Christof Renner

Intraoperative MRI to guide the resection of primary supratentorial glioblastoma multiforme—a quantitative radiological analysis

Patients with supratentorial high-grade glioma underwent surgery within a vertically open 0.5-T magnetic resonance (MR) system to evaluate the efficacy of intraoperative MR guidance in achieving gross-total resection. For 31 patients, preoperative clinical data and MR findings were consistent with the putative diagnosis of a high-grade glioma, in 23 cases in eloquent regions. Tumor resections were carried out within a 0.5-T MR SIGNA SP/i (GE Medical Systems, USA). The resection of the lesion was carried out using fully MR compatible neurosurgical equipment and was stopped at the point when the operation was considered complete by the surgeon viewing the operation field with the microscope. We repeated imaging to determine the residual tumor volume only visible with MRI. Areas of tissue that were abnormal on these images were localized in the bed of resection by using interactive MR guidance. The procedure of resection, imaging control and interactive image guidance was repeated where necessary. Almost all tissue with abnormal characteristics was resected, with the exception of tissue localized in eloquent brain areas. The diagnosis of glioblastoma was confirmed in all 31 cases. When comparing the tumor volume before resection and at the point where the neurosurgeon would otherwise have terminated surgery (“first control”), residual tumor tissue was detectable in 29/31 patients; the mean residual tumor volume was 30.7±24%. After repeated resections under interactive image guidance the mean residual tumor volume was 15.1%. At this step we found tumor remnants only in 20/31 patients. The perioperative morbidity (12.9%) was low. Twenty-seven patients underwent sufficient postoperative radiotherapy. We found a significant difference (logrankp=0.0037) in the mean survival times of the two groups with complete resection (n=10, median survival time 537 days) and incomplete resection (n=17, median survival time 237 days). The resection of primary glioblastoma multiforme under intraoperative MR guidance as demonstrated is a possibility to achieve a more complete removal of the tumor than with conventional techniques. In our small but homogeneous patient group we found an increase in the median survival time in patients with MRI for complete tumor resection, and the overall surgical morbidity was low.

Carnosine retards tumor growth in vivo in an NIH3T3-HER2/neu mouse model

BackgroundIt was previously demonstrated that the dipeptide carnosine inhibits growth of cultured cells isolated from patients with malignant glioma. In the present work we investigated whether carnosine also affects tumor growth in vivo and may therefore be considered for human cancer therapy.ResultsA mouse model was used to investigate whether tumor growth in vivo can be inhibited by carnosine. Therefore, NIH3T3 fibroblasts, conditionally expressing the human epidermal growth factor receptor 2 (HER2/neu), were implanted into the dorsal skin of nude mice, and tumor growth in treated animals was compared to control mice. In two independent experiments nude mice that received tumor cells received a daily intra peritoneal injection of 500 μl of 1 M carnosine solution. Measurable tumors were detected 12 days after injection. Aggressive tumor growth in control animals, that received a daily intra peritoneal injection of NaCl solution started at day 16 whereas aggressive growth in mice treated with carnosine was delayed, starting around day 19. A significant effect of carnosine on tumor growth was observed up to day 24. Although carnosine was not able to completely prevent tumor growth, a microscopic examination of tumors revealed that those from carnosine treated animals had a significant lower number of mitosis (p < 0.0003) than untreated animals, confirming that carnosine affects proliferation in vivo.ConclusionAs a naturally occurring substance with a high potential to inhibit growth of malignant cells in vivo, carnosine should be considered as a potential anti-cancer drug. Further experiments should be performed in order to understand how carnosine acts at the molecular level.

Carnosine inhibits ATP production in cells from malignant glioma.

Abstract Objectives: Recently, it was revealed that carnosine inhibits growth of cells isolated from human malignant glioma. In order to understand how this effect is mediated, experiments were performed that addressed a possible influence of carnosine on energy metabolism. Methods: Cells from the glioma line T98G and primary cultured cells from human malignant glioma were cultivated in the presence of carnosine and inhibitors of cellular energy metabolism. As a specific inhibitor for anaerobic glycolysis, oxamate, and as an inhibitor for mitochondrial oxidative phosphorylation, potassium cyanide, were used, and the influence on ATP production was determined using cell-based assays. Results: The experiments identified glycolysis as crucial for ATP production in gliomas. In addition, ATP production by mitochondrial activity did not significantly contribute to ATP production and carnosine was identified to be an inhibitor of the vital anaerobic glycolysis. Discussion: Carnosine might be considered as a potential drug for the treatment of malignant glioma or other tumors since it inhibits the glycolytic energy metabolism that is crucial for cancer cells and malignant gliomas as shown in the current study. This is especially interesting since the dipeptide is a naturally occurring substance that should be well tolerated.

Organotypic slice cultures of human glioblastoma reveal different susceptibilities to treatments

Background Glioblastoma multiforme is the most common lethal brain tumor in human adults, with no major therapeutic breakthroughs in recent decades. Research is based mostly on human tumor cell lines deprived of their organotypic environment or inserted into immune-deficient animals required for graft survival. Here, we describe how glioblastoma specimens obtained from surgical biopsy material can be sectioned and transferred into cultures within minutes. Methods Slices were kept in 6-well plates, allowing direct observation, application of temozolomide, and irradiation. At the end of experiments, slice cultures were processed for histological analysis including hematoxylin-eosin staining, detection of proliferation (Ki67), apoptosis/cell death (cleaved caspase 3, propidium iodide), DNA double-strand breaks (γH2AX), and neural subpopulations. First clinical trials employed irradiation with the heavy ion carbon for the treatment of glioblastoma patients, but the biological effects and most effective dose regimens remain to be established. Therefore, we developed an approach to expose glioblastoma slice cultures to 12C and X-rays. Results We found preservation of the individual histopathology over at least 16 days. Treatments resulted in activation of caspase 3, inhibition of proliferation, and cell loss. Irradiation induced γH2AX. In line with clinical observations, individual tumors differed significantly in their susceptibility to temozolomide (0.4%–2.5% apoptosis and 1%–15% cell loss). Conclusion Glioblastoma multiforme slice cultures provide a unique tool to explore susceptibility of individual tumors for specific therapies including heavy ions, thus potentially allowing more personalized treatments plus exploration of mechanisms of (and strategies to overcome) tumor resistance.

Evaluation of intra-operative ultrasound imaging in brain tumor resection: a prospective study

Abstract Aims: The purpose of our study was to evaluate intra-operative ultrasound (IOUS) as a tool of resection control after brain tumor surgery. In addition, we looked for tumor species suitable for ultrasound representation. Methods: Using a Siemens Omnia Sonoline Ultrasound, 36 tumors were examined, high-grade gliomas (62%), metastases (22%) and others (16%). We focused on tumor imaging by ultrasound with regard to its reliability of tumor expansion and margins. Evaluation of the images was carried out by correlating the ultrasound-based intra-operative measured tumor volume before and after resection with a pre- and post-operative (within 48 hours) measured volume by MRI. The IOUS measurements were performed by the neurosurgeon and the MRI measurements by the neuroradiologist. Thus, the measurement procedures were blinded. Corresponding to a deviation of the ultrasound volume by 10, 20 and > 20% from the MRI volume, the correlation was ranked good, moderate and poor. For assessing the agreement between these two methods of imaging, the statistical analysis was conducted using a method described by Bland and Altman. Results: High-grade gliomas mostly showed a moderate or poor correlation in comparing IOUS- and MRI-tumor volumetry resulting in incomplete resection. Metastases resulted in a good to moderate correlation with a satisfactory extent of resection. The other tumors had poor images with larger tumor residues. The MRI measured volumes tended to be larger on average; the deviation grew with tumor size. Conclusion: The reliability of IOUS depends on tumor type. It is beneficial to use IOUS for the resection of metastases and a few high-grade gliomas. Concerning the volumetric accuracy, the value of IOUS is worse than its value of navigation and resection control.

Identification of factors involved in the anti-tumor activity of carnosine on glioblastomas using a proteomics approach.

Human glioblastoma multiforme is the most malignant brain tumor in adults and is difficult to treat. Recently, it was demonstrated that the dipeptide carnosine inhibits tumor growth, but the main molecular targets are not known. Therefore, a proteomics study with glioblastoma cells treated with carnosine was performed. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time of flight detected 31 proteins expressed differentially under the influence of carnosine. Finally, peptide mass fingerprinting identified the “BCL2-associated athanogene 2” and the “von Hippel-Lindau binding protein 1” among other proteins, linking the action of carnosine to protein folding and HIF-1α signalling.

Hedgehog signaling in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most malignant brain tumor in adults with a median survival of 14.6 mo under the best available treatment. New treatment strategies are therefore urgently required, for which a profound understanding of tumor biology is necessary. Much effort has been devoted to tumor-specific aberrant signaling processes. Recently it was discovered that the transcription factor Gli1, which is activated by hedgehog signaling, is a highly predictive marker in GBM, as determined by immunohistochemistry. To determine whether GBM cells have transcriptionally active Gli1, we performed experiments with reporter genes with cells isolated from surgically removed human tumors and cell lines. We also determined whether the hedgehog signaling inhibitor cyclopamine influences reporter gene expression and cell viability, and we determined the expression of Gli1, SHH and Patched1 by quantitative real-time RT-PCR. Reporter gene analysis of nine cultures and four cell lines demonstrated a significantly enhanced transcriptional activity in six tumor cell cultures and all cell lines. Analysis of cell viability in the presence of cyclopamine revealed a response of all cell cultures with the exception of one primary culture and one cell line, but only one cell line responded to cyclopamine with reduced hedgehog signaling activity. This indicates that the toxicity of cyclopamine toward GBM cells is independent from hedgehog signaling. Since no correlation between hedgehog activity and SHH, Gli1 and Patched1 mRNA levels was observed we conclude that other mechanisms aside from transcriptional regulation of these factors are responsible for hedgehog activity in tumor cells derived from GBM.

Cerebrospinal fluid leak after microsurgical surgery in vestibular schwannomas via retrosigmoidal craniotomy

Abstract Objective: Cerebrospinal fluid (CSF) leak is still a common complication in surgery of vestibular schwannoma, increasing morbidity and prolonging hospital stay. Our single center study was performed to determine the incidences of CSF leaks after microsurgical removal of vestibular schwannoma via a retrosigmoidal approach with two different surgical closure techniques. Methods: Between January 2003 and December 2009 in 81 patients, microsurgical tumor resection using a suboccipital, retrosigmoidal approach was performed with an interdisciplinary ENT and neurosurgical management was performed. In 41 cases, the dural closure was done using a sandwich technique: subdural closure with TissuFleece® respectively Spongostan®, and after that dural suture and epidural Tachosil® were fixed on. In 40 cases, the dura was sealed epidurally with Tachosil after suture. In 65 cases, the posterior wall of the petrous bone was drilled. The closure was performed using muscle and FibrinGlue®. All patients had a minimal follow-up of 1 year. Results: Seven patients (8·6%) developed a CSF fistula. Three patients (3·7%) underwent surgical procedure because of persisting CSF fistula while in four cases (4·9%) spontaneous closure under lumbar drain was observed. Comparing the different techniques of dural sealing, we found in 41 patients with sandwich technique three CSF leaks (7·3%) while there were four CSF leaks (10%) in 40 patients with a single epidurally sealed dural closure (P=0·69). No rhinorrhea or otorhinorrhea was observed. No intracranial infection or meningitis in case of CSF leak occurred. Conclusion: Suture and occlusion of the dura is an important step to prevent CSF leak and postoperative infection. By comparing sandwich technique and single-layer dural sealing, no significant difference could be shown.

Comparing Brain Tissue Oxygen Measurements and Derived Autoregulation Parameters from Different Probes (Licox vs. Raumedic)

We investigated two commercially available probes for measurement of the partial pressure of brain tissue oxygen (PbrO2) and calculation of the index of brain tissue oxygen pressure reactivity (ORx) in 7 patients after aneurysmal subarachnoid hemorrhage (SAH). Simultaneous monitoring of PbrO2 using the Licox(®) probe and the multiparameter Raumedic probe (Neurovent PTO(®)), measuring PbrO2, intracranial pressure (ICP) and brain temperature (Neurovent PTO) was performed for a median of 9 days (range 7-17 days). Both probes provided stable monitoring throughout the desired period. Mean PbrO2 from Licox and Neurovent PTO was 16.1 ± 9.0 mmHg and 17.5 ± 11.9 mmHg respectively. Mean ORx was 0.35 ± 0.44 and 0.31 ± 0.43 respectively. There was a difference in the measurement of PbrO2 of -2.73 ± 10.1 mmHg (Licox - Raumedic). The difference in the two values for the calculated ORx was far smaller (0.03 ± 0.31; Licox - Raumedic) and the correlation coefficient higher than for both values of PbrO2 (0.76 for ORx vs. 0.56 for PbrO2). The calculation of the autoregulation parameter ORx seemed more independent of the measurement process than the measurement of PbrO2 itself and signifies the potential clinical importance of this parameter.

Distributive shock, cardiac arrhythmias and multiple organ failure following surgery of a fourth ventricular epidermoid

A 33-years-old male patient presented with cardiac arrhythmias, acute shock and multiple organ dysfunction after the surgical removal of a massive epidermoid posterior to the brainstem. The patient initially presented with paraesthesia along the right C6 dermatome due to a big tumour at the brain stem. Surgical removal was performed without adverse events and he was transferred to our intensive care unit (ICU) immediately after the operation. Though initially showing a stable postsurgical course he developed cardiac arrhythmias and a state of acute distributive shock with consecutive multi organ failure. Extensive diagnostic measures could not identify a specific cause for this rapid deterioration. However, under carefully monitored symptomatic therapy the patient improved quickly, was extubated 72 h after admission and discharged from the ICU 6 days later. The follow-up did not show any persisting neurological deficits and no evidence of a residual tumour in the MRI-study.