Human prion diseases and the prion protein - what is the current state of knowledge?

Prion diseases and the prion protein are only partially understood so far in many aspects. This explains the continued research on this topic, calling for an overview on the current state of knowledge. The main objective of the present review article is to provide a comprehensive up-to-date presentation of all major features of human prion diseases bridging the gap between basic research and clinical aspects. Starting with the prion protein, current insights concerning its physiological functions and the process of pathological conversion will be highlighted. Diagnostic, molecular, and clinical aspects of all human prion diseases will be discussed, including information concerning rare diseases like prion-associated amyloidoses and Huntington disease-like 1, as well as the question about a potential human threat due to the transmission of prions from prion diseases of other species such as chronic wasting disease. Finally, recent attempts to develop future therapeutic strategies will be addressed.

The Spectrum of Molecular Pathways in Gliomas-An Up-to-Date Review.

During the last 20 years, molecular alterations have gained increasing significance in the diagnosis and biological assessment of tumors. Gliomas represent the largest group of tumors of the central nervous system, and the main aim of this review is to present the current knowledge on molecular pathways and their alterations in gliomas. A wide range of new insights has been gained, including evidence for the involvement of the WNT pathway or the hippo pathway in the pathobiology of gliomas, indicating a broad involvement of different pathways formerly not considered to play a central role in gliomas. Even new aspects of angiogenic, apoptotic, and metabolic pathways are presented, as well as the rapidly growing field of epigenetic processes, including non-coding RNAs. The two major conclusions drawn from the present review are the distinct interconnectivity of the whole spectrum of molecular pathways and the prominent role of non-coding RNAs, especially circular RNAs, in the regulation of specific targets. All these new insights are discussed, even considering the topic of the resistance to therapy of gliomas, along with aspects that are still incompletely understood, like the role of hydroxymethylation, or even ferroptosis, in the pathobiology of gliomas.

Adult-type and Pediatric-type Diffuse Gliomas : What the Neuroradiologist Should Know.

The classification of diffuse gliomas into the adult type and the pediatric type is the new basis for the diagnosis and clinical evaluation. The knowledge for the neuroradiologist should not remain limited to radiological aspects but should be based additionally on the current edition of the World Health Organization (WHO) classification of tumors of the central nervous system (CNS). This classification defines the 11 entities of diffuse gliomas, which are included in the 3 large groups of adult-type diffuse gliomas, pediatric-type diffuse low-grade gliomas, and pediatric-type diffuse high-grade gliomas. This article provides a detailed overview of important molecular, morphological, and clinical aspects for all 11 entities, such as typical genetic alterations, age distribution, variability of the tumor localization, variability of histopathological and radiological findings within each entity, as well as currently available statistical information on prognosis and outcome. Important differential diagnoses are also discussed.

Cellular Components of the Tumor Environment in Gliomas-What Do We Know Today?

A generation ago, the molecular properties of tumor cells were the focus of scientific interest in oncology research. Since then, it has become increasingly apparent that the tumor environment (TEM), whose major components are non-neoplastic cell types, is also of utmost importance for our understanding of tumor growth, maintenance and resistance. In this review, we present the current knowledge concerning all cellular components within the TEM in gliomas, focusing on their molecular properties, expression patterns and influence on the biological behavior of gliomas. Insight into the TEM of gliomas has expanded considerably in recent years, including many aspects that previously received only marginal attention, such as the phenomenon of phagocytosis of glioma cells by macrophages and the role of the thyroid-stimulating hormone on glioma growth. We also discuss other topics such as the migration of lymphocytes into the tumor, phenotypic similarities between chemoresistant glioma cells and stem cells, and new clinical approaches with immunotherapies involving the cells of TEM.

Heterogeneity in malignant gliomas: a magnetic resonance analysis of spatial distribution of metabolite changes and regional blood volume.

First-pass contrast-enhanced dynamic perfusion imaging provides information about the regional cerebral blood volume (rCBV), an increase of which indicates neovascularization. MR spectroscopic imaging informs about metabolite changes in brain tumors, with elevated choline (Cho) values revealing cell proliferation and density, and the glial metabolite creatine (Cr) representing high-energy storage. This study investigates metabolite changes within the tumor voxel of maximal rCBV value (rCBVmax). Anatomically coregistered parameter maps of rCBV, Cho and Cr were evaluated in 36 patients with primary or recurrent WHO grade III or IV gliomas. Apart from Cho and Cr values within the voxel of rCBVmax (Choperf, Crperf), the maximal Cho and Cr values of the tumor tissue were recorded (Chomax, Crmax). The correlation between these parameters was analyzed with Spearman's rho test while a binomial test was performed to check whether Chomax = Choperf and Crmax = Crperf. We found that, in 29 of the 36 patients, neither Cho nor Cr had their maxima in the voxel of rCBVmax (Choperf, Crperf < Chomax, Crmax, P < 0.001). However, Choperf was highly correlated with Chomax (r = 0.76, P < 0.001) and Crperf with Crmax (r = 0.47, P < 0.001). Further Choperf correlated with Crperf (r = 0.55, P < 0.001). Neither of the spectroscopic parameters (Chomax, Crmax, Choperf, Crperf,) correlated with rCBVmax. In conclusion, in WHO grade III and IV gliomas the voxel with maximal rCBV often differs from the voxel with the maximal Cho and Cr, indicating the spatial divergence between neovascularization and tumor cell proliferation, cell density and glial processes. However, tCho and tCr changes within the area of neovascularization are positively correlated with the maximal increase within the tumor tissue. These results demonstrate aspects of regional tumor heterogeneity as characterized by different MR modalities that, apart from histopathological grading might be crucial for neurosurgical biopsy as well as for antiangiogenetic and future molecular therapies.

Correlation between amplification of the gene for the epidermal growth factor receptor (EGFR), data from preoperative proton-MR-spectroscopy (1HMRS) and histomorphometric data of glioblastomas.

OBJECTIVE: To investigate a correlation between preoperative data from proton-MR-spectroscopy (1HMRS), genomic alterations (epidermal growth growth factor receptor [EGFR] gene amplification) and histomorphometric data from glioblastomas. STUDY DESIGN: In surgical specimens from 18 patients with glioblastomas, the degree of amplification of the gene for EGFR was determined in the region with the largest Ki-67 proliferation index by differential polymerase chain reaction. RESULTS: Correlation analysis showed significant positive correlation between degree of EGFR gene amplification and choline and total creatine (CHO/TCR) ratio, indicating increased membrane turnover. Cases with a high EGFR/interferon ratio showed a tendency toward a low lipid peak, whereas cases with a low EGFR/interferon ratio showed a large variation of the lipid peak. Differences were observed regarding quantitative histomorphologic data of tumor cell nuclei, especially nuclear size and shape. Together with the EGFR/interferon ratio, these morphometric data provided a good reclassification of cases with low and with high values for both spectroscopic variables by means of cross-validated linear discriminant analysis. CONCLUSION: The results provide further evidence for the biologic significance of metabolic data from preoperative 1HMRS, because these metabolic data showed a significant statistical relationship with histomorphology and a frequently occurring molecular biologic alteration (EGFR gene amplification) in glioblastomas.

The morphology of perinecrotic tumor cell nuclei in glioblastomas shows a significant relationship with survival time.

A deeper knowledge about histopathological criteria with a significant impact on the prognosis of patients with glioblastomas is worthwhile, since these patients may show a considerable difference in the time of survival. Investigation of the morphology of perinecrotic tumor cell nuclei is a promising approach, because the expression of specific molecules in these cells has been associated with a more aggressive behaviour of the tumors. In our series of patients with documented clinical course, 11 patients had a survival of at least 24 months and we compared this group with a group of 10 patients with maximum survival of 12 months. Digital microscopic image analysis was performed in paraffin sections from the primary surgical specimen. Three hundred perinecrotic tumor cell nuclei per case and 300 nuclei per case from tumor cells lying more distant from the tumor necroses ('distant zone' nuclei) were measured. The ratio for the numerical nuclear density between both types of nuclei was significantly larger in cases with short survival indicating a more pronounced nuclear density of perinecrotic nuclei in relation to the 'distant zone' nuclei in these tumors. In cases with long survival, on the contrary, perinecrotic tumor cells exhibited an only slightly larger numerical density compared with 'distant zone' nuclei. Mean values and standard deviations from parameters of nuclear shape (Fourier-amplitudes) had significantly smaller values in short-time survivors indicating a tendency towards a more circular nuclear shape with less pronounced intratumoral variation in that group. Based on the morphometric results, all cases could be correctly reclassified as short- or long-time survivors by means of cross-validated discriminant analysis. In conclusion, the results confirm significant morphological differences between tumors from patients with short and with long survival regarding morphology of both types of tumor cell nuclei. It seems likely, that histomorphometry of tumor cell nuclei could be a promising approach for the assessment of the individual prognosis of patients with glioblastomas.

Application of different methods for nuclear shape analysis with special reference to the differentiation of brain tumors.

OBJECTIVE: To study the discriminatory power of different methods designed for nuclear shape analysis with reference to the differentiation and grading of brain tumors and the differentiation between proliferating and nonproliferating nuclei. STUDY DESIGN: At least 300 tumor cell nuclei per case were measured by means of a digital image analysis system. Fourier amplitudes no. 1 to 15, moments no. 1 to 7 according to Hu, roundness factor, ellipse shape factor, concavity factor, Feret ratio, fractal dimension and bending energy were determined for each nucleus. The discriminatory power of these parameters was tested in three pairwise comparisons: (1) oligodendrogliomas WHO grade II (n = 13) vs. grade III (n = 11), (2) medulloblastomas WHO grade IV (n = 14) vs. anaplastic ependymomas WHO grade III (n = 12), (3) Ki-67-positive vs. Ki-67-negative tumor cell nuclei in the 14 medulloblastomas. RESULTS: When data from Fourier analysis were included in statistical analysis, cross-validated discriminant analysis led to a 100% correct reclassification for the first and for the second pairwise comparison and to a 75% correct reclassification when comparing Ki-67-positive and Ki-67-negative nucleifrom medulloblastomas. Different combinations of the other shape parameters led to a lower percentage of correctly reclassified cases for all three pairwise comparisons, especially when Fourier analysis was not included in the analysis. CONCLUSION: Fourier analysis provided an optimal statistical discrimination between different brain tumor entities and between data sets from proliferating and nonproliferating tumor cell nuclei. Since nuclear shape is an important criterion for the investigation of tumors, the application of Fourier analysis is therefore recommended for quantitative histologic investigations in neuro-oncology.

Morphology of tumor cell nuclei is significantly related with survival time of patients with glioblastomas.

PURPOSE: To investigate whether histomorphology of tumor cell nuclei has a significant and independent relation to survival time of patients with glioblastomas. EXPERIMENTAL DESIGN: Seventy-two tumors from 72 patients were investigated by means of digital image analysis. Proliferating and nonproliferating nuclei were separately measured and parameters of nuclear size, shape, texture, and spatial relationships (topometric parameters) were detected. Survival analysis was done regarding morphometric data together with the patients' age, the amount of resection (total or subtotal), and the classification of the tumor as a "primary" (de novo) or "secondary" glioblastoma. RESULTS: The overall relation of all morphometric data to the time of survival was highly significant (Cox analysis, P < 0.0001). Apart from the extent of surgical resection, parameters of nuclear shape and topometric variables, such as the distance between two nuclei lying nearest to each other, showed an independent and significant relation to survival time. The patients' age had also a significant but comparably slight relation to survival time. CONCLUSIONS: The morphology of tumor cell nuclei, as represented by morphometric data, shows a significant relation to survival time of patients with glioblastomas. This relation is statistically independent from the amount of surgical resection, from the patients' age and from the classification of the glioblastoma as being primary or secondary. The results support the view that histomorphometry of tumor cell nuclei is a valuable prognostic marker for patients with glioblastomas. We believe that such a marker ought to be incorporated into the formation of individual therapeutic decisions.

Fourier analysis of intracranial aneurysms: towards an objective and quantitative evaluation of the shape of aneurysms.

Shape irregularities of intracranial aneurysms may indicate an increased risk of rupture. To quantify morphological differences, Fourier analysis of the shape of intracranial aneurysms was introduced. We compared the morphology of 45 unruptured (UIA) and 46 ruptured intracranial aneurysms (RIA) in 70 consecutive patients on the basis of 3D-rotational angiography. Fourier analysis, coefficient of roundness and qualitative shape assessment were determined for each aneurysm. Morphometric analysis revealed significantly smaller coefficient of roundness (P < 0.02) and higher values for Fourier amplitudes numbers 2, 3 and 7 (P < 0.01) in the RIA group, indicating more complex and irregular morphology in RIA. Qualitative assessment from 3D-reconstructions showed surface irregularities in 78% of RIA and 42% of UIA (P < 0.05). Our data have shown significant differences in shape between RIA and UIA, and further developments of Fourier analysis may provide an objective factor for the assessment of the risk of rupture.

Morphology of proliferating and non-proliferating tumor cell nuclei in glioblastomas correlates with preoperative data from proton-MR-spectroscopy.

In contrast to the growing interest in proton-MR-spectroscopy (1HMRS) for preoperative examination of patients with brain tumors, there is nearly no knowledge about a correlation between data from 1HMRS and histomorphology as confirmed by quantitative morphological methods. Whether a correlation can be confirmed between data from 1HMRS and quantitative histomorphology of glioblastomas representing the most frequent type of brain tumors was investigated in the present study. Furthermore, it was of interest, whether correlations between spectroscopic data and histomorphology can be confirmed for proliferating and non-proliferating tumor cell nuclei independently. Using stringent inclusion criteria for this study, 24 patients were investigated by means of preoperative 1HMRS and by means of digital image analysis of paraffin sections from the surgical specimen. Proliferating and non-proliferating tumor cell nuclei were investigated separately in the region with the highest proliferative activity in each tumor using immunohistological staining for the proliferation marker Ki67. Main results showed highly significant correlations between total creatine and variables of nuclear size, as well as correlations between choline and variables of nuclear shape. These results were confirmed for both proliferating and non-proliferating tumor cell nuclei. A significant correlation between N-acetyl-aspartate level and topometric variables (number of neighbors per nucleus, variables describing distances between tumor cell nuclei) was confirmed for proliferating tumor cell nuclei. Discriminant analysis provided a good separation of cases with high and with low values for these spectroscopic variables based on histomorphometric data. In conclusion, the results confirm a direct correlation between data from preoperative 1HMRS and histomorphological characteristics of glioblastomas supporting the biological relevance of spectroscopic data for the examination of brain tumor patients.

Regional heterogeneity of EGFR gene amplification and nuclear morphology in glioblastomas. An investigation using laser microdissection and pressure catapulting.

OBJECTIVE: To study the regional heterogeneity of epidermal growth factor receptor (EGFR) gene amplification (EGFR-GA) in glioblastomas, considering the relationship between this mutation and morphology of tumor cell nuclei. STUDY DESIGN: Tissue samples gained by laser microdissection and pressure catapulting were used for the performance of differential polymerase chain reaction in 32 morphologically different regions from 7 glioblastomas. Semiquantitative determination of EGFR expression and image analysis of tumor cell nuclei were performed in the same regions. RESULTS: Distinct regional differences concerning the degree of EGFR-GA were found in 2 tumor cases. When comparing regions with different degrees of gene amplification within these cases, morphologic differences in tumor cell nuclei were observed. The other tumor cases also showed distinct intratumoral heterogeneity concerning histomorphology but no regional heterogeneity in the degree of EGFR-GA. When comparing regions with a low densitometric EGFR/interferon (INF) band ratio (< 2.19, n = 18) and a high EGFR/IFN band ratio (> 4.39, n = 14), the latter type of region showed a significantly higher percentage of Ki-67--positive tumor cell nuclei and lower values for several shape variables (Fourier amplitudes), indicating a tendency toward a more regular nuclear shape in regions with distinct EGFR-GA. For the EGFR/IFN band ratio, a significant correlation was found with several morphometric variables, especially those of nuclear shape and distances between nuclei. CONCLUSION: In glioblastomas showing regional heterogeneity in the degree of EGFR-GA, morphology of tumor cell nuclei has been shown to be different when comparing regions with different degrees of EGFR-GA. Glioblastomas may also show distinct regional heterogeneity of histomorphology without evidence of regional heterogeneity of EGFR-GA. A significant statistical association has been confirmed between the degree of EGFR-GA and quantitative morphology of tumor cell nuclei.

Preoperative proton-MR spectroscopy of gliomas--correlation with quantitative nuclear morphology in surgical specimen.

A comparison between data from proton-MR spectroscopy (1HMRS) and quantitative histomorphology of tumor cell nuclei in gliomas has not been reported up to now. Therefore, the question must be answered, if there are any significant correlations between histomorphology of gliomas and quantitative data from 1HMRS concerning tissue metabolites. Surgical glioma specimen (glioblastomas, astrocytomas, oligodendrogliomas) from 46 patients with tumor grades II-IV according to WHO have been evaluated by means of a digital image analysis system using Ki-67-immunostained paraffin sections. Nuclear density, Ki-67-proliferation index, nuclear area and shape variables (roundness factor, Fourier-amplitudes) have been determined from 200 randomly selected tumor cell nuclei in each tumor specimen. These data have been correlated with preoperative data from 1HMRS. A positive correlation between Fourier-amplitudes, choline peak and lipide peak was observed, as well as a negative correlation between these variables and the nuclear roundness factor. This result indicates higher choline and lipide peaks with increasing irregularity of nuclear outlines. Proliferation index Ki-67 was positively correlated with the lipide peak, nuclear density showed a positive correlation with the choline peak. Glioblastomas (n = 29) showed an additional positive correlation between mean nuclear size and total creatine. Anaplastic gliomas (n = 12) showed a positive correlation between lactate peak and the standard deviation of the nuclear roundness factor. Further multivariate analyses have shown, that for the present collective of 46 cases, histometric variables have a higher significance than spectroscopic data for the differentiation of the different tumor grades. These results verify a significant correlation between preoperative data from 1HMRS and histomorphology of tumor cell nuclei in gliomas, supporting the biological significance of both histomorphometry and 1HMRS for the evaluation of these tumors.

Laser microdissection and pressure catapulting (LMPC) in paraffin sections mounted on glass slides. A methodological report.

The technique of laser microdissection together with laser pressure catapulting (LMPC) is demonstrated in paraffin sections obtained from surgical specimens of brain tumors mounted on glass slides. A sufficient and precise application of microdissection techniques in tissue on glass slides is worthwhile, since it offers the possibility of a retrospective analysis of archived paraffin sections in histopathology. We could demonstrate a precise dissection of areas in tissues of different thicknesses (4 microm and 20 microm). Areas of tissue mounted directly on glass need to be dissected in a scanning mode in order to remove the total region in form of small tissue fragments row by row. This mode provided a precise microdissection of tissue areas of different sizes and shapes. A successful molecular biological analysis of the microdissected regions could be demonstrated. As an example for such an analysis, differential-PCR for detecting an amplification of the gene for the epidermal growth factor receptor (EGFR) was performed.

Correlation between preoperative magnetic resonance spectroscopic data on high grade gliomas and morphology of Ki-67-positive tumor cell nuclei.

OBJECTIVE: To investigate possible statistical correlations between metabolic data from preoperative proton magnetic resonance spectroscopy (1HMRS) and morphology of proliferating tumor cell nuclei in anaplastic gliomas and glioblastomas. STUDY DESIGN: Ki-67-positive tumor cell nuclei in paraffin sections of surgical specimens from 36 patients (7 anaplastic gliomas, World Health Organization grade 3; 29 glioblastomas, World Health Organization grade 4) were investigated by means of a digital image analysis system. Stringent inclusion criteria were formulated for all cases with respect to histologic quality and spectroscopic examination. As morphometric variables, nuclear area, shape variables (roundness factor, size-invariate Fourier amplitudes) and density of Ki-67-positive tumor cell nuclei per reference area were determined. RESULTS: Correlation analysis according to Spearman revealed a significant positive correlation between the total creatine (TCR) peak and nuclear area (P = .005). This correlation was also found within the glioblastoma group (P = .019). There was also a significant negative correlation of nuclear area with the ratio between choline and TCR in all cases (P = .014) and within the glioblastoma group (P = .046). No significant correlation of spectroscopic data was found with nuclear shape or density of Ki-67-positive tumor cell nuclei. CONCLUSION: The results demonstrate a correlation between spectroscopic data and morphology of proliferating tumor cell nuclei (nuclear size) in high grade gliomas. This study is part of a detailed investigation of the interrelationship between preoperative 1HMRS and quantitative histomorphology of gliomas.

Topometric analysis of diffuse astrocytomas.

OBJECTIVE: To investigate differences between astrocytomas of WHO grade 2 and anaplastic astrocytomas of WHO grade 3 in terms of topometric variables characterizing individual tumor cell nuclei. STUDY DESIGN: Paraffin sections from surgical specimens from 25 astrocytomas (grade 2, n = 11; grade 3, n = 14) were analyzed by means of an image analysis system. At least 300 tumor cell nuclei were measured in the region with the highest Ki-67 proliferation index. Three different kinds of topometric variables were determined for each tumor cell nucleus: (1) several distances; (2) the variable Angle 2/1, the angle between the straight lines representing the distance to the nearest and second-nearest nucleus; and (3) the number of neighbors according to our mathematical definition. RESULTS: Most topometric variables showed distinct differences between the 2 tumor grades (multivariate analysis of variance), with 88% cases correctly reclassified by means of cross-validated discriminant analysis. The variables with the highest discriminatory power were the SD of Angle 2/1 and the ratio between the distance to the second-nearest and nearest tumor cell nucleus, with lower values for these variables in anaplastic astrocytomas. Even variables concerning neighborhood relationships showed significant differences. CONCLUSION: The results of this pilot study show that this first set of topometric variables is sufficient to detect differences between topologic characteristics of tumor cell nuclei in astrocytomas grade 2 and grade 3. Topometry seems to be an important tool for grading astrocytomas.