Evaluating the impact of a rigid and a deformable registration method of pre-treatment images for hypoxia-based dose painting

PURPOSE

To assess the impact of rigid and deformable image registration methods (RIR, DIR) on the outcome of a hypoxia-based dose painting strategy.

MATERIALS AND METHODS

Thirty head and neck cancer patients were imaged with [18F]FMISO-PET/CT before radiotherapy. [18F]FMISO-PET/CT images were registered to the planning-CT by RIR or DIR. The [18F]FMISO uptake was converted into oxygen partial pressure (pO2) maps. Hypoxic Target Volumes were contoured on pO2 maps for the deformed (HTVdef) and non-deformed (HTV) cases. A dose escalation strategy by contours, aiming at 95 % tumour control probability (TCP), was applied. HTVs were characterised based on geometry-related metrics, the underlying pO2 distribution, and the dose boost level. A dosimetric and radiobiological evaluation of selected treatment plans made considering RIR and DIR was performed. Moreover, the TCP of the RIR dose distribution was evaluated when considering the deformed [18F]FMISO-PET image as an indicator of the actual target radiosensitivity to determine the potential impact of an unalignment.

RESULTS

Statistically significant differences were found between HTV and HTVdef for volume-based metrics and underlying pO2 distribution. Eight out of nine treatment plans for HTV and HTVdef showed differences on the level 10 %/3 mm on a gamma analysis. The TCP difference, however, between RIR and the case when the RIR dose distribution was used with the deformed radiosensitivity map was below 2 pp.

CONCLUSIONS

Although the choice of the CTplan-to-PET registration method pre-treatment impacts the HTV localisation and morphology and the corresponding dose distribution, it negligibly affects the TCP in the proposed dose escalation strategy by contours.

Monocarboxylate Transporter-1 (MCT1)-Mediated Lactate Uptake Protects Pancreatic Adenocarcinoma Cells from Oxidative Stress during Glutamine Scarcity Thereby Promoting Resistance against Inhibitors of Glutamine Metabolism

Metabolic compartmentalization of stroma-rich tumors, like pancreatic ductal adenocarcinoma (PDAC), greatly contributes to malignancy. This involves cancer cells importing lactate from the microenvironment (reverse Warburg cells) through monocarboxylate transporter-1 (MCT1) along with substantial phenotype alterations. Here, we report that the reverse Warburg phenotype of PDAC cells compensated for the shortage of glutamine as an essential metabolite for redox homeostasis. Thus, oxidative stress caused by glutamine depletion led to an Nrf2-dependent induction of MCT1 expression in pancreatic T3M4 and A818-6 cells. Moreover, greater MCT1 expression was detected in glutamine-scarce regions within tumor tissues from PDAC patients. MCT1-driven lactate uptake supported the neutralization of reactive oxygen species excessively produced under glutamine shortage and the resulting drop in glutathione levels that were restored by the imported lactate. Consequently, PDAC cells showed greater survival and growth under glutamine depletion when utilizing lactate through MCT1. Likewise, the glutamine uptake inhibitor V9302 and glutaminase-1 inhibitor CB839 induced oxidative stress in PDAC cells, along with cell death and cell cycle arrest that were again compensated by MCT1 upregulation and forced lactate uptake. Our findings show a novel mechanism by which PDAC cells adapt their metabolism to glutamine scarcity and by which they develop resistance against anticancer treatments based on glutamine uptake/metabolism inhibition.

Expression and role of the immune checkpoint regulator PD-L1 in the tumor-stroma interplay of pancreatic ductal adenocarcinoma

Introduction

Immune checkpoint inhibitors (ICI), e.g., targeting programmed cell death protein 1-ligand 1 (PD-L1) or its receptor PD-1, have markedly improved the therapy of many cancers but so far failed in pancreatic ductal adenocarcinoma (PDAC). Macrophages represent one of the most abundant immune cell populations within the tumor microenvironment (TME) of PDAC being able to either support or restrain tumor progression depending on their phenotype. To better understand treatment failure of PD-L1/PD-1 inhibitors in PDAC, this study examined PD-L1 expression in the context of a dynamic TME in PDAC with a particular focus on the impact of macrophages.

Methods

Formalin-fixed and paraffin embedded tissue samples of primary PDAC tissues and corresponding liver metastases were used for immunohistochemical analyses. Serial sections were stained with antibodies detecting Pan-Cytokeratin, CD68, CD163, CD8, and PD-L1.To investigate whether the PD-1/PD-L1 axis and macrophages contribute to immune escape of PDAC cells, a stroma enriched 3D spheroid coculture model was established in vitro, using different PDAC cell lines and macrophages subtypes as well as CD8+ T cells. Functional and flow cytometry analyses were conducted to characterize cell populations.

Results

Immunohistochemical analyses revealed that PD-L1 is mainly expressed by stroma cells, including macrophages and not PDAC cells in primary PDAC tissues and corresponding liver metastases. Notably, high local abundance of macrophages and strong PD-L1 staining were commonly found at invasion fronts of tumoral lesions between CD8+ T cells and tumor cells. In order to investigate whether PD-L1 expressing macrophages impact the response of PDAC cells to treatment with PD-L1/PD-1 inhibitors, we developed a spheroid model comprising two different PDAC cell lines and different ratios of in vitro differentiated primary M1- or M2-like polarized macrophages. In line with our in situ findings, high PD-L1 expression was observed in macrophages rather than PDAC cells, which was further increased by the presence of PDAC cells. The effector phenotype of co-cultured CD8+ T cells exemplified by expression of activation markers and release of effector molecules was rather enhanced by PDAC macrophage spheroids, particularly with M1-like macrophages compared to mono-culture spheroids. However, this was not associated with enhanced PDAC cell death. ICI treatment with either Durvalumab or Pembrolizumab alone or in combination with Gemcitabine hardly affected the effector phenotype of CD8+ T cells along with PDAC cell death. Thus, despite strong PD-L1 expression in macrophages, ICI treatment did not result in an enhanced activation and cytotoxic phenotype of CD8+ T cells.

Conclusion

Overall, our study revealed novel insights into the interplay of PDAC cells and macrophages in the presence of ICI.

NF-κB/RelA controlled A20 limits TRAIL-induced apoptosis in pancreatic cancer

The emergence of resistance to systemic therapies in pancreatic ductal adenocarcinoma (PDAC) is still a major obstacle in clinical practice. Both, constitutive and inducible NF-κB activity are known as key players in this context. To identify differentially expressed and TRAIL resistance mediating NF-κB target genes, TRAIL sensitive and resistant PDAC cell lines were analyzed by transcriptome assays. In this context, A20 was identified as an NF-κB/RelA inducible target gene. Translational PDAC tissue analysis confirmed the correlation of elevated A20 protein expression with activated RelA expression in PDAC patients. In in vitro experiments, an elevated A20 expression is accompanied by a specific resistance toward TRAIL-mediated apoptosis but not to chemotherapeutic-induced cell death. This TRAIL resistance was attributed to A20´s E3-ligase activity-mediating Zink finger domain. Furthermore, the ubiquitin-binding scaffold protein p62 was identified as indispensable for the TRAIL-mediated apoptosis-inducing pathway affected by A20. The results of this study identify A20 as a possible therapeutic target to affect resistance to TRAIL-induced apoptosis in PDAC cells.

Hepatic myofibroblasts exert immunosuppressive effects independent of the immune checkpoint regulator PD-L1 in liver metastasis of pancreatic ductal adenocarcinoma

Introduction

Pancreatic ductal adenocarcinoma (PDAC) represents the 4^th most common cause of cancer-related deaths in Western countries. Most patients are diagnosed at advanced stages, often already with metastases. The main site of metastasis is the liver and hepatic myofibroblasts (HMF) play a pivotal role in metastatic outgrowth. Immune checkpoint inhibitors (ICI) targeting programmed death ligand 1 (PD-L1) or programmed cell death protein 1 (PD-1) improved treatment of several cancers but not of PDAC. Therefore, this study aimed to better understand the impact of HMF on PD-L1 expression and immune evasion of PDAC cells during liver metastasis.

Methods

Formalin-fixed and paraffin embedded biopsy samples or diagnostic resection specimens from liver metastases of 15 PDAC patients were used for immunohistochemical analyses. Serial sections were stained with antibodies directed against Pan-Cytokeratin, αSMA, CD8, and PD-L1. To investigate whether the PD-1/PD-L1 axis and HMF contribute to immune escape of PDAC liver metastases, a stroma enriched 3D spheroid coculture model was established in vitro, using two different PDAC cell lines, HMF, and CD8⁺ T cells. Here, functional and flow cytometry analyses were conducted.

Results

Immunohistochemical analysis of liver tissue sections of PDAC patients revealed that HMF represent an abundant stroma population in liver metastases, with clear differences in the spatial distribution in small (1500 µm) and large (> 1500 μm) metastases. In the latter, PD-L1 expression was mainly located at the invasion front or evenly distributed, while small metastases either lacked PD-L1 expression or showed mostly weak expression in the center. Double stainings revealed that PD-L1 is predominantly expressed by stromal cells, especially HMF. Small liver metastases with no or low PD-L1 expression comprised more CD8⁺ T cells in the tumor center, while large metastases exhibiting stronger PD-L1 expression comprised less CD8⁺ T cells being mostly located at the invasion front. HMF-enriched spheroid cocultures with different ratios of PDAC cells and HMF well mimicking conditions of hepatic metastases in situ. Here, HMF impaired the release of effector molecules by CD8⁺ T cells and the induction of PDAC cell death, an effect that was dependent on the amount of HMF but also of PDAC cells. ICI treatment led to elevated secretion of distinct CD8⁺ T cell effector molecules but did not increase PDAC cell death under either spheroid condition.

Conclusion

Our findings indicate a spatial reorganization of HMF, CD8⁺ T cells, and PD-L1 expression during progression of PDAC liver metastases. Furthermore, HMF potently impair the effector phenotype of CD8⁺ T cells but the PD-L1/PD-1 axis apparently plays a minor role in this scenario suggesting that immune evasion of PDAC liver metastases relies on other immunosuppressive mechanisms.

Biopsy-Derived Oral Keratinocytes – a Model to Potentially Test for Oral Mucosa Radiation Sensitivity

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Human oral keratinocytes – the key players in radiation mucositis in head and neck cancer treatment – are established ex vivo from patient-derived micro-biopsies.

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Individual radiosensitivity of primary oral keratinocytes is measured by a novel assay for cellular proliferation and spreading.

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The keratinocyte model also supports classical functional assays such as clonogenic survival and DNA double strand repair.

Purpose

To establish stable in vitro growth of keratinocytes from very small biopsy specimens and successfully apply new test systems to determine their radiosensitivity.

Materials and Methods

Oral mucosa biopsies (diameter: 1.7 mm) from 15 subjects were immobilized with custom-made cups onto culture plates. Outgrowing cells were tested for cytokeratin 5/14 and Ki67, expanded, radiated at different doses, and seeded onto circumscribed areas before being allowed to spread centrifugally. In this newly developed spreading assay, cell-covered areas were measured by image analysis. For statistical analysis, a linear mixed regression model was used; additionally, results were correlated to the radiation dose applied. Colony forming efficiency (CFE) was used to validate the results. DNA damage repair was analysed by gammaH2AX and 53BP1 foci quantification using immunofluorescence microscopy 24 h and 96 h after irradiation.

Results

Stable keratinocyte growth continued for up to 7 weeks in 14 biopsies. Cells spread reliably from an initial 16.6 mm² up to a median of 119.2 mm² (range: 54.4–290). Radiated cells spread to only 100.7 mm² (2 Gy; range: 55.3–266.7); 73.2 mm² (4 Gy; 15–240.4); 47 mm² (6 Gy; 2–111.9), and 22.7 mm² (8 Gy; 0–80). Similarly, CFE decreased from 0.223 (0 Gy) to 0.0028 (8 Gy). Using an individual donor as a random factor, cell spread correlated with CFE, where radiation dose was the main driver (decrease by 0.50, adjusted for area). Upon irradiation with 6 Gy, radiation-induced DNA damage was increased after 24 h in all samples, and even after 96 h in 5 out of 7 samples, as detected by a higher number of gammaH2AX/53BP1 foci in irradiated cells (mean 3.7 for 24 h; mean 0.6 for 96 h).

Conclusion

In vitro propagation of keratinocytes derived from a small biopsy is feasible. Radiation impairs cellular migration and proliferation, and the newly described spreading assay allows ranking for cellular radioresistance. The keratinocyte model also supports classical functional assays such as clonogenic survival and DNA double strand repair. The clinical relevance awaits upcoming investigations.

Programmed Death-Ligand 1 (PD-L1) Expression Is Induced by Insulin in Pancreatic Ductal Adenocarcinoma Cells Pointing to Its Role in Immune Checkpoint Control

Type-2 diabetes (T2DM) is a risk factor for the development of pancreatic ductal adenocarcinoma (PDAC) and is characterized by insulin resistance and hyperinsulinemia. Besides the well-known growth-promoting activity of insulin or the other members of the Insulin/Insulin-like Growth factor (IGF) axis, we here describe an inducing effect of insulin on PD-L1 expression in PDAC cells. Treatment of the PDAC cell lines BxPc3, A818-6, and T3M4 with insulin increased PD-L1 expression in a time- and dose dependent fashion, as shown by Western blot and qPCR analysis. siRNA mediated knock-down showed that the effects of insulin on PD-L1 depend on the insulin and IGF receptors (InsR and IGFR, respectively). In addition, a crosstalk of insulin-induced ERK activation and Epidermal Growth Factor (EGF) triggered PD-L1 expression. This involves different mechanisms in the three cell lines including upregulation of InsR-A expression in A818-6 and modulation of the adaptor protein Gab1 in BxPc3 cells. As a consequence of the insulin-induced PD-L1 expression, PDAC cells suppress the proliferation of activated human CD8+ T-cells in coculture experiments. The suppression of CD8+ cell proliferation by insulin-pretreated PDAC cells was reversed by PD-1 blockade with Pembrolizumab or by PD-L1 siRNA. Furthermore, the clinical relevance of these observations was supported by detecting a coexpression of cytoplasmic InsR (characteristic for its activation) and PD-L1 in tumor tissues from PDAC patients. Our findings provide a novel insight into the protumorigenic role of insulin in PDAC. Recognizing the impact of insulin on PD-L1 expression as part of the immune privilege, strategies to interfere with this mechanism could pave the way towards a more efficient immunotherapy of PDAC.

Initiation of Pancreatic Cancer: The Interplay of Hyperglycemia and Macrophages Promotes the Acquisition of Malignancy-Associated Properties in Pancreatic Ductal Epithelial Cells

Pancreatic ductal adenocarcinoma (PDAC) is still one of the most aggressive solid malignancies with a poor prognosis. Obesity and type 2 diabetes mellitus (T2DM) are two major risk factors linked to the development and progression of PDAC, both often characterized by high blood glucose levels. Macrophages represent the main immune cell population in PDAC contributing to PDAC development. It has already been shown that pancreatic ductal epithelial cells (PDEC) undergo epithelial–mesenchymal transition (EMT) when exposed to hyperglycemia or macrophages. Thus, this study aimed to investigate whether concomitant exposure to hyperglycemia and macrophages aggravates EMT-associated alterations in PDEC. Exposure to macrophages and elevated glucose levels (25 mM glucose) impacted gene expression of EMT inducers such as IL-6 and TNF-α as well as EMT transcription factors in benign (H6c7-pBp) and premalignant (H6c7-kras) PDEC. Most strikingly, exposure to hyperglycemic coculture with macrophages promoted downregulation of the epithelial marker E-cadherin, which was associated with an elevated migratory potential of PDEC. While blocking IL-6 activity by tocilizumab only partially reverted the EMT phenotype in H6c7-kras cells, neutralization of TNF-α by etanercept was able to clearly impair EMT-associated properties in premalignant PDEC. Altogether, the current study attributes a role to a T2DM-related hyperglycemic, inflammatory micromilieu in the acquisition of malignancy-associated alterations in premalignant PDEC, thus providing new insights on how metabolic diseases might promote PDAC initiation.

[Weaning from Mechanical Ventilation in Patients with SARS-CoV-2 Infection after Prolonged Mechanical Ventilation - First Experience]

AIM

 With the emergence of a new virus and the associated pandemic, the ICU started to see a brand new kind of patient with severe ARD. As with any disease, sometimes the discontinuation of mechanical ventilation for any reason can be difficult. As a center specializing in weaning patients after prolonged mechanical ventilation, we wanted to compare our results with weaning patients who had prolonged mechanical ventilation for other reasons than those of patients who had prolonged mechanical ventilation due to SARS-CoV-2 infection.

METHODS

 We obtained our data from WeanNet register, the weaning register of the German Institute for Lung Research (ILF). In our analysis, we included only patient data from January until July 2020, which was recorded in our in-house study files.

RESULTS

 Our analysis included data on 28 patients; 11 were treated with prolonged mechanical ventilation due to SARS-CoV-2 pneumonia, 17 had no SARS-CoV-2 infection. 81.2 % of SARS-CoV-2 patients were successfully weaned from invasive ventilator therapy compared to 76.4 % of patients without SARS-CoV-2. Mortality in the SARS-CoV-2 group was 18.2 % compared to 11.8 % in the other group. Patients with SARS-CoV-2 infections were predominantly males with preexisting cardiovascular disease or a history of nicotine abuse. ARDS was the most common cause of respiratory failure which led to primary intubation.

CONCLUSION

 Even though we were only able to analyze a small number of patient histories due to the novelty of the disease, we were able to show that patients with prolonged mechanical ventilation after SARS-CoV-2 infection can be equally successfully weaned compared to patients with prolonged mechanical ventilation due to other diseases. Risk factors for prolonged mechanical ventilation after a severe case of SARS-CoV-2 infection seemed to be male gender, nicotine abuse and cardiovascular disease.

HIV DNA reservoir and elevated PD-1 expression of CD4 T-cell subsets particularly persist in the terminal ileum of HIV-positive patients despite cART

OBJECTIVES

Despite its importance as an HIV anatomic sanctuary, little is known about the characteristics of the HIV reservoir in the terminal ileum (TI). In blood, the immune checkpoint inhibitor programmed-death-1 (PD-1) has been linked to the HIV reservoir and T-cell immune dysfunction. We thus evaluated PD-1 expression and cell-associated HIV DNA in memory CD4 T-cell subsets from TI, peripheral blood (PB) and rectum (RE) of untreated and treated HIV-positive patients to identify associations between PD-1 and HIV reservoir in other sites.

METHODS

Using mononuclear cells from PB, TI and RE of untreated HIV-positive (N = 6), treated (n = 18) HIV-positive and uninfected individuals (n = 16), we identified and sorted distinct memory CD4 T-cell subsets by flow cytometry, quantified their cell-associated HIV DNA using quantitative PCR and assessed PD-1 expression levels using geometric mean fluorescence intensity. Combined HIV-1 RNA in situ hybridization and immunohistochemistry was performed on ileal biopsy sections.

RESULTS

Combined antiretroviral therapy (cART)-treated patients with undetectable HIV RNA and significantly lower levels of HIV DNA in PB showed particularly high PD-1 expression in PB and TI, and high HIV DNA levels in TI, irrespective of clinical characteristics. By contrast, in treatment-naïve patients HIV DNA levels in memory CD4 T-cell subsets were high in PB and TI.

CONCLUSION

Elevated PD-1 expression on memory CD4 T-cells in PB and TI despite treatment points to continuous immune dysfunction and underlines the importance of evaluating immunotherapy in reversing HIV latency and T-cell reconstitution. As HIV DNA particularly persists in TI despite cART, investigating samples from TI is crucial in understanding HIV immunopathogenesis.

Recent insights into the role of L1CAM in cancer initiation and progression

First described as a neuronal cell adhesion molecule, L1CAM was later identified to be present at increased levels in primary tumors and metastases of various types of cancer. Here, we describe the multifaceted roles of L1CAM that are involved in diverse fundamental steps during tumor initiation and progression, as well as in chemoresistance. Recently, Ganesh et al reported that L1CAM identifies metastasis-initiating cells in colorectal carcinoma exhibiting stem-like cell features, increased tumorigenic potential and enhanced chemoresistance. In this review, we highlight recent advances in L1CAM research with particular emphasis on its role in de-differentiation processes and cancer cell stemness supporting the view that L1CAM is a powerful prognostic factor and a suitable target for improved therapy of metastatic and drug-resistant tumors.

NF-κB Dependent Chemokine Signaling in Pancreatic Cancer

Pancreatic cancer is one of the carcinomas with the worst prognoses, as shown by its five-year survival rate of 9%. Although there have been new therapeutic innovations, the effectiveness of these therapies is still limited, resulting in pancreatic ductal adenocarcinoma (PDAC) becoming the second leading cause of cancer-related death in 2020 in the US. In addition to tumor cell intrinsic resistance mechanisms, this disease exhibits a complex stroma consisting of fibroblasts, immune cells, neuronal and vascular cells, along with extracellular matrix, all conferring therapeutic resistance by several mechanisms. The NF-κB pathway is involved in both the tumor cell-intrinsic and microenvironment-mediated therapeutic resistance by regulating the transcription of a plethora of target genes. These genes are involved in nearly all scenarios described as the hallmarks of cancer. In addition to classical regulators of apoptosis, NF-κB regulates the expression of chemokines and their receptors, both in the tumor cells and in cells of the microenvironment. These chemokines mediate autocrine and paracrine loops among tumor cells but also cross-signaling between tumor cells and the stroma. In this review, we will focus on NF-κB-mediated chemokine signaling, with an emphasis on therapy resistance in pancreatic cancer.

Metastasis of pancreatic cancer: An uninflamed liver micromilieu controls cell growth and cancer stem cell properties by oxidative phosphorylation in pancreatic ductal epithelial cells

Pancreatic ductal adenocarcinoma (PDAC) is commonly diagnosed when liver metastases already emerged. We recently demonstrated that hepatic stromal cells determine the dormancy status along with cancer stem cell (CSC) properties of pancreatic ductal epithelial cells (PDECs) during metastasis. This study investigated the influence of the hepatic microenvironment - and its inflammatory status - on metabolic alterations and how these impact cell growth and CSC-characteristics of PDECs. Coculture with hepatic stellate cells (HSCs), simulating a physiological liver stroma, but not with hepatic myofibroblasts (HMFs) representing liver inflammation promoted expression of Succinate Dehydrogenase subunit B (SDHB) and an oxidative metabolism along with a quiescent phenotype in PDECs. SiRNA-mediated SDHB knockdown increased cell growth and CSC-properties. Moreover, liver micrometastases of tumor bearing KPC mice strongly expressed SDHB while expression of the CSC-marker Nestin was exclusively found in macrometastases. Consistently, RNA-sequencing and in silico modeling revealed significantly altered metabolic fluxes and enhanced SDH activity predominantly in premalignant PDECs in the presence of HSC compared to HMF. Overall, these data emphasize that the hepatic microenvironment determines the metabolism of disseminated PDECs thereby controlling cell growth and CSC-properties during liver metastasis.

Alveolar capillary dysplasia with left heart obstruction - rare but lethal

Alveolar capillary dysplasia (ACD) is a rare neonatal lung disease characterized anatomically by a defective and hypoplastic development of pulmonary alveoli leading to persistent pulmonary hypertension (PPHN) and finally lethal respiratory failure. It is often associated with congenital left heart obstruction. Given the fatal prognosis an early diagnosis is important. However, due to the fast onset of PPHN in neonates and lack of pathognomonic signs for its cause, safe and fast detection of ACD is challenging. Therefore, following the exclusion of cardiac and common pulmonary causes, lung biopsy becomes essential for diagnosis.We hereby report a case of ACD with atrial septal defect type one and hypoplastic aortic arch with an ante-mortem diagnosis and discuss the current state of medicine in relation to ACD.

The antioxidant transcription factor Nrf2 modulates the stress response and phenotype of malignant as well as premalignant pancreatic ductal epithelial cells by inducing expression of the ATF3 splicing variant ΔZip2

Pancreatic ductal adenocarcinoma (PDAC) exhibits one of the worst survival rates of all cancers. While death rates show declining trends in the majority of cancers, PDAC registers rising rates. Based on the recently described crosstalk between TGF-β1 and Nrf2 in the PDAC development, the involvement of ATF3 and its splice variant ΔZip2 in TGF-β1- and Nrf2-driven pancreatic tumorigenesis was investigated. As demonstrated here, PDAC (Panc1, T3M4) cells or premalignant H6c7 pancreatic ductal epithelial cells differentially express ΔZip2- and ATF3, relating to stronger Nrf2 activity seen in Panc1 cells and TGF-ß1 activity in T3M4 or H6c7 cells, respectively. Treatment with the electrophile/oxidative stress inducer tBHQ or the cytostatic drug gemcitabine strongly elevated ΔZip2 expression in a Nrf2-dependent fashion. The differential expression of ATF3 and ΔZip2 in response to Nrf2 and TGF-ß1 relates to differential ATF3-gene promoter usage, giving rise of distinct splice variants. Nrf2-dependent ΔZip2 expression confers resistance against gemcitabine-induced apoptosis, only partially relating to interference with ATF3 and its proapoptotic activity, e.g., through CHOP-expression. In fact, ΔZip2 autonomously activates expression of cIAP anti-apoptotic proteins. Moreover, ΔZip2 favors and ATF3 suppresses growth and clonal expansion of PDAC cells, again partially independent of each other. Using a Panc1 tumor xenograft model in SCID-beige mice, the opposite activities of ATF3 and ΔZip2 on tumor-growth and chemoresistance were verified in vivo. Immunohistochemical analyses confirmed ΔZip2 and Nrf2 coexpression in cancerous and PanIN structures of human PDAC and chronic pancreatitis tissues, respectively, which to some extent was reciprocal to ATF3 expression. It is concluded that depending on selective ATF3-gene promoter usage by Nrf2, the ΔZip2 expression is induced in response to electrophile/oxidative (here through tBHQ) and xenobiotic (here through gemcitabine) stress, providing apoptosis protection and growth advantages to pancreatic ductal epithelial cells. This condition may substantially add to pancreatic carcinogenesis driven by chronic inflammation.

Electrochemical initiation of electron-catalyzed phenanthridine synthesis by trifluoromethylation of isonitriles

Electrochemical initiation of the trifluoromethylation of biaryl isonitriles verifies the electron's catalytic character in the examined cascade reaction.

Diabetes as risk factor for pancreatic cancer: Hyperglycemia promotes epithelial-mesenchymal-transition and stem cell properties in pancreatic ductal epithelial cells

Type 2 diabetes mellitus (T2DM) is associated with hyperglycemia and a risk to develop pancreatic ductal adenocarcinoma (PDAC), one of the most fatal malignancies. Cancer stem cells (CSC) are essential for initiation and maintenance of tumors, and acquisition of CSC-features is linked to epithelial-mesenchymal-transition (EMT). The present study investigated whether hyperglycemia promotes EMT and CSC-features in premalignant and malignant pancreatic ductal epithelial cells (PDEC). Under normoglycemia (5 mM d-glucose), Panc1 PDAC cells but not premalignant H6c7-kras cells exhibited a mesenchymal phenotype along with pronounced colony formation. While hyperglycemia (25 mM d-glucose) did not impact the mesenchymal phenotype of Panc1 cells, CSC-properties were aggravated exemplified by increased Nanog expression and Nanog-dependent formation of holo- and meroclones. In H6c7-kras cells, high glucose increased secretion of Transforming-Growth-Factor-beta1 (TGF-β1) as well as TGF-β1 signaling, and in a TGF-β1-dependent manner reduced E-cadherin expression, increased Nestin expression and number of meroclones. Finally, reduced E-cadherin expression was detected in pancreatic ducts of hyperglycemic but not normoglycemic mice. These data suggest that hyperglycemia promotes the acquisition of mesenchymal and CSC-properties in PDEC by activating TGF-β signaling and might explain how T2DM facilitates pancreatic tumorigenesis.

The hepatic microenvironment essentially determines tumor cell dormancy and metastatic outgrowth of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is often diagnosed when liver metastases already emerged. This study elucidated the impact of hepatic stromal cells on growth behavior of premalignant and malignant pancreatic ductal epithelial cells (PDECs). Liver sections of tumor-bearing KPC mice comprised micrometastases displaying low proliferation located in an unobtrusive hepatic microenvironment whereas macrometastases containing more proliferating cells were surrounded by hepatic myofibroblasts (HMFs). In an age-related syngeneic PDAC mouse model livers with signs of age-related inflammation exhibited significantly more proliferating disseminated tumor cells (DTCs) and micrometastases despite comparable primary tumor growth and DTC numbers. Hepatic stellate cells (HSC), representing a physiologic liver stroma, promoted an IL-8 mediated quiescence-associated phenotype (QAP) of PDECs in coculture. QAP included flattened cell morphology, Ki67-negativity and reduced proliferation, elevated senescence-associated β galactosidase activity and diminished p-Erk/p-p38-ratio. In contrast, proliferation of PDECs was enhanced by VEGF in the presence of HMF. Switching the micromilieu from HSC to HMF or blocking VEGF reversed QAP in PDECs. This study demonstrates how HSCs induce and maintain a reversible QAP in disseminated PDAC cells, while inflammatory HMFs foster QAP reversal and metastatic outgrowth. Overall, the importance of the hepatic microenvironment in induction and reversal of dormancy during PDAC metastasis is emphasized.

Role of CCL20 mediated immune cell recruitment in NF-κB mediated TRAIL resistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest cancers. From a clinical view, the transcription factor NF-κB is of particular importance, since this pathway confers apoptosis resistance and limits drug efficacy. Whereas the role of the most abundant NF-κB subunit p65/RelA in therapeutic resistance is well documented, only little knowledge of the RelA downstream targets and their functional relevance in TRAIL mediated apoptosis in PDAC is available. In the present study TRAIL resistant and sensitive PDAC cell lines were analyzed for differentially expressed RelA target genes, to define RelA downstream targets mediating TRAIL resistance. The most upregulated target gene was then further functionally characterized. Unbiased genome-wide expression analysis demonstrated that the chemokine CCL20 represents the strongest TRAIL inducible direct RelA target gene in resistant PDAC cells. Unexpectedly, targeting CCL20 by siRNA, blocking antibodies or by downregulation of the sole CCL20 receptor CCR6 had no effect on PDAC cell death or cancer cell migration, arguing against an autocrine role of CCL20 in PDAC. However, by using an ex vivo indirect co-culture system we were able to show that CCL20 acts paracrine to recruit immune cells. Importantly, CCL20-recruited immune cells further increase TRAIL resistance of CCL20-producing PDAC cells. In conclusion, our data show a functional role of a RelA-CCL20 pathway in PDAC TRAIL resistance. We demonstrate how the therapy-induced cross-talk of cancer cells with immune cells affects treatment responses, knowledge needed to tailor novel bi-specific treatments, which target tumor cell as well as immune cells.

The anti-oxidative transcription factor Nuclear factor E2 related factor-2 (Nrf2) counteracts TGF-β1 mediated growth inhibition of pancreatic ductal epithelial cells -Nrf2 as determinant of pro-tumorigenic functions of TGF-β1

BACKGROUND

Nuclear factor E2 related factor-2 (Nrf2) is an oxidative stress inducible transcription factor being essential in regulating cell homeostasis. Thus, acute induction of Nrf2 in epithelial cells exposed to inflammation confers protection from oxidative cell damage and mutagenesis supporting an anti-tumorigenic role for Nrf2. However, pancreatic ductal adenocarcinoma (PDAC) is characterized by persistent Nrf2 activity conferring therapy resistance which points to a pro-tumorigenic role of Nrf2. A similar dichotomous role in tumorigenesis is described for the Transforming Growth Factor-beta 1 (TGF-β1). The present study therefore aimed at elucidating whether the switch of Nrf2 function towards a tumor promoting one relates to the modulation of TGF-β1 induced cell responses and whether this might occur early in PDAC development.

METHODS

In situ analysis comprised immunohistochemical stainings of activated (phosphorylated) Nrf2 and Ki67 in pancreatic tissues containing normal ducts and pancreatic intraepithelial neoplasia (PanINs). In vitro, Nrf2 levels in benign (H6c7-pBp), premalignant (H6c7-kras) and malignant (Colo357) pancreatic ductal epithelial cells were modulated by Nrf2 specific siRNA or Nrf2 overexpression. Then, the effect of Nrf2 alone and in combination with TGF-β1 on cell growth and survival was investigated by cell counting, Ki67 staining and apoptosis assays. The underlying cell signaling was investigated by western blotting. Statistical analysis was performed by Shapiro-Wilk test for normal distribution. Parametric data were analyzed by one-way ANOVA, while non-parametric data were analyzed by Kruskal-Wallis one-way ANOVA on ranks.

RESULTS

Significantly elevated expression of activated Nrf2 and Ki67 could be detected in PanINs but not in normal pancreatic ductal epithelium. While the effect of Nrf2 on basal cell growth of H6c7-pBp, H6c7-kras and Colo357 cells was minor, it clearly attenuated the growth inhibiting effects of TGF-β1 in all cell lines. This enhanced Nrf2-mediated cell survival was predominantly based on an enhanced proliferative activity. Accordingly, expression of p21 expression along with expression of phospho-p38 and phospho-Smad3 was diminished whereas Erk-phosphorylation was enhanced under these conditions.

CONCLUSIONS

Overall, our data demonstrate that Nrf2 being elevated in early precursor lesions counteracts the growth inhibiting function of TGF-β1 already in benign and premalignant pancreatic ductal epithelial cells. This could represent one fundamental mechanism underlying the functional switch of both- TGF-β1 and Nrf2 - which may manifest already in early stages of PDAC development.

The Crosstalk between Nrf2 and TGF-β1 in the Epithelial-Mesenchymal Transition of Pancreatic Duct Epithelial Cells

Nrf2 and TGF-β1 both affect tumorigenesis in a dual fashion, either by preventing carcinogen induced carcinogenesis and suppressing tumor growth, respectively, or by conferring cytoprotection and invasiveness to tumor cells during malignant transformation. Given the involvement of Nrf2 and TGF-β1 in the adaptation of epithelial cells to persistent inflammatory stress, e.g. of the pancreatic duct epithelium during chronic pancreatitis, a crosstalk between Nrf2 and TGF-β1 can be envisaged. By using premalignant human pancreatic duct cells (HPDE) and the pancreatic ductal adenocarcinoma cell line Colo357, we could show that Nrf2 and TGF-β1 independently but additively conferred an invasive phenotype to HPDE cells, whereas acting synergistically in Colo357 cells. This was accompanied by differential regulation of EMT markers like vimentin, Slug, L1CAM and E-cadherin. Nrf2 activation suppressed E-cadherin expression through an as yet unidentified ARE related site in the E-cadherin promoter, attenuated TGF-β1 induced Smad2/3-activity and enhanced JNK-signaling. In Colo357 cells, TGF-β1 itself was capable of inducing Nrf2 whereas in HPDE cells TGF-β1 per-se did not affect Nrf2 activity, but enhanced Nrf2 induction by tBHQ. In Colo357, but not in HPDE cells, the effects of TGF-β1 on invasion were sensitive to Nrf2 knock-down. In both cell lines, E-cadherin re-expression inhibited the proinvasive effect of Nrf2. Thus, the increased invasion of both cell lines relates to the Nrf2-dependent downregulation of E-cadherin expression. In line, immunohistochemistry analysis of human pancreatic intraepithelial neoplasias in pancreatic tissues from chronic pancreatitis patients revealed strong Nrf2 activity already in premalignant epithelial duct cells, accompanied by partial loss of E-cadherin expression. Our findings indicate that Nrf2 and TGF-β1 both contribute to malignant transformation through distinct EMT related mechanisms accounting for an invasive phenotype. Provided a crosstalk between both pathways, Nrf2 and TGF-β1 mutually promote their tumorigenic potential, a condition manifesting already at an early stage during inflammation induced carcinogenesis of the pancreas.

Abstract B114: c-Rel is a critical mediator of NF-κB dependent TRAIL resistance of pancreatic cancer cells

NF-κB has been shown to be critical for resistance of pancreatic ductal adenocarcinoma (PDAC) against chemotherapeutic drug and death receptor induced apoptosis, but little is known about the role of the c-Rel subunit.

In the present study, by analysis of genome-wide patterns of c-Rel dependent gene expression we were able to establish c-Rel as a critical regulator of TRAIL induced apoptosis in PDAC. Transfection with siRNA against c-Rel sensitized the TRAIL resistant PDAC cells and EMSA revealed that c-Rel is part of the TRAIL inducible NF-κB complex. Array analysis identified NFATc2 as a critical downstream target of c-Rel in PDAC. In line, siRNA targeting c-Rel strongly reduced TRAIL induced NFATc2 activity and siRNA targeting NFATc2 sensitized PDAC cells against TRAIL induced apoptosis. Finally, TRAIL induced expression of COX-2 was diminished through siRNA targeting c-Rel or NFATc2 and pharmacological inhibition of COX-2 with celecoxib enhanced TRAIL apoptosis.

In conclusion, we were able to delineate a novel c-Rel, NFATc2 and COX-2 dependent anti-apoptotic signalling pathway in PDAC with broad clinical implications for pharmaceutical intervention strategies.

Citation Format: Claudia Geismann, Frauke Grohmann, Robert Häsler, Philip Rosenstiel, Günter Schneider, Sebastian Zeissig, Stefan Schreiber, Heiner Schäfer, Alexander Arlt. c-Rel is a critical mediator of NF-κB dependent TRAIL resistance of pancreatic cancer cells. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B114.

CD4+ T cells potently induce epithelial-mesenchymal-transition in premalignant and malignant pancreatic ductal epithelial cells-novel implications of CD4+ T cells in pancreatic cancer development

Chronic pancreatitis (CP) is a risk factor of pancreatic ductal adenocarcinoma (PDAC) and characterized by a pronounced desmoplastic reaction with CD4⁺ T cells accounting for the majority of the stromal T cell infiltrate. Epithelial-mesenchymal-transition (EMT) is a critical process for metastasis by which epithelial/carcinoma cells become enabled to disseminate probably prior to tumor formation. To investigate whether CD4⁺ T cells induce EMT in human pancreatic ductal epithelial cells, premalignant H6c7 cells were mono- or co-cultured with human CD4⁺CD25⁺CD127^-CD49d^- regulatory T cells (T-regs) or CD4⁺CD25^- T-effector cells (T-effs) being isolated by negative magnetic bead separation from blood of healthy donors. Particularly in the presence of activated T-effs, H6c7 cells acquired a spindle-shaped morphology, reduced E-cadherin expression, and elevated expression of the mesenchymal proteins vimentin, L1CAM, and ZEB-1. This was accompanied by an increased invasive behavior. Moreover, activated T-effs exerted similar effects in the PDAC cell line T3M4. Blocking of TNF-α and IL-6 being released at greater amounts into supernatants during co-cultures with activated T-effs attenuated the EMT-associated alterations in H6c7 cells. Supporting these findings, EMT-associated alterations (exemplified by reduced E-cadherin expression and enhanced expression of vimentin and L1CAM) were predominantly detected in ductal epithelium of CP tissues surrounded by a dense stroma enriched with CD4⁺ T cells. Overall this study points to a novel role of CD4⁺ T cells beyond their immune function in pancreatic tumorigenesis and underscores the view that EMT induction in pancreatic ductal epithelial cells represents an early event in PDAC development being essentially promoted by inflammatory processes.

How two sites of inflammation promote carcinogenesis: The role of macrophages in inflammation associated carcinogenesis

We recently reported that anti-inflammatory macrophages contribute to the initiation of colorectal carcinogenesis in IBD patients by inducing epithelial-mesenchymal-transition associated alterations in colonic epithelial cells. In this process, TGFβ1 dependent upregulation of the adhesion molecule L1CAM is one key event, paving the way to colitis associated tumorigenesis and metastatic spread.

Abstract 2273: c-Rel is a critical mediator of NF-κB-dependent apoptosis resistance of pancreatic cancer cells against TRAIL

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest malignancies with an overall life expectancy of six months despite palliative radio-chemotherapy. The transcription factor NF-κB has been shown to be a critical component of dysregulated transcription factor activity conferring this profound resistance against chemotherapeutic drugs and death receptor induced apoptosis. Despite extensive data on the role of the most abundant NF-κB subunit p65/RelA in PDAC apoptosis control, only little knowledge of the role of the subunit c-Rel in solid cancers exists. In the present study, three pancreatic carcinoma cell lines (Panc1, Patu8988t, MiaPaca2) were analysed for the role of c-Rel in resistance against TRAIL induced apoptosis. TRAIL resistant Panc1 and Patu8988 cells exhibit a strong TRAIL inducible NF-κB activity, whereas TRAIL sensitive MiaPaca2 cells displayed only a small increase in NF-κB binding activity. Transfection with siRNA against the c-Rel subunit of NF-κB sensitized the TRAIL resistant cells in a comparable fashion like siRNA targeting the p65/RelA subunit. Gel shift analysis revealed that together with the p65/RelA subunit, c-Rel is part of the TRAIL inducible NF-κB complex in PDAC. Array analysis results suggested NFATc2 as a c-Rel target gene that is one of the 15 strongest TRAIL inducible genes in apoptosis-resistant Panc1 cells. siRNA targeting c-Rel strongly reduced TRAIL induced NFATc2 activity in TRAIL resistant PDAC cells. Furthermore siRNA targeting NFATc2 sensitized these PDAC cells against TRAIL induced apoptosis. Finally, TRAIL induced expression of COX-2 was strongly reduced through siRNA targeting c-Rel or NFATc2 and pharmacological inhibition of COX-2 with celecoxib strongly increased TRAIL apoptosis.

In conclusion, c-Rel is a critical mediator of NF-κB dependent anti-apoptotic signalling in PDAC through activation of NFATc2 and COX-2.

Citation Format: Claudia Geismann, Frauke Grohmann, Gabriele Wirths, Susanne Sebens, Anita Dreher, Robert Häsler, Sebastian Zeissig, Stefan Schreiber, Philip Rosenstiel, Heiner Schäfer, Alexander Arlt. c-Rel is a critical mediator of NF-κB-dependent apoptosis resistance of pancreatic cancer cells against TRAIL. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2273. doi:10.1158/1538-7445.AM2014-2273

Cytoprotection "gone astray": Nrf2 and its role in cancer

Nrf2 has gained great attention with respect to its pivotal role in cell and tissue protection. Primarily defending cells against metabolic, xenobiotic and oxidative stress, Nrf2 is essential for maintaining tissue integrity. Owing to these functions, Nrf2 is regarded as a promising drug target in the chemoprevention of diseases, including cancer. However, much evidence has accumulated that the beneficial role of Nrf2 in cancer prevention essentially depends on the tight control of its activity. In fact, the deregulation of Nrf2 is a critical determinant in oncogenesis and found in many types of cancer. Therefore, amplified Nrf2 activity has profound effects on the phenotype of tumor cells, including radio/chemoresistance, apoptosis protection, invasiveness, antisenescence, autophagy deficiency, and angiogenicity. The deregulation of Nrf2 can result from various epigenetic and genetic alterations directly affecting Nrf2 control or from the complex interplay of Nrf2 with numerous oncogenic signaling pathways. Additionally, alterations of the cellular environment, eg, during inflammation, contribute to Nrf2 deregulation and its persistent activation. Therefore, the status of Nrf2 as anti- or protumorigenic is defined by many different modalities. A better understanding of these modalities is essential for the safe use of Nrf2 as an activation target for chemoprevention on the one hand and as an inhibition target in cancer therapy on the other. The present review mainly addresses the conditions that promote the oncogenic function of Nrf2 and the resulting consequences providing the rationale for using Nrf2 as a target structure in cancer therapy.

Coherent structural dynamics of a prototypical charge-density-wave-to-metal transition

Using femtosecond time-resolved x-ray diffraction, we directly monitor the coherent lattice dynamics through an ultrafast charge-density-wave-to-metal transition in the prototypical Peierls system K(0.3)MoO(3) over a wide range of relevant excitation fluences. While in the low fluence regime we directly follow the structural dynamics associated with the collective amplitude mode; for fluences above the melting threshold of the electronic density modulation we observe a transient recovery of the periodic lattice distortion. We can describe these structural dynamics as a motion along the coordinate of the Peierls distortion triggered by the prompt collapse of electronic order after photoexcitation. The results indicate that the dynamics of a structural symmetry-breaking transition are determined by a high-symmetry excited state potential energy surface distinct from that of the initial low-temperature state.

M1 and M2: there is no "good" and "bad"-How macrophages promote malignancy-associated features in tumorigenesis

We recently identified tumor-associated macrophages from pancreatic ductal adenocarcinoma sharing pro- and anti-inflammatory characteristics. Already in residence in the setting of chronic pancreatitis, local macrophages confer malignancy-associated features to premalignant pancreatic ductal epithelial cells by both promoting and inhibiting inflammation, either of which can foster malignant conversion. Our findings support the concept that contrasting modes of inflammation can promote tumorigenesis.

The fatal alliance of cancer and T cells: How pancreatic tumor cells gather immunosuppressive T cells

Immune evasion is a hallmark of cancer. We recently identified the adhesion molecule L1CAM as biomarker of pancreatic ductal adenocarcinoma (PDAC) associated with poor prognosis. During inflammation-associated carcinogenesis, L1CAM drives the enrichment of highly immunosuppressive CD4⁺CD25^-CD69⁺ T cells. Thus, L1CAM may serve as a target in immunomodulatory therapy for PDAC.