M alignant glioma is the most common brain tumor in adults; it has an aggressive lethal nature and a median survival of only 14 months, despite the standard established therapy of maximum resection followed by radiation and chemotherapy. Several immunotherapies, such as dendritic cell therapy, have been evaluated as new adjuvant approaches. However, the efficacy of immunotherapy for patients with malignant glioma is limited for several reasons, including the anatomical isolation of the central nervous system by the blood-brain barrier, the absence of a lymphatic drainage system, and the ability of glioma cells to escape recognition by the immune system. Recent studies suggest that indoleamine 2,3-dioxygenase (IDO), the initial rate-limiting enzyme in tryptophan (Trp) metabolism, may be involved in such tumor-induced escape from immunosurveillance, showing an immunosuppressive function.14,27 IDO is expressed in various human cancers such as malignant melanoma, ovarabbreviatioNs FACS = fluorescence-activated cell sorter; GAPDH = glyceraldehyde-3-phosphate dehydrogenase; IDO = indoleamine 2,3-dioxygenase; IDO-KD = IDO-knockdown; INF-g = interferon-g; PBS = phosphate-buffered saline; RT-PCR = real-time polymerase chain reaction; SEM = standard error of the mean; shRNA = short hairpin RNA; TMZ = temozolomide; Treg = regulatory T cell; Trp = tryptophan; 1-MT = 1-methyl-l-tryptophan. Thus, IDO may be a therapeutic target for malignant cancer. The authors have recently shown that IDO expression is markedly increased in human glioblastoma and secondary glioblastoma with malignant change, suggesting that IDO targeting may also have therapeutic potential for patients with glioma. The aim of this study was to investigate the antitumor effect of IDO inhibition and to examine the synergistic function of IDO inhibitor and temozolomide (TMZ) in a murine glioma model. methods Murine glioma GL261 cells and human glioma U87 cells were included in this study. The authors used 3 mouse models to study glioma cell growth: 1) a subcutaneous ectopic model, 2) a syngeneic intracranial orthotopic model, and 3) an allogenic intracranial orthotopic model. IDO inhibition was achieved via knockdown of IDO in GL261 cells using short hairpin RNA (shRNA) and through oral administration of the IDO inhibitor, 1-methyl-l-tryptophan (1-MT). Tumor volume in the subcutaneous model and survival time in the intracranial model were evaluated. results In the subcutaneous model, oral administration of 1-MT significantly suppressed tumor growth, and synergistic antitumor effects of 1-MT and TMZ were observed (p < 0.01). Mice containing intracranially inoculated IDO knockdown cells had a significantly longer survival period as compared with control mice (p < 0.01). coNclusioNs These results suggest that IDO expression is implicated in immunosuppression and tumor progression in glioma cells. Therefore, combining IDO inhibition with standard TMZ treatment could be an encouraging therapeutic strategy for patients with malignant glioma.
We describe a rare case where a patient developed intracranial pial arteriovenous (AV) fistula due to dural tenting. The patient was a 63-year-old woman who had undergone neck clipping for an unruptured middle cerebral artery (MCA) aneurysm. The surgery was performed without any problems and her postoperative course was uneventful. Two weeks after cerebral angiography operation revealed a pial AV fistula fed by the right MCA and drained into the vein of Trolard through the Sylvian vein which had not existed before surgery. Being diagnosed as de novo pial AV fistula, surgical repair was performed. The AV fistula was located just beneath the dural tenting. The fistulous point was confirmed with fluorescein video angiography and obliterated using a clip. Although rare, we should pay attention to the AV fistula due to dural tenting as the complications of cranial surgery.
Neck clipping of a large middle cerebral artery aneurysm was performed using a newly developed surgical microscope integrated with modules for both indocyanine green (ICG) and fluorescein videoangiography. During surgery, ICG and fluorescein videoangiography by intra-arterial or intravenous injection were safely carried out without interrupting the surgical procedure. Based on the findings obtained from the case, we evaluated the differences between the dyes and the injection routes. With intra-arterial injection, fluorescein offered sharper contrast images and was better at depicting fine arteries than ICG. Patchy staining of vessel walls was observed in intravenous fluorescein videoangiography, while it was not evident in ICG. Intra-arterial injection method had a great advantage in the rapid clearance of the dyes, which allowed us to perform repeated videoangiography within a short period, and was useful in detecting incomplete clipping in this case; however, catheter insertion requires additional work and carries a potential risk. Use of a microscope integrated for both ICG and fluorescein videoangiography would be another method for repeated evaluation. Namely, alternate use of the dyes enables us to perform videoangiography in a short time even via intravenous injection.
Biomaterials to treat cancers hold therapeutic potential; however, their translation to bedside treatment requires further study. The carmustine (1,3-bis (2-chloroethyl)-1-nitrosourea; BCNU) wafer, a biodegradable polymer, currently is the only drug that is able to be placed at the surgical site to treat malignant tumors. However, how this wafer affects the surrounding tumor microenvironment is not well understood to date. We retrospectively reviewed all patients with glioblastoma treated with and without BCNU wafers who underwent repeat resection at tumor recurrence. We investigated radiological imaging; the interval between the two surgeries; and immunohistochemistry of CD3, CD4, CD8, CD20, CD68, FOXP3, and PD1. We implanted BCNU wafers in 41 newly diagnosed glioblastoma patients after approval of the wafer in Japan. Of them, 14 underwent surgery at recurrence and tissue was obtained from around the wafers. The interval between the first and second surgeries ranged from 63 to 421 days. The wafer could be observed on magnetic resonance imaging at up to 226 days, whereas intraoperatively the biodegraded material of the wafer could be found at up to 421 days after the initial surgery. Immunohistochemical analysis demonstrated that CD8+ and CD68+ cells were significantly increased, but FOXP3+ cells did not increase, after wafer implantation compared to tissue from cases without wafer implantation. MRI data and immune cells, as well as interval between surgeries and immune cells, demonstrated positive correlation. These results helped us to understand the bioactivity of bioengineered materials and to establish a new approach for immunotherapy.
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