RCAN1 is a marker of oxidative stress, induced in acute pancreatitis.

BACKGROUND: To date, there still is a lack of specific acute pancreatitis markers and specifically an early marker that can reliably predict disease severity. The inflammatory response in acute pancreatitis is mediated in part through oxidative stress and calcineurin-NFAT (Nuclear Factor of Activated T-cells) signaling, which is inducing its own negative regulator, regulator of calcineurin 1 (RCAN1). Caerulein induction is a commonly used in vivo model of experimental acute pancreatitis. Caerulein induces CN-NFAT signaling, reactive oxygen species and inflammation. METHODS: To screen for potential markers of acute pancreatitis, we used the caerulein model of experimental acute pancreatitis (AP) in C57Bl/6 J mice. Pancreata from treated and control mice were used for expression profiling. Promising gene candidates were validated in cell culture experiments using primary murine acinar cells and rat AR42J cells. These candidates were then further tested for their usefulness as biomarkers in mouse and human plasma. RESULTS: We identified a number of novel genes, including Regulator of calcineurin 1 (Rcan1) and Sestrin 2 (Sesn2) and demonstrated that they are induced by oxidative stress, by stimulation with H2O2 and by inhibiting caerulein stimulated expression with the antioxidant N-acetylcysteine. We found Rcan1 protein to be significantly elevated in AP-induced mouse plasma as well as in plasma from AP patients. CONCLUSION: We demonstrated that Rcan1 is regulated by oxidative stress and identified RCAN1 as a potential diagnostic marker of AP.

The extracellular matrix and focal adhesion kinase signaling regulate cancer stem cell function in pancreatic ductal adenocarcinoma.

Cancer stem cells (CSCs) play an important role in the clonogenic growth and metastasis of pancreatic ductal adenocarcinoma (PDAC). A hallmark of PDAC is the desmoplastic reaction, but the impact of the tumor microenvironment (TME) on CSCs is unknown. In order to better understand the mechanisms, we examined the impact of extracellular matrix (ECM) proteins on PDAC CSCs. We quantified the effect of ECM proteins, ß1-integrin, and focal adhesion kinase (FAK) on clonogenic PDAC growth and migration in vitro and tumor initiation, growth, and metastasis in vivo in nude mice using shRNA and overexpression constructs as well as small molecule FAK inhibitors. Type I collagen increased PDAC tumor initiating potential, self-renewal, and the frequency of CSCs through the activation of FAK. FAK overexpression increased tumor initiation, whereas a dominant negative FAK mutant or FAK kinase inhibitors reduced clonogenic PDAC growth in vitro and in vivo. Moreover, the FAK inhibitor VS-4718 extended the anti-tumor response to gemcitabine and nab-paclitaxel in patient-derived PDAC xenografts, and the loss of FAK expression limited metastatic dissemination of orthotopic xenografts. Type I collagen enhances PDAC CSCs, and both kinase-dependent and independent activities of FAK impact PDAC tumor initiation, self-renewal, and metastasis. The anti-tumor impact of FAK inhibitors in combination with standard chemotherapy support the clinical testing of this combination.

Real-time assessment of tissue hypoxia in vivo with combined photoacoustics and high-frequency ultrasound.

PURPOSE: In preclinical cancer studies, non-invasive functional imaging has become an important tool to assess tumor development and therapeutic effects. Tumor hypoxia is closely associated with tumor aggressiveness and is therefore a key parameter to be monitored. Recently, photoacoustic (PA) imaging with inherently co-registered high-frequency ultrasound (US) has reached preclinical applicability, allowing parallel collection of anatomical and functional information. Dual-wavelength PA imaging can be used to quantify tissue oxygen saturation based on the absorbance spectrum differences between hemoglobin and deoxyhemoglobin. EXPERIMENTAL DESIGN: A new bi-modal PA/US system for small animal imaging was employed to test feasibility and reliability of dual-wavelength PA for measuring relative tissue oxygenation. Murine models of pancreatic and colon cancer were imaged, and differences in tissue oxygenation were compared to immunohistochemistry for hypoxia in the corresponding tissue regions. RESULTS: Functional studies proved feasibility and reliability of oxygenation detection in murine tissue in vivo. Tumor models exhibited different levels of hypoxia in localized regions, which positively correlated with immunohistochemical staining for hypoxia. Contrast-enhanced imaging yielded complementary information on tissue perfusion using the same system. CONCLUSION: Bimodal PA/US imaging can be utilized to reliably detect hypoxic tumor regions in murine tumor models, thus providing the possibility to collect anatomical and functional information on tumor growth and treatment response live in longitudinal preclinical studies.