Junkoh Yamamoto

Bystander effect-mediated gene therapy of gliomas using genetically engineered neural stem cells

Since neural stem cells (NSCs) have the ability to migrate toward a tumor mass, genetically engineered NSCs were used for the treatment of gliomas. We first evaluated the “bystander effect” between NSCs transduced with the herpes simplex virus-thymidine kinase (HSVtk) gene (NSCtk) and C6 rat glioma cells under both in vitro and in vivo conditions. A potent bystander effect was observed in co-culture experiments of NSCtk and C6 cells. In the intracranial co-implantation experiments in athymic nude mice and Sprague–Dawley rats, the animals co-implanted with NSCtk and C6 cells and treated with ganciclovir (GCV) showed no intracranial tumors and survived more than 100 days, while those treated with physiological saline (PS) died of tumor progression. We next injected NSCtk cells into the pre-existing C6 tumor in rats and treated them with GCV or PS. The tumor volume was serially measured by magnetic resonance imaging. The tumor disappeared in six out of nine rats in the NSCtk/GCV group, while all the rats treated with PS died of tumor progression by day 21. The results indicate the feasibility of a novel gene therapy strategy for gliomas through a bystander effect generated by intratumoral injection of NSCtk cells and systemic GCV administration.

Monitoring of singlet oxygen is useful for predicting the photodynamic effects in the treatment for experimental glioma.

Purpose: Singlet oxygen (1O2) generated in photodynamic therapy (PDT) plays a very important role in killing tumor cells. Using a new near-IR photomultiplier tube system, we monitored the real-time production of 1O2 during PDT and thus investigated the relationship between the 1O2 production and photodynamic effects. Experimental Design: We did PDT in 9L gliosarcoma cells in vitro and in an experimental tumor model in vivo using 5-aminolevulinic acid and nanosecond-pulsed dye laser. During this time, we monitored 1O2 using this system. Moreover, based on the 1O2 monitoring, we set the different conditions of laser exposure and investigated whether they could affect the tumor cell death. Results: We could observe the temporal changes of 1O2 production during PDT in detail. At a low fluence rate the 1O2 signal gradually decreased with a low peak, whereas at a high fluence rate it decreased immediately with a high peak. Consequently, the cumulative 1O2 at a low fluence rate was higher, which thus induced a strong photodynamic effect. The proportion of apoptosis to necrosis might therefore be dependent on the peak and duration of the 1O2 signal. A low fluence rate tended to induce apoptotic change, whereas a high fluence rate tended to induce necrotic change. Conclusions: The results of this study suggested that the monitoring of 1O2 enables us to predict the photodynamic effect, allowing us to select the optimal laser conditions for each patient.

Potent Bystander Effect in Suicide Gene Therapy Using Neural Stem Cells Transduced with Herpes Simplex Virus Thymidine Kinase Gene

Objective: The herpes simplex virus thymidine kinase (HSVtk)/ganciclovir suicide gene therapy system has been considered as one of the most promising therapeutic strategies for malignant gliomas. We have been using HSVtk gene-transduced neural stem cells (NSCtk) that possess an ability to migrate toward a tumor mass for the treatment of experimental brain tumors. In the present study, we evaluated the potency of anti-tumor effect mediated by the bystander effect between NSCtk and C6 glioma cells in the HSVtk/ganciclovir suicide gene therapy system. Methods: NSCtk and C6 glioma cells were mixed at various ratios (NSCtk:C6 cell ratios of 1:1 to 1:64) and the bystander effect was evaluated both under in vitro and in vivo conditions. Results: In vitro co-culture experiment showed a complete tumor growth inhibition at the NSCtk:C6 ratios as low as 1:16. In vivo co-implantation study in the rat brain showed no visible tumors at the NSCtk:C6 ratios as low as 1:16 and all those rats survived more than 100 days. Conclusion: The results clearly demonstrated an extremely potent bystander effect between NSCtk and C6 cells, and the minimum number of NSCtk cells needed for the treatment of tumors was roughly estimated.

Tumor Consistency of Pituitary Macroadenomas: Predictive Analysis on the Basis of Imaging Features with Contrast-Enhanced 3D FIESTA at 3T

BACKGROUND AND PURPOSE: Preoperative evaluation of pituitary macroadenoma tumor consistency is important for neurosurgery. Thus, we aimed to retrospectively assess the role of contrast-enhanced FIESTA in predicting the tumor consistency of pituitary macroadenomas. MATERIALS AND METHODS: Twenty-nine patients with pituitary macroadenomas underwent conventional MR imaging sequences and contrast-enhanced FIESTA before surgery. Two neuroradiologists assessed the contrast-enhanced FIESTA, contrast-enhanced T1WI, and T2WI. On the basis of surgical findings, the macroadenomas were classified by the neurosurgeons as either soft or hard. Finally, Fisher exact probability tests and unpaired t tests were used to compare predictions on the basis of the MR imaging findings with the tumor consistency, collagen content, and postoperative tumor size. RESULTS: The 29 pituitary macroadenomas were classified as either solid or mosaic types. Solid type was characterized by a homogeneous pattern of tumor signal intensity without intratumoral hyperintense dots, whereas the mosaic type was characterized by many intratumoral hyperintense dots on each MR image. Statistical analyses revealed a significant correlation between tumor consistency and contrast-enhanced FIESTA findings. Sensitivity and specificity were higher for contrast-enhanced FIESTA (1.00 and 0.88–0.92, respectively) than for contrast-enhanced T1WI (0.80 and 0.25–0.33, respectively) and T2WI (0.60 and 0.38–0.54, respectively). Compared with mosaic-type adenomas, solid-type adenomas tended to have a hard tumor consistency as well as a significantly higher collagen content and lower postoperative tumor size. CONCLUSIONS: Contrast-enhanced FIESTA may provide preoperative information regarding the consistency of macroadenomas that appears to be related to the tumor collagen content.

Radiosensitizing effect of 5-aminolevulinic acid-induced protoporphyrin IX in glioma cells in vitro

5-Aminolevulinic acid (ALA) is a prodrug used in photodynamic therapy and fluorescence-guided resection of malignant gliomas due to its high cellular uptake in tumours. Porphyrin compounds act not only as photosensitizers but also as radiosensitizers. In the present study, the possible use of 5-ALA as a radiosensitizer for malignant gliomas was examined in vitro. Rat glioma cell lines (9L, C6) were pre-treated with 5-ALA and exposed to ionizing irradiation. The radiosensitizing effect of 5-ALA was evaluated by colony-forming assay. Intracellular reactive oxygen species (ROS) produced by 5-ALA and irradiation were evaluated by confocal laser scanning microscopy. Pre-treatment with 5-ALA enhanced the radiosensitivity of 9L cells to single-dose ionizing irradiation compared with controls (D0 value, 4.35 ± 0.20 and 4.84 ± 0.23 Gy, respectively, P ≤ 0.05). Exposure to multi-dose ionizing irradiation revealed high radiosensitivity in both 9L and C6 cells pre-treated with 5-ALA compared to controls. Production of intracellular ROS increased in 9L cells pre-treated with 5-ALA after ionizing irradiation compared to control cells. Thus, 5-ALA functions as a specific radiosensitizer for malignant gliomas. Intracellular 5-ALA-induced PpIX plays an important role in the production of ROS and the radiosensitizing effect under ionizing irradiation conditions.

Delineation of optic nerves and chiasm in close proximity to large suprasellar tumors with contrast-enhanced FIESTA MR imaging.

PURPOSE To evaluate whether contrast material-enhanced (CE) fast imaging employing steady-state acquisition (FIESTA) can depict the anterior optic pathways in patients with large suprasellar tumors. MATERIALS AND METHODS Institutional review board approval was obtained. Twenty-eight patients with large suprasellar tumors undergoing surgical treatment (19 pituitary adenomas, six meningiomas, and three additional miscellaneous tumors) underwent preoperative magnetic resonance (MR) imaging, including CE FIESTA, at 3.0 T. Two radiologists assessed the visibility of five segments of the optic pathways (bilateral optic nerves and optic tracts, optic chiasm) with CE FIESTA and conventional MR imaging, including thin-section coronal T2-weighted imaging and CE T1-weighted imaging, by using a three-point scale. Moreover, the preoperative signal intensity of the optic pathways was correlated with pre- and postoperative visual impairment to determine whether high signal intensity at CE FIESTA is predictive of persistence of visual impairment after surgery. The χ(2) test was used to compare scores assigned to CE FIESTA and conventional MR images. RESULTS The percentage of anterior optic pathways rated as visible was significantly higher with CE FIESTA than with conventional MR imaging (100% [140 of 140 segments] vs 78% [109 of 140 segments], P < .05). Thirty-one of the 140 segments (22%) were not depicted with conventional MR imaging; all of these 31 segments were visualized with CE FIESTA. For 12 patients who underwent transcranial surgery, the anatomic locations of the optic pathways at CE FIESTA were compatible with the surgical findings. CE FIESTA helped predict persistent visual impairment after surgical treatment with a sensitivity of 75% (three of four patients) and a specificity of 96% (23 of 24 patients). The accuracy of CT FIESTA in the prediction of visual loss was significantly higher than that of T2-weighted imaging (93% [26 of 28 patients] vs 50% [14 of 28 patients], P < .05). CONCLUSION CE FIESTA is useful for the preoperative localization of the anterior optic pathways in patients with large suprasellar tumors and offers the potential to predict persistent visual impairment after decompression.

Prediction of hard meningiomas: quantitative evaluation based on the magnetic resonance signal intensity.

Background From a surgical perspective, presurgical prediction of meningioma consistency is beneficial. Purpose To quantitatively analyze the correlation between the magnetic resonance (MR) signal intensity (SI) or apparent diffusion coefficient (ADC) and meningioma consistency and to determine which MR sequence could help predicting hard meningiomas. Material and Methods This study included 43 patients with meningiomas who underwent preoperative MR imaging (MRI), including T1-weighted (T1W) imaging, T2-weighted (T2W) imaging, fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), contrast-enhanced (CE)-T1W imaging, and CE-fast imaging employing steady-state acquisition (FIESTA). A neurosurgeon evaluated the tumor consistency using a visual analog scale (VAS) with the anchors “soft” (score = 0) and “hard” (score = 10). The SI ratio (tumor to cerebral cortex SI) and ADC value were compared with the tumor consistency. The sensitivity, specificity, and accuracy for predicting hard meningiomas (VAS score ≥8; 9 of 43 patients) were calculated using cutoff values for the SI ratio that were obtained in a receiver operating characteristic curve analysis. Results A significant negative correlation was observed between the tumor consistency and the SI ratio on T2W imaging, FLAIR, and CE-FIESTA (P < 0.05) but not on T1W imaging, CE-T1W imaging, and the ADC value. The sensitivity, specificity, and accuracy for predicting hard meningiomas were 89%, 79%, and 81% with T2W imaging; 89%, 76%, and 79% with FLAIR; and 100%, 74%, and 79% with CE-FIESTA, respectively. Conclusion Our results suggest that a quantitative assessment using conventional T2W imaging or FLAIR may be a simple and useful method for predicting hard meningiomas.

Severe Subarachnoid Hemorrhage Associated with Cerebral Venous Thrombosis in Early Pregnancy: A Case Report

BACKGROUND Cerebral venous thrombosis (CVT) rarely induces subarachnoid hemorrhage (SAH). During late pregnancy and puerperium, CVT is an uncommon but important cause of stroke. However, severe SAH resulting from CVT is extremely rare during early pregnancy. OBJECTIVE We report on a rare case of severe SAH due to CVT, and discuss the potential pitfalls of CVT diagnosis in early pregnancy. CASE REPORT A 32-year-old pregnant woman (9th week of pregnancy) presented with slight head dullness. Initial magnetic resonance imaging (MRI) revealed focal, abnormal signal intensity in the left thalamus. Nine days later, the patient developed a generalized seizure and severe SAH was detected with computed tomography (CT) scan. MRI and cerebral angiography revealed a completely thrombosed superior sagittal sinus, vein of Galen, straight sinus, and right transverse sinus. Transvaginal sonography indicated a missed abortion. The day after admission, the patient presented again with a progressive loss of consciousness and signs of herniation. The patient underwent emergency decompressive craniotomy, followed by intrauterine curettage. Two months later, she made an excellent recovery except for a slight visual field defect. CONCLUSIONS A rare case of severe SAH due to CVT is reported, with emphasis on the potential pitfalls of CVT diagnosis in early pregnancy.

Intratumoral hemorrhage because of primary spinal mixed germ cell tumor presenting with atypical radiological features in an adult

BACKGROUND CONTEXT Germ cell tumors are known to arise in the central nervous system, usually in the intracranial regions. However, primary spinal mixed germ cell tumors are extremely rare. PURPOSE This is the first reported case of intratumoral hemorrhage because of a primary spinal mixed germ cell tumor consisting of germinoma and immature teratoma in the conus medullaris of an adult patient that presented with rapid changes on magnetic resonance image (MRI). We report this rare case and discuss the clinical manifestations of an intramedullary spinal mixed germ cell tumor in adult. STUDY DESIGN A case report. METHODS A 42-year-old woman experienced buttock numbness, and a spinal cord tumor was observed on the conus medullaris on MRI. The patient was scheduled for an operation in 1 month, but she developed sudden-onset neurologic deterioration. Rapid progression of the tumor was observed on follow-up MRI. The tumor was removed by emergency surgery and was identified as a primary mixed germinoma and immature teratoma. RESULTS The patient received adjuvant chemotherapy and radiotherapy after gross total resection. The neurologic deficit of the patient was relieved, and recurrence of the tumor was not observed 26 months after the surgery. CONCLUSIONS We present this rare case and emphasize the necessity of precise diagnosis and early treatment of primary spinal germ cell tumor. Close observation on MRI is required after surgery, and adjuvant chemotherapy and radiotherapy should be considered according to the pathologic features.

Superficial siderosis associated with a chronic subdural hematoma: T2-weighted MR imaging at 3T.

RATIONALE AND OBJECTIVES The purposes of this study were to assess the association between superficial siderosis (SS) and subdural hematoma (SDH) and to evaluate the magnetic resonance imaging (MR) characteristics of SS in patients with the presence or histories of SDH compared to those with histories of aneurysmal subarachnoid hemorrhage (SAH). MATERIALS AND METHODS A radiology database for a 4-year period contained data on patients with diagnoses of SDH. From these patients, 47 patients were further selected who underwent brain MR examinations using a 3-T MR system (the SDH group). Using T2-weighted images, two neuroradiologists evaluated the presence or absence and the characteristics of SS findings by comparing the patients with histories of aneurysmal subarachnoid hemorrhage (the SAH group; n = 36). The SS findings were classified into three types: apical (SS at the top of the surface of the gyrus of the cerebral hemisphere), gyral (SS surrounding the gyrus), and mixed. RESULTS SS findings were seen in 13 patients (27.7%) in the SDH group (SS-SDH) and 13 patients (36.1%) in the SAH group (SS-SAH); all 13 cases of SS-SDH were the apical type, whereas the 13 cases of SS-SAH were either the gyral (n = 9 [69.2%]) or mixed (n = 4 [30.8%]) type. SS-SDH was seen only in the cerebral hemisphere ipsilateral to the side of the SDH (12 of 13 [92.3%]). All 13 cases of SS-SDH were accompanied by thinning of gray-matter intensity in the cerebral cortex, which was more frequently seen than in SS-SAH (P < .01). CONCLUSION SDH occasionally causes the SS-like MR findings, and the pathogenesis of SS-SDH may be also different from that of SS-SAH.