Störz, Peter

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 The protein kinase D (PKD) family of kinases belongs to the CAMK group and consists of three highly homologous enzymes. They play a versatile role in cancer cell signaling, primarily downstream of PKC isoforms. Classically PKDs are activated upon co-localization with PKC at DAG containing membranes, where PKC phosphorylates the PKD activation loop, generating active PKD. Besides this, PKDs are also activated in oxidative stress conditions, where PKD1 protects against cellular damage via signaling to NF-kB. While the three isoforms are highly homologous, they are not redundant in their biological function and oncogenic potential. A picture has emerged which associates PKD1 expression and activity with decreased migration and inhibition of epithelial mesenchymal transition (EMT). PKD2 and PKD3 on the other hand are upregulated in various cancers, and show oncogenic potential e.g. via enhanced ECM breakdown and potentiation of angiogenesis. While non-redundant biological roles continue to surface, the biochemical mechanisms behind these discrepant functions remain mostly elusive. Here, we identify an isoform specific regulation of PKD2 in oxidative stress conditions via the phosphorylation of a key Tyrosine residue in the substrate binding loop of the activation segment which is highly conserved in most Ser/Thr kinases. Phosphorylation of this residue selectively occurs in PKD2 (and not in PKD1). While wild-type PKD1 signals to NF-kB in oxidative stress, we could show that wild-type PKD2 signaling to NF-kB is impeded in these conditions. Substitution of the activation segment Tyr-717 in PKD2 with a non-phosphorylatable Phe restores signaling to NF-kB, indicating that Tyr-717 phosphorylation is a key determinant for the signaling outcome of PKDs in oxidative stress. Note: This abstract was not presented at the conference. Citation Format: Mathias Cobbaut, Rita Derua, Etienne Waelkens, Peter Störz, Veerle Janssens, Johan Van Lint. Differential regulation of Protein Kinase D isoforms in oxidative stress conditions via tyrosine phosphorylation in the activation segment [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B08.

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.

AbstractAcinar‐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 KrasG12D 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.

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.

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.

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.