Zurück

ID: 291 (Conflict of Interest: K)

Die Proteinkinase CK2 reguliert die Expression von nerve/glial antigen (NG)2 im Glioblastom

B. M.Schmitt, M. W. Laschke, M. D. Menger, E.Ampofo
Universitätsklinikum des Saarlandes, Homburg (Saar)

Einleitung

Glioblastoma multiforme is the most common and aggressive form of primary brain tumors. Several studies reported that overexpression of nerve/glial antigen (NG)2 in glioblastoma cells is associated with a poor clinical outcome due to an elevated proliferative activity. Accordingly, the proteoglycan NG2 is a promising target for the development of new therapeutic strategies. In preliminary experiments, we found that the pharmacological inhibition of protein kinase CK2 decreases NG2 protein levels. Therefore, the aim of the present study was to investigate the effect of CK2-dependent downregulation of NG2 on underlying gene regulatory mechanisms and associated functions.

Material und Methoden

The human NG2-positive glioblastoma cell lines A1207 and U87 were treated with CK2 inhibitors or CK2 siRNA and expression of NG2 was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR), flow cytometry and Western Blot analysis. The regulatory effect of CK2 inhibition on NG2 gene expression was examined by means of luciferase assays of truncated NG2 promoter fragments. Moreover, NG2-rescue-assays following CK2 inhibition were performed. Cell viability and proliferation were analyzed by lactate dehydrogenase (LDH)-, water-soluble tetrazolium salt (WST)- and BrdU-assays. Finally, the effect of CK2 inhibition on tumor growth and NG2 protein levels was investigated by xenotransplantation of the human NG2-positive glioblastoma cell line A1207 into the flanks of severe combined immunodeficiency (SCID)/beige mice.

Ergebnisse

NG2 protein levels were significantly reduced after CK2 inhibition. Additional qRT-PCR analyses revealed that downregulation of CK2 kinase activity attenuates NG2 gene expression. Within the NG2 promotor we identified a transcriptional active region depending on CK2 activity. The viability of human glioblastoma cells was not affected, whereas cell proliferation was markedly reduced after CK2 inhibition. In addition, NG2 overexpression significantly diminished the anti-proliferative effects of CK2 inhibition. In vivo, we found that CX-4945 treatment of tumor-bearing mice decreases growth and NG2 protein levels of xenograft A1207 tumors.

Schlussfolgerung

Protein kinase CK2 is a regulator of NG2 expression in glioblastoma cells. Hence, targeting NG2 expression by pharmacological CK2 inhibition may provide a novel strategy in the therapy of NG2-positive glioblastoma.