Classification histologique et moléculaire des gliomes

Downregulation of miR-137 and miR-6500-3p promotes cell proliferation in pediatric high-grade gliomas

Pediatric high-grade gliomas (pHGGs) are aggressive brain tumors affecting children, and outcomes have remained dismal, even with access to new multimodal therapies. In this study, we compared the miRNomes and transcriptomes of pediatric low- (pLGGs) and high-grade gliomas (pHGGs) using small RNA sequencing (smRNA-Seq) and gene expression microarray, respectively. Through integrated bioinformatics analyses and experimental validation, we identified miR-137 and miR-6500-3p as significantly downregulated in pHGGs. miR-137 or miR-6500-3p overexpression reduced cell proliferation in two pHGG cell lines, SF188 and UW479. CENPE, KIF14 and NCAPG levels were significantly higher in pHGGs than pLGGs, and were direct targets of miR-137 or miR-6500-3p. Furthermore, knockdown of CENPE, KIF14 or NCAPG combined with temozolomide treatment resulted in a combined suppressive effect on pHGG cell proliferation. In summary, our results identify novel mRNA/miRNA interactions that contribute to pediatric glioma malignancy and represent potential targets for the development of new therapeutic strategies.

LncRNA profile study reveals four-lncRNA signature associated with the prognosis of patients with anaplastic gliomas

Anaplastic glioma is Grade III and the median overall survival is about 37.6 months. However, there are still other factors that affect the prognosis for anaplastic glioma patients due to variable overall survival. So we screened four-lncRNA signature (AGAP2-AS1, TPT1-AS1, LINC01198 and MIR155HG) from the lncRNA expression profile from the GSE16011, CGGA and REMBRANDT datasets. The patients in low risk group had longer overall survival than high risk group (median OS 2208.25 vs. 591.30 days; P < 0.0001). Moreover, patients in the low risk group showed similar overall survival to Grade II patients (P = 0.1669), while the high risk group showed significant different to Grade IV (P = 0.0005) with similar trend. So based on the four-lncRNA, the anaplastic gliomas could be divided into grade II-like and grade IV-like groups. On the multivariate analysis, it showed the signature was an independent prognostic factor (P = 0.000). The expression of four lncRNAs in different grades showed that AGAP2-AS1, LINC01198 and MIR155HG were increased with tumor grade, while TPT1-AS1 was decreased. Knockdown of AGAP2-AS1 can inhibit the cell proliferation, migration and invasion, while increase the apoptosis cell rates in vitro. In conclusion, our results showed that the four-lncRNA signature has prognostic value for anaplastic glioma. Moreover, clinicians should conduct corresponding therapies to achieve best treatment with less side effects for two groups patients.

Glioblastoma, hypoxia and autophagy: a survival-prone 'ménage-à-trois'

Glioblastoma multiforme is the most common and the most aggressive primary brain tumor. It is characterized by a high degree of hypoxia and also by a remarkable resistance to therapy because of its adaptation capabilities that include autophagy. This degradation process allows the recycling of cellular components, leading to the formation of metabolic precursors and production of adenosine triphosphate. Hypoxia can induce autophagy through the activation of several autophagy-related proteins such as BNIP3, AMPK, REDD1, PML, and the unfolded protein response-related transcription factors ATF4 and CHOP. This review summarizes the most recent data about induction of autophagy under hypoxic condition and the role of autophagy in glioblastoma.

miR-93 promotes cell proliferation in gliomas through activation of PI3K/Akt signaling pathway

The PI3K/Akt signaling pathway is frequently activated in various human cancer types and plays essential roles in development and progression of cancers. Multiple regulators, such as phosphatase and tensin homolog (PTEN) and PH domain leucine rich repeat protein phosphatases (PHLPP), have also found to be involved in suppression of the PI3K/Akt signaling pathway. However, how suppressive effects mediated by these regulators are concomitantly disrupted in cancers, which display constitutively activated PI3K/Akt signaling, remains puzzling. In the present study, we reported that the expression of miR-93 was markedly upregulated in glioma cell lines and clinical glioma tissues. Statistical analysis revealed that miR-93 levels significantly correlated with clinicopathologic grade and overall survival in gliomas. Furthermore, we found that overexpressing miR-93 promoted, but inhibition of miR-93 reduced, glioma cell proliferation and cell-cycle progression. We demonstrated that miR-93 activated PI3K/Akt signaling through directly suppressing PTEN, PHLPP2 and FOXO3 expression via targeting their 3'UTRs. Therefore, our results suggest that miR-93 might play an important role in glioma progression and uncover a novel mechanism for constitutive PI3K/Akt activation in gliomas.

Overexpression of SCLIP promotes growth and motility in glioblastoma cells

SCLIP, a microtubule-destabilizing phosphoprotein, is known to be involved in the development of the central nervous system (CNS). It has been well established that there are notable parallels between normal development and tumorigenesis, especially in glioma. However, no studies have examined the significance of SCLIP in gliomagenesis. To address this, we investigated the expression of SCLIP and its roles in the development of gliomas. Notably, we found that SCLIP was highly expressed in various grades of glioma samples, as compared with normal brain tissues. Overexpression of SCLIP dramatically stimulated tumor cell migration and invasion as well as proliferation and downregulation of SCLIP showed opposite effects, establishing an important oncogenic role for this gene. Furthermore, we revealed that STAT3 was required to maintain SCLIP stability, suggesting that overexpression of STAT3 may be a critical step to facilitate microtubule dynamics and subsequently promotes migration and invasion of glioma cells. Taken together, our findings demonstrate that SCLIP plays an important role in glioma pathology, and may represent a novel therapeutic strategy against human glioma.

[Elderly patients with glioblastoma: state of the art]

The incidence of glioblastoma increases with age, with a median age, at diagnosis, of 65 years. Indeed, the optimization of standard of care of elderly glioblastoma patients in an aging population in Western countries becomes crucial. The age remains the main prognostic factor of glioblastoma. Survival among elderly patients is significantly less than among younger patients. The median survival of elderly glioblastoma patients is generally inferior to 6 months. More aggressive tumor behavior, less aggressive treatments, increased toxicity of therapies and more unfavorable clinical factors and comorbidities could explain a higher severity of the disease in the elderly. The balance between treatment efficacy and quality of life is a major focus because of the shorter life expectancy of patients. The standard of care of glioblastoma in elderly patients remains controversial. Large optimal resection, when achievable, should be preferred to biopsy. Survival is longer after adjuvant radiotherapy, either normofractionated over 6-weeks course or hypofractionated over 3-weeks course, for patients with good clinical status. Hypofractionation is often preferred because of shorter procedure. Chemotherapy alone with temozolomide can be proposed to patients with methylated MGMT promoter. A phase III randomized study, testing short-course adjuvant radiotherapy with or without temozolomide in elderly patients with good clinical status, is ongoing.

PIVL, a new serine protease inhibitor from Macrovipera lebetina transmediterranea venom, impairs motility of human glioblastoma cells

A novel Kunitz-type serine proteinase inhibitor, termed PIVL, was purified to homogeneity from the venom of the Tunisian snake Macrovipera lebetina transmediterranea. It is a monomeric polypeptide chain cross-linked by three disulfide linkages with an isotope-averaged molecular mass of 7691.7 Da. The 67-residue full-length PIVL sequence was deduced from a venom gland cDNA clone. Structurally, PIVL is built by a single Kunitz/BPTI-like domain. Functionally, it is able to specifically inhibit trypsin activity. Interestingly, PIVL exhibits an anti-tumor effect and displays integrin inhibitory activity without being cytotoxic. Here we show that PIVL is able to dose-dependently inhibit the adhesion, migration and invasion of human glioblastoma U87 cells. Our results also show that PIVL impairs the function of αvβ3 and to a lesser extent, the activity of αvβ6, αvβ5, α1β1 and α5β1 integrins. Interestingly, we demonstrate that the (41)RGN(43) motif of PIVL is likely responsible for its anti-cancer effect. By using time lapse videomicroscopy, we found that PIVL significantly reduced U87 cells motility and affected cell directionality persistence by 68%. These findings reveal novel pharmacological effects for a Kunitz-type serine proteinase inhibitor.

The role of radiotherapy and chemotherapy in the treatment of primary adult high grade gliomas: assessment of patients for these treatment approaches and the common immediate side effects

Gliomas are the commonest primary brain tumours in adults. They are usually classified and graded according to the criteria by the World Health Organisation. High-grade gliomas are the most malignant primary brain tumours. Conventional therapies include surgery, radiotherapy, and chemotherapy. The tumours often demonstrate high levels of resistance to these conventional therapies, and in spite of treatment advances the prognosis remains poor.

Molecular genetics of adult grade II gliomas: towards a comprehensive tumor classification system

Adult grade II low-grade gliomas (LGG) are classified according to the WHO as astrocytomas, oligodendrogliomas or mixed gliomas. TP53 mutations and 1p19q codeletion are the main molecular abnormalities recorded, respectively, in astrocytomas and oligodendrogliomas and in mixed gliomas. Although IDH mutations (IDH1 or IDH2) are recorded in up to 85 % of low-grade gliomas, IDH negative gliomas do occur. We have searched for p53 expression, 1p19q codeletion and IDH status (immunohistochemical detection of the common R132H IDH1 mutation and IDH direct sequencing). Internexin alpha (INA) expression previously recorded to be associated with 1p19q codeletion (1p19q+) gliomas was also analysed. Low-grade gliomas were accurately classified into four groups: group 1, IDH+/p53-/1p19q-; group 2, IDH+/p53-/1p19q+; group 3, IDH+/p53+/1p19q-; and group 4, triple negative gliomas. In contrast to the WHO classification, this molecular classification predicts overall survival on uni- and multivariate analysis (P = 0.001 and P = 0.007, respectively). Group 4 carries the worst prognosis and group 2 the best. Interestingly, p53 +/INA- expression predicts lack of 1p19q codeletion (specificity 100 %, VPP 100 %). The combined use of these three molecular markers allow for an accurate prediction of survival in LGG. These findings could significantly modify LGG classification and may represent a new tool to guide patient-tailored therapy. Moreover, immunohistochemical detection of p53, INA and mR132H IDH1 expression could represent an interesting prescreening test to be performed before 1p19q codeletion, IDH1 minor mutation and IDH2 mutation detection.

IDH mutations in human glioma

A novel mutation of isocitrate dehydrogenase-1 (IDH1) was recently found in a large percentage of secondary human gliomas. Unlike previously discovered prognostic molecular characteristics, IDH1 mutations were found across gliomas of many different grades and histologies. Further studies have illuminated its utility as a prognostic marker in low-grade and high-grade gliomas and its ability to aid the differentiation and diagnosis of various tumors with histologic ambiguity. As a metabolic enzyme, its inhibitory actions and neomorphic activity present a unique avenue in the understanding of these tumors and potentially a novel mechanism through which they may be treated.

Downregulation of GRIM-19 promotes growth and migration of human glioma cells

It has become increasingly clear that there are notable parallels between normal development and tumorigenesis. Glioma is a classic model that links between tumorigenesis and development. We evaluated the expression of GRIM-19, a novel gene essential for normal development, in various grades of gliomas and several human glioma cell lines. We showed that GRIM-19 mRNA and protein expression were markedly lower in gliomas than in control brain tissues and negatively correlated with the malignancy of gliomas. Downregulation of GRIM-19 in glioma cells significantly enhanced cell proliferation and migration, whereas overexpression of GRIM-19 showed the opposite effects. We also showed that the activation of signal transducer and activator of transcription 3 (STAT3) and the expression of many STAT3-dependent genes were regulated by the expression of GRIM-19. In addition, GRIM-19 exerted its role probably through the non-STAT3 signaling pathway. Collectively, our data suggest that most gliomas expressed GRIM-19 at low levels, which may play a major role in tumorigenesis in the brain.

Histomolecular classification of adult diffuse gliomas: the diagnostic value of immunohistochemical markers

Adult gliomas are most often infiltrative. The World Health Organization (WHO) has classed them into three major groups according to the presomptive cell of origin: astrocytoma, oligodendroglioma and mixed oligoastrocytoma. Depending on the presence or absence of a small number of signs of anaplasia (mitosis, nuclear atypia, cell density, microvascular proliferation and necrosis) the WHO distinguishes grade II (LGG), III (anaplastic), and IV (glioblastomas, GBM). Mutation in the isocitrate deshydrogenase I and II (IDH1 and 2) genes distinguishes grade II, III and secondary GBM from primary GBM. Moreover two additional genetic alterations are recorded in grade II and III gliomas: TP53 mutations that characterize astrocytomas and 1p19q codeletion (as the result of t(1;19)(q10;p10) translocation) recorded in oligodendrogliomas. Mixed gliomas, the most non-reproducible category, share with astrocytomas and oligodendrogliomas the same genetic alterations. Interestingly TP53 mutation (p53+) and 1p19q codeletion (1p19q+) are mutually exclusive and involve IDH mutated (IDH+) glial precursor cells. According to IDH, TP53, and 1p19q status, four major subtypes of LGG are recorded: IDH+/p53-/1p19q-, IDH+/p53+/1p19q-, IDH+/p53-/1p19q+ and triple negative, this last subgroup having the worst prognosis. Interestingly, p53 expression and internexin alpha (INA) expression can replace to some extent TP53 mutation and 1p19 codeletion, respectively. Moreover the antibody directed against the IDH1R132H isoform is highly specific. Because this mutation is the most frequent it is sufficient to assess IDH status in more than 80% of grade II and III gliomas. Taken together these three immunohistochemical markers are contribute greatly to the classification of gliomas and should be tested routinely as diagnostic markers. Finally, although GBM are genetically heterogeneous, the vast majority display EGFR amplification, often associated with EGFR expression, which can be helpful for diagnosis in certain cases.

Old proteins - new locations: myoglobin, haemoglobin, neuroglobin and cytoglobin in solid tumours and cancer cells

AIM

The unexpected identification of myoglobin (MB) in breast cancer prompted us to evaluate the clinico-pathological value of MB, haemoglobin (HB) and cytoglobin (CYGB) in human breast carcinoma cases. We further screened for the presence of neuroglobin (NGB) and CYGB in tumours of diverse origin, and assessed the O(2) -response of HB, MB and CYGB mRNAs in cancer cell lines, to better elicit the links between this ectopic globin expression and tumour hypoxia.

METHODS

Breast tumours were analysed by immunohistochemistry for HB, MB and CYGB and correlated with clinico-pathological parameters. Screening for CYGB and NGB mRNA expression in tumour entities was performed by hybridization, quantitative PCR (qPCR) and bioinformatics. Hypoxic or anoxic responses of HB, MB and CYGB mRNAs was analysed by qPCR in human Hep3B, MCF7, HeLa and RCC4 cancer cell lines.

RESULTS

78.8% of breast cancer cases were positive for MB, 77.9% were positive for HB and 55.4% expressed CYGB. The closest correlation with markers of hypoxia was observed for CYGB. Compared to the weakly positive status of MB in healthy breast tissues, invasive tumours either lost or up-regulated MB. Breast carcinomas showed the tendency to silence CYGB. HB was not seen in normal tissues and up-regulated in tumours. Beyond breast malignancies, expression levels of NGB and CYGB mRNAs were extremely low in brain tumours (glioblastoma, astrocytoma). NGB was not observed in non-brain tumours. CYGB mRNA, readily detectable in breast cancer and other tumours, is down-regulated in lung adenocarcinomas. Alpha1 globin (α1 globin) and Mb were co-expressed in MCF7 and HeLa cells; CYGB transcription was anoxia-inducible in Hep3B and RCC4 cells.

CONCLUSIONS

This is the first time that HB and CYGB are reported in breast cancer. Neither NGB nor CYGB are systematically up-regulated in tumours. The down-regulated CYGB expression in breast and lung tumours is in line with a tumour-suppressor role. Each of the screened cancer cells expresses at least one globin (i.e. main globin species: CYGB in Hep3B; α1 globin + MB in MCF7 and HeLa). Thus, globins exist in a wide variety of solid tumours. However, the generally weak expression of the endogenous proteins in the cancer argues against a significant contribution to tumour oxygenation. Future studies should consider that cancer-expressed globins might function in ways not directly linked to the binding and transport of oxygen.

Purification, synthesis and characterization of AaCtx, the first chlorotoxin-like peptide from Androctonus australis scorpion venom

AaCtx is the first chlorotoxin-like peptide isolated from Androctonus australis scorpion venom. Its amino acid sequence shares 70% similarity with chlorotoxin from Leiurus quinquestriatus scorpion venom, from which it differs by twelve amino acids. Due to its very low concentration in venom (0.05%), AaCtx was chemically synthesized. Both native and synthetic AaCtx were active on invasion and migration of human glioma cells. However, their activity was found to be lower than that of chlorotoxin. The molecular model of AaCtx shows that most of amino acids differing between AaCtx and chlorotoxin are localized on the N-terminal loop and the α-helix. Based on known compounds that block chloride channels, we suggest that the absence of negative charged amino acids on AaCtx structure may be responsible for its weak activity on glioma cells migration and invasion. This finding serves as a starting point for structure-function relationship studies leading to design high specific anti-glioma drugs.

Absence of IDH mutation identifies a novel radiologic and molecular subtype of WHO grade II gliomas with dismal prognosis

The phenotypic heterogeneity of low-grade gliomas (LGGs) is still inconsistently explained by known molecular abnormalities in patients treated according to the present standards of care. IDH1 codon 132 and IDH2 codon 172 sequencing was performed in a series of 47 LGGs and correlated with clinical presentation, MR imaging characteristics, genomic profile and outcome. A total of 38 IDH1 mutations at codon 132 and 2 IDH2 mutations at codon 172 were found, including 35 R132H (87.5%), 2 R132C (5.0%), 1 R132S (2.5%) and 2 R172 M (5%). The IDH mutations were significantly associated with 1p19q deleted genotype (P = 0.031) and p53 expression (P = 0.014). The presence (vs. absence) of IDH mutations was associated with a better outcome (5-year survival rate, 93% vs. 51%, respectively, P = 0.000001). After adjustment for age, tumor location and size, radiologic infiltration pattern and extent of surgery, multivariate analysis confirmed that IDH mutations was an independent favorable prognostic factor (hazard ratio = 40.9; 95% CI, 2.89-578.49, P = 0.006). Furthermore, we showed that patients with IDH-nonmutated tumors were significantly older (P = 0.020) and that these tumors involved significantly more frequently the insula (P = 0.004), were larger in size (>6 cm, P = 0.047), displayed an infiltrative pattern on MRI (P = 0.007) and were all p53 negative with no 1p19q deletion (P < 10⁻⁶). The absence of IDH mutations in LGGs identifies a novel entity of LGGs with distinctive location, infiltrative behavior, specific molecular alterations, and dismal outcome. These findings could significantly modify the LGG classification and may represent a new tool to guide patient-tailored therapy.

1p19q LOH patterns and expression of p53 and Olig2 in gliomas: relation with histological types and prognosis

In glial tumors, the loss of heterozygosity of the 1p and 19q chromosomal arms is thought to be a marker of good prognosis in oligodendroglial tumors. However, 1p and 19q loss of heterozygosity may be telomeric, interstitial, centromeric or affect the whole arm of the chromosome and the associations between these different patterns and tumor type, other molecular markers and patient prognosis remain unclear. We analyzed microsatellite markers in a region spanning the chromosome from the telomere to the centromere, to characterize the pattern of 1p and 19q loss of heterozygosity in 39 infiltrative gliomas, including astrocytomas, glioblastomas, oligoastrocytomas and oligodendrogliomas. We then studied the association between loss of heterozygosity and the expression of p53 protein and Olig2, as analyzed using immunohistochemistry, and epidermal growth factor receptor (EGFR) gene amplification, as investigated using fluorescence in situ hybridization (FISH). Finally, we assessed the influence of molecular markers on the overall survival of patients. We identified five different 1p19q loss of heterozygosity patterns among the tumors studied and found that loss of heterozygosity over the whole 1p arm was associated with loss of heterozygosity over the whole 19q arm in 90% of cases. 1p19q whole loss was present in all the classical oligodendrogliomas, whereas other 1p19q loss patterns predominated in oligoastrocytomas. 1p19q whole loss was also significantly associated with Olig2 overexpression, but was never observed in tumors overexpressing p53 protein. We also found that, among patients with contrast-enhancing tumors, those with 1p19q whole loss tended to survive for longer. In combination with classical histological and immunohistochemical data, 1p19q status determination provides pertinent information useful for (1) discriminating between histological types of gliomas and (2) identifying a subgroup of tumors that are associated with a better prognosis.

Expression of integrin alpha6beta1 enhances tumorigenesis in glioma cells

The integrin alpha6beta1 and its main ligand laminin-111 are overexpressed in glioblastoma, as compared with normal brain tissue, suggesting they may be involved in glioblastoma malignancy. To address this question, we stably expressed the alpha6 integrin subunit in the U87 cell line via retroviral-mediated gene transfer. We show that cell surface expression of the alpha6beta1 integrin led to dramatic changes in tumor U87 cell behavior, both in vitro and in vivo. Nude mice receiving either subcutaneous or intracerebral inoculation of alpha6beta1-expressing cells developed substantially more voluminous tumors than mice injected with control cells. The difference in tumor growth was associated with a marked increase in vascularization in response to alpha6beta1 integrin expression and may also be related to changes in the balance between cell proliferation and survival. Indeed, expression of alpha6beta1 enhanced proliferation and decreased apoptosis of U87 cells both in the tumor and in vitro. Additionally, we demonstrate that alpha6beta1 is implicated in glioblastoma cell migration and invasion and that laminin-111 might mediate dissemination of alpha6beta1-positive cells in vivo. Our results highlight for the first time the considerable role of the integrin alpha6beta1 in glioma progression.