RESUMO
Diffuse invasion of the surrounding brain parenchyma is a major obstacle in the treatment of gliomas with various therapeutics, including anti-angiogenic agents. Here we identify the epi-/genetic and microenvironmental downregulation of ephrinB2 as a crucial step that promotes tumour invasion by abrogation of repulsive signals. We demonstrate that ephrinB2 is downregulated in human gliomas as a consequence of promoter hypermethylation and gene deletion. Consistently, genetic deletion of ephrinB2 in a murine high-grade glioma model increases invasion. Importantly, ephrinB2 gene silencing is complemented by a hypoxia-induced transcriptional repression. Mechanistically, hypoxia-inducible factor (HIF)-1α induces the EMT repressor ZEB2, which directly downregulates ephrinB2 through promoter binding to enhance tumour invasiveness. This mechanism is activated following anti-angiogenic treatment of gliomas and is efficiently blocked by disrupting ZEB2 activity. Taken together, our results identify ZEB2 as an attractive therapeutic target to inhibit tumour invasion and counteract tumour resistance mechanisms induced by anti-angiogenic treatment strategies.
Assuntos
Resistencia a Medicamentos Antineoplásicos , Efrina-B2/genética , Glioma/genética , Glioma/patologia , Neovascularização Patológica/genética , Neovascularização Patológica/patologia , Homeobox 2 de Ligação a E-box com Dedos de Zinco/metabolismo , Inibidores da Angiogênese/farmacologia , Inibidores da Angiogênese/uso terapêutico , Animais , Bevacizumab/farmacologia , Bevacizumab/uso terapêutico , Hipóxia Celular/genética , Regulação para Baixo/genética , Resistencia a Medicamentos Antineoplásicos/genética , Efrina-B2/metabolismo , Regulação Neoplásica da Expressão Gênica , Glioma/irrigação sanguínea , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Invasividade Neoplásica , Neovascularização Patológica/tratamento farmacológico , Neovascularização Patológica/metabolismo , Regulação para Cima/genética , Ensaios Antitumorais Modelo de Xenoenxerto , Homeobox 2 de Ligação a E-box com Dedos de Zinco/genéticaRESUMO
The concept of cancer stem-like cells (CSCs) has gained considerable attention in various solid tumors including glioblastoma, the most common primary brain tumor. This sub-population of tumor cells has been intensively investigated and their role in therapy resistance as well as tumor recurrence has been demonstrated. In that respect, development of therapeutic strategies that target CSCs (and possibly also the tumor bulk) appears a promising approach in patients suffering from primary brain tumors. In the present study, we utilized RNA interference (RNAi) to screen the complete human kinome and phosphatome (682 and 180 targets, respectively) in order to identify genes and pathways relevant for the survival of brain CSCs and thereby potential therapeutical targets for glioblastoma. We report of 46 putative candidates including known survival-related kinases and phosphatases. Interestingly, a number of genes identified are involved in metabolism, especially glycolysis, such as PDK1 and PKM2 and, most prominently PFKFB4. In vitro studies confirmed an essential role of PFKFB4 in the maintenance of brain CSCs. Furthermore, high PFKFB4 expression was associated with shorter survival of primary glioblastoma patients. Our findings support the importance of the glycolytic pathway in the maintenance of malignant glioma cells and brain CSCs and imply tumor metabolism as a promising therapeutic target in glioblastoma.
Assuntos
Glioma/genética , Glioma/patologia , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Fosfofrutoquinase-2/deficiência , Fosfofrutoquinase-2/genética , Interferência de RNA , Trifosfato de Adenosina/biossíntese , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Morte Celular/genética , Sobrevivência Celular/genética , Regulação Neoplásica da Expressão Gênica/genética , Glioma/diagnóstico , Glioma/metabolismo , Glicólise/genética , Humanos , Isoenzimas/deficiência , Isoenzimas/genética , Ácido Láctico/biossíntese , Lentivirus/genética , Prognóstico , RNA Interferente Pequeno/genéticaRESUMO
Deletions of chromosomal arms 1p and 19q are frequent in oligodendroglial tumours and linked to radio- and chemotherapy response as well as longer survival. The molecular mechanisms underlying this clinically important association are as yet unknown. Here, we studied the peroxiredoxin 1 (PRDX1) gene at 1p34.1 for promoter methylation and expression in primary gliomas and investigated its role in radio- and chemosensitivity of glioma cells in vitro. In total, we screened primary glioma tissues from 93 patients for methylation of the 5'-CpG island of PRDX1 by sodium bisulfite sequencing. PRDX1 mRNA and protein expression levels were determined in subsets of the tumours by quantitative PCR and western blot analysis, respectively. PRDX1 hypermethylation and reduced expression were frequently detected in oligodendroglial tumours and secondary glioblastomas, but not in primary glioblastomas. In oligodendroglial tumours, both PRDX1 hypermethylation and reduced mRNA expression were significantly associated with 1p/19q-deletion. Stable knockdown of PRDX1 by lentiviral transduction of short-hairpin (sh)RNA constructs significantly increased apoptosis and reduced cell viability of Hs683 glioma cells exposed to ionizing irradiation or temozolomide in vitro. Taken together, our findings indicate that epigenetic silencing of PRDX1 is frequent in 1p/19q-deleted oligodendroglial tumours and likely contributes to radio- and chemosensitivity of these tumours.
Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 1/genética , Glioma/patologia , Oligodendroglia/metabolismo , Peroxirredoxinas/genética , Regiões Promotoras Genéticas/genética , Tolerância a Radiação/genética , Adulto , Idoso , Apoptose/efeitos dos fármacos , Apoptose/genética , Apoptose/efeitos da radiação , Linhagem Celular Tumoral , Ilhas de CpG/genética , Metilação de DNA/efeitos dos fármacos , Metilação de DNA/efeitos da radiação , Dacarbazina/análogos & derivados , Dacarbazina/farmacologia , Regulação para Baixo/genética , Feminino , Técnicas de Silenciamento de Genes , Inativação Gênica , Glioma/tratamento farmacológico , Glioma/genética , Glioma/radioterapia , Humanos , Isocitrato Desidrogenase/genética , Masculino , Pessoa de Meia-Idade , Mutação , Oligodendroglia/efeitos dos fármacos , Oligodendroglia/patologia , Oligodendroglia/efeitos da radiação , Peroxirredoxinas/deficiência , Regiões Promotoras Genéticas/efeitos dos fármacos , Regiões Promotoras Genéticas/efeitos da radiação , Temozolomida , Adulto JovemRESUMO
Blue Cross and Blue Shield of Michigan assessed the intensity of inpatient laboratory use for similar patients in a sample of 30 short-term hospitals in three geographic areas. Hospital records were abstracted for 1,834 patients treated in 1980 for uncomplicated (Stage 1) admissions involving eight common diagnoses. It was found that patients treated in osteopathic teaching hospitals received significantly more laboratory tests than similar patients in allopathic teaching or nonteaching hospitals. Statistically significant differences were also found among the three geographic areas in the sample.