Prognostic significance of brain invasion in meningiomas: systematic review and meta-analysis

The WHO 2016 classification introduced brain invasion as a standalone criterion for grade II meningioma (GIIM). We systematically reviewed studies published after 2000 and performed a PRISMA-compliant meta-analysis of the hazard ratios (HRs) for progression-free survival (PFS) between brain-invasive and noninvasive meningiomas. In five studies that included both benign and higher-grade meningiomas, brain invasion was a significant risk factor for recurrence (HR = 2.45, p = 0.0004). However, in 3 studies comparing "brain-invasive meningioma with otherwise benign histology (BIOB)" with grade I meningioma, brain invasion was not a significant predictor of PFS (HR = 1.49, p = 0.23). Among GIIM per the WHO 2000 criteria, brain invasion was a significant predictor of shorter PFS than noninvasive GIIM (HR = 3.40, p = 0.001) but not per the WHO 2016 criteria (HR 1.13, p = 0.54), as the latter includes BIOB. Meta-regression analysis of seven studies of grade II meningioma showed that more frequent BIOB was associated with lower HRs (p < 0.0001). Hence, there is no rationale for brain invasion as a standalone criterion for grade II meningioma, although almost all studies were retrospective and exhibited highly heterogeneous HRs due to differences in brain-tumor interface data availability.

Genetic/molecular alterations of meningiomas and the signaling pathways targeted

Meningiomas are usually considered to be benign central nervous system tumors; however, they show heterogenous clinical, histolopathological and cytogenetic features associated with a variable outcome. In recent years important advances have been achieved in the identification of the genetic/molecular alterations of meningiomas and the signaling pathways involved. Thus, monosomy 22, which is often associated with mutations of the NF2 gene, has emerged as the most frequent alteration of meningiomas; in addition, several other genes (e.g., AKT1, KLF4, TRAF7, SMO) and chromosomes have been found to be recurrently altered often in association with more complex karyotypes and involvement of multiple signaling pathways. Here we review the current knowledge about the most relevant genes involved and the signaling pathways targeted by such alterations. In addition, we summarize those proposals that have been made so far for classification and prognostic stratification of meningiomas based on their genetic/genomic features.

Overexpression of RLIP76 Required for Proliferation in Meningioma Is Associated with Recurrence

The GTPase-activating protein RLIP76 is overexpressed in and correlates with the pathological grade of many malignant tumor cells. But the potential correlation between RLIP76 and clinical outcomes in patients with meningioma remains unknown. In this study, we examined the expression of RLIP76 in meningioma and correlated the RLIP76 expression to the patient outcome. RLIP76 expression in tumor tissues was examined with immunohistochemistry, quantitative reverse-transcription polymerase chain reaction(RT-PCR) and Western-blot. Immunohistochemistry showed an increased RLIP76 immunostaining score in anaplastic and atypical meningiomas versus classical meningiomas. Statistical analyses revealed that RLIP76 immunostaining positively correlated with immunostaining for Ki-67, a nuclear protein highly expressed in proliferating cells(r=0.29, p=0.034 by Spearman's correlation coefficient). Clinicopathological evaluation suggested that RLIP76 expression be associated with tumor grade and recurrence(P<0.05). Univariate and Cox analysis indicated that RLIP76 was an independent prognostic factor for tumor recurrence. Furthermore, the human malignant meningioma cell lines IOMM-Lee and CH157-MN stably transfected with short hairpin RNA (siRNA) targeting RLIP76 were then examined by in vitro growth assays, and apoptosis assays. RLIP76 knockdown in IOMM-Lee and CH157-MN cells inhibited cell proliferation and induced apoptosis. Western blot analysis revealed that cells underexpressing RLIP76 exhibited decreased B-cell lymphoma-2(Bcl-2) expression but increased apoptosis effector caspase-3 expression. These findings demonstrate that high RLIP76 expression is associated with a poor outcome of meningioma and may provide a new gene therapy approach for patients with malignant meningiomas.

Presence of matrix metalloproteinase-2 and tissue inhibitor matrix metalloproteinase-2 gene polymorphisms and immunohistochemical expressions in intracranial meningiomas

OBJECT

Meningiomas are benign extraaxial tumors with a slow progression. Some of them, in spite of being benign in nature, may show an aggressive progression pattern. To investigate the behavioral characteristics of meningiomas, researchers have studied matrix metalloproteinases (MMPs), their tissue inhibitors (TIMPs), interstitial collagens, proteins, vascular endothelial growth factors (VEGF), and tumor necrosis factors.

METHODS

In this study, the authors investigated MMP2 and TIMP2 gene polymorphisms in formalin-fixed paraffin-embedded tissue samples obtained from meningioma patients who had previously undergone surgery at the authors' institution. In addition, brain invasion, Ki-67 index, and MMP-2 and TIMP-2 expressions were investigated using immunohistochemical methods. MMP2 (735C>T, 1575G>A, 1306C>T) and TIMP2 (418G>C, 303C>T) gene polymorphisms were investigated from paraffin-embedded tissue sections using the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

There were statistically significant differences between genotype (p = 0.001) and allele frequencies (p = 0.001 and OR 7.4 [95% CI 1.5-36.2]) in patient and control groups for MMP2 1306C>T polymorphism. The authors did not find a statistically significant difference for other polymorphisms. GA genotype was found to be more frequent when brain invasion was suspected for MMP2 1575G>A polymorphism (p = 0.006). There was not a statistically significant difference for other MMP2 or TIMP2 gene polymorphisms.

CONCLUSIONS

The authors' results support the importance of MMPs and their tissue inhibitors in meningioma pathogenesis. In future studies, these gene polymorphisms, especially MMP2 1306C>T and 1575G>A, should be investigated for meningioma or brain invasion susceptibility in larger study groups.

Predicting outcomes of patients with intracranial meningiomas using molecular markers of hypoxia, vascularity, and proliferation

BACKGROUND

The natural history of surgically treated intracranial meningiomas can be quite variable. Recurrence and patient outcome cannot currently be predicted with accuracy.

OBJECTIVE

To explore the potential roles of tumor hypoxia-regulated biological markers, preoperative imaging, measures of proliferation, and angiogenesis in predicting patient outcome.

METHODS

Tissue from 263 patients (average follow-up, 75 months) was examined for molecular markers hypoxia-inducible factor-1α (HIF-1α), carbonic anhydrase-IX (CA-IX), and glucose transporter-1 (Glut-1); vascular endothelial growth factor (VEGF); proliferation (MIB-1); and microvascular density (MVD) (Factor VIII). Preoperative magnetic resonance images were also examined for tumor size and peritumoral brain edema (PTBE).

RESULTS

VEGF, HIF-1α, CA-IX, and Glut-1 are positively correlated (P < .001-.005). PTBE was associated with higher grade (P = .03), larger tumors (P = .02), and log of MVD (P = .004). Progression-free survival (PFS) was associated with higher grade (P < .001), subtotal resection (P = .004), VEGF expression (P = .004), and log of MIB-labeling index (P < .001) on pairwise comparisons. Using multivariate analysis, PFS was associated with subtotal resection (HR 2.71, P = .027), higher grade (HR 6.29, P < .001), higher VEGF expression (HR 1.52, P = .038), and log of MIB-labeling index (HR 1.68, P = .005). Shorter overall survival was associated with subtotal resection (HR 3.23, P = .002), higher grade (HR 4.47, P < .001), higher expression of HIF-1α (HR 1.56, P < .001) and Glut-1 (HR 1.39, P = .02), and log of MIB-labeling index (HR 1.87, P < .001) when controlled for age.

CONCLUSION

HIF, VEGF, and MIB-1 are significantly correlated with tumor recurrence. With further study, these molecular markers may be used to predict outcome for patients with intracranial meningiomas.

The significance of Ki-67/MIB-1 labeling index in human meningiomas: a literature study

Histology alone does not always predict the clinical outcome of human meningiomas. Determination of proliferative activity has therefore become an important diagnostic and prognostic tool to identify more aggressive meningiomas, and the Ki-67/MIB-1 monoclonal antibody has become widely used. The aim of this study was to assess the prognostic value of the Ki-67/MIB-1 labeling index (LI) in human meningiomas by a search in the literature. In PubMed/Medline databases, 53 articles were found, and they all showed positive correlations between Ki-67/MIB-1 LI and histological malignancy grade. The average mean labeling indices were 3%, 8%, and 17% for grade I-III meningiomas, respectively. There was, however, considerable overlap of indices between the malignancy groups. Concerning recurrence, meningiomas with a labeling index beyond 4% may indicate an increased relapse rate. Consequently, Ki-67/MIB-1 LI represents a useful predictor of tumor grade and risk of recurrence, however, it must be interpreted cautiously in the individual tumor.