The Clinical Significance of O6-Methylguanine-DNA Methyltransferase Promoter Methylation Status in Adult Patients With Glioblastoma: A Meta-analysis.

BACKGROUND AND OBJECTIVE: Promoter status of O6-methylguanine-DNA methyltransferase (MGMT) has been widely established as a clinically relevant factor in glioblastoma (GBM) patients. However, in addition to varied therapy schedule, the prognosis of GBM patients is also affected by variations of age, race, primary or recurrent tumor. This study comprehensively investigated the association between MGMT promoter status and prognosis in overall GBM patients and in different GBM subtype including new diagnosed patients, recurrent patients and elderly patients. METHODS: A comprehensive search was performed using PubMed, EMBASE, Cochrane databases to identify literatures (published from January 1, 2005 to April 1, 2017) that evaluated the associations between MGMT promoter methylation and prognosis of GBM patients. RESULTS: Totally, 66 studies including 7,886 patients met the inclusion criteria. Overall GBM patients with a methylated status of MGMT receiving temozolomide (TMZ)-containing treatment had better overall survival (OS) and progression-free survival (PFS) [OS: hazard ratio (HR) = 0.46, 95% confidence interval (CI): 0.41-0.52, p < 0.001, Bon = 0.017; PFS: HR = 0.48, 95% CI 0.40-0.57, p < 0.001, Bon = 0.014], but no significant advantage on OS or PFS in GBM patients with TMZ-free treatment was observed (OS: HR = 0.97, 95% CI 0.91-1.03, p = 0.08, Bon = 1; PFS: HR = 0.76, 95% CI 0.57-1.02, p = 0.068, Bon = 0.748). These different impacts of MGMT status on OS were similar in newly diagnosed GBM patients, elderly GBM patients and recurrent GBM. Among patients receiving TMZ-free treatment, survival benefit in Asian patients was not observed anymore after Bonferroni correction (Asian OS: HR = 0.78, 95% CI 0.64-0.95, p = 0.02, Bon = 0.24, I2 = 0%; PFS: HR = 0.69, 95% CI 0.50-0.94, p = 0.02, Bon = 0.24). No benefit was observed in Caucasian receiving TMZ-free therapy regardless of Bonferroni adjustment. CONCLUSION: The meta-analysis highlights the universal predictive value of MGMT methylation in newly diagnosed GBM patients, elderly GBM patients and recurrent GBM patients. For elderly methylated GBM patients, TMZ alone therapy might be a more suitable option than radiotherapy alone therapy. Future clinical trials should be designed in order to optimize therapeutics in different GBM subpopulation.

Involvement of ROS-alpha v beta 3 integrin-FAK/Pyk2 in the inhibitory effect of melatonin on U251 glioma cell migration and invasion under hypoxia.

BACKGROUND: Melatonin, a well-known antioxidant, has been shown to possess anti-invasive properties for glioma. However, little is known about the effect of melatonin on glioma cell migration and invasion under hypoxia, which is a crucial microenvironment for tumor progress. In addition, focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) are closely associated with cell migration and invasion. Therefore, we investigated the possible role of these kinases and its related signaling in the regulation of human U251 glioma cells behavior by melatonin under hypoxia. METHODS: The abilities of migration and invasion of U251 glioma cells were determined by wound healing and transwell assay in vitro. The intracellular production of reactive oxygen species (ROS) was measured by using the fluorescent probe 6-carboxy-2', 7'-dichorodihydrofluorescein diacetate (DCFH-DA). Immunofluorescence experiments and western blotting analysis were used to detect the expression level of protein. Small interfering RNAs (siRNA) was used to silence specific gene expression. RESULTS: The pharmacologic concentration (1 mM) of melatonin significantly inhibited the migration and invasion of human U251 glioma cells under hypoxia. The inhibitory effect of melatonin was accompanied with the reduced phosphorylation of FAK and Pyk2, and decreased expression of alpha v beta 3 (αvß3) integrin. Additionally, inhibition of αvß3 integrin by siRNA reduced the phosphorylation of FAK/Pyk2 and demonstrated the similar anti-tumor effects as melatonin, suggesting the involvement of αvß3 integrin- FAK/Pyk2 pathway in the anti-migratory and anti-invasive effect of melatonin. It was also found that melatonin treatment decreased the ROS levels in U251 glioma cells cultured under hypoxia. ROS inhibitor apocynin not only inhibited αvß3 integrin expression and the phosphorylation levels of FAK and Pyk2, but also suppressed the migratory and invasive capacity of U251 glioma cells under hypoxia. CONCLUSIONS: These results suggest that melatonin exerts anti-migratory and anti-invasive effects on glioma cells in response to hypoxia via ROS-αvß3 integrin-FAK/Pyk2 signaling pathways. This provides evidence that melatonin may be a potential therapeutic molecule targeting the hypoxic microenvironment of glioma.

[The expression of hepatocyte growth factor and its receptor in brain astrocytomas].

OBJECTIVE: To investigate the expression of hepatocyte growth factor (HGF) mRNA and its receptor (c-Met) mRNA in brain astrocytomas and their relationships with tumor proliferation, angiogenesis, clinical pathology and prognosis. METHODS: The expression of HGF mRNA, c-Met mRNA in the resected tumor tissues of 76 patients with brain astrocytomas, 43 males and 33 females, aged 20 - 71, were detected by in situ hybridization. Immunohistochemistry technique was used to test the expression of proliferating cell nuclear antigen (PCNA) protein and the microvessel density (MVD) was determined by immunohistochemistry with monoclonal antibody against CD34. RESULTS: The positive rates of expression of HGF, c-Met and PCNA in low pathologic grades of brain astrocytoma were 34.5%, 44.8% and 15% +/- 9% respectively, and in high pathologic grades of brain astrocytoma were 34.5%, 44.8% and 48% +/- 12% respectively (P < 0.05). MVD in low and high pathologic grades of brain astrocytoma were 17 +/- 7 and 31 +/- 13 respectively (P < 0.05). The expression of HGF, c-Met, PCNA and CD34 was not related to sex, age, position of tumor and diameter of tumor. The expression of c-Met was related to the expression of HGF, PCNA and the MVD in the tumor tissues of these patients. The pathological grade, position of tumor, HGF, c-Met, PCNA, MVD had a significant influence on the survival time. CONCLUSION: HGF/c-Met plays an important role in the formation and progression of the brain astrocytoma and can promote tumor proliferation and intratumoral microvascular formation, and is closely related to the prognosis of the patients.