Erythropoietin augments survival of glioma cells after radiation and temozolomide

PURPOSE

Despite beneficial effects of irradiation/chemotherapy on survival of glioblastoma (GBM) patients, collateral damage to intact neural tissue leads to "radiochemobrain" and reduced quality of life in survivors. For prophylactic neuroprotection, erythropoietin (EPO) is a promising candidate, provided that concerns regarding potential tumor promoting effects are alleviated.

METHODS AND MATERIALS

Human GBM-derived cell lines U87, G44, G112, and the gliosarcoma-derived line G28 were treated with EPO, with and without combinations of irradiation or temozolomide (TMZ). Responsiveness of glioma cells to EPO was measured by cell migration from spheroids, cell proliferation, and clonogenic survival. Implantation of U87 cells into brains of nude mice, followed 5 days later by EPO treatment (5,000 U/kg intraperitoneal every other day for 2 weeks) should reveal effects of EPO on tumor growth in vivo. Reverse transcriptase-polymerase chain reaction was performed for EPOR, HIF-1alpha, and epidermal growth factor receptor (EGFR)vIII in cell lines and 22 human GBM specimens.

RESULTS

EPO did not modulate basal glioma cell migration and stimulated proliferation in only one of four cell lines. Importantly, EPO did not enhance tumor growth in mouse brains. Preincubation of glioma cells with EPO for 3 h, followed by irradiation and TMZ for another 24 h, resulted in protection against chemoradiation-induced cytotoxicity in three cell lines. Conversely, EPO induced a dose-dependent decrease in survival of G28 gliosarcoma cells. In GBM specimens, expression of HIF-1alpha correlated positively with expression of EPOR and EGFRvIII. EPOR and EGFRvIII expression did not correlate.

CONCLUSIONS

EPO is unlikely to appreciably influence basal glioma growth. However, concomitant use of EPO with irradiation/chemotherapy in GBM patients is not advisable.

Safety profile of carmustine wafers in malignant glioma: a review of controlled trials and a decade of clinical experience

BACKGROUND

Carmustine (1,3-bis [2-chloroethyl]-1-nitrosourea, or BCNU) wafers are approved for recurrent glioblastoma and newly diagnosed malignant glioma (MG). Based on considerable clinical experience and use in multimodal regimens, the safety of BCNU wafers needs a re-evaluation.

SCOPE

A review of literature from 1996 to February 2008 was conducted on the safety of BCNU wafer in MG patients using search criteria in Medline, EMBASE, and BIOSIS. Abstracts from relevant US and European meetings were also evaluated. Three Phase III (two were pivotal) and 26 non-Phase III studies met inclusion criteria. Overall incidence was estimated for each adverse event (AE), and data from individual studies were summarised as median (range) rates. Comparisons were based on consistent similarities or differences across overall incidence, median rate and range.

FINDINGS

BCNU wafer group AE rates from the two pivotal Phase III trials ranged from 4-23% for cerebral oedema, 4-9% for intracranial hypertension, 14-16% for healing abnormalities, 5% for CSF leaks, 4-5% for intracranial infection, 19-33% for seizures, 10% for deep vein thrombosis, and 8% for pulmonary embolus. There were no notable differences in AE rates between the two pivotal Phase III and 26 non-Phase III studies. For the non-pivotal studies, the overall incidence of AEs was low, ranging from 0.2% for intracranial hypertension to 9.6% for healing abnormalities. Healing abnormalities, intracranial infection, and seizures were the most consistently reported AEs, having been observed in 16, 12, and 11 studies, respectively. Rates of healing abnormalities appeared higher in recurrent than in newly diagnosed disease. There were no notable differences between BCNU wafer plus adjuvant treatment (e.g., temozolomide) and BCNU wafer alone, with the exception of haematologic toxicity.

CONCLUSION

This review of safety data for BCNU wafers provides reassurance that the AE rates reported in current treatment strategies including multimodal treatment approaches are comparable to those observed in the initial registration studies. The broad range of AE rates may reflect differences in the perioperative and postoperative management. Clinical experience suggests that strategies may exist to reduce the risk of complications.

Multiphoton excitation fluorescence microscopy of 5-aminolevulinic acid induced fluorescence in experimental gliomas

BACKGROUND AND OBJECTIVE

The clinical usefulness of 5-ALA guided detection of tumor tissue has been demonstrated for a number of malignancies. However, current techniques of intraoperative detection of protoporphyrin IX fluorescence in situ do not offer subcellular resolution. Therefore, discrimination of non-specific 5-ALA induced fluorescence remains difficult.

MATERIALS AND METHODS

In this study we have used an orthotopic glioma model to analyze PpIX fluorescence in tumor tissue and normal brain by multiphoton excitation microscopy after intraperitoneal administration of 5-ALA. A DermaInspect in vivo imaging system was used for autofluorescence measurements at 750 nm excitation and detection in the green channel of a standard photomultiplier module. For detection of PpIX fluorescence at different excitation wavelengths a red sensitive version of the photomultiplier and a filter combination of short pass filters and a color glass long pass filter was used restricting the sensitivity in the red channel to a range of 580-700 nm.

RESULTS

Multiphoton microscopy allowed a higher structural definition of tumor tissue based on the excitation of 5-ALA induced PpIX fluorescence compared to autofluorescence imaging. The high resolution of multiphoton microscopy allowed discrimination of fluorescence from the cytoplasm of tumor cells and 5-ALA induced PpIX fluorescence of normal brain parenchyma adjacent to tumor. Fluorescence lifetime imaging showed significantly longer fluorescence lifetimes of 5-ALA induced PpIX fluorescence in tumor tissue compared to normal brain. This allowed definition and visualization of the tumor/brain interface based on this parameter alone.

CONCLUSION

Multiphoton microscopy of 5-ALA induced PpIX fluorescence in brain tumor tissue conceptually provides a high resolution diagnostic tool, which in addition to structural information may also provide photochemical/functional information.

Wild-type p53 in cancer cells: when a guardian turns into a blackguard

The tumor suppressor p53 controls a broad range of cellular responses. Induction of a transient (cell cycle arrest) or a permanent (senescence) block of cell proliferation, or the activation of cell death pathways in response to genotoxic stress comprise the major arms of the survival-death axis governed by p53. Due to these biological properties, inactivation of p53 is a crucial step in tumor development and progression, reflected by the high incidence of TP53 mutations in different types of human cancers. The remarkable potency of p53 in suppressing tumorigenic outgrowth has promoted the expectation that tumor cells expressing wild-type p53 (wtp53) should be more prone to elimination by cytotoxic treatments than tumor cells expressing mutant p53 (mutp53) with defunct wtp53 activities. However, recent findings yielded somewhat unexpected insights concerning the preponderance of the survival-promoting effects of wtp53 in cancer cells, a rather undesired property from the therapeutic point of view. In this commentary we will discuss the possibility that the developmentally established distinct patterns of wtp53 mediated responses in different tissues are an important factor in determining the ultimate outcome of cellular responses mediated by wtp53 in different types of tumor cells, with a particular focus on the divergent impact of wtp53 in malignant tumors of the central nervous system. We infer that a selective gain of pro-survival functions of wtp53 in cancer cells will confer a survival advantage that counteracts tumor therapy.

Online tumor conference in the clinical management of gynecological cancer: experience from a pilot study in Germany

The concept of the online tumor conference was established in 2004 as a pilot project. We developed specific web-based software to organize and conduct online tumor board meetings of gynecologists, surgeons, radiologists, oncologists, and pathologists from different hospitals and gynecological practitioners, discussing individual patient's cases, defining therapy options, and exchanging clinical experience. Following a didactic approach, patient data are presented to the participants, with a special focus toward patient's preference and late toxicity from prior therapy. Then different national (eg, Arbeitsgemeinschaft Gynaekologische Onkologie, Deutsche Gesellschag fur Gynaekologic und Geburtshilfe) and international guidelines (eg, American Society of Clinical Oncology, National Cancer Institute), current study results based on literature review and open clinical trials are discussed. An individual diagnosis and therapy recommendation for each patient is reached by consensus. All protocols, guidelines, and publication data are upgraded and dispersed via Internet for all participants. In the period from December 2004 to August 2006, 39 tumor board conferences were performed with a total of 667 participants. One hundred forty-four patients' cases were presented, and 121 peer-reviewed second-opinions were sought. In an anonymous survey, 84% of the participants reported to be satisfied with the information content and 72% with the technical support. Overall 98% of the individual therapy recommendations were accepted and implemented. The tumor board conference presents an optimal possibility for extensive scientific discussions and exchange (92%) and improves advanced educational training (81%). In conclusion, the online tumor conference is feasible and represents a time-saving possibility for gynecological oncologist to receive a treatment recommendation based on the best available clinical and scientific evidence.

Lumbosacral glioblastoma and leptomeningeal gliomatosis complicating the course of a cervicothoracic astrocytoma WHO grade II

CASE REPORT

The reported female patient underwent sub-total resection of an intra-medullary cervicothoracic astrocytoma classified as WHO grade II in 1984 at the age of 18 months and received local irradiation. In 1989, a local recurrence was diagnosed and a partial resection was performed. Sixteen years later, a small recurrent cervicothoracic tumour was found and spinal seeding to the equine nerve roots and the left cerebellar cortex was apparent on MRI. The patient was implanted with a ventriculoperitoneal shunt for a pseudo-tumour cerebri producing papilloedema, which eventually lead to amaurosis. After an extended biopsy, the invasive lumbosacral tumour was classified as glioblastoma multiforme. Two months later, the patient died after rapid progression of the caudal cranial nerve dysfunction.

DISCUSSION AND CONCLUSION

Anaplastic progression and dissemination of spinal astrocytomas even two decades after initial diagnosis and treatment are rare. Therapies and diagnostic follow-up strategies are discussed.

Rechallenge of malignant gliomas with temozolomide —Can it be effective?

2072

Background: No standard treatment of recurrent malignant glioma is established. Moreover, it is unclear if a rechallenge with temozolomide is effective. We present here feasibility and first treatment results of a dose-dense, individually dose adapted 21-day regimen with temozolomide. Methods: 13 consecutive patients with recurrent malignant gliomas (11 glioblastomas [GBM], 1 anaplastic astrocytoma, 1 anaplastic oligodendroglioma) were treated. The basic data are: median time to first relapse 8.3 months; median Karnofsky performance status 60% (7 x 50+60%; 6 x 70–100%); median age 52.2 (32–73) years; gender: 9 males (69%), 4 females (31%). All patients were pretreated with radiochemotherapy and temozolomide 200mg/m2 days 1–5/28 in first line. In eight of the 13 patients, therapy was switched without delay to the dose-dense schedule: temozolomide 100mg/m2 day 1–21/28. During treatment, the dosage was adapted individually, aiming towards total leukocyte counts of approximately 4,000/μL. Results: The 21/28-days regimen was better tolerated than the 5/28-days schedule regarding nausea and fatigue. Blood counts decreased continuously, enabling a gradual dose adaptation. The dosage was kept at 100mg/m2 in 9 patients, reduced to 75 mg/m2 in 3 and gradually increased to 130 mg/m2 in 1 patient. Hematotoxicity was WHO grade 3 in 2, and grade 4 in 1 patient without clinical signs. One patient had a pneumonia WHO grade 4 in the terminal stage of the disease several weeks after discontinuation of the chemotherapy. Response after 2 months was: 3 partial and 1 complete remission (31%; GBM only: 18%), 4 stable diseases (31%), 5 progressive diseases (38%). The progression free survival at 6 months (PFS) was 54.5% (GBM: 44%). In the 9 glioblastoma patients with an observation period of more than 6 months, the median survival time after relapse was 35.8 weeks, median overall survival 18.2 months. Conclusions: Second line treatment with dose dense temozolomide at 100 mg/m2 day 1–21/28 and individual dose adaptation is feasible for recurrent malignant gliomas. Even in this series with relatively unfavorable prognostic criteria, the rate of objective responses and 6-months PFS after rechallenge with temozolomide compares well with other series. The results will be controlled in a prospective study.

No significant financial relationships to disclose.

Characterization of the amplicon on chromosomal segment 4q12 in glioblastoma multiforme

A subset of glioblastomas (GBMs) carry gene amplifications on chromosomal segment 4q12. To characterize this amplicon in detail, we analyzed a set of 100 samples consisting of 65 GBMs, 10 WHO grade III astrocytomas, 12 oligodendrogliomas, and 13 glioma cell cultures. We applied multiplex ligation-dependent probe amplification to determine the gene dosage of PDGFRA, KIT, and KDR and the flanking genes USP46, RASL11B, LNX1, CHIC2, SEC3L1, and IGFBP7. The amplicon was highly variable in size and copy number and extended over a region of up to 5 Mb. Amplifications on 4q12 were observed in 15% of GBMs and 23% of GBM cell cultures but not in 22 other gliomas. We analyzed transcription and translation of some genes within this amplicon. Gene amplification generally correlated with high transcript levels but did not necessarily result in increased protein levels. However, we detected frequent expression of proteins encoded by PDGFRA, KIT, and KDR in GBMs and GBM cell cultures independent of the amplification status. Future treatment of GBM patients may include drugs targeting multiple kinases that are encoded by genes on chromosomal segment 4q12.

Preoperative thrombocytosis predicts poor survival in patients with glioblastoma

Thrombocytosis, which is defined as a platelet count greater than 400 platelets/nl, has been found to be an independent predictor of shorter survival in various tumors. Release of growth factors from tumors has been proposed to increase platelet counts. Preoperative platelet counts and other clinical and hematological parameters were reviewed from the records of 153 patients diagnosed between 1999 and 2004 with histologically confirmed glioblastoma in order to evaluate the prognostic significance of preoperative thrombocytosis in these patients. The relationship between thrombocytosis and survival was initially analyzed in all patients regardless of further therapy. Univariate log-rank tests showed that the median survival time of 29 patients with preoperative thrombocytosis (19%) was significantly shorter (4 months; 95% confidence interval [95% CI], 3-6 months) compared to 124 patients with normal platelet counts (11 months; 95% CI, 8-13 months; p = 0.0006). Multivariate analysis (Cox proportional hazards model) confirmed preoperative platelet count, age, prothrombin time, and activated partial thromboplastin time to be prognostic factors of survival (all p < 0.05). In a subset of patients (only operated patients with radiation therapy with or without additional chemotherapy), survival was likewise significantly shorter when preoperative thrombocytosis was diagnosed (6 months; 95% CI, 4-12 months) compared to patients with normal platelet count (13 months; 95% CI, 11-15 months; p = 0.0359). In multivariate analysis, age, platelet count, preoperative prothrombin time, and degree of tumor resection retained significance as prognostic factors of survival (all p < 0.05). The results of our study demonstrate preoperative thrombocytosis to be a prognostic factor associated with shorter survival time in patients with glioblastoma.

Imaging of brain and brain tumor specimens by time-resolved multiphoton excitation microscopy ex vivo

Multiphoton excitation fluorescent microscopy is a laser-based technology that allows subcellular resolution of native tissues in situ. We have recently applied this technology to the structural and photochemical imaging of cultured glioma cells and experimental gliomas ex vivo. We demonstrated that high microanatomical definition of the tumor, invasion zone, and normal adjacent brain can be obtained down to single-cell resolution in unprocessed tissue blocks. In this study, we used multiphoton excitation and four-dimensional microscopy to generate fluorescence lifetime maps of the murine brain anatomy, experimental glioma tissue, and biopsy specimens of human glial tumors. In murine brain, cellular and noncellular elements of the normal anatomy were identified. Distinct excitation profiles and lifetimes of endogenous fluorophores were identified for specific brain regions. Intracranial grafts of human glioma cell lines in mouse brain were used to study the excitation profiles and fluorescence lifetimes of tumor cells and adjacent host brain. These studies demonstrated that normal brain and tumor could be distinguished on the basis of fluorescence intensity and fluorescence lifetime profiles. Human brain specimens and brain tumor biopsies were also analyzed by multiphoton microscopy, which demonstrated distinct excitation and lifetime profiles in glioma specimens and tumor-adjacent brain. This study demonstrates that multiphoton excitation of autofluorescence can distinguish tumor tissue and normal brain based on the intensity and lifetime of fluorescence. Further technical developments in this technology may provide a means for in situ tissue analysis, which might be used to detect residual tumor at the resection edge.

Time-domain and spectral-domain optical coherence tomography in the analysis of brain tumor tissue

INTRODUCTION

Detection of residual tumor during resection of glial brain tumors remains a challenge because of a low inherent contrast of adjacent edematous brain, the surrounding infiltration zone, and the solid tumor. Therefore, new technologies that may facilitate an intraoperative analysis of the tissue at the resection edge are of great interest to neurosurgeons.

MATERIALS AND METHODS

For ex vivo imaging of gliomas in a mouse model and human biopsy specimens of brain tumors and nervous system tissue we have used a time-domain Sirius 713 Tomograph with a central wavelength of 1,310 nm and a coherence length of 15 microm equipped with a mono mode fiber and a modified optical coherence tomography (OCT) adapter containing a lens system for imaging at a working distance of 2.5 cm. A spectral-domain tomograph using 840 nm and 930 nm superluminescence diodes (SLD) with a central wavelength of 900 nm was used as a second imaging modelity.

RESULTS

Both time-domain and spectral-domain coherence tomography delineated normal brain, the infiltration zone and solid tumor in murine intracerebral gliomas. Histological evaluation of H&E sections parallel to the optical plain demonstrated that tumor areas of less than a millimeter could be detected and that not only solid tumor, but also brain invaded by a low-density single tumor cells produced an OCT signal different from normal brain. Spectral-domain OCT (SD-OCT) demonstrated a significantly more detailed microstructure of tumor and normal brain up to a tissue depth of 1.5-2.0 mm, whereas the interpretation of time-domain OCT (TD-OCT) was difficult at a tissue depth >1.0 mm. Because of rapid scanning times SD-OCT data could be acquired as 3D data maps, which allowed a multi-planar analysis of the tumor to brain interface. Similar to our findings in experimental gliomas, images of human nervous system tissue acquired using SD-OCT showed a characteristic signal of normal brain tissue and a detailed microstructure of tumor parenchyma.

CONCLUSION

Spectral-domain OCT of experimental gliomas and human brain tumor specimens differentiates solid tumor, diffusely invaded brain tissue, and adjacent normal brain based on microstructure and B-scan signal characteristics. In conjunction with the rapid image acquisition rates of SD-OCT, this technology carries the potential of a novel intraoperative imaging tool for the detection of residual tumor and guidance of neurosurgical tumor resections.

Optical coherence tomography for experimental neuroendoscopy

Optical coherence tomography (OCT) is a non-invasive and non-contact imaging technology that has been applied to several biomedical applications. We have recently demonstrated that OCT allows discrimination of tumor adjacent brain, diffuse and solid tumor tissue and that this technology may be used to detect residual tumor within the resection cavity during resection of intrinsic brain tumors. Here we show that an OCT integrated endoscope can image the endoventricular anatomy and other endoscopically accessible structures in a human brain specimen. A Sirius 713 optical coherence tomography device was mounted to a modified rigid endoscope. A formalin-fixed human brain specimen was used to simulate endoscopic visualization of brain anatomy and two specimens of fixed malignant tumors with endoventricular growth patterns. Simultaneous OCT imaging and endoscopic video imaging of the visible spectrum was possible using a graded index rod endoscope. OCT imaging of a human brain specimen in water allowed an in-depth view into structures like the walls of the ventricular system, the choroid plexus or the thalamostriatal vein. OCT further allowed imaging of structures beyond tissue barriers or opaque media. In this fixed specimen OCT allowed discrimination of vascular structures down to a diameter of 50 mum. In vessels larger that 100 mum the lumen could be discriminated and within larger blood vessels a layered structure of the vascular wall as well as endovascular plaques could be visualized. This in vitro pilot study has demonstrated that OCT integrated into neuroendoscopes may add information that cannot be obtained by the video imaging alone. This technology may provide an extra margin of safety by providing cross-sectional images of tissue barriers within optically opaque conditions.

Multiphoton excitation of autofluorescence for microscopy of glioma tissue

OBJECTIVE

Intraoperative detection of residual tumor tissue in glioma surgery remains an important challenge because the extent of tumor removal is related to the prognosis of the disease. Multiphoton excited fluorescence tomography of living tissues provides high-resolution structural and photochemical imaging at a subcellular level. In this conceptual study, we have used multiphoton microscopy and fluorescence lifetime imaging (4D microscopy) to image cultured glioma cell lines, solid tumor, and invasive tumor cells in an experimental mouse glioma model and human glioma biopsy specimens.

MATERIAL AND METHODS

A laser imaging system containing a mode-locked 80 MHz titanium:sapphire laser with a tuning range of 710 to 920 nm, a scan unit, and a time correlated single photon counting board was used to generate autofluorescence intensity images and fluorescence lifetime images of cultured cell lines, experimental intracranial gliomas in mouse brain, and biopsies of human gliomas.

RESULTS

Multiphoton microscopy of native tumor bearing brain provided structural images of the normal brain anatomy at a subcellular resolution. Solid tumor, the tumor-brain interface, and single invasive tumor cells could be visualized. Fluorescence lifetime imaging demonstrated significantly different decay of the fluorescent signal in tumor versus normal brain, allowing a clear definition of the tumor-brain interface based on this parameter. Distinct fluorescence lifetimes of endogenous fluorophores were found in different cellular compartments in cultured glioma cells. The analysis of the relationship between the laser excitation wavelength and the lifetime of excitable fluorophores demonstrated distinct profiles for cells of different histotypes.

CONCLUSION

Multiphoton excited fluorescence of endogenous fluorophores allows structural imaging of tumor and central nervous system histo-architecture at a subcellular level. The analysis of the decay of the fluorescent signal within specific excitation volumes by fluorescent lifetime imaging discriminates glioma cells and normal brain, and the excitation/lifetime profiles may further allow differentiation of cellular histotypes. This technology provides a noninvasive optical tissue analysis that may potentially be applied to an intraoperative analysis of resection plains in tumor surgery.

Synaptic organization in cochlear inner hair cells deficient for the CaV1.3 (alpha1D) subunit of L-type Ca2+ channels

Cochlear inner hair cells (IHCs) release neurotransmitter onto afferent auditory nerve fibers in response to sound stimulation. Normal development and function of inner hair cells require the expression of alpha subunit 1.3 forming L-type voltage-gated Ca(2+) channel (Ca(V)1.3). Here, we used immunohistochemistry and reverse transcription-polymerase chain reaction to study the synaptic organization and expression of large conductance Ca(2+)-activated potassium channels in IHCs of mice lacking the Ca(V)1.3 Ca(2+) channel (Ca(V)1.3(-/-)). Despite the near complete block of evoked afferent synaptic transmission, hair cell ribbon synapses were formed and remained preserved for at least 4 weeks after birth. Moreover, these "silent" afferent synapses held major components of the synaptic machinery such as Bassoon, Piccolo, and CSP. Hence, the block of exocytosis might be solely attributed to the lack of Ca(2+) influx through Ca(V)1.3 channels. Later on, Ca(V)1.3 deficient IHCs subsequently lost their afferent synapses. This was probably due to a secondary degeneration of the postsynaptic spiral ganglion neurons. In line with a prolonged efferent synaptic transmission onto Ca(V)1.3 deficient IHCs, which normally ceases around onset of hearing, we found juxtaposed immunoreactive spots of efferent presynaptic synaptophysin and postsynaptic (IHCs) small conductance Ca(2+)-activated potassium channels (SK channels) up to six weeks after birth. Finally, we show a substantial reduction of mRNA for the alpha subunit of the large conductance Ca(2+)-activated potassium channel (BK) in the apical cochlea, suggesting a reduced transcription of its gene in Ca(V)1.3 deficient IHCs. Ca(V)1.3 deficient IHCs lacked the apical spot-like immunoreactivity of clustered BK channels, which normally contribute to the temporal precision of hair cell afferent synaptic transmission. In summary, these data indicate that the Ca(V)1.3 channels are crucially involved in regulation of the expression of BK and SK channels. Ca(V)1.3 channels seem not to be essential for ribbon synapse formation, but are required for the maintenance of ribbon synapses and spiral ganglion neurons.

Role of microglia in neuronal cell death in prion disease

To elucidate the role played by the prion protein in scrapie pathogenesis, we performed experiments with PrP27-30 isolated from scrapie-infected hamster brains in cell culture and studied in vivo the temporal and spatial correlation between deposition of the disease-associated isoform of the prion protein (PrPSc), microglial activation and neuronal cell death in mice infected with scrapie strains 79A, ME7 and RML. The results presented here show that cellular expression of PrPc and the presence of microglia are necessary for the neurotoxicity of PrPSc in vitro. In vivo, accumulation of protease-resistant prion protein was detected early in the incubation period using the histoblot technique. Microglial activation was also detected early in the incubation period of all models studied. Both the time course and the spatial distribution of microglial activation closely resembled the pattern of PrPSc deposition. Microglial activation clearly preceded the detection of apoptotic neuronal cell death which was assessed using the in situ end-labeling technique (ISEL). Taken together, our results indicate that microglial activation is involved in the neurotoxicity of PrPSc both in vitro and in vivo.