Döppler, Heike

Pancreatic acinar-to-ductal metaplasia (ADM) is a reversible process that occurs after pancreatic injury, but becomes permanent and leads to pancreatic lesions in the presence of an oncogenic mutation in KRAS,. While inflammatory macrophage-secreted chemokines, growth factors that activate epidermal growth factor receptor (EGFR) and oncogenic KRAS have been implicated in the induction of ADM, it is currently unclear whether a common underlying signaling mechanism exists that drives this process. In this study, we show that different inducers of ADM increase levels of hydrogen peroxide, most likely generated at the mitochondria, and upregulate the expression of Protein Kinase D1 (PKD1), a kinase that can be activated by hydrogen peroxide. PKD1 expression in acinar cells affects their survival and mediates ADM, which is in part due to the PKD1 target NF-κB. Overall, our data implicate ROS-PKD1 signaling as a common feature of different inducers of pancreatic ADM.

The development of pancreatic cancer requires recruitment and activation of different macrophage populations. However, little is known about how macrophages are attracted to the pancreas after injury or an oncogenic event, and how they crosstalk with lesion cells or other cells of the lesion microenvironment. Here, we delineate the importance of CXCL10/CXCR3 signaling during the early phase of murine pancreatic cancer. We show that CXCL10 is produced by pancreatic precancerous lesion cells in response to IFNγ signaling and that inflammatory macrophages are recipients for this chemokine. CXCL10/CXCR3 signaling in macrophages mediates their chemoattraction to the pancreas, enhances their proliferation, and maintains their inflammatory identity. Blocking of CXCL10/CXCR3 signaling in vivo shifts macrophage populations to a tumor-promoting (Ym1 + , Fizz + , Arg1 + ) phenotype, increases fibrosis, and mediates progression of lesions, highlighting the importance of this pathway in PDA development. This is reversed when CXCL10 is overexpressed in PanIN cells.

Vascular endothelial growth factor A (VEGF) signals primarily through its cognate receptor VEGFR-2 to control vasculogenesis and angiogenesis. Dysregulation of these physiological processes contributes to the pathologies of heart disease, stroke, and cancer. Protein kinase D (PKD) plays a crucial role in the regulation of angiogenesis by modulating endothelial cell proliferation and migration. In human umbilical vein endothelial cells (HUVEC) and human blood outgrowth endothelial cells (BOEC), knockdown of PKD-1 or PKD-2 downregulates VEGFR-2 and significantly inhibits VEGF-induced endothelial cell proliferation and migration. We sought to determine the molecular mechanism through which PKD modulates VEGFR-2 expression. Based on bioinformatics data, activating enhancer binding protein 2 (AP2) binding sites exist within the VEGFR-2 promoter. Thus, we hypothesized PKD may downregulate VEGFR-2 through AP2-mediated transcriptional repression of the VEGFR-2 promoter. Indeed, AP2β binds the VEGFR-2 promoter upon PKD knockdown in HUVEC as evident by chromatin immunoprecipitation assay. Luciferase reporter assays using serial deletions of AP2β binding sites within the VEGFR-2 promoter revealed transcriptional activity negatively correlated with the number of AP2β binding sites, thus confirming negative regulation of VEGFR-2 transcription by AP2β. Next, using siRNA, we demonstrated that upregulation of AP2β decreased VEGFR-2 expression and loss of AP2β enhanced VEGFR-2 expression. In vivo studies confirmed this finding as we observed increased VEGFR-2 immunostaining in the dorsal horn of the spinal cord of embryonic day 13 AP2β knockout mice. We hypothesize that PKD directly regulates AP2β function by serine phosphorylation and ongoing studies are being conducted to determine phosphorylation sites in AP2β directly regulated by PKD. Taken together, we demonstrate AP2β negatively regulates VEGFR-2 transcription and VEGFR-2 is a major downstream target of PKD. Our findings describing how PKD regulates angiogenesis may contribute to the development of therapies to improve the clinical outcome of patients afflicted by heart disease, stroke, and cancer.

Summary Activating mutations of the K‐ras proto‐oncogene are detected in over 95% of pancreatic adenocarcinoma (PDA) and its precursor lesions. One mechanism by which activated K‐ras can drive the development of PDA is activation of the transcription factor nuclear factor κ‐B (NF‐κB), which has been shown to regulate genes involved in all aspects of tumor formation and progression. We here describe the PRKD1 gene promoter as a target for K‐ras‐NF‐κB signaling. We identify the binding sites for NF‐κB in the PRKD1 promoter and show that K‐ras‐driven upregulation of expression of PRKD1 and its gene product protein kinase D1 (PKD1) is linked to increased cell survival and oncogenic signaling in PDA. Conclusion Our data provide a functional link between oncogenic K‐ras, NF‐κB and PKD1, a targetable kinase in this cancer. Grant Funding Source : Supported by the NCI R01 grant CA140182

Abstract 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.

Abstract Pancreatic cancer is characterized by an inflammatory environment. Here we delineate the crosstalk between different macrophage populations with pancreatic cells carrying oncogenic Kras mutations. First, we show that pancreatic acinar cells that undergo oncogenic transformation by mutant Kras upregulate chemoattractants that attract inflammatory macrophages. These inflammatory macrophages contribute to acinar cell dedifferentiation to a progenitor-like cell type (acinar-to-ductal metaplasia; ADM). Resulting cells can give rise to PanIN lesions. We then provide insight at which stage of PanIN formation a switch between inflammatory and alternatively-activated macrophages occurs; and define one mechanism by which this can be mediated. Eventually, we provide insight of how alternatively-activated macrophages facilitate the further progression of PanIN lesions to a more aggressive phenotype. Citation Format: Geou-Yarh Liou, Heike Doeppler, Ligia Bastea, Peter Storz.{Authors}. Crosstalk of different macrophage populations with pancreatic acinar or PanIN cells and contribution to development of pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A59.

Abstract The development of pancreatic cancer requires both obtain of oncogenic Kras mutations and up-regulation of growth factor signaling. However, how oncogenic Kras regulates growth factor signaling in pancreatic cancer development is still unclear. Using a transgenic mouse model harboring an oncogenic Kras mutation and a 3D organoid explant culture of primary pancreatic acini, we here show that expression of mutant Kras in pancreatic acinar cells alters their mitochondrial metabolism, resulting in increased generation of mitochondrial reactive oxygen species (mROS). We further demonstrate that mROS induced by oncogenic Kras is required for transdifferentiating acinar cells to a duct-like phenotype and eventually progression to pancreatic intraepithelial neoplasia (PanIN), the most common precursor lesions of pancreatic ductal adenocarcinoma (PDAC). This transdiffentiation process is mediated by increased levels of epidermal growth factor receptor (EGFR) as well as its ligands, EGF and TGFα, through activation of the ROS-receptive transcription factors, NF-κB1 and NF-κB2. In Kas transgenic mice, the interception of KrasG12D-mediated generation of mROS significantly reduced the formation of pre-neoplastic lesions. Hence, our data provide mechanistic insight of how oncogenic Kras mutant crosstalks with growth factor signaling to cause the formation of pancreatic cancer. Citation Format: Geou-Yarh Liou, Heike Doeppler, Kathleen E. DelGirono, Howard C. Crawford, Michael P. Murphy, Peter Storz. Oncogenic Kras-induced mitochondrial oxidative stress in pancreatic acini modulates the formation of precancerous lesions through autocrine EGFR signaling. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr PR01.