@article{WohllebenScherzadGuettleretal.2015,
  author    = {Wohlleben, Gisela and Scherzad, Agmal and G{\"u}ttler, Antje and Vordermark, Dirk and Kuger, Sebastian and Flentje, Michael and Polat, Buelent},
  title     = {Influence of hypoxia and irradiation on osteopontin expression in head and neck cancer and glioblastoma cell lines},
  series = {Radiation Oncology},
  volume    = {10},
  journal   = {Radiation Oncology},
  number    = {167},
  doi       = {10.1186/s13014-015-0473-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-125746},
  year      = {2015},
  abstract  = {Background Tumor hypoxia is a known risk factor for reduced response to radiotherapy. The evaluation of noninvasive methods for the detection of hypoxia is therefore of interest. Osteopontin (OPN) has been discussed as an endogenous hypoxia biomarker. It is overexpressed in many cancers and is involved in tumor progression and metastasis. Methods To examine the influence of hypoxia and irradiation on osteopontin expression we used different cell lines (head and neck cancer (Cal27 and FaDu) and glioblastoma multiforme (U251 and U87)). Cells were treated with hypoxia for 24 h and were then irradiated with doses of 2 and 8 Gy. Osteopontin expression was analyzed on mRNA level by quantitative real-time RT-PCR (qPCR) and on protein level by western blot. Cell culture supernatants were evaluated for secreted OPN by ELISA. Results Hypoxia caused an increase in osteopontin protein expression in all cell lines. In Cal27 a corresponding increase in OPN mRNA expression was observed. In contrast the other cell lines showed a reduced mRNA expression under hypoxic conditions. After irradiation OPN mRNA expression raised slightly in FaDu and U87 cells while it was reduced in U251 and stable in Cal27 cells under normoxia. The combined treatment (hypoxia and irradiation) led to a slight increase of OPN mRNA after 2 Gy in U251 (24 h) and in U87 (24 and 48 h) cell lines falling back to base line after 8 Gy. This effect was not seen in Cal27 or in FaDu cells. Secreted OPN was detected only in the two glioblastoma cell lines with reduced protein levels under hypoxic conditions. Again the combined treatment resulted in a minor increase in OPN secretion 48 hours after irradiation with 8 Gy. Conclusion Osteopontin expression is strongly modulated by hypoxia and only to a minor extent by irradiation. Intracellular OPN homeostasis seems to vary considerably between cell lines. This may explain the partly conflicting results concerning response prediction and prognosis in the clinical setting.},
  language  = {en}
}
@article{PolatKaiserWohllebenetal.2017,
  author    = {Polat, B{\"u}lent and Kaiser, Philipp and Wohlleben, Gisela and Gehrke, Thomas and Scherzad, Agmal and Scheich, Matthias and Malzahn, Uwe and Fischer, Thomas and Vordermark, Dirk and Flentje, Michael},
  title     = {Perioperative changes in osteopontin and TGFβ1 plasma levels and their prognostic impact for radiotherapy in head and neck cancer},
  series = {BMC Cancer},
  volume    = {17},
  journal   = {BMC Cancer},
  number    = {6},
  doi       = {10.1186/s12885-016-3024-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157529},
  year      = {2017},
  abstract  = {Background: In head and neck cancer little is known about the kinetics of osteopontin (OPN) expression after tumor resection. In this study we evaluated the time course of OPN plasma levels before and after surgery. Methods: Between 2011 and 2013 41 consecutive head and neck cancer patients were enrolled in a prospective study (group A). At different time points plasma samples were collected: T0) before, T1) 1 day, T2) 1 week and T3) 4 weeks after surgery. Osteopontin and TGFβ1 plasma concentrations were measured with a commercial ELISA system. Data were compared to 131 head and neck cancer patients treated with primary (n = 42) or postoperative radiotherapy (n = 89; group B1 and B2). Results: A significant OPN increase was seen as early as 1 day after surgery (T0 to T1, p < 0.01). OPN levels decreased to base line 3-4 weeks after surgery. OPN values were correlated with postoperative TGFβ1 expression suggesting a relation to wound healing. Survival analysis showed a significant benefit for patients with lower OPN levels both in the primary and postoperative radiotherapy group (B1: 33 vs 11.5 months, p = 0.017, B2: median not reached vs 33.4, p = 0.031). TGFβ1 was also of prognostic significance in group B1 (33.0 vs 10.7 months, p = 0.003). Conclusions: Patients with head and neck cancer showed an increase in osteopontin plasma levels directly after surgery. Four weeks later OPN concentration decreased to pre-surgery levels. This long lasting increase was presumably associated to wound healing. Both pretherapeutic osteopontin and TGFβ1 had prognostic impact.},
  language  = {en}
}
@article{MeyerScherzadMoratinetal.2019,
  author    = {Meyer, Till Jasper and Scherzad, Agmal and Moratin, Helena and Gehrke, Thomas Eckert and Killisperger, Julian and Hagen, Rudolf and Wohlleben, Gisela and Polat, B{\"u}lent and Dembski, Sofia and Kleinsasser, Norbert and Hackenberg, Stephan},
  title     = {The radiosensitizing effect of zinc oxide nanoparticles in sub-cytotoxic dosing is associated with oxidative stress in vitro},
  series = {Materials},
  volume    = {12},
  journal   = {Materials},
  number    = {24},
  issn      = {1996-1944},
  doi       = {10.3390/ma12244062},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-193897},
  pages     = {4062},
  year      = {2019},
  abstract  = {Radioresistance is an important cause of head and neck cancer therapy failure. Zinc oxide nanoparticles (ZnO-NP) mediate tumor-selective toxic effects. The aim of this study was to evaluate the potential for radiosensitization of ZnO-NP. The dose-dependent cytotoxicity of ZnO-NP\(_{20 nm}\) and ZnO-NP\(_{100 nm}\) was investigated in FaDu and primary fibroblasts (FB) by an MTT assay. The clonogenic survival assay was used to evaluate the effects of ZnO-NP alone and in combination with irradiation on FB and FaDu. A formamidopyrimidine-DNA glycosylase (FPG)-modified single-cell microgel electrophoresis (comet) assay was applied to detect oxidative DNA damage in FB as a function of ZnO-NP and irradiation exposure. A significantly increased cytotoxicity after FaDu exposure to ZnO-NP\(_{20 nm}\) or ZnO-NP\(_{100 nm}\) was observed in a concentration of 10 µg/mL or 1 µg/mL respectively in 30 µg/mL of ZnO-NP\(_{20 nm}\) or 20 µg/mL of ZnO-NP\(_{100 nm}\) in FB. The addition of 1, 5, or 10 µg/mL ZnO-NP\(_{20 nm}\) or ZnO-NP\(_{100 nm}\) significantly reduced the clonogenic survival of FaDu after irradiation. The sub-cytotoxic dosage of ZnO-NP\(_{100 nm}\) increased the oxidative DNA damage compared to the irradiated control. This effect was not significant for ZnO-NP\(_{20 nm}\). ZnO-NP showed radiosensitizing properties in the sub-cytotoxic dosage. At least for the ZnO-NP\(_{100 nm}\), an increased level of oxidative stress is a possible mechanism of the radiosensitizing effect.},
  language  = {en}
}
@article{PolatWohllebenKosmalaetal.2022,
  author    = {Polat, B{\"u}lent and Wohlleben, Gisela and Kosmala, Rebekka and Lisowski, Dominik and Mantel, Frederick and Lewitzki, Victor and L{\"o}hr, Mario and Blum, Robert and Herud, Petra and Flentje, Michael and Monoranu, Camelia-Maria},
  title     = {Differences in stem cell marker and osteopontin expression in primary and recurrent glioblastoma},
  series = {Cancer Cell International},
  volume    = {22},
  journal   = {Cancer Cell International},
  issn      = {1475-2867},
  doi       = {10.1186/s12935-022-02510-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301240},
  year      = {2022},
  abstract  = {Background Despite of a multimodal approach, recurrences can hardly be prevented in glioblastoma. This may be in part due to so called glioma stem cells. However, there is no established marker to identify these stem cells. Methods Paired samples from glioma patients were analyzed by immunohistochemistry for expression of the following stem cell markers: CD133, Musashi, Nanog, Nestin, octamer-binding transcription factor 4 (Oct4), and sex determining region Y-box 2 (Sox2). In addition, the expression of osteopontin (OPN) was investigated. The relative number of positively stained cells was determined. By means of Kaplan-Meier analysis, a possible association with overall survival by marker expression was investigated. Results Sixty tissue samples from 30 patients (17 male, 13 female) were available for analysis. For Nestin, Musashi and OPN a significant increase was seen. There was also an increase (not significant) for CD133 and Oct4. Patients with mutated Isocitrate Dehydrogenase-1/2 (IDH-1/2) status had a reduced expression for CD133 and Nestin in their recurrent tumors. Significant correlations were seen for CD133 and Nanog between OPN in the primary and recurrent tumor and between CD133 and Nestin in recurrent tumors. By confocal imaging we could demonstrate a co-expression of CD133 and Nestin within recurrent glioma cells. Patients with high CD133 expression had a worse prognosis (22.6 vs 41.1 months, p = 0.013). A similar trend was seen for elevated Nestin levels (24.9 vs 41.1 months, p = 0.08). Conclusions Most of the evaluated markers showed an increased expression in their recurrent tumor. CD133 and Nestin were associated with survival and are candidate markers for further clinical investigation.},
  language  = {en}
}