A study of embryonic stem cell‐related proteins in human astrocytomas: Identification of Nanog as a predictor of survival

Abstract

Recent studies suggest that the regulatory networks controlling the functions of stem cells during development may be abnormally active in human cancers. An embryonic stem cell (ESC) gene signature was found to correlate with a more undifferentiated phenotype of several human cancer types including gliomas, and associated with poor prognosis in breast cancer. In the present study, we used tissue microarrays of 80 low-grade (WHO Grade II) and 98 high-grade human gliomas (WHO Grades III and IV) to investigate the presence of the ESC-related proteins Nanog, Klf4, Oct4, Sox2 and c-Myc by immunohistochemistry. While similar patterns of co-expressed proteins between low-and high-grade gliomas were present, we found up-regulated protein levels of Nanog, Klf4, Oct4 and Sox2 in high-grade gliomas. Survival analysis by Kaplan-Meier analysis revealed a significant shorter survival in the subgroups of low-grade astrocytomas (n 5 42) with high levels of Nanog protein (p 5 0.0067) and of Klf4 protein (p 5 0.0368), in high-grade astrocytomas (n 5 85) with high levels of Nanog (p 5 0.0042), Klf4 (p 5 0.0447), and c-Myc (p 5 0.0078) and in glioblastomas only (n 5 71) with high levels of Nanog (p 5 0.0422) and of c-Myc (p 5 0.0256). In the multivariate model, Nanog was identified as an independent prognostic factor in the subgroups of low-grade astrocytomas (p 5 0.0039), high-grade astrocytomas (p 5 0.0124) and glioblastomas only (p 5 0.0544), together with established clinical variables in these tumors. These findings provide further evidence for the joint regulatory pathways of ESC-related proteins in gliomas and identify Nanog as one of the key players in determining clinical outcome of human astrocytomas.Gliomas are the most common primary tumors of the CNS and are divided into low-grade and high-grade gliomas. 1 Lowgrade gliomas (LGG) in adults are of malignancy Grade II, according to the WHO classification of brain tumors, and commonly occur as astrocytomas, oligodendrogliomas or oligoastrocytomas Grade II. In spite of a relatively favorable prognosis, LGG will eventually transform into high-grade tumors with fatal outcome. 2 High-grade gliomas (HGG) are of Grades III or IV according to the WHO classification. Grade III tumors are referred to as anaplastic gliomas and grade IV is also known as glioblastoma. 1 WHO Grade III tumors of an astrocytic phenotype are highly proliferative, infiltrative tumors but without necrotic areas and/or hyperplastic vasculature, whereas both anaplastic oligodendrogliomas and glioblastomas

Cancer Stem Cells in Glioblastoma Multiforme

“…CSCs in GBM bear the characteristics of ESCs by their expression of similar proteins, making it possible to both characterize and isolate CSCs in GBM (13, 14). A recent report demonstrates an ESC-like signature in high grade (grades 3 and 4) gliomas with upregulation of NANOG, KLF4, OCT4, and SOX2 proteins (15). Upregulation of these proteins has been correlated with poorer survival in both high- and low-grade gliomas (15, 16), although inclusion of gliomas of different grades and their analysis as a single entity means that this study inherently lacks the specificity needed for the characterization of a unique CSC population in GBM.…”

“…A recent report demonstrates an ESC-like signature in high grade (grades 3 and 4) gliomas with upregulation of NANOG, KLF4, OCT4, and SOX2 proteins (15). Upregulation of these proteins has been correlated with poorer survival in both high- and low-grade gliomas (15, 16), although inclusion of gliomas of different grades and their analysis as a single entity means that this study inherently lacks the specificity needed for the characterization of a unique CSC population in GBM. A recent review points to CSCs in GBM possessing a hierarchy, with overlapping phenotypes expressing upstream (ESC) and downstream (progenitor cell) markers (17).…”

Elevated Expression of the C-Type Lectin CD93 in the Glioblastoma Vasculature Regulates Cytoskeletal Rearrangements That Enhance Vessel Function and Reduce Host Survival

“…For this analysis, we included the high-grade astrocytic tumors that were part of a previously described clinical cohort (23). High-grade ependymomas, gliosarcomas, and anaplastic oligodendrogliomas were excluded from this analysis.…”

Differential expression of CXCR4 and CXCR7 with various stem cell markers in paired human primary and recurrent glioblastomas

“…By co-staining of CXCR4 and CXCR7 with stem cell markers we could show in our primary-recurrent GBM cohort that CXCR4 was mostly found on stem-cell marker positive GBM cells, whereas CXCR7 was usually expressed on stem-cell marker negative cells, with exception of the combination CXCR7-KLF-4. An embryonic stem cell gene signature is well known to correlate with a more undifferentiated phenotype in various cancers (28), and a large scale tissue microarray analysis including 80 low-grade and 98 high-grade gliomas showed an upregulated protein level of NANOG, KLF-4, OCT-4 and SOX-2 in highgrade gliomas (29). Several other studies also point to the relevance of neural and embryonic stem cell markers in GBM progression (30)(31)(32)(33)(34)(35)(36).…”