Epigenetic Silencing of miR-9 Promotes Migration and Invasion by EZH2 in Glioblastoma Cells

The effect of microRNA-9 overexpression on inhibition of melanoma cancer stem cells tumorigenicity

Most of the studies have reported the downregulation of miR-9 in metastatic melanomas compared to primary tumors. They indicated that miR-9 negatively regulates the epithelial-to-mesenchymal transition (EMT) by inhibiting SNAIL1 expression and consequently promotes CDH1 expression. Since the process of EMT is associated to stem cell features, it could be interesting to study the effect of miR-9 on melanoma cancer stem cells. In the present study, we examined the effects of miR-9 manipulation on the stemness potential of melanoma cells. Our data demonstrated that the overexpression of miR-9 in A375 and NA8 cells significantly inhibits the ability of proliferation, self-renewal, migration, and tumorigenicity of melanoma cells which was concomitant with changes in the level of BRAF , some EMT factors, and stemness genes. Likewise, the reduction of miR-9 levels led to an increase in cell proliferation, colony and sphere formation, and the ability of cell migration and tumorigenicity. In conclusion, our results specified the role of miR-9 as a tumor suppressor miRNA to inhibit many aspects of melanoma stem cells, and therefore, it could be a potential candidate for the suppression of melanoma growth and progression.

Development and Validation of CXCR4 Nomogram-Based Immune Infiltration/Tumor Inflammation in Primary Glioblastoma

Glioblastoma (GBM) is a highly malignant and aggressive tumor with poor prognosis. Therefore, the discovery of new prognostic molecular markers is of great significance for clinical prognosis. The CXC chemokine receptor (CXCR) members play a key regulatory role in many cancers. In this study, we explore the clinical value and application of the CXCR members in primary glioblastoma. Two GBM datasets from The Cancer Genome Atlas (TCGA) and The China Glioma Genome Atlas (CGGA) databases were used to explore the relationship between differential expression of CXCRs and GBM subtypes as well as immune infiltration. C-X-C motif chemokine receptor 4 (CXCR4) was screened as an independent prognostic factor, and a nomogram and risk prediction model were developed and tested in the CGGA database using the TCGA database. Receiver operating curve (ROC) and decision curve analysis (DCA) found good accuracy and net benefit of the models. The correlation of CXCR4 with immune infiltration and tumor was analyzed using CancerSEA and TIMER. In in vitro experiments, we found that CXCR4 was significantly overexpressed in glioblastoma and was closely related to the inflammatory response of U251/U87 cells. CXCR4 is an excellent independent prognostic factor for glioblastoma and positively correlates with tumor inflammation.

Progress in targeting PTEN/PI3K/Akt axis in glioblastoma therapy: Revisiting molecular interactions

Glioblastoma (GBM) is one of the most malignant cancers of central nervous system and due to its sensitive location, surgical resection has high risk and therefore, chemotherapy and radiotherapy are utilized for its treatment. However, chemoresistance and radio-resistance are other problems in GBM treatment. Hence, new therapies based on genes are recommended for treatment of GBM. PTEN is a tumor-suppressor operator in cancer that inhibits PI3K/Akt/mTOR axis in diminishing growth, metastasis and drug resistance. In the current review, the function of PTEN/PI3K/Akt axis in GBM progression is evaluated. Mutation or depletion of PTEN leads to increase in GBM progression. Low expression level of PTEN mediates poor prognosis in GBM and by increasing proliferation and invasion, promotes malignancy of tumor cells. Moreover, loss of PTEN signaling can result in therapy resistance in GBM. Activation of PTEN signaling impairs GBM metabolism via glycolysis inhibition. In contrast to PTEN, PI3K/Akt signaling has oncogenic function and during tumor progression, expression level of PI3K/Akt enhances. PI3K/Akt signaling shows positive association with oncogenic pathways and its expression similar to PTEN signaling, is regulated by non-coding RNAs. PTEN upregulation and PI3K/Akt signaling inhibition by anti-cancer agents can be beneficial in interfering GBM progression. This review emphasizes on the signaling networks related to PTEN/PI3K/Akt and provides new insights for targeting this axis in effective GBM treatment.

GSK343, an Inhibitor of Enhancer of Zeste Homolog 2, Reduces Glioblastoma Progression through Inflammatory Process Modulation: Focus on Canonical and Non-Canonical NF-κB/IκBα Pathways

Glioblastoma (GB) is a tumor of the central nervous system characterized by high proliferation and invasiveness. The standard treatment for GB includes radiotherapy and chemotherapy; however, new therapies are needed. Particular attention was given to the role of histone methyltransferase enhancer of zeste-homolog-2 (EZH2) in GB. Recently, several EZH2-inhibitors have been developed, particularly GSK343 is well-known to regulate apoptosis and autophagy processes; however, its abilities to modulate canonical/non-canonical NF-κB/IκBα pathways or an immune response in GB have not yet been investigated. Therefore, this study investigated for the first time the effect of GSK343 on canonical/non-canonical NF-κB/IκBα pathways and the immune response, by an in vitro, in vivo and ex vivo model of GB. In vitro results demonstrated that GSK343 treatments 1, 10 and 25 μM significantly reduced GB cell viability, showing the modulation of canonical/non-canonical NF-κB/IκBα pathway activation. In vivo GSK343 reduced subcutaneous tumor mass, regulating canonical/non-canonical NF-κB/IκBα pathway activation and the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD). Ex vivo results confirmed the anti-proliferative effect of GSK343 and also demonstrated its ability to regulate immune response through CXCL9, CXCL10 and CXCL11 expression in GB. Thus, GSK343 could represent a therapeutic strategy to counteract GB progression, thanks to its ability to modulate canonical/non-canonical NF-κB/IκBα pathways and immune response.

Demystifying the CXCR4 conundrum in cancer biology: Beyond the surface signaling paradigm

The oncogenic chemokine duo CXCR4-CXCL12/SDF-1 (C-X-C Receptor 4-C-X-C Ligand 12/ Stromal-derived factor 1) has been the topic of intense scientific disquisitions since Muller et al., in her ground-breaking research, described this axis as a critical determinant of organ-specific metastasis in breast cancer. Elevated CXCR4 levels correlate with distant metastases, poor prognosis, and unfavourable outcomes in most solid tumors. Therapeutic impediment of the axis in clinics with Food and Drug Administration (FDA) approved inhibitors like AMD3100 or Plerixafor yield dubious results, contrary to pre-clinical developments. Clinical trials entailing inhibition of CXCR7 (C-X-C Receptor 7), another convicted chemokine receptor that exhibits affinity for CXCL12, reveal outcomes analogous to that of CXCR4-CXCL12 axis blockade. Of note, the cellular CXCR4 knockout phenotype varies largely from that of inhibitor treatments. These shaky findings pique great curiosity to delve further into the realm of this infamous chemokine receptor to provide a probable explanation. A multitude of recent reports suggests the presence of an increased intracellular CXCR4 pool in various cancers, both cytoplasmic and nuclear. This intracellular CXCR4 protein reserve seems active as it correlates with vital tumor attributes, viz. prognosis, aggressiveness, metastasis, and disease-free survival. Diminishing this entire intracellular CXCR4 load apart from the surface signals looks encouraging from a therapeutic point of view. Transcending beyond the classically accepted concept of ligand-mediated surface signaling, this review sheds new light on plausible associations of intracellularly compartmentalised CXCR4 with various aspects of tumorigenesis. Besides, this review also puts forward a comprehensive account of CXCR4 regulation in different cancers.

Prometastatic CXCR4 and Histone Methyltransferase EZH2 Are Upregulated in SMARCB1/INI1-Deficient and TP53-Mutated Poorly Differentiated Chordoma

Background: Chordoma is a rare tumor most commonly arising in the sacrococcygeal region from notochord remnants. Usually, these tumors are locally invasive and recurrent, and they have a 5–43% ability to metastasize. A newly-described aggressive variant called poorly differentiated chordoma is different from conventional chordoma in that it does not have the well-differentiated histologic appearance of conventional chordoma and also exhibits the loss of SMARCB1/INI1. Herein, we describe a case of poorly differentiated chordoma with SMARCB1/INI1 loss, a concurrent TP53 mutation, and Rb1 loss. Methods: The patient is a middle-aged man with a history of previously resected sacrococcygeal chordoma, who was found to have new hepatic, lung, and adrenal lesions. Results: Biopsy of the liver lesion showed sheets of malignant epithelioid cells with vacuolated cytoplasm, areas of necrosis, and up to five mitoses in one high-power field. No physaliferous cytologic features or matrix material was seen. After reviewing an extensive panel of immunohistochemical markers, the origin of the metastatic tumor could not be determined; the tumor was only positive for Cam5.2, EMA, and CD56. Brachyury was performed due to the patient’s previous history and was positive. Genomic testing showed a SMARCB1 mutation, TP53 mutation, and RB1 loss. Additional markers were performed, and the tumor showed a Ki-67 proliferation index of approximately 80%, mutant p53 protein, loss of INI1, and strong expression of both the histone methyl transferase EZH2 and the chemokine receptor CXCR4. Conclusions: Poorly differentiated chordoma is a highly aggressive variant of chordoma with few cases reported. This case of SMARCB1/INI-deficient, poorly differentiated chordoma also showed a concurrent TP53 mutation and loss of RB1, which resulted in malignant transformation with upregulation of both prometastatic CXCR4 and the histone methyltransferase EZH2, causing aggressive behavior and metastasis.

The long and short non-coding RNAs modulating EZH2 signaling in cancer

Non-coding RNAs (ncRNAs) are a large family of RNA molecules with no capability in encoding proteins. However, they participate in developmental and biological processes and their abnormal expression affects cancer progression. These RNA molecules can function as upstream mediators of different signaling pathways and enhancer of zeste homolog 2 (EZH2) is among them. Briefly, EZH2 belongs to PRCs family and can exert functional roles in cells due to its methyltransferase activity. EZH2 affects gene expression via inducing H3K27me3. In the present review, our aim is to provide a mechanistic discussion of ncRNAs role in regulating EZH2 expression in different cancers. MiRNAs can dually induce/inhibit EZH2 in cancer cells to affect downstream targets such as Wnt, STAT3 and EMT. Furthermore, miRNAs can regulate therapy response of cancer cells via affecting EZH2 signaling. It is noteworthy that EZH2 can reduce miRNA expression by binding to promoter and exerting its methyltransferase activity. Small-interfering RNA (siRNA) and short-hairpin RNA (shRNA) are synthetic, short ncRNAs capable of reducing EZH2 expression and suppressing cancer progression. LncRNAs mainly regulate EZH2 expression via targeting miRNAs. Furthermore, lncRNAs induce EZH2 by modulating miRNA expression. Circular RNAs (CircRNAs), like lncRNAs, affect EZH2 expression via targeting miRNAs. These areas are discussed in the present review with a focus on molecular pathways leading to clinical translation.

EZH2 Mediates Proliferation, Migration, and Invasion Promoted by Estradiol in Human Glioblastoma Cells

Glioblastomas (GBM) are the most frequent and aggressive brain tumors. 17β-estradiol (E2) increases proliferation, migration, and invasion of human GBM cells; however underlying mechanisms are no fully understood. Zeste 2 Enhancer Homologous enzyme (EZH2) is a methyltransferase part of Polycomb 2 repressor complex (PRC2). In GBM, EZH2 is overexpressed and involved in the cell cycle, migration, and invasion processes. We studied the role of EZH2 in the pro-oncogenic actions of E2 in human GBM cells. EZH2 gene silencing and pharmacological inhibition of EZH2 blocked proliferation, migration, and invasion of GBM cells induced by E2. We identified in silico additional putative estrogen response elements (EREs) at the EZH2 promoter, but E2 did not modify EZH2 expression. In silico analysis also revealed that among human GBM samples, EZH2 expression was homogeneous; in contrast, the heterogeneous expression of estrogen receptors (ERs) allowed the classification of the samples into groups. Even in the GBM cluster with high expression of ERs and those of their target genes, the expression of PCR2 target genes did not change. Overall, our data suggest that in GBM cells, pro-oncogenic actions of E2 are mediated by EZH2, without changes in EZH2 expression and by mechanisms that appear to be unrelated to the transcriptional activity of ERs.

EZH2 as a new therapeutic target in brain tumors: Molecular landscape, therapeutic targeting and future prospects

Brain tumors are responsible for high mortality and morbidity worldwide. The brain tumor treatment depends on identification of molecular pathways involved in progression and malignancy. Enhancer of zeste homolog 2 (EZH2) has obtained much attention in recent years in field of cancer therapy due to its aberrant expression and capacity in modulating expression of genes by binding to their promoter and affecting methylation status. The present review focuses on EZH2 signaling in brain tumors including glioma, glioblastoma, astrocytoma, ependymomas, medulloblastoma and brain rhabdoid tumors. EZH2 signaling mainly participates in increasing proliferation and invasion of cancer cells. However, in medulloblastoma, EZH2 demonstrates tumor-suppressor activity. Furthermore, EZH2 can regulate response of brain tumors to chemotherapy and radiotherapy. Various molecular pathways can function as upstream mediators of EZH2 in brain tumors including lncRNAs and miRNAs. Owing to its enzymatic activity, EZH2 can bind to promoter of target genes to induce methylation and affects their expression. EZH2 can be considered as an independent prognostic factor in brain tumors that its upregulation provides undesirable prognosis. Both anti-tumor agents and gene therapies such as siRNA have been developed for targeting EZH2 in cancer therapy.

Advances in Chemokine Signaling Pathways as Therapeutic Targets in Glioblastoma

With a median patient survival of 15 months, glioblastoma (GBM) is still one of the deadliest malign tumors. Despite immense efforts, therapeutic regimens fail to prolong GBM patient overall survival due to various resistance mechanisms. Chemokine signaling as part of the tumor microenvironment plays a key role in gliomagenesis, proliferation, neovascularization, metastasis and tumor progression. In this review, we aimed to investigate novel therapeutic approaches targeting various chemokine axes, including CXCR2/CXCL2/IL-8, CXCR3/CXCL4/CXCL9/CXCL10, CXCR4/CXCR7/CXCL12, CXCR6/CXCL16, CCR2/CCL2, CCR5/CCL5 and CX3CR1/CX3CL1 in preclinical and clinical studies of GBM. We reviewed targeted therapies as single therapies, in combination with the standard of care, with antiangiogenic treatment as well as immunotherapy. We found that there are many antagonist-, antibody-, cell- and vaccine-based therapeutic approaches in preclinical and clinical studies. Furthermore, targeted therapies exerted their highest efficacy in combination with other established therapeutic applications. The novel chemokine-targeting therapies have mainly been examined in preclinical models. However, clinical applications are auspicious. Thus, it is crucial to broadly investigate the recently developed preclinical approaches. Promising preclinical applications should then be investigated in clinical studies to create new therapeutic regimens and to overcome therapy resistance to GBM treatment.

Long noncoding RNA DLGAP1-AS1 promotes the progression of glioma by regulating the miR-1297/EZH2 axis

Dysregulated lncRNAs have been implicated in a plethora of tumors, including glioma. One such oncogenic lncRNAs that has been reported in several cancers is the lncRNA DLGAP1 antisense RNA 1 (DLGAP1-AS1). This study seeks to characterize the expression of DLGAP1-AS1 in glioma tissues, which we found to be raised in both glioma samples and cell lines. Functional experiments revealed that DLGAP1-AS1 promoted in vitro glioma cell invasion, migration and proliferation. DLGAP1-AS1 was found to function as a miR-1297 sponge, based on information from luciferase reporter assays, RNA pull-down assays and publicly available online databases. miR-1297 was in turn found to functionally target EZH2. DLGAP1-AS1 modulated EZH2 expressions through miR-1297 sponging. Glioma progression appears to be supported DLGAP1-AS1 -promoted activation of the miR-1297/EZH2 axis. The components of this axis may function as therapeutic targets for glioma.