Wai Sang Poon

Detection of Multiple Gene Amplifications in Glioblastoma Multiforme Using Array-Based Comparative Genomic Hybridization

We have used a new method of genomic microarray to investigate amplification of oncogenes throughout the genome of glioblastoma multiforme (GBM). Array-based comparative genomic hybridization (array CGH) allows for simultaneous examination of 58 oncogenes/amplicons that are commonly amplified in various human cancers. Amplification of multiple oncogenes in human cancers can be rapidly determined in a single experiment. Tumor DNA and normal control DNA were labeled by nick translation with green- and red-tagged nucleotides, respectively. Instead of hybridizing to normal metaphase chromosomes in conventional comparative genomic hybridization (CGH), the probes of the mixed fluorescent labeled DNA were applied to genomic array templates comprised of P1, PAC, and BAC clones of 58 target oncogenes. The baseline for measuring deviations was established by performing a series of independent array CGH using test and reference DNA made from normal individuals. In the present study, we examined fourteen GBMs (seven cell lines and seven tumours) with CGH and array CGH to reveal the particular oncogenes associated with this cancer. High-level amplifications were identified on the oncogenes/amplicons CDK4, GLI, MYCN, MYC, MDM2, and PDGFRA. The highest frequencies of gains were detected on PIK3CA (64.3%), EGFR (57.1%), CSE1L (57.1%), NRAS (50%), MYCN (42.9%), FGR (35.7%), ESR (35.7%), PGY1 (35.7%), and D17S167 (35.7%). These genes are suggested to be involved in the GBM tumorigenesis.

Spontaneous Intracranial Hemorrhage: Which Patients Need Diagnostic Cerebral Angiography?: A Prospective Study of 206 Cases and Review of the Literature

BACKGROUND AND PURPOSE In spontaneous intracerebral hemorrhage (ICH), the site, age of the patients, and preexisting hypertension are important factors in determining the possibility of finding an underlying vascular abnormality by cerebral angiography. To what extent these three factors affect the indication for angiography remains controversial. A prospective study was carried out to correlate the angiographic findings with these three factors. METHODS Two hundred six consecutive spontaneous ICH cases with an age range from 5 to 79 years (median, 45) were investigated with CT and cerebral angiography over a 3-year period (April 1993 through March 1996). Exclusion criteria were (1) poor surgical risk or severely neurologically disabled patients, (2) refusal of angiography, (3) patients in whom severe coagulopathy accounted for the hemorrhage, (4) bleeding into tumor, or (5) subarachnoid hemorrhage-predominant cases. RESULTS Angiographic yield (the frequency of positive angiography in a defined patient group) was significantly higher in patients (1) at or below the median age of 45 than those above (53/105, 50%, versus 18/101, 18%; P < .001) and (2) without preexisting hypertension than those with (64/145, 44%, versus 5/58, 9%; P < .001). The correlation of age and preexisting hypertension to angiographic yield was independent (logistic regression coefficients -0.056 and -1.59 and SE 0.12 and 0.515, respectively, both P < .001). In patients of the younger age group without preexisting hypertension, angiographic yield was 48% in putaminal, thalamic, or posterior fossa ICH and 65% in lobar ICH. In the older hypertensive patients, the yields were 0% and 10%, respectively. However, in patients with isolated intraventricular hemorrhage, most were normotensive and the yield was high in both age groups (67% versus 63%). CONCLUSION Diagnostic cerebral angiography should be considered for all spontaneous ICH patients except those over 45 years old with preexisting hypertension in thalamic, putaminal, or posterior fossa hemorrhage.

Heterogeneous responses of aquaporin-4 in oedema formation in a replicated severe traumatic brain injury model in rats

Aquaporin-4 (AQP4) is the most abundant water channel in the rat brain. In this study, the distribution pattern and mRNA expression levels of AQP4 were examined in a severe traumatic brain injury model by immunohistochemistry and reverse transcription-polymerase chain reaction. Oedema formation and blood-brain barrier (BBB) integrity were assessed by wet-dry weight measurements and immunostaining of endogenous IgG respectively. In the oedematous contusional cortex with impaired BBB integrity, negative immunostaining of AQP4 and down-regulation of its mRNA level were identified (P<0.05) at 1 day post-injury, while in other oedematous regions of the injured brain where BBB was intact, there was no significant change in the AQP4 expression level. This heterogeneous pattern of AQP4 responses can be interpreted as follows: focal brain injury (such as a contusion) with impaired BBB resulting in vasogenic oedema is associated with reduction of AQP4 expression, whereas, in cytotoxic oedema, associated with diffuse brain injury with intact BBB, changes in AQP4 expression are not significant. This study provides basic information for investigating new treatments for traumatic brain oedema.

Intravenous Magnesium Sulphate for Aneurysmal Subarachnoid Hemorrhage (IMASH) A Randomized, Double-Blinded, Placebo-Controlled, Multicenter Phase III Trial

Background and Purpose— Pilot clinical trials using magnesium sulfate in patients with acute aneurysmal subarachnoid hemorrhage have reported trends toward improvement in clinical outcomes. This Phase III study aimed to compare intravenous magnesium sulfate infusion with saline placebo among such patients. Methods— We recruited patients with aneurysmal subarachnoid hemorrhage within 48 hours of onset from 10 participating centers. The patients were randomly assigned to magnesium sulfate infusion titrated to a serum magnesium concentration twice the baseline concentration or saline placebo for 10 to 14 days. Patients and assessors were blinded to treatment allocation. The study is registered at www.strokecenter.org/trials (as Intravenous Magnesium Sulphate for Aneurysmal Subarachnoid Hemorrhage [IMASH]) and www.ClinicalTrials.gov (NCT00124150). Results— Of the 327 patients recruited, 169 were randomized to receive treatment with intravenous magnesium sulfate and 158 to receive saline (placebo). The proportions of patients with a favorable outcome at 6 months (Extended Glasgow Outcome Scale 5 to 8) were similar, 64% in the magnesium sulfate group and 63% in the saline group (OR, 1.0; 95% CI, 0.7 to 1.6). Secondary outcome analyses (modified Rankin Scale, Barthel Index, Short Form 36, and clinical vasospasm) also showed no significant differences between the 2 groups. Predefined subgroups included age, admission World Federation of Neurological Surgeons grade, pre-existing hypertension, intracerebral hematoma, intraventricular hemorrhage, location of aneurysm, size of aneurysm, and mode of aneurysm treatment. In none of the subgroups did the magnesium sulfate group show a better outcome at 6 months. Conclusions— The results do not support a clinical benefit of intravenous magnesium sulfate infusion over placebo infusion in patients with acute aneurysmal subarachnoid hemorrhage.

Genetic alterations in pediatric high-grade astrocytomas

High-grade astrocytomas are tumors that are uncommon in children. Relatively few studies have been performed on their molecular properties and so it is not certain whether they follow different genetic pathways from those described in adult diffuse astrocytomas. In this study, we evaluated 24 pediatric high-grade astrocytomas (11 anaplastic astrocytomas and 13 glioblastomas) all of which were sporadic and primary. We studied mutations of p53, phosphatase and tensin homolog (PTEN), loss of heterozygosity (LOH) of chromosomes 17p13, 9p21 and 10q23-25, amplification of epidermal growth factor receptor (EGFR), and overexpression of EGFR and p53 protein. In addition, we searched for microsatellite instability (MSI) by using MSI sensitive and specific microsatellite markers. p53 mutations were found in 38% (9/24) of the high-grade astrocytomas and all brain stem tumors except 2 (71%, 5/7) had p53 mutations. PTEN mutations were found in 8% (2/24) of high-grade astrocytomas. However, no EGFR amplification was found in any of them. LOH was found at 17p13.1 in 50% (3/6 informative tumors), 9p21 in 83% (5/6 informative tumors), and 10q23-25 in 78% (7/9 informative tumors). Four tumors showed MSI, and 2 of them that showed widespread MSI were regarded as tumors with replication error (RER+) phenotype. All 4 tumors with MSI showed concurrent LOH of 9p21 and 10q23-25. Combining gene alterations, LOH, MSI, and gene mutations, inactivation of both alleles of PTEN and p53 was found in 57% (4/7 informative tumors) and 50% (3/6 informative tumors) of the cases respectively. We conclude that development of pediatric high-grade astrocytomas may follow pathways different from the primary or secondary paradigm of adult glioblastomas. In a subset of these tumors, genomic instability was also implicated.

The role of computed tomographic angiography in the diagnosis of intracranial aneurysms and emergent aneurysm clipping.

Conventional cerebral angiography has always been regarded as the gold standard for intracranial aneurysm detection. However, conventional angiography has the disadvantages of being invasive and time consuming. We present here 30 patients who underwent computed tomographic angiography (CTA) with three-dimensional reconstruction for the detection of intracranial aneurysms. All of these patients had subarachnoid hemorrhage or suspected intracranial aneurysms. CTA was performed in all patients with the use of a General Electric Hispeed Advantage helical scanner. Iohexol, 135 ml, was used as the contrast agent. Twenty-five patients also underwent conventional angiography for comparison. The five patients who underwent CTA only did not have conventional angiography because of poor clinical condition, and four of them subsequently died. Five patients had subarachnoid hemorrhage, but the results of both CTA and conventional angiography were negative for aneurysms. One patient had an incidental finding of a 3-mm left posterior communicating artery aneurysm on CTA, which was confirmed by conventional angiography. In the remaining 19 patients, 19 saccular aneurysms and 1 fusiform aneurysm were detected by CTA. Locations and sizes were confirmed by conventional angiography in all except two. The first exception was a patient who had a 2.5-mm anterior communicating artery aneurysm detected by CTA but not by conventional angiography. Surgical exploration confirmed the CTA diagnosis. The other exception was a patient in whom a 2-mm right posterior communicating artery aneurysm was detected by CTA but in whom conventional angiography showed a 2-mm left posterior communicating artery aneurysm. Unfortunately, there was no surgical confirmation in this case because the family of the patient refused surgery. Our results have demonstrated that CTA is a quick, reliable, and relatively simple diagnostic tool for intracranial aneurysms. In an emergent situation, such as a deteriorating patient with a hematoma, it is superior to either empiric exploration or infusion computed tomographic scans because it delineates the orientation and configuration of the aneurysm and its associated vascular anatomy.

Intravenous magnesium sulfate after aneurysmal subarachnoid hemorrhage: a prospective randomized pilot study.

We performed a randomized, double-blind, pilot study on magnesium sulfate (MgSO4) infusion for aneurysmal subarachnoid hemorrhage (SAH). Sixty patients with SAH were randomly allocated to receive either MgSO4 80 mmol/day or saline infusion for 14 days. Patients also received intravenous nimodipine. Episodes of vasospasm were treated with hypertensive and hypervolemic therapy. Neurologic status was assessed 6 months after hemorrhage using the Barthel index and Glasgow Outcome Scale. Incidences of cardiac and pulmonary complications were also recorded. Patient characteristics, severity of SAH, and surgical treatment did not differ between groups. The incidence of symptomatic vasospasm decreased from 43% in the saline group to 23% in patients receiving MgSO4 infusion, but it did not reach statistical significance, P=0.06. For patients who had transcranial Doppler-detected vasospasm, defined as mean flow velocity >120 cm/s and a Lindegaard index >3, the duration was shorter in the magnesium group compared with controls (P<0.01). There was, however, no difference between groups in functional recovery or Glasgow Outcome Scale score. The incidence of adverse events such as brain swelling, hydrocephalus, and nosocomial infection was also similar in patients receiving MgSO4 or saline. In this small pilot study, MgSO4 infusion for aneurysmal SAH is feasible. On the basis of the preliminary data, a larger study recruiting approximately 800 patients is required to test for a possible neuroprotective effect of magnesium after SAH.

Does intensive rehabilitation improve the functional outcome of patients with traumatic brain injury (TBI)? A randomized controlled trial

Objective: To evaluate the effects of an increase in the intensity of rehabilitation on the functional outcome of patients with traumatic brain injury (TBI). Design and methods: Sixty-eight patients (age 12–65 years) with moderate-to-severe TBI were included. They were randomized into high (4-hour/day) or control (2-hour/day) intensity rehabilitation programmes at an average of 20 days after the injury. The programmes ended when the patients achieved independence in daily activities or when 6 months had passed. Outcome and results: No significant differences were found in the Functional Independence Measure (FIM) (primary outcome) and Neurobehavioural Cognitive Status Examination (NCSE) total scores between the two groups. There were significantly more patients in the high intensity group than in the control group who achieved a maximum FIM total score at the third month (47% vs. 19%, p = 0.015) and a maximum Glasgow Outcome Scale (GOS) score at the second (28% vs. 8%, p = 0.034) and third months (34% vs. 14%, p = 0.044). Conclusions: Early intensive rehabilitation may improve the functional outcome of patients with TBI in the early months post-injury and hence increase the chance of their returning to work early. Intensive rehabilitation in this study speeded up recovery rather than changed the final outcome.

Transcriptional and epigenetic regulation of human microRNAs

MicroRNAs (miRNAs) are members of non-coding RNAs. They are involved in diverse biological functions. MiRNAs are precisely regulated in a tissue- and developmental-specific manner, but dysregulated in many human diseases, in particular cancers. Transcriptional regulation, post-transcriptional regulation, as well as genetic alterations, are the three major mechanisms controlling the spatial and temporal expression of miRNAs. Emerging evidence now indicates that transcriptional and epigenetic regulations play major roles in miRNA expression. This review summarizes the current knowledge and discusses the future challenges.

The impact of teleradiology on the inter-hospital transfer of neurosurgical patients

The aim of this study was to examine the role of teleradiology in the management of inter-hospital transfer of neurosurgical patients, especially in terms of safety and early therapeutic interventions. Data were collected prospectively, comparing events during the inter-hospital transfer of patients from a district general hospital to a tertiary neurosurgical centre, before and after teleradiology became available. From March to December 1995, 50 referrals made without teleradiology were compared with 66 referrals after teleradiology installation. Our results showed that for patients referred with teleradiologic images, unnecessary transfers were reduced (21%), more therapeutic measures before transfer were implemented (27% vs 20%, p = 0.41), adverse events occurring during transfer were significantly reduced (8% vs 32%, p = 0.002), and transfer time was shortened (72 min vs 80 min, p = 0.38). The potential advantages of this system in facilitating safer transfers and faster management of neurosurgical emergencies therefore merit further attention.