Overexpression of CD44 is associated with a poor prognosis in grade II/III gliomas

Circadian Clock Gene bmal1 Acts as a Tumor Suppressor Gene in a Mice Model of Human Glioblastoma

Glioblastomas derived from malignant astrocytes are the most common primary tumors of the central nervous system in humans, exhibiting very bad prognosis. Treatment with surgery, radiotherapy, and chemotherapy (mainly using temozolomide), generates as much one-year survival. The circadian clock controls different aspects of tumor development, and its role in GBM is beginning to be explored. Here, the role of the canonic circadian clock gene bmal1 was studied in vivo in a nude mice model bearing human GBMs from LN229 cells xenografted orthotopically in the dorsal striatum. For that aim, a bmal1 knock-down was generated in LN229 cells by CRISPR/Cas9 gene editing tool, and tumor progression was followed in male mice by measuring survival, tumor growth, cell proliferation and prognosis with CD44 marker, as well as astrocyte activation in the tumor microenvironment with GFAP and nestin markers. Disruption of bmal1 in the tumor decreased survival, increased tumor growth and CD44 expression, worsened motor performance, as well as increased GFAP expression in astrocytes at tumor microenvironment. In addition, survival and tumor progression was not affected in mice bearing LN229 wild type GBM that underwent circadian disruption by constant light, as compared to mice synchronized to 12:12 light-dark cycles. These results consistently demonstrate in an in vivo orthotopic model of human GBM, that bmal1 has a key role as a tumor suppressor gene regulating GBM progression.

Systems biology approach to identify biomarkers and therapeutic targets for colorectal cancer

Background

Colorectal cancer (CRC), is the third most prevalent cancer across the globe, and is often detected at advanced stage. Late diagnosis of CRC, leave the chemotherapy and radiotherapy as the main options for the possible treatment of the disease which are associated with severe side effects. In the present study, we seek to explore CRC gene expression data using a systems biology framework to identify potential biomarkers and therapeutic targets for earlier diagnosis and treatment of the disease.

Methods

The expression data was retrieved from the gene expression omnibus (GEO). Differential gene expression analysis was conducted using R/Bioconductor package. The PPI network was reconstructed by the STRING. Cystoscope and Gephi software packages were used for visualization and centrality analysis of the PPI network. Clustering analysis of the PPI network was carried out using k-mean algorithm. Gene-set enrichment based on Gene Ontology (GO) and KEGG pathway databases was carried out to identify the biological functions and pathways associated with gene groups. Prognostic value of the selected identified hub genes was examined by survival analysis, using GEPIA.

Results

A total of 848 differentially expressed genes were identified. Centrality analysis of the PPI network resulted in identification of 99 hubs genes. Clustering analysis dissected the PPI network into seven interactive modules. While several DEGs and the central genes in each module have already reported to contribute to CRC progression, survival analysis confirmed high expression of central genes, CCNA2, CD44, and ACAN contribute to poor prognosis of CRC patients. In addition, high expression of TUBA8, AMPD3, TRPC1, ARHGAP6, JPH3, DYRK1A and ACTA1 was found to associate with decreased survival rate.

Conclusion

Our results identified several genes with high centrality in PPI network that contribute to progression of CRC. The fact that several of the identified genes have already been reported to be relevant to diagnosis and treatment of CRC, other highlighted genes with limited literature information may hold potential to be explored in the context of CRC biomarker and drug target discovery.

Hyaluronic acid-functionalized lipoplexes and polyplexes as emerging nanocarriers for receptor-targeted cancer therapy

Cancer is an intricate disease that develops as a response to a combination of hereditary and environmental risk factors, which then result in a variety of changes to the genome. The cluster of differentiation (CD44) is a type of transmembrane glycoprotein that serves as a potential biomarker for cancer stem cells (CSC) and viable targets for therapeutic intervention in the context of cancer therapy. Hyaluronic acid (HA) is a linear polysaccharide that exhibits a notable affinity for the CD44 receptor. This characteristic renders it a promising candidate for therapeutic interventions aimed at selectively targeting CD44-positive cancer cells. Treating cancer via non-viral vector-based gene delivery has changed the notion of curing illness through the incorporation of therapeutic genes into the organism. The objective of this review is to provide an overview of various hyaluronic acid-modified lipoplexes and polyplexes as potential drug delivery methods for specific forms of cancer by effectively targeting CD44.

Nanoparticle-based drug delivery systems targeting cancer cell surfaces

Traditional cancer chemotherapy easily produces serious toxic and side effects due to the lack of specific selection of tumor cells, which restricts its curative effect. Targeted delivery can increase the concentration of drugs in the target site and reduce their toxic and side effects on normal tissues and cells. Biocompatible and surface-modifiable nanocarriers are novel drug delivery systems, which are used to specifically target tumor sites in a controllable way. One of the effective ways to design effective targeting nanocarriers is to decorate with functional ligands, which can bind to specific receptors overexpressed on the surfaces of cancer cells. Various functional ligands, including transferrin, folic acid, polypeptide and hyaluronic acid, have been widely explored to develop tumor-selective drug delivery systems. This review focuses on the research progress of various receptors overexpressed on the surfaces of cancer cells and different nano-delivery systems of anticancer drugs targeted on the surfaces of cancer cells. We believe that through continuous research and development, actively targeted cancer nano-drugs will make a breakthrough and become an indispensable platform for accurate cancer treatment.

miR-3174 Is a New Tumor Suppressor MicroRNA That Inhibits Several Tumor-Promoting Genes in Glioblastoma

microRNAs (miRNAs) play an important role in the pathology of glioblastoma (GBM), which is the most malignant and most common primary malignant brain tumor. miRNAs can target multiple genes simultaneously and are considered as potential therapeutic agents or targets. This study aimed to determine the role of miR-3174 in the pathobiology of GBM using both in vitro and in vivo approaches. This is the first study deciphering the role of miR-3174 in GBM. We studied the expression of miR-3174 and found it to be downregulated in a panel of GBM cell lines, GSCs and tissues relative to astrocytes and normal brain tissue. This finding led us to hypothesize that miR-3174 has a tumor-suppressive role in GBM. Exogenous expression of miR-3174 inhibited GBM cell growth and invasion, and hampered the neurosphere formation ability of GSCs. miR-3174 downregulated the expression of multiple tumor-promoting genes including CD44, MDM2, RHOA, PLAU and CDK6. Further, overexpression of miR-3174 reduced tumor volume in nude mice with intracranial xenografts. Immuno-histochemical study of brain sections with intracranial tumor xenografts revealed the pro-apoptotic and anti-proliferative activity of miR-3174. In conclusion, we demonstrated that miR-3174 has a tumor-suppressive role in GBM and could be exploited for therapeutic purposes.

RUNX1/CD44 axis regulates the proliferation, migration, and immunotherapy of gliomas: A single-cell sequencing analysis

Background

Glioma is one of the most common, primary, and lethal adult brain tumors because of its extreme aggressiveness and poor prognosis. Several recent studies relevant to the immune function of CD44, a transmembrane glycoprotein as a significant hyaluronic acid receptor, have achieved great success, revealing the critical role of CD44 in immune infiltration in gliomas. The overexpression of CD44 has been verified to correlate with cancer aggressiveness and migration, while the clinical and immune features of CD44 expression have not yet been thoroughly characterized in gliomas.

Methods

Molecular and clinical data of glioma collected from publicly available genomic databases were analyzed.

Results

CD44 was up-expressed in malignant gliomas, notably in the 1p/19q non-codeletion cases, isocitrate dehydrogenase (IDH) wild-type, and mesenchymal subtypes in GBM samples. CD44 expression level strongly correlates with stromal and immune cells, mainly infiltrating the glioma microenvironment by single-cell sequencing analysis. Meanwhile, CD44 can be a promising biomarker in predicting immunotherapy responses and mediating the expression of PD-L1. Finally, RUNX1/CD44 axis could promote the proliferation and migration of gliomas.

Conclusions

Therefore, CD44 was responsible for glioma growth and progression. It could potentially lead to a novel target for glioma immunotherapy or a prognostic biomarker.

Recent advances in label-free optical, electrochemical, and electronic biosensors for glioma biomarkers

Gliomas are the most commonly occurring primary brain tumor with poor prognosis and high mortality rate. Currently, the diagnostic and monitoring options for glioma mainly revolve around imaging techniques, which often provide limited information and require supervisory expertise. Liquid biopsy is a great alternative or complementary monitoring protocol that can be implemented along with other standard diagnosis protocols. However, standard detection schemes for sampling and monitoring biomarkers in different biological fluids lack the necessary sensitivity and ability for real-time analysis. Lately, biosensor-based diagnostic and monitoring technology has attracted significant attention due to several advantageous features, including high sensitivity and specificity, high-throughput analysis, minimally invasive, and multiplexing ability. In this review article, we have focused our attention on glioma and presented a literature survey summarizing the diagnostic, prognostic, and predictive biomarkers associated with glioma. Further, we discussed different biosensory approaches reported to date for the detection of specific glioma biomarkers. Current biosensors demonstrate high sensitivity and specificity, which can be used for point-of-care devices or liquid biopsies. However, for real clinical applications, these biosensors lack high-throughput and multiplexed analysis, which can be achieved via integration with microfluidic systems. We shared our perspective on the current state-of-the-art different biosensor-based diagnostic and monitoring technologies reported and the future research scopes. To the best of our knowledge, this is the first review focusing on biosensors for glioma detection, and it is anticipated that the review will offer a new pathway for the development of such biosensors and related diagnostic platforms.

Proteolysis of CD44 at the cell surface controls a downstream protease network

The cell surface receptor cluster of differentiation 44 (CD44) is the main hyaluronan receptor of the human body. At the cell surface, it can be proteolytically processed by different proteases and was shown to interact with different matrix metalloproteinases. Upon proteolytic processing of CD44 and generation of a C-terminal fragment (CTF), an intracellular domain (ICD) is released after intramembranous cleavage by the γ-secretase complex. This intracellular domain then translocates to the nucleus and induces transcriptional activation of target genes. In the past CD44 was identified as a risk gene for different tumor entities and a switch in CD44 isoform expression towards isoform CD44s associates with epithelial to mesenchymal transition (EMT) and cancer cell invasion. Here, we introduce meprin β as a new sheddase of CD44 and use a CRISPR/Cas9 approach to deplete CD44 and its sheddases ADAM10 and MMP14 in HeLa cells. We here identify a regulatory loop at the transcriptional level between ADAM10, CD44, MMP14 and MMP2. We show that this interplay is not only present in our cell model, but also across different human tissues as deduced from GTEx (Gene Tissue Expression) data. Furthermore, we identify a close relation between CD44 and MMP14 that is also reflected in functional assays for cell proliferation, spheroid formation, migration and adhesion.

Fumarate hydratase inhibits non-small cell lung cancer metastasis via inactivation of AMPK and upregulation of DAB2

Lung cancer is one of the leading causes of cancer mortality worldwide. As it is often first diagnosed only when cancer metastasis has already occurred, the development of effective biomarkers for the risk prediction of cancer metastasis, followed by stringent monitoring and the early treatment of high-risk patients, is essential for improving patient survival. Cancer cells exhibit alterations in metabolic pathways that enable them to maintain rapid growth and proliferation, which are quite different from the metabolic pathways of normal cells. Fumarate hydratase (FH, fumarase) is a well-known tricarboxylic acid cycle enzyme that catalyzes the reversible hydration/dehydration of fumarate to malate. The current study sought to investigate the relationship between FH expression levels and the outcome of patients with lung cancer. FH was knocked down in lung cancer cells using shRNA or overexpressed using a vector, and the effect on migration ability was assessed. Furthermore, the role of AMP-activated protein kinase (AMPK) phosphorylation and disabled homolog 2 in the underlying mechanism was investigated using an AMPK inhibitor approach. The results showed that in lung cancer tissues, low FH expression was associated with lymph node metastasis, tumor histology and recurrence. In addition, patients with low FH expression exhibited a poor overall survival in comparison with patients having high FH expression. When FH was overexpressed in lung cancer cells, cell migration was reduced with no effect on cell proliferation. Furthermore, the level of phosphorylated (p-)AMPK, an energy sensor molecule, was upregulated when FH was knocked down in lung cancer cells, and the inhibition of p-AMPK led to an increase in the expression of disabled homolog 2, a tumor suppressor protein. These findings suggest that FH may serve as an effective biomarker for predicting the prognosis of lung cancer and as a therapeutic mediator.

Network of miR-373/miR-520s-CD44 Axis Significantly Inhibits the Growth and Invasion of Human Glioblastoma Cells

BACKGROUND

The expression and regulation of microRNAs (miRNAs) play an important role in glioblastoma (GBM) tumorigenesis, progression and prognosis. Little is known about the role of the miRNA regulatory network of GBM risk-related genes in GBM growth and invasiveness.

METHODS

The UALCAN and Oncomine gene expression dataset were used to explore gene expression profiles in human GBM. The Kaplan-Meier method was performed to evaluate the prognostic values of the GBM-related genes. Multiple bioinformatics databases were analysed to predict the GBM-related genes targeted by miRNAs. A luciferase reporter assay and other molecular cell function experiments were conducted to reveal the mechanisms of interaction between the identified miRNAs and their targets.

RESULTS

The CD44 expression is significantly higher in GBM tissues than that in normal tissues, and negatively correlated with survival duration in GBM patients. In normal physiological conditions, CD44 expression is lower in various parts of the central nervous system than in other organ systems. The mRNA encoding CD44 is a direct target of miR-373 and miR-520s, and this finding was verified by molecular biology experiments. We further found that miR-373 and miR-520s expression was negatively associated with CD44 expression in GBM specimens, and that the miR-373 or miR-520s-CD44 interaction network significantly affected the growth and invasiveness of GBM cells.

CONCLUSION

The miR-373 and miR-520s exert their functions by suppressing CD44 expression in GBM cells, and their expression, together with that of CD44, could thus serve as a valuable biomarker of GBM prognosis.

A novel defined risk signature of interferon response genes predicts the prognosis and correlates with immune infiltration in glioblastoma

BACKGROUND

Interferons (IFNs) have been implemented as anti-tumor immunity agents in clinical trials of glioma, but only a subset of glioblastoma (GBM) patients profits from it. The predictive role of IFNs stimulated genes in GBM needs further exploration to investigate the clinical role of IFNs.

METHODS

This study screened 526 GBM patients from three independent cohorts. The transcriptome data with matching clinical information were analyzed using R. Immunohistochemical staining data from the Human Protein Atlas and DNA methylation data from MethSurv were used for validation in protein and methylation level respectively.

RESULTS

We checked the survival effect of all 491 IFNs response genes, and found 54 genes characterized with significant hazard ratio in overall survival (OS). By protein-protein interaction analysis, 10 hub genes were selected out for subsequent study. And based on the expression of these 10 genes, GBM patients could be divided into two subgroups with significant difference in OS. Furthermore, the least absolute shrinkage and selection operator cox regression model was utilized to construct a multigene risk signature, including STAT3, STAT2 and SOCS3, which could serve as an independent prognostic predictor for GBM. The risk model was validated in two independent GBM cohorts. The GBM patients with high risk scores mainly concentrated in the GBM Mesenchymal subtype. The higher risk group was enriched in hypoxia, angiogenesis, EMT, glycolysis and immune pathways, and had increased Macrophage M2 infiltration and high expression of immune checkpoint CD274 (namely PD-L1).

CONCLUSIONS

Our findings revealed the three-gene risk model could be an independent prognostic predictor for GBM, and they were crucial participants in immunosuppressive microenvironment of GBM.

The Therapeutic Effects of DDP/CD44-shRNA Nanoliposomes in AMF on Ovarian Cancer

Background

Globally, ovarian cancer is one of the most common gynecological malignant tumors, and the overall curative effect has been unsatisfactory for years. Exploring and investigating novel therapeutic strategy for ovarian cancer are an imperative need.

Methods

Using manganese zinc ferrite nanoparticles (PEG-MZF-NPs) as gene transferring vector and drug delivery carrier, a new combinatorial regimen for the target treatment of ovarian cancer by integrating CD44-shRNA, DDP (cisplatin) and magnetic fluid hyperthermia (MFH) together was designed and investigated in vivo and in vitro in this study.

Results

PEG-MZF-NPs/DDP/CD44-shRNA nanoliposomes were successfully prepared, and TEM detection indicated that they were 15–20 nm in diameter, with good magnetothermal effect in AMF, similar to the previously prepared PEG-MZF-NPs. Under the action of AMF, PEG-MZF-NPs/shRNA/DDP nanoliposomes effectively inhibited ovarian tumors’ growth, restrained the cancer cells’ proliferation and invasion, and promoted cell apoptosis. VEGF, survivin, BCL-2, and BCL-xl proteins significantly decreased, while caspase-3 and caspase-9 proteins markedly increased both in vitro and in vivo, far better than any of the individual therapies did. Moreover, no significant effects were found on bone marrow hematopoiesis and liver and kidney function of nude mice intervened by the combinatorial therapeutic regimen.

Conclusion

In the present study, we developed PEG-MZF-NPs/DDP/CD44-shRNA magnetic nanoliposomes and inaugurated an integrated therapy through the synergistic effect of MFH, gene therapy, and chemotherapy, and it shows a satisfactory therapeutic effect on ovarian cancer in vitro and in vivo, much better than any single treatment regimen did, with no significant side effects. This study provides a new promising method for ovarian cancer treatment.

CD44-Mediated Poor Prognosis in Glioma Is Associated With M2-Polarization of Tumor-Associated Macrophages and Immunosuppression

Background

Glioma is the most common primary brain tumor with a poor prognosis. Key genes that are negatively related to prognosis may provide the therapy targets to cure glioma. To clarify the role of CD44 in glioma, we explored its function at bulk-transcriptome, spatial and single-cell transcriptome levels.

Methods

In total, expression profiles with survival data of whole-grade glioma from The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA), RNA-seq data with anatomic information of glioblastoma (GBM) from the Ivy Glioblastoma Atlas Project, RNA-sequencing (RNA-seq) data from recurrent GBM receiving adjuvant anti-PD-1 immunotherapy accessed through GSE121810, and single-cell RNA-seq data of GBM under accession GSE103224 were enrolled in this study. CD44-specific findings were further analyzed by R language.

Results

CD44 is positively correlated with WHO grade of malignancy and is negatively related to prognosis in glioma. Meanwhile, CD44 predominantly expresses in GBM mesenchymal subtype, and gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses reveal that CD44 positively coexpressed genes are closely related to glioma immunity. Moreover, CD44+ cells mainly distribute in perinecrotic region with high expression of immune factors. At single-cell resolution, only malignant tumor cells, tumor-associated macrophages (TAMs), and T cells express CD44 in GBM. CD44+ malignant tumor cells are in mesenchymal-1-like (MES1-like) cellular state, and CD44+ TAMs are in M2 phenotype. CD44+ T cells have high expression of both PD-1 and PD-L1. CD44 and its directly interacted inhibitory immunomodulators are upregulated in patients with nonresponder recurrent GBM treated with PD-1 blockade therapy.

Conclusion

Our work demonstrates that CD44, a new M2 TAM biomarker, is involved in immune suppressor and promote glioma progression in glioma microenvironment. These results expand our understanding of CD44-specific clinical and immune features in glioma.

Association of glioma CD44 expression with glial dynamics in the tumour microenvironment and patient prognosis

Because of the heterogeneity of lower-grade gliomas (LGGs), patients show various survival outcomes that are not reliably predicted by histological classification. The tumour microenvironment (TME) contributes to the initiation and progression of brain LGGs. Identifying potential prognostic markers based on the immune and stromal components in the TME will provide new insights into the dynamic modulation of these two components of the TME in LGGs. We applied ESTIMATE to calculate the ratio of immune and stromal components from The Cancer Genome Atlas database. After combined differential gene expression analysis, protein–protein interaction network construction and survival analysis, CD44 was screened as an independent prognostic factor and subsequently validated utilizing data from the Chinese Glioma Genome Atlas database. To decipher the association of glioma cell CD44 expression with stromal cells in the TME and tumour progression, RT–qPCR, cell viability and wound healing assays were employed to determine whether astrocytes enhance glioma cell viability and migration by upregulating CD44 expression. Surprisingly, M1 macrophages were identified as positively correlated with CD44 expression by CIBERSORT analysis. CD44⁺ glioma cells were further suggested to interact with microglia-derived macrophages (M1 phenotype) via osteopontin signalling on the basis of single-cell sequencing data. Overall, we found that astrocytes could elevate the CD44 expression level of glioma cells, enhancing the recruitment of M1 macrophages that may promote glioma stemness via osteopontin-CD44 signalling. Thus, glioma CD44 expression might coordinate with glial activities in the TME and serve as a potential therapeutic target and prognostic marker for LGGs.

CD44 Promotes Lung Cancer Cell Metastasis through ERK-ZEB1 Signaling

Lung cancer is a malignancy with high mortality worldwide, and metastasis occurs at a high frequency even when cancer spread is not detectable at primary operation. Cancer stemness plays an important role in malignant cancer behavior, treatment resistance, and cancer metastasis. Therefore, understanding the molecular pathogenesis behind cancer-stemness-mediated metastasis and developing effective approaches to prevent metastasis are key issues for improving cancer treatment. In this study, we investigated the role of CD44 stemness marker in lung cancer using in vitro and clinical studies. Immunohistochemical staining of lung cancer tissue specimens revealed that primary tumors with higher CD44 expression showed increased metastasis to regional lymph nodes. Flow cytometry analysis suggested that CD44 positive cells were enriched in the metastatic lymph nodes compared to the primary tumors. CD44 overexpression significantly increased migration and invasion abilities of lung cancer cells through CD44-induced ERK phosphorylation, ZEB1 upregulation, and Claudin-1 downregulation. Furthermore, ERK inhibition suppressed the migration and invasion abilities of CD44-overexpressing lung cancer cells. In summary, our in vitro and clinical results indicate that CD44 may be a potential prognostic and therapeutic marker for lung cancer patients.

Expression of CD44 and the survival in glioma: a meta-analysis

Background: Higher tumor expression of CD44, a marker of cancer stem cells (CSCs), is associated with poor overall survival (OS) in various cancers. However, the association between CD44 and poor OS remains inconsistent in glioma. We aimed to evaluate the potential predictive role of CD44 for prognosis of glioma patients in a meta-analysis.

Methods: Observational studies comparing OS of glioma patients according to the level of CD44 were identified through searching PubMed, Embase, and Cochrane’s Library databases. Meta-analyses were performed with a random- or fixed-effect model according to the heterogeneity. Subgroup analyses were performed to evaluate the influences of study characteristics.

Results: Eleven retrospective cohort studies were included. Results showed that increased CD44 expression in tumor predicted poor OS in glioma patients (hazard ratio [HR]: 1.42, 95% confidence interval [CI]: 1.02–1.97, P=0.04). Subgroup analyses showed that higher tumor CD44 expression significantly predicted poor OS in patients with World Health Organization (WHO) stages II–III glioma (HR: 2.99, 95% CI: 1.53–5.89, P=0.002), but not in patients with glioblastoma (HR: 1.26, 95% CI: 0.76–2.08, P=0.47; P for subgroup difference = 0.03). Results were not statistically different between subgroups according to patient ethnicity, sample size, CD44 detection method, CD44 cutoff, HR estimation, univariate or multivariate analysis, or median follow-up durations (P-values for subgroup difference all >0.10).

Conclusion: Higher tumor expression of CD44 may predict poor survival in patients with glioma, particularly in those with WHO stage II–III glioma.

CD44 as a tumor biomarker and therapeutic target

CD44, a complex transmembrane glycoprotein, exists in multiple molecular forms, including the standard isoform CD44s and CD44 variant isoforms. CD44 participates in multiple physiological processes, and aberrant expression and dysregulation of CD44 contribute to tumor initiation and progression. CD44 represents a common biomarker of cancer stem cells, and promotes epithelial-mesenchymal transition. CD44 is involved in the regulation of diverse vital signaling pathways that modulate cancer proliferation, invasion, metastasis and therapy-resistance, and it is also modulated by a variety of molecules in cancer cells. In addition, CD44 can serve as an adverse prognostic marker among cancer population. The pleiotropic roles of CD44 in carcinoma potentially offering new molecular target for therapeutic intervention. Preclinical and clinical trials for evaluating the pharmacokinetics, efficacy and drug-related toxicity of CD44 monoclonal antibody have been carried out among tumors with CD44 expression. In this review, we focus on current data relevant to CD44, and outline CD44 structure, the regulation of CD44, functional properties of CD44 in carcinogenesis and cancer progression as well as the potential CD44-targeting therapy for cancer management.

Comment on "Expression of CD44 and the survival in glioma: a meta-analysis"

CD44 has been considered as a cancer stem cell marker in various tumors. With great enthusiasm, we read an article written by Wu et al. entitled "Expression of CD44 and the survival in glioma: a meta-analysis" published in Bioscience Reports. The authors performed meta-analyses to study the prognostic significance of CD44 in gliomas, and drew the conclusion that high expression of CD44 may predict poor survival in glioma, particularly in WHO grade II-III gliomas. However, two major defects exist in the present study, which made the meta-analysis on the prognostic significance of CD44 in all gliomas unreliable. In this commentary, we discussed the limitations and significance of the present study.

The predominant expression of cancer stem cell marker ALDH1A3 in tumor infiltrative area is associated with shorter overall survival of human glioblastoma

Background

ALDH1A3 is a cancer stem cell marker in neoplasms including glioblastoma (GBM). However, the comprehensive role of ALDH1A3 in GBM remains unclear. This study attempted to investigate the expression of ALDH1A3 in human GBM tissues and its association with clinical parameters.

Methods

Thirty primary GBM and 9 control were enrolled in this study. ALDH1A3 mRNA and protein expression levels were detected by RT²-PCR and western blot, respectively. Immunohistochemistry and immunofluorescence staining were performed to evaluate the regional and cellular expression manner of ALDH1A3. The association of ALDH1A3 expression with multiple clinical parameters was analyzed.

Results

ALDH1A3 protein level, but not mRNA level, in a subgroup of GBM was significantly higher than that in the control group. ALDH1A3 immunoreactivity was detected heterogeneously in individual GBMs. Fifteen of 30 cases showed a positive of ALDH1A3 immunoreactivity which was predominantly observed in the tumor infiltrative area (TI). Double immunofluorescence staining revealed a co-localization of ALDH1A3 with GFAP in glial-shaped cells and in tumor cells. ALDH1A3 immunoreactivity was often merged with CD44, but not with CD68. Moreover, ALDH1A3 expression was positively associated with the tumor edema grade and inversely with overall survival (OS) (median OS: 16 months vs 10 months), but with neither MGMT promoter methylation status nor Ki67 index in GBM. An upregulation of ALDH1A3 was accompanied by a reduced expression of STAT3β and p-STAT3β.

Conclusions

Inter- and intra-tumoral heterogeneous expression of ALDH1A3 was exhibited in GBMs. A high immunoreactivity of ALDH1A3 in tumor infiltrative area was associated with shorter OS, especially in patients with MGMT promoter methylation. Our findings propose ALDH1A3 not only as a predictive biomarker but also as a potential target for personalized therapy of GBM.

The Role of Cancer Stem Cells in Radiation Resistance

Cancer stem cells (CSC) are a distinct subpopulation within a tumor. They are able to self-renew and differentiate and possess a high capability to repair DNA damage, exhibit low levels of reactive oxygen species (ROS), and proliferate slowly. These features render CSC resistant to various therapies, including radiation therapy (RT). Eradication of all CSC is a requirement for an effective antineoplastic treatment and is therefore of utmost importance for the patient. This makes CSC the prime targets for any therapeutic approach. Albeit clinical data is still scarce, experimental data and first clinical trials give hope that CSC-targeted treatment has the potential to improve antineoplastic therapies, especially for tumors that are known to be treatment resistant, such as glioblastoma. In this review, we will discuss CSC in the context of RT, describe known mechanisms of resistance, examine the possibilities of CSC as biomarkers, and discuss possible new treatment approaches.

Splicing Dysregulation as Oncogenic Driver and Passenger Factor in Brain Tumors

Brain tumors are a heterogeneous group of neoplasms ranging from almost benign to highly aggressive phenotypes. The malignancy of these tumors mostly relies on gene expression reprogramming, which is frequently accompanied by the aberrant regulation of RNA processing mechanisms. In brain tumors, defects in alternative splicing result either from the dysregulation of expression and activity of splicing factors, or from mutations in the genes encoding splicing machinery components. Aberrant splicing regulation can generate dysfunctional proteins that lead to modification of fundamental physiological cellular processes, thus contributing to the development or progression of brain tumors. Herein, we summarize the current knowledge on splicing abnormalities in brain tumors and how these alterations contribute to the disease by sustaining proliferative signaling, escaping growth suppressors, or establishing a tumor microenvironment that fosters angiogenesis and intercellular communications. Lastly, we review recent efforts aimed at developing novel splicing-targeted cancer therapies, which employ oligonucleotide-based approaches or chemical modulators of alternative splicing that elicit an impact on brain tumor biology.

Emerging Role of Cellular Prion Protein in the Maintenance and Expansion of Glioma Stem Cells

Cellular prion protein (PrP^C) is a membrane-anchored glycoprotein representing the physiological counterpart of PrP scrapie (PrP^Sc), which plays a pathogenetic role in prion diseases. Relatively little information is however available about physiological role of PrP^C. Although PrP^C ablation in mice does not induce lethal phenotypes, impairment of neuronal and bone marrow plasticity was reported in embryos and adult animals. In neurons, PrP^C stimulates neurite growth, prevents oxidative stress-dependent cell death, and favors antiapoptotic signaling. However, PrP^C activity is not restricted to post-mitotic neurons, but promotes cell proliferation and migration during embryogenesis and tissue regeneration in adult. PrP^C acts as scaffold to stabilize the binding between different membrane receptors, growth factors, and basement proteins, contributing to tumorigenesis. Indeed, ablation of PrP^C expression reduces cancer cell proliferation and migration and restores cell sensitivity to chemotherapy. Conversely, PrP^C overexpression in cancer stem cells (CSCs) from different tumors, including gliomas—the most malignant brain tumors—is predictive for poor prognosis, and correlates with relapses. The mechanisms of the PrP^C role in tumorigenesis and its molecular partners in this activity are the topic of the present review, with a particular focus on PrP^C contribution to glioma CSCs multipotency, invasiveness, and tumorigenicity.