MGMT promoter methylation is not correlated with integrin expression in malignant gliomas: clarifying recent clinical trial results

Integrin alpha-v-beta-3 (α_vβ₃) is important for invasive tumor growth and angiogenesis in glioblastomas (GBM). However, recent clinical trials on inhibition of this integrin led to ambiguous results whether patients with methylated or unmethylated ⁶O-methylguanine methyltransferase (MGMT) promoter might profit from this kind of therapy. Therefore, we addressed the still unanswered question about a possible correlation between integrin α_vβ₃ expression and MGMT promoter methylation in GBM. For this purpose, tumor samples from newly diagnosed and untreated GBM patients with methylated (n = 22) or unmethylated (n = 17) MGMT promoter were simultaneously analyzed for integrin α_vβ₃ expression by an automated immunohistochemical staining platform. Interestingly, subsequent semi-quantitative analysis by a special imaging software did not show any difference in integrin expression between patients with methylated or unmethylated MGMT promoter status. Moreover, further analysis of the integrin subunits via ELISA from histologic sections revealed that there is no difference in integrin subunit expression between these patients. Hence, our results are important for designing future clinical trials with respect to treatment stratification, while it still has to be identified which other molecular factors determine differential responses to targeted anti-integrin α_vβ₃ treatment.

Substitutions of PrP N-terminal histidine residues modulate scrapie disease pathogenesis and incubation time in transgenic mice

Prion diseases have been linked to impaired copper homeostasis and copper induced-oxidative damage to the brain. Divalent metal ions, such as Cu2+ and Zn2+, bind to cellular prion protein (PrPC) at octapeptide repeat (OR) and non-OR sites within the N-terminal half of the protein but information on the impact of such binding on conversion to the misfolded isoform often derives from studies using either OR and non-OR peptides or bacterially-expressed recombinant PrP. Here we created new transgenic mouse lines expressing PrP with disrupted copper binding sites within all four histidine-containing OR's (sites 1-4, H60G, H68G, H76G, H84G, "TetraH>G" allele) or at site 5 (composed of residues His-95 and His-110; "H95G" allele) and monitored the formation of misfolded PrP in vivo. Novel transgenic mice expressing PrP(TetraH>G) at levels comparable to wild-type (wt) controls were susceptible to mouse-adapted scrapie strain RML but showed significantly prolonged incubation times. In contrast, amino acid replacement at residue 95 accelerated disease progression in corresponding PrP(H95G) mice. Neuropathological lesions in terminally ill transgenic mice were similar to scrapie-infected wt controls, but less severe. The pattern of PrPSc deposition, however, was not synaptic as seen in wt animals, but instead dense globular plaque-like accumulations of PrPSc in TgPrP(TetraH>G) mice and diffuse PrPSc deposition in (TgPrP(H95G) mice), were observed throughout all brain sections. We conclude that OR and site 5 histidine substitutions have divergent phenotypic impacts and that cis interactions between the OR region and the site 5 region modulate pathogenic outcomes by affecting the PrP globular domain.

Overexpression of cytosolic, plasma membrane bound and extracellular heat shock protein 70 (Hsp70) in primary glioblastomas

A unique feature in several non-CNS-tumors is the overexpression of heat shock protein 70 (Hsp70, HSPA1A) in the cytosol, but also its unusual plasma membrane expression and release. Although in gliomas, cytosolic Hsp70 levels are not associated with histological grading, the role of membrane bound and released Hsp70 is still completely unknown. Membrane bound as well as cytosolic Hsp70 can be detected in viable tumor cells with the monoclonal antibody (mAb) cmHsp70.1. Herein, we analysed membrane bound Hsp70 levels in primary and secondary gliomas of different grades and on isolated glioma subpopulations (endothelial cells, CD133-positive cells, primary cultures) by immunohistochemistry and flow cytometry using cmHsp70.1 mAb. Extracellular Hsp70 was determined by a commercial Hsp70 sandwich ELISA (R&D) in plasma samples of glioblastoma patients and healthy volunteers. We found an overexpression of Hsp70 in primary glioblastomas compared to low-grade, anaplastic, or secondary gliomas as determined by immunohistochemistry. Especially in flow cytometry, a strong plasma membrane Hsp70 expression was only observed in primary but not secondary glioblastomas. Within the heterogeneous tumor mass, CD133-positive tumor-initiating and primary glioblastoma cells showed a high membrane Hsp70 expression density, whereas endothelial cells, isolated from glioblastoma tissues only showed a weak staining pattern. Also in plasma samples, secreted Hsp70 protein was significantly increased in patients harbouring primary glioblastomas compared to those with secondary and low grade glioblastomas. Taken together, we show for the first time that cytosolic, membrane bound and extracellular Hsp70 is uniquely overexpressed in primary glioblastomas.

Quantifying prion disease penetrance using large population control cohorts

More than 100,000 genetic variants are reported to cause Mendelian disease in humans, but the penetrance-the probability that a carrier of the purported disease-causing genotype will indeed develop the disease-is generally unknown. We assess the impact of variants in the prion protein gene (PRNP) on the risk of prion disease by analyzing 16,025 prion disease cases, 60,706 population control exomes, and 531,575 individuals genotyped by 23andMe Inc. We show that missense variants in PRNP previously reported to be pathogenic are at least 30 times more common in the population than expected on the basis of genetic prion disease prevalence. Although some of this excess can be attributed to benign variants falsely assigned as pathogenic, other variants have genuine effects on disease susceptibility but confer lifetime risks ranging from <0.1 to ~100%. We also show that truncating variants in PRNP have position-dependent effects, with true loss-of-function alleles found in healthy older individuals, a finding that supports the safety of therapeutic suppression of prion protein expression.

Prognostic significance of dynamic 18F-FET PET in newly diagnosed astrocytic high-grade glioma

Despite advances in diagnosis and the use of different therapeutic regimens in astrocytic high-grade glioma (HGG), the prognosis for patients remains grim. Additional pretherapeutic information is needed to tailor management. To gain additional prognostic information at primary diagnosis, we investigated the value of dynamic O-(2-(18)F-fluoroethyl)-L-tyrosine ((18)F-FET) PET.

METHODS

We retrospectively evaluated 121 patients who had a primary diagnosis of astrocytic HGG (51 World Health Organization [WHO] grade III; 70 WHO IV) and underwent dynamic (18)F-FET PET before histopathologic assessment. We assessed static parameters (maximal and mean tumoral standardized uptake value corrected for mean background activity in the contralateral hemisphere [SUV(max)/BG and SUV(mean)/BG, respectively], biologic tumor volume) and dynamic time-activity curves, including minimal time to peak (TTP(min)). The prognostic influence of PET parameters and other clinical parameters on progression-free and overall survival was evaluated using uni- and multivariate Cox regression and Kaplan-Meier survival estimates.

RESULTS

In the group overall, median progression-free survival and overall survival were 12.2 and 21.9 mo. SUV(max)/BG, SUV(mean)/BG, and biologic tumor volume were significantly higher in WHO IV than in WHO III gliomas; median TTP(min) was 12.5 min in both groups. On univariate analysis, the factors age, WHO grade, O6-methylguanine-DNA methyltransferase promoter methylation status, contrast enhancement, initial treatment, and TTP(min) showed prognostic significance, with WHO grade, O6-methylguanine-DNA methyltransferase status, age, and TTP(min) remaining significant in the multivariate analysis. WHO grade and TTP(min) reached a similar fit for the prognostic evaluation. The prognosis of WHO III astrocytoma with an early TTP(min) of 12.5 min or less did not differ significantly from that of glioblastoma.

CONCLUSION

Early TTP(min) is associated with worse outcome in patients with newly diagnosed astrocytic HGG. In the preoperative setting, TTP(min) can be a valuable noninvasive prognostic marker with comparable significance to WHO grade. Additionally, TTP(min) can help identify highly aggressive WHO III astrocytoma tumors and may help in adjusting standard treatment toward an individualized, risk-adapted therapy regime.

Dynamic 18F-FET PET in suspected WHO grade II gliomas defines distinct biological subgroups with different clinical courses

In suspected grade II gliomas, three distinct patterns of time-activity curves (TAC) on O-(2-[(18)F]fluoroethyl)-1-tyrosine ((18)F-FET) positron emission tomography (PET) have been delineated (i) increasing TAC homogeneously throughout the tumor, and decreasing TAC, (ii) either homogeneously throughout the tumor or (iii) only focally within otherwise increasing TAC patterns. Increasing TAC was associated with low-grade histology and decreasing TAC with high-grade histology. This prospective study analyzed whether these patterns correlate with distinct biological tumor subtypes and differential outcome. (18)F-FET PET-guided biopsies were used for stepwise histopathological evaluation. Molecular-genetic evaluation included O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation, isocitrate dehydrogenase (IDH1/2) mutational and 1p/19q codeletion status. Progression-free survival (PFS) was estimated with the Kaplan-Meier method. Prognostic factors were obtained from multivariate regression models. 98 adult patients were included. Homogeneous increasing, focal decreasing and homogeneous decreasing TAC were seen in 51, 19 and 28 patients. The corresponding 1-year (2-years) PFS were 92% (85%), 89% (51%) and 50% (28%; p = 0.002). IDH1/2 mutations were more frequent in tumors with homogeneous increasing (90%) and focal decreasing (79%) TAC, but were rare in those exhibiting homogeneous decreasing TAC (25%; p < 0.001). Overall, TAC patterns, IDH1/2 mutational and 1p/19q codeletion status were powerful and independent prognostic factors. Dynamic (18)F-FET PET might be an important and independent imaging biomarker for patients with suspected WHO grade II gliomas and offers perspectives for stratified diagnostic and therapeutic strategies. Tumors with focal decreasing TAC need highly targeted surgical interventions to avoid undergrading and undertreatment.

Molecular stereotactic biopsy technique improves diagnostic accuracy and enables personalized treatment strategies in glioma patients

BACKGROUND

In gliomas molecular biomarkers are increasingly gaining diagnostic, prognostic and predictive significance. Determination of biomarker status after biopsy is important as not all patients are eligible for open tumor resection. We developed and validated prospectively (6/10-12/11) a protocol allowing for both reliable determination of multiple biomarkers and representative histological diagnoses from small-sized biopsies.

METHODS

All molecular stereotactic biopsies were performed according to a detailed workflow. The selection of specimens best suited for molecular analyses was intra-operatively guided by the attending neuropathologist. Postoperative screening was done by methylation specific PCR using two distinct cryopreserved specimens to test for reproducibility of the findings and to rule out contamination. The DNA of a single best-suited specimen (1 mm(3)) was subjected to detailed molecular analysis (MGMT promoter methylation, IDH1/2 mutational status, LOH 1p and/or 19q).

RESULTS

159 consecutively enrolled untreated gliomas were analyzed (94 glioblastomas, 2 gliosarcomas, 24 anaplastic astrocytomas, 10 oligo-tumors grade II/III, 20 grade II astrocytomas and 9 pilocytic astrocytomas). Transient morbidity was 2 %. Overall, the drop-out rate due to tissue contamination was 0.4 %. Median time from biopsy to histological and molecular genetic analyses was 3 and 5 days, respectively. Distributions of the respective biomarker status for tumor subgroups were consistent with the literature. The final histological diagnosis was changed/modified in 5/159 patients according to molecular findings. Treatment after molecular biopsy was highly personalized.

CONCLUSIONS

Molecular stereotactic biopsy is feasible and safe, can be implemented in daily clinical practice, improves diagnostic precision and enables personalized treatment.

Male sex as a risk factor for the clinical course of skull base chordomas

Object

Chordomas of the skull base are rare and locally invasive and have a poor prognosis. The aim of this retrospective multicenter study was to evaluate the current pattern of care and clinical course and to identify prognostic factors.

Methods

A total of 47 patients (26 men; mean age 48.5 years) treated in 5 centers were included. Histology was centrally reviewed; additionally, semiquantitative N- and E-cadherin expression analysis was performed. Prognostic factors were obtained from multivariate regression models. For survival analysis the Kaplan-Meier method was used.

Results

The median follow-up period was 5.2 years. Complete resection, incomplete resection, and extended biopsy were performed in 14.9%, 80.9%, and 4.3% of patients, respectively. Surgical morbidity was not associated with extent of resection. Adjuvant radiation therapy was performed in 30 (63.8%) of 47 patients. The median progression-free survival (PFS) was 7.3 years. Complete resection prolonged median overall survival (OS) (p = 0.04). Male patients presented with worse PFS (4.8 years vs 9.8 years; p = 0.04) and OS (8.3 years vs not reached; p = 0.03) even though complete resection was exclusively achieved in the male subpopulation. Multivariate analysis confirmed male sex as the most important risk factor for tumor progression (p = 0.04) and death (p = 0.02). Age, duration of symptoms, initial Karnofsky Performance Scale score, brainstem compression, involvement of the petrous bone, infiltration of the dura mater, modality and dose of radiation therapy, and the E- and N-cadherin expression patterns did not gain prognostic relevance.

Conclusions

In skull base chordomas, male patients bear a higher risk of progressive disease and death. Male patients might benefit from more aggressive adjuvant therapy and/or from a closer follow-up schedule.

Dynamic 18F-FET PET in newly diagnosed astrocytic low-grade glioma identifies high-risk patients

Because the clinical course of low-grade gliomas in the individual adult patient varies considerably and is unpredictable, we investigated the prognostic value of dynamic (18)F-fluorethyltyrosine ((18)F-FET) PET in the early diagnosis of astrocytic low-grade glioma (World Health Organization grade II).

METHODS

Fifty-nine patients with newly diagnosed low-grade glioma and dynamic (18)F-FET PET before histopathologic assessment were retrospectively investigated. (18)F-FET PET analysis comprised a qualitative visual classification of lesions; assessment of the semiquantitative parameters maximal, mean, and total standardized uptake value as ratio to background and biologic tumor volume; and dynamic analysis of intratumoral (18)F-FET uptake over time (increasing vs. decreasing time-activity curves). The correlation between PET parameters and progression-free survival, overall survival, and time to malignant transformation was investigated.

RESULTS

(18)F-FET uptake greater than the background level was found in 34 of 59 tumors. Dynamic (18)F-FET uptake analysis was available for 30 of these 34 patients. Increasing and decreasing time-activity curves were found in 18 and 12 patients, respectively. Neither the qualitative factor presence or absence of (18)F-FET uptake nor any of the semiquantitative uptake parameters significantly influenced clinical outcome. In contrast, decreasing time-activity curves in the kinetic analysis were highly prognostic for shorter progression-free survival and time to malignant transformation (P < 0.001).

CONCLUSION

Absence of (18)F-FET uptake in newly diagnosed astrocytic low-grade glioma does not generally indicate an indolent disease course. Among the (18)F-FET-positive gliomas, decreasing time-activity curves in dynamic (18)F-FET PET constitute an unfavorable prognostic factor in astrocytic low-grade glioma and, by identifying high-risk patients, may ease treatment decisions.

Report about four novel mutations in the prion protein gene

BACKGROUND/AIMS

Since detection of the prion protein gene (PRNP) more than 30 mutations have been discovered. Some have only been found in single case reports without known intrafamilial accumulation or neuropathological proof so that the causal connection between mutation and disease could not be proved. Those patients often present atypical clinical phenotypes, and it is not unusual that they are classified as diseases other than Creutzfeldt-Jakob disease (CJD).

METHODS

Cases of suspected CJD have been reported to the national reference center for prion diseases. Clinical and diagnostic data were collected, and a classification of definite, possible or probable prion disease was made. Molecular analysis of PRNP was performed by capillary sequencing.

RESULTS

We have described 4 cases with atypical clinical and diagnostic findings and unknown mutations in PRNP so far.

CONCLUSION

Three patients fulfilled the criteria of probable CJD, and 1 patient fulfilled the criteria of possible CJD but the clinical picture in none of the patients was typical CJD; hence, it remained questionable whether the mutations were causal of the disease.

[18F]fluoroethyltyrosine-positron emission tomography-based therapy monitoring after stereotactic iodine-125 brachytherapy in patients with recurrent high-grade glioma

Therapy monitoring of glioma after stereotactic iodine-125 brachytherapy (SBT) remains challenging because posttherapeutic changes in magnetic resonance imaging can mimic tumor progression. We evaluated the prognostic value of serial [18F]fluoroethyltyrosine (FET)-positron emission tomographic (PET) scans for therapy monitoring of high-grade glioma (HGG) after SBT. Thirty-three patients with recurrent HGG were included. Serial FET-PET scans were performed prior to therapeutic intervention and at 3-month intervals during the first year after SBT. FET-PET evaluation was performed by both conventional data analysis and kinetic analysis. Prognostic factors were obtained from proportional hazard models. Median local progression-free survival (LPFS) was 11.1 months. Maximal standardized background uptake value (SUVmax/BG) and biologic tumor volume (BTV) differentiated accurately between therapeutic effects and local tumor progression at the 6-month and subsequent examinations. Increasing uptake kinetics at baseline (p < .05) and during follow-up (p < .01) were stringently associated with a longer LPFS. Early increase in FET uptake after SBT is not unequivocally associated with tumor progression; it might be induced by reactive changes and could easily lead to a misclassification of the tumor status (pseudoprogression). Six months after SBT (or later), however, increased SUVmax/BG and BTV values are associated with a worse prognosis. Multivariate analysis stresses the prognostic importance of dynamic studies.

Optical needle endoscope for safe and precise stereotactically guided biopsy sampling in neurosurgery

Proper treatment of deep seated brain tumors requires correct histological diagnosis which unambiguously necessitates biopsy sampling. Stereotactically guided sampling of biopsies is widely used but bears the danger of incorrect sampling locations and damage to intracerebral blood vessels. Here, we present a minimally invasive contact endoscopic probe that can be inserted into the tissue inside a standard biopsy needle and allows for fluorescence detection of both tumorous tissue and intracerebral blood vessels. Outer diameter of our contact probe is smaller than 1.5 mm, field-of-view in the range of several hundred microns; the optical design allows for simultaneous detection and visualization of tissue autofluorescence and selective fluorescence signals from deep seated brain tumors and vasculature as shown on in vivo animal models. We demonstrate the tumor detection capability during stereotactic needle insertion in a clinical pilot trial. Using our probe, we expect stereotactic interventions to become safer and more precise and the technology might ultimately be used also for various other kinds of applications.

Isolation and characterization of bone marrow-derived progenitor cells from malignant gliomas

BACKGROUND

Malignant gliomas are highly-vascularised tumours. Neoangiogenesis is a crucial factor in the malignant behaviour of tumour and prognosis of patients. Several mechanisms are suspected to lead to neoangiogenesis, one of them is the recruitment of multipotent progenitor cells towards the tumour. Factors such as Vascular endothelial growth factor-A (VEGF-A) were described to recruit bone marrow-derived endothelial progenitor cells (EPCs) to the glioma stroma and vasculature. Little is known about isolating EPCs from normal or malignant tissues.

MATERIALS AND METHODS

In this study, we addressed the topic of characterization of tumour-isolated EPCs and re-defined the clonal relationship between EPCs and hematopoietic stem cells (HSCs) in gliomas. We first checked public gene expression data of glioma for putative marker expression, pointing towards a prevalence of EPCs and HSCs in glioma. Immunohistochemical staining of glioma tissue confirmed the higher expression of these progenitor markers in glioma tissue. EPCs and HSCs were consequently isolated and characterized at the phenotypic and functional levels. We applied a new isolation method, for the first time, to specimen from patients with high grade glioma including seven grade IV glioblastoma, five-grade III astrocytoma, and three grade III oligoastrocytoma.

RESULTS

In all samples, we were able to isolate the tumour-derived EPCs, which were positive for characteristic markers: CD31, CD34 and VEGFR2. The EPCs formed capillary networks in vitro and had the ability to take up acetylated low-density lipoprotein. Glioma-derived HSCs were positive for CD34 and CD45, but they were unable to form a capillary network in vitro. These findings on tumour-derived EPCs/HSCs were in concordance with the results, derived from peripheral blood of healthy volunteers.

CONCLUSION

In our study, we established a new method for EPC/HSC isolation from human gliomas, defined the contribution of EPCs and HSCs to the tumour tissue, and highlighted the intense in vivo tumour host interaction.

ALDH1A1 is a marker of astrocytic differentiation during brain development and correlates with better survival in glioblastoma patients

Glioblastoma is the most common malignant brain tumor and patients usually succumb to their disease within 2 years. Aldehyde dehydrogenase 1A1 (ALDH1A1) has been suggested as a marker for cancer stem cells that is associated with poor prognosis in human gliomas. However, little is known about the expression and the function of ALDH1A1 in early stages of brain development. We analyzed ALDH1A1 expression in developing and mature central nervous system (CNS) as well as in 93 cases of primary glioblastomas. Surprisingly, ALDH1A1 was absent in the stem cell niches at varying stages of CNS development, but strong ALDH1A1 expression was observed in mature astrocytes coexpressing GFAP and S100. There were 92 out of 93 glioblastomas (99%) that showed ALDH1A1 protein expression in up to 49% of tumor cells. The majority of these cells co-expressed GFAP, but not established stem cell markers such as Nestin, OLIG2 or SOX2. Finally, strong expression of ALDH1A1 correlated with a significantly better survival of the patients and proved to be an independent prognostic marker in our series (P < 0.01). In contrast to other published data, we therefore provide evidence for ALDH1A1 as a marker of astrocytic differentiation during brain development and of better prognosis in patients suffering from primary glioblastoma.

Prediction of oligodendroglial histology and LOH 1p/19q using dynamic [(18)F]FET-PET imaging in intracranial WHO grade II and III gliomas

Oligodendroglial components (OC) and loss of heterozygosity on chromosomes 1p and 19q (LOH 1p/19q) are associated with better outcome in patients with glioma. We aimed to assess the fitness of [(18)F]fluoroethyltyrosine positron-emission-tomography (FET-PET) for noninvasively identifying these important prognostic/predictive factors. One hundred forty-four patients with MRI-suspected WHO grade II and III glioma underwent FET-PET scans prior to histological diagnosis. FET-PET analyses included maximal tumoral uptake (SUV(max)/BG), biological tumor volume (BTV), mean tumoral uptake (SUV(mean)/BG), total tumoral uptake (SUV(total)/BG), and kinetic analysis. Suspicion of OC was based on static and dynamic FET-uptake parameters. PET results were correlated with histology and 1p/19q status. OC tumors exhibited significantly higher uptake values, compared with astrocytomas (AC) (SUV(max)/BG 3.1 vs 2.3, BTV 15.5 mL vs 7.2 mL, SUV(total)/BG 38.5 vs 17.4, P < .01 each; SUV(mean)/BG 2.2 vs 2.1, P < .05). These differences were more pronounced in WHO grade II gliomas. Comparable results were found with respect to 1p/19q status. Kinetic analysis misclassified 18 of 34 low-grade OC tumors as high-grade glioma but misclassified only 5 of 45 of the low-grade ACs. FET-based suspicion of OC resulted in concordance rates of both 76% for the prediction of OC and LOH 1p/19q. FET-uptake was significantly higher in gliomas with OC, compared with AC, and likewise in 1p/19q codeleted, compared with noncodeleted tumors. However, FET-PET analysis did not reliably predict the presence of OC/LOH 1p/19q in the individual patient, mostly because of an overlap in PET characteristics of OC tumors and high-grade AC. Histological examination is still required for an accurate diagnosis.

Extramedullary multiple myeloma presenting as a pituitary mass lesion

INTRODUCTION

A plasmocytoma involving the pituitary gland is an extremely rare entity, with approximately 22 cases of solitary myeloma or multiple myeloma presenting with sellar mass reported in the literature so far.

CASE REPORT

Here, we report the case of a 71-year-old female patient affected by an extramedullary IgG-lambda multiple myeloma presenting as a pituitary mass lesion. We summarize the diagnostic approaches that confirmed the diagnosis of multiple myeloma and describe treatment outcome after therapy.

DISCUSSION

Intrasellar plasmocytoma though rare, should be considered in the differential diagnosis of a pituitary mass lesion, since associated with different therapeutic and prognostic implications. Physicians should be alert for intrasellar plasma cell tumors in case of well preserved anterior pituitary function in combination with cranial nerve neuropathies and sellar destruction.

FET-PET assessed recurrence pattern after radio-chemotherapy in newly diagnosed patients with glioblastoma is influenced by MGMT methylation status

BACKGROUND AND PURPOSE

The aim of the present study was to evaluate factors predicting the recurrence pattern determined by [(18)F]FET-PET imaging in patients with newly diagnosed glioblastoma after combined radio-chemotherapy treated according to the EORTC/NCIC trial.

MATERIAL AND METHODS

Seventy-nine patients with newly diagnosed GBM treated with radiotherapy plus temozolomide (75 mg/m(2)/d) followed by adjuvant cyclic (5/28 days) temozolomide (150-200 mg/m(2)) were retrospectively analysed. Recurrence patterns were assessed by means of positron-emission-tomography with [(18)F]FET and additional MRI; in 54 patients MGMT methylation status was evaluated.

RESULTS

Whilst 49.4% of the patients had an in-field recurrence, 12.6% an ex-field recurrence and 3.8% a recurrence at the field margin, 34.2% of the patients did not relapse during follow-up (median 595 days). Considering all patients included in this study, 41.5% (12/29) of the MGMT methylated population had no relapse, 37.9% (11/29) had an in-field-recurrence and 20.7% (6/29) an ex-field/marginal recurrence, whilst 28.0% (7/25) of the MGMT unmethylated population had no relapse, 64.0% (16/25) had an in-field-recurrence and 8.0% (2/25) an ex-field/marginal recurrence (p=0.15).

CONCLUSIONS

After the administration of temozolomide concomitant with and adjuvant to radiotherapy in patients with glioblastoma, the pattern determined by [(18)F]FET-PET seems to be associated with MGMT methylation status.

Intramedullary pilomyxoid astrocytoma with intracerebral metastasis exhibiting oligoden-droglioma-like features

Intramedullary glioma are rare and their biological behaviour can differ from their cerebral counterparts. Pilomyxoid astrocytoma (PMA, WHO grade II), predominantly occur in the hypothalamic/chiasmatic region of infants and children. The few reported cases of pediatric intramedullary PMA displayed a particularly aggressive behavior. Here, we report a diagnostically challenging case of a five year old female patient presenting with intramedullary glioma and local tumor recurrence three years later. Twelve years after the initial manifestation, a second tumor was found intracerebrally. We performed a comprehensive histological, molecular pathological and imaging analysis of the tumors from both localizations. The results revealed a metastasizing PMA with unique histological and genetic features. Our study indicates that PMA comprise a heterogeneous group including aggressive subtypes which may not be compatible with the current classification according to WHO grade II. Furthermore, the case emphasizes the increasing relevance of molecular pathological markers complementing classic histo-logical diagnosis.

Low values of 5-hydroxymethylcytosine (5hmC), the "sixth base," are associated with anaplasia in human brain tumors

5-Methylcytosine (5 mC) in genomic DNA has important epigenetic functions in embryonic development and tumor biology. 5-Hydroxymethylcytosine (5 hmC) is generated from 5 mC by the action of the TET (Ten-Eleven-Translocation) enzymes and may be an intermediate to further oxidation and finally demethylation of 5 mC. We have used immunohistochemistry (IHC) and isotope-based liquid chromatography mass spectrometry (LC-MS) to investigate the presence and distribution of 5 hmC in human brain and brain tumors. In the normal adult brain, IHC identified 61.5% 5 hmC positive cells in the cortex and 32.4% 5 hmC in white matter (WM) areas. In tumors, positive staining of cells ranged from 1.1% in glioblastomas (GBMs) (WHO Grade IV) to 8.9% in Grade I gliomas (pilocytic astrocytomas). In the normal adult human brain, LC-MS also showed highest values in cortical areas (1.17% 5 hmC/dG [deoxyguanosine]), in the cerebral WM we measured around 0.70% 5 hmC/dG. levels were related to tumor differentiation, ranging from lowest values of 0.078% 5 hmC/dG in GBMs (WHO Grade IV) to 0.24% 5 hmC/dG in WHO Grade II diffuse astrocytomas. 5 hmC measurements were unrelated to 5 mC values. We find that the number of 5 hmC positive cells and the amount of 5 hmC/dG in the genome that has been proposed to be related to pluripotency and lineage commitment in embryonic stem cells is also associated with brain tumor differentiation and anaplasia.

MiRNA expression patterns predict survival in glioblastoma

Background

In order to define new prognostic subgroups in patients with glioblastoma a miRNA screen (> 1000 miRNAs) from paraffin tissues followed by a bio-mathematical analysis was performed.

Methods

35 glioblastoma patients treated between 7/2005 - 8/2008 at a single institution with surgery and postoperative radio(chemo)therapy were included in this retrospective analysis. For microarray analysis the febit biochip "Geniom^® Biochip MPEA homo-sapiens" was used. Total RNA was isolated from FFPE tissue sections and 1100 different miRNAs were analyzed.

Results

It was possible to define a distinct miRNA expression pattern allowing for a separation of distinct prognostic subgroups. The defined miRNA pattern was significantly associated with early death versus long-term survival (split at 450 days) (p = 0.01). The pattern and the prognostic power were both independent of the MGMT status.

Conclusions

At present, this is the first dataset defining a prognostic role of miRNA expression patterns in patients with glioblastoma. Having defined such a pattern, a prospective validation of this observation is required.

Promoter methylation and expression of MGMT and the DNA mismatch repair genes MLH1, MSH2, MSH6 and PMS2 in paired primary and recurrent glioblastomas

Epigenetic silencing of the O(6) -methylguanine-DNA methyltransferase (MGMT) gene promoter is associated with prolonged survival in glioblastoma patients treated with temozolomide (TMZ). We investigated whether glioblastoma recurrence is associated with changes in the promoter methylation status and the expression of MGMT and the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2 in pairs of primary and recurrent glioblastomas of 80 patients, including 64 patients treated with radiotherapy and TMZ after the first operation. Among the primary tumors, the MGMT promoter was methylated in 31 patients and unmethylated in 49 patients. In 71 patients (89%), the MGMT promoter methylation status of the primary tumor was retained at recurrence. MGMT promoter methylation, but not MGMT protein expression, was associated with longer progression-free survival, overall survival and postrecurrence survival (PRS). Moreover, PRS was increased under salvage chemotherapy. Investigation of primary and recurrent glioblastomas of 43 patients did not identify promoter methylation in any of the four MMR genes. However, recurrent glioblastomas demonstrated significantly lower MSH2, MSH6 and PMS2 protein expression as detected by immunohistochemistry. In conclusion, reduced expression of MMR proteins, but not changes in MGMT promoter methylation, is characteristic of glioblastomas recurring after the current standards of care.

IDH1 mutations in grade II astrocytomas are associated with unfavorable progression-free survival and prolonged postrecurrence survival

BACKGROUND

The favorable prognostic impact of mutations in the IDH1 gene is well documented for malignant gliomas; its influence on World Health Organization (WHO) grade II astrocytomas, however, is still under debate.

METHODS

A previously published database of 127 predominantly surgically treated patients harboring WHO grade II astrocytomas was revisited. Patients were screened for TP53 mutations (sequencing analysis), IDH1 mutations (pyrosequencing), and MGMT promoter methylation (methylation-specific polymerase chain reaction and bisulfite sequencing). Endpoints were overall survival, progression-free survival (PFS), time to malignant transformation, and postrecurrence survival. Radiotherapy was usually withheld until tumor progression/malignant transformation occurred.

RESULTS

IDH1 mutations, TP53 mutations, and methylated MGMT promoters were seen in 78.1%, 51.2%, and 80.0% of the analyzed tumors, respectively. IDH1 mutations, which were significantly associated with TP53 mutations and/or MGMT promoter methylation (P < .001), resulted in shortened PFS (median, 47 vs 84 months; P = .004); postrecurrence survival, however, was significantly increased in those patients undergoing malignant transformation (median, 49 vs 13.5 months; P = .006). Overall survival was not affected by IDH1. A similar pattern of influence was seen for MGMT promoter methylation. Methylated tumors did significantly worse (better) in terms of PFS (postrecurrence survival); a low number of unmethylated tumors, however, limited the power of this analysis. Conversely, TP53 mutations were stringently associated with a worse prognosis throughout the course of the disease.

CONCLUSIONS

IDH1 mutations are associated with a Janus headlike phenomenon; unfavorable prognostic influence on PFS turns into favorable impact on postrecurrence survival. A similar pattern of influence might exist for MGMT methylation.

Predominant influence of MGMT methylation in non-resectable glioblastoma after radiotherapy plus temozolomide

BACKGROUND

Patients with non-resectable glioblastoma generally exhibit a poor prognosis, even after radiotherapy plus concomitant and adjuvant temozolomide (XRT/TMZ→TMZ). Unfortunately, no data are available concerning the predictive value of O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation for this important subpopulation. For clarification, a prospective study was conducted.

METHODS

Adult patients with a non-resectable glioblastoma were included. A molecular stereotactic biopsy technique was used for tumour characterisation combining histopathological diagnosis with small sample size adjusted methylation-specific PCR (MSP) and sodium bisulfite sequencing. Treatment included XRT (60 Gy in 30 fractions)/TMZ (daily dose of 75 mg/m(2))→TMZ (150-200 mg/m(2) per day for 5 days of every 28-day cycle). The primary end point was progression-free survival (PFS). Secondary endpoints were overall survival (OS) and treatment response (TR). Patients were categorised in the Radiation Therapy Oncology Group (RTOG)-recursive partitioning analysis (RPA) Classes III (N=4), IV (N=12), V (N=28) and VI (N=12).

RESULTS AND DISCUSSION

The success rates of MSP and sequence analyses were 100%. The MGMT promoter was methylated in 30/56 tumours, which was associated with an increased PFS (median 56 versus 20 weeks; hazard ratio 0.15; range 0.07 to 0.33; p<0.0001), higher frequency of TR (93.3% vs 46.2%; p=0.0008) and increased OS (median 104 vs 28 weeks; hazard ratio 0.18; range 0.08 to 0.38; p<0.0001). The transient perioperative morbidity was 1.8%.

CONCLUSION

MGMT promoter methylation has a predominant favourable influence even for the important subpopulation with non-resectable glioblastoma. The molecular stereotactic biopsy technique is safe and effective for predictive evaluation and helps to avoid both over- and undertreatment.

O-methylguanine-DNA methyltransferase (MGMT) mRNA expression predicts outcome in malignant glioma independent of MGMT promoter methylation

BACKGROUND

We analyzed prospectively whether MGMT (O(6)-methylguanine-DNA methyltransferase) mRNA expression gains prognostic/predictive impact independent of MGMT promoter methylation in malignant glioma patients undergoing radiotherapy with concomitant and adjuvant temozolomide or temozolomide alone. As DNA-methyltransferases (DNMTs) are the enzymes responsible for setting up and maintaining DNA methylation patterns in eukaryotic cells, we analyzed further, whether MGMT promoter methylation is associated with upregulation of DNMT expression.

METHODOLOGY/PRINCIPAL FINDINGS

ADULT PATIENTS WITH A HISTOLOGICALLY PROVEN MALIGNANT ASTROCYTOMA (GLIOBLASTOMA: N = 53, anaplastic astrocytoma: N = 10) were included. MGMT promoter methylation was determined by methylation-specific PCR (MSP) and sequencing analysis. Expression of MGMT and DNMTs mRNA were analysed by real-time qPCR. Prognostic factors were obtained from proportional hazards models. Correlation between MGMT mRNA expression and MGMT methylation status was validated using data from the Cancer Genome Atlas (TCGA) database (N = 229 glioblastomas). Low MGMT mRNA expression was strongly predictive for prolonged time to progression, treatment response, and length of survival in univariate and multivariate models (p<0.0001); the degree of MGMT mRNA expression was highly correlated with the MGMT promoter methylation status (p<0.0001); however, discordant findings were seen in 12 glioblastoma patients: Patients with methylated tumors with high MGMT mRNA expression (N = 6) did significantly worse than those with low transcriptional activity (p<0.01). Conversely, unmethylated tumors with low MGMT mRNA expression (N = 6) did better than their counterparts. A nearly identical frequency of concordant and discordant findings was obtained by analyzing the TCGA database (p<0.0001). Expression of DNMT1 and DNMT3b was strongly upregulated in tumor tissue, but not correlated with MGMT promoter methylation and MGMT mRNA expression.

CONCLUSIONS/SIGNIFICANCE

MGMT mRNA expression plays a direct role for mediating tumor sensitivity to alkylating agents. Discordant findings indicate methylation-independent pathways of MGMT expression regulation. DNMT1 and DNMT3b are likely to be involved in CGI methylation. However, their exact role yet has to be defined.

Hot spots in dynamic (18)FET-PET delineate malignant tumor parts within suspected WHO grade II gliomas

Molecular imaging studies have recently found inter- and intratumoral heterogeneity in World Health Organization (WHO) grade II gliomas. A correlative analysis with tumor histology, however, is still lacking. For elucidation we conducted the current prospective study. Fifty-five adult patients with an MRI-based suspicion of a WHO grade II glioma were included. [F-18]Fluoroethyltyrosine ((18)FET) uptake kinetic studies were combined with frame-based stereotactic localization techniques and used as a guide for stepwise (1-mm steps) histopathological evaluation throughout the tumor space. In tumors with heterogeneous PET findings, the O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status and expression of mutated protein isocitrate dehydrogenase variant R132H (IDH1) were determined inside and outside of hot spot volumes. Metabolic imaging revealed 3 subgroups: the homogeneous WHO grade II glioma group (30 patients), the homogeneous malignant glioma group (10 patients), and the heterogeneous group exhibiting both low- and high-grade characteristics at different sites (15 patients). Stepwise evaluation of 373 biopsy samples indicated a strong correlation with analyses of uptake kinetics (p < 0.0001). A homogeneous pattern of uptake kinetics was linked to homogeneous histopathological findings, whereas a heterogeneous pattern was associated with histopathological heterogeneity; hot spots exhibiting malignant glioma characteristics covered 4-44% of the entire tumor volumes. Both MGMT and IDH1 status were identical at different tumor sites and not influenced by heterogeneity. Maps of (18)FET uptake kinetics strongly correlated with histopathology in suspected grade II gliomas. Anaplastic foci can be accurately identified, and this finding has implications for prognostic evaluation and treatment planning.

Genetic prion disease with codon 196 PRNP mutation: clinical and pathological findings

Ten percent to 15% of all human transmissible spongiform encephalopathy are characterized by a mutation in prion protein gene (PRNP). They are distinct with respect to clinical signs, disease onset, disease duration, and diagnostic findings. During our surveillance activities in Germany, we identified 7 patients with the rare mutation E196K in PRNP gene, thereof 4 patients belonging to 2 families. The clinical syndromes were characterized by nonspecific and psychiatric symptoms at disease onset and progressed to predominant motor signs. These patients showed a late median disease onset of 71 years and short disease duration of 6.5 months. In absence of family history, they mimicked sporadic Creutzfeldt-Jakob disease (CJD). In clinical tests they were 100% positive for 14-3-3 protein detection in cerebrospinal fluid and less sensitive for magnetic resonance imaging (MRI) and electroencephalogram (EEG) abnormalities. As a secondary magnetic resonance imaging (MRI) abnormality, we have seen conspicuous common involvement of the subcortical white matter in 57%. Four patients underwent autopsy-pathological lesions revealed striking similarity to sporadic Creutzfeldt-Jakob disease but also involvement of the white matter.

Lentivector-mediated RNAi efficiently suppresses prion protein and prolongs survival of scrapie-infected mice

Prion diseases are fatal neurodegenerative diseases characterized by the accumulation of PrP(Sc), the infectious and protease-resistant form of the cellular prion protein (PrP(C)). We generated lentivectors expressing PrP(C)-specific short hairpin RNAs (shRNAs) that efficiently silenced expression of the prion protein gene (Prnp) in primary neuronal cells. Treatment of scrapie-infected neuronal cells with these lentivectors resulted in an efficient and stable suppression of PrP(Sc) accumulation. After intracranial injection, lentiviral shRNA reduced PrP(C) expression in transgenic mice carrying multiple copies of Prnp. To test the therapeutic potential of lentiviral shRNA, we used what we believe to be a novel approach in which the clinical situation was mimicked. We generated chimeric mice derived from lentivector-transduced embryonic stem cells. Depending on the degree of chimerism, these animals carried the lentiviral shRNAs in a certain percentage of brain cells and expressed reduced levels of PrP(C). Importantly, in highly chimeric mice, survival after scrapie infection was significantly extended. Taken together, these data suggest that lentivector-mediated RNA interference could be an approach for the treatment of prion disease.

Brain-derived proteins in the CSF: do they correlate with brain pathology in CJD?

BACKGROUND

Brain derived proteins such as 14-3-3, neuron-specific enolase (NSE), S 100b, tau, phosphorylated tau and Abeta1-42 were found to be altered in the cerebrospinal fluid (CSF) in Creutzfeldt-Jakob disease (CJD) patients. The pathogenic mechanisms leading to these abnormalities are not known, but a relation to rapid neuronal damage is assumed. No systematic analysis on brain-derived proteins in the CSF and neuropathological lesion profiles has been performed.

METHODS

CSF protein levels of brain-derived proteins and the degree of spongiform changes, neuronal loss and gliosis in various brain areas were analyzed in 57 CJD patients.

RESULTS

We observed three different patterns of CSF alteration associated with the degree of cortical and subcortical changes. NSE levels increased with lesion severity of subcortical areas. Tau and 14-3-3 levels increased with minor pathological changes, a negative correlation was observed with severity of cortical lesions. Levels of the physiological form of the prion protein (PrPc) and Abeta1-42 levels correlated negatively with cortical pathology, most clearly with temporal and occipital lesions.

CONCLUSION

Our results indicate that the alteration of levels of brain-derived proteins in the CSF does not only reflect the degree of neuronal damage, but it is also modified by the localization on the brain pathology. Brain specific lesion patterns have to be considered when analyzing CSF neuronal proteins.

Sphingosine kinase and sphingosine-1-phosphate regulate migration, endocytosis and apoptosis of dendritic cells

Dendritic cells (DC) are inducers of primary immune responses and represent an attractive vector for cancer immunotherapy. Sphingosine kinase (SphK) and its product sphingosine-1-phosphate (S1P) play an important role in the regulation of immune cells and cancer, affecting processes such as differentiation, growth or migration. We studied the role of SphK and S1P on migration of DC. RT-PCR showed mRNA expression of SphK in DC, declining from immature (iDC) to mature DC (mDC) to antigen-loaded mDC. Expression of S1P receptors was S1P(1) > S1P(2) = S1P(3), unrelated to maturation or antigen uptake. In transwell assays, iDC migrated towards SDF-1, MIP-1alpha, MCP and S1P, whereby S1P combined with a chemokine had a synergistic effect. mDC migrated towards 6Ckine and MIP-3beta, but not towards S1P. The SphK-inhibitor dihydro-sphingosine (DHS) reduced migration of iDC but not of mDC. In addition S1P(3)-inhibitor suramin inhibited DC migration in response to S1P. DHS had a reverse effect on endocytosis, enhancing the uptake of FITC dextran. We also observed an anti-apoptotic effect of S1P on mDC for the first time. This indicates that SphK/S1P may play a role in accumulation of peripheral iDC at the location of antigen and subsequent antigen-uptake. These findings may help to optimise DC-based cancer immunotherapy by modulation of SphK/S1P.