The radiosensitivity of tumour cells depends mainly on their capacity to maintain genomic integrity. This requires efficient repair of radiation-induced DNA double strand breaks, a process governed by the cell cycle. Based on their functions in cell cycle regulation and DNA damage repair, we hypothesised that targeting of CDK2 and CDK9 modifies cancer cell response to radiotherapy. Therefore, we evaluated the significance of CDK2 and CDK9 for the cellular radiation response in a panel of human head and neck squamous cell carcinoma (HNSCC) cell lines. In order to achieve our goal, we performed a series of experiments to measure several key parameters such as clonogenic radiation survival, cell cycling, DNA damage repair and apoptosis. We found that loss of CDK2 radiosensitises mouse embryonic fibroblasts (MEFs) as well as HNSCC two dimensional (2D) cell cultures. However, under more physiological three dimensional (3D) growth conditions in laminin-rich extracellular matrix, targeting of CDK2 failed to modulate the radiosensitivity of HNSCC cells. Moreover, CDK2 attenuated the repair of radiogenic double strand breaks (DSBs) in MEFs as well as SAS and FaDu HNSCC cells indicating a possible role of CDK2 in DNA damage repair. However, we found that CDK2 is dispensable for cell cycle and checkpoint regulation in response to irradiation in SAS and FaDu cells. Taken together, our results suggest that targeting of CDK2 may not provide a therapeutic benefit to overcome HNSCC cell resistance to radiotherapy. We also showed that depletion of CDK9 clearly enhances the radiosensitivity of HNSCC cultures. In addition, the ectopic expression of CDK9 has a radioprotective effect. These findings suggest a potential role of CDK9 in the radiation response of HNSCC cells. Moreover, our study indicates a possible role of CDK9 in the DNA damage repair response and cell cycling of HNSCC cells. Conclusively, on the basis of these data, targeting of CDK9 in addition to conventional radiotherapy might be a viable strategy to overcome cancer cell resistance.

This study investigated several somatostatin analogues labeled with copper-64 for imaging and targeted therapy of SSTr positive cancer. Among three new cross-bridged bifunctional chelators coupled to Y3-TATE, 64Cu-CB-TE2A-Y3-TATE had the most favorable tumor targeting properties. The introduction of ionizable linker groups could not remedy the slow clearance from the kidney, and other modifications will be necessary to resolve this issue. The emerging idea of using the copper-64-labeled somatostatin antagonist 64Cu-CB-TE2A-sst2-ANT as a tumor targeting agent will require further experimentation. This radiopharmaceutical showed promising initial results in a biodistribution study in male Lewis rats, however, it should be compared to 111In-DOTA-sst2-ANT in the same model. Nuclear localization of copper-64 from two somatostatin analogues differing in their chelate stability strengthened the hypothesis of copper-64 dissociation from the bifunctional chelator prior to trafficking to the nucleus. However, the increased nuclear uptake of copper-64 from the less stable 64Cu-TETA-Y3-TATE did not result in a significant effect on cell killing of A427-7 cells. In experiments with [64Cu]copper acetate and the EGFR-antibody 64Cu-DOTA-cetuximab, the tumor suppressor protein p53 was identified as a mediator of the nuclear transport of copper. 64Cu-DOTA-cetuximab was also utilized in five cervical cancer cell lines with a wide range of EGFR expression. EGFR quantification by saturation receptor binding, and EGFR function as determined via internalization of 64Cu-DOTA-cetuximab closely followed the expression pattern of these cell lines found via EGFR mRNA profiling. This constitutes a first step in the evaluation of cetuximab for the treatment, and of 64Cu-DOTA-cetuximab for the imaging of advanced cervical cancer, as EGFR expression on the tumor cell surface clearly can be quantified and visualized with this experimental system. Copper-64 has been used in this study to probe the basic biochemical process of intracellular copper trafficking, and for the targeting of cell surface receptors via radiolabeled peptides and antibodies, providing an example of the powerful combination of radiopharmaceutical chemistry and cell biology.

Background: The naked mole-rat (NMR) is a long-lived and cancer resistant species. Identification of potential anti-cancer and age related mechanisms is of great interest and makes this species eminent to investigate anti-cancer strategies and understand aging mechanisms. Since it is known that the NMR expresses higher liver mRNA-levels of alpha 2-macroglobulin than mice, nothing is known about its structure, functionality or expression level in the NMR compared to the human A2M. Results: Here we show a comprehensive analysis of NMR- and human plasma-A2M, showing a different prediction in glycosylation of NMR-A2M, which results in a higher molecular weight compared to human A2M. Additionally, we found a higher concentration of A2M (8.3±0.44 mg/mL vs. and 4.4±0.20 mg/mL) and a lower total plasma protein content (38.7±1.79 mg/mL vs. 61.7±3.20 mg/mL) in NMR compared to human. NMR-A2M can be transformed by methylamine and trypsin resulting in a conformational change similar to human A2M. NMRA2M is detectable by a polyclonal antibody against human A2M. Determination of tryptic and anti-tryptic activity of NMR and human plasma revealed a higher anti-tryptic activity of the NMR plasma. On the other hand, less proteolytic activity was found in NMR plasma compared to human plasma.

To determine the characteristics, treatments and outcomes of patients with glioblastoma multiforme (GBM) or gliosarcoma (GS) and metastases outside of the central nervous system (CNS).

Die Abschätzung der Prognose für Patienten, insbesondere Kinder mit onkologischen Erkrankungen stellt eine große Herausforderung an die behandelnden Ärzte dar. Vor Beginn einer Therapie werden daher viele Informationen gesammelt, um einen Patienten möglichst gut in eine vordefinierte Risikogruppe stratifizieren und dementsprechend eine mehr oder weniger intensive Therapie anbieten zu können. Diese Einteilungen sind allerdings für keinen Malignomtyp mit 100%-iger Sicherheit möglich. Das ist die Ursache dafür, dass auch in niedrige Risikogruppen eingeteilte Patienten nicht auf die Therapie ansprechen und einen unvorhergesehen schlechten Verlauf zeigen können. Auf der anderen Seite scheint es Patienten zu geben, die trotz initial schlecht eingeschätzter Prognose einen überaschend guten Verlauf nehmen, auf die Therapie gut ansprechen und letztlich geheilt werden können. Einen Beitrag zu leisten, um die Stratifizierung für Kinder, die an einem Neuroblastom erkrankt sind, zu verbessern und damit zu vermeiden, dass einige Patienten unter- oder andere Patienten übertherapiert werden müssen, ist das Ziel dieser Habilitationsarbeit. Zu diesem Zweck wurden differentielle, molekulare Marker in primären humanen Neuroblastomen identifiziert und deren prognostische Bedeutung dargestellt. Einzelne dieser Marker (differentiell expremierte mRNAs) wurden in Zellkultursystemen funktionell untersucht, um deren zellbiologische Funktion, die der jeweiligen prognostischen Bedeutung zugrunde liegen kann zu erklären. Desweiteren konnten genomische Merkmale des amplifizierten genomischen Abschnittes auf Chromosom 2p25 um MYCN beschrieben werden. Darauf basierend konnte eine patientenindividuelle und tumorzellspezifische PCR entwickelt werden (AFS-PCR), die sich als Marker für den Nachweis einer minimalen Resterkrankung eignet.

Conclusion: Surgery should be considered whenever possible. This means that the patient has to be in good clinical condition (Karnofsky performance score > 70), the extracerebral metastases should be stable, the number of cerebral lesions should not exceed more than 3 seedings, and the age of the patient should be below 70 years. Since brain metastases are usually well circumscribed, complete extirpation seems to be possible. Postoperative MRI should be demanded in order to confirm complete extirpation. Additional radiotherapy is indicated in case of subtotal resection of a single lesion and in multiple lesions. In single brain metastasis a prospective randomized trial is necessary to prove whether conventional radiotherapy is essential after surgery in the primary treatment of the tumors or can be delayed until cerebral lesions recur. Radiosurgery is an alternative to surgery in the treatment of metastasis. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Photodynamic therapy (PDT) has shown to be a promising technique to treat various forms of malignant neoplasia. The photodynamic eradication of the tumor cells is achieved by applying a photosensitizer either locally or systemically and following local activation through irradiation of the tumor mass with light of a specific wavelength after a certain time of incubation. Due to preferential accumulation of the photosensitizer in tumor cells, this procedure allows a selective inactivation of the malignant tumor while sparing the surrounding tissue to the greatest extent. These features and requirements make the PDT an attractive therapeutic option for the treatment of retinoblastoma, especially when surgical enucleation is a curative option. This extreme solution is still in use in case of tumours that are resistant to conventional chemotherapy or handled too late due to poor access to medical care in less advanced country. In this study we initially conducted in-vitro investigations of the new cationic water-soluble photo sensitizer tetrahydroporphyrin-tetratosylat (THPTS) regarding its photodynamic effect on human Rb-1 and Y79 retinoblastoma cells. We were able to show, that neither the incubation with THPTS without following illumination, nor the sole illumination showed a considerable effect on the proliferation of the retinoblastoma cells, whereas the incubation with THPTS combined with following illumination led to a maximal cytotoxic effect on the tumor cells. Moreover the phototoxicity was lower in normal primary cells from retinal pigmented epithelium demonstrating a higher phototoxic effect of THPTS in cancer cells than in this normal retinal cell type. The results at hand form an encouraging foundation for further in-vivo studies on the therapeutic potential of this promising photosensitizer for the eyeball and vision preserving as well as potentially curative therapy of retinoblastoma.

Zugl.: Hohenheim, Univ., Diss., 2007

University, Diss., 2007--Frankfurt (Main). / Zsfassung in engl. und dt. Sprache.

Tübingen, Univ., Diss., 2004.