Publications by authors named "Peter Storz"

96 Publications

Dysfunctional EGFR and oxidative stress-induced PKD1 signaling drive formation of DCLK1+ pancreatic stem cells.

iScience 2021 Jan 5;24(1):102019. Epub 2021 Jan 5.

Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, FL 32224, USA.

Doublecortin-like kinase 1 (DCLK1)-positive pancreatic cancer stem cells develop at a precancerous stage and may contribute to the lack of efficacy of pancreatic cancer therapy. Although PanIN cells express oncogenic KRas and have an increased activity of epidermal growth factor receptor (EGFR), we demonstrate that, in DCLK1 PanIN cells, EGFR signaling is not propagated to the nucleus. Mimicking blockage of EGFR with erlotinib in PanIN organoid culture or in p48;Kras mice led to a significant increase in DCLK1 PanIN cells. As a mechanism of how EGFR inhibition leads to formation of DCLK1 cells, we identify an increase in hydrogen peroxide contributing to activation of Protein Kinase D1 (PKD1). Active PKD1 then drives stemness and abundance of DCLK1 cells in lesions. Our data suggest a signaling mechanism that leads to the development of DCLK1 pancreatic cancer stem cells, which can be exploited to target this population in potential therapeutic approaches.
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http://dx.doi.org/10.1016/j.isci.2020.102019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820128PMC
January 2021

Carcinogenesis of Pancreatic Ductal Adenocarcinoma.

Gastroenterology 2020 06 19;158(8):2072-2081. Epub 2020 Mar 19.

Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan. Electronic address:

Although the estimated time for development of pancreatic ductal adenocarcinoma (PDA) is more than 20 years, PDAs are usually detected at late, metastatic stages. PDAs develop from duct-like cells through a multistep carcinogenesis process, from low-grade dysplastic lesions to carcinoma in situ and eventually to metastatic disease. This process involves gradual acquisition of mutations in oncogenes and tumor suppressor genes, as well as changes in the pancreatic environment from a pro-inflammatory microenvironment that favors the development of early lesions, to a desmoplastic tumor microenvironment that is highly fibrotic and immune suppressive. This review discusses our current understanding of how PDA originates.
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http://dx.doi.org/10.1053/j.gastro.2020.02.059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7282937PMC
June 2020

Alzheimer's Risk Factors Age, APOE Genotype, and Sex Drive Distinct Molecular Pathways.

Neuron 2020 06 20;106(5):727-742.e6. Epub 2020 Mar 20.

Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA; Neuroscience Graduate Program, Mayo Clinic, Jacksonville, FL 32224, USA. Electronic address:

Evidence suggests interplay among the three major risk factors for Alzheimer's disease (AD): age, APOE genotype, and sex. Here, we present comprehensive datasets and analyses of brain transcriptomes and blood metabolomes from human apoE2-, apoE3-, and apoE4-targeted replacement mice across young, middle, and old ages with both sexes. We found that age had the greatest impact on brain transcriptomes highlighted by an immune module led by Trem2 and Tyrobp, whereas APOE4 was associated with upregulation of multiple Serpina3 genes. Importantly, these networks and gene expression changes were mostly conserved in human brains. Finally, we observed a significant interaction between age, APOE genotype, and sex on unfolded protein response pathway. In the periphery, APOE2 drove distinct blood metabolome profile highlighted by the upregulation of lipid metabolites. Our work identifies unique and interactive molecular pathways underlying AD risk factors providing valuable resources for discovery and validation research in model systems and humans.
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http://dx.doi.org/10.1016/j.neuron.2020.02.034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7388065PMC
June 2020

Early detection and imaging strategies to reveal and target developing pancreatic cancer.

Expert Rev Anticancer Ther 2020 02 27;20(2):81-83. Epub 2020 Jan 27.

Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, FL, USA.

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http://dx.doi.org/10.1080/14737140.2020.1720654DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7380330PMC
February 2020

The GEF-H1/PKD3 signaling pathway promotes the maintenance of triple-negative breast cancer stem cells.

Int J Cancer 2020 06 14;146(12):3423-3434. Epub 2019 Dec 14.

Institute of Cell Biology and Immunology and Stuttgart Research Center Systems Biology, University of Stuttgart, Stuttgart, Germany.

Protein kinase D3 (PKD3) is upregulated in triple-negative breast cancer (TNBC) and associated with cell proliferation and metastasis development but its precise pro-oncogenic function is unknown. Here we show that PKD3 is required for the maintenance of the TNBC stem cell population. The depletion of PKD3 in MDA-MB-231 cells reduced the cancer stem cell frequency in vitro and tumor initiation potential in vivo. We further provide evidence that the RhoGEF GEF-H1 is upstream of PKD3 activation in TNBC stem cells. Most importantly, pharmacological PKD inhibition in combination with paclitaxel synergistically decreased oncosphere and colony formation efficiency in vitro and tumor recurrence in vivo. Based on our results we propose that targeting the GEF-H1/PKD3 signaling pathway in combination with chemotherapy might provide an effective therapeutic option for TNBC.
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http://dx.doi.org/10.1002/ijc.32798DOI Listing
June 2020

Sangivamycin and its derivatives inhibit Haspin-Histone H3-survivin signaling and induce pancreatic cancer cell death.

Sci Rep 2019 11 12;9(1):16588. Epub 2019 Nov 12.

Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, FL, 32224, USA.

Current treatment options for patients with pancreatic cancer are suboptimal, resulting in a five year survival rate of about 9%. Difficulties with treatment are due to an immunosuppressive, fibrotic tumor microenvironment that prevents drugs from reaching tumor cells, but also to the limited efficacy of existing FDA-approved chemotherapeutic compounds. We here show that the nucleoside analog Sangivamycin and its closely-related compound Toyocamycin target PDA cell lines, and are significantly more efficient than Gemcitabine. Using KINOMEscan screening, we identified the kinase Haspin, which is overexpressed in PDA cell lines and human PDA samples, as a main target for both compounds. Inhibition of Haspin leads to a decrease in Histone H3 phosphorylation and prevents Histone H3 binding to survivin, thus providing mechanistic insight of how Sangivamycin targets cell proliferation, mitosis and induces apoptotic cell death. In orthotopically implanted tumors in mice, Sangivamycin was efficient in decreasing the growth of established tumors. In summary, we show that Sangivamycin and derivatives can be an efficient new option for treatment of PDA.
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http://dx.doi.org/10.1038/s41598-019-53223-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6851150PMC
November 2019

Pomalidomide-induced changes in the pancreatic tumor microenvironment and potential for therapy.

Authors:
Peter Storz

Oncoscience 2019 Jul 23;6(7-8):351-353. Epub 2019 Aug 23.

Mayo Clinic, Griffin Building, Jacksonville, FL, USA.

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http://dx.doi.org/10.18632/oncoscience.486DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6768848PMC
July 2019

Protein kinase D up-regulates transcription of in endothelial cells by suppressing nuclear localization of the transcription factor AP2β.

J Biol Chem 2019 10 6;294(43):15759-15767. Epub 2019 Sep 6.

Department of Biochemistry and Molecular Biology, College of Medicine and Science, Mayo Clinic, Jacksonville, Florida 32224

Vascular endothelial growth factor A (VEGF) signals primarily through its cognate receptor VEGF receptor-2 (VEGFR-2) to control vasculogenesis and angiogenesis, key physiological processes in cardiovascular disease and cancer. In human umbilical vein endothelial cells (HUVECs), knockdown of protein kinase D-1 (PKD1) or PKD2 down-regulates VEGFR-2 expression and inhibits VEGF-induced cell proliferation and migration. However, how PKD regulates VEGF signaling is unclear. Previous bioinformatics analyses have identified binding sites for the transcription factor activating enhancer-binding protein 2 (AP2) in the promoter. Using ChIP analyses, here we found that PKD knockdown in HUVECs increases binding of AP2β to the promoter. Luciferase reporter assays with serial deletions of AP2-binding sites within the promoter revealed that its transcriptional activity negatively correlates with the number of these sites. Next we demonstrated that AP2β up-regulation decreases VEGFR-2 expression and that loss of AP2β enhances VEGFR-2 expression in HUVECs. experiments confirmed increased VEGFR-2 immunostaining in the spinal cord of AP2β knockout mouse embryos. Mechanistically, we observed that PKD phosphorylates AP2β at Ser and Ser and suppresses its nuclear accumulation. Inhibition of PKD activity with a pan-PKD inhibitor increased AP2β nuclear localization, and overexpression of both WT and constitutively active PKD1 or PKD2 reduced AP2β nuclear localization through a Ser- and Ser-dependent mechanism. Furthermore, substitution of Ser in AP2β increased its binding to the promoter. Our findings uncover evidence of a molecular pathway that regulates expression, insights that may shed light on the etiology of diseases associated with aberrant VEGF/VEGFR signaling.
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http://dx.doi.org/10.1074/jbc.RA119.010152DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6816101PMC
October 2019

Mucin-1 is required for Coxsackie Virus B3-induced inflammation in pancreatitis.

Sci Rep 2019 07 23;9(1):10656. Epub 2019 Jul 23.

Division of Surgical Oncology, Department of Surgery, Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA.

The Muc-1 oncoprotein is a tumor-associated mucin often overexpressed in pancreatic cancer. We report that knockout of Muc-1 reduced the degree of pancreatic inflammation that resulted from infection with Coxsackievirus B3 (CVB3) in a mouse model. CVB3-infected Muc-1-deficient (Muc-1) mice had significantly reduced infiltration of macrophages into the murine pancreas. We found that Muc-1 signaling through NF-κB increased expression of ICAM-1, a pro-inflammatory mediator that recruits macrophages. Further investigation revealed that bone marrow derived macrophages (BMDM) from the Muc-1 mice exhibited defective migration properties, in part due to low expression of the C-C motif chemokine receptor (CCR2) and the integrin Very Late Antigen 4 (VLA-4). The results presented here provide novel insight into the role of Muc-1 in regulating the inflammatory response and the cellular microenvironment in pancreatitis.
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http://dx.doi.org/10.1038/s41598-019-46933-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6650496PMC
July 2019

Targeting the tumor microenvironment in pancreatic ductal adenocarcinoma.

Expert Rev Anticancer Ther 2019 06 31;19(6):473-482. Epub 2019 May 31.

a Department of Cancer Biology , Mayo Clinic , Jacksonville , FL , USA.

: The dismally slow improvement in patient survival over the years for pancreatic cancer patients is mainly due to two factors: the late diagnosis, at which point the disease is spread to distant organs; and the fact that tumor cells are surrounded by a dense, highly immunosuppressive microenvironment. The tumor microenvironment not only shields pancreatic cancer cells from chemotherapy but also leaves it unsusceptible to various immunotherapeutic strategies that have been proven successful in other types of cancer. : This review highlights the main components of the pancreatic tumor microenvironment, how they cross-talk with each other to generate stroma and promote tumor growth. Additionally, we discuss the most promising treatment targets in the microenvironment whose modulation can be robustly tested in combination with standard of care chemotherapy. Currently, active clinical trials for pancreatic cancer involving components of the microenvironment are also listed. : Although immunotherapeutic approaches involving checkpoint inhibition are being pursued enthusiastically, there is still more work to be done with several other emerging immune targets that could provide therapeutic benefit.
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http://dx.doi.org/10.1080/14737140.2019.1622417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6548630PMC
June 2019

Mimicking and Manipulating Pancreatic Acinar-to-Ductal Metaplasia in 3-dimensional Cell Culture.

J Vis Exp 2019 02 11(144). Epub 2019 Feb 11.

Department of Cancer Biology, Mayo Clinic Florida;

The differentiation of acinar cells to ductal cells during pancreatitis and in the early development of pancreatic cancer is a key process that requires further study. To understand the mechanisms regulating acinar-to-ductal metaplasia (ADM), ex vivo 3D culture and differentiation of primary acinar cells to ductal cells offers many advantages over other systems. With the technique herein, modulation of protein expression is simple and quick, requiring only one day to isolate, stimulate or virally infect, and begin culturing primary acinar cells to investigate the ADM process. In contrast to using basement membrane matrix, the seeding of acinar cell clusters in collagen I extracellular matrix, allows acinar cells to retain their acinar identity before manipulation. This is vital when testing the contribution of various components to the induction of ADM. Not only are the effects of cytokines or other ectopically administered factors testable through this technique, but the contribution of common mutations, increased protein expression, or knockdown of protein expression is testable via viral infection of primary acinar cells, using adenoviral or lentiviral vectors. Moreover, cells can be re-isolated from collagen or basement membrane matrix at the endpoint and analyzed for protein expression.
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http://dx.doi.org/10.3791/59096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6922010PMC
February 2019

Pomalidomide Alters Pancreatic Macrophage Populations to Generate an Immune-Responsive Environment at Precancerous and Cancerous Lesions.

Cancer Res 2019 04 29;79(7):1535-1548. Epub 2019 Jan 29.

Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, Florida.

During development of pancreatic cancer, alternatively activated macrophages contribute to fibrogenesis, pancreatic intraepithelial neoplasia (PanIN) lesion growth, and generation of an immunosuppressive environment. Here, we show that the immunomodulatory agent pomalidomide depletes pancreatic lesion areas of alternatively activated macrophage populations. Pomalidomide treatment resulted in downregulation of interferon regulatory factor 4, a transcription factor for M2 macrophage polarization. Pomalidomide-induced absence of alternatively activated macrophages led to a decrease in fibrosis at PanIN lesions and in syngeneic tumors; this was due to generation of an inflammatory, immune-responsive environment with increased expression of IL1α and presence of activated (IFNγ-positive) CD4 and CD8 T-cell populations. Our results indicate that pomalidomide could be used to decrease fibrogenesis in pancreatic cancer and may be ideal as a combination treatment with chemotherapeutic drugs or other immunotherapies. SIGNIFICANCE: These findings reveal new insights into how macrophage populations within the pancreatic cancer microenvironment can be modulated, providing the means to turn the microenvironment from immunosuppressive to immune-responsive.
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http://dx.doi.org/10.1158/0008-5472.CAN-18-1153DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6445670PMC
April 2019

The phosphorylation status of PIP5K1C at serine 448 can be predictive for invasive ductal carcinoma of the breast.

Oncotarget 2018 Nov 20;9(91):36358-36370. Epub 2018 Nov 20.

Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, FL 32224, USA.

Phosphatidylinositol-4-phosphate 5-kinase type-1C (PIP5K1C) is a lipid kinase that regulates focal adhesion dynamics and cell attachment through site-specific formation of phosphatidylinositol-4,5-bisphosphate (PI4,5P). By comparing normal breast tissue to carcinoma and invasive ductal carcinoma subtypes, we here show that the phosphorylation status of PIP5K1C at serine residue 448 (S448) can be predictive for breast cancer progression to an aggressive phenotype, while PIP5K1C expression levels are not indicative for this event. PIP5K1C phosphorylation at S448 is downregulated in invasive ductal carcinoma, and similarly, the expression levels of PKD1, the kinase that phosphorylates PIP5K1C at this site, are decreased. Overall, since PKD1 is a negative regulator of cell migration and invasion in breast cancer, the phosphorylation status of this residue may serve as an indicator of aggressiveness of breast tumors.
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http://dx.doi.org/10.18632/oncotarget.26357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6284740PMC
November 2018

Protein kinase D1: gatekeeper of the epithelial phenotype and key regulator of cancer metastasis?

Authors:
Peter Storz

Br J Cancer 2018 02 20;118(4):459-461. Epub 2018 Feb 20.

Department of Cancer Biology, Mayo Clinic, Jacksonville, FL 32224, USA.

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http://dx.doi.org/10.1038/bjc.2018.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5830601PMC
February 2018

Paracrine Secretion of Transforming Growth Factor β by Ductal Cells Promotes Acinar-to-Ductal Metaplasia in Cultured Human Exocrine Pancreas Tissues.

Pancreas 2017 10;46(9):1202-1207

From the *Departments of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX; †Department of Cancer Biology, Mayo Clinic, Jacksonville, FL; and ‡Surgery Department, University of Pennsylvania School of Medicine, Philadelphia, PA.

Objective: We aimed to evaluate the contribution of acinar-to-ductal metaplasia (ADM) to the accumulation of cells with a ductal phenotype in cultured human exocrine pancreatic tissues and reveal the underlying mechanism.

Methods: We sorted and cultured viable cell populations in human exocrine pancreatic tissues with a flow cytometry-based lineage tracing method to evaluate possible mechanisms of ADM. Cell surface markers, gene expression pattern, and sphere formation assay were used to examine ADM.

Results: A large proportion of acinar cells gained CD133 expression during the 2-dimensional culture and showed down-regulation of acinar markers and up-regulation of ductal markers, assuming an ADM phenotype. In a serum-free culture condition, ADM induction was mainly dependent on transforming growth factor β (TGF-β) secreted from cultured ductal cells. Human acinar cells when cultured alone for a week in a serum-free condition do not undergo ADM. However, serum may contain other factors besides TGF-β to induce ADM in human acinar cells. In addition, we found that TGF-β cannot induce ADM of murine acinar cells.

Conclusions: Ductal cells are the major source of TGF-β that induces ADM in cultured human exocrine pancreatic tissues. This culture system might be a useful model to investigate the mechanism of ADM in human cells.
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http://dx.doi.org/10.1097/MPA.0000000000000913DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6192250PMC
October 2017

Src-mediated tyrosine phosphorylation of Protein Kinase D2 at focal adhesions regulates cell adhesion.

Sci Rep 2017 08 25;7(1):9524. Epub 2017 Aug 25.

Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida, 32224, USA.

Dependent on their cellular localization, Protein Kinase D (PKD) enzymes regulate different processes including Golgi transport, cell signaling and response to oxidative stress. The localization of PKD within cells is mediated by interaction with different lipid or protein binding partners. With the example of PKD2, we here show that phosphorylation events can also contribute to localization of subcellular pools of this kinase. Specifically, in the present study, we show that tyrosine phosphorylation of PKD2 at residue Y87 defines its localization to the focal adhesions and leads to activation. This phosphorylation occurs downstream of RhoA signaling and is mediated via Src. Moreover, mutation of this residue blocks PKD2's interaction with Focal Adhesion Kinase (FAK). The presence and regulation of PKD2 at focal adhesions identifies a novel function for this kinase as a modulator of cell adhesion and migration.
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http://dx.doi.org/10.1038/s41598-017-10210-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5573332PMC
August 2017

Protein kinase C isoforms in the normal pancreas and in pancreatic disease.

Cell Signal 2017 12 18;40:1-9. Epub 2017 Aug 18.

Department of Cancer Biology, Mayo Clinic, Jacksonville, FL, USA. Electronic address:

Protein Kinase C isoforms have been implicated in regulating multiple processes within the healthy pancreas. Moreover, their dysregulation contributes to all aspects of pancreatic disease. In this review, with a focus on acinar, ductal, and islet cells, we highlight the roles and contributions of the different PKC isoforms to normal pancreas function. We also discuss the contribution of PKC enzymes to pancreatic diseases, including insulin resistance and diabetes mellitus, as well as pancreatitis and the development and progression of pancreatic cancer.
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http://dx.doi.org/10.1016/j.cellsig.2017.08.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651200PMC
December 2017

Glycogen synthase kinase-3β ablation limits pancreatitis-induced acinar-to-ductal metaplasia.

J Pathol 2017 09 27;243(1):65-77. Epub 2017 Jul 27.

Division of Oncology Research and Schulze Center for Novel Therapeutics, Mayo Clinic, Rochester, MN, USA.

Acinar-to-ductal metaplasia (ADM) is a reversible epithelial transdifferentiation process that occurs in the pancreas in response to acute inflammation. ADM can rapidly progress towards pre-malignant pancreatic intraepithelial neoplasia (PanIN) lesions in the presence of mutant KRas and ultimately pancreatic adenocarcinoma (PDAC). In the present work, we elucidate the role and related mechanism of glycogen synthase kinase-3beta (GSK-3β) in ADM development using in vitro 3D cultures and genetically engineered mouse models. We show that GSK-3β promotes TGF-α-induced ADM in 3D cultured primary acinar cells, whereas deletion of GSK-3β attenuates caerulein-induced ADM formation and PanIN progression in Kras transgenic mice. Furthermore, we demonstrate that GSK-3β ablation influences ADM formation and PanIN progression by suppressing oncogenic KRas-driven cell proliferation. Mechanistically, we show that GSK-3β regulates proliferation by increasing the activation of S6 kinase. Taken together, these results indicate that GSK-3β participates in early pancreatitis-induced ADM and thus could be a target for the treatment of chronic pancreatitis and the prevention of PDAC progression. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/path.4928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6042855PMC
September 2017

The Presence of Interleukin-13 at Pancreatic ADM/PanIN Lesions Alters Macrophage Populations and Mediates Pancreatic Tumorigenesis.

Cell Rep 2017 05;19(7):1322-1333

Department of Cancer Biology, Mayo Clinic, Jacksonville, FL 32224, USA. Electronic address:

The contributions of the innate immune system to the development of pancreatic cancer are still ill defined. Inflammatory macrophages can initiate metaplasia of pancreatic acinar cells to a duct-like phenotype (acinar-to-ductal metaplasia [ADM]), which then gives rise to pancreatic intraepithelial neoplasia (PanIN) when oncogenic KRas is present. However, it remains unclear when and how this inflammatory macrophage population is replaced by tumor-promoting macrophages. Here, we demonstrate the presence of interleukin-13 (IL-13), which can convert inflammatory into Ym1+ alternatively activated macrophages, at ADM/PanIN lesions. We further show that Ym1+ macrophages release factors, such as IL-1ra and CCL2, to drive pancreatic fibrogenesis and tumorigenesis. Treatment of mice expressing oncogenic KRas under an acinar cell-specific promoter with a neutralizing antibody for IL-13 significantly decreased the accumulation of alternatively activated macrophages at these lesions, resulting in decreased fibrosis and lesion growth.
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http://dx.doi.org/10.1016/j.celrep.2017.04.052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5510483PMC
May 2017

Differential regulation of PKD isoforms in oxidative stress conditions through phosphorylation of a conserved Tyr in the P+1 loop.

Sci Rep 2017 04 20;7(1):887. Epub 2017 Apr 20.

Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Leuven, Belgium.

Protein kinases are essential molecules in life and their crucial function requires tight regulation. Many kinases are regulated via phosphorylation within their activation loop. This loop is embedded in the activation segment, which additionally contains the Mg binding loop and a P + 1 loop that is important in substrate binding. In this report, we identify Abl-mediated phosphorylation of a highly conserved Tyr residue in the P + 1 loop of protein kinase D2 (PKD2) during oxidative stress. Remarkably, we observed that the three human PKD isoforms display very different degrees of P + 1 loop Tyr phosphorylation and we identify one of the molecular determinants for this divergence. This is paralleled by a different activation mechanism of PKD1 and PKD2 during oxidative stress. Tyr phosphorylation in the P + 1 loop of PKD2 increases turnover for Syntide-2, while substrate specificity and the role of PKD2 in NF-κB signaling remain unaffected. Importantly, Tyr to Phe substitution renders the kinase inactive, jeopardizing its use as a non-phosphorylatable mutant. Since large-scale proteomics studies identified P + 1 loop Tyr phosphorylation in more than 70 Ser/Thr kinases in multiple conditions, our results do not only demonstrate differential regulation/function of PKD isoforms under oxidative stress, but also have implications for kinase regulation in general.
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http://dx.doi.org/10.1038/s41598-017-00800-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5430542PMC
April 2017

Mitochondrial and Oxidative Stress-Mediated Activation of Protein Kinase D1 and Its Importance in Pancreatic Cancer.

Front Oncol 2017 15;7:41. Epub 2017 Mar 15.

Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic , Jacksonville, FL , USA.

Due to alterations in their metabolic activity and decreased mitochondrial efficiency, cancer cells often show increased generation of reactive oxygen species (ROS), but at the same time, to avoid cytotoxic signaling and to facilitate tumorigenic signaling, have mechanism in place that keep ROS in check. This requires signaling molecules that convey increases in oxidative stress to signal to the nucleus to upregulate antioxidant genes. Protein kinase D1 (PKD1), the serine/threonine kinase, is one of these ROS sensors. In this mini-review, we highlight the mechanisms of how PKD1 is activated in response to oxidative stress, so far known downstream effectors, as well as the importance of PKD1-initiated signaling for development and progression of pancreatic cancer.
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http://dx.doi.org/10.3389/fonc.2017.00041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5350125PMC
March 2017

Acinar cell plasticity and development of pancreatic ductal adenocarcinoma.

Authors:
Peter Storz

Nat Rev Gastroenterol Hepatol 2017 05 8;14(5):296-304. Epub 2017 Mar 8.

Department of Cancer Biology, Room 306 Griffin Building, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, Florida 32224, USA.

Acinar cells in the adult pancreas show high plasticity and can undergo transdifferentiation to a progenitor-like cell type with ductal characteristics. This process, termed acinar-to-ductal metaplasia (ADM), is an important feature facilitating pancreas regeneration after injury. Data from animal models show that cells that undergo ADM in response to oncogenic signalling are precursors for pancreatic intraepithelial neoplasia lesions, which can further progress to pancreatic ductal adenocarcinoma (PDAC). As human pancreatic adenocarcinoma is often diagnosed at a stage of metastatic disease, understanding the processes that lead to its initiation is important for the discovery of markers for early detection, as well as options that enable an early intervention. Here, the critical determinants of acinar cell plasticity are discussed, in addition to the intracellular and extracellular signalling events that drive acinar cell metaplasia and their contribution to development of PDAC.
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http://dx.doi.org/10.1038/nrgastro.2017.12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6036907PMC
May 2017

Targeting reactive oxygen species in development and progression of pancreatic cancer.

Expert Rev Anticancer Ther 2017 Jan 23;17(1):19-31. Epub 2016 Nov 23.

a Department of Cancer Biology , Mayo Clinic , Jacksonville , FL , USA.

Introduction: Pancreatic ductal adenocarcinoma (PDA) is characterized by expression of oncogenic KRas which drives all aspects of tumorigenesis. Oncogenic KRas induces the formation of reactive oxygen species (ROS) which have been implicated in initiation and progression of PDA. To facilitate tumor promoting levels and to avoid oncogene-induced senescence or cytotoxicity, ROS homeostasis in PDA cells is balanced by additional up-regulation of antioxidant systems. Areas covered: We examine the sources of ROS in PDA, the mechanisms by which ROS homeostasis is maintained, and the biological consequences of ROS in PDA. Additionally, we discuss the potential mechanisms for targeting ROS homoeostasis as a point of therapeutic intervention. An extensive review of the relevant literature as it relates to the topic was conducted using PubMed. Expert commentary: Even though oncogenic mutations in the KRAS gene have been detected in over 95% of human pancreatic adenocarcinoma, targeting its gene product, KRas, has been difficult. The dependency of PDA cells on balancing ROS homeostasis could be an angle for new prevention or treatment strategies. These include use of antioxidants to prevent formation or progression of precancerous lesions, or methods to increase ROS in tumor cells to toxic levels.
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http://dx.doi.org/10.1080/14737140.2017.1261017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5518736PMC
January 2017

Protein Kinase D1 regulates focal adhesion dynamics and cell adhesion through Phosphatidylinositol-4-phosphate 5-kinase type-l γ.

Sci Rep 2016 10 24;6:35963. Epub 2016 Oct 24.

Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida 32224, USA.

Focal adhesions (FAs) are highly dynamic structures that are assembled and disassembled on a continuous basis. The balance between the two processes mediates various aspects of cell behavior, ranging from cell adhesion and spreading to directed cell migration. The turnover of FAs is regulated at multiple levels and involves a variety of signaling molecules and adaptor proteins. In the present study, we show that in response to integrin engagement, a subcellular pool of Protein Kinase D1 (PKD1) localizes to the FAs. PKD1 affects FAs by decreasing turnover and promoting maturation, resulting in enhanced cell adhesion. The effects of PKD1 are mediated through direct phosphorylation of FA-localized phosphatidylinositol-4-phosphate 5-kinase type-l γ (PIP5Klγ) at serine residue 448. This phosphorylation occurs in response to Fibronectin-RhoA signaling and leads to a decrease in PIP5Klγs' lipid kinase activity and binding affinity for Talin. Our data reveal a novel function for PKD1 as a regulator of FA dynamics and by identifying PIP5Klγ as a novel PKD1 substrate provide mechanistic insight into this process.
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http://dx.doi.org/10.1038/srep35963DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5075913PMC
October 2016

Vasodilator-Stimulated Phosphoprotein Activity Is Required for Coxiella burnetii Growth in Human Macrophages.

PLoS Pathog 2016 Oct 6;12(10):e1005915. Epub 2016 Oct 6.

Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America.

Coxiella burnetii is an intracellular bacterial pathogen that causes human Q fever, an acute flu-like illness that can progress to chronic endocarditis and liver and bone infections. Humans are typically infected by aerosol-mediated transmission, and C. burnetii initially targets alveolar macrophages wherein the pathogen replicates in a phagolysosome-like niche known as the parasitophorous vacuole (PV). C. burnetii manipulates host cAMP-dependent protein kinase (PKA) signaling to promote PV formation, cell survival, and bacterial replication. In this study, we identified the actin regulatory protein vasodilator-stimulated phosphoprotein (VASP) as a PKA substrate that is increasingly phosphorylated at S157 and S239 during C. burnetii infection. Avirulent and virulent C. burnetii triggered increased levels of phosphorylated VASP in macrophage-like THP-1 cells and primary human alveolar macrophages, and this event required the Cα subunit of PKA. VASP phosphorylation also required bacterial protein synthesis and secretion of effector proteins via a type IV secretion system, indicating the pathogen actively triggers prolonged VASP phosphorylation. Optimal PV formation and intracellular bacterial replication required VASP activity, as siRNA-mediated depletion of VASP reduced PV size and bacterial growth. Interestingly, ectopic expression of a phospho-mimetic VASP (S239E) mutant protein prevented optimal PV formation, whereas VASP (S157E) mutant expression had no effect. VASP (S239E) expression also prevented trafficking of bead-containing phagosomes to the PV, indicating proper VASP activity is critical for heterotypic fusion events that control PV expansion in macrophages. Finally, expression of dominant negative VASP (S157A) in C. burnetii-infected cells impaired PV formation, confirming importance of the protein for proper infection. This study provides the first evidence of VASP manipulation by an intravacuolar bacterial pathogen via activation of PKA in human macrophages.
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http://dx.doi.org/10.1371/journal.ppat.1005915DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5053435PMC
October 2016

The PRKD1 promoter is a target of the KRas-NF-κB pathway in pancreatic cancer.

Sci Rep 2016 09 21;6:33758. Epub 2016 Sep 21.

Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, FL 32224, USA.

Increased expression of PRKD1 and its gene product protein kinase D1 (PKD1) are linked to oncogenic signaling in pancreatic ductal adenocarcinoma, but a direct functional relationship to oncogenic KRas has not been established so far. We here describe the PRKD1 gene promoter as a target for oncogenic KRas signaling. We demonstrate that KRas-induced activation of the canonical NF-κB pathway is one mechanism of how PRKD1 expression is increased and identify the binding sites for NF-κB in the PRKD1 promoter. Altogether, these results describe a novel mechanism governing PRKD1 gene expression in PDA and provide a functional link between oncogenic KRas, NF-κB and expression of PRKD1.
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http://dx.doi.org/10.1038/srep33758DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5030668PMC
September 2016

Legumain is activated in macrophages during pancreatitis.

Am J Physiol Gastrointest Liver Physiol 2016 09 11;311(3):G548-60. Epub 2016 Aug 11.

Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia; Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia; and ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash University, Parkville, Victoria, Australia.

Pancreatitis is an inflammatory disease of the pancreas characterized by dysregulated activity of digestive enzymes, necrosis, immune infiltration, and pain. Repeated incidence of pancreatitis is an important risk factor for pancreatic cancer. Legumain, a lysosomal cysteine protease, has been linked to inflammatory diseases such as atherosclerosis, stroke, and cancer. Until now, legumain activation has not been studied during pancreatitis. We used a fluorescently quenched activity-based probe to assess legumain activation during caerulein-induced pancreatitis in mice. We detected activated legumain by ex vivo imaging, confocal microscopy, and gel electrophoresis. Compared with healthy controls, legumain activity in the pancreas of caerulein-treated mice was increased in a time-dependent manner. Legumain was localized to CD68(+) macrophages and was not active in pancreatic acinar cells. Using a small-molecule inhibitor of legumain, we found that this protease is not essential for the initiation of pancreatitis. However, it may serve as a biomarker of disease, since patients with chronic pancreatitis show strongly increased legumain expression in macrophages. Moreover, the occurrence of legumain-expressing macrophages in regions of acinar-to-ductal metaplasia suggests that this protease may influence reprogramming events that lead to inflammation-induced pancreatic cancer.
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http://dx.doi.org/10.1152/ajpgi.00047.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5075999PMC
September 2016

A bright future for protein kinase D1 as a drug target to prevent or treat pancreatic cancer.

Mol Cell Oncol 2016 Jan 10;3(1):e1035477. Epub 2015 Dec 10.

The Biotechnology Center of Oslo, University of Oslo , Oslo, Norway.

Pancreatic ductal adenocarcinoma originates from acinar cells that undergo acinar-to-ductal metaplasia (ADM). ADM is initiated in response to growth factors, inflammation, and oncogene activation and leads to a de-differentiated, duct-like phenotype. Our recent publication demonstrated a transforming growth factor α-Kras(G12D)-protein kinase D1-Notch1 signaling axis driving the induction of ADM and further progression to pancreatic intraepithelial neoplasia. This suggests that protein kinase D1 might be an early marker for tumor development and a potential target for drug development.
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http://dx.doi.org/10.1080/23723556.2015.1035477DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4845192PMC
January 2016

KRas, ROS and the initiation of pancreatic cancer.

Authors:
Peter Storz

Small GTPases 2017 01 24;8(1):38-42. Epub 2016 May 24.

a Department of Cancer Biology , Mayo Clinic Comprehensive Cancer Center, Mayo Clinic , Jacksonville , FL , USA.

Oncogenic mutations of KRAS are the most frequent driver mutations in pancreatic cancer. Expression of an oncogenic allele of KRAS leads to metabolic changes and altered cellular signaling that both can increase the production of intracellular reactive oxygen species (ROS). Increases in ROS have been shown to drive the formation and progression of pancreatic precancerous lesions by upregulating survival and growth factor signaling. A key issue for precancerous and cancer cells is to keep ROS at levels where they are beneficial for tumor development and progression, but below the threshold that leads to induction of senescence or cell death. In KRas-driven neoplasia aberrantly increased ROS levels are therefore balanced by an upregulation of antioxidant genes.
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http://dx.doi.org/10.1080/21541248.2016.1192714DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5331894PMC
January 2017