    Aldehyde dehydrogenase (ALDH) 1A enzymes produce retinoic acid (RA), a transcription induction molecule. To investigate if ALDH1A1 or ALDH1A3-mediated RA signaling has an active role in breast cancer tumorigenesis, we performed gene expression and tumor xenograft studies. Analysis of breast patient tumors revealed that high levels of ALDH1A3 correlated with expression of RA-inducible genes with retinoic acid response elements (RAREs), poorer patient survival and triple-negative breast cancers. This suggests a potential link between ALDH1A3 expression and RA signaling especially in aggressive and/or triple-negative breast cancers. In MDA-MB-231, MDA-MB-468 and MDA-MB-435 cells, ALDH1A3 and RA increased expression of RA-inducible genes. Interestingly, ALDH1A3 had opposing effects in tumor xenografts, increasing tumor growth and metastasis of MDA-MB-231 and MDA-MB-435 cells, but decreasing tumor growth of MDA-MB-468 cells. Exogenous RA replaced ALDH1A3 in inducing the same opposing tumor growth and metastasis effects, suggesting that ALDH1A3 mediates these effects by promoting RA signaling. Genome expression analysis revealed that ALDH1A3 induced largely divergent gene expression in MDA-MB-231 and MDA-MB-468 cells which likely resulted in the opposing tumor growth effects. Treatment with DNA methylation inhibitor 5-aza-2'deoxycytidine restored uniform RA-inducibility of RARE-containing HOXA1 and MUC4 in MDA-MB-231 and MDA-MB-468 cells, suggesting that differences in epigenetic modifications contribute to differential ALDH1A3/RA-induced gene expression in breast cancer. In summary, ALDH1A3 induces differential RA signaling in breast cancer cells which affects the rate of breast cancer progression.

    View details for DOI 10.1016/j.molonc.2014.07.010

    View details for PubMedID 25106087

    View details for PubMedCentralID PMC5528683

  • Core Needle Biopsy of Breast Cancer Tumors Increases Distant Metastases in a Mouse Model NEOPLASIA Mathenge, E. G., Dean, C. A., Clements, D., Vaghar-Kashani, A., Photopoulos, S., Coyle, K. M., Giacomantonio, M., Malueth, B., Nunokawa, A., Jordan, J., Lewis, J. D., Gujar, S. A., Marcato, P., Lee, P. W., Giacomantonio, C. A. 2014; 16 (11): 950-960

    Abstract

    Incisional biopsies, including the diagnostic core needle biopsy (CNB), routinely performed before surgical excision of breast cancer tumors are hypothesized to increase the risk of metastatic disease. In this study, we experimentally determined whether CNB of breast cancer tumors results in increased distant metastases and examine important resultant changes in the primary tumor and tumor microenvironment associated with this outcome.To evaluate the effect of CNB on metastasis development, we implanted murine mammary 4T1 tumor cells in BALB/c mice and performed CNB on palpable tumors in half the mice. Subsequently, emulating the human scenario, all mice underwent complete tumor excision and were allowed to recover, with attendant metastasis development. Tumor growth, lung metastasis, circulating tumor cell (CTC) levels, variation in gene expression, composition of the tumor microenvironment, and changes in immunologic markers were compared in biopsied and non-biopsied mice.Mice with biopsied tumors developed significantly more lung metastases compared to non-biopsied mice. Tumors from biopsied mice contained a higher frequency of myeloid-derived suppressor cells (MDSCs) accompanied by reduced CD4 + T cells, CD8 + T cells, and macrophages, suggesting biopsy-mediated development of an increasingly immunosuppressive tumor microenvironment. We also observed a CNB-dependent up-regulation in the expression of SOX4, Ezh2, and other key epithelial-mesenchymal transition (EMT) genes, as well as increased CTC levels among the biopsy group.CNB creates an immunosuppressive tumor microenvironment, increases EMT, and facilitates release of CTCs, all of which likely contribute to the observed increase in development of distant metastases.

    View details for DOI 10.1016/j.neo.2014.09.004

    View details for Web of Science ID 000345516900007

    View details for PubMedID 25425969

    View details for PubMedCentralID PMC4240917

  • The NAD(+) synthesizing enzyme nicotinamide mononucleotide adenylyltransferase 2 (NMNAT-2) is a p53 downstream target CELL CYCLE Pan, L., Ahn, D., Sharif, T., Clements, D., Gujar, S. A., Lee, P. W. 2014; 13 (6): 1041-1048

    Abstract

    NAD(+) metabolism plays key roles not only in energy production but also in diverse cellular physiology. Aberrant NAD(+) metabolism is considered a hallmark of cancer. Recently, the tumor suppressor p53, a major player in cancer signaling pathways, has been implicated as an important regulator of cellular metabolism. This notion led us to examine whether p53 can regulate NAD(+) biosynthesis in the cell. Our search resulted in the identification of nicotinamide mononucleotide adenylyltransferase 2 (NMNAT-2), a NAD(+) synthetase, as a novel downstream target gene of p53. We show that NMNAT-2 expression is induced upon DNA damage in a p53-dependent manner. Two putative p53 binding sites were identified within the human NMNAT-2 gene, and both were found to be functional in a p53-dependent manner. Furthermore, knockdown of NMNAT-2 significantly reduces cellular NAD(+) levels and protects cells from p53-dependent cell death upon DNA damage, suggesting an important functional role of NMNAT-2 in p53-mediated signaling. Our demonstration that p53 modulates cellular NAD(+) synthesis is congruent with p53's emerging role as a key regulator of metabolism and related cell fate.

    View details for DOI 10.4161/cc.28128

    View details for Web of Science ID 000336659200024

    View details for PubMedID 24552824

    View details for PubMedCentralID PMC3984302

  • Gemcitabine-mediated tumour regression and p53-dependent gene expression: implications for colon and pancreatic cancer therapy CELL DEATH & DISEASE Hill, R., Rabb, M., Madureira, P. A., CLEMENTS, D., Gujar, S. A., Waisman, D. M., Giacomantonio, C. A., Lee, P. W. 2013; 4

    Abstract

    Gemcitabine is a chemotherapeutic that is widely used for the treatment of a variety of haematological malignancies and has become the standard chemotherapy for the treatment of advanced pancreatic cancer. Combinational gemcitabine regimes (e.g.with doxorubicin) are being tested in clinical trials to treat a variety of cancers, including colon cancer. The limited success of these trials has prompted us to pursue a better understanding of gemcitabine's mechanism of cell killing, which could dramatically improve the therapeutic potential of this agent. For comparison, we included gamma irradiation that triggers robust cell cycle arrest and Cr(VI), which is a highly toxic chemical that induces a robust p53-dependent apoptotic response. Gemcitabine induced a potent p53-dependent apoptosis that correlated with the accumulation of pro-apoptotic proteins such as PUMA and Bax. This is accompanied by a drastic reduction in p2l and 14-3-3σ protein levels, thereby significantly sensitizing the cells to apoptosis. In vitro and in vivo studies demonstrated that gemcitabine required PUMA transcription to instigate an apoptotic programme. This was in contrast to Cr(VI)-induced apoptosis that required Bax and was independent of transcription. An examination of clinical colon and pancreatic cancer tissues shows higher p53, p21, 14-3-3σ and Bax expression compared with matched normal tissues, yet there is a near absence of PUMA protein. This may explain why gemcitabine shows only limited efficacy in the treatment of these cancers. Our results raise the possibility that targeting the Bax-dependent cell death pathway, rather than the PUMA pathway, could result in significantly improved patient outcome and prognosis for these cancers.

    View details for DOI 10.1038/cddis.2013.307

    View details for Web of Science ID 000325370300008

    View details for PubMedID 24008735

    View details for PubMedCentralID PMC3789167

  • Multifaceted Therapeutic Targeting of Ovarian Peritoneal Carcinomatosis Through Virus-induced Immunomodulation MOLECULAR THERAPY Gujar, S., Dielschneider, R., Clements, D., Helson, E., Shmulevitz, M., Marcato, P., Pan, D., Pan, L., Ahn, D., Alawadhi, A., Lee, P. W. 2013; 21 (2): 338-347

    Abstract

    Immunosuppression associated with ovarian cancer (OC) and resultant peritoneal carcinomatosis (PC) hampers the efficacy of many promising treatment options, including immunotherapies. It is hypothesized that oncolytic virus-based therapies can simultaneously kill OC and mitigate immunosuppression. Currently, reovirus-based anticancer therapy is undergoing phase I/II clinical trials for the treatment of OC. Hence, this study was focused on characterizing the effects of reovirus therapy on OC and associated immune microenvironment. Our data shows that reovirus efficiently killed OC cells and induced higher expression of the molecules involved in antigen presentation including major histocompatibility complex (MHC) class I, β2-microglobulin (β2M), TAP-1, and TAP-2. In addition, in the presence of reovirus, dendritic cells (DCs) overcame the OC-mediated phenotypic suppression and successfully stimulated tumor-specific CD8+ T cells. In animal studies, reovirus targeted local and distal OC, alleviated the severity of PC and significantly prolonged survival. These therapeutic effects were accompanied by decreased frequency of suppressive cells, e.g., Gr1.1+, CD11b+ myeloid derived suppressor cells (MDSCs), and CD4+, CD25+, FOXP3+ Tregs, tumor-infiltration of CD3+ cells and higher expression of Th1 cytokines. Finally, reovirus therapy during early stages of OC also resulted in the postponement of PC development. This report elucidates timely information on a therapeutic approach that can target OC through clinically desired multifaceted mechanisms to better the outcomes.

    View details for DOI 10.1038/mt.2012.228

    View details for Web of Science ID 000314434600011

    View details for PubMedID 23299799

    View details for PubMedCentralID PMC3594021