Brain tumour diagnostics using a DNA methylation-based classifier as a diagnostic support tool

AIMS

Methylation profiling (MP) is increasingly incorporated in the diagnostic process of central nervous system (CNS) tumours at our centres in The Netherlands and Scandinavia. We aimed to identify the benefits and challenges of MP as a support tool for CNS tumour diagnostics.

METHODS

About 502 CNS tumour samples were analysed using (850 k) MP. Profiles were matched with the DKFZ/Heidelberg CNS Tumour Classifier. For each case, the final pathological diagnosis was compared to the diagnosis before MP.

RESULTS

In 54.4% (273/502) of all analysed cases, the suggested methylation class (calibrated score ≥0.9) corresponded with the initial pathological diagnosis. The diagnosis of 24.5% of these cases (67/273) was more refined after incorporation of the MP result. In 9.8% of cases (49/502), the MP result led to a new diagnosis, resulting in an altered WHO grade in 71.4% of these cases (35/49). In 1% of cases (5/502), the suggested class based on MP was initially disregarded/interpreted as misleading, but in retrospect, the MP result predicted the right diagnosis for three of these cases. In six cases, the suggested class was interpreted as 'discrepant but noncontributory'. The remaining 33.7% of cases (169/502) had a calibrated score <0.9, including 7.8% (39/502) for which no class indication was given at all (calibrated score <0.3).

CONCLUSIONS

MP is a powerful tool to confirm and fine-tune the pathological diagnosis of CNS tumours, and to avoid misdiagnoses. However, it is crucial to interpret the results in the context of clinical, radiological, histopathological and other molecular information.

The histopathological spectrum of malignant hyperthermia and rhabdomyolysis due to RYR1 mutations

Objective

The histopathological features of malignant hyperthermia (MH) and non-anaesthetic (mostly exertional) rhabdomyolysis (RM) due to RYR1 mutations have only been reported in a few cases.

Methods

We performed a retrospective multi-centre cohort study focussing on the histopathological features of patients with MH or RM due to RYR1 mutations (1987–2017). All muscle biopsies were reviewed by a neuromuscular pathologist. Additional morphometric and electron microscopic analysis were performed where possible.

Results

Through the six participating centres we identified 50 patients from 46 families, including patients with MH (n = 31) and RM (n = 19). Overall, the biopsy of 90% of patients showed one or more myopathic features including: increased fibre size variability (n = 44), increase in the number of fibres with internal nuclei (n = 30), and type I fibre predominance (n = 13). Abnormalities on oxidative staining, generally considered to be more specifically associated with RYR1-related congenital myopathies, were observed in 52%, and included unevenness (n = 24), central cores (n = 7) and multi-minicores (n = 3). Apart from oxidative staining abnormalities more frequently observed in MH patients, the histopathological spectrum was similar between the two groups. There was no correlation between the presence of cores and the occurrence of clinically detectable weakness or presence of (likely) pathogenic variants.

Conclusions

Patients with RYR1-related MH and RM exhibit a similar histopathological spectrum, ranging from mild myopathic changes to cores and other features typical of RYR1-related congenital myopathies. Suggestive histopathological features may support RYR1 involvement, also in cases where the in vitro contracture test is not informative.

Electronic supplementary material

The online version of this article (10.1007/s00415-019-09209-z) contains supplementary material, which is available to authorized users.

RYR1-related myopathies: a wide spectrum of phenotypes throughout life

BACKGROUND AND PURPOSE

Although several recent studies have implicated RYR1 mutations as a common cause of various myopathies and the malignant hyperthermia susceptibility (MHS) trait, many of these studies have been limited to certain age groups, confined geographical regions or specific conditions. The aim of the present study was to investigate the full spectrum of RYR1-related disorders throughout life and to use this knowledge to increase vigilance concerning malignant hyperthermia.

METHODS

A retrospective cohort study was performed on the clinical, genetic and histopathological features of all paediatric and adult patients in whom an RYR1 mutation was detected in a national referral centre for both malignant hyperthermia and inherited myopathies (2008-2012).

RESULTS

The cohort of 77 non-related patients (detection rate 28%) included both congenital myopathies with permanent weakness and 'induced' myopathies such as MHS and non-anaesthesia-related episodes of rhabdomyolysis or hyperCKemia, manifested throughout life and triggered by various stimuli. Sixty-one different mutations were detected, of which 24 were novel. Some mutations are present in both dominant (MHS) and recessive modes (congenital myopathy) of inheritance, even within families. Histopathological features included an equally wide spectrum, ranging from only subtle abnormalities to prominent cores.

CONCLUSIONS

This broad range of RYR1-related disorders often presents to the general paediatric and adult neurologist. Its recognition is essential for genetic counselling and improving patients' safety during anaesthesia. Future research should focus on in vitro testing by the in vitro contracture test and functional characterization of the large number of RYR1 variants whose precise effects currently remain uncertain.

Adrenal nodularity and somatic mutations in primary aldosteronism: one node is the culprit?

CONTEXT

Somatic mutations in genes that influence cell entry of calcium have been identified in aldosterone-producing adenomas (APAs) of adrenal cortex in primary aldosteronism (PA). Many adrenal glands removed for suspicion of APA do not contain a single adenoma but nodular hyperplasia.

OBJECTIVE

The objective of the study was to assess multinodularity and phenotypic and genotypic characteristics of adrenals removed because of the suspicion of APAs.

DESIGN AND METHODS

We assessed the adrenals of 53 PA patients for histopathological characteristics and immunohistochemistry for aldosterone (P450C18) and cortisol (P450C11) synthesis and for KCNJ5, ATP1A1, ATP2B3, and CACNA1D mutations in microdissected nodi.

RESULTS

Glands contained a solitary adenoma in 43% and nodular hyperplasia in 53% of cases. Most adrenal glands contained only one nodule positive for P450C18 expression, with all other nodules negative. KCNJ5 mutations were present in 22 of 53 adrenals (13 adenoma and nine multinodular adrenals). An ATP1A1 and a CACNA1D mutation were found in one multinodular gland each and an ATP2B3 mutation in five APA-containing glands. Mutations were always located in the P450C18-positive nodule. In one gland two nodules containing two different KCNJ5 mutations were present. Zona fasciculata-like cells were more typical for KCNJ5 mutation-containing nodules and zona glomerulosa-like cells for the other three genes.

CONCLUSIONS

Somatic mutations in KCNJ5, ATP1A1, or CACNA1D genes are not limited to APAs but are also found in the more frequent multinodular adrenals. In multinodular glands, only one nodule harbors a mutation. This suggests that the occurrence of a mutation and nodule formation are independent processes. The implications for clinical management remain to be determined.

Micronodular transformation as a novel mechanism of VEGF-A-induced metastasis

How and why tumors metastasize is still a matter of debate. The assumption is that mutations render tumor cells with a metastatic phenotype, enabling entrance in and transport through lymph or blood vessels. Distant outgrowth is thought to occur only in a suitable microenvironment (the seed and soil hypothesis). However, the anatomical location of most metastases in cancer patients suggests entrapment of tumor cells in the first microcapillary bed that is encountered. We here investigated how vascular endothelial growth factor-A (VEGF-A) attributes to the metastatic process. We describe here that VEGF-A enhances spontaneous metastasis by inducing intravasation of heterogeneous tumor cell clusters, surrounded by vessel wall elements, via an invasion-independent mechanism. These tumor clusters generate metastatic tissue embolisms in pulmonary arteries. Treatment of tumor-bearing mice with the antiangiogenic compound ZD6474 prevented the development of this metastatic phenotype. This work shows that tumors with high constitutive VEGF-A expression metastasize via the formation of tumor emboli and provides an alternative rationale for anti-VEGF-A therapy, namely to inhibit metastasis formation.

Development of luciferase tagged brain tumour models in mice for chemotherapy intervention studies

The blood-brain barrier (BBB) is considered one of the major causes for the low efficacy of cytotoxic compounds against primary brain tumours. The aim of this study was to develop intracranial tumour models in mice featuring intact or locally disrupted BBB properties, which can be used in testing chemotherapy against brain tumours. These tumours were established by intracranial injection of suspensions of different tumour cell lines. All cell lines had been transfected with luciferase to allow non-invasive imaging of tumour development using a super-cooled CCD-camera. Following their implantation, tumours developed which displayed the infiltrative, invasive or expansive growth patterns that are also found in primary brain cancer or brain metastases. Contrast-enhanced magnetic resonance imaging showed that the Mel57, K1735Br2 and RG-2 lesions grow without disruption of the BBB, whereas the BBB was leaky in the U87MG and VEGF-A-transfected Mel57 lesions. This was confirmed by immunohistochemistry. Bioluminescence measurements allowed the visualisation of tumour burden already within 4 days after injection of the tumour cells. The applicability of our models for performing efficacy studies was demonstrated in an experiment using temozolomide as study drug. In conclusion, we have developed experimental brain tumour models with partly disrupted, or completely intact BBB properties. In vivo imaging by luciferase allows convenient follow-up of tumour growth and these models will be useful for chemotherapeutic intervention studies.

The pattern of metastasis of human melanoma to the central nervous system is not influenced by integrin alpha(v)beta(3) expression

We investigated the effect of integrin alpha(v)beta(3) expression on the metastatic pattern of human melanoma cells in the central nervous system (CNS). For this purpose, we developed a hematogenous CNS melanoma metastasis model in nude mice using a modified internal carotid artery infusion technique. This protocol revealed 2 different patterns of CNS metastasis. The integrin alpha(v)beta(3)-expressing melanoma lines Mel57 and Zkr nearly exclusively produced metastases in the brain parenchyma, whereas cells of the BLM and MV3 lines, devoid of integrin alpha(v)beta(3) expression, preferentially metastasized to dura mater and leptomeninges. Treatment with hyaluronidase to obtain single BLM cell suspensions did not influence the metastatic pattern, indicating that this was not simply the result of entrapment of tumor cell aggregates in large-sized leptomeningeal vessels. The role of integrin alpha(v)beta(3) expression in the process of metastasis was tested by transfection of BLM, but did not lead to an altered pattern of metastasis. We did observe, however, slower growth of the transfected tumors, although the in vitro growth rate was unaltered, indicating a reduction in tumorigenicity. We conclude from our findings that CNS metastasis of melanoma cells in the mouse xenograft model occurs in at least 2 different but very reproducible patterns. Although it is predicted that adhesion of tumor cells to endothelial cells plays a role in this phenomenon, tumor cell integrin alpha(v)beta(3) expression per se does not explain the difference in metastatic behavior in the CNS. We assume that other, as yet unknown factors, must be involved.

Endothelial protease-activated receptor-2 induces tissue factor expression and von Willebrand factor release

A second protease-activated receptor (PAR-2) that could be activated by trypsin or more physiologically by mast cell tryptase has been recently cloned. Both the structure and activation mechanism of PAR-2 was similar to the functional thrombin receptor (PAR-1). Although many effects of the coagulation protease thrombin on the vascular endothelium could be attributed to PAR-1 activation, very little is known about the physiological and pathophysiological role of PAR-2. We investigated whether stimulation of PAR-2 on endothelial cells induced two cellular responses that play a central role in primary and secondary haemostasis: the release of high molecular weight von Willebrand factor (hmw-VWF) from Weibel-Palade bodies and the de novo synthesis of tissue factor (TF) mRNA and protein. Human umbilical vein endothelial cells (HUVEC) were incubated with agonists for PAR-2 at 37 degrees C. Both trypsin and SLIGKV increased TF mRNA and activity and induced the release of hmw-VWF due to elevated levels of cytosolic Ca2+. Trypsin (10 nm) induced a 6-fold increase of TF mRNA and reduced time until fibrin clot formation to 37%, indicating trebling of the cell surface located TF activity. Stimulation of HUVEC with the PAR-2 agonist peptide SLIGKV induced a dose-dependent increase of TF mRNA up to 6 times and TF activity up to 3 times. Release of hmw-VWF was achieved both after incubation of HUVEC with trypsin and SLIGKV and was directly depending on intracellular Ca2+ mobilization. To make results comparable to the functional thrombin receptor, homologous experiments were carried out using the PAR-1 agonists thrombin and SFLLRN.

Trypsin induced von Willebrand factor release from human endothelial cells in mediated by PAR-2 activation

Nystedt and co-workers cloned in 1994 a second protease activatable receptor (PAR-2) that could be activated by trypsin but not by thrombin (1). In this study, we investigated whether trypsin induced stimulation of endothelial cells is linked to PAR-2 activation. We have found by mRNA analysis that endothelial cells of venous and arterial origin express both protease activatable receptors. The functional thrombin receptor and the protease activated receptor-2 (PAR-2) mediate apparently the same effects in human vascular endothelial cells. Both, the activation of the thrombin receptor with thrombin or SFLLRN and the activation of the PAR-2 with trypsin or SLIGRL induced intracellular calcium mobilisation and a subsequent release of von Willebrand factor (vWf) from Weibel-Palade bodies. As a consequence, it can be concluded that endothelial cells have two different receptors mediating the same cellular responses after activation.

The tethered ligand receptor is the responsible receptor for the thrombin induced release of von Willebrand factor from endothelial cells (HUVEC)

The present study was undertaken to define clearly the receptor, which is responsible for the thrombin induced vWf release from HUVEC. Vu et al. reported that cleavage of the platelet thrombin receptor by thrombin resulted in a new N-terminus (SFLLRN...) which acts as tethered ligand (4). The free peptide activates platelets and induces rises in both cytosolic free Ca2+ and PGI2 production in HUVEC (10). HUVEC were incubated with thrombin, SFLLRN or other relevant substances. After incubation, the intracellular vWf content was compared with the vWf concentration in the supernatant. The intracellular vWf concentration was measured by microscope fluorometry and the concentrations in the supernatant with an ELISA. The thrombin stimulated cells showed 53% vWf antigen compared with control cells (100%). This result was well correlated with the 2.4 fold higher vWf concentrations measured in the supernatant of thrombin stimulated cells than in control cells. Also the addition of SFLLRN (1-60 microM) or trypsin (1-50 nM) increased vWf release from HUVEC in a dose dependent manner. These results indicate that thrombin induced vWf release from HUVEC is mediated through the activation of the tethered ligand receptor.

[Epidermal growth factor receptor (EGF-R) in human breast cancer--a marker of morphologic-functional differentiation]

Epidermal growth factor and some related mitogens elicit a biological response in normal and malignant cells by mediation of a specific receptor, the epidermal growth factor receptor (EGF-R). In recent publications the expression of this receptor, a glycoprotein with extensive sequence homology to the erb B-oncogene, has in human breast carcinoma, been claimed to be an excellent indicator of a poor prognosis, superior to conventional prognostic factors such as nodal status and tumour size. To learn about the functional and prognostic role of EGF-R in breast carcinoma, we screened breast cancer tissue from 91 patients for the expression of the receptor by immunohistochemical means, with a monoclonal antibody. The results were compared to the expression of steroid receptors and to morphological and clinical parameters. We detected EGF-R in normal squamous cells of the skin and in epithelial and myoepithelial cells in non-neoplastic lobuli and ducts of the human breast. EGF-R was found in breast cancer tissues of 22 of the 91 patients. Specific staining was observed mainly in the cell membranes, but also to some extent in the cytoplasm. The distribution pattern of the antigen in terms of intensity of staining and number of specifically stained cells varied widely among different and within different regions of the same tumours.(ABSTRACT TRUNCATED AT 250 WORDS)