Publications by authors named "Nancy D Ebelt"

16 Publications

  • Page 1 of 1

-Based Therapy Targeting Indoleamine 2,3-Dioxygenase Restructures the Immune Contexture to Improve Checkpoint Blockade Efficacy.

Biomedicines 2020 Dec 16;8(12). Epub 2020 Dec 16.

Department of Immuno-Oncology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.

Therapeutic options for non-small cell lung cancer (NSCLC) treatment have changed dramatically in recent years with the advent of novel immunotherapeutic approaches. Among these, immune checkpoint blockade (ICB) using monoclonal antibodies has shown tremendous promise in approximately 20% of patients. In order to better predict patients that will respond to ICB treatment, biomarkers such as tumor-associated CD8 T cell frequency, tumor checkpoint protein status and mutational burden have been utilized, however, with mixed success. In this study, we hypothesized that significantly altering the suppressive tumor immune landscape in NSCLC could potentially improve ICB efficacy. Using sub-therapeutic doses of our -based therapy targeting the suppressive molecule indoleamine 2,3-dioxygenase (shIDO-ST) in tumor-bearing mice, we observed dramatic changes in immune subset phenotypes that included increases in antigen presentation markers, decreased regulatory T cell frequency and overall reduced checkpoint protein expression. Combination shIDO-ST treatment with anti-PD-1/CTLA-4 antibodies enhanced tumor growth control, compared to either treatment alone, which was associated with significant intratumoral infiltration by CD8 and CD4 T cells. Ultimately, we show that increases in antigen presentation markers and infiltration by T cells is correlated with significantly increased survival in NSCLC patients. These results suggest that the success of ICB therapy may be more accurately predicted by taking into account multiple factors such as potential for antigen presentation and immune subset repertoire in addition to markers already being considered. Alternatively, combination treatment with agents such as shIDO-ST could be used to create a more conducive tumor microenvironment for improving responses to ICB.
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http://dx.doi.org/10.3390/biomedicines8120617DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7765568PMC
December 2020

Development of a multi-antigenic SARS-CoV-2 vaccine candidate using a synthetic poxvirus platform.

Nat Commun 2020 11 30;11(1):6121. Epub 2020 Nov 30.

Department of Hematology and Transplant Center, City of Hope National Medical Center, Duarte, CA, 91010, USA.

Modified Vaccinia Ankara (MVA) is a highly attenuated poxvirus vector that is widely used to develop vaccines for infectious diseases and cancer. We demonstrate the construction of a vaccine platform based on a unique three-plasmid system to efficiently generate recombinant MVA vectors from chemically synthesized DNA. In response to the ongoing global pandemic caused by SARS coronavirus-2 (SARS-CoV-2), we use this vaccine platform to rapidly produce fully synthetic MVA (sMVA) vectors co-expressing SARS-CoV-2 spike and nucleocapsid antigens, two immunodominant antigens implicated in protective immunity. We show that mice immunized with these sMVA vectors develop robust SARS-CoV-2 antigen-specific humoral and cellular immune responses, including potent neutralizing antibodies. These results demonstrate the potential of a vaccine platform based on synthetic DNA to efficiently generate recombinant MVA vectors and to rapidly develop a multi-antigenic poxvirus-based SARS-CoV-2 vaccine candidate.
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http://dx.doi.org/10.1038/s41467-020-19819-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7705736PMC
November 2020

Targeting desmoplasia in pancreatic cancer as an essential first step to effective therapy.

Oncotarget 2020 Sep 22;11(38):3486-3488. Epub 2020 Sep 22.

Department of Immuno-Oncology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.

Pancreatic cancer is considered one of the most lethal cancers in the US. It contributes to an estimated 47,000 deaths annually and is predicted to surpass prostate, breast and colorectal cancers as the leading cause of cancer-related death. Although major advancements in cancer treatment have improved outcomes for many cancer types, survival rate for pancreatic cancer has not improved in nearly four decades despite tremendous effort. One attribute of pancreatic cancer that is considered a major barrier to effective treatment is the formation of fibrotic tissue around tumor cells known as desmoplasia. A number of promising approaches have been developed to deplete fibrotic components in pancreatic tumors to enhance drug delivery, some of which have been tested in clinical trials of advanced, unresectable pancreatic cancer. Here, we discuss previous efforts, shortcomings and new considerations for developing more effective agents to eliminate desmoplasia.
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http://dx.doi.org/10.18632/oncotarget.27745DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7517960PMC
September 2020

Development of a Synthetic Poxvirus-Based SARS-CoV-2 Vaccine.

bioRxiv 2020 Jul 2. Epub 2020 Jul 2.

Department of Hematology and Transplant Center, City of Hope National Medical Center, Duarte CA 91010, USA.

Modified Vaccinia Ankara (MVA) is a highly attenuated poxvirus vector that is widely used to develop vaccines for infectious diseases and cancer. We developed a novel vaccine platform based on a unique three-plasmid system to efficiently generate recombinant MVA vectors from chemically synthesized DNA. In response to the ongoing global pandemic caused by SARS coronavirus-2 (SARS-CoV-2), we used this novel vaccine platform to rapidly produce fully synthetic MVA (sMVA) vectors co-expressing SARS-CoV-2 spike and nucleocapsid antigens, two immunodominant antigens implicated in protective immunity. Mice immunized with these sMVA vectors developed robust SARS-CoV-2 antigen-specific humoral and cellular immune responses, including potent neutralizing antibodies. These results demonstrate the potential of a novel vaccine platform based on synthetic DNA to efficiently generate recombinant MVA vectors and to rapidly develop a multi-antigenic poxvirus-based SARS-CoV-2 vaccine candidate.
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http://dx.doi.org/10.1101/2020.07.01.183236DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7337387PMC
July 2020

5-Azacytidine Potentiates Anti-tumor Immunity in a Model of Pancreatic Ductal Adenocarcinoma.

Front Immunol 2020 31;11:538. Epub 2020 Mar 31.

Department of Immuno-Oncology, Beckman Research Institute, City of Hope, Duarte, CA, United States.

Tumors evolve a variety of mechanisms to escape immune detection while expressing tumor-promoting molecules that can be immunogenic. Here, we show that transposable elements (TE) and gene encoded, tumor-associated antigens (TAA), which can be both highly immunogenic and tumor-promoting, are significantly upregulated during the transition from pre-malignancy to malignancy in an inducible model of pancreatic ductal adenocarcinoma (PDAC). Coincident with the increased presence of TEs and TAAs was the downregulation of gene transcripts associated with antigen presentation, T cell recruitment and intrinsic anti-viral responses, suggesting a unique strategy employed by PDAC to possibly augment tumorigenesis while escaping detection by the immune system. treatment of mouse and human PDAC cell lines with the DNA methyltransferase inhibitor 5-azacytidine (Aza) resulted in augmented expression of transcripts for antigen presentation machinery and T cell chemokines. When immunocompetent mice implanted with PDAC were therapeutically treated with Aza, we observed significant tumor regression that was not observed in immunocompromised mice, implicating anti-tumor immunity as the principal mechanism of tumor growth control. Analysis of PDAC tumors, immediately following Aza treatment in immunocompetent mice, revealed a significantly greater infiltration of T cells and various innate immune subsets compared to control treatment, suggesting that Aza treatment enhances tumor immunogenicity. Thus, augmenting antigen presentation and T cell chemokine expression using DNA methyltransferase inhibitors could be leveraged to potentiate adaptive anti-tumor immune responses against PDAC.
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http://dx.doi.org/10.3389/fimmu.2020.00538DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7136411PMC
March 2020

Modulating multi-functional ERK complexes by covalent targeting of a recruitment site in vivo.

Nat Commun 2019 11 19;10(1):5232. Epub 2019 Nov 19.

Division of Chemical Biology and Medicinal Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA.

Recently, the targeting of ERK with ATP-competitive inhibitors has emerged as a potential clinical strategy to overcome acquired resistance to BRAF and MEK inhibitor combination therapies. In this study, we investigate an alternative strategy of targeting the D-recruitment site (DRS) of ERK. The DRS is a conserved region that lies distal to the active site and mediates ERK-protein interactions. We demonstrate that the small molecule BI-78D3 binds to the DRS of ERK2 and forms a covalent adduct with a conserved cysteine residue (C159) within the pocket and disrupts signaling in vivo. BI-78D3 does not covalently modify p38MAPK, JNK or ERK5. BI-78D3 promotes apoptosis in BRAF inhibitor-naive and resistant melanoma cells containing a BRAF V600E mutation. These studies provide the basis for designing modulators of protein-protein interactions involving ERK, with the potential to impact ERK signaling dynamics and to induce cell cycle arrest and apoptosis in ERK-dependent cancers.
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http://dx.doi.org/10.1038/s41467-019-12996-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6863825PMC
November 2019

Hyaluronidase-Expressing Effectively Targets Tumor-Associated Hyaluronic Acid in Pancreatic Ductal Adenocarcinoma.

Mol Cancer Ther 2020 02 6;19(2):706-716. Epub 2019 Nov 6.

Department of Immuno-Oncology, Beckman Research Institute of the City of Hope, Duarte, California.

In pancreatic ductal adenocarcinoma (PDAC), the extracellular matrix (ECM) surrounding cancer cells forms a barrier that often limits the ability of chemotherapeutic drugs and cytotoxic immune subsets to penetrate and eliminate tumors. The dense stromal matrix protecting cancer cells, also known as desmoplasia, results from the overproduction of major ECM components such as collagens and hyaluronic acid (HA). Although candidate drugs targeting ECM components have shown promise in increasing penetration of chemotherapeutic agents, severe adverse effects associated with systemic depletion of ECM in peripheral healthy tissues limits their use at higher, more effective doses. Currently, few strategies exist that preferentially degrade ECM in tumor tissue over healthy tissues. In light of this, we have developed an attenuated, tumor-targeting (ST) expressing functional bacterial hyaluronidase (bHs-ST), capable of degrading human HA deposited within PDAC tumors. Our data show that bHs-ST (i) targets and colonizes orthotopic human PDAC tumors following systemic administration and (ii) is efficiently induced to deplete tumor-derived HA, which in turn (iii) significantly increases diffusion of within desmoplastic tumors. BHs-ST represents a promising new tumor ECM-targeting strategy that may be instrumental in minimizing off-tumor toxicity while maximizing drug delivery into highly desmoplastic tumors.
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http://dx.doi.org/10.1158/1535-7163.MCT-19-0556DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007852PMC
February 2020

Unraveling the crosstalk between melanoma and immune cells in the tumor microenvironment.

Semin Cancer Biol 2019 12 9;59:236-250. Epub 2019 Aug 9.

Department of Immuno-Oncology, Beckman Research Institute of City of Hope, Duarte, California, USA. Electronic address:

Cutaneous melanoma is the most common skin cancer with an incidence that has been rapidly increasing in the past decades. Melanomas are among the most immunogenic tumors and, as such, have the greatest potential to respond favorably to immunotherapy. However, like many cancers, melanomas acquire various suppressive mechanisms, which generally act in concert, to escape innate and adaptive immune detection and destruction. Intense research into the cellular and molecular events associated with melanomagenesis, which ultimately lead to immune suppression, has resulted in the discovery of new therapeutic targets and synergistic combinations of immunotherapy, targeted therapy and chemotherapy. Tremendous effort to determine efficacy of single and combination therapies in pre-clinical and clinical phase I-III trials has led to FDA-approval of several immunotherapeutic agents that could potentially be beneficial for aggressive, highly refractory, advanced and metastatic melanomas. The increasing availability of approved combination therapies for melanoma and more rapid assessment of patient tumors has increased the feasibility of personalized treatment to overcome patient and tumor heterogeneity and to achieve greater clinical benefit. Here, we review the evolution of the immune system during melanomagenesis, mechanisms exploited by melanoma to suppress anti-tumor immunity and methods that have been developed to restore immunity. We emphasize that an effective therapeutic strategy will require coordinate activation of tumor-specific immunity as well as increased recognition and accessibility of melanoma cells in primary tumors and distal metastases. This review integrates available knowledge on melanoma-specific immunity, molecular signaling pathways and molecular targeting strategies that could be utilized to envision therapeutics with broader application and greater efficacy for early stage and advanced metastatic melanoma.
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http://dx.doi.org/10.1016/j.semcancer.2019.08.002DOI Listing
December 2019

A c-Jun N-terminal kinase inhibitor, JNK-IN-8, sensitizes triple negative breast cancer cells to lapatinib.

Oncotarget 2017 Dec 24;8(62):104894-104912. Epub 2017 Aug 24.

Institute of Cellular & Molecular Biology, University of Texas at Austin, Dell Pediatric Research Institute, Austin, TX 78723, USA.

Triple negative breast cancers (TNBC) have poor prognosis compared to other breast cancer subtypes and represent 15-20% of breast cancers diagnosed. Unique targets and new molecularly-targeted therapies are urgently needed for this subtype. Despite high expression of Epidermal Growth Factor Receptor, inhibitors such as lapatinib have not shown therapeutic efficacy in TNBC patients. Herein, we report that treatment with the covalent JNK inhibitor, JNK-IN-8, synergizes with lapatinib to cause cell death, while these compounds as single agents have little effect. The combination significantly increases survival of mice bearing xenografts of MDA-MB-231 human TNBC cells. Our studies demonstrate that lapatinib treatment increases c-Jun and JNK phosphorylation indicating a mechanism of resistance. Combined, these compounds significantly reduce transcriptional activity of Nuclear Factor kappa B, Activating Protein 1, and Nuclear factor erythroid 2-Related Factor 2. As master regulators of antioxidant response, their decreased activity induces a 10-fold increase in reactive oxygen species that is cytotoxic, and is rescued by addition of exogenous antioxidants. Over expression of p65 or Nrf2 also significantly rescues viability during JNK-IN-8 and lapatinib treatment. Further studies combining JNK-IN-8 and lapatinib may reveal a benefit for patients with TNBC, fulfilling a critical medical need.
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http://dx.doi.org/10.18632/oncotarget.20581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5739608PMC
December 2017

Serotonin Analogues as Inhibitors of Breast Cancer Cell Growth.

ACS Med Chem Lett 2017 Oct 14;8(10):1072-1076. Epub 2017 Sep 14.

Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States.

Serotonin (5-hydroxytryptamine, 5-HT) is a critical local regulator of epithelial homeostasis in the breast and exerts its actions through a number of receptors. Dysregulation of serotonin signaling is reported to contribute to breast cancer pathophysiology by enhancing cell proliferation and promoting resistance to apoptosis. Preliminary analyses indicated that the potent 5-HT1B/1D serotonin receptor agonist 5-nonyloxytryptamine (5-NT), a triptan-like molecule, induced cell death in breast cancer cell lines. Thus, we synthesized a series of novel alkyloxytryptamine analogues, several of which decreased the viability of various human cancer cell lines. Proteomic and metabolomic analyses showed that compounds and induced apoptosis and interfered with signaling pathways that regulate protein translation and survival, such as the Akt/mTOR pathway, in triple-negative breast cancer cells.
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http://dx.doi.org/10.1021/acsmedchemlett.7b00282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5641961PMC
October 2017

Utilizing Salmonella to treat solid malignancies.

J Surg Oncol 2017 Jul 18;116(1):75-82. Epub 2017 Apr 18.

Department of Experimental Therapeutics, Beckman Research Institute of City of Hope, Duarte, California.

Despite intensive research into novel treatment strategies for cancer, it remains the second most common cause of death in industrialized populations. Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with dismal prognosis. Currently, surgical resection offers the best chance for extended survival, yet recurrence remains high and is associated with poor outcome. Systemic treatment has evolved from non-specific, cytotoxic chemotherapy to the use of cancer-targeting agents, profoundly changing treatment approaches in the metastatic and adjuvant settings. One promising approach, highlighted in this review, uses the inherent capacity of Salmonella to colonize and eliminate solid tumors.
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http://dx.doi.org/10.1002/jso.24644DOI Listing
July 2017

Extracellular Matrix Stiffening Induces a Malignant Phenotypic Transition in Breast Epithelial Cells.

Cell Mol Bioeng 2017 Feb 19;10(1):114-123. Epub 2016 Oct 19.

1Department of Biomedical Engineering, The University of Texas at Austin, Austin, USA.

Tumors are much stiffer than healthy tissue, and progressively stiffen as the cancer develops. Tumor stiffening is largely the result of extracellular matrix (ECM) remodeling, for example, deposition and crosslinking of collagen I. Well established models have demonstrated the influence of the microenvironment in regulating tissue homeostasis, with matrix stiffness being a particularly influential mediator. Non-malignant MCF10A mammary epithelial cells (MECs) lose their epithelial characteristics and become invasive when cultured in stiff microenvironments, leading to the hypothesis that tumor stiffening could contribute directly to disease progression. However, previous studies demonstrating MCF10A invasion have been performed in gels with constant mechanical properties, unlike the dynamically stiffening tumor microenvironment. Here, we employ a temporally stiffening hydrogel platform to demonstrate that matrix stiffening induces invasion from and proliferation in MCF10A mammary acini. After allowing MCF10A acini to form in soft hydrogels for 14 days, the gels were stiffened to the level of a malignant tumor, giving rise to a proliferative and invasive phenotype. Cells were observed to collectively migrate away from mammary acini while maintaining cell-cell contacts. Small molecule inhibition of PI3K and Rac1 pathways was sufficient to significantly reduce the number and size of invasive acini after stiffening. Our results demonstrate that temporal matrix stiffening can induce invasion from mammary acini and supports the notion that tumor stiffening could be implicated in disease progression and metastasis.
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http://dx.doi.org/10.1007/s12195-016-0468-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6816676PMC
February 2017

ATM regulation of IL-8 links oxidative stress to cancer cell migration and invasion.

Elife 2015 Jun 1;4. Epub 2015 Jun 1.

Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, United States.

Ataxia-telangiectasia mutated (ATM) protein kinase regulates the DNA damage response (DDR) and is associated with cancer suppression. Here we report a cancer-promoting role for ATM. ATM depletion in metastatic cancer cells reduced cell migration and invasion. Transcription analyses identified a gene network, including the chemokine IL-8, regulated by ATM. IL-8 expression required ATM and was regulated by oxidative stress. IL-8 was validated as an ATM target by its ability to rescue cell migration and invasion defects in ATM-depleted cells. Finally, ATM-depletion in human breast cancer cells reduced lung tumors in a mouse xenograft model and clinical data validated IL-8 in lung metastasis. These findings provide insights into how ATM activation by oxidative stress regulates IL-8 to sustain cell migration and invasion in cancer cells to promote metastatic potential. Thus, in addition to well-established roles in tumor suppression, these findings identify a role for ATM in tumor progression.
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http://dx.doi.org/10.7554/eLife.07270DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4463759PMC
June 2015

c-Jun N-terminal kinase 2 prevents luminal cell commitment in normal mammary glands and tumors by inhibiting p53/Notch1 and breast cancer gene 1 expression.

Oncotarget 2015 May;6(14):11863-81

Institute of Cellular & Molecular Biology, College of Pharmacy, University of Texas at Austin, Dell Pediatric Research Institute, Austin, TX 78723, USA.

Breast cancer is a heterogeneous disease with several subtypes carrying unique prognoses. Patients with differentiated luminal tumors experience better outcomes, while effective treatments are unavailable for poorly differentiated tumors, including the basal-like subtype. Mechanisms governing mammary tumor subtype generation could prove critical to developing better treatments. C-Jun N-terminal kinase 2 (JNK2) is important in mammary tumorigenesis and tumor progression. Using a variety of mouse models, human breast cancer cell lines and tumor expression data, studies herein support that JNK2 inhibits cell differentiation in normal and cancer-derived mammary cells. JNK2 prevents precocious pubertal mammary development and inhibits Notch-dependent expansion of luminal cell populations. Likewise, JNK2 suppresses luminal populations in a p53-competent Polyoma Middle T-antigen tumor model where jnk2 knockout causes p53-dependent upregulation of Notch1 transcription. In a p53 knockout model, JNK2 restricts luminal populations independently of Notch1, by suppressing Brca1 expression and promoting epithelial to mesenchymal transition. JNK2 also inhibits estrogen receptor (ER) expression and confers resistance to fulvestrant, an ER inhibitor, while stimulating tumor progression. These data suggest that therapies inhibiting JNK2 in breast cancer may promote tumor differentiation, improve endocrine therapy response, and inhibit metastasis.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4494910PMC
http://dx.doi.org/10.18632/oncotarget.3787DOI Listing
May 2015

c-Jun N-Terminal Kinases Mediate a Wide Range of Targets in the Metastatic Cascade.

Genes Cancer 2013 Sep;4(9-10):378-87

Institute of Cellular & Molecular Biology, The University of Texas at Austin, Austin, TX, USA ; Division of Pharmacology & Toxicology, Dell Pediatric Research Institute, College of Pharmacy, The University of Texas at Austin, Austin, TX, USA.

Disseminated cancer cells rely on intricate interactions among diverse cell types in the tumor-associated stroma, vasculature, and immune system for survival and growth. Ubiquitous expression of c-Jun N-terminal kinase (jnk) genes in various cell types permits their control of metastasis. In early stages of metastasis, JNKs affect tumor-associated inflammation and angiogenesis as well as tumor cell migration and intravasation. Within the tumor stroma, JNKs are essential for the release of growth factors that promote epithelial-to-mesenchymal transition (EMT) in tumor cells. JNK3, the least ubiquitous isoform, facilitates angiogenesis by increasing endothelial cell migration. Importantly, JNK expression in tumor cells integrates stromal signals to promote tumor cell invasion. However, JNK isoforms differentially regulate migration toward the endothelial barrier. Once tumor cells enter the bloodstream, JNKs increase circulating tumor cell (CTC) survival and homing to tissues. By promoting fibrosis, JNKs improve CTC attachment to the endothelium. Once anchored, JNKs stimulate EMT to facilitate tumor cell extravasation and enhance the secretion of endothelial barrier disrupters. Tumor cells attract barrier-disrupting macrophages by JNK-dependent transcription of macrophage chemoattractant molecules. In the secondary tissue, JNKs are instrumental in the premetastatic niche and stimulate tumor cell proliferation. JNK expression in cancer cells stimulates tissue-remodeling macrophages to improve tumor colonization. However, in T-cells, JNKs alter cytokine production that increases tumor surveillance and inhibits the recruitment of tissue-remodeling macrophages. Therapeutically targeting JNKs for metastatic disease is attractive considering their promotion of metastasis; however, specific JNK tools are needed to determine their definitive actions within the context of the entire metastatic cascade.
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http://dx.doi.org/10.1177/1947601913485413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3863335PMC
September 2013

Jnk2 effects on tumor development, genetic instability and replicative stress in an oncogene-driven mouse mammary tumor model.

PLoS One 2010 May 3;5(5):e10443. Epub 2010 May 3.

Division of Pharmacology and Toxicology, Center for Molecular and Cellular Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, Texas, United States of America.

Oncogenes induce cell proliferation leading to replicative stress, DNA damage and genomic instability. A wide variety of cellular stresses activate c-Jun N-terminal kinase (JNK) proteins, but few studies have directly addressed the roles of JNK isoforms in tumor development. Herein, we show that jnk2 knockout mice expressing the Polyoma Middle T Antigen transgene developed mammary tumors earlier and experienced higher tumor multiplicity compared to jnk2 wildtype mice. Lack of jnk2 expression was associated with higher tumor aneuploidy and reduced DNA damage response, as marked by fewer pH2AX and 53BP1 nuclear foci. Comparative genomic hybridization further confirmed increased genomic instability in PyV MT/jnk2-/- tumors. In vitro, PyV MT/jnk2-/- cells underwent replicative stress and cell death as evidenced by lower BrdU incorporation, and sustained chromatin licensing and DNA replication factor 1 (CDT1) and p21(Waf1) protein expression, and phosphorylation of Chk1 after serum stimulation, but this response was not associated with phosphorylation of p53 Ser15. Adenoviral overexpression of CDT1 led to similar differences between jnk2 wildtype and knockout cells. In normal mammary cells undergoing UV induced single stranded DNA breaks, JNK2 localized to RPA (Replication Protein A) coated strands indicating that JNK2 responds early to single stranded DNA damage and is critical for subsequent recruitment of DNA repair proteins. Together, these data support that JNK2 prevents replicative stress by coordinating cell cycle progression and DNA damage repair mechanisms.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0010443PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2862739PMC
May 2010