Refine
Document Type
- Article (4)
- Doctoral Thesis (1)
Has Fulltext
- yes (5)
Is part of the Bibliography
- no (5) (remove)
Keywords
- cancer stem cells (5) (remove)
Institute
The view that tumors consist of a homogenous mass of clonal derived cells has dramatically changed in recent years. Tumors harbor an enormous heterogeneity of cells with distinct capabilities and functions. The heterogeneity originates from a differentiation hierarchy of tumor cells, similar to normal tissue organization of stem-cell driven organs, but also from clonal succession of subpopulations by randomly acquired genetic mutations and epigenetic changes. Both scenarios are certainly not mutually exclusive, and also stem and progenitor cells underlie mutational selection. Intratumoral heterogeneity is a major challenge for cancer treatment and disease monitoring. Functional studies revealed that not all tumor cells have the same ability to initiate tumor growth upon transplantation in receptive animal models. The tumorinitiating cells (TICs) were called cancer stem cells due to their similarities to normal tissue stem cells in their molecular and functional properties. They can renew themselves long-term and give rise to tumor cells lacking cancer stem cell properties. However, it is worth stressing here that TICs do not necessarily originate from stem cells, but may have regained stem cell properties. TICs caught major attention since they may provide important steps in the progression of malignant diseases, such as epithelial-to-mesenchymal transition, dissemination, long-term persistence, therapy resistance, and relapse of the disease. The prospective identification of TICs using distinct surface markers would allow their molecular and functional characterization, the design of detection methods for diagnosis and prognosis, and the development of targeted therapies against these detrimental cells. While functional evidence for the existence of TICs were provided for many tumor entities, their marker profile still remains largely undefined and controversial. ...
Glioblastoma is one of the deadliest malignancies and is virtually incurable. Accumulating evidence indicates that a small population of cells with a stem-like phenotype is the major culprit of tumor recurrence. Enhanced DNA repair capacity and expression of stemness marker genes are the main characteristics of these cells. Elimination of this population might delay or prevent tumor recurrence following radiochemotherapy. The aim of this study was to analyze whether interference with the Hedgehog signaling (Hh) pathway or combined Hh/Notch blockade using small-molecule inhibitors can efficiently target these cancer stem cells and sensitize them to therapy. Using tumor sphere lines and primary patient-derived glioma cultures we demonstrate that the Hh pathway inhibitor GANT61 (GANT) and the arsenic trioxide (ATO)-mediated Hh/Notch inhibition are capable to synergistically induce cell death in combination with the natural anticancer agent (−)-Gossypol (Gos). Only ATO in combination with Gos also strongly decreased stemness marker expression and prevented sphere formation and recovery. These synergistic effects were associated with distinct proteomic changes indicating diminished DNA repair and markedly reduced stemness. Finally, using an organotypic brain slice transplantation model, we show that combined ATO/Gos treatment elicits strong growth inhibition or even complete elimination of tumors. Collectively, our data show for the first time that ATO and Gos, two drugs that can be used in the clinic, represent a promising targeted therapy approach for the synergistic elimination of glioma stem-like cells.
Cancer stem cells (CSCs) are nowadays one of the major focuses in tumor research since this subpopulation was revealed to be a great obstacle for successful treatment. The identification of CSCs in pediatric solid tumors harbors major challenges because of the immature character of these tumors. Here, we present CD34, CD90, OV-6 and cell-surface vimentin (csVimentin) as reliable markers to identify CSCs in hepatoblastoma cell lines. We were able to identify CSC characteristics for the subset of CD34+CD90+OV-6+csVimentin+-co-expressing cells, such as pluripotency, self-renewal, increased expression of EMT markers and migration. Treatment with Cisplatin as the standard chemotherapeutic drug in hepatoblastoma therapy further revealed the chemo-resistance of this subset, which is a main characteristic of CSCs. When we treated the cells with the Hsp90 inhibitor 17-AAG, we observed a significant reduction in the CSC subset. With our study, we identified CSCs of hepatoblastoma using CD34, CD90, OV-6 and csVimentin. This set of markers could be helpful to estimate the success of novel therapeutic approaches, as resistant CSCs are responsible for tumor relapses.
Das NANOG2-Gen ist ein Genduplikat des nur in embryonalen Stammzellen exprimierten Stammzellfaktors NANOG1, der eine Schlüsselrolle bei der Pluripotenz und der Selbsterneuerung der Stammzellen und möglicherweise der Krebsstammzellen hat. Zur Analyse, ob NANOG2 die beschriebenen Funktionen von NANOG1 in Gewebestammzellen und Krebsstammzellen übernimmt und ursächlich für die Leukämieentstehung verantwortlich ist, wurden embryonale Zellen und primäre Leukämiezellen auf NANOG2-Expression durch RT-PCR-Experimente, Western Blot Analysen und ChIP Assays untersucht. Dabei konnte eine Methode zur Unterscheidung der NANOG1 und NANOG2-Transkripte etabliert, neue Genstrukturen dieser Gene charakterisiert und NANOG2-Transkripte in hämatopoetischen Stammzellen und in allen primären Leukämiezellen detektiert werden. Außerdem konnte mit Hilfe von Genexpressionsanalysen eine äquivalente Funktion von NANOG2 zu NANOG1 festgestellt werden.
Aberrant activation of hedgehog (Hh) signaling has been observed in a wide variety of tumors and accounts for more than 25% of human cancer deaths. Inhibitors targeting the Hh signal transducer Smoothened (SMO) are widely used and display a good initial efficacy in patients suffering from basal cell carcinoma (BCC); however, a large number of patients relapse. Though SMO mutations may explain acquired therapy resistance, a growing body of evidence suggests that the non-canonical, SMO-independent activation of the Hh pathway in BCC patients can also account for this adverse effect. In this review, we highlight the importance of glioma-associated oncogene (GLI) transcription factors (the main downstream effectors of the canonical and the non-canonical Hh cascade) and their putative role in the regulation of multiple oncogenic signaling pathways. Moreover, we discuss the contribution of the Hh signaling to malignant transformation and propose GLIs as central hubs in tumor signaling networks and thus attractive molecular targets in anti-cancer therapies.