Yoshinori Kajiwara

Monoallelic BUB1B mutations and defective mitotic-spindle checkpoint in seven families with premature chromatid separation (PCS) syndrome.

Cancer‐prone syndrome of premature chromatid separation (PCS syndrome) with mosaic variegated aneuploidy (MVA) is a rare autosomal recessive disorder characterized by growth retardation, microcephaly, childhood cancer, premature chromatid separation of all chromosomes, and mosaicism for various trisomies and monosomies. Biallelic BUB1B mutations were recently reported in five of eight families with MVA syndrome (probably identical to the PCS syndrome). We here describe molecular analysis of BUB1B (encoding BubR1) in seven Japanese families with the PCS syndrome. Monoallelic BUB1B mutations were found in all seven families studied: a single‐base deletion (1833delT) in four families; and a splice site mutation, a nonsense mutation, and a missense mutation in one family each. Transcripts derived from the patients with the 1833delT mutation and the splice site mutation were significantly reduced, probably due to nonsense‐mediated mRNA decay. No mutation was found in the second alleles in the seven families studied, but RT‐PCR of BUB1B and Western blot analysis of BubR1 indicated a modest decrease of their transcripts. BubR1 in the cells from two patients showed both reduced protein expression and diminished kinetochore localization. Their expression level of p55cdc, a specific activator of anaphase‐promoting complex, was normal but its kinetochore association was abolished. Microcell‐mediated transfer of chromosome 15 (containing BUB1B) into the cells restored normal BubR1 levels, kinetochore localization of p55cdc, and the normal responses to colcemid treatment. These findings indicate the involvement of BubR1 in p55cdc‐mediated mitotic checkpoint signaling, and suggest that >50% decrease in expression (or activity) of BubR1 is involved in the PCS syndrome.

Lymphomas and glioblastomas: Differences in the apparent diffusion coefficient evaluated with high b-value diffusion-weighted magnetic resonance imaging at 3 T

BACKGROUND AND PURPOSE As the usefulness of the apparent diffusion coefficient (ADC) obtained from diffusion-weighted images (DWI) for the differential diagnosis between glioblastoma and primary central nervous system lymphoma is controversial, we assessed whether high b-value DWI at b 4000 s/mm(2) could discriminate between glioblastoma and lymphoma. We also compared the power of high- and standard b-value (b-4000, b-1000) imaging on a 3-Tesla (3T) magnetic resonance (MR) instrument. MATERIALS AND METHODS This study was approved by our Institutional Review Board. We acquired DWI at 3T with b = 1000 and b = 4000 s/mm(2) in 10 patients with lymphoma and 14 patients with glioblastoma. The ADC was measured by placing multiple regions of interest (ROI) on ADC maps of the site of enhanced lesions on contrast-enhanced T1-weighted MR images. We avoided hemorrhagic and cystic lesions by using T1-, T2-, FLAIR-, and T2* MR images. The ADC values of each tumor were determined preoperatively from several ROI and expressed as the minimum-, mean-, and maximum ADC value (ADC(MIN), ADC(MEAN), ADC(MAX)). We evaluated the relationship between ADCs and histological information including tumor cellularity. RESULTS All ADC values were statistically associated with tumor cellularity. ADC(MIN) at b-4000 was associated with tumor cellularity more significantly than ADC(MIN) at b-1000. All ADC values were lower for lymphoma than glioblastoma and the statistical difference was larger at b = 4000- than b = 1000 s/mm(2). According to the results of discriminant analysis, the log likelihood was greatest for ADC(MIN) at b = 4000. At a cut-off value of ADC(MIN) = 0.500 × 10(-3)mm(2)/s at b-4000 it was possible to differentiate between lymphoma and glioblastoma (sensitivity 90.9%, specificity 91.7%). CONCLUSIONS Calculating the ADC value is useful for distinguishing lymphoma from glioblastoma. The lowest degree of overlapping and a better inverse correspondence with tumor cellularity were obtained with ADC(MIN) at b-4000 s/mm(2) at 3T MRI.

Intravenous administration of bone marrow stromal cells increases survivin and Bcl-2 protein expression and improves sensorimotor function following ischemia in rats

Intravenous administration of bone marrow stromal cells (MSCs) in animal models with focal cerebral ischemia has been found to be effective in attenuating neuronal damage. We examined whether intravenously transplanted MSCs alters expression of apoptosis-related proteins. Fisher-344 rats were subjected to 90-min middle cerebral artery occlusion (MCAO). The experimental groups were: (I) vehicle group, with intravenous injection of phosphate-buffered saline (PBS) 3h after MCAO; and (II) transplant group, with intravenous injection of MSCs (3x10(6)cells) 3h after MCAO. Neurological function of rats was evaluated using modified neurological severity score (mNSS) and Rotor-rod Motor Test (RMT). Rats were sacrificed on 1st, 3rd and 7th days of MCAO, and coronal brain sections were stained immunohistochemically to identify the apoptosis-related proteins, namely survivin and Bcl-2. We also examined Terminal Deoxynucleotidyl Transferase-Mediated dUTP-biotin Nick End Labeling (TUNEL)-positive cells on 3rd day of MCAO. Functional recovery according to mNSS and RMT was significantly better in the transplant group as compared with the vehicle group (P<0.05). Immunohistochemical analysis revealed significant expression of survivin on 3rd day and Bcl-2 on 1st and 3rd days in the transplant group. The vehicle group displayed significantly more TUNEL-positive cells than the transplant group on 3rd day (P<0.05). These results suggest that intravenous transplantation of MSCs prevents down-regulation of survivin and Bcl-2 preventing apoptosis and cell death in the ischemic brain leading to motor and sensory function recovery.

Centrosome amplification induced by survivin suppression enhances both chromosome instability and radiosensitivity in glioma cells

Glioblastoma is characterised by invasive growth and a high degree of radioresistance. Survivin, a regulator of chromosome segregation, is highly expressed and known to induce radioresistance in human gliomas. In this study, we examined the effect of survivin suppression on radiosensitivity in malignant glioma cells, while focusing on centrosome aberration and chromosome instability (CIN). We suppressed survivin by small interfering RNA transfection, and examined the radiosensitivity using a clonogenic assay and a trypan blue exclusion assay in U251MG (p53 mutant) and D54MG (p53 wild type) cells. To assess the CIN status, we determined the number of centrosomes using an immunofluorescence analysis, and the centromeric copy number by fluorescence in situ hybridisation. As a result, the radiosensitisation differed regarding the p53 status as U251MG cells quickly developed extreme centrosome amplification (=CIN) and enhanced the radiosensitivity, while centrosome amplification and radiosensitivity increased more gradually in D54MG cells. TUNEL assay showed that survivin inhibition did not lead to apoptosis after irradiation. This cell death was accompanied by an increased degree of aneuploidy, suggesting mitotic cell death. Therefore, survivin inhibition may be an attractive therapeutic target to overcome the radioresistance while, in addition, proper attention to CIN (centrosome number) is considered important for improving radiosensitivity in human glioma.

Role of perfusion-weighted imaging at 3 T in the histopathological differentiation between astrocytic and oligodendroglial tumors

OBJECTIVE The differentiation of oligodendroglial tumors from astrocytic tumors is important clinically, because oligodendroglial tumors are more chemosensitive than astrocytic tumors. This study was designed to clarify the usefulness of 3T MR perfusion imaging (PWI) in the histopathological differentiation between astrocytic and oligodendroglial tumors. This is because there is a growing interest in the diagnostic performance of 3T MR imaging, which has the advantages of a higher signal-to-noise ratio (SNR) and greater spatial and temporal resolution. MATERIALS AND METHODS This study retrospectively included 24 consecutive patients with supratentorial, WHO grade II and III astrocytic and oligodendroglial tumors (7 astrocytic, 10 oligoastrocytic, and 7 oligodendroglial tumors) that were newly diagnosed and resected between November 2006 and December 2009 at Hiroshima University Hospital. These patients underwent dynamic susceptibility contrast-enhanced (DSC) PWI relative cerebral blood volume (rCBV) measurements before treatment. Astrocytic tumors were designated as the astrocytic group, and oligoastrocytic and oligodendroglial tumors as the oligodendroglial group. The regions of interest with the maximum rCBV values within the tumors were normalized relative to the contra-lateral white matter (rCBVmax). RESULTS The average rCBVmax of astrocytic tumors (2.01±0.68) was significantly lower than that of the oligoastrocytic (4.60±1.05) and oligodendroglial tumors (6.17±0.867) (P<0.0001). A cut-off value of 3.0 allowed to differentiate the oligodendroglial group from the astrocytic group at 100% sensitivity and 87.5% specificity. CONCLUSION The rCBVmax values obtained from 3T MR PWI may be useful as an adjunct to the postoperative histopathological diagnosis of glioma patients.

Glioblastoma treated with postoperative radio-chemotherapy : Prognostic value of apparent diffusion coefficient at MR imaging

PURPOSE To retrospectively evaluate whether the mean, minimum, and maximum apparent diffusion coefficient (ADC) of glioblastomas obtained from pretreatment MR images is of prognostic value in patients with glioblastoma. MATERIALS AND METHODS The institutional review board approved our study and waived the requirement for informed patient consent. Between February 1998 and January 2006, 33 patients (24 males, 9 females; age range 10-76 years) with supratentorial glioblastoma underwent pretreatment magnetic resonance (MR) imaging. The values of the mean, minimum, and maximum ADC (ADC(mean), ADC(MIN), and ADC(MAX), respectively) of each tumor were preoperatively determined from several regions of interest defined in the tumors. After surgical intervention, all patients underwent irradiation and chemotherapy performed according to our hospital protocol. The patient age, symptom duration, Karnofsky performance scale score, extent of surgery, and ADC were assessed using factor analysis of overall survival. Prognostic factors were evaluated using Kaplan-Meier survival curves, the log-rank test, and multiple regression analysis with the Cox proportional hazards model. RESULTS Likelihood ratio tests confirmed that ADC(MIN) was the strongest among the three prognostic factors. Total surgical removal was the most important predictive factor for overall survival (P<0.01). ADC(MIN) was also statistically correlated with overall survival (P<0.05) and could be used to classify patients into different prognostic groups. Interestingly, ADC(MIN) was also the strongest prognostic factor (P<0.01) in the group of patients in whom total tumor removal was not possible. CONCLUSION The ADC(MIN) value obtained from pretreatment MR images is a useful clinical prognostic biomarker in patients with glioblastoma.

Preoperative histological grading of meningiomas using apparent diffusion coefficient at 3T MRI

PURPOSE We assessed whether a high b-value DWI at b=4000s/mm(2) would discriminate the histopathological differentiation of the tumor grade of meningiomas, and also focused on the relationship between radiologic features and the tumor grade. MATERIALS AND METHODS We acquired DWI at 3T with b=1000 and b=4000s/mm(2) in 77 patients (42, 31 and 4 patients were WHO grades I (G1), II (G2), and III (G3), respectively). The apparent diffusion coefficient (ADC) was measured by placing multiple regions of interest (ROIs) on ADC maps. The ADC values of each tumor were determined preoperatively from several ROIs, and expressed as the minimum (ADCMIN), mean (ADCMEAN), and maximum absolute values (ADCMAX). We evaluated the relationship between ADCs and histological findings, and assessed the radiologic features such as tumor location, tumor size, presence/absence of peritumoral edema, shape of the tumor, presence/absence of bone destruction or hyperplasia, status of contrast enhancement, presence/absence of calcification and cyst. RESULTS ADCs of the meningiomas were inversely correlated with the histological grade of meningiomas. According to results of the discriminant analysis, the apparent log likelihood value was greatest for ADCMIN at b=4000. Furthermore, only the ADCMIN value at b=4000 was significantly correlated with the histological grade of meningiomas when we performed a multiple logistic regression analysis to identify the significant independent factors such as shape of tumor, presence/absence of bone destruction, status of contrast enhancement, presence/absence of cyst and ADCMIN at b=4000. CONCLUSION A meningioma with a low ADCMIN at a high b-value might imply a high-grade meningioma.

Good Clinical Course in Infants with Desmoplastic Cerebral Neuroepithelial Tumor Treated by Surgery Alone

We investigated why surgery alone provides for a benign clinical course in patients with desmoplastic infantile ganglioglioma and astrocytoma (DIG/A). The clinical course of 4, less than six-month-old girls, surgically treated at our institutions, was evaluated retrospectively. All presented with the clinical symptom of increasing head circumference. CT and MRI scans revealed a solid tumor attached to the dura that was surrounded by large, multiple cysts, in fronto-temporo-parietal lobe. Gross total removal succeeded in all 4 cases because the solid components of the tumor were very firm in contrast to the soft adjacent brain tissue. Microscopically, the surgical specimens consisted almost entirely of dense fibrous connective tissue containing generally elongate cells with inconspicuous cytoplasm. Most of these cells were immunopositive for GFAP. There was no evidence of tumor cells in the cyst wall. In 3 cases, some small neurons were positive for neurofilament immunostain. A high proportion of undifferentiated small cells in a less demoplastic area far from the dura were immunopositive for MIB-1. All of the 4 patients have been free of recurrence for more than five years. In patients with DIG/A, there are 5 reasons for a good clinical course. [1] At surgery, the tumor margin is clearly discernible because of the difference between the solid tumor and the soft adjacent brain tissue. [2] The tumor is located in the superficial cerebral hemisphere. [3] Large, multiple cysts surround the tumor. [4] The growth point appears to be adjacent to the cysts. [5] The cyst walls are free of invading tumor cells.

Geminin: A good prognostic factor in high‐grade astrocytic brain tumors

Geminin is a nuclear protein that belongs to the DNA replication inhibitor group. It inhibits DNA replication by preventing Cdt1 from loading minichromosome maintenance protein onto chromatin, as is required for DNA replication. For this study, the authors investigated geminin expression in high‐grade astrocytic tumors, including anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM), with a view to predicting clinical outcomes on this basis in patients with these malignant brain tumors.

Cytoplasmic, but not nuclear, p16 expression may signal poor prognosis in high-grade astrocytomas.

SummaryBackgroundThe negative consequences of the cytoplasmic localization of p16 in patients with high-grade astrocytomas, on their prognosis, was investigated.Methodsp16 Expression was examined in 20 anaplastic astrocytoma and 42 glioblastoma patients by immunohistochemical analysis, and the relationship between both cytoplasmic and nuclear p16 expression and prognosis analyzed.ResultsThe cytoplasmic expression of p16 statistically correlated with poor prognosis. On the other hand, no correlation was observed between p16 nuclear expression and patient survival.ConclusionThe cytoplasmic immunoreactivity of p16 appears to be an unfavorable prognostic indicator in high-grade astrocytoma patients. The localization of p16 expression should be determined when evaluating the prognosis of these patients.