Evaluation of efficacy and biocompatibility of a novel semisynthetic collagen matrix as a dural onlay graft in a large animal model

Background

Semisynthetic collagen matrices are promising duraplasty grafts with low risk of cerebrospinal fluid (CSF) fistulas, good tissue integration and minor foreign body reaction. The present study investigates the efficacy and biocompatibility of a novel semisynthetic bilayered collagen matrix (BCM, B. Braun Aesculap) as dural onlay graft for duraplasty.

Methods

Thirty-four pigs underwent osteoclastic trepanation, excision of the dura, and placement of a cortical defect, followed by duraplasty using BCM, Suturable DuraGen™ (Integra Neuroscience), or periosteum. CSF tightness and intraoperative handling of the grafts were evaluated. Pigs were sacrificed after 1 and 6 months for histological analysis.

Findings

BCM and DuraGen™ showed superior handling than periosteum with a trend for better adhesion to dura and CSF tightness for BCM. Periosteum, which was sutured unlike the synthetic grafts, had the highest intraoperative CSF tightness. Duraplasty time with periosteum was significantly higher (14.4 ± 2.7 min) compared with BCM (2.8 ± 0.8 min) or DuraGen™ (3.0 ± 0.5 min). Tissue integration by fibroblast infiltration was observed after 1 month for all devices. More adhesions between graft and cortex were observed with DuraGen™ compared with BCM and periosteum. No relevant adhesions between leptomeninges and BCM were observed and all devices showed comparable lymphocytic reaction of the brain. All devices were completely integrated after 6 months. BCM and DuraGen™ showed a trend for an enhanced lymphocytic reaction of the brain parenchyma compared with periosteum. Implant rejection was not observed.

Conclusion

Semisythetic collagen matrices are an attractive alternative in duraplasty due to their easy handling, lower surgical time, and high biocompatibility.

Microsurgical fenestration of perineural cysts to the thecal sac at the level of the distal dural sleeve

BACKGROUND

Surgery for symptomatic sacral perineural cysts remains an issue of discussion. Assuming micro-communications between the cyst and thecal sac resulting in a valve mechanism and trapping of CSF as a pathomechanism, microsurgical fenestration from the cyst to the thecal sac was performed to achieve free CSF communication.

METHODS

In 13 consecutive patients (10 female, 3 male), MRI revealed sacral perineural cysts and excluded other pathologies. Micro-communication between the thecal sac and the cysts was shown by delayed contrast filling of the cysts on postmyelographic CT. Surgical fenestration achieved free CSF communication between the thecal sac and cysts in all patients. The patient histories, follow-up examinations and self-assessment scales were analyzed. Symptoms at initial presentation included lumbosacral pain, pseudoradicular symptoms, genital pain and urinary dysfunction. Mean follow-up was 10.7 ± 6.6 months.

FINDINGS

Besides one CSF fistula, no surgical complications were observed. Five patients did not improve after surgery; in four of these cases multiple cysts were found, but small and promptly filling cysts remained untreated. Seven patients reported lasting benefit following surgery; three of these had single cysts, and all had cysts >1 cm. One patient initially benefited from cyst fenestration but experienced recurrent pain within 2 months postoperatively. Re-myelography revealed delayed contrast filling of the recurrent cyst; however, surgical revision did not lead to an improvement despite successful fenestration and collapse of the cyst revealed by postoperative imaging.

CONCLUSIONS

Microsurgical fenestration of sacral perineural cysts to the thecal sac is a surgical approach that has shown success in the treatment of lumbosacral pain, pseudoradicular symptoms, genital pain and urinary dysfunction associated with sacral perineural cysts. Our analysis, however, shows that mainly patients with singular large cysts benefit from this treatment.

[Demands for endoscopy service outside of regular hours: a retrospective study and literature analysis]

BACKGROUND AND OBJECTIVE

Many acute care hospitals provide round-the-clock emergency endoscopy to guarantee immediate diagnosis and treatment of acute conditions of the gastrointestinal tract. This study is the first one to assess the demand for emergency endoscopy outside usual working hours.

PATIENTS AND METHODS

This study evaluated retrospectively 315 consecutive emergency endoscopies done at an acute care hospital (575 beds; catchment population 100,000, in the Ruhr area of Germany) between 26.7.2003 and 01.11.2009 (6 years and 3 months) outside usual working hours (i.e. during the weekend and from 6 pm to 8 am during weekdays). This represents 50 emergency endoscopies outside working hours per 100,000 people per year.

RESULTS

56.8 % of the examinations took place during the weekend (Saturday or Sunday), 26.7 % during the night (10 pm - 8 am). The distribution of the different endoscopic modalities was: 228 EGD (72.4 %), 42 incomplete colonoscopies or recto-sigmoidoscopies (13.3 %), 28 retrograde cholangio- or cholangiopancreatographies (8.9 %), 16 complete colonoscopies (5.2 %) and one oral enteroscopy. 208 (66%) of endoscopic procedures were purely diagnostic without any therapeutic intervention. The indication for endoscopy was documented in 243 of the 315 procedures. In 76.5 % of those cases the suspicion of a gastrointestinal bleeding was the indication for endoscopy.

CONCLUSION

In an acute care hospital in Germany 50 emergency endoscopies outside working hours were performed per 100,000 population per year. This rate exceeds that reported in other European countries (Great Britain: 26.7, Norway: 24). Further studies are needed to evaluate the impact of different emergency endoscopic strategies on patient outcome and treatment costs.

First-line treatment of malignant glioma with carmustine implants followed by concomitant radiochemotherapy: a multicenter experience

Randomized phase III trials have shown significant improvement of survival 1, 2, and 3 years after implantation of 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU) wafers for patients with newly diagnosed malignant glioma. But these studies and subsequent non-phase III studies have also shown risks associated with local chemotherapy within the central nervous system. The introduction of concomitant radiochemotherapy with temozolomide (TMZ) has later demonstrated a survival benefit in a phase III trial and has become the current treatment standard for newly diagnosed malignant glioma patients. Lately, this has resulted in clinical protocols combining local chemotherapy with BCNU wafers and concomitant radiochemotherapy with TMZ although this may carry the risk of increased toxicity. We have compiled the treatment experience of seven neurosurgical centers using implantation of carmustine wafers at primary surgery followed by 6 weeks of radiation therapy (59–60 Gy) and 75 mg/m²/day TMZ in patients with newly diagnosed glioblastoma followed by TMZ monochemotherapy. We have retrospectively analyzed the postoperative clinical course, occurrence and severity of adverse events, progression-free interval, and overall survival in 44 patients with newly diagnosed glioblastoma multiforme. All patients received multimodal treatment including tumor resection, BCNU wafer implantation, and concomitant radiochemotherapy. Of 44 patients (mean age 59 ± 10.8 years) with glioblastoma who received Gliadel wafer at primary surgery, 28 patients (64%) had died, 16 patients (36%) were alive, and 15 patients showed no evidence of clinical or radiographic progression after a median follow-up of 15.6 months. At time of analysis of adverse events in this patient population, the median overall survival was 12.7 months and median progression-free survival was 7.0 months. Surgical, neurological, and medical adverse events were analyzed. Twenty-three patients (52%) experienced adverse events of any kind including complications that did not require treatment. Nineteen patients (43%) experienced grade 3 or grade 4 adverse events. Surgical complications included cerebral edema, healing abnormalities, cerebral spinal fluid leakage, meningitis, intracranial abscess, and hydrocephalus. Neurological adverse events included newly diagnosed seizures, alteration of mental status, and new neurological deficits. Medical complications were thromboembolic events (thrombosis, pulmonary embolism) and hematotoxicity. Combination of both treatment strategies, local chemotherapy with BCNU wafer and concomitant radiochemotherapy, appears attractive in aggressive multimodal treatment schedules and may utilize the sensitizing effect of TMZ and carmustine on MGMT and AGT on their respective drug resistance genes. Our data demonstrate that combination of local chemotherapy and concomitant radiochemotherapy carries a significant risk of toxicity that currently appears underestimated. Adverse events observed in this study appear similar to complication rates published in the phase III trials for BCNU wafer implantation followed by radiation therapy alone, but further add the toxicity of concomitant radiochemotherapy with systemic TMZ. Save use of a combined approach will require specific prevention strategies for multimodal treatments.

Specific visualization of glioma cells in living low-grade tumor tissue

Background

The current therapy of malignant gliomas is based on surgical resection, radio-chemotherapy and chemotherapy. Recent retrospective case-series have highlighted the significance of the extent of resection as a prognostic factor predicting the course of the disease. Complete resection in low-grade gliomas that show no MRI-enhanced images are especially difficult. The aim in this study was to develop a robust, specific, new fluorescent probe for glioma cells that is easy to apply to live tumor biopsies and could identify tumor cells from normal brain cells at all levels of magnification.

Methodology/Principal Findings

In this investigation we employed brightly fluorescent, photostable quantum dots (QDs) to specifically target epidermal growth factor receptor (EGFR) that is upregulated in many gliomas. Living glioma and normal cells or tissue biopsies were incubated with QDs coupled to EGF and/or monoclonal antibodies against EGFR for 30 minutes, washed and imaged. The data include results from cell-culture, animal model and ex vivo human tumor biopsies of both low-grade and high-grade gliomas and show high probe specificity. Tumor cells could be visualized from the macroscopic to single cell level with contrast ratios as high as 1000: 1 compared to normal brain tissue.

Conclusions/Significance

The ability of the targeted probes to clearly distinguish tumor cells in low-grade tumor biopsies, where no enhanced MRI image was obtained, demonstrates the great potential of the method. We propose that future application of specifically targeted fluorescent particles during surgery could allow intraoperative guidance for the removal of residual tumor cells from the resection cavity and thus increase patient survival.

Intra-osseous ultrasound for pedicle screw positioning in the subaxial cervical spine: an experimental study

Background

In contrast to other regions of the human spine, dorsal fixation with rods and pedicle screws is comparatively rarely performed in the cervical spine. Although this technique provides a higher mechanical strength than the more frequently used lateral mass screws, many surgeons fear the relatively high rate of misplacements. This higher incidence is mainly due to the complex vertebral anatomy in this spinal segment. For correct screw placement, the availability of an immediate and efficient intra-operative imaging tool to ascertain the accuracy of the pedicle screw hole position would be beneficial. We have previously investigated the usefulness of an intraspinal, specifically, intra-osseous ultrasound technique in the lumbar spine. In this study its accuracy as a means of controlling intrapedicular screw hole positioning has been evaluated in the cervical spine.

Methods

An endovascular ultrasound transducer was used for the intra-luminal scanning of 54 pedicle screw holes in cadaveric human spine specimens. Twenty-three of these had been intentionally misplaced (cortex breached). The resulting image files were assessed by three investigators blinded to both the procedure and the corresponding CT findings.

Findings

The investigators differentiated correctly between adequately and poorly placed pedicle screw holes in 96% of cases. False negatives and false positives both occurred in no more than 1.8% of cases.

Conclusions

Intrapedicular ultrasonography of pedicle screw holes in the cervical spine is a promising technique for the intra-operative assessment of bore hole placement and may increase operative safety and postoperative outcome in posterior cervical fusion surgery.

A Transmedullary Approach to Occlusion of a Ventral Perimedullary Arteriovenous Fistula of the Thoracic Spinal Cord

OBJECTIVE

A spinal perimedullary arteriovenous fistula (PMAVF) is a direct fistula of one or more spinal arteries into the perimedullary venous network with reversed venous flow and subsequent venous congestion of the spinal cord. The therapeutic goal of surgery is to normalize the venous drainage by obliterating the fistula. Strictly ventral lesions typically require an anterior approach to ensure adequate exposure of the fistula as well and the preservation of the physiological blood supply to the spinal cord.

CLINICAL PRESENTATION

We present a case of a ventral PMAVF at the level of T10 with feeders from the anterior spinal artery, caudally draining veins on the ventral spinal cord, and a dilated transmedullary vein filling cranially draining veins on the dorsal aspect of the spinal cord.

TECHNIQUE

The dilated transmedullary vein was approached by a laminectomy. The vein was coagulated, and the gliotic channel was used to approach the ventral fistula site from the dorsal surface of the spinal cord. Complete obliteration of the fistula was achieved, and the preoperative neurological deficit improved.

CONCLUSION

We conclude that transmedullarly draining veins offers a possible dorsal approach for the occlusion of some ventral PMAVFs, thus avoiding more complex anterior approaches to the ventral spinal cord.

Robot-assisted image-guided transcranial magnetic stimulation for somatotopic mapping of the motor cortex: a clinical pilot study

Purpose

Shape and exact location of motor cortical areas varies among individuals. The exact knowledge of these locations is crucial for planning of neurosurgical procedures. In this study, we have used robot-assisted image-guided transcranial magnetic stimulation (Ri-TMS) to elicit MEP response recorded for individual muscles and reconstruct functional motor maps of the primary motor cortex.

Methods

One healthy volunteer and five patients with intracranial tumors neighboring the precentral gyrus were selected for this pilot study. Conventional MRI and fMRI were obtained. Transcranial magnetic stimulation was performed using a MagPro X100 stimulator and a standard figure-of-eight coil positioned by an Adept Viper s850 robot. The fMRI activation/Ri-TMS response pattern were compared. In two cases, Ri-TMS was additionally compared to intraoperative direct electrical cortical stimulation.

Results

Maximal MEP response of the m. abductor digiti minimi was located in an area corresponding to the “hand knob” of the precentral gyrus for both hemispheres. Repeated Ri-TMS measurements showed a high reproducibility. Simultaneous registration of the MEP response for m. brachioradialis, m. abductor pollicis brevis, and m. abductor digiti minimi demonstrated individual peak areas of maximal MEP response for the individual muscle groups. Ri-TMS mapping was compared to the corresponding fMRI studies. The areas of maximal MEP response localized within the “finger tapping” activated areas by fMRI in all six individuals.

Conclusions

Ri-TMS is suitable for high resolution non-invasive preoperative somatotopic mapping of the motor cortex. Ri-TMS may help in the planning of neurosurgical procedures and may be directly used in navigation systems.

Chloroquine activates the p53 pathway and induces apoptosis in human glioma cells

Glioblastoma is the most common malignant brain tumor in adults. The currently available treatments offer only a palliative survival advantage and the need for effective treatments remains an urgent priority. Activation of the p53 growth suppression/apoptotic pathway is one of the promising strategies in targeting glioma cells. We show that the quinoline derivative chloroquine activates the p53 pathway and suppresses growth of glioma cells in vitro and in vivo in an orthotopic (U87MG) human glioblastoma mouse model. Induction of apoptosis is one of the mechanisms underlying the effects of chloroquine on suppressing glioma cell growth and viability. siRNA-mediated downregulation of p53 in wild-type but not mutant p53 glioblastoma cells substantially impaired chloroquine-induced apoptosis. In addition to its p53-activating effects, chloroquine may also inhibit glioma cell growth via p53-independent mechanisms. Our results clarify the mechanistic basis underlying the antineoplastic effect of chloroquine and reveal its therapeutic potential as an adjunct to glioma chemotherapy.

Implementation of a critical incident reporting system in a neurosurgical department

BACKGROUND

Critical incident monitoring is an important tool for quality improvement and the maintenance of high safety standards. It was developed for aviation safety and is now widely accepted as a useful tool to reduce medical care-related morbidity and mortality. Despite this widespread acceptance, the literature has no reports on any neurosurgical applications of critical incident monitoring. We describe the introduction of a mono-institutional critical incident reporting system in a neurosurgical department. Furthermore, we have developed a formula to assess possible counterstrategies.

METHODS

All staff members of a neurosurgical department were advised to report critical incidents. The anonymous reporting form contained a box for the description of the incident, several multiple-choice questions on specific risk factors, place and reason for occurrence of the incident, severity of the consequences and suggested counterstrategies. The incident data was entered into an online documentation system (ADKA DokuPik) and evaluated by an external specialist. For data analysis we applied a modified assessment scheme initially designed for flight safety.

RESULTS

Data collection was started in September 2008. The average number of reported incidents was 18 per month (currently 216 in total). Most incidents occurred on the neurosurgical ward (64%). Human error was involved in 86% of the reported incidents. The largest group of incidents consisted of medication-related problems. Accordingly, counterstrategies were developed, resulting in a decrease in the relative number of reported medication-related incidents from 42% (March 09) to 30% (September 09).

CONCLUSIONS

Implementation of the critical incident reporting system presented no technical problems. The reporting rate was high compared to that reported in the current literature. The formulation, evaluation and introduction of specific counterstrategies to guard against selected groups of incidents may improve patient safety in neurosurgical departments.

Intraosseous ultrasonography to determine the accuracy of drill hole positioning prior to the placement of pedicle screws: an experimental study

Object

Dorsal fixation with rods and pedicle screws (PSs) is the most frequently used surgery to correct traumatic and degenerative instabilities of the human spine. Prior to screw placement, screw holes are drilled along the vertebral pedicles. Despite the use of a variety of techniques, misplacement of screw holes, and consequently of the PSs, is a common problem. The authors investigated the usefulness of an intraspinal, intraosseous ultrasonography technique to determine the accuracy of drill hole positioning.

Methods

An endovascular ultrasound transducer was used for the intraluminal scanning of bore holes in trabecular bovine bone, 12 pedicle drill holes in cadaveric human spine, and 4 pedicle drill holes in a patient undergoing thoracic spondylodesis. Seven of the experimental bore holes in the cadaveric spine were placed optimally (that is, inside the pedicle) and 5 were placed suboptimally (breaching the medial or lateral cortical surface of the pedicle). Computed tomography scans were obtained in the patient and cadaveric specimen after the procedure.

Results

The image quality achieved in examinations of native bovine bone tissue, the formalin-fixed human spine specimen, and human vertebrae in vivo was equal. The authors endosonographically identified correct intrapedicular and intravertebral positions as well as poor (cortex breached) placement of drill holes.

Conclusions

Intraosseous ultrasonography is a promising technique for the investigation of PS holes prior to screw implantation, and may add to the safety of PS placement.

Untreated glioblastoma multiforme: increased myo-inositol and glutamine levels in the contralateral cerebral hemisphere at proton MR spectroscopy

PURPOSE

To use localized in vivo proton magnetic resonance (MR) spectroscopy of the contralateral hemisphere in patients with glioblastoma multiforme (GBM) to detect alterations in cerebral metabolites as potential markers of infiltrating GBM cells.

MATERIALS AND METHODS

The study was approved by the ethics committee, and written informed consent was obtained. Twenty-two patients with newly diagnosed and untreated GBM underwent in vivo single-voxel short echo time proton MR spectroscopy with a 3-T MR imaging system. Absolute metabolite concentrations in the hemisphere contralateral to the tumor were compared with data from five patients with low-grade gliomas (LGGs) and from a group of 14 age-matched control subjects by using analysis of variance and subsequent t tests or corresponding nonparametric tests.

RESULTS

In the contralateral hemisphere, MR spectroscopy revealed increased concentrations of myo-inositol and glutamine. Mean myo-inositol levels were significantly increased in patients with GBM (3.6 mmol/L +/- 0.8 [standard deviation]) relative to levels in control subjects (3.1 mmol/L +/- 0.6; P = .03) and tended to be higher relative to levels in patients with LGG (2.7 mmol/L +/- 0.8; P = .09). Mean glutamine concentrations in patients with GBM (3.4 mmol/L +/- 0.9) differed significantly from those in control subjects (2.7 mmol/L +/- 0.7; P = .01); mean concentrations in patients with GBM differed from those in patients with LGG (2.4 mmol/L +/- 0.5; P = .01). There were no significant differences between data in patients with LGG and in control subjects.

CONCLUSION

Increased concentrations of myo-inositol and glutamine in the contralateral normal-appearing white matter of GBM patients are consistent with mild astrocytosis and suggest the detectability of early neoplastic infiltration by using proton MR spectroscopy in vivo.

Brain-mapping using robotized TMS

We present first results of brain-mapping using robotic Transcranial Magnetic Stimulation. This non-invasive procedure enables the reliable detection of the representation of individual muscles or muscle groups in the motor-cortex. The accuracy is only exceeded by direct electrical stimulation of the brain during surgery. Brain-mapping using robotic TMS can also be used to detect displacements of brain regions caused by tumors. The advantage of TMS is that it is non-invasive. In this study, we compare results from statistical mapping with robotic TMS to results achieved from direct stimulation done during tumor surgery. To our knowledge this is the first study of this type. We mapped the representation of three muscle groups (forearm, pinky and thumb) in tumor patients with the robot-aided TMS protocol and with direct stimulation. The resulting maps agree within 5mm.

Imaging of human brain tumor tissue by near-infrared laser coherence tomography

INTRODUCTION

Intraoperative detection of residual tumor remains an important challenge in surgery to treat gliomas. New developments in optical techniques offer non-invasive high-resolution imaging that may integrate well into the workflow of neurosurgical operations. Using an intracranial glioma model, we have recently shown that time domain optical coherence tomography (OCT) allows discrimination of normal brain, diffusely invaded brain tissue, and solid tumor. OCT imaging allowed acquisition of 2D and 3D data arrays for multiplanar analysis of the tumor to brain interface. In this study we have analyzed biopsy specimens of human brain tumors and we present the first feasibility study of intraoperative OCT and post-image acquisition processing for non-invasive imaging of the brain and brain tumor.

METHODS

We used a Sirius 713 Tomograph with a superluminescence diode emitting light at a near infrared central wavelength of 1,310 nm and a coherence length of 15 microm. The light is passed through an optical mono mode fiber to a modified OCT adapter containing a lens system with a working distance of 10 cm and an integrated pilot laser. Navigation-registered tumor biopsies were imaged ex vivo and the intraoperative site of optical tissue analysis was registered by marker acquisition using a neuronavigation system.

RESULTS

Optical coherence tomography non-contact measurements of brain and brain tumor tissue produced B-scan images of 4 mm in width and 1.5-2.0 mm in depth at an axial and lateral optical resolution of 15 microm. OCT imaging demonstrated a different microstructure and characteristic signal attenuation profiles of tumor versus normal brain. Post-image acquisition processing and automated detection of the tissue to air interface was used to realign A-scans to compensate for image distortions caused by pulse- and respiration-induced movements of the target volume. Realigned images allowed monitoring of intensity changes within the scan line and facilitated selection of areas for the averaging of A-scans and the calculation of attenuation coefficients for specific regions of interest.

CONCLUSION

This feasibility study has demonstrated that OCT analysis of the tissue microstructure and light attenuation characteristics discriminate normal brain, areas of tumor infiltrated brain, solid tumor, and necrosis. The working distance of the OCT adapter and the A-scan acquisition rate conceptually allows integration of the OCT applicator into the optical path of the operating microscopes. This would allow a continuous analysis of the resection plain, providing optical tomography, thereby adding a third dimension to the microscopic view and information on the light attenuation characteristics of the tissue.

Multi-photon excitation fluorescence microscopy of brain-tumour tissue and analysis of cell density

BACKGROUND

Recent studies have highlighted the importance of the complete resection of a brain tumour but the task often remains a challenge for the neurosurgeon. New technologies which add objective information beyond visualisation provided by the traditional operating microscope are required. In this study, we have analysed the cellular density of the tumour/brain interface using three dimensional multi-photon microscopy intensity-images of experimental gliomas and human brain-tumour biopsy samples.

METHODS

The density of cellular nuclei was determined in specimens of experimental gliomas in a mouse model and human brain tumour biopsies by analysis of optical tissue sections. Three dimensional multi-photon microscopy image stacks were compared to serial H&E stained sections of conventional histopathology.

FINDINGS

Both techniques consistently showed a good correlation of cell density values in solid tumour tissue of experimental gliomas versus adjacent brain. The multi-photon microscopy analysis of human biopsy specimens showed that optical analysis of native tissue provided information on the cellular density.

CONCLUSIONS

Multi-photon microscopy is an efficient and rapid tool for the study of brain and brain tumour tissue. Multi-photon microscopy allows the detection of individual tumour cells and tumour cell clusters in native tissue biopsies and may therefore provide a tool in the identification of highly cellular lesions during the resection of brain tumours.

A non-midline spheno-orbital encephalocele in a newborn

Basal encephaloceles in western countries occur in 1 of every 35 000-40 000 live births; with an incidence of less than 10% they are the least common of all encephaloceles. Certain subtypes such as transsphenoidal variants may be as rare as 1 in 700 000 live births. These rare encephaloceles are classified into five anatomic types: spheno-ethmodial, transsphenoidal, spheno-orbital, transethmoidal, and spheno-maxillary. Here we present an exceedingly rare variant of a non-midline basal encephalocele of the spheno-orbital type, which was treated by resection of the encephalocele, which contained dysplastic central nervous system tissue, on day four post partum. The patient had no neurological deficits and a six year follow-up showed a normal intellect and a good cosmetic result.

Differential effect of imatinib and synergism of combination treatment with chemotherapeutic agents in malignant glioma cells

Imatinib mesylate (STI571, Gleevec) is a signal transduction inhibitor and novel anti-cancer agent. It selectively inhibits aberrantly activated tyrosine kinases in malignant cells, for example, bcr-abl in leukaemia, platelet-derived growth factor receptor and stem cell factor receptor (c-Kit) in solid cancers including malignant glioma. However, recently published clinical studies with imatinib monotherapy in patients with malignant glioma demonstrated only very modest anti-tumour activity. The aim of this study was to investigate the biological activity of imatinib, its cellular mechanisms of action and its synergism with other chemotherapeutic agents in human malignant glioma cells in culture. Expression of PDGF/R and c-Kit was analyzed by RT-PCR. Proliferation was measured by MTT assays and drug synergy was assessed by the Chou-Talalay method. Cell cycle and apoptosis were analyzed by flow cytometry and migration by monolayer migration assays. Multi-immunoblot was performed on imatinib-treated and control malignant glioma cells. Results indicate that imatinib is more effective in inhibiting cell colony formation and migration rather than proliferation. Imatinib treatment caused cell cycle arrest of glioma cells in G0-G1 or G2/M, with significant elevation of a few cyclin-dependent kinases. Furthermore, imatinib acted synergistically with chemotherapy agents, such as the DNA alkylating agent, temozolomide, and riboneucleotide reductase inhibitors, for example, hydroxyurea at varied effective dose levels. In conclusion, imatinib exerts varied biological effects on malignant glioma cells in culture. Synergistic interaction of imatinib with chemotherapy agents may be related to cell cycle control mechanisms and could be potentially important in a clinical setting.