Anhua Wu

Persistence of CD133+ Cells in Human and Mouse Glioma Cell Lines: Detailed Characterization of GL261 Glioma Cells with Cancer Stem Cell-Like Properties

The concept of cancer stem cells suggests that there are malignant stem-like cells within a tumor that are responsible for tumor renewal and resistance to cytotoxic therapies. Studies have identified glioma stem-like cells that extrude Hoechst 33342 dye, representing a double-negative side population (SP) thought to be selectively resistant to drug therapy. A CD133+ stem cell-like subpopulation has been isolated from a human glioma that was enriched for tumor-initiating cells. It is unknown whether CD133+ cells with similar phenotype persist in established glioma cell lines, or if CD133 is a marker of glioma stem-like cells in rodents. We investigated whether CD133+ and SP cells existed in the GL261 cell line, a syngeneic mouse glioma model that is widely used for preclinical and translational research. Intracerebral injection of less than 100 CD133+ GL261 cells formed tumors, whereas it required 10,000 CD133(-) cells to initiate a tumor. CD133+ GL261 cells expressed nestin, formed tumor spheres with high frequency, and differentiated into glial and neuronal-like cells. Similar to GL261, seven human glioma cell lines analyzed also contained a rare CD133+ population. Surprisingly, we found that CD133+ GL261 cells did not reside in the SP, nor did the majority ( approximately 94%) of CD133+ human glioma cells. These results demonstrate that the expression of CD133 in murine glioma cells is associated with enhanced tumorigenicity and a stem-like phenotype. This study also reveals a previously unrecognized level of heterogeneity in glioma cell lines, exposing several populations of cells that have characteristics of cancer stem cells.

In vivo vaccination with tumor cell lysate plus CpG oligodeoxynucleotides eradicates murine glioblastoma

Dendritic cell (DC) vaccines have shown antitumor activity in experimental glioma models and in human glioma patients. The typical approach has been to generate the vaccine ex vivo, by pulsing DCs with tumor lysate or peptides, then administering the DCs back into the patient. This process requires significant expertise and expenses in DC generation. Immature DCs which present antigens to T cells in the absence of appropriate costimulatory signals can lead to induction of immune tolerance. Recent studies have shown that coadministration of toll-like receptor 9 agonists, CpG oligodeoxynucleotides, can promote DC vaccines to break immune tolerance to tumor antigens. We investigated the therapeutic efficacy of in vivo DC activation, by directly administering glioma cell lysate with CpG oligodeoxynucleotides (CpG/lysate), in glioma-bearing mice. Subcutaneous vaccination with CpG/lysate induced a significant increase (P<0.05) in the number of total T cells and activated DCs in lymph nodes draining the vaccination site as compared to mice treated with CpG or tumor lysate alone. Mice vaccinated with CpG/lysate exhibited over 2 times greater median survival than mice in the control groups (P<0.05). Up to 55% of mice vaccinated with CpG/lysate were rendered tumor-free as assessed by survival and bioluminescent imaging. Splenocytes taken from mice vaccinated with CpG/lysate elaborated significantly more IFN-γ production and displayed greater tumor cell lysis activity compared with the control groups (P<0.05). These results suggest direct vaccination with CpG/lysate provides an alternative and effective approach to induce host antitumor immunity and warrants clinical investigation in the immunotherapy of cancer.

Transposon-based interferon gamma gene transfer overcomes limitations of episomal plasmid for immunogene therapy of glioblastoma.

Despite improvements in gene delivery technology, transient expression of plasmid DNA has limited the efficacy of nonviral vectors applied to cancer gene therapy. We previously developed plasmid DNA vectors capable of transgene integration and long-term expression in human glioblastoma cells by utilizing the Sleeping Beauty (SB) transposable element. In this study, we compared the efficacy of interferon gamma (IFN-γ) immunogene therapy using episomal or SB vectors in a syngeneic GL261 glioma model. Gene delivery was achieved by intratumoral convection-enhanced delivery of DNA/polyethylenimine complexes. Only mice treated with SB transposase-encoding DNA to facilitate chromosomal integration exhibited a significant increase in survival (P<0.05). SB-mediated intratumoral gene transfer caused sustained IFN-γ expression assessed by reverse transcription-polymerase chain reaction, of both vector-derived and endogenous IFN-γ, whereas expression following episomal plasmid gene transfer was undetectable within 2 weeks. Median survival was enhanced further when SB-mediated IFN-γ gene transfer was combined with CpG oligodeoxynucleotides as adjuvant therapy. Prolonged survival positively correlated with tumor regression measured by in vivo bioluminescent imaging, and enhanced T-cell activation revealed by the ELISPOT assay. SB appears to improve the efficacy of cytokine gene therapy using nonviral vectors by enhancing the duration of transgene expression.

Bioinformatic profiling identifies an immune-related risk signature for glioblastoma

Objective: To investigate the local immune status and its prognostic value in glioma. Methods: A cohort of 297 glioma samples with whole genome microarray expression data from the Chinese Glioma Genome Atlas database were included for discovery. The Cancer Genome Atlas (TCGA) database was used for validation. Principal components analysis and gene set enrichment analysis were used to explore the bioinformatic implication. Results: Distinct local immune status was identified according to histologic grade. Glioblastoma (GBM) exhibited an enhanced immune phenotype compared to lower grade glioma. We profiled the immune-related gene set and identified 8 genes (FOXO3, IL6, IL10, ZBTB16, CCL18, AIMP1, FCGR2B, and MMP9) with the greatest prognostic value in GBM. A local immune-related risk signature was developed from the genes to distinguish cases as high or low risk of unfavorable prognosis, which could be validated in TCGA database. High-risk patients conferred an enhanced intensity of local immune response compared to low-risk ones. Additionally, the signature exhibited different distribution based on molecular features. The signature had prognostic significance in the stratified cohorts and was identified as an independent prognostic factor for GBM. Conclusions: We profiled the immune status in glioma and established a local immune signature for GBM, which could independently identify patients with a high risk of reduced survival, indicating the relationship between prognosis and local immune response.

A five-miRNA signature with prognostic and predictive value for MGMT promoter-methylated glioblastoma patients

Although O(6)-methylguanine DNA methyltransferase (MGMT) promoter methylation status is an important marker for glioblastoma multiforme (GBM), there is considerable variability in the clinical outcome of patients with similar methylation profiles. The present study aimed to refine the prognostic and predictive value of MGMT promoter status in GBM by identifying a micro (mi)RNA risk signature. Data from The Cancer Genome Atlas was used for this study, with MGMT promoter-methylated samples randomly divided into training and internal validation sets. Data from The Chinese Glioma Genome Atlas was used for independent validation. A five miRNA-based risk signature was established for MGMT promoter-methylated GBM to distinguish cases as high- or low-risk with distinct prognoses, which was confirmed using internal and external validation sets. Importantly, the prognostic value of the signature was significant in different cohorts stratified by clinicopathologic factors and alkylating chemotherapy, and a multivariate Cox analysis found it to be an independent prognostic marker along with age and chemotherapy. Based on these three factors, we developed a quantitative model with greater accuracy for predicting the 1-year survival of patients with MGMT promoter-methylated GBM. These results indicate that the five-miRNA signature is an independent risk predictor for GBM with MGMT promoter methylation and can be used to identify patients at high risk of unfavorable outcome and resistant to alkylating chemotherapy, underscoring its potential for personalized GBM management.

Does the existence of HCMV components predict poor prognosis in glioma

Human cytomegalovirus (HCMV) has been associated with malignant gliomas. The objective of the present study was to further investigate the existence and prognostic value of HCMV components in gliomas. Using immunohistochemical staining, HCMV proteins IE1-72 and pp65 were examined in 67 glioma specimens of various histologic grades, in comparison to 6 -control brain tissue samples. The HCMV DNA was measured in both the tumor tissues and the peripheral blood of the patients, using nested PCR. Kaplan–Meier analysis and Cox proportional hazards models were used to analyzed the prognostic value of HCMV components in glioma tissues. IE1-72 was detected in 76.1xa0% (51/67) of glioma tissues, and pp65 was detected in 65.7xa0% (44/67) of glioma tissues. HCMV DNA was detected in 52.2xa0% (35/67) of glioma tissues and 29.9xa0% (20/67) of peripheral blood samples of glioma patients. These HCMV components were not detected in control brain tissue. However, the existence of HCMV components showed no significant correlation with the prognosis of glioma patients. Our results demonstrate that although HCMV proteins and nucleic acids are present in gliomas, they do not correlate with the prognosis. The role of HCMV in gliomas needs to be carefully interpreted.

HDAC4, a prognostic and chromosomal instability marker, refines the predictive value of MGMT promoter methylation.

AbstractnChromosomal instability is a hallmark of human cancers and is closely linked to tumorigenesis. The prognostic value of molecular signatures of chromosomal instability (CIN) has been validated in various cancers. However, few studies have examined the relationship between CIN and glioma. Histone deacetylases (HDACs) regulate chromosome structure and are linked to the loss of genomic integrity in cancer cells. In this study, the prognostic value of HDAC4 expression and its association with markers of CIN were investigated by analyzing data from our own and four other large sample databases. The results showed that HDAC4 expression is downregulated in high- as compared to low-grade glioma and is associated with a favorable clinical outcome. HDAC4 expression and CIN were closely related in glioma from both functional and statistical standpoints. Moreover, the predictive value of the O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status—a widely used glioma marker—was refined by HDAC4 expression level, which was significantly related to CIN in our study. In conclusion, we propose that HDAC4 expression, a prognostic and CIN marker, enhances the predictive value of MGMT promoter methylation status for identifying patients who will most benefit from radiochemotherapy.

Association between small heat shock protein B11 and the prognostic value of MGMT promoter methylation in patients with high-grade glioma.

OBJECT This study investigated the role and prognostic value of heat shock proteins (HSPs) in glioma. METHODS Data from 3 large databases of glioma samples (Chinese Glioma Genome Atlas, Repository for Molecular Brain Neoplasia Data, and GSE16011), which contained whole-genome messenger RNA microarray expression data and patients clinical data, were analyzed. Immunohistochemical analysis was performed to validate protein expression in another set of 50 glioma specimens. RESULTS Of 28 HSPs, 11 were overexpressed in high-grade glioma (HGG) compared with low-grade glioma. A univariate Cox analysis revealed that HSPB11 has significant prognostic value for each glioma grade, which was validated by a Kaplan-Meier survival analysis. HSPB11 expression was associated with poor prognosis and was independently correlated with overall survival (OS) in HGG. This study further explored the combined role of HSPB11 and other molecular markers in HGG, such as isocitrate dehydrogenase 1 (IDH1) mutation and O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status. HSPB11 expression was able to refine the prognostic value of IDH1 mutation in patients with HGG. However, when combined with MGMT promoter methylation status, among patients with a methylated MGMT promoter, those with lower levels of HSPB11 expression had longer OS and progression-free survival than patients with higher levels of HSPB11 expression or with an unmethylated MGMT promoter. Moreover, within the MGMT promoter methylation group, patients with low levels of HSPB11 expression were more sensitive to combined radiochemotherapy than those with high levels of HSPB11 expression, which may explain why some patients with HGG with a methylated MGMT promoter show tolerance to radiochemotherapy. CONCLUSIONS HSPB11 was identified as a novel prognostic marker in patients with HGG. Together with MGMT promoter methylation status, HSPB11 expression can predict outcome for patients with HGG and identify those who would most benefit from combined radiochemotherapy.

Tumor Purity as an Underlying Key Factor in Glioma

Purpose: Glioma tissues consist of not only glioma cells but also glioma-associated nontumor cells, such as stromal cells and immune cells. These nontumor cells dilute the purity of glioma cells and play important roles in glioma biology. Currently, the implications of variation in glioma purity are not sufficiently clarified. Experimental Design: Here, tumor purity was inferred for 2,249 gliomas and 29 normal brain tissues from 5 cohorts. Based on the transcriptomic profiling method, we classified CGGA and TCGA-RNAseq cohorts as the RNAseq set for discovery. Cases from TCGA-microarray, REMBRANDT, and GSE16011 cohorts were grouped as a microarray set for validation. Tissues from the CGGA cohort were reviewed for histopathologic validation. Results: We found that glioma purity was highly associated with major clinical and molecular features. Low purity cases were more likely to be diagnosed as malignant entities and independently correlated with reduced survival time. Integrating glioma purity into prognostic nomogram significantly improved the predictive validity. Moreover, most recognized prognostic indicators were no longer significantly effective under different purity conditions. These results highlighted the clinical importance of glioma purity. Further analyses found distinct genomic patterns associated with glioma purity. Low purity cases were distinguished by enhanced immune phenotypes. Macrophages, microglia, and neutrophils were mutually associated and enriched in low purity gliomas, whereas only macrophages and neutrophils served as robust indicators for poor prognosis. Conclusions: Glioma purity and relevant nontumor cells within microenvironment confer important clinical, genomic, and biological implications, which should be fully valued for precise classification and clinical prediction. Clin Cancer Res; 23(20); 6279–91. ©2017 AACR.

Can lateral ventricle contact predict the ontogeny and prognosis of glioblastoma

AbstractnLateral ventricle contact (LVC) by glioblastomas has been proposed to reveal their origin and may have prognostic value; however, results from previous studies have been controversial. This study explored the association between LVC and tumor origin and prognosis in glioblastoma patients. Magnetic resonance imaging and clinical data from 115 glioma patients were retrospectively reviewed, and Kaplan–Meier analysis and Cox proportional hazards models were used to assess the occurrence of LVC as a function of survival in 43 glioblastoma patients. The mRNA expression profiles were compared by microarray analysis in LV-contacting and non-LV-contacting glioblastomas (LVCGs and NLVCGs, respectively). The sphere-forming and invasive capabilities of LVCG- and NLVCG-derived stem cells were compared in primary glioma stem cell cultures with tumorsphere formation and Matrigel assays, respectively. LVC was more frequently detected in high-grade gliomas which, along with LVCGs, were significantly larger than low-grade gliomas and NLVCGs. LVC parameters were not independent predictors of glioblastoma patient prognosis; the expression profiles (including stemness genes expression) were similar between LVCGs and NLVCGs, and no significant differences were observed in tumorsphere-forming capacity and invasiveness between stem cells derived from the two glioblastoma types. Our results suggest that the origin of glioblastomas cannot be simply estimated by radiographic LVC, and after standard therapy the prognostic value of LVC needs to be carefully interpreted.