@article{HesbacherPfitzerWiedorferetal.2016, author = {Hesbacher, Sonja and Pfitzer, Lisa and Wiedorfer, Katharina and Angermeyer, Sabrina and Borst, Andreas and Haferkamp, Sebastian and Scholz, Claus-J{\"u}rgen and Wobser, Marion and Schrama, David and Houben, Roland}, title = {RB1 is the crucial target of the Merkel cell polyomavirus Large T antigen in Merkel cell carcinoma cells}, series = {Oncotarget}, volume = {7}, journal = {Oncotarget}, number = {22}, doi = {10.18632/oncotarget.8793}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-177858}, pages = {32956-32968}, year = {2016}, abstract = {The pocket protein (PP) family consists of the three members RB1, p107 and p130 all possessing tumor suppressive properties. Indeed, the PPs jointly control the G1/S transition mainly by inhibiting E2F transcription factors. Notably, several viral oncoproteins are capable of binding and inhibiting PPs. Merkel cell polyomavirus (MCPyV) is considered as etiological factor for Merkel cell carcinoma (MCC) with expression of the viral Large T antigen (LT) harboring an intact PP binding domain being required for proliferation of most MCC cells. Therefore, we analyzed the interaction of MCPyV-LT with the PPs. Co-IP experiments indicate that MCPyV-LT binds potently only to RB1. Moreover, MCPyV-LT knockdown-induced growth arrest in MCC cells can be rescued by knockdown of RB1, but not by p107 or p130 knockdown. Accordingly, cell cycle arrest and E2F target gene repression mediated by the single PPs can only in the case of RB1 be significantly reverted by MCPyV-LT expression. Moreover, data from an MCC patient indicate that loss of RB1 rendered the MCPyV-positive MCC cells LT independent. Thus, our results suggest that RB1 is the dominant tumor suppressor PP in MCC, and that inactivation of RB1 by MCPyV-LT is largely sufficient for its growth supporting function in established MCPyV-positive MCC cells.}, language = {en} } @article{HaferkampHesbacherWeyandtetal.2014, author = {Haferkamp, Sebastian and Hesbacher, Sonja and Weyandt, Gerhard and Vetter-Kauczok, Claudia S. and Becker, J{\"u}rgen C. and Motschenbacher, Stephanie and Wobser, Marion and Maier, Melissa and Schmid, Corinna P. and Houben, Roland}, title = {p53 regulation by TRP2 is not pervasive in melanoma}, doi = {10.1371/journal.pone.0087440}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-111396}, year = {2014}, abstract = {p53 is a central tumor suppressor protein and its inhibition is believed to be a prerequisite for cancer development. In approximately 50\% of all malignancies this is achieved by inactivating mutations in the p53 gene. However, in several cancer entities, including melanoma, p53 mutations are rare. It has been recently proposed that tyrosinase related protein 2 (TRP2), a protein involved in melanin synthesis, may act as suppressor of the p53 pathway in melanoma. To scrutinize this notion we analyzed p53 and TRP2 expression by immunohistochemistry in 172 melanoma tissues and did not find any correlation. Furthermore, we applied three different TRP2 shRNAs to five melanoma cell lines and could not observe a target specific effect of the TRP2 knockdown on either p53 expression nor p53 reporter gene activity. Likewise, ectopic expression of TRP2 in a TRP2 negative melanoma cell line had no impact on p53 expression. In conclusion our data suggest that p53 repression critically controlled by TRP2 is not a general event in melanoma.}, language = {en} } @article{WobserSiedelKneitzetal.2013, author = {Wobser, Marion and Siedel, Claudia and Kneitz, Hermann and Br{\"o}cker, Eva-Bettina and Goebeler, Mathias and Houben, Roland and Geissinger, Eva}, title = {Microvessel Density and Expression of Vascular Endothelial Growth Factor and its Receptors in Different Subtypes of Primary Cutaneous B-cell Lymphoma}, series = {Acta Dermato-Venereologica}, volume = {93}, journal = {Acta Dermato-Venereologica}, number = {6}, doi = {10.2340/00015555-1589}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128608}, pages = {656-662}, year = {2013}, abstract = {A proangiogenic micromilieu is associated with a worse prognosis in systemic lymphoma. Hence, targeting the tumour microenvironment and its vasculature has evolved as a promising novel treatment strategy. The role of tumour neoangiogenesis in cutaneous B-cell lymphoma, however, has not yet been elucidated. Therefore, we examined the expression of vascular endothelial growth factor (VEGF) and its receptors VEGFR-1 and VEGFR-2, as well as microvessel density by immunohistochemistry in paraffin-embedded specimens of different subtypes of primary cutaneous B-cell lymphomas, systemic diffuse large B-cell lymphoma, and cutaneous B-cell pseudolymphoma. Primary cutaneous large B-cell lymphoma (PCLBCL) were characterized by significantly higher intratumoral expression levels of VEGF and its receptors in comparison with the indolent lymphoma subtypes. Moreover, PCLBCL exhibited significantly higher intratumoral microvessel counts. Our study provides evidence that the most aggressive subtype of cutaneous B-cell lymphoma, PCLBCL, is characterized by a proangiogenic micromilieu.}, language = {en} } @article{WobserRothAppenzelleretal.2021, author = {Wobser, Marion and Roth, Sabine and Appenzeller, Silke and Houben, Roland and Schrama, David and Goebeler, Matthias and Geissinger, Eva and Rosenwald, Andreas and Maurus, Katja}, title = {Targeted deep sequencing of mycosis fungoides reveals intracellular signaling pathways associated with aggressiveness and large cell transformation}, series = {Cancers}, volume = {13}, journal = {Cancers}, number = {21}, issn = {2072-6694}, doi = {10.3390/cancers13215512}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250094}, year = {2021}, abstract = {Introduction: Large-cell transformation (LCT) of mycosis fungoides (MF) has been associated with a higher risk of relapse and progression and, consequently, restricted prognosis. Its molecular pathogenesis has not been elucidated yet. Materials and Methods: In order to address molecular mechanisms of LCT, we performed hybrid capture panel-based sequencing of skin biopsies from 10 patients suffering from MF with LCT versus 17 patients without LCT including follow-up biopsies during clinical course, respectively (51 samples in total). The analyzed patients were attributed to three different groups based on the presence of LCT and clinical behavior. Results: While indolent MF cases without LCT did not show pathogenic driver mutations, a high rate of oncogenic alterations was detected in patients with LCT and aggressive clinical courses. Various genes of different oncogenic signaling pathways, including the MAPK and JAK-STAT signaling pathways, as well as epigenetic modifiers were affected. A high inter-individual and distinctive intra-individual mutation diversity was observed. Oncogenic RAS mutations were exclusively detected in patients with LCT. Conclusion: Our data demonstrate that LCT transition of MF is associated with increased frequency of somatic mutations in cancer-associated genes. In particular, the activation of RAS signaling — together with epigenetic dysregulation — may crucially contribute to the molecular pathogenesis of the LCT phenotype, thus conveying its adverse clinical behavior.}, language = {en} } @article{GrimmHufnagelWobseretal.2018, author = {Grimm, Johannes and Hufnagel, Anita and Wobser, Marion and Borst, Andreas and Haferkamp, Sebastian and Houben, Roland and Meierjohann, Svenja}, title = {BRAF inhibition causes resilience of melanoma cell lines by inducing the secretion of FGF1}, series = {Oncogenesis}, volume = {7}, journal = {Oncogenesis}, number = {71}, doi = {10.1038/s41389-018-0082-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-177261}, year = {2018}, abstract = {Approximately half of all melanoma patients harbour activating mutations in the serine/threonine kinase BRAF. This is the basis for one of the main treatment strategies for this tumor type, the targeted therapy with BRAF and MEK inhibitors. While the initial responsiveness to these drugs is high, resistance develops after several months, frequently at sites of the previously responding tumor. This indicates that tumor response is incomplete and that a certain tumor fraction survives even in drug-sensitive patients, e.g., in a therapy-induced senescence-like state. Here, we show in several melanoma cell lines that BRAF inhibition induces a secretome with stimulating effect on fibroblasts and naive melanoma cells. Several senescence-associated factors were found to be transcribed and secreted in response to BRAF or MEK inhibition, among them members of the fibroblast growth factor family. We identified the growth factor FGF1 as mediator of resilience towards BRAF inhibition, which limits the pro-apoptotic effects of the drug and activates fibroblasts to secrete HGF. FGF1 regulation was mediated by the PI3K pathway and by FRA1, a direct target gene of the MAPK pathway. When FGFR inhibitors were applied in parallel to BRAF inhibitors, resilience was broken, thus providing a rationale for combined therapeutical application.}, language = {en} } @article{WobserWeberGlunzetal.2019, author = {Wobser, Marion and Weber, Alexandra and Glunz, Amelie and Tauch, Saskia and Seitz, Kristina and Butelmann, Tobias and Hesbacher, Sonja and Goebeler, Matthias and Bartz, Ren{\´e} and Kohlhof, Hella and Schrama, David and Houben, Roland}, title = {Elucidating the mechanism of action of domatinostat (4SC-202) in cutaneous T cell lymphoma cells}, series = {Journal of Hematology \& Oncology}, volume = {12}, journal = {Journal of Hematology \& Oncology}, doi = {10.1186/s13045-019-0719-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200703}, pages = {30}, year = {2019}, abstract = {Background Targeting epigenetic modifiers is effective in cutaneous T cell lymphoma (CTCL). However, there is a need for further improvement of this therapeutic approach. Here, we compared the mode of action of romidepsin (FK228), an established class I histone deacetylase inhibitor, and domatinostat (4SC-202), a novel inhibitor of class I HDACs, which has been reported to also target the lysine-specific histone demethylase 1A (LSD1). Methods We performed MTS assays and flow cytometric analyses of propidium iodide or annexin V-stained cells to assess drug impact on cellular proliferation, cell cycle distribution, and survival. Histone acetylation and methylation as well as caspase activation was analyzed by immunoblot. Gene expression analysis was performed using NanosString technology. Knockdown and knockout of LSD1 was achieved with shRNA and CRISPR/Cas9, respectively, while the CRISPR/Cas9 synergistic activation mediator system was used to induce expression of endogenous HDACs and LSD1. Furthermore, time-lapse fluorescence microscopy and an in vitro tubulin polymerization assay were applied. Results While FK228 as well as 4SC-202 potently induced cell death in six different CTCL cell lines, only in the case of 4SC-202 death was preceded by an accumulation of cells in the G2/M phase of the cell cycle. Surprisingly, apoptosis and accumulation of cells with double DNA content occurred already at 4SC-202 concentrations hardly affecting histone acetylation and methylation, and provoking significantly less changes in gene expression compared to biologically equivalent doses of FK228. Indeed, we provide evidence that the 4SC-202-induced G2/M arrest in CTCL cells is independent of de novo transcription. Furthermore, neither enforced expression of HDAC1 nor knockdown or knockout of LSD1 affected the 4SC-202-induced effects. Since time-lapse microscopy revealed that 4SC-202 could affect mitotic spindle formation, we performed an in vitro tubulin polymerization assay revealing that 4SC-202 can directly inhibit microtubule formation. Conclusions We demonstrate that 4SC-202, a drug currently tested in clinical trials, effectively inhibits growth of CTCL cells. The anti-cancer cell activity of 4SC-202 is however not limited to LSD1-inhibition, modulation of histone modifications, and consecutive alteration of gene expression. Indeed, the compound is also a potent microtubule-destabilizing agent.}, language = {en} }