c -MYC amplification and expression in astrocytic tumors

Role of Non-coding RNAs in the Response of Glioblastoma to Temozolomide

Chemotherapy and radiotherapy are widely used in clinical practice across the globe as cancer treatments. Intrinsic or acquired chemoresistance poses a significant problem for medical practitioners and researchers, causing tumor recurrence and metastasis. The most dangerous kind of malignant brain tumor is called glioblastoma multiforme (GBM) that often recurs following surgery. The most often used medication for treating GBM is temozolomide chemotherapy; however, most patients eventually become resistant. Researchers are studying preclinical models that accurately reflect human disease and can be used to speed up drug development to overcome chemoresistance in GBM. Non-coding RNAs (ncRNAs) have been shown to be substantial in regulating tumor development and facilitating treatment resistance in several cancers, such as GBM. In this work, we mentioned the mechanisms of how different ncRNAs (microRNAs, long non-coding RNAs, circular RNAs) can regulate temozolomide chemosensitivity in GBM. We also address the role of these ncRNAs encapsulated inside secreted exosomes.

Metabolic Roles of HIF1, c-Myc, and p53 in Glioma Cells

The metabolic reprogramming that promotes tumorigenesis in glioblastoma is induced by dynamic alterations in the hypoxic tumor microenvironment, as well as in transcriptional and signaling networks, which result in changes in global genetic expression. The signaling pathways PI3K/AKT/mTOR and RAS/RAF/MEK/ERK stimulate cell metabolism, either directly or indirectly, by modulating the transcriptional factors p53, HIF1, and c-Myc. The overexpression of HIF1 and c-Myc, master regulators of cellular metabolism, is a key contributor to the synthesis of bioenergetic molecules that mediate glioma cell transformation, proliferation, survival, migration, and invasion by modifying the transcription levels of key gene groups involved in metabolism. Meanwhile, the tumor-suppressing protein p53, which negatively regulates HIF1 and c-Myc, is often lost in glioblastoma. Alterations in this triad of transcriptional factors induce a metabolic shift in glioma cells that allows them to adapt and survive changes such as mutations, hypoxia, acidosis, the presence of reactive oxygen species, and nutrient deprivation, by modulating the activity and expression of signaling molecules, enzymes, metabolites, transporters, and regulators involved in glycolysis and glutamine metabolism, the pentose phosphate cycle, the tricarboxylic acid cycle, and oxidative phosphorylation, as well as the synthesis and degradation of fatty acids and nucleic acids. This review summarizes our current knowledge on the role of HIF1, c-Myc, and p53 in the genic regulatory network for metabolism in glioma cells, as well as potential therapeutic inhibitors of these factors.

Liquid biopsy: creating opportunities in brain space

In recent years, liquid biopsy has emerged as an alternative method to diagnose and monitor tumors. Compared to classical tissue biopsy procedures, liquid biopsy facilitates the repetitive collection of diverse cellular and acellular analytes from various biofluids in a non/minimally invasive manner. This strategy is of greater significance for high-grade brain malignancies such as glioblastoma as the quantity and accessibility of tumors are limited, and there are collateral risks of compromised life quality coupled with surgical interventions. Currently, blood and cerebrospinal fluid (CSF) are the most common biofluids used to collect circulating cells and biomolecules of tumor origin. These liquid biopsy analytes have created opportunities for real-time investigations of distinct genetic, epigenetic, transcriptomics, proteomics, and metabolomics alterations associated with brain tumors. This review describes different classes of liquid biopsy biomarkers present in the biofluids of brain tumor patients. Moreover, an overview of the liquid biopsy applications, challenges, recent technological advances, and clinical trials in the brain have also been provided.

IDP-410: a Novel Therapeutic Peptide that Alters N-MYC Stability and Reduces Angiogenesis and Tumor Progression in Glioblastomas

Glioblastomas (GBMs) are the most frequent and highly aggressive brain tumors, being resistant to all cytotoxic and molecularly targeted agents tested so far. There is, therefore, an urgent need to find novel therapeutic approaches and/or alternative targets to bring treatment options to patients. Here, we first show that GBMs express high levels of N-MYC protein, a transcription factor involved in normal brain development. A novel stapled peptide designed to specifically target N-MYC protein monomer, IDP-410, is able to impair the formation of N-MYC/MAX complex and reduce the stability of N-MYC itself. As a result, the viability of GBM cells is compromised. Moreover, the efficacy is found dependent on the levels of expression of N-MYC. Finally, we demonstrate that IDP-410 reduces GBM growth in vivo when administered systemically, both in subcutaneous and intracranial xenografts, reducing the vascularization of the tumors, highlighting a potential relationship between the function of N-MYC and the expression of mesenchymal/angiogenic genes. Overall, our results strengthen the view of N-MYC as a therapeutic target in GBM and strongly suggest that IDP-410 could be further developed to become a first-in-class inhibitor of N-MYC protein, affecting not only tumor cell proliferation and survival, but also the interplay between GBM cells and their microenvironment.

Transcription factors in glioblastoma - Molecular pathogenesis and clinical implications

Glioblastoma, also known as glioblastoma multiforme (GBM), is one of the most lethal human cancers, however, the molecular mechanisms driving GBM remain largely elusive. Recent studies have revealed that transcription factors are significantly involved in GBM biology. Transcription factors (TFs), which are proteins that bind DNA to regulate gene expression, have critical roles at focal points in signaling pathways, orchestrating many cellular processes, such as cell growth and proliferation, differentiation, apoptosis, immune responses, and metabolism. Dysregulated or mutated TFs are common in GBM, resulting in aberrant gene expression that promotes tumor initiation, progression, and resistance to conventional therapies. In the present Review, we focus on TFs that are implicated in GBM pathogenesis, highlighting their oncogenic or tumor suppressive functions and describing the molecular mechanisms underlying their effect on GBM cells. We also discuss their use as biomarkers for GBM prognosis and therapeutic response, as well as their targeting with drugs for GBM treatment. Deciphering the role of TFs in the biology of GBM will provide new insights into the pathological mechanisms and reveal novel biomarkers and therapeutic targets.

Circ_0058106 promotes proliferation, metastasis and EMT process by regulating Wnt2b/β-catenin/c-Myc pathway through miR-185-3p in hypopharyngeal squamous cell carcinoma

Hypopharyngeal squamous cell carcinoma (HSCC) accounts 95% of hypopharyngeal cancer, which is characterized by high early metastasis rate and poor prognosis. It is reported that circular RNA is involved in the occurrence and development of cancer; however, the role of circRNA in hypopharyngeal cancer has little been investigated. We performed hypopharyngeal carcinoma circRNA microarray and qRT-PCR verification. The results showed circ_0058106 expression level was significantly upregulated in tumor tissues than in corresponding normal tissues. We found that circ_0058106 upregulation promoted proliferation, migration and invasion of HSCC cells, while knockdown of circ_0058106 inhibited proliferation, migration and invasion of HSCC cells both in vitro and in vivo. Bioinformatics predicted circ_0058106 may interact with miR-185-3p. We verified circ_0058106 directly bound miR-185-3p and downregulated miR-185-3p expression by using dual-luciferase reporter assay and qRT-PCR. Moreover, we proved circ_0058106 promoted HSCC cells tumorigenesis and EMT process by regulating Wnt2b/β-catenin/c-Myc pathway via miR-185-3p. In conclusion, our findings firstly confirmed the carcinogenic effect of circ_0058106 in promoting HSCC cells tumorigenesis, metastasis, invasion and EMT process by regulating Wnt2b/β-catenin/c-Myc pathway through sponging miR-185-3p, indicating that circ_0058106 may be a new therapeutic target and prognostic marker for HSCC.

Targeting MYCN in Molecularly Defined Malignant Brain Tumors

Misregulation of MYC genes, causing MYC overexpression or protein stabilization, is frequently found in malignant brain tumors highlighting their important roles as oncogenes. Brain tumors in children are the most lethal of all pediatric malignancies and the most common malignant primary adult brain tumor, glioblastoma, is still practically incurable. MYCN is one of three MYC family members and is crucial for normal brain development. It is associated with poor prognosis in many malignant pediatric brain tumor types and is focally amplified in specific adult brain tumors. Targeting MYCN has proved to be challenging due to its undruggable nature as a transcription factor and for its importance in regulating developmental programs also in healthy cells. In this review, we will discuss efforts made to circumvent the difficulty of targeting MYCN specifically by using direct or indirect measures to treat MYCN-driven brain tumors. We will further consider the mechanism of action of these measures and suggest which molecularly defined brain tumor patients that might benefit from MYCN-directed precision therapies.

Histone demethylase KDM4C controls tumorigenesis of glioblastoma by epigenetically regulating p53 and c-Myc

Glioblastoma is the most lethal brain tumor and its pathogenesis remains incompletely understood. KDM4C is a histone H3K9 demethylase that contributes to epigenetic regulation of both oncogene and tumor suppressor genes and is often overexpressed in human tumors, including glioblastoma. However, KDM4C’s roles in glioblastoma and the underlying molecular mechanisms remain unclear. Here, we show that KDM4C knockdown significantly represses proliferation and tumorigenesis of glioblastoma cells in vitro and in vivo that are rescued by overexpressing wild-type KDM4C but not a catalytic dead mutant. KDM4C protein expression is upregulated in glioblastoma, and its expression correlates with c-Myc expression. KDM4C also binds to the c-Myc promoter and induces c-Myc expression. Importantly, KDM4C suppresses the pro-apoptotic functions of p53 by demethylating p53K372me1, which is pivotal for the stability of chromatin-bound p53. Conversely, depletion or inhibition of KDM4C promotes p53 target gene expression and induces apoptosis in glioblastoma. KDM4C may serve as an oncogene through the dual functions of inactivation of p53 and activation of c-Myc in glioblastoma. Our study demonstrates KDM4C inhibition as a promising therapeutic strategy for targeting glioblastoma.

Hypoxic Glioma Stem Cell-Derived Exosomes Containing Linc01060 Promote Progression of Glioma by Regulating the MZF1/c-Myc/HIF1α Axis

Glioma stem cells (GSC) are a subpopulation of tumor cells with special abilities to proliferate and differentiate in gliomas. They are one of the main causes of tumor recurrence, especially under hypoxic conditions. Although long noncoding RNAs (lncRNA) are known to be involved in numerous biological processes and are implied in the occurrence of certain diseases, their role in tumor development and progression remains poorly understood. Here we explored the mechanisms by which lncRNA derived from hypoxic GSCs (H-GSC) cause glioma progression. Isolation and identification of the Linc01060 gene, the exosomes containing them, and the proteins from tumor cells regulating the gene allowed for studying the effects of Linc01060 on proliferation and glycometabolism. H-GSC exerted their effects by transferring exosomes to glioma cells, resulting in a significant increase in Linc01060 levels. Mechanistically, Linc01060 directly interacted with the transcription factor myeloid zinc finger 1 (MZF1) and enhanced its stability. Linc01060 facilitated nuclear translocation of MZF1 and promoted MZF1-mediated c-Myc transcriptional activities. In addition, c-Myc enhanced the accumulation of the hypoxia-inducible factor-1 alpha (HIF1α) at the posttranscriptional level. HIF1α bound the hormone response elements of the Linc01060 promoter, upregulating the transcription of Linc01060 gene. Clinically, Linc01060 was upregulated in glioma and was significantly correlated with tumor grade and poor clinical prognosis. Overall, these data show that secretion of Linc01060-containing exosomes from H-GSCs activates prooncogenic signaling pathways in glioma cells to promote disease progression. SIGNIFICANCE: These findings suggest that inhibition of Linc01060-containing exosomes or targeting the Linc01060/MZF1/c-Myc/HIF1α axis may be an effective therapeutic strategy in glioma.

LINC00470 promotes tumour proliferation and invasion, and attenuates chemosensitivity through the LINC00470/miR-134/Myc/ABCC1 axis in glioma

Glioma is the most common primary malignant tumour in the brain; temozolomide (TMZ) is the most prevalent chemotherapeutic drug currently used to combat this cancer. We reported previously that the long intergenic non‐protein coding RNA 470 (LINC00470) is a novel prognostic biomarker for glioma and promotes the tumour growth in an intracranial transplantation mouse model. However, the effects of LINC00470 on glioma cell proliferation, invasion and TMZ chemosensitivity, as well as its molecular mechanism, remain unclear. In this study, we found elevated expression levels of LINC00470 and MYC in glioma tissues and cells and decreased expression of microRNA‐134 (miR‐134). Functional studies have shown that LINC00470 promotes proliferation and invasion, and attenuates chemosensitivity of glioma cells, while miR‐134 exerts the opposite effect. In the rescue experiments, the tumorigenic effect of LINC00470 was offset by miR‐134. In the mechanism study, we found that LINC00470 was a competitive endogenous RNA (ceRNA) of miR‐134 and that miR‐134 can directly target MYC and negatively regulate its expression. Furthermore, MYC was positively correlated with ATP‐binding cassette subfamily C member 1 (ABCC1) expression in glioma cells and MYC up‐regulated ABCC1 expression. Further studies found that LINC00470 regulated MYC by sponging miR‐134 to regulate the expression of ABCC1. We concluded that LINC00470 promoted the expression of MYC and ABCC1 by suppressing miR‐134, thus promoting glioma cell proliferation and invasion, and attenuating TMZ chemosensitivity. Moreover, the LINC00470/miR‐134/MYC/ABCC1 axis constitutes a potential therapeutic target.

Impact of 9p deletion and p16, Cyclin D1, and Myc hyperexpression on the outcome of anaplastic oligodendrogliomas

Objective

To study the presence of 9p deletion and p16, cyclin D1 and Myc expression and their respective diagnostic and prognostic interest in oligodendrogliomas.

Methods

We analyzed a retrospective series of 40 consecutive anaplastic oligodendrogliomas (OIII) from a single institution and compared them to a control series of 10 low grade oligodendrogliomas (OII). Automated FISH analysis of chromosome 9p status and immunohistochemistry for p16, cyclin D1 and Myc was performed for all cases and correlated with clinical and histological data, event free survival (EFS) and overall survival (OS).

Results

Chromosome 9p deletion was observed in 55% of OIII (22/40) but not in OII. Deletion was highly correlated to EFS (median = 29 versus 53 months, p<0.0001) and OS (median = 48 versus 83 months, p<0.0001) in both the total cohort and the OIII population. In 9p non-deleted oligodendrogliomas, p16 hyperexpression correlated with a shorter OS (p = 0.02 in OII and p = 0.0001 in OIII) whereas lack of p16 expression was correlated to a shorter EFS and OS in 9p deleted OIII (p = 0.001 and p = 0.0002 respectively). Expression of Cyclin D1 was significantly higher in OIII (median expression 45% versus 14% for OII, p = 0.0006) and was correlated with MIB-1 expression (p<0.0001), vascular proliferation (p = 0.002), tumor necrosis (p = 0.04) and a shorter EFS in the total cohort (p = 0.05). Hyperexpression of Myc was correlated to grade (median expression 27% in OII versus 35% in OIII, p = 0.03), and to a shorter EFS in 9p non-deleted OIII (p = 0.01).

Conclusion

Chromosome 9p deletion identifies a subset of OIII with significantly worse prognosis. The combination of 9p status and p16 expression level identifies two distinct OIII populations with divergent prognosis. Hyperexpression of Bcl1 and Myc appears highly linked to anaplasia but the prognostic value is unclear and should be investigated further.

Remote intracranial recurrence of IDH mutant gliomas is associated with TP53 mutations and an 8q gain

Most IDH mutant gliomas harbor either 1p/19q co-deletions or TP53 mutation; 1p/19q co-deleted tumors have significantly better prognoses than tumors harboring TP53 mutations. To investigate the clinical factors that contribute to differences in tumor progression of IDH mutant gliomas, we classified recurrent tumor patterns based on MRI and correlated these patterns with their genomic characterization. Accordingly, in IDH mutant gliomas (N = 66), 1p/19 co-deleted gliomas only recurred locally, whereas TP53 mutant gliomas recurred both locally and in remote intracranial regions. In addition, diffuse tensor imaging suggested that remote intracranial recurrence in the astrocytomas, IDH-mutant with TP53 mutations may occur along major fiber bundles. Remotely recurrent tumors resulted in a higher mortality and significantly harbored an 8q gain; astrocytomas with an 8q gain resulted in significantly shorter overall survival than those without an 8q gain. OncoScan^® arrays and next-generation sequencing revealed specific 8q regions (i.e., between 8q22 and 8q24) show a high copy number. In conclusion, only tumors with TP53 mutations showed patterns of remote recurrence in IDH mutant gliomas. Furthermore, an 8q gain was significantly associated with remote intracranial recurrence and can be considered a poor prognostic factor in astrocytomas, IDH-mutant.

KCTD2, an adaptor of Cullin3 E3 ubiquitin ligase, suppresses gliomagenesis by destabilizing c-Myc

Cullin3 E3 ubiquitin ligase ubiquitinates a wide range of substrates through substrate-specific adaptors Bric-a-brac, Tramtrack, and Broad complex (BTB) domain proteins. These E3 ubiquitin ligase complexes are involved in diverse cellular functions. Our recent study demonstrated that decreased Cullin3 expression induces glioma initiation and correlates with poor prognosis of patients with malignant glioma. However, the substrate recognition mechanism associated with tumorigenesis is not completely understood. Through yeast two-hybrid screening, we identified potassium channel tetramerization domain-containing 2 (KCTD2) as a BTB domain protein that binds to Cullin3. The interaction of Cullin3 and KCTD2 was verified using immunoprecipitation and immunofluorescence. Of interest, KCTD2 expression was markedly decreased in patient-derived glioma stem cells (GSCs) compared with non-stem glioma cells. Depletion of KCTD2 using a KCTD2-specific short-hairpin RNA in U87MG glioma cells and primary Ink4a/Arf-deficient murine astrocytes markedly increased self-renewal activity in addition with an increased expression of stem cell markers, and mouse in vivo intracranial tumor growth. As an underlying mechanism for these KCTD2-mediated phenotypic changes, we demonstrated that KCTD2 interacts with c-Myc, which is a key stem cell factor, and causes c-Myc protein degradation by ubiquitination. As a result, KCTD2 depletion acquires GSC features and affects aerobic glycolysis via expression changes in glycolysis-associated genes through c-Myc protein regulation. Of clinical significance was our finding that patients having a profile of KCTD2 mRNA-low and c-Myc gene signature-high, but not KCTD2 mRNA-low and c-Myc mRNA-high, are strongly associated with poor prognosis. This study describes a novel regulatory mode of c-Myc protein in malignant gliomas and provides a potential framework for glioma therapy by targeting c-Myc function.

Failure of the PTEN/aPKC/Lgl Axis Primes Formation of Adult Brain Tumours in Drosophila

Different regions in the mammalian adult brain contain immature precursors, reinforcing the concept that brain cancers, such as glioblastoma multiforme (GBM), may originate from cells endowed with stem-like properties. Alterations of the tumour suppressor gene PTEN are very common in primary GBMs. Very recently, PTEN loss was shown to undermine a specific molecular axis, whose failure is associated with the maintenance of the GBM stem cells in mammals. This axis is composed of PTEN, aPKC, and the polarity determinant Lethal giant larvae (Lgl): PTEN loss promotes aPKC activation through the PI3K pathway, which in turn leads to Lgl inhibition, ultimately preventing stem cell differentiation. To find the neural precursors responding to perturbations of this molecular axis, we targeted different neurogenic regions of the Drosophila brain. Here we show that PTEN mutation impacts aPKC and Lgl protein levels also in Drosophila. Moreover, we demonstrate that PI3K activation is not sufficient to trigger tumourigenesis, while aPKC promotes hyperplastic growth of the neuroepithelium and a noticeable expansion of the type II neuroblasts. Finally, we show that these neuroblasts form invasive tumours that persist and keep growing in the adult, leading the affected animals to untimely death, thus displaying frankly malignant behaviours.

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.

Calcium signaling orchestrates glioblastoma development: Facts and conjunctures

While it is a relatively rare disease, glioblastoma multiform (GBM) is one of the more deadly adult cancers. Following current interventions, the tumor is never eliminated whatever the treatment performed; whether it is radiotherapy, chemotherapy, or surgery. One hypothesis to explain this poor outcome is the "cancer stem cell" hypothesis. This concept proposes that a minority of cells within the tumor mass share many of the properties of adult neural stem cells and it is these that are responsible for the growth of the tumor and its resistance to existing therapies. Accumulating evidence suggests that Ca(2+) might also be an important positive regulator of tumorigenesis in GBM, in processes involving quiescence, maintenance, proliferation, or migration. Glioblastoma tumors are generally thought to develop by co-opting pathways that are involved in the formation of an organ. We propose that the cells initiating the tumor, and subsequently the cells of the tumor mass, must hijack the different checkpoints that evolution has selected in order to prevent the pathological development of an organ. In this article, two main points are discussed. (i) The first is the establishment of a so-called "cellular society," which is required to create a favorable microenvironment. (ii) The second is that GBM can be considered to be an organism, which fights to survive and develop. Since GBM evolves in a limited space, its only chance of development is to overcome the evolutionary checkpoints. For example, the deregulation of the normal Ca(2+) signaling elements contributes to the progression of the disease. Thus, by manipulating the Ca(2+) signaling, the GBM cells might not be killed, but might be reprogrammed toward a new fate that is either easy to cure or that has no aberrant functioning. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

The role of Myc and let-7a in glioblastoma, glucose metabolism and response to therapy

Glioblastoma multiforme (GBM) is thought to result from an imbalance between glucose metabolism and tumor growth. The Myc oncogene and lethal-7a microRNA (let-7a miRNA) have been suggested to cooperatively regulate multiple downstream targets leading to changes in chromosome stability, gene mutations, and/or modulation of tumor growth. Here, we review the roles of Myc and let-7a in glucose metabolism and tumor growth and addresses their future potential as prognostic markers and therapeutic tools in GBM. We focus on the functions of Myc and let-7a in glucose uptake, tumor survival, proliferation, and mobility of glioma cells. In addition, we discuss how regulation of different pathways by Myc or let-7a may be useful for future GBM therapies. A large body of evidence suggests that targeting Myc and let-7a may provide a selective mechanism for the deregulation of glucose metabolic pathways in glioma cells. Indeed, Myc and let-7a are aberrantly expressed in GBM and have been linked to the regulation of cell growth and glucose metabolism in GBM. This article is part of a Special Issue entitled "Targeting alternative glucose metabolism and regulate pathways in GBM cells for future glioblastoma therapies".

MYC and MXI1 protein expression: potential prognostic significance in women with breast cancer in China

OBJECTIVE

To investigate the expression levels and the clinical significance of MYC and MXI1 proteins in breast cancer.

METHODS

The expression levels of MYC and MXI1 were detected by immunohistochemical assay in 166 cases of breast cancer; the relationships among MYC, MXI1 and the clinicopathological parameters were analyzed by χ2 test. Univariate analysis and Cox's proportional hazards model were used to evaluate the prognostic significance of the 2 proteins.

RESULTS

27.71% of the tumor specimens showed high staining intensity for MYC (high-expression group, HEG-MYC) and 22.89% showed high staining intensity for MXI1 (HEG-MXI1); the expression of 2 proteins was negatively correlated (r = -0.177 p = 0.022). The Kaplan-Meier method for survival analysis showed that patients of the MYC-HEG demonstrated a significantly worse disease-specific survival than those of the MYC-low-expression group (LEG) (χ2 = 11.102, p = 0.001). However, patients of the MXI1-HEG had a significantly better disease-specific survival than those of the MXI1-LEG (χ2 = 7.858, p = 0.005). Both univariate analysis and Cox's proportional hazards model indicated that MYC and MXI1 could be independent prognostic molecular markers.

CONCLUSION

MYC-HEG and MXI1-LEG levels are associated with poor prognosis in patients with breast cancer, suggesting that they may be useful molecular markers in breast cancer prognosis prediction.

cMYC expression in infiltrating gliomas: associations with IDH1 mutations, clinicopathologic features and outcome

Gliomas are among the most frequent adult primary brain tumors. Mutations in IDH1, a metabolic enzyme, strongly correlate with secondary glioblastomas and increased survival. cMYC is an oncogene also implicated in aberrant metabolism, but its prognostic impact remains unclear. Recent genotyping studies also showed SNP variants near the cMYC gene locus, associate with an increased risk for development of IDH1/2 mutant gliomas suggesting a possible interaction between cMYC and IDH1. We evaluated nuclear cMYC protein levels and IDH1 (R132H) by immunohistochemistry in patients with oligodendroglioma/oligoastrocytomas (n = 20), astrocytomas (grade II) (n = 19), anaplastic astrocytomas (n = 21) or glioblastomas (n = 111). Of 158 tumors with sufficient tissue, 110 (70 %) showed nuclear cMYC immunopositivity--most frequent (95 %, χ(2) p = 0.0248) and intense (mean 1.33, ANOVA p = 0.0179) in anaplastic astrocytomas versus glioblastomas (63 %) or low grade gliomas (74 %). cMYC expression associated with younger age as well as p53 immunopositivity (OR = 3.6, p = 0.0332) and mutant IDH1 (R132H) (OR = 7.4, p = 0.06) among malignant gliomas in our cohort. Independent analysis of the publically available TCGA glioblastoma dataset confirmed our strong association between cMYC and mutant IDH1 expression. Both IDH1 (R132H) and cMYC protein expression were associated with improved overall survival by univariate analysis. However, cMYC co-expression associated with shortened time to malignant transformation and overall survival among IDH1 (R132H) mutants in both univariate and multivariate analyses. In summary, our findings suggest that cMYC may be associated with a unique clinicopathologic and biologic group of infiltrating gliomas and help mediate the malignant transformation of IDH1 mutant gliomas.

Inhibition of BET bromodomain targets genetically diverse glioblastoma

PURPOSE

Glioblastoma is refractory to conventional therapies. The bromodomain and extraterminal domain (BET) proteins are epigenetic readers that selectively bind to acetylated lysine residues on histone tails. These proteins recently emerged as important therapeutic targets in NUT midline carcinoma and several types of hematopoietic cancers. In this study, the therapeutic potential of a novel BET bromodomain inhibitor, JQ1, was assessed in a panel of genetically heterogeneous glioblastoma samples.

EXPERIMENTAL DESIGN

The antineoplastic effects of JQ1 were shown using ex vivo cultures derived from primary glioblastoma xenograft lines and surgical specimens of different genetic background. The in vivo efficacy was assessed in orthotopic glioblastoma tumors.

RESULTS

We showed that JQ1 induced marked G1 cell-cycle arrest and apoptosis, which was phenocopied by knockdown of individual BET family members. JQ1 treatment resulted in significant changes in expression of genes that play important roles in glioblastoma such as c-Myc, p21(CIP1/WAF1), hTERT, Bcl-2, and Bcl-xL. Unlike the observations in some hematopoietic cancer cell lines, exogenous c-Myc did not significantly protect glioblastoma cells against JQ1. In contrast, ectopically expressed Bcl-xL partially rescued cells from JQ1-induced apoptosis, and knockdown of p21(CIP1/WAF1) attenuated JQ1-induced cell-cycle arrest. Cells genetically engineered for Akt hyperactivation or p53/Rb inactivation did not compromise JQ1 efficacy, suggesting that these frequently mutated signaling pathways may not confer resistance to JQ1. Furthermore, JQ1 significantly repressed growth of orthotopic glioblastoma tumors.

CONCLUSION

Our results suggest potentially broad therapeutic use of BET bromodomain inhibitors for treating genetically diverse glioblastoma tumors.

Myc proteins in brain tumor development and maintenance

Myc proteins are often deregulated in human brain tumors, especially in embryonal tumors that affect children. Many observations have shown how alterations of these pleiotropic Myc transcription factors provide initiation, maintenance, or progression of tumors. This review will focus on the role of Myc family members (particularly c-myc and Mycn) in tumors like medulloblastoma and glioma and will further discuss how to target stabilization of these proteins for future brain tumor therapies.

Effects of RNAi-mediated gene silencing of LRIG1 on proliferation and invasion of glioma cells

The effects of RNAi-mediated gene silencing of LRlG1 on proliferation and invasion of the human glioma cell line U251-MG and the possible mechanisms were explored in this study. The plasmids pGenesil2-LRIG1-shRNA1 and pGenesil2-LRIG1-shRNA2 were transfected into U251-MG glioma cells respectively by using Lipofectamine 2000 and the transfected cells in which the LRIG1 expression was stably suppressed were selected by G418. The cells transfected with negative shRNA served as control. The expression levels of LRIG1 mRNA and protein were measured by qRT-PCR and Western blotting, respectively. The cell cycle was analyzed by flow cytometry. The results showed that LRIG1 mRNA expression was reduced by 70% and 58% and LRIG1 protein expression by 58% and 26% in U251-MG cells transfected with pGenesil2-LRIG1-shRNAl and pGenesil2-LRIG1-shRNA2 relative to the negative shRNA-transfected U251-MG cells. The proliferative capacity of the LRIG1 specific siRNA-transfected cells was stronger than that of control cells. Cell cycle analysis showed that silencing LRIG1 significantly increased the percentage of S phase cells and the proliferation index (P<0.01). Moreover, silencing LRIG1 could promote the invasion of U251-MG cells (P<0.05). These findings suggested that LRIG1-targeting siRNA can exert a dramatically inhibitory effect on RNA transcription and protein expression of LRIG1, and LRIG1 down-regulation could promote the proliferation of U251-MG cells, arrest U251-MG cells in S phase, and enhance the invasion of U251-MG cells.