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Accumulating evidence suggests that glioma stem cells (GSCs) are important therapeutic targets in glioblastoma (GBM). In this study, we identified NIMA-related kinase 2 (NEK2) as a functional binding protein of enhancer of zeste homolog 2 (EZH2) that plays a critical role in the posttranslational regulation of EZH2 protein in GSCs. NEK2 was among the most differentially expressed kinase-encoding genes in GSC-containing cultures (glioma spheres), and it was required for in vitro clonogenicity, in vivo tumor propagation, and radioresistance. Mechanistically, the formation of a protein complex comprising NEK2 and EZH2 in glioma spheres phosphorylated and then protected EZH2 from ubiquitination-dependent protein degradation in a NEK2 kinase activity-dependent manner. Clinically, NEK2 expression in patients with glioma was closely associated with EZH2 expression and correlated with a poor prognosis. NEK2 expression was also substantially elevated in recurrent tumors after therapeutic failure compared with primary untreated tumors in matched GBM patients. We designed a NEK2 kinase inhibitor, compound 3a (CMP3a), which efficiently attenuated GBM growth in a mouse model and exhibited a synergistic effect with radiotherapy. These data demonstrate a key role for NEK2 in maintaining GSCs in GBM by stabilizing the EZH2 protein and introduce the small-molecule inhibitor CMP3a as a potential therapeutic agent for GBM. [ABSTRACT FROM AUTHOR]

Objective.: Our objectives were to determine if the erythropoietin receptor (EpoR) has increased expression in epithelial ovarian carcinoma, and if erythropoietin (Epo) confers malignant properties to ovarian cancer cell lines. Methods.: A Western blot analysis of protein lysates from normal ovarian surface epithelial cells and ovarian cancer cell lines was performed. In addition, immunohistochemical (IHC) staining for EpoR in tissue specimens of normal, low malignant potential tumor, and epithelial ovarian carcinoma was performed. Epo effect on ovarian cancer cell lines was investigated by a cytotoxicity assay using a cell line with high (OVCAR3) and low (SKOV3) EpoR expression. Results.: Western blot analysis revealed increased expression of EpoR in multiple ovarian cancer cell lines. IHC staining revealed limited EpoR expression in benign ovarian tissue and increased levels in ovarian low malignant potential (LMP) tumor and carcinoma. This difference between benign ovarian tissue and carcinoma was found to be statistically significant using a quantitative scoring system. In addition, a cytotoxicity assay with paclitaxel and cisplatin revealed an attenuation of cytotoxic effects. Conclusion.: Increased EpoR expression in ovarian LMP tumors and carcinoma is demonstrated by Western blot analysis and IHC staining. Furthermore, adversely effects sensitivity to cisplatin in the ovarian cancer cell lines. These data add to the growing body of evidence suggesting possible detrimental effects of erythropoietin. [Copyright &y& Elsevier]