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

OCT4 Expression in Gliomas Is Dependent on Cell Metabolism

The OCT4 transcription factor is necessary to maintain cell stemness in the early stages of embryogenesis and is involved in the formation of induced pluripotent stem cells, but its role in oncogenesis is not yet entirely clear. In this work, OCT4 expression was investigated in malignant gliomas. Twenty glioma cell lines and a sample of normal adult brain tissue were used. OCT4 expression was found in all studied glioma cell lines but was not detected in normal adult brain tissue. For one of these lines, OCT4 knockdown caused tumor cell death. By varying the culture conditions of these cells, we unexpectedly found that OCT4 expression increased when cells were incubated in serum-free medium, and this effect was significantly enhanced in serum-free and L-glutamine-free medium. L-glutamine and the Krebs cycle, which is slowed down in serum-free medium according to our NMR data, are sources of α-KG. Thus, our data indicate that OCT4 expression in gliomas may be regulated by the α-KG-dependent metabolic reprogramming of cells.

Stemness and clinical features in relation to the subventricular zone in diffuse lower-grade glioma; an exploratory study

Background

The subventricular zone (SVZ) of the human brain is a site of adult stem cell proliferation and a microenvironment for neural stem cells (NSCs). It has been suggested that NSCs in the SVZ are potential cells of origin containing driver mutations of glioblastoma, but their role in the origin of diffuse lower-grade gliomas (dLGGs) is not much studied.

Methods

We included 188 patients ≥18 years with IDH-mutated dLGG (WHO grades 2–3) histologically diagnosed between 2007 and 2020. Tissue microarrays of tumor samples for patients between 2007 and 2016 were used for immunodetection of Nestin, SOX2, SOX9, KLF4, NANOG, CD133 cMYC, and Ki67. DNA methylation profile was used for stemness index (mDNAsi). Tumor contact with the SVZ was assessed and the distance was computed.

Results

Overall, 70.2% of the dLGG had SVZ contact. Tumors with SVZ contact were larger (102.4 vs 30.9 mL, P < .01), the patients were older (44.3 vs 40.4 years, P = .04) and more often had symptoms related to increased intracranial pressure (31.8% vs 7.1%, P < .01). The expression of SOX2, SOX9, Nestin, and Ki67 showed intersample variability, but no difference was found between tumors with or without SVZ contact, nor with the actual distance to the SVZ. mDNAsi was similar between groups (P = .42).

Conclusions

We found no statistical relationship between proximity with the SVZ and mDNAsi or expression of SOX2, SOX9, Nestin, and Ki67 in IDH-mutated dLGG. Our data suggest that the potential impact of SVZ on IDH-mutated dLGG is probably not associated with a more stemness-like tumor profile.

Gene Expression Profiling of Glioblastoma to Recognize Potential Biomarker Candidates

Glioblastoma is an aggressive malignant tumor of the brain and spinal cord. Due to the blood–brain barrier, the accessibility of its treatments still remains significantly challenging. Unfortunately, the recurrence rates of glioblastoma upon surgery are very high too. Hence, understanding the molecular drivers of disease progression is valuable. In this study, we aimed to investigate the molecular drivers responsible for glioblastoma progression and identify valid biomarkers. Three microarray expression profiles GSE90604, GSE50601, and GSE134470 containing healthy and glioblastoma-affected samples revealed overlapping differentially expressed genes (DEGs). The interrelational pathway enrichment analysis elucidated the halt of cell cycle checkpoints and activation of signaling pathways and led to the identification of 6 predominant hub genes. Validation of hub genes in comparison with The Cancer Genome Atlas datasets identified the potential biomarkers of glioblastoma. The study evaluated two significantly upregulated genes, SPARC (secreted protein acidic and rich in cysteine) and VIM (vimentin) for glioblastoma. The genes CACNA1E (calcium voltage-gated channel subunit alpha1 e), SH3GL2 (SH3 domain-containing GRB2-like 2, endophilin A1), and DDN (dendrin) were identified as under-expressed genes as compared to the normal and pan-cancer tissues along with prominent putative prognostic biomarker potentials. The genes DDN and SH3GL2 were found to be upregulated in the proneural subtype, while CACNA1E in the mesenchymal subtype of glioblastoma exhibits good prognostic potential. The mutational analysis also revealed the benign, possibly, and probably damaging substitution mutations. The correlation between the DEG and survival in glioblastoma was evaluated using the Kaplan–Meier plots, and VIM had a greater life expectancy of 60.25 months. Overall, this study identified key candidate genes that might serve as predictive biomarkers for glioblastoma.

Glioblastoma Embryonic-like Stem Cells Exhibit Immune-Evasive Phenotype

Simple Summary

Most glioblastoma (GBM) patients relapse after an initial response to treatment. These aggressive traits are often associated with the presence of glioma stem cells (GSCs) within the tumor bulk, which are thought to participate in GBM therapy resistance. Given GBM cellular heterogeneity, we hypothesized that GSCs might also display cellular hierarchies associated with different degrees of stemness. Based on single-cell RNAseq data from GBM patients, we identified a subpopulation of GSCs, named core-GSCs (c-GSCs), with a similar profile to embryonic stem cells and downregulation of immune-associated pathways. In addition, we developed an in vitro induced c-GSC (ic-GSC) model resembling their tumor counterpart. The characterization of immune-privileged c-GSCs provides a valuable resource to study immune evasion mechanisms in GBM and to identify potential unexplored targets to improve immunotherapy treatments.

Abstract

Background: Glioma stem cells (GSCs) have self-renewal and tumor-initiating capacities involved in drug resistance and immune evasion mechanisms in glioblastoma (GBM). Methods: Core-GSCs (c-GSCs) were identified by selecting cells co-expressing high levels of embryonic stem cell (ESC) markers from a single-cell RNA-seq patient-derived GBM dataset (n = 28). Induced c-GSCs (ic-GSCs) were generated by reprogramming GBM-derived cells (GBM-DCs) using induced pluripotent stem cell (iPSC) technology. The characterization of ic-GSCs and GBM-DCs was conducted by immunostaining, transcriptomic, and DNA methylation (DNAm) analysis. Results: We identified a GSC population (4.22% ± 0.59) exhibiting concurrent high expression of ESC markers and downregulation of immune-associated pathways, named c-GSCs. In vitro ic-GSCs presented high expression of ESC markers and downregulation of antigen presentation HLA proteins. Transcriptomic analysis revealed a strong agreement of enriched biological pathways between tumor c-GSCs and in vitro ic-GSCs (κ = 0.71). Integration of our epigenomic profiling with 833 functional ENCODE epigenetic maps identifies increased DNA methylation on HLA genes’ regulatory regions associated with polycomb repressive marks in a stem-like phenotype. Conclusions: This study unravels glioblastoma immune-evasive mechanisms involving a c-GSC population. In addition, it provides a cellular model with paired gene expression, and DNA methylation maps to explore potential therapeutic complements for GBM immunotherapy.

The Embryonic Key Pluripotent Factor NANOG Mediates Glioblastoma Cell Migration via the SDF1/CXCR4 Pathway

NANOG is a key transcription factor required for maintaining pluripotency of embryonic stem cells. Elevated NANOG expression levels have been reported in many types of human cancers, including lung, oral, prostate, stomach, breast, and brain. Several studies reported the correlation between NANOG expression and tumor metastasis, revealing itself as a powerful biomarker of poor prognosis. However, how NANOG regulates tumor progression is still not known. We previously showed in medaka fish that Nanog regulates primordial germ cell migration through Cxcr4b, a chemokine receptor known for its ability to promote migration and metastasis in human cancers. Therefore, we investigated the role of human NANOG in CXCR4-mediated cancer cell migration. Of note, we found that NANOG regulatory elements in the CXCR4 promoter are functionally conserved in medaka fish and humans, suggesting an evolutionary conserved regulatory axis. Moreover, CXCR4 expression requires NANOG in human glioblastoma cells. In addition, transwell assays demonstrated that NANOG regulates cancer cell migration through the SDF1/CXCR4 pathway. Altogether, our results uncover NANOG-CXCR4 as a novel pathway controlling cellular migration and support Nanog as a potential therapeutic target in the treatment of Nanog-dependent tumor progression.

Abuhamad A, Syahir A. Understanding Glioblastoma Biomarkers: Knocking a Mountain with a Hammer

Gliomas are the most frequent and deadly form of human primary brain tumors. Among them, the most common and aggressive type is the high-grade glioblastoma multiforme (GBM), which rapidly grows and renders patients a very poor prognosis. Meanwhile, cancer stem cells (CSCs) have been determined in gliomas and play vital roles in driving tumor growth due to their competency in self-renewal and proliferation. Studies of gliomas have recognized CSCs via specific markers. This review comprehensively examines the current knowledge of the most significant CSCs markers in gliomas in general and in glioblastoma in particular and specifically focuses on their outlook and importance in gliomas CSCs research. We suggest that CSCs should be the superior therapeutic approach by directly targeting the markers. In addition, we highlight the association of these markers with each other in relation to their cascading pathways, and interactions with functional miRNAs, providing the role of the networks axes in glioblastoma signaling pathways.

NANOG expression in human development and cancerogenesis

NANOG is an important stem cell transcription factor involved in human development and cancerogenesis. Its expression is complex and regulated on different levels. Moreover, NANOG protein might regulate hundreds of target genes at the same time. NANOG is crucial for preimplantation development phase and progressively decreases during embryonic stem cells differentiation, thus regulating embryonic and fetal development. Postnatally, NANOG is undetectable or expressed in very low amounts in the majority of human tissues. NANOG re-expression can be detected during cancerogenesis, already in precancerous lesions, with increasing levels of NANOG in high grade dysplasia. NANOG is believed to enable cancer cells to obtain stem-cell like properties, which are believed to be the source of expanding growth, tumor maintenance, metastasis formation, and tumor relapse. High NANOG expression in cancer is frequently associated with advanced stage, poor differentiation, worse overall survival, and resistance to treatment, and is therefore a promising prognostic and predictive marker. We summarize the current knowledge on the role of NANOG in cancerogenesis and development, including our own experience. We provide a critical overview of NANOG as a prognostic and diagnostic factor, including problems regarding its regulation and detection.

Glioma SOX2 expression decreased after adjuvant therapy

BACKGROUND

SOX2 is regarded as an important marker in stem cell. The change of SOX2 expression after adjuvant therapy in high grade glioma (HGG) remains unknown so far. Few patients with recurrent glioma have opportunity to undergo operation once again, so the recurrent glioma samples are scarce. This study tries to analyze SOX2 expression in paired primary and recurrent HGG, aims to better understand the transformation law of SOX2 after adjuvant therapy in HGG.

METHODS

Twenty-four recurrent HGG patients who undergone a second resection were included. 16 patients received adjuvant therapy, the remaining 8 patients didn't receive any adjuvant therapy at all. The protein expression of SOX2 in paired primary and recurrent HGG was tested by immunohistochemistry. The statistical analysis was conducted by IBM SPSS Statistics 19.0.

RESULTS

In primary HGG, SOX2 expression of 3 + , 2 + , 1+ and 0+ were seen in 20 (83.3%), 1 (4.2%), 1 (4.2%) and 2 cases (8.3%), respectively. The expression of SOX2 was decreased in recurrent HGG compared to the paired primary sample (p = 0.001). The decrease of SOX2 was often seen in patients received chemotherapy, radiotherapy or both (p = 0.003). Patients with SOX2 high expression in primary glioma had a longer median PFS than those with SOX2 low expression with marginal statistic significance (12.7 vs. 5.4 months, p = 0.083). For cases with SOX2 high expression in the primary glioma, those had SOX2 low expression after recurrence seemed to have worse prognosis as compared to patients with stable SOX2 high expression (PFS: 10.4 vs. 14.9 months, p = 0.036; OS: 27.0 vs 49.5 months, p = 0.005).

CONCLUSIONS

This is the first study comparing the protein expression of SOX2 in recurrent HGG and its paired primary tumor. SOX2 high expression is common in brain HGG, a tendency of decreased SOX2 expression in recurrent gliomas was evidenced. Lower SOX2 expression was seen in those patients who received adjuvant chemotherapy and/or radiotherapy. Patients with low SOX2 expression in primary HGG usually have poorer prognosis, those with SOX2 expression decreased in recurrent HGG had worse outcome.

Therapeutic Targeting of Cancer Stem Cells in Human Glioblastoma by Manipulating the Renin-Angiotensin System

Patients with glioblastoma (GB), a highly aggressive brain tumor, have a median survival of 14.6 months following neurosurgical resection and adjuvant chemoradiotherapy. Quiescent GB cancer stem cells (CSCs) invariably cause local recurrence. These GB CSCs can be identified by embryonic stem cell markers, express components of the renin-angiotensin system (RAS) and are associated with circulating CSCs. Despite the presence of circulating CSCs, GB patients rarely develop distant metastasis outside the central nervous system. This paper reviews the current literature on GB growth inhibition in relation to CSCs, circulating CSCs, the RAS and the novel therapeutic approach by repurposing drugs that target the RAS to improve overall symptom-free survival and maintain quality of life.

The clinicopathological significance of CD133 and Sox2 in astrocytic glioma

BACKGROUND

The treatment strategies of astrocytoma have not changed considerably due to the restricted appreciation of its biology.

OBJECTIVES

This study aimed to evaluate the expression of the stem cell-related proteins (CD133 and Sox2) and their prognostic value in astrocytic glioma.

METHODS

The immunohistochemical expression of CD133 and Sox2 in 40 patients with an astrocytic glioma of different grades was studied. The recorded data on the overall survival (OS), progression-free survival (PFS) and the response to the therapeutic protocol were collected and lastly analyzed.

RESULTS

CD133 expression was observed in 87.5% of the cases, while positive Sox2 expression was found in all the studied cases. There was a significant association of CD133 expression with the histological grade and the tumor size (p< 0.001). A significant association of Sox2 with the histological grade and the tumor size was noted (p= 0.004, p= 0.006 respectively). Up-regulation of both CD133 and Sox2 had a significant association with poor clinical response to the therapy (p< 0.001 for each). Shorter OS and PFS were related to CD133 and Sox2 overexpression.

CONCLUSIONS

Astrocytoma with CD133 and Sox2 overexpression had an unfavorable prognosis and poor clinical response to the current therapeutic protocol.

Prognostic significance of NANOG expression in solid tumors: a meta-analysis

Purpose

NANOG is a tumor marker and indicates poor prognosis in various neoplasms; however, the evidence is controversial. This meta-analysis investigated the association of NANOG expression and clinicopathological features, and it impact on survival of patients with malignant tumors.

Methods

Studies published through May 31, 2018 were retrieved from PubMed, Web of Science, Embase, and the China National Knowledge Infrastructure. Two researchers independently screened the content and quality of studies and extracted data. Correlations of NANOG expression, clinicopathological variables, and survival were analyzed and the combined odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (95% CIs) were calculated.

Results

Thirty-three articles including 35 data sets of 3,959 patients were analyzed. Overall, elevated NANOG expression was associated with poor overall survival (HR = 2.19; 95% CI: 1.87–2.58, P<0.001) and poor disease-free survival (HR = 2.21, 95% CI: 1.54–3.18, P<0.001). Subgroup analysis found that NANOG expression was associated with worse overall survival in non–small cell lung (HR = 1.87; 95% CI: 1.26–2.76, P = 0.002), head and neck (HR = 2.29; 95% CI: 1.75–3.02, P<0.001), and digestive system (HR = 2.38; 95% CI: 1.95–2.91, P<0.001) cancers. Moreover, we found that high NANOG expression was associated with poor tumor differentiation (OR = 2.63; 95% CI: 1.59–4.55, P = 0.001), lymph node metastasis (OR = 2.59; 95% CI: 1.50–4.47, P = 0.001), advanced TNM stage (OR = 2.22; 95% CI: 1.42–3.45, P<0.001), and T stage (OR = 0.44; 95% CI: 0.20–0.93, P = 0.031).

Conclusion

The evidence supports NANOG as a tumor biomarker to guide clinical management and indicate prognosis. Additional studies are needed to further validate these results.

Krüppel-like factor 4 expression in solid tumor prognosis: A meta-analysis

BACKGROUND

Accumulating studies have demonstrated that Krüppel-like factor 4 (KLF4) can act as a tumor suppressor or oncogene in the carcinogenesis of diverse cancers. The prognostic value of KLF4 in various human solid cancers remains controversial. Thus, the present meta-analysis was conducted to evaluate the prognostic value of KLF4 in solid tumors.

METHODS

Eligible literature was retrieved by searching the PubMed, Embase, and Cochrane Library. Combined hazard ratios (HRs) for overall survival (OS) and disease-free survival (DFS) were assessed using fixed-effects and random-effects models. Meta-regression and subgroup analyses were performed to identify the source of heterogeneity. In addition, publication bias was assessed using Begg's funnel plot and Egger's regression asymmetry test.

RESULTS

The 22 eligible studies finally enrolled a total of 2988 patients to assess the prognostic value of KLF4 in solid tumors. Low KLF4 expression was clearly related to worse OS (HR = 1.71, 95% confidence interval [CI] = 1.30-2.24, P < 0.001) and DFS (HR = 1.74, 95% CI = 1.34-2.26, P < 0.001), indicating that low KLF4 expression could be an independent prognostic factor for poor survival in solid cancers.

CONCLUSION

KLF4 might be a potential marker to predict prognosis in solid cancer patients.

PROX1 is a novel pathway-specific prognostic biomarker for high-grade astrocytomas; results from independent glioblastoma cohorts stratified by age and IDH mutation status

PROX1 is a transcription factor with an essential role in embryonic development and determination of cell fate. In addition, PROX1 has been ascribed suppressive as well as oncogenic roles in several human cancers, including brain tumors. In this study we explored the correlation between PROX1 expression and patient survival in high-grade astrocytomas. For this purpose, we analyzed protein expression in tissue microarrays of tumor samples stratified by patient age and IDH mutation status. We initially screened 86 unselected high-grade astrocytomas, followed by 174 IDH1-R132H1 immunonegative glioblastomas derived from patients aged 60 years and older enrolled in the Nordic phase III trial of elderly patients with newly diagnosed glioblastoma. Representing the younger population of glioblastomas, we studied 80 IDH-wildtype glioblastomas from patients aged 18-60 years. There was no correlation between PROX1 protein and survival for patients with primary glioblastomas included in these cohorts. In contrast, high expression of PROX1 protein predicted shorter survival in the group of patients with IDH-mutant anaplastic astrocytomas and secondary glioblastomas. The prognostic impact of PROX1 in IDH-mutant 1p19q non-codeleted high-grade astrocytomas, as well as the negative findings in primary glioblastomas, was corroborated by gene expression data extracted from the Cancer Genome Atlas. We conclude that PROX1 is a new prognostic biomarker for 1p19q non-codeleted high-grade astrocytomas that have progressed from pre-existing low-grade tumors and harbor IDH mutations.

Tumour stem cells in meningioma: A review

Meningioma is a common intracranial and intraspinal neoplasm accounting for 25-30% of all primary neurological tumours. It is associated with high rates of recurrence especially in higher-grade tumours and lesions located at the skull base. Cancer stem cells are increasingly recognised as the origin of cancer and are attributed to loco-regional recurrence, metastasis and treatment resistance. This review presents the accumulating evidence of the presence of tumour stem cells within meningioma and the stem cell markers being used to characterise this putative primitive population within this common tumour.

High OCT4A levels drive tumorigenicity and metastatic potential of medulloblastoma cells

Medulloblastoma is a highly aggressive pediatric brain tumor, in which sporadic expression of the pluripotency factor OCT4 has been recently correlated with poor patient survival. However the contribution of specific OCT4 isoforms to tumor aggressiveness is still poorly understood. Here, we report that medulloblastoma cells stably overexpressing the OCT4A isoform displayed enhanced clonogenic, tumorsphere generation, and invasion capabilities. Moreover, in an orthotopic metastatic model of medulloblastoma, OCT4A overexpressing cells generated more developed, aggressive and infiltrative tumors, with tumor-bearing mice attaining advanced metastatic disease and shorter survival rates. Pro-oncogenic OCT4A effects were expression-level dependent and accompanied by distinct chromosomal aberrations. OCT4A overexpression in medulloblastoma cells also induced a marked differential expression of non-coding RNAs, including poorly characterized long non-coding RNAs and small nucleolar RNAs. Altogether, our findings support the relevance of pluripotency-related factors in the aggravation of medulloblastoma traits classically associated with poor clinical outcome, and underscore the prognostic and therapeutic value of OCT4A in this challenging type of pediatric brain cancer.

Prognostic implication of NOTCH1 in early stage oral squamous cell cancer with occult metastases

OBJECTIVE

The objective of this study was to explore the prognostic value of cancer stem cell markers, namely CD133, NANOG, and NOTCH1, in early stage oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

One hundred forty-four patients with early stage (cT1T2N0) OSCC were identified from a pre-existing database of patients with oral cancer. We examined the impact of the immunohistochemical expression of CD133, NANOG, and NOTCH1 in OSCC. Overall survival (OS) curves were calculated using the Kaplan-Meier method. Predictors of outcome were identified using multivariate analysis.

RESULTS

We found that CD133, NANOG, and NOTCH1 were significantly associated with lymph node metastasis, and NOTCH1 was also significantly associated with depth of invasion and locoregional recurrence.

CONCLUSIONS

NOTCH1 was identified as an independent prognostic factor for OS.

CLINICAL RELEVANCE

NOTCH1 might prove to be a useful indicator for high-risk patients with occult metastases from early stage OSCC.

Methylated cis-regulatory elements mediate KLF4-dependent gene transactivation and cell migration

Altered DNA methylation status is associated with human diseases and cancer; however, the underlying molecular mechanisms remain elusive. We previously identified many human transcription factors, including Krüppel-like factor 4 (KLF4), as sequence-specific DNA methylation readers that preferentially recognize methylated CpG (mCpG), here we report the biological function of mCpG-dependent gene regulation by KLF4 in glioblastoma cells. We show that KLF4 promotes cell adhesion, migration, and morphological changes, all of which are abolished by R458A mutation. Surprisingly, 116 genes are directly activated via mCpG-dependent KLF4 binding activity. In-depth mechanistic studies reveal that recruitment of KLF4 to the methylated cis-regulatory elements of these genes result in chromatin remodeling and transcription activation. Our study demonstrates a new paradigm of DNA methylation-mediated gene activation and chromatin remodeling, and provides a general framework to dissect the biological functions of DNA methylation readers and effectors.

Expression and Prognostic Value of Oct-4 in Astrocytic Brain Tumors

Background

Glioblastomas are the most frequent type of malignant primary brain tumor with a median overall survival less than 15 months. Therapy resistance of glioblastomas has been attributed to the presence of tumor initiating stem-like cells (TSCs). TSC-related markers have therefore been suggested to have promising potentials as prognostic markers in gliomas.

Methodology/Principal Findings

The aim of the present study was to investigate the expression and prognostic impact of the TSC-related marker Oct-4 in astrocytic brain tumors of increasing grade. In total 114 grade II, III and IV astrocytic brain tumors were immunohistochemically stained for Oct-4, and the fraction and intensity of Oct-4 positive cells were determined by morphometric analysis of full tumor sections. Oct-4 was expressed in all tumors, and the Oct-4 positive cell fraction increased with tumor grade (p = 0.045). There was no association between survival and Oct-4 positive cell fraction, neither when combining all tumor grades nor in analysis of individual grades. Oct-4 intensity was not associated with grade, but taking IDH1 status into account we found a tendency for high Oct-4 intensity to be associated with poor prognosis in anaplastic astrocytomas. Double immunofluorescence stainings showed co-localization in the perivascular niches of Oct-4 and two other TSC markers CD133 and nestin in glioblastomas. In some areas Oct-4 was expressed independently of CD133 and nestin.

Conclusions

In conclusion, high Oct-4 fraction was associated with tumor malignancy, but seemed to be without independent prognostic influence in glioblastomas. Identification of a potential prognostic value in anaplastic astrocytomas requires additional studies using larger patient cohorts.

Cancer Stem Cells in Moderately Differentiated Buccal Mucosal Squamous Cell Carcinoma Express Components of the Renin-Angiotensin System

AIM

We have recently identified and characterized cancer stem cell (CSC) subpopulations within moderately differentiated buccal mucosal squamous cell carcinoma (MDBMSCC). We hypothesized that these CSCs express components of the renin-angiotensin system (RAS).

METHODS

3,3'-Diaminobenzidine (DAB) immunohistochemical (IHC) staining was performed on formalin-fixed paraffin-embedded MDBMSCC samples to investigate the expression of the components of the RAS: (pro)renin receptor (PRR), angiotensin converting enzyme (ACE), angiotensin II receptor 1 (ATIIR1), and angiotensin II receptor 2 (ATIIR2). NanoString mRNA gene expression analysis and Western Blotting (WB) were performed on snap-frozen MDBMSCC samples to confirm gene expression and translation of these transcripts, respectively. Double immunofluorescent (IF) IHC staining of these components of the RAS with the embryonic stem cell markers OCT4 or SALL4 was performed to demonstrate their localization in relation to the CSC subpopulations within MDBMSCC.

RESULTS

DAB IHC staining demonstrated expression of PRR, ACE, ATIIR1, and ATIIR2 in MDBMSCC. IF IHC staining showed that PRR was expressed by the CSC subpopulations within the tumor nests, the peri-tumoral stroma, and the endothelium of the microvessels within the peri-tumoral stroma. ATIIR1 and ATIIR2 were localized to the CSC subpopulations within the tumor nests and the peri-tumoral stroma, while ACE was localized to the endothelium of the microvessels within the peri-tumoral stroma. WB and NanoString analyses confirmed protein expression and transcription activation of PRR, ACE, and ATIIR1, but not of ATIIR2, respectively.

CONCLUSION

Our novel findings of the presence and localization of PRR, ACE, ATIIR1, and potentially ATIIR2 to the CSC subpopulations within MDBMSCC suggest CSC as a therapeutic target by modulation of the RAS.

CRISPR/Cas9-mediated gene knockout of NANOG and NANOGP8 decreases the malignant potential of prostate cancer cells

NANOG expression in prostate cancer is highly correlated with cancer stem cell characteristics and resistance to androgen deprivation. However, it is not clear whether NANOG or its pseudogenes contribute to the malignant potential of cancer. We established NANOG- and NANOGP8-knockout DU145 prostate cancer cell lines using the CRISPR/Cas9 system. Knockouts of NANOG and NANOGP8 significantly attenuated malignant potential, including sphere formation, anchorage-independent growth, migration capability, and drug resistance, compared to parental DU145 cells. NANOG and NANOGP8 knockout did not inhibit in vitro cell proliferation, but in vivo tumorigenic potential decreased significantly. These phenotypes were recovered in NANOG- and NANOGP8-rescued cell lines. These results indicate that NANOG and NANOGP8 proteins are expressed in prostate cancer cell lines, and NANOG and NANOGP8 equally contribute to the high malignant potential of prostate cancer.

Stem cell markers in glioma progression and recurrence

Aggressive cancer cells show histological similarities to embryonic stem cells. As differentiated cells can re-acquire pluripotency and self-renewal by transfection with the transcription factors OCT4, SOX2, KLF4 and MYC, with Nanog as readout for success, we comprehensively investigated their occurrence and frequency in human astrocytomas of different malignancy grades, primary and matched recurrent glioblastomas, short- and long-term glioblastoma cultures and glioma cell lines. Among astrocytomas, mRNA expression of OCT4, MYC and (less robust) KLF4 increased with malignancy, while in recurrent glioblastomas MYC expression slightly decreased. Correlation analysis revealed distinct positive correlation between distinct stem cell markers, and this effect was most prominent in the recurrent glioblastoma cohort. In situ, embryonic stem cell factors were found also in more differentiated tumor regions. Respective cells were rarely actively proliferating and showed single or combined expression signatures, which, at least in parts, corresponded to observed positive correlations of mRNA expression. However, a 'master-marker' defining the complete glioma stem cell subset could not be confirmed. In glioma cell lines, long- and short-term cultures, embryonic markers were detected at comparable levels. Upon exposure to temozolomide, increased expression of KLF4 (and lesser Nanog and OCT4) was observed. Experimental intrinsic overexpression of SOX2, KLF4 or OCT4 did not affect the other stem cell factors. The embryonic stem cell factors comprehensively investigated in this project can control self-renewal and pluripotency, and therefore tumorigenicity. They should be considered for the development of future diagnostic and therapeutic strategies.

Cancer Stem Cells in Glioblastoma Multiforme

Aim

To identify and characterize cancer stem cells (CSC) in glioblastoma multiforme (GBM).

Methods

Four-micrometer thick formalin-fixed paraffin-embedded GBM samples from six patients underwent 3,3-diaminobenzidine (DAB) and immunofluorescent (IF) immunohistochemical (IHC) staining for the embryonic stem cell (ESC) markers NANOG, OCT4, SALL4, SOX2, and pSTAT3. IF IHC staining was performed to demonstrate co-expression of these markers with GFAP. The protein expression and the transcriptional activities of the genes encoding NANOG, OCT4, SOX2, SALL4, and STAT3 were investigated using Western blotting (WB) and NanoString gene expression analysis, respectively.

Results

DAB and IF IHC staining demonstrated the presence of a CSC population expressing NANOG, OCT4, SOX2, SALL4, and pSTAT3 with the almost ubiquitous presence of SOX2 and a relatively low abundance of OCT4, within GBM. The expression of NANOG, SOX2 and, pSTAT3 but, not OCT and SALL4, was confirmed by WB. NanoString gene analysis demonstrated transcriptional activation of NANOG, OCT4, SALL4, STAT3, and SOX2 in GBM.

Conclusion

This study demonstrated a population of CSCs within GBM characterized by the expression of the CSC markers NANOG, SALL4, SOX2, pSTAT3 and OCT4 at the protein and mRNA levels. The almost ubiquitous presence of SOX2 and a relatively low abundance of OCT4 would support the putative existence of a stem cell hierarchy within GBM.

Electrochemical detection of Nanog in cell extracts via target-induced resolution of an electrode-bound DNA pseudoknot

Nanog is among the most important indicators of cell pluripotency and self-renew, so detection of Nanog is critical for tumor assessment and monitoring of clinical prognosis. In this work, a novel method for Nanog detection is proposed by using electrochemical technique based on target-induced conformational change of an electrode-bound DNA pseudoknot. In the absence of Nanog, the rigid structure of the pseudoknot will minimize the connection between the redox tag and the electrode, thus reducing the obtained faradaic current. Nevertheless, the Nanog binding may liberate the flexible single-stranded element that transforms the DNA pesudokont into DNA hairpin structure due to steric hindrance effect, thus making the electrochemical tag close to the electrode surface. Consequently, electron transfer can be enhanced and very well electrochemical response can be observed. By using the proposed method, Nanog can be determined in a linear range from 2nM to 25nM with a detection limit of 163 pM. Furthermore, the proposed method can be directly used to assay Nanog not only in purified samples but also in complex media (cell extracts), which shows potential applications in Nanog functional studies as well as clinical diagnosis in the future.

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

The chemokine CXCL12 (also termed SDF-1, stromal cell-derived factor-1) and its receptors CXCR4 and CXCR7 are known to play a pivotal role in tumor progression including glioblastomas (GBM). Previous investigations focused on the expression and functional roles of CXCR4 and CXCR7 in different GBM cell subpopulations, but comparative analysis in matched primary versus recurrent GBM samples are still lacking. Thus, here we investigated the expression of CXCR4 and CXCR7 on mRNA and protein level using matched primary and recurrent GBM pairs. Additionally, as GBM CXCR4-positive stem-like cells are supposed to give rise to recurrence, we compared the expression of both receptors in primary and recurrent GBM cells expressing either neural (MUSASHI-1) or embryonic stem cell markers (KLF-4, OCT-4, SOX-2, NANOG). We were able to show that both CXCR4 and CXCR7 were expressed at considerable mRNA and protein levels. CXCR7 was downregulated in relapse cases, and different groups regarding CXCR4/CXCR7 expression differences between primary and recurrent samples could be distinguished. A co-expression of both receptors was rare. In line with this, CXCR4 was co-expressed with all investigated neural and embryonic stem cell markers in both primary and recurrent tissues, whereas CXCR7 was mostly found on stem cell marker-negative cells, but was co-expressed with KLF-4 on a distinct GBM cell subpopulation. These results point to an individual role of CXCR4 and CXCR7 in stem cell marker-positive GBM cells in glioma progression and underline the opportunity to develop new therapeutic tools for GBM intervention.

The Transcription Regulator Krüppel-Like Factor 4 and Its Dual Roles of Oncogene in Glioblastoma and Tumor Suppressor in Neuroblastoma

The Krüppel-like factor 4 (KLF4) gene is located on chromosome 9q31. All of the currently known 17 KLF transcription regulators that have similarity with members of the specificity protein family are distinctly characterized by the Cys₂/His₂ zinc finger motifs at their carboxyl terminals for preferential binding to the GC/GT box or the CACCC element of the gene promoter and enhancer regions. KLF4 is a transcriptional regulator of cell proliferation, differentiation, apoptosis, migration, and invasion, emphasizing its importance in diagnosis and prognosis of particular tumors. KLF4 has been implicated in tumor progression as well as in tumor suppression, depending on tumor types and contexts. Different studies so far strongly suggest that KLF4 acts as an oncogene in glioblastoma, which is the most malignant and prevalent brain tumor in human adult. It is now well established that the presence of glioblastoma stem cells (GSCs) in glioblastoma causes therapy resistance and progressive growth of the tumor. Because KLF4 is one of the key stemness factors in GSCs, it is likely that KLF4 contributes significantly to the survival of GSCs and the recurrence of glioblastoma. On the other hand, recent studies show that KLF4 can act as a tumor suppressor in human malignant neuroblastoma, which is a deadly tumor mostly in children, by inhibiting the cell cycle and activating the cell differentiation and death pathways. Our increasing understanding of the molecular mechanisms of the contrasting roles of KLF4 in glioblastoma and neuroblastoma is useful for superior diagnosis, therapy, and prognosis of these tumors of the nervous system.

Expression of Oct4, Smad1 and Smad2 in gastric cancer

AIM: To detect the expression of octamer-binding transcription factor-4 (Oct4) and drosophila mothers against decapentaplegic protein (Smad) 1 and 2 in gastric cancer, and to discuss their interactions.

METHODS: We collected 60 cases of gastric cancer (adenocarcinoma) and 25 cases of normal gastric tissue (above 10 cm from the tumor edge) to detect Oct4, Smad1 and Smad2 gene expression by quantitative real-time PCR technique and protein expression by Western blot.

RESULTS: Oct4 expression was significantly higher in gastric cancer than in normal gastric tissue (P < 0.05). Oct4 expression was significantly lower in well and moderately differentiated gastric cancer than in poorly differentiated gastric cancer (P < 0.05). Oct4 expression increased along with the increase of TNM stage (P < 0.05). Oct4 expression was significantly higher in gastric cancer with lymph node metastasis than in without (P < 0.05). Smad1 and Smad2 expression was significantly higher in normal gastric tissue than in gastric cancer (P < 0.05). Smad1 and Smad2 expression was significantly higher in well and moderately differentiated gastric cancer than in poorly differentiated gastric cancer (P < 0.05). Smad1 and Smad2 expression decreased along with the increase of TNM stage (P < 0.05). Smad1 and Smad2 expression was significantly lower in gastric cancer with lymph node metastasis than in without (P < 0.05). All the above three indicators had no significant correlation with age or gender (P > 0.05); Oct4 expression was correlated negatively with Smad1 (r = -0.882, P < 0.05) and Smad2 expression (r = -0.859, P < 0.05); Smad1 expression was correlated positively with Smad2 expression (r = 0.905, P < 0.05).

CONCLUSION: Oct4, Smad1 and Smad2 expression may be closely related to the occurrence and development of gastric cancer, and therefore, they may be used as new drug targets for targeted therapy of gastric cancer.

Concise Review: NANOG in Cancer Stem Cells and Tumor Development: An Update and Outstanding Questions

The homeobox domain transcription factor NANOG, a key regulator of embryonic development and cellular reprogramming, has been reported to be broadly expressed in human cancers. Functional studies have provided strong evidence that NANOG possesses protumorigenic attributes. In addition to promoting self-renewal and long-term proliferative potential of stem-like cancer cells, NANOG-mediated oncogenic reprogramming may underlie clinical manifestations of malignant disease. In this review, we examine the molecular origin, expression, biological activities, and mechanisms of action of NANOG in various malignancies. We also consider clinical implications such as correlations between NANOG expression and cancer prognosis and/or response to therapy. We surmise that NANOG potentiates the molecular circuitry of tumorigenesis, and thus may represent a novel therapeutic target or biomarker for the diagnosis, prognosis, and treatment outcome of cancer. Finally, we present critical pending questions relating NANOG to cancer stem cells and tumor development.

FGF2 as a potential prognostic biomarker for proneural glioma patients

BACKGROUND

The survival of high-grade glioma patients is poor and the treatment of these patients can cause severe side effects. This fosters the necessity to identify prognostic biomarkers, in order to optimize treatment and diminish unnecessary suffering of patients. The aim of this study was to identify prognostic biomarkers for high-grade glioma patients.

METHODS

Eleven proteins were selected for analysis due to their suggested importance for survival of patients with other types of cancers and due to a high variation in protein levels between glioma patients (according to the Human Protein Atlas, www.proteinatlas.org). Protein expression patterns of these 11 proteins were analyzed by immunohistochemistry in tumor samples from 97 high-grade glioma patients. The prognostic values of the proteins were analyzed with univariate and multivariate Cox regression analyses for the high-grade glioma patients, including subgroup analyses of histological subtypes and immunohistochemically defined molecular subtypes.

RESULTS

The proteins with the most significant (univariate and multivariate p<0.05) correlations were analyzed further with cross-validated Kaplan-Meier analyses for the possibility of predicting survival based on the protein expression pattern of the corresponding candidate. Random Forest classification with variable subset selection was used to analyze if a protein signature consisting of any combination of the 11 proteins could predict survival for the high-grade glioma patients and the subgroup with glioblastoma patients. The proteins which correlated most significantly (univariate and multivariate p<0.05) to survival in the Cox regression analyses were Myc for all high-grade gliomas and FGF2, CA9 and CD44 for the subgroup of proneural gliomas, with FGF2 having a strong negative predictive value for survival. No prognostic signature of the proteins could be found.

CONCLUSION

FGF2 is a potential prognostic biomarker for proneural glioma patients, and warrants further investigation.

Deregulated proliferation and differentiation in brain tumors

Neurogenesis, the generation of new neurons, is deregulated in neural stem cell (NSC)- and progenitor-derived murine models of malignant medulloblastoma and glioma, the most common brain tumors of children and adults, respectively. Molecular characterization of human malignant brain tumors, and in particular brain tumor stem cells (BTSCs), has identified neurodevelopmental transcription factors, microRNAs, and epigenetic factors known to inhibit neuronal and glial differentiation. We are starting to understand how these factors are regulated by the major oncogenic drivers in malignant brain tumors. In this review, we will focus on the molecular switches that block normal neuronal differentiation and induce brain tumor formation. Genetic or pharmacological manipulation of these switches in BTSCs has been shown to restore the ability of tumor cells to differentiate. We will discuss potential brain tumor therapies that will promote differentiation in order to reduce treatment resistance, suppress tumor growth, and prevent recurrence in patients.

Glioblastoma stem-like cells: at the root of tumor recurrence and a therapeutic target

Glioblastoma is the most common and most aggressive primary brain malignancy. The current initial standard of care consists of maximal safe surgical resection followed by radical radiotherapy and adjuvant temozolomide. Despite optimal therapy, median survival is ~15 months from diagnosis in molecularly unselected patients, and <6 months for patients with recurrent disease. Therefore, clinical treatments are currently palliative, not curative. Collectively, current knowledge suggests that the continued tumor growth and recurrence is in part due to the presence of glioma stem-like cells, which display self-renewal and tumorigenic potential. They differ from their more differentiated progeny, as they are more resistant to current treatments. Recurrent disease may be a consequence of the enhancement and/or gain of stem cell-like characteristics during disease progression, together with preferential death of more differentiated tumor cells during treatment, signifying that the cancer stem cell phenotype is a crucial therapeutic target. The limited knowledge of the characteristics of these cells and their response to current clinical treatments warrants intensive investigation with the aim to improve patient survival and/or develop a cure for this disease.

Adult neurogenesis and glial oncogenesis: when the process fails

Malignant brain tumors, including glioblastoma multiforme (GBM), are known for their high degree of invasiveness, aggressiveness, and lethality. These tumors are made up of heterogeneous cell populations and only a small part of these cells (known as cancer stem cells) is responsible for the initiation and recurrence of the tumor. The biology of cancer stem cells and their role in brain tumor growth and therapeutic resistance has been extensively investigated. Recent work suggests that glial tumors arise from neural stem cells that undergo a defective process of differentiation. The understanding of this process might permit the development of novel treatment strategies targeting cancer stem cells. In the present review, we address the mechanisms underlying glial tumor formation, paying special attention to cancer stem cells and the role of the microenvironment in preserving them and promoting tumor growth. Recent advancements in cancer stem cell biology, especially regarding tumor initiation and resistance to chemo- or radiotherapy, have led to the development of novel treatment strategies that focus on the niche of the stem cells that make up the tumor. Encouraging results from preclinical studies predict that these findings will be translated into the clinical field in the near future.