@article{AdamBaeurleBrodskyetal.2014,
  author    = {Adam, Christian and Baeurle, Anne and Brodsky, Jeffrey L. and Schrama, David and Wipf, Peter and Becker, J{\"u}rgen Christian and Houben, Roland},
  title     = {The HSP70 Modulator MAL3-101 Inhibits Merkel Cell Carcinoma},
  doi       = {10.1371/journal.pone.0092041},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-112795},
  year      = {2014},
  abstract  = {Merkel Cell Carcinoma (MCC) is a rare and highly aggressive neuroendocrine skin cancer for which no effective treatment is available. MCC represents a human cancer with the best experimental evidence for a causal role of a polyoma virus. Large T antigens (LTA) encoded by polyoma viruses are oncoproteins, which are thought to require support of cellular heat shock protein 70 (HSP70) to exert their transforming activity. Here we evaluated the capability of MAL3-101, a synthetic HSP70 inhibitor, to limit proliferation and survival of various MCC cell lines. Remarkably, MAL3-101 treatment resulted in considerable apoptosis in 5 out of 7 MCC cell lines. While this effect was not associated with the viral status of the MCC cells, quantitative mRNA expression analysis of the known HSP70 isoforms revealed a significant correlation between MAL3-101 sensitivity and HSC70 expression, the most prominent isoform in all cell lines. Moreover, MAL3-101 also exhibited in vivo antitumor activity in an MCC xenograft model suggesting that this substance or related compounds are potential therapeutics for the treatment of MCC in the future.},
  language  = {en}
}
@article{BehrPeitschHametneretal.2014,
  author    = {Behr, Daniel S. and Peitsch, Wiebke K. and Hametner, Christian and Lasitschka, Felix and Houben, Roland and Sch{\"o}nhaar, Kathrin and Michel, Julia and Dollt, Claudia and Goebeler, Matthias and Marx, Alexander and Goerdt, Sergij and Schmieder, Astrid},
  title     = {Prognostic value of immune cell infiltration, tertiary lymphoid structures and PD-L1 expression in Merkel cell carcinomas},
  series = {International Journal of Clinical and Experimental Pathology},
  volume    = {7},
  journal   = {International Journal of Clinical and Experimental Pathology},
  number    = {11},
  issn      = {1936-2625},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-117720},
  pages     = {7610-7621},
  year      = {2014},
  abstract  = {Merkel cell carcinoma (MCC) is an aggressive, virus-associated, neuroendocrine tumor of the skin mainly affecting immunocompromised patients. Higher intratumoral infiltration with CD3 and CD8 positive T-cells is associated with a better prognosis, highlighting the relevance of the immune system for MCC development and progression. In this study 21 primary MCCs were stained with immune cell markers including CD3, CD4, CD8, CD68, CD20, and S100. Furthermore, tumor-infiltrating neutrophils, tertiary lymphoid structures and PD-L1 expression were analyzed and correlated with overall and recurrence free survival. All MCCs were Merkel Cell Polyomavirus positive. Overall and recurrence-free survival did not correlate with intra-and peritumoral CD3 and CD8 T-cell infiltration. In addition, no significant association regarding prognosis was found for tumor-associated neutrophils, tumor-associated macrophages or PD-L1 positivity in MCCs. Interestingly, the presence of tertiary lymphoid structures (TLS) in the tumor microenvironment significantly correlated with recurrence-free survival (P=0.025). In addition, TLS were significantly associated with a higher CD8/CD4 ratio in the tumor periphery (P=0.032), but not in the center of the tumor (P > 0.999). These results demonstrate for the first time that TLS, easily assessed in paraffin-embedded tissue in the tumor periphery of MCCs, may be a valuable prognostic factor indicating prolonged recurrence free survival.},
  language  = {en}
}
@article{EsnaultSchramaHoubenetal.2022,
  author    = {Esnault, Clara and Schrama, David and Houben, Roland and Guy{\´e}tant, Serge and Desgranges, Audrey and Martin, Camille and Berthon, Patricia and Viaud-Massuard, Marie-Claude and Touz{\´e}, Antoine and Kervarrec, Thibault and Samimi, Mahtab},
  title     = {Antibody-drug conjugates as an emerging therapy in oncodermatology},
  series = {Cancers},
  volume    = {14},
  journal   = {Cancers},
  number    = {3},
  issn      = {2072-6694},
  doi       = {10.3390/cancers14030778},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262192},
  year      = {2022},
  abstract  = {Antibody-drug conjugates (ADCs) are an emerging class of therapeutics, with twelve FDA- and EMA-approved drugs for hematological and solid cancers. Such drugs consist in a monoclonal antibody linked to a cytotoxic agent, allowing a specific cytotoxicity to tumor cells. In recent years, tremendous progress has been observed in therapeutic approaches for advanced skin cancer patients. In this regard, targeted therapies (e.g., kinase inhibitors) or immune checkpoint-blocking antibodies outperformed conventional chemotherapy, with proven benefit to survival. Nevertheless, primary and acquired resistances as well as adverse events remain limitations of these therapies. Therefore, ADCs appear as an emerging therapeutic option in oncodermatology. After providing an overview of ADC design and development, the goal of this article is to review the potential ADC indications in the field of oncodermatology.},
  language  = {en}
}
@article{FreyHoubenBroecker2010,
  author    = {Frey, Li­dia M. and Houben, Roland and Br{\"o}cker, Eva-B.},
  title     = {Pigmentation, Melanocyte Colonization, and p53 Status in Basal Cell Carcinoma},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-68283},
  year      = {2010},
  abstract  = {Basal cell carcinoma (BCC) is the most common neoplasm in the Caucasian population. Only a fraction of BCC exhibits pigmentation. Lack of melanocyte colonization has been suggested to be due to p53-inactivating mutations in the BCC cells interfering with the p53-proopiomelanocortin pathway and the production of alpha melanocyte-stimulating hormone in the tumor. To evaluate this, we determined tumor pigmentation as well as expression of melan-A and of p53 in 49 BCC tissues bymeans of immunohistochemistry. As expected, we observed a positive relation between tumor pigmentation and melan-A positive intratumoral melanocytes.Melanocyte colonization and, to a lesser extent, p53 overexpression showed intraindividual heterogeneity in larger tumors. p53 overexpression, which is indicative of p53 mutations, was not correlated to melanocyte colonization of BCC. Sequencing of exon 5-8 of the p53 gene in selected BCC cases revealed that colonization by melanocytes and BCC pigmentation is neither ablated by p53 mutations nor generally present in BCCs with wild-type p53.},
  subject      = {Medizin},
  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{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{HafnerHoubenBaeurleetal.2012,
  author    = {Hafner, Christian and Houben, Roland and Baeurle, Anne and Ritter, Cathrin and Schrama, David and Landthaler, Michael and Becker, J{\"u}rgen C.},
  title     = {Activation of the PI3K/AKT Pathway in Merkel Cell Carcinoma},
  series = {PLoS One},
  volume    = {7},
  journal   = {PLoS One},
  number    = {2},
  doi       = {10.1371/journal.pone.0031255},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131398},
  pages     = {e31255},
  year      = {2012},
  abstract  = {Merkel cell carcinoma (MCC) is a highly aggressive skin cancer with an increasing incidence. The understanding of the molecular carcinogenesis of MCC is limited. Here, we scrutinized the PI3K/AKT pathway, one of the major pathways activated in human cancer, in MCC. Immunohistochemical analysis of 41 tumor tissues and 9 MCC cell lines revealed high levels of AKT phosphorylation at threonine 308 in 88\% of samples. Notably, the AKT phosphorylation was not correlated with the presence or absence of the Merkel cell polyoma virus (MCV). Accordingly, knock-down of the large and small T antigen by shRNA in MCV positive MCC cells did not affect phosphorylation of AKT. We also analyzed 46 MCC samples for activating PIK3CA and AKT1 mutations. Oncogenic PIK3CA mutations were found in 2/46 (4\%) MCCs whereas mutations in exon 4 of AKT1 were absent. MCC cell lines demonstrated a high sensitivity towards the PI3K inhibitor LY-294002. This finding together with our observation that the PI3K/AKT pathway is activated in the majority of human MCCs identifies PI3K/AKT as a potential new therapeutic target for MCC patients.},
  language  = {en}
}
@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{HoubenAlimovaSarmaetal.2023,
  author    = {Houben, Roland and Alimova, Pamela and Sarma, Bhavishya and Hesbacher, Sonja and Schulte, Carolin and Sarosi, Eva-Maria and Adam, Christian and Kervarrec, Thibault and Schrama, David},
  title     = {4-[(5-methyl-1H-pyrazol-3-yl)amino]-2H-phenyl-1-phthalazinone inhibits MCPyV T antigen expression in Merkel cell carcinoma independent of Aurora kinase A},
  series = {Cancers},
  volume    = {15},
  journal   = {Cancers},
  number    = {9},
  issn      = {2072-6694},
  doi       = {10.3390/cancers15092542},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-313547},
  year      = {2023},
  abstract  = {Merkel cell carcinoma (MCC) is frequently caused by the Merkel cell polyomavirus (MCPyV), and MCPyV-positive tumor cells depend on expression of the virus-encoded T antigens (TA). Here, we identify 4-[(5-methyl-1H-pyrazol-3-yl)amino]-2H-phenyl-1-phthalazinone (PHT) — a reported inhibitor of Aurora kinase A — as a compound inhibiting growth of MCC cells by repressing noncoding control region (NCCR)-controlled TA transcription. Surprisingly, we find that TA repression is not caused by inhibition of Aurora kinase A. However, we demonstrate that β-catenin — a transcription factor repressed by active glycogen synthase kinase 3 (GSK3) — is activated by PHT, suggesting that PHT bears a hitherto unreported inhibitory activity against GSK3, a kinase known to function in promoting TA transcription. Indeed, applying an in vitro kinase assay, we demonstrate that PHT directly targets GSK3. Finally, we demonstrate that PHT exhibits in vivo antitumor activity in an MCC xenograft mouse model, suggesting a potential use in future therapeutic settings for MCC.},
  language  = {en}
}
@article{HoubenCelikdemirKervarrecetal.2023,
  author    = {Houben, Roland and Celikdemir, B{\"u}ke and Kervarrec, Thibault and Schrama, David},
  title     = {Merkel cell polyomavirus: infection, genome, transcripts and its role in development of Merkel cell carcinoma},
  series = {Cancers},
  volume    = {15},
  journal   = {Cancers},
  number    = {2},
  issn      = {2072-6694},
  doi       = {10.3390/cancers15020444},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-305021},
  year      = {2023},
  abstract  = {The best characterized polyomavirus family member, i.e., simian virus 40 (SV40), can cause different tumors in hamsters and can transform murine and human cells in vitro. Hence, the SV40 contamination of millions of polio vaccine doses administered from 1955-1963 raised fears that this may cause increased tumor incidence in the vaccinated population. This is, however, not the case. Indeed, up to now, the only polyomavirus family member known to be the most important cause of a specific human tumor entity is Merkel cell polyomavirus (MCPyV) in Merkel cell carcinoma (MCC). MCC is a highly deadly form of skin cancer for which the cellular origin is still uncertain, and which appears as two clinically very similar but molecularly highly different variants. While approximately 80\% of cases are found to be associated with MCPyV the remaining MCCs carry a high mutational load. Here, we present an overview of the multitude of molecular functions described for the MCPyV encoded oncoproteins and non-coding RNAs, present the available MCC mouse models and discuss the increasing evidence that both, virus-negative and -positive MCC constitute epithelial tumors.},
  language  = {en}
}