Masashi Kinoshita

Identification of tumor-initiating cells in a highly aggressive brain tumor using promoter activity of nucleostemin

Controversy remains over whether the cancer stem cell (CSC) theory applies to all tumors. To determine whether cells within a highly aggressive solid tumor are stochastically or hierarchically organized, we combined a reporter system where the nucleostemin (NS) promoter drives GFP expression (termed NS-GFP) with a mouse brain tumor model induced by retroviral Ras expression on a p16Ink4a/p19Arf-deficient background. The NS-GFP system allowed us to monitor the differentiation process of normal neural stem/precursor cells by analyzing GFP fluorescence intensity. In tumor-bearing mice, despite the very high frequency of tumorigenic cells, we successfully identified the NS-GFP+ cells as tumor-initiating cells (T-ICs). The clonal studies conclusively established that phenotypical heterogeneity can exist among the cells comprising a genetically homogeneous tumor, suggesting that this aggressive brain tumor follows the CSC model. Detailed analyses of the NS-GFP+ brain tumor cells revealed that T-ICs showed activation of the receptor tyrosine kinase c-Met, which functions in tumor invasiveness. Thus, the NS-GFP system provides a powerful tool to elucidate stem cell biology in normal and malignant tissues.

Association fibers connecting the Broca center and the lateral superior frontal gyrus: a microsurgical and tractographic anatomy.

OBJECT Recently, intraoperative mapping has disclosed that, in addition to the classic language centers (that is, the Broca and Wernicke centers), other cortical regions may also play an important role in language organization. In the prefrontal cortex, although the lateral superior frontal gyrus (LSFG) could have language-related functions, there are no detailed reports that demonstrate the anatomical connection between the LSFG and other well-known language cortices, such as the Broca center. To show the existence of the structural connection, white matter association fibers between the inferior frontal gyrus (IFG) and the LSFG were examined using fiber dissection (FD) and diffusion tensor (DT) imaging-based tractography. METHODS Eight cadaveric cerebral hemispheres were dissected to reveal the association fibers between the IFG and LSFG. The DT imaging-based tractography studies targeting the prefrontal cortex were obtained in 53 right-handed patients who had no organic cerebral lesions. RESULTS The association fiber tract between Brodmann area 44/45 (the Broca center in the dominant hemisphere) and LSFG were detected in all specimens by FD. In the DT imaging-based tractography studies, the tract was identified in all patients bilaterally, except for the 4 in whom the tract was detected only in the left hemisphere. This tract was spread significantly wider in the left than in the right hemisphere, and left lateralization was evident in male patients. CONCLUSIONS Based on its character, this tract was named the Broca-LSFG pathway. These findings suggest a close relationship between this pathway and language organization. The structural anatomy of the Broca-LSFG pathway may explain speech disturbances induced by LSFG stimulation that are sometimes observed during intraoperative language mapping.

Functional Reorganization in the Patient with Progressing Glioma of the Pure Primary Motor Cortex: A Case Report with Special Reference to the Topographic Central Sulcus Defined by Somatosensory-Evoked Potential

BACKGROUND The concept of human brain reorganization due to slow-growing lesions, including low-grade glioma, has been gradually and generally accepted. However, few cases have been reported in which the reorganization, especially in the topographic pure primary motor cortex, was observed during brain surgery. We report a case of slow-growing oligodendroglioma located in the pure primary motor cortex, as detected by magnetic resonance imaging that could be resected in part thanks to the brain plasticity. In addition, we describe a pitfall of topographic guidance using somatosensory-evoked potential (SEP) monitoring. CASE DESCRIPTION A 36-year-old right-handed patient underwent resection of a gradually growing oligodendroglioma located in the right primary motor cortex, with no other adjacent lesions, 8 years after the initial biopsy. The central sulcus was defined with intraoperative SEP monitoring in both operations. Based on the findings of the intraoperative direct electrical stimulation under awake craniotomy, we suspect that motor function shifted posteriorly and reorganized beyond the central sulcus. CONCLUSIONS Pure primary motor cortex could be reorganized by its own lesion. In reorganized brain, topographic central sulcus defined based on SEP findings may be an inappropriate guidance to estimate true functional area. In such a condition, intraoperative direct electrical stimulation under awake craniotomy makes it feasible to resect pure primary motor cortex invaded by tumors.

Predictive value of fractional anisotropy of the arcuate fasciculus for the functional recovery of language after brain tumor resection: a preliminary study.

OBJECTIVE The arcuate fasciculus has been recognized as an important pathway for language processing. Brain tumors located in proximity to the fasciculus frequently cause preoperative language impairment, and in some cases, no language recovery occurs after tumor resection. No predictive value has been presented for possible postoperative language recovery after tumor resection. The aim of this study is to analyze the preoperative state of the arcuate fasciculus in the patients with brain tumor from the perspective of its usefulness as a predictive factor for postoperative recovery of language functions. METHODS For 12 right-handed patients with brain tumors in the left hemisphere, preoperative arcuate fasciculi were analyzed with fractional anisotropy (FA) of the diffusion tensor imaging (DTI) tractography. Language functions were evaluated pre- and postoperatively by using the Western Aphasia Battery (WAB). The preoperative value of the FA of the arcuate fasciculus on the lesion side was examined in relation with the language recovery. RESULTS There was a positive relationship between preoperative increasing values of the FA of the left arcuate fasciculus and improvement of the postoperative total WAB score (p=0.0056), and the scores of the naming (p=0.018), reading (p=0.029), and writing subcategories (p=0.012) CONCLUSION: The preoperative increasing value of the FA of the arcuate fasciculus in the dominant hemisphere could be a predictor for postoperative language recovery following tumor resection. Meticulous procedure should be performed especially in the cases with higher FA of the arcuate fasciculus harboring high possibility of language recovery.

Chronic spatial working memory deficit associated with the superior longitudinal fasciculus: a study using voxel-based lesion-symptom mapping and intraoperative direct stimulation in right prefrontal glioma surgery

OBJECTIVE Although the right prefrontal region is regarded as a silent area, chronic deficits of the executive function, including working memory (WM), could occur after resection of a right prefrontal glioma. This may be overlooked by postoperative standard examinations, and the disabilities could affect the patients professional life. The right prefrontal region is a part of the frontoparietal network and is subserved by the superior longitudinal fasciculus (SLF); however, the role of the SLF in spatial WM is unclear. This study investigated a persistent spatial WM deficit in patients who underwent right prefrontal glioma resection, and evaluated the relationship between the spatial WM deficit and the SLF. METHODS Spatial WM was examined in 24 patients who underwent prefrontal glioma resection (right, n = 14; left, n = 10) and in 14 healthy volunteers using a spatial 2-back task during the long-term postoperative period. The neural correlates of spatial WM were evaluated using lesion mapping and voxel-based lesion-symptom mapping. In addition, the spatial 2-back task was performed during surgery under direct subcortical electrical stimulation in 2 patients with right prefrontal gliomas. RESULTS Patients with a right prefrontal lesion had a significant chronic spatial WM deficit. Voxel-based lesion-symptom mapping analysis revealed a significant correlation between spatial WM deficit and the region that overlapped the first and second segments of the SLF (SLF I and SLF II). Two patients underwent awake surgery and had difficulties providing the correct responses in the spatial 2-back task with direct subcortical electrical stimulation on the SLF I, which was preserved and confirmed by postoperative diffusion tensor imaging tractography. These patients exhibited no spatial WM deficits during the postoperative immediate and long-term periods. CONCLUSIONS Spatial WM deficits may persist in patients who undergo resection of the tumor located in the right prefrontal brain parenchyma. Injury to the dorsal frontoparietal subcortical white matter pathway, i.e., the SLF I or SLF I and II, could play a causal role in this chronic deficit. A persistent spatial WM deficit, without motor and language deficits, could affect the professional life of the patient. In such cases, awake surgery would be useful to detect the spatial WM network with appropriate task during tumor exploration.

Correlation between language function and the left arcuate fasciculus detected by diffusion tensor imaging tractography after brain tumor surgery

OBJECT Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language-processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery. METHODS Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB). RESULTS After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039). CONCLUSIONS The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.

What Bone Part Is Important to Remove in Accessing the Suprachiasmatic Region with Less Frontal Lobe Retraction in Frontotemporal Craniotomies

BACKGROUND The anterolateral approach is one of the main routes for accessing suprachiasmatic lesions involving the anterior communicating artery (AComA) complex. Pterional (PT) craniotomy and its alternatives, including orbitozygomatic, orbitopterional, and mini-supraorbital craniotomies, have been developed as tailored frontotemporal craniotomies. One of the main differences between PT craniotomy and its alternatives is the removal of the orbital bone along with the sphenoid wing. However, which bone part is the most important to remove has not been discussed in relation to frontal lobe retraction. We have evaluated how the removal of the supraorbital bar versus the removal of the lateral orbital wall along with the sphenoid wing affects the relationship between the levels of frontal lobe retraction and area of exposure (AOE) in the suprachiasmatic region. METHODS We performed three types of craniotomies: PT craniotomy, PT craniotomy with the removal of the supraorbital bar (PT-SO craniotomy), and PT craniotomy with the removal of the lateral orbital wall along with the sphenoid wing, i.e., the frontal process of the zygomatic bone and the orbital and cerebral faces of the greater sphenoid wing (PT-LO-SW craniotomy). For each craniotomy, the AOE around the suprachiasmatic region was measured at four different levels of frontal lobe retraction, namely, 5, 10, 15, and 20 mm, from the cranial base. RESULTS At 5-mm retraction, PT-LO-SW craniotomy was the only craniotomy in which the AComA complex was visible. At 10-mm retraction, PT-LO-SW craniotomy afforded the greatest AOE among the three craniotomies, and the AOE was significantly greater than that of PT craniotomy (P = 0.025). At 15- and 20-mm retraction, there were no significant differences among the three craniotomies. CONCLUSIONS Treatment of lesions in the suprachiasmatic region via an anterolateral route involving a frontotemporal craniotomy requires sufficient removal of the lateral orbital wall along with the greater sphenoid wing so that brain retraction is minimized.

Biological basis and clinical study of glycogen synthase kinase- 3β-targeted therapy by drug repositioning for glioblastoma

Background Glycogen synthase kinase (GSK)-3β has emerged as an appealing therapeutic target for glioblastoma (GBM). Here, we investigated the therapeutic effect of the current approved drugs against GBM via inhibition of GSK3β activity both, in experimental setting and in a clinical study for recurrent GBM patients by repositioning existent drugs in combination with temozolomide (TMZ). Materials and Methods Progression-free and overall survival rates were compared between patients with low or high expression of active GSK3β in the primary tumor. GBM cells and a mouse model were examined for the effects of GSK3β-inhibitory drugs, cimetidine, lithium, olanzapine, and valproate. The safety and efficacy of the cocktail of these drugs (CLOVA cocktail) in combination with TMZ were tested in the mouse model and in a clinical study for recurrent GBM patients. Results Activation of GSK3β in the tumor inversely correlated with patient survival as an independent prognostic factor. CLOVA cocktail significantly inhibited cell invasion and proliferation. The patients treated with CLOVA cocktail in combination with TMZ showed increased survival compared to the control group treated with TMZ alone. Conclusions Repositioning of the GSK3β-inhibitory drugs improved the prognosis of refractory GBM patients with active GSK3β in tumors. Combination of CLOVA cocktail and TMZ is a promising approach for recurrent GBM.

Direct evidence for the causal role of the left supplementary motor area in working memory: A preliminary study

Working memory is defined as active short-term memory nvolved in purpose-oriented tasks [1]. It plays an essential role n activities of daily living and social life, such as conversation, eading, and calculation. Previous functional magnetic resonance maging (MRI) studies have reported activation in some brain egionsduringa language-relatedN-back task that evaluatedworkng memory; these regions include the dorsolateral prefrontal ortex, anterior cingulate cortex, Broca’s area, supramarginal gyrus, uperior parietal lobule, and supplementary motor area (SMA) [2]. lthough several studies involving human brain mapping have ndicated that short-term memory could be subserved by several rain regions, including the perisylvian cortex, superior frontal yrus, and fornix, there is no direct evidence that the SMA plays a ole in working memory in the human brain [3–6]. Here, we report hat the left SMA plays a role in verbal working memory and the sefulness of the intraoperative 2-back task for evaluatingworking emory during awake surgery.

Intraoperative Motor Symptoms during Brain Tumor Resection in the Supplementary Motor Area (SMA) without Positive Mapping during Awake Surgery

Awake surgery could be a useful modality for lesions locating in close proximity to the eloquent areas including primary motor cortex and pyramidal tract. In case with supplementary motor area (SMA) lesion, we often encounter with intraoperative motor symptoms during awake surgery even in area without positive mapping. Although the usual recovery of the SMA syndrome has been well documented, rare cases with permanent deficits could be encountered in the clinical setting. It has been difficult to evaluate during surgery whether the intraoperative motor symptoms lead to postoperative permanent deficits. The purpose of this study was to demonstrate the intraoperative motor symptoms could be reversible, further to provide useful information for making decision to continue surgical procedure of tumor resection. Eight consecutive patients (from July 2012 to June 2014, six men and two women, aged 33–63 years) with neoplastic lesions around the SMA underwent an awake surgery. Using a retrospective analysis of intraoperative video records, intraoperative motor symptoms during tumor resection were investigated. In continuous functional monitoring during resection of SMA tumor under awake conditions, the following motor symptoms were observed during resection of the region without positive mapping: delayed motor weakness, delay of movement initiation, slowness of movement, difficulty in dual task response, and coordination disturbance. In seven patients hemiparesis observed immediately after surgery recovered to preoperative level within 6 weeks. During awake surgery for SMA tumors, the above-mentioned motor symptoms could occur in area without positive mapping and might be predictors for reversible SMA syndrome.