Publications by authors named "Silke Lassmann"

67 Publications

Transitioning the Molecular Tumor Board from Proof of Concept to Clinical Routine: A German Single-Center Analysis.

Cancers (Basel) 2021 Mar 8;13(5). Epub 2021 Mar 8.

Department of Medicine I, Medical Center, University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany.

Molecular precision oncology faces two major challenges: first, to identify relevant and actionable molecular variants in a rapidly changing field and second, to provide access to a broad patient population. Here, we report a four-year experience of the Molecular Tumor Board (MTB) of the Comprehensive Cancer Center Freiburg (Germany) including workflows and process optimizations. This retrospective single-center study includes data on 488 patients enrolled in the MTB from February 2015 through December 2018. Recommendations include individual molecular diagnostics, molecular stratified therapies, assessment of treatment adherence and patient outcomes including overall survival. The majority of MTB patients presented with stage IV oncologic malignancies (90.6%) and underwent an average of 2.1 previous lines of therapy. Individual diagnostic recommendations were given to 487 patients (99.8%). A treatment recommendation was given in 264 of all cases (54.1%) which included a molecularly matched treatment in 212 patients (43.4%). The 264 treatment recommendations were implemented in 76 patients (28.8%). Stable disease was observed in 19 patients (25.0%), 17 had partial response (22.4%) and five showed a complete remission (6.6%). An objective response was achieved in 28.9% of cases with implemented recommendations and for 4.5% of the total population (22 of 488 patients). By optimizing the MTB workflow, case-discussions per session increased significantly while treatment adherence and outcome remained stable over time. Our data demonstrate the feasibility and effectiveness of molecular-guided personalized therapy for cancer patients in a clinical routine setting showing a low but robust and durable disease control rate over time.
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http://dx.doi.org/10.3390/cancers13051151DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7962829PMC
March 2021

Integrating quantitative proteomics with accurate genome profiling of transcription factors by greenCUT&RUN.

Nucleic Acids Res 2021 Feb 1. Epub 2021 Feb 1.

Department of Urology, Medical Center-University of Freiburg, 79016 Freiburg, Germany.

Genome-wide localization of chromatin and transcription regulators can be detected by a variety of techniques. Here, we describe a novel method 'greenCUT&RUN' for genome-wide profiling of transcription regulators, which has a very high sensitivity, resolution, accuracy and reproducibility, whilst assuring specificity. Our strategy begins with tagging of the protein of interest with GFP and utilizes a GFP-specific nanobody fused to MNase to profile genome-wide binding events. By using a GFP-nanobody the greenCUT&RUN approach eliminates antibody dependency and variability. Robust genomic profiles were obtained with greenCUT&RUN, which are accurate and unbiased towards open chromatin. By integrating greenCUT&RUN with nanobody-based affinity purification mass spectrometry, 'piggy-back' DNA binding events can be identified on a genomic scale. The unique design of greenCUT&RUN grants target protein flexibility and yields high resolution footprints. In addition, greenCUT&RUN allows rapid profiling of mutants of chromatin and transcription proteins. In conclusion, greenCUT&RUN is a widely applicable and versatile genome-mapping technique.
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http://dx.doi.org/10.1093/nar/gkab038DOI Listing
February 2021

The Clinically Used Iron Chelator Deferasirox Is an Inhibitor of Epigenetic JumonjiC Domain-Containing Histone Demethylases.

ACS Chem Biol 2019 08 19;14(8):1737-1750. Epub 2019 Jul 19.

Institute of Pharmaceutical Sciences , Albert-Ludwigs-Universität Freiburg , Albertstraße 25 , 79104 Freiburg i.Br. , Germany.

Fe(II)- and 2-oxoglutarate (2OG)-dependent JumonjiC domain-containing histone demethylases (JmjC KDMs) are "epigenetic eraser" enzymes involved in the regulation of gene expression and are emerging drug targets in oncology. We screened a set of clinically used iron chelators and report that they potently inhibit JMJD2A (KDM4A) . Mode of action investigations revealed that one compound, deferasirox, is a active site-binding inhibitor as shown by kinetic and spectroscopic studies. Synthesis of derivatives with improved cell permeability resulted in significant upregulation of histone trimethylation and potent cancer cell growth inhibition. Deferasirox was also found to inhibit human 2OG-dependent hypoxia inducible factor prolyl hydroxylase activity. Therapeutic effects of clinically used deferasirox may thus involve transcriptional regulation through 2OG oxygenase inhibition. Deferasirox might provide a useful starting point for the development of novel anticancer drugs targeting 2OG oxygenases and a valuable tool compound for investigations of KDM function.
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http://dx.doi.org/10.1021/acschembio.9b00289DOI Listing
August 2019

Variant classification in precision oncology.

Int J Cancer 2019 12 21;145(11):2996-3010. Epub 2019 May 21.

Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.

Next-generation sequencing has become a cornerstone of therapy guidance in cancer precision medicine and an indispensable research tool in translational oncology. Its rapidly increasing use during the last decade has expanded the options for targeted tumor therapies, and molecular tumor boards have grown accordingly. However, with increasing detection of genetic alterations, their interpretation has become more complex and error-prone, potentially introducing biases and reducing benefits in clinical practice. To facilitate interdisciplinary discussions of genetic alterations for treatment stratification between pathologists, oncologists, bioinformaticians, genetic counselors and medical scientists in specialized molecular tumor boards, several systems for the classification of variants detected by large-scale sequencing have been proposed. We review three recent and commonly applied classifications and discuss their individual strengths and weaknesses. Comparison of the classifications underlines the need for a clinically useful and universally applicable variant reporting system, which will be instrumental for efficient decision making based on sequencing analysis in oncology. Integrating these data, we propose a generalizable classification concept featuring a conservative and a more progressive scheme, which can be readily applied in a clinical setting.
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http://dx.doi.org/10.1002/ijc.32358DOI Listing
December 2019

Surgical management of lower-grade glioma in the spotlight of the 2016 WHO classification system.

J Neurooncol 2019 Jan 22;141(1):223-233. Epub 2018 Nov 22.

Department of Neurosurgery, Medical Center, Freiburg, Germany.

Purpose: According to the 2016 WHO classification lower-grade gliomas consist of three groups: IDH-mutated and 1p/19q co-deleted, IDH-mutated and IDH-wildtype tumors. The aim of this study was to evaluate the impact of surgical therapy for lower-grade gliomas with a particular focus on the molecular subgroups.

Methods: This is a bi-centric retrospective analysis including 299 patients, who underwent treatment for lower-grade glioma between 1990 and 2016. All tumors were re-classified according to the 2016 WHO classification. Data concerning baseline and tumor characteristics, overall survival, different treatment modalities and functional outcome were analyzed.

Results: A total of 112 (37.5%) patients with IDH-mutation and 1p/19q co-deletetion, 86 (28.8%) patients with IDH-mutation and 101 (33.8%) patients with IDH-wildtype tumors were identified. The median overall survival (mOS) differed significantly between the groups (p < 0.001). Surgical resection was performed in 226 patients and showed significantly improved mOS compared to the biopsy group (p = 0.001). Gross total resection (GTR) was associated with better survival (p = 0.007) in the whole cohort as well as in the IDH-mutated and IDH-wildtype groups compared to partial resection or biopsy. IDH-wildtype patients presented a significant survival benefit after combined radio-chemotherapy compared to radio- or chemotherapy alone (p = 0.02). Good clinical status (NANO) was associated with longer OS (p = 0.001).

Conclusion: The impact of surgical treatment on the outcome of lower-grade gliomas depends to a great extent on the molecular subtype of the tumors. Patients with more aggressive tumors (IDH-wildtype) seem to profit from more intensive treatment like GTR, multiple resections and combined radio-/chemotherapy.
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http://dx.doi.org/10.1007/s11060-018-03030-wDOI Listing
January 2019

Personalized Clinical Decision Making Through Implementation of a Molecular Tumor Board: A German Single-Center Experience.

JCO Precis Oncol 2018 16;2. Epub 2018 Aug 16.

University of Freiburg, Freiburg; , , , , , , , , , and , German Cancer Consortium, partner site Freiburg, and German Cancer Research Center, Heidelberg; , Augsburg Medical Center, Augsburg; and , University of Lübeck, Lübeck, Germany.

Purpose: Dramatic advances in our understanding of the molecular pathophysiology of cancer, along with a rapidly expanding portfolio of molecular targeted drugs, have led to a paradigm shift toward personalized, biomarker-driven cancer treatment. Here, we report the 2-year experience of the Comprehensive Cancer Center Freiburg Molecular Tumor Board (MTB), one of the first interdisciplinary molecular tumor conferences established in Europe. The role of the MTB is to recommend personalized therapy for patients with cancer beyond standard-of-care treatment.

Methods: This retrospective case series includes 198 patients discussed from March 2015 through February 2017. The MTB guided individual molecular diagnostics, assessed evidence of actionability of molecular alterations, and provided therapy recommendations, including approved and off-label treatments as well as available matched clinical trials.

Results: The majority of patients had metastatic solid tumors (73.7%), mostly progressive (77.3%) after a mean of 2.0 lines of standard treatment. Diagnostic recommendations resulted in 867 molecular diagnostic tests for 172 patients (five per case), including exome analysis in 36 cases (18.2%). With a median turnaround time of 28 days, treatment recommendations were given to 104 patients (52.5%). These included single-agent targeted therapies (42.3%), checkpoint inhibitors (37.5%), and combination therapies (18.3%). Treatment recommendations were implemented in 33 of 104 patients (31.7%), of whom 19 (57.6%) showed stable disease or partial response, including 14 patients (7.1% of the entire population) receiving off-label treatments.

Conclusion: Personalized extended molecular-guided patient care is effective for a small but clinically meaningful proportion of patients in challenging clinical situations. Limited access to targeted drugs, lack of trials, and submission at late disease stage prevents broader applicability, whereas genome-wide analyses are not a strict requirement for predictive molecular testing.
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http://dx.doi.org/10.1200/PO.18.00105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7446498PMC
August 2018

MR-spectroscopic imaging of glial tumors in the spotlight of the 2016 WHO classification.

J Neurooncol 2018 Sep 27;139(2):431-440. Epub 2018 Apr 27.

Department of Neurosurgery, Medical Center - University of Freiburg, Breisacher Straße 64, 79106, Freiburg, Germany.

Background: The purpose of this study is to map spatial metabolite differences across three molecular subgroups of glial tumors, defined by the IDH1/2 mutation and 1p19q-co-deletion, using magnetic resonance spectroscopy. This work reports a new MR spectroscopy based classification algorithm by applying a radiomics analytics pipeline.

Materials: 65 patients received anatomical and chemical shift imaging (5 × 5 × 20 mm voxel size). Tumor regions were segmented and registered to corresponding spectroscopic voxels. Spectroscopic features were computed (n = 860) in a radiomic approach and selected by a classification algorithm. Finally, a random forest machine-learning model was trained to predict the molecular subtypes.

Results: A cluster analysis identified three robust spectroscopic clusters based on the mean silhouette widths. Molecular subgroups were significantly associated with the computed spectroscopic clusters (Fisher's Exact test p < 0.01). A machine-learning model was trained and validated by public available MRS data (n = 19). The analysis showed an accuracy rate in the Random Forest model by 93.8%.

Conclusions: MR spectroscopy is a robust tool for predicting the molecular subtype in gliomas and adds important diagnostic information to the preoperative diagnostic work-up of glial tumor patients. MR-spectroscopy could improve radiological diagnostics in the future and potentially influence clinical and surgical decisions to improve individual tumor treatment.
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http://dx.doi.org/10.1007/s11060-018-2881-xDOI Listing
September 2018

Specific role of RhoC in tumor invasion and metastasis.

Oncotarget 2017 Oct 16;8(50):87364-87378. Epub 2017 Sep 16.

Institute for Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, Albert-Ludwigs-University, Freiburg, Germany.

Rho GTPases are regulators of many cellular functions and are often dysregulated in cancer. However, the precise role of Rho proteins for tumor development is not well understood. In breast cancer, overexpression of RhoC is linked with poor prognosis. Here, we aim to compare the function of RhoC and its homolog family member RhoA in breast cancer progression. We established stable breast epithelial cell lines with inducible expression of RhoA and RhoC, respectively. Moreover, we made use of Rho-activating bacterial toxins (Cytotoxic Necrotizing Factors) to stimulate the endogenous pool of Rho GTPases in benign breast epithelial cells and simultaneously knocked down specific Rho proteins. Whereas activation of Rho GTPases was sufficient to induce an invasive phenotype in three-dimensional culture systems, overexpression of RhoA or RhoC were not. However, RhoC but not RhoA was required for invasion, whereas RhoA and RhoC equally regulated proliferation. We further identified downstream target genes of RhoC involved in invasion and identified PTGS2 (COX-2) being preferentially upregulated by RhoC. Consistently, the COX-2 inhibitor Celecoxib blocked the invasive phenotype induced by the Rho-activating toxins.
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http://dx.doi.org/10.18632/oncotarget.20957DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5675639PMC
October 2017

Targeting of Cell Surface Proteolysis of Collagen XVII Impedes Squamous Cell Carcinoma Progression.

Mol Ther 2018 01 27;26(1):17-30. Epub 2017 Sep 27.

Department of Dermatology, Medical Center and Faculty of Medicine-University of Freiburg, 79104 Freiburg, Germany. Electronic address:

Squamous cell carcinoma (SCC) is one of the most common skin cancers and causes significant morbidity. Although the expression of the epithelial adhesion molecule collagen XVII (ColXVII) has been linked to SCC invasion, only little is known about its mechanistic contribution. Here, we demonstrate that ColXVII expression is essential for SCC cell proliferation and motility. Moreover, it revealed that particularly the post-translational modification of ColXVII by ectodomain shedding is the major driver of SCC progression, because ectodomain-selective immunostaining was mainly localized at the invasive front of human cutaneous SCCs, and exclusive expression of a non-sheddable ColXVII mutant in SCC-25 cells inhibits their matrix-independent growth and invasiveness. This cell surface proteolysis, which is strongly elevated during SCC invasion and metastasis, releases soluble ectodomains and membrane-anchored endodomains. Both released ColXVII domains play distinct roles in tumor progression: the endodomain induces proliferation and survival, whereas the ectodomain accelerates invasiveness. Furthermore, specific blockage of shedding by monoclonal ColXVII antibodies repressed matrix-independent growth and invasion of SCC cells in organotypic co-cultures. Thus, selective inhibition of ColXVII shedding may offer a promising therapeutic strategy to prevent SCC progression.
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http://dx.doi.org/10.1016/j.ymthe.2017.09.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5763164PMC
January 2018

A new model system identifies epidermal growth factor receptor-human epidermal growth factor receptor 2 (HER2) and HER2-human epidermal growth factor receptor 3 heterodimers as potent inducers of oesophageal epithelial cell invasion.

J Pathol 2017 12 5;243(4):481-495. Epub 2017 Nov 5.

Institute for Surgical Pathology, Medical Centre, University of Freiburg, Freiburg, Germany.

Oesophageal squamous cell carcinomas and oesophageal adenocarcinomas show distinct patterns of ErbB expression and dimers. The functional effects of specific ErbB homodimers or heterodimers on oesophageal (cancer) cell behaviour, particularly invasion during early carcinogenesis, remain unknown. Here, a new cellular model system for controlled activation of epidermal growth factor receptor (EGFR) or human epidermal growth factor receptor 2 (HER2) and EGFR-HER2 or HER2-human epidermal growth factor receptor 3 (HER3) homodimers and heterodimers was studied in non-neoplastic squamous oesophageal epithelial Het-1A cells. EGFR, HER2 and HER3 intracellular domains (ICDs) were fused to dimerization domains (DmrA/DmrA and DmrC), and transduced into Het-1A cells lacking ErbB expression. Dimerization of EGFR, HER2 or EGFR-HER2 and HER2-HER3 ICDs was induced by synthetic ligands (A/A or A/C dimerizers). This was accompanied by phosphorylation of the respective EGFR, HER2 and HER3 ICDs and activation of distinct downstream signalling pathways, such as phospholipase Cγ1, Akt, STAT and Src family kinases. Phenotypically, ErbB dimers caused cell rounding and non-apoptotic blebbing, specifically in EGFR-HER2 and HER2-HER3 heterodimer cells. In a Transwell assay, cell migration velocity was elevated in HER2 dimer cells as compared with empty vector cells. In addition, HER2 dimer cells showed in increased cell invasion, reaching significance for induced HER2-HER3 heterodimers (P = 0.015). Importantly, in three-dimensional organotypic cultures, empty vector cells grew as a superficial cell layer, resembling oesophageal squamous epithelium. In contrast, induced HER2 homodimer cells were highly invasive into the matrix and formed cell clusters. This was associated with partial loss of cytokeratin 7 (when HER2 homodimers were modelled) and p63 (when EGFR-HER2 heterodimers were modelled), which suggests a change or loss of squamous cell differentiation. Controlled activation of specific EGFR, HER2 and HER3 homodimers and heterodimers caused oesophageal squamous epithelial cell migration and/or invasion, especially in a three-dimensional microenvironment, thereby functionally identifying ErbB homodimers and heterodimers as important drivers of oesophageal carcinogenesis. 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.4987DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5693673PMC
December 2017

Epithelioid hemangioendotheliomas of the liver and lung in children and adolescents.

Pediatr Blood Cancer 2017 Dec 9;64(12). Epub 2017 Jun 9.

German Cancer Consortium (DKTK), Partner site Freiburg, Freiburg, Germany.

Epithelioid hemangioendothelioma (EHE) is a rare, vascular sarcoma. Visceral forms arise in the liver/ lungs. We review the clinical and molecular phenotype of pediatric visceral EHE based on the case of a 9-year-old male child with EHE of the liver/lungs. His tumor expressed the EHE-specific fusion oncogene WWTR1-CAMTA1. Molecular characterization revealed a low somatic mutation rate and activated interferon signaling, angiogenesis regulation, and blood vessel remodeling. After polychemotherapy and resection of lung tumors, residual disease remained stable on oral lenalidomide. Literature review identified another 24 children with EHE of the liver/lungs. Most presented with multifocal, systemic disease. Only those who underwent complete resection achieved complete remission. Four children experienced rapid progression and died. In six children, disease remained stable for years without therapy. Two patients died from progressive EHE 21 and 24 years after first diagnosis. Natural evolution of pediatric visceral EHE is variable, and long-term prognosis remains unclear.
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http://dx.doi.org/10.1002/pbc.26675DOI Listing
December 2017

Protein-losing pseudomembranous colitis with cap polyposis-like features.

World J Gastroenterol 2017 Apr;23(16):3003-3010

Wolfgang Kreisel, Bertram Bengsch, Anna-Maria Globig, Department of Medicine II, Gastroenterology, Hepatology, Endocrinology and Infectious Diseases, Medical Center, University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany.

Protein-losing enteropathy (PLE) is characterized by loss of serum proteins into the gastrointestinal tract. It may lead to hypoproteinemia and clinically present as protein deficiency edema, ascites, pleural or pericardial effusion and/or malnutrition. In most cases the site of protein loss is the small intestine. Here we present an unusual case of severe PLE in a 55-year old female with a one-year history of recurrent diarrhea, crampy abdominal pain, and peripheral edema. Endoscopy and MRI showed a diffuse inflammatory thickening of the sigmoid colon and the rectum. Surgical resection of the involved colon was performed and the symptoms were significantly resolved. The final histologic evaluation confirmed a diagnosis of a pseudomembranous colitis with cap polyposis-like features. Such a cause of PLE has never been described before.
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http://dx.doi.org/10.3748/wjg.v23.i16.3003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413796PMC
April 2017

The Atypical Kinase RIOK1 Promotes Tumor Growth and Invasive Behavior.

EBioMedicine 2017 Jun 12;20:79-97. Epub 2017 Apr 12.

Institute of Molecular Medicine and Cell Research (IMMZ), Faculty of Medicine, Albert-Ludwigs-University (ALU), Freiburg, Germany; Faculty of Biology, ALU, Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, BIOSS, ALU, Germany; German Cancer Consortium (DKTK, Freiburg) and German Cancer Research Center (DKFZ), Heidelberg, Germany. Electronic address:

Despite being overexpressed in different tumor entities, RIO kinases are hardly characterized in mammalian cells. We investigated the role of these atypical kinases in different cancer cells. Using isogenic colon-, breast- and lung cancer cell lines, we demonstrate that knockdown of RIOK1, but not of RIOK2 or RIOK3, strongly impairs proliferation and invasiveness in conventional and 3D culture systems. Interestingly, these effects were mainly observed in RAS mutant cancer cells. In contrast, growth of RAS wildtype Caco-2 and Bcr-Abl-driven K562 cells is not affected by RIOK1 knockdown, suggesting a specific requirement for RIOK1 in the context of oncogenic RAS signaling. Furthermore, we show that RIOK1 activates NF-κB signaling and promotes cell cycle progression. Using proteomics, we identified the pro-invasive proteins Metadherin and Stathmin1 to be regulated by RIOK1. Additionally, we demonstrate that RIOK1 promotes lung colonization in vivo and that RIOK1 is overexpressed in different subtypes of human lung- and breast cancer. Altogether, our data suggest RIOK1 as a potential therapeutic target, especially in RAS-driven cancers.
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http://dx.doi.org/10.1016/j.ebiom.2017.04.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478185PMC
June 2017

EpCAM controls morphogenetic programs during zebrafish pronephros development.

Biochem Biophys Res Commun 2017 May 12;487(2):209-215. Epub 2017 Apr 12.

Renal Division, Department of Medicine, University Freiburg Medical Center, Hugstetter Str. 55, 79106 Freiburg, Germany. Electronic address:

Epithelial cell adhesion molecule EpCAM is a transmembrane glycoprotein that is dynamically expressed in human and murine renal epithelia during development. The levels of EpCAM in the renal epithelium are upregulated both during regeneration after ischemia/reperfusion injury and in renal-derived carcinomas. The role of EpCAM in early kidney development, however, has remained unclear. The zebrafish pronephros shows a similar segmentation pattern to the mammalian metanephric nephron, and has recently emerged as a tractable model to study the regulatory programs governing early nephrogenesis. Since EpCAM shows persistent expression in the pronephros throughout early development, we developed a method to study the global changes in gene expression in specific pronephric segments of wild type and EpCAM-deficient zebrafish embryos. In epcam mutants, we found 379 differentially expressed genes. Gene ontology analysis revealed that EpCAM controls various developmental programs, including uretric bud development, morphogenesis of branching epithelium, regulation of cell differentiation and cilium morphogenesis.
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http://dx.doi.org/10.1016/j.bbrc.2017.04.035DOI Listing
May 2017

ATM mutations and E-cadherin expression define sensitivity to EGFR-targeted therapy in colorectal cancer.

Oncotarget 2017 Mar;8(10):17164-17190

Institute of Surgical Pathology, University of Freiburg, Freiburg im Breisgau, Germany.

EGFR-targeted therapy is a key treatment approach in patients with RAS wildtype metastatic colorectal cancers (CRC). Still, also RAS wildtype CRC may be resistant to EGFR-targeted therapy, with few predictive markers available for improved stratification of patients. Here, we investigated response of 7 CRC cell lines (Caco-2, DLD1, HCT116, HT29, LS174T, RKO, SW480) to Cetuximab and correlated this to NGS-based mutation profiles, EGFR promoter methylation and EGFR expression status as well as to E-cadherin expression. Moreover, tissue specimens of primary and/or recurrent tumors as well as liver and/or lung metastases of 25 CRC patients having received Cetuximab and/or Panitumumab were examined for the same molecular markers. In vitro and in situ analyses showed that EGFR promoter methylation and EGFR expression as well as the MSI and or CIMP-type status did not guide treatment responses. In fact, EGFR-targeted treatment responses were also observed in RAS exon 2 p.G13 mutated CRC cell lines or CRC cases and were further linked to PIK3CA exon 9 mutations. In contrast, non-response to EGFR-targeted treatment was associated with ATM mutations and low E-cadherin expression. Moreover, down-regulation of E-cadherin by siRNA in otherwise Cetuximab responding E-cadherin positive cells abrogated their response. Hence, we here identify ATM and E-cadherin expression as potential novel supportive predictive markers for EGFR-targeted therapy.
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http://dx.doi.org/10.18632/oncotarget.15211DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5370031PMC
March 2017

Spatio-temporal mutation profiles of case-matched colorectal carcinomas and their metastases reveal unique de novo mutations in metachronous lung metastases by targeted next generation sequencing.

Mol Cancer 2016 10 18;15(1):63. Epub 2016 Oct 18.

Institute for Surgical Pathology, Medical Center-Faculty of Medicine, University of Freiburg, Breisacherstr. 115A, 79106, Freiburg, Germany.

Background: Targeted next generation sequencing (tNGS) has become part of molecular pathology diagnostics for determining RAS mutation status in colorectal cancer (CRC) patients as predictive tool for decision on EGFR-targeted therapy. Here, we investigated mutation profiles of case-matched tissue specimens throughout the disease course of CRC, to further specify RAS-status dynamics and to identify de novo mutations associated with distant metastases.

Methods: Case-matched formalin-fixed and paraffin-embedded (FFPE) resection specimens (n = 70; primary tumours, synchronous and/or metachronous liver and/or lung metastases) of 14 CRC cases were subjected to microdissection of normal colonic epithelial, primary and metastatic tumour cells, their DNA extraction and an adapted library protocol for limited DNA using the 48 gene TruSeq Amplicon Cancer Panel, MiSeq sequencing and data analyses (Illumina).

Results: By tNGS primary tumours were RAS wildtype in 5/14 and mutated in 9/14 (8/9 KRAS exon 2; 1/9 NRAS Exon 3) of cases. RAS mutation status was maintained in case-matched metastases throughout the disease course, albeit with altered allele frequencies. Case-matched analyses further identified a maximum of three sequence variants (mainly in APC, KRAS, NRAS, TP53) shared by all tumour specimens throughout the disease course per individual case. In addition, further case-matched de novo mutations were detected in synchronous and/or metachronous liver and/or lung metastases (e.g. in APC, ATM, FBXW7, FGFR3, GNAQ, KIT, PIK3CA, PTEN, SMAD4, SMO, STK11, TP53, VHL). Moreover, several de novo mutations were more frequent in synchronous (e.g. ATM, KIT, PIK3CA, SMAD4) or metachronous (e.g. FBXW7, SMO, STK11) lung metastases. Finally, some de novo mutations occurred only in metachronous lung metastases (CDKN2A, FGFR2, GNAS, JAK3, SRC).

Conclusion: Together, this study employs an adapted FFPE-based tNGS approach to confirm conservation of RAS mutation status in primary and metastatic tissue specimens of CRC patients. Moreover, it identifies genes preferentially mutated de novo in late disease stages of metachronous CRC lung metastases, several of which might be actionable by targeted therapies.
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http://dx.doi.org/10.1186/s12943-016-0549-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5069823PMC
October 2016

Turning Skyscrapers into Town Houses: Insights into Barrett's Esophagus.

Pathobiology 2017 23;84(2):87-98. Epub 2016 Sep 23.

Institute for Surgical Pathology, Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.

Barrett's esophagus (BE) is defined as metaplasia of the esophageal squamous epithelium with multiple cell layers into a single layer of intestinal columnar epithelial cells - or, in other words, skyscrapers are turned into town houses. The underlying pathomechanism(s) and the cell of origin of BE lesions have not been defined yet. However, four potential hypotheses for BE development have been suggested. The morphological changes during BE development are associated with rather well-described aberrant gene/protein expression patterns. However, the potential key regulators of this conversion process are still unclear. The process of metaplastic conversion is difficult to monitor in a spatiotemporal manner in vitro, and robust models are lacking. There is therefore a need for novel experimental systems. This review focuses on potential key regulators, microenvironmental influences, epigenetic alterations and experimental research systems related to BE.
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http://dx.doi.org/10.1159/000447779DOI Listing
March 2017

Loss of LSR affects epithelial barrier integrity and tumor xenograft growth of CaCo-2 cells.

Oncotarget 2017 Jun;8(23):37009-37022

Institute of Experimental and Clinical Pharmacology and Toxicology, Albert-Ludwigs-University (ALU), Freiburg, Germany.

The lipolysis-stimulated lipoprotein receptor (LSR) is a lipoprotein receptor, serves as host receptor for clostridial iota-like toxins and is involved in the formation of tricellular contacts. Of particular interest is the role of LSR in progression of various cancers. Here we aimed to study the tumor growth of LSR-deficient colon carcinoma-derived cell lines HCT116 and CaCo-2 in a mouse xenograft model. Whereas knockout of LSR had no effect on tumor growth of HCT116 cells, we observed that CaCo-2 LSR knockout tumors grew to a smaller size than their wild-type counterparts. Histological analysis revealed increased apoptotic and necrotic cell death in a tumor originating from LSR-deficient CaCo-2 cells. LSR-deficient CaCo-2 cells exhibited increased cell proliferation in vitro and an altered epithelial morphology with impaired targeting of tricellulin to tricellular contacts. In addition, loss of LSR reduced the transepithelial electrical resistance of CaCo-2 cell monolayers and increased permeability for small molecules. Moreover, LSR-deficient CaCo-2 cells formed larger cysts in 3D culture than their wild-type counterparts. Our study provides evidence that LSR affects epithelial morphology and barrier formation in CaCo-2 cells and examines for the first time the effects of LSR deficiency on the tumor growth properties of colon carcinoma-derived cell lines.
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http://dx.doi.org/10.18632/oncotarget.10425DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5514888PMC
June 2017

Histone modifiers and marks define heterogeneous groups of colorectal carcinomas and affect responses to HDAC inhibitors in vitro.

Am J Cancer Res 2016 15;6(3):664-76. Epub 2016 Feb 15.

Department of Pathology, All University Medical CenterFreiburg, Germany; German Cancer Consortium (DKTK) and German Cancer Research Center (DKFZ)Heidelberg, Germany; Comprehensive Cancer Center Freiburg, All University Medical CenterFreiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of FreiburgGermany.

Little is known about histone modifiers and histone marks in colorectal cancers (CRC). The present study therefore addressed the role of histone acetylation and histone deacetylases (HDAC) in CRCs in situ and in vitro. Immunohistochemistry of primary CRCs (n=47) revealed that selected histone marks were frequently present (H3K4me3: 100%; H3K9me3: 77%; H3K9ac: 75%), partially displayed intratumoral heterogeneity (H3K9me3; H3K9ac) and were significantly linked to higher pT category (H3K9me3: p=0.023; H3K9ac: p=0.028). Furthermore, also HDAC1 (62%), HDAC2 (100%) and HDAC3 (72%) expression was frequent, revealing four CRC types: cases expressing 1) HDAC1, HDAC2 and HDAC3 (49%), 2) HDAC2 and HDAC3 (30%), 3) HDAC1 and HDAC2 (10.5%) and 4) exclusively HDAC2 (10.5%). Correlation to clinico-pathological parameters (pT, pN, G, MSI status) revealed that heterogeneous HDAC1 expression correlated with lymph node status (p=0.012). HDAC expression in situ was partially reflected by six CRC cell lines, with similar expression of all three HDACs (DLD1, LS174T), preferential HDAC2 and HDAC3 expression (SW480, Caco2) or lower HDAC2 and HDAC3 expression (HCT116, HT29). HDAC activity was variably higher in HCT116, HT29, DLD1 and SW480 compared to LS174T and Caco2 cells. Treatment with broad (SAHA) and specific (MS-275; FK228) HDAC inhibitors (HDACi) caused loss of cell viability in predominantly MSIpositive CRC cells (HCT116, LS174T, DLD1; SAHA, MS-275 and in part FK228). In contrast, MSI-negative CRC cells (Caco2, HT29, SW480) were resistant, except for high doses of FK228 (Caco2, HT29). Cell viability patterns were not linked to different efficacies of HDACi on reduction of HDAC activity or histone acetylation, p21 expression and/or induction of DNA damage (γH2A-X levels). In summary, this study reveals inter- and intra-tumoral heterogeneity of histone marks and HDAC expression in CRCs. This is reflected by diverse HDACi responses in vitro, which do not follow known modes of action. Together, this implies further exploitation of histone alterations in CRC for molecular classification and/or novel treatment options.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4851845PMC
May 2016

Response of esophageal cancer cells to epigenetic inhibitors is mediated via altered thioredoxin activity.

Lab Invest 2016 Mar 21;96(3):307-16. Epub 2015 Dec 21.

Department of Pathology, Institute of Surgical Pathology, University Medical Center, Freiburg, Germany.

We previously showed that histone deacetylase inhibitor (HDACi) and 5-azacytidine (AZA) treatment selectively induced cell death of esophageal cancer cells. The mechanisms of cancer selectivity, however, remained unclear. Here we examined whether the cancer selectivity of HDACi/AZA treatment is mediated by the thioredoxin (Trx) system and reactive oxygen species (ROS) in esophageal cancer cells. For this, we first analyzed human tissue specimens of 37 esophageal cancer patients by immunohistochemistry for Trx, Trx-interacting protein (TXNIP) and Trx reductase (TXNRD). This revealed a loss or at least reduction of nuclear Trx in esophageal cancer cells, compared with normal epithelial cells (P<0.001). Although no differences were observed for TXNIP, TXNRD was more frequently expressed in cancer cells (P<0.001). In the two main histotypes of esophageal squamous cell carcinomas (ESCCs, n=19) and esophageal adenomcarcinomas (EAC, n=16), similar Trx, TXNIP and TXNRD expression patterns were observed. Also in vitro, nuclear Trx was only detectable in non-neoplastic Het-1A cells, but not in OE21/ESCC or OE33/EAC cell lines. Moreover, the two cancer cell lines showed an increased Trx activity, being significant for OE21 (P=0.0237). After treatment with HDACi and/or AZA, ROS were exclusively increased in both cancer cell lines (P=0.048-0.017), with parallel decrease of Trx activity. This was variably accompanied by increased TXNIP levels upon AZA, MS-275 or MS-275/AZA treatment for 6 or 24 h in OE21, but not in Het-1A or OE33 cells. In summary, this study evaluated Trx and its associated proteins TXNIP and TXNRD for the first time in esophageal cancers. The analyses revealed an altered subcellular localization of Trx and strong upregulation of TXNRD in esophageal cancer cells. Moreover, HDACi and AZA disrupted Trx function and induced accumulation of ROS with subsequent apoptosis in esophageal cancer cells exclusively. Trx function is hence an important cellular mediator conferring non-neoplastic cell resistance for HDACi and/or AZA.
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http://dx.doi.org/10.1038/labinvest.2015.148DOI Listing
March 2016

Subcellular localization of EGFR in esophageal carcinoma cell lines.

J Cell Commun Signal 2016 Mar 18;10(1):41-7. Epub 2015 Nov 18.

Institute of Surgical Pathology, Department of Pathology, University Medical Center, Breisacherstrasse 115A, 79106, Freiburg, Germany.

Background: The EGF receptor is a therapeutic target in cancer cells, whereby mutations of EGFR and/or signalling members act as predictive markers. EGFR however also exhibits dynamic changes of subcellular localization, leading to STAT5 complex formation, nuclear translocation and induction of Aurora-A expression in squamous cancer cells. We previously described high EGFR and Aurora-A expression in esophageal cancer cells. Here, we investigated subcellular localization of EGFR and STAT5 in esophageal cancer cells.

Results: Quantitative immunofluorescence analyses of four esophageal cancer cell lines reflecting esophageal squamous cell carcinomas (ESCC) and esophageal adenocarcinomas (EAC) revealed that the subcellular localization of EGFR was shifted from a membranous to cytoplasmic localization upon EGF-stimulation in OE21 (ESCC) cells. Thereby, EGFR in part co-localized with E-Cadherin. In parallel, phosphorylated STAT5-Tyr694 appeared to increase in the nucleus and to decrease at the cell membrane. In three additional cell lines, EGFR was only marginally (Kyse-410/ESCC; OE19/EAC) and weakly (OE33, EAC) detectable at the cell membrane. Partial co-localization of EGFR and E-Cadherin occurred in OE33 cells. Post EGF-stimulation, EGFR was detected in the cytoplasm, resembling endosomal compartments. Furthermore, OE19 and OE33 exhibited nuclear STAT5-Tyr694 phosphorylation upon EGF-stimulation. None of the four cell lines showed nuclear EGFR expression and localization.

Conclusion: In contrast to other (squamous) cancer cells, activation of EGFR in esophageal squamous cancer cells does not result in nuclear translocation of EGFR. Still, the subcellular localization of EGFR may influence STAT5-associated signaling pathways in esophageal cancer cells and hence possibly also the responses to ErbB, respective EGFR-targeted therapies.
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http://dx.doi.org/10.1007/s12079-015-0308-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4850139PMC
March 2016

Selective inhibition of esophageal cancer cells by combination of HDAC inhibitors and Azacytidine.

Epigenetics 2015 ;10(5):431-45

a Dept. of Pathology; University Medical Center ; Freiburg , Germany.

Esophageal cancers are highly aggressive tumors with poor prognosis despite some recent advances in surgical and radiochemotherapy treatment options. This study addressed the feasibility of drugs targeting epigenetic modifiers in esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC) cells. We tested inhibition of histone deacetylases (HDACs) by SAHA, MS-275, and FK228, inhibition of DNA methyltransferases by Azacytidine (AZA) and Decitabine (DAC), and the effect of combination treatment using both types of drugs. The drug targets, HDAC1/2/3 and DNMT1, were expressed in normal esophageal epithelium and tumor cells of ESCC or EAC tissue specimens, as well as in non-neoplastic esophageal epithelial (Het-1A), ESCC (OE21, Kyse-270, Kyse-410), and EAC (OE33, SK-GT-4) cell lines. In vitro, HDAC activity, histone acetylation, and p21 expression were similarly affected in non-neoplastic, ESCC, and EAC cell lines post inhibitor treatment. Combined MS-275/AZA treatment, however, selectively targeted esophageal cancer cell lines by inducing DNA damage, cell viability loss, and apoptosis, and by decreasing cell migration. Non-neoplastic Het-1A cells were protected against HDACi (MS-275)/AZA treatment. RNA transcriptome analyses post MS-275 and/or AZA treatment identified novel regulated candidate genes (up: BCL6, Hes2; down: FAIM, MLKL), which were specifically associated with the treatment responses of esophageal cancer cells. In summary, combined HDACi/AZA treatment is efficient and selective for the targeting of esophageal cancer cells, despite similar target expression of normal and esophageal cancer epithelium, in vitro and in human esophageal carcinomas. The precise mechanisms of action of treatment responses involve novel candidate genes regulated by HDACi/AZA in esophageal cancer cells. Together, targeting of epigenetic modifiers in esophageal cancers may represent a potential future therapeutic approach.
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http://dx.doi.org/10.1080/15592294.2015.1039216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4623041PMC
January 2016

Therapeutic polo-like kinase 1 inhibition results in mitotic arrest and subsequent cell death of blasts in the bone marrow of AML patients and has similar effects in non-neoplastic cell lines.

Leuk Res 2015 Apr 28;39(4):462-70. Epub 2015 Jan 28.

Institute of Clinical Pathology, Department of Pathology, University Medical Center, Breisacher Str. 115a, 79106 Freiburg, Germany. Electronic address:

Polo-like kinase 1 (PLK1) is an important regulator of the cell cycle and is overexpressed in various solid and hematological malignancies. Small molecule inhibitors targeting PLK1, such as BI2536 or BI6727 (Volasertib) are a promising therapeutic approach in such malignancies. Here, we show a loss of specifically localized PLK1 in AML blasts in vivo, accompanied by mitotic arrest with transition into apoptosis, in bone marrow biopsies of AML patients after treatment with BI2536. We verify these results in live cell imaging experiments with the AML cell line HL-60, and demonstrate that non-neoplastic, immortalized lymphoblastoid cells are also sensitive to PLK1 inhibition. It is demonstrated that normal granulopoietic precursors have similar PLK1 expression levels as leukemic blasts. These results are in line with the adverse effects of PLK1 inhibition and underline the great potential of PLK1 inhibitors in the treatment of AML.
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http://dx.doi.org/10.1016/j.leukres.2015.01.007DOI Listing
April 2015

Aurora B expression and histone variant H1.4S27 phosphorylation are no longer coordinated during metaphase in aneuploid colorectal carcinomas.

Virchows Arch 2015 May 14;466(5):503-15. Epub 2015 Feb 14.

Department of Pathology, University Medical Center, Breisacherstrasse 115A, 79106, Freiburg, Germany.

Experimental model systems identified phosphorylation of linker histone variant H1.4 at Ser 27 (H1.4S27p) as a novel mitotic mark set by Aurora B kinase. Here, we examined expression of Aurora B and H1.4S27p in colorectal carcinoma (CRC) cell lines (HCT116, DLD1, Caco-2, HT29) and tissue specimens (n = 36), in relation to microsatellite instability (MSI) status and ploidy. In vitro, Aurora B (pro-/meta-/anaphase) and H1.4S27p (pro-/metaphase) were localized in mitotic figures. The proportion of labeled mitoses was significantly different between cell lines for Aurora B (p = 0.019) but not for H1.4S27p (p = 0.879). For Aurora B, these differences were not associated with an altered Aurora B gene copy number (FISH) or messenger RNA (mRNA) expression level (qRT-PCR). Moreover, Aurora B expression and H1.4S27 phosphorylation were no longer coordinated during metaphase in aneuploid HT29 cells (p = 0.039). In CRCs, immunoreactivity for Aurora B or H1.4S27p did not correlate with T- or N-stage, grade, or MSI status. However, metaphase labeling of H1.4S27p was significantly higher in diploid than in aneuploid CRCs (p = 0.011). Aurora B was significantly correlated with H1.4S27p-positive metaphases in MSI (p = 0.010) or diploid (p = 0.003) CRCs. Finally, combined classification of MSI status and ploidy revealed a significant positive correlation of Aurora B with H1.4S27p in metaphases of diploid/MSI (p = 0.010) and diploid/microsatellite-stable (MSS; p = 0.031) but not of aneuploid/MSS (p = 0.458) CRCs. The present study underlines the functional link of Aurora B expression and H1.4S27p during specific phases of mitosis in diploid and/or MSI-positive CRCs in vitro and in situ. Importantly, the study shows that the coordination between Aurora B expression and phosphorylation of H1.4 at Ser 27 is lost in cycling aneuploid CRC cells.
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http://dx.doi.org/10.1007/s00428-015-1727-6DOI Listing
May 2015

B-Raf inhibitors induce epithelial differentiation in BRAF-mutant colorectal cancer cells.

Cancer Res 2015 Jan 7;75(1):216-29. Epub 2014 Nov 7.

Signal Transduction in Tumour Development and Drug Resistance Group, Institute of Molecular Medicine and Cell Research (IMMZ), Albert-Ludwigs-University (ALU), Freiburg, Germany. Centre for Biological Signalling Studies BIOSS, ALU Freiburg.

BRAF mutations are associated with aggressive, less-differentiated and therapy-resistant colorectal carcinoma. However, the underlying mechanisms for these correlations remain unknown. To understand how oncogenic B-Raf contributes to carcinogenesis, in particular to aspects other than cellular proliferation and survival, we generated three isogenic human colorectal carcinoma cell line models in which we can dynamically modulate the expression of the B-Raf(V600E) oncoprotein. Doxycyclin-inducible knockdown of endogenous B-Raf(V600E) decreases cellular motility and invasion in conventional and three-dimensional (3D) culture, whereas it promotes cell-cell contacts and induces various hallmarks of differentiated epithelia. Importantly, all these effects are recapitulated by B-Raf (PLX4720, vemurafenib, and dabrafenib) or MEK inhibitors (trametinib). Surprisingly, loss of B-Raf(V600E) in HT29 xenografts does not only stall tumor growth, but also induces glandular structures with marked expression of CDX2, a tumor-suppressor and master transcription factor of intestinal differentiation. By performing the first transcriptome profiles of PLX4720-treated 3D cultures of HT29 and Colo-205 cells, we identify several upregulated genes linked to epithelial differentiation and effector functions, such as claudin-1, a Cdx-2 target gene encoding a critical tight junction component. Thereby, we provide a mechanism for the clinically observed correlation between mutant BRAF and the loss of Cdx-2 and claudin-1. PLX4720 also suppressed several metastasis-associated transcripts that have not been implicated as targets, effectors or potential biomarkers of oncogenic B-Raf signaling so far. Together, we identify a novel facet of clinically applied B-Raf or MEK inhibitors by showing that they promote cellular adhesion and differentiation of colorectal carcinoma cells.
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http://dx.doi.org/10.1158/0008-5472.CAN-13-3686DOI Listing
January 2015

Metadherin exon 11 skipping variant enhances metastatic spread of ovarian cancer.

Int J Cancer 2015 May 8;136(10):2328-40. Epub 2014 Nov 8.

Department of Hematology and Oncology, Freiburg University Medical Center, University of Freiburg, Germany; Department of Psychiatry and Psychotherapy, Freiburg University Medical Center, University of Freiburg, Germany.

Metastatic ovarian cancer has a dismal prognosis and current chemotherapeutic approaches have very limited success. Metadherin (MTDH) is expressed in human ovarian cancer tissue and its expression inversely correlates with patients overall survival. Consistent with these studies, we observed MTDH expression in tissue specimens of FIGO Stage III ovarian carcinomas (72/83 cases). However, we also observed this in normal human ovarian epithelial (OE) cells, which raised the question of whether MTDH-variants with functional differences exist. We identified a novel MTDH exon 11 skipping variant (MTDHdel) which was seen at higher levels in ovarian cancer compared to benign OE cells. We analyzed MTDH-binding partner interactions and found that 12 members of the small ribosomal subunit and several mRNA binding proteins bound stronger to MTDHdel than to wildtype MTDH which indicates differential effects on gene translation. Knockdown of MTDH in ovarian cancer cells reduced the amount of distant metastases and improved the survival of ovarian cancer-bearing mice. Selective overexpression of the MTDHdel enhanced murine and human ovarian cancer progression and caused a malignant phenotype in originally benign human OE cells. MTDHdel was detectable in microdissected ovarian cancer cells of some human tissue specimens of ovarian carcinomas. In summary, we have identified a novel MTDH exon 11 skipping variant that shows enhanced binding to small ribosomal subunit members and that caused reduced overall survival of ovarian cancer bearing mice. Based on the findings in the murine system and in human tissues, MTDHdel must be considered a major promalignant factor for ovarian cancer.
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http://dx.doi.org/10.1002/ijc.29289DOI Listing
May 2015

Does imaging αvβ3 integrin expression with PET detect changes in angiogenesis during bevacizumab therapy?

J Nucl Med 2014 Nov 2;55(11):1878-84. Epub 2014 Oct 2.

Molecular Imaging and Therapy Service, Memorial Sloan Kettering Cancer Center, New York, New York.

Unlabelled: In recent years, there has been a growing interest in molecular imaging markers of tumor-induced angiogenesis. Several radiolabeled RGD (arginine, glycine, aspartate) peptides have been developed for PET imaging of αvβ3 integrins in the tumor vasculature, but there are only limited data on how angiogenesis inhibitors affect the tumor uptake of these peptides.

Methods: Changes in (68)Ga-NODAGA-c(RGDfK) peptide uptake were measured using PET during bevacizumab therapy of 2 αvβ3-negative squamous cell carcinoma cell lines (A-431 and FaDu) that induce αvβ3-positive neovasculature when transplanted into nude mice. Tumor uptake of (68)Ga-NODAGA-c(RGDfK) was correlated to microvascular density, vascular morphology, and permeability as well as αvβ3 integrin expression.

Results: Bevacizumab significantly inhibited growth of A-431 tumors and caused a significant reduction in microvascular density and αvβ3 integrin expression within 7 d after start of therapy. Bevacizumab also caused a normalization of blood vessel morphology and decreased tumor necrosis. However, (68)Ga-NODAGA-c(RGDfK) uptake was significantly increased at day 7 of therapy and did not decrease until after 3 wk of treatment. In Fadu xenografts, bevacizumab therapy caused only a minor inhibition of tumor growth and minor changes in (68)Ga-NODAGA-c(RGDfK) uptake.

Conclusion: Uptake of radiolabeled RGD peptides is not necessarily decreased by effective antiangiogenic therapy. Early in the course of therapy a decrease in the expression of αvβ3 integrins may not be reflected by a decrease in the uptake of RGD peptides.
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http://dx.doi.org/10.2967/jnumed.114.137570DOI Listing
November 2014

SNAIL1 combines competitive displacement of ASCL2 and epigenetic mechanisms to rapidly silence the EPHB3 tumor suppressor in colorectal cancer.

Mol Oncol 2015 Feb 16;9(2):335-54. Epub 2014 Sep 16.

Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg, Stefan-Meier-Str. 17, 79104 Freiburg, Germany; Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, Schänzlestr. 18, 79104 Freiburg, Germany. Electronic address:

EPHB3 is a critical cellular guidance factor in the intestinal epithelium and an important tumor suppressor in colorectal cancer (CRC) whose expression is frequently lost at the adenoma-carcinoma transition when tumor cells become invasive. The molecular mechanisms underlying EPHB3 silencing are incompletely understood. Here we show that EPHB3 expression is anti-correlated with inducers of epithelial-mesenchymal transition (EMT) in primary tumors and CRC cells. In vitro, SNAIL1 and SNAIL2, but not ZEB1, repress EPHB3 reporter constructs and compete with the stem cell factor ASCL2 for binding to an E-box motif. At the endogenous EPHB3 locus, SNAIL1 triggers the displacement of ASCL2, p300 and the Wnt pathway effector TCF7L2 and engages corepressor complexes containing HDACs and the histone demethylase LSD1 to collapse active chromatin structure, resulting in rapid downregulation of EPHB3. Beyond its impact on EPHB3, SNAIL1 deregulates markers of intestinal identity and stemness and in vitro forces CRC cells to undergo EMT with altered morphology, increased motility and invasiveness. In xenotransplants, SNAIL1 expression abrogated tumor cell palisading and led to focal loss of tumor encapsulation and the appearance of areas with tumor cells displaying a migratory phenotype. These changes were accompanied by loss of EPHB3 and CDH1 expression. Intriguingly, SNAIL1-induced phenotypic changes of CRC cells are significantly impaired by sustained EPHB3 expression both in vitro and in vivo. Altogether, our results identify EPHB3 as a novel target of SNAIL1 and suggest that disabling EPHB3 signaling is an important aspect to eliminate a roadblock at the onset of EMT processes.
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http://dx.doi.org/10.1016/j.molonc.2014.08.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5528665PMC
February 2015

ErbB targeting inhibitors repress cell migration of esophageal squamous cell carcinoma and adenocarcinoma cells by distinct signaling pathways.

J Mol Med (Berl) 2014 Nov 6;92(11):1209-23. Epub 2014 Aug 6.

Department of Pathology, University Medical Center, Breisacherstrasse 115A, 79106, Freiburg, Germany.

Unlabelled: ErbB family receptor tyrosine kinases (ErbBs) play a role in cell adhesion and migration and are frequently overexpressed in esophageal squamous cell carcinomas (ESCCs) or esophageal adenocarcinomas (EACs). Targeting ErbBs by tyrosine kinase inhibitors (TKIs) may therefore limit esophageal cancer cell migration. Here, we studied the impact of TKIs on ErbB dimerization, cell signaling pathways, and cell migration in three esophageal cell lines: OE21 (ESCC), OE33 (EAC), and Het-1A (non-neoplastic esophageal epithelium). In OE21 cells, the TKIs erlotinib, gefitinib, and lapatinib slightly affected epidermal growth factor receptor EGFR/EGFR, but not EGFR/HER2 dimerization as detected by in situ proximity ligation assay (in situ PLA). Still, TKIs inhibited ERK1/2, Akt, STAT3, and RhoA activity in OE21 cells, as assessed by Western blot, antibody arrays, and Rho GTPase effector pull-down assays. This was accompanied by reduced OE21 cell migration, induction of focal adhesions, and actin cytoskeleton reorganization, as shown by Oris™ migration assay and focal adhesion kinase (FAK)/phalloidin staining. In contrast, in OE33 cells, only lapatinib decreased STAT5, Src family kinase (SFK), and FAK activity as well as β-catenin expression. This impeded cell migration and induced morphological changes in OE33 cells. No alterations were seen for the non-neoplastic Het-1A cells. Thus, we identified the ErbB signaling network as regulator of esophageal cancer cell's actin cytoskeleton, focal adhesions, and cell migration. ErbB targeted TKIs therefore also limit ESCC and EAC cell motility and migration.

Key Message: Clinical tyrosine kinase inhibitors (TKIs) reduce esophageal cancer cell migration. Loss of cell migration is linked to reduced Akt, ERK1/2, STAT (3 or 5), FAK, SFKs, and RhoA activity. Clinical TKIs act via distinct signaling in the two main histotypes of esophageal cancer.
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http://dx.doi.org/10.1007/s00109-014-1187-5DOI Listing
November 2014

Impact of routinely employed procedures for tissue processing on the proteomic analysis of formalin-fixed paraffin-embedded tissue.

Proteomics Clin Appl 2014 Oct 24;8(9-10):796-804. Epub 2014 Jul 24.

Institute of Pathology, University Medical Center, Freiburg, Germany; Comprehensive Cancer Center, Freiburg, Germany.

Purpose: FFPE (formalin fixed, paraffin embedded) tissue cohorts represent an enduring archive of clinical specimens. Proteomic analysis of FFPE tissues is gaining interest for the in-depth analysis of aberrant proteome composition. Procedures for FFPE tissue processing are standardized but there is diversity regarding the different processing systems. This work focuses on three different processing methods commonly used in large European pathology institutes.

Experimental Design: Formalin fixed tissue specimens of different tumors were serially sliced and processed with three different processing systems (xylene, ethanol/vacuum or microwave based). After paraffin embedding, they were subjected to MS-based proteomic analysis to investigate the impact of tissue processing techniques on the quality of proteomic analysis. Results were compared with proteomic analysis of corresponding cryopreserved tissue specimens.

Results: All processing techniques achieved very good proteome coverage similar to the cryopreserved counterpart. Gene ontology profiles, relative protein abundances, and peptide modifications such as methionine oxidation or proteolytic truncation were highly similar for all techniques as well as for the cryopreserved samples.

Conclusions And Clinical Relevance: The results show that different processing procedures do not impede proteomic analysis as a robust and powerful approach for the identification of protein determinants and markers of disease processes and highlights the general robustness of FFPE-tissue based proteomics.
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http://dx.doi.org/10.1002/prca.201300082DOI Listing
October 2014