P18.10.B Natural history of meningiomas - a serial volumetric analysis of 240 tumors

Background

The management of asymptomatic intracranial meningiomas is controversial. Through the assessment of growth predictors, we aimed to create the basis for practicable clinical pathways for the management of these tumors.

Material and Methods

We volumetrically analyzed meningiomas radiologically diagnosed at our institution between 2003 and 2015. For this purpose, we used exclusively thin-layered MR images (i.e. ≤ 2mm slice thickness). The primary endpoint was tumor growth defined as a 14.35% increase in tumor volume. We identified predictive clinical and radiological characteristics and used the significant variables from a multivariable regression model to construct a decision tree based on the exhaustive Chi-squared Automatic Interaction Detection (exhaustive CHAID) algorithm.

Results

Of 240 meningiomas, 159 (66.3%) demonstrated growth during a mean observation period of 46.9 months. On multivariable logistic regression analysis, older age (OR=0.979 (0.958-1.000), p=0.048) and presence of calcification (OR=0.442 (0.224-0.872), p=0.019) had a negative predictive value for tumor growth, while T2-signal iso-/hyperintensity (OR=4.415 (2.056-9.479), p<0.001) had a positive predictive value. A decision tree model yielded three growth risk groups based on T2-signal intensity and presence of calcifications with a proportion of growing tumors of 34.1% in the low risk group, 60.0% in the intermediate risk group and 80.2% in the high risk group. Median tumor volume doubling time (Td) was 185.7 months in the low risk, 100.1 months in the intermediate risk and 51.7 months in the high risk group (p<0.001). While 0% of meningiomas in the low and intermediate risk group had a Td of ≤12 months, 8.9% in the high risk group did so (p=0.021).

Conclusion

Most meningiomas demonstrated growth during follow-up. The presence or absence of calcifications and the signal intensity on T2-weighted imaging allow a practical and simple stratification of meningiomas into low, intermediate and high risk tumors. Small tumors in the low or intermediate risk categories can be monitored with longer follow-up intervals, whereas in the high risk category proactive management decisions can be justified.

ALS-Associated Endoplasmic Reticulum Proteins in Denervated Skeletal Muscle: Implications for Motor Neuron Disease Pathology

Alpha-motoneurons and muscle fibres are structurally and functionally interdependent. Both cell types particularly rely on endoplasmic reticulum (ER/SR) functions. Mutations of the ER proteins VAPB, SigR1 and HSP27 lead to hereditary motor neuron diseases (MNDs). Here, we determined the expression profile and localization of these ER proteins/chaperons by immunohistochemistry and immunoblotting in biopsy and autopsy muscle tissue of patients with amyotrophic lateral sclerosis (ALS) and other neurogenic muscular atrophies (NMAs) and compared these patterns to mouse models of neurogenic muscular atrophy. Postsynaptic neuromuscular junction staining for VAPB was intense in normal human and mouse muscle and decreased in denervated Nmd^2J mouse muscle fibres. In contrast, VAPB levels together with other chaperones and autophagy markers were increased in extrasynaptic regions of denervated muscle fibres of patients with MNDs and other NMAs, especially at sites of focal myofibrillar disintegration (targets). These findings did not differ between NMAs due to ALS and other causes. G93A-SOD1 mouse muscle fibres showed a similar pattern of protein level increases in denervated muscle fibres. In addition, they showed globular VAPB-immunoreactive structures together with misfolded SOD1 protein accumulations, suggesting a primary myopathic change. Our findings indicate that altered expression and localization of these ER proteins and autophagy markers are part of the dynamic response of muscle fibres to denervation. The ER is particularly prominent and vulnerable in both muscle fibres and alpha-motoneurons. Thus, ER pathology could contribute to the selective build-up of degenerative changes in the neuromuscular axis in MNDs.

Loss of function of the ALS protein SigR1 leads to ER pathology associated with defective autophagy and lipid raft disturbances

Intracellular accumulations of altered, misfolded proteins in neuronal and other cells are pathological hallmarks shared by many neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Mutations in several genes give rise to familial forms of ALS. Mutations in Sigma receptor 1 have been found to cause a juvenile form of ALS and frontotemporal lobar degeneration (FTLD). We recently described altered localization, abnormal modification and loss of function of SigR1 in sporadic ALS. In order to further elucidate the molecular mechanisms underlying SigR1-mediated alterations in sporadic and familial ALS, we extended our previous studies using neuronal SigR1 knockdown cell lines. We found that loss of SigR1 leads to abnormal ER morphology, mitochondrial abnormalities and impaired autophagic degradation. Consistent with these results, we found that endosomal trafficking of EGFR is impaired upon SigR1 knockdown. Furthermore, in SigR1-deficient cells the transport of vesicular stomatitis virus glycoprotein is inhibited, leading to the accumulation of this cargo protein in the Golgi apparatus. Moreover, depletion of SigR1 destabilized lipid rafts and associated calcium mobilization, confirming the crucial role of SigR1 in lipid raft and intracellular calcium homeostasis. Taken together, our results support the notion that loss of SigR1 function contributes to ALS pathology by causing abnormal ER morphology, lipid raft destabilization and defective endolysosomal pathways.