@article{AlbSieAdametal.2012,
  author    = {Alb, Miriam and Sie, Christopher and Adam, Christian and Chen, Suzie and Becker, J{\"u}rgen C. and Schrama, David},
  title     = {Cellular and cytokine-dependent immunosuppressive mechanisms of grm1-transgenic murine melanoma},
  series = {Cancer Immunology, Immunotherapy},
  volume    = {61},
  journal   = {Cancer Immunology, Immunotherapy},
  number    = {12},
  doi       = {10.1007/s00262-012-1290-9},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-125096},
  pages     = {2239-2249},
  year      = {2012},
  abstract  = {Grm1-transgenic mice spontaneously develop cutaneous melanoma. This model allowed us to scrutinize the generic immune responses over the course of melanoma development. To this end, lymphocytes obtained from spleens, unrelated lymph nodes and tumor-draining lymph nodes of mice with no evidence of disease, and low or high tumor burden were analyzed ex vivo and in vitro. Thereby, we could demonstrate an increase in the number of activated CD4\(^+\) and CD8+ lymphocytes in the respective organs with increasing tumor burden. However, mainly CD4\(^+\) T cells, which could constitute both T helper as well as immunosuppressive regulatory T cells, but not CD8\(^+\) T cells, expressed activation markers upon in vitro stimulation when obtained from tumor-bearing mice. Interestingly, these cells from tumor-burdened animals were also functionally hampered in their proliferative response even when subjected to strong in vitro stimulation. Further analyses revealed that the increased frequency of regulatory T cells in tumor-bearing mice is an early event present in all lymphoid organs. Additionally, expression of the immunosuppressive cytokines TGF-β1 and IL-10 became more evident with increased tumor burden. Notably, TGF-β1 is strongly expressed in both the tumor and the tumor-draining lymph node, whereas IL-10 expression is more pronounced in the lymph node, suggesting a more complex regulation of IL-10. Thus, similar to the situation in melanoma patients, both cytokines as well as cellular immune escape mechanisms seem to contribute to the observed immunosuppressed state of tumor-bearing grm1-transgenic mice, suggesting that this model is suitable for preclinical testing of immunomodulatory therapeutics.},
  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{SarmaWillmesAngereretal.2020,
  author    = {Sarma, Bhavishya and Willmes, Christoph and Angerer, Laura and Adam, Christian and Becker, J{\"u}rgen C. and Kervarrec, Thibault and Schrama, David and Houben, Roland},
  title     = {Artesunate affects T antigen expression and survival of virus-positive Merkel cell carcinoma},
  series = {Cancers},
  volume    = {12},
  journal   = {Cancers},
  number    = {4},
  issn      = {2072-6694},
  doi       = {10.3390/cancers12040919},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-203851},
  year      = {2020},
  abstract  = {Merkel cell carcinoma (MCC) is a rare and highly aggressive skin cancer with frequent viral etiology. Indeed, in about 80\% of cases, there is an association with Merkel cell polyomavirus (MCPyV); the expression of viral T antigens is crucial for growth of virus-positive tumor cells. Since artesunate — a drug used to treat malaria — has been reported to possess additional anti-tumor as well as anti-viral activity, we sought to evaluate pre-clinically the effect of artesunate on MCC. We found that artesunate repressed growth and survival of MCPyV-positive MCC cells in vitro. This effect was accompanied by reduced large T antigen (LT) expression. Notably, however, it was even more efficient than shRNA-mediated downregulation of LT expression. Interestingly, in one MCC cell line (WaGa), T antigen knockdown rendered cells less sensitive to artesunate, while for two other MCC cell lines, we could not substantiate such a relation. Mechanistically, artesunate predominantly induces ferroptosis in MCPyV-positive MCC cells since known ferroptosis-inhibitors like DFO, BAF-A1, Fer-1 and β-mercaptoethanol reduced artesunate-induced death. Finally, application of artesunate in xenotransplanted mice demonstrated that growth of established MCC tumors can be significantly suppressed in vivo. In conclusion, our results revealed a highly anti-proliferative effect of the approved and generally well-tolerated anti-malaria compound artesunate on MCPyV-positive MCC cells, suggesting its potential usage for MCC therapy.},
  language  = {en}
}