Ryuta Saito

Distribution of Liposomes into Brain and Rat Brain Tumor Models by Convection-Enhanced Delivery Monitored with Magnetic Resonance Imaging

Although liposomes have been used as a vehicle for delivery of therapeutic agents in oncology, their efficacy in targeting brain tumors has been limited due to poor penetration through the blood-brain barrier. Because convection-enhanced delivery (CED) of liposomes may improve the therapeutic index for targeting brain tumors, we conducted a three-stage study: stage 1 established the feasibility of using in vivo magnetic resonance imaging (MRI) to confirm adequate liposomal distribution within targeted regions in normal rat brain. Liposomes colabeled with gadolinium (Gd) and a fluorescent indicator, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine-5,5′-disulfonic acid [DiI-DS; formally DiIC18(3)-DS], were administered by CED into striatal regions. The minimum concentration of Gd needed for monitoring, correlation of infused volume with distribution volume, clearance of infused liposome containing Gd and DiI-DS (Lip/Gd/DiI-DS), and potential local toxicity were evaluated. After determination of adequate conditions for MRI detection in normal brain, stage 2 evaluated the feasibility of in vivo MRI monitoring of liposomal distribution in C6 and 9L-2 rat glioma models. In both models, the distribution of Lip/Gd/DiI-DS covering the tumor mass was well defined and monitored with MRI. Stage 3 was designed to develop a clinically relevant treatment strategy in the 9L-2 model by infusing liposome containing Gd (Lip/Gd), prepared in the same size as Lip/Gd/DiI-DS, with Doxil, a liposomal drug of similar size used to treat several cancers. MRI detection of Lip/Gd coadministered with Doxil provided optimum CED parameters for complete coverage of 9L-2 tumors. By permitting in vivo monitoring of therapeutic distribution in brain tumors, this technique optimizes local drug delivery and may provide a basis for clinical applications in the treatment of malignant glioma.

Extensive distribution of liposomes in rodent brains and brain tumors following convection-enhanced delivery

Liposomes labeled with various markers were subjected to local–regional administration with either direct injection or convection-enhanced delivery (CED) into rodent brains and brain tumor models. Direct injection of liposomes containing attached or encapsulated fluorochromes and/or encapsulated gold particles indicated that tissue localization of liposomes could be sensitively and specifically detected in the central nervous system (CNS). When CED was applied, liposomes achieved extensive and efficient distribution within normal mouse brains. Co-infusion of mannitol further increased tissue penetration of liposomes. Liposomes were also loaded with gadodiamide to monitor their CNS distribution in rats by magnetic resonance imaging (MRI). CED-infused liposomes were readily seen on MRI scans as large regions of intense signal at 2 h, and more diffuse regions at 24 h. Finally, labeled liposomes were infused via CED into tumor tissue in glioma xenograft models in rodent hosts. In intracranial U-87 glioma xenografts, CED-infused liposomes had distributed throughout tumor tissue, including extension into surrounding normal tissue. Greater penetration was observed using 40 versus 90 nm liposomes, as well as with mannitol co-infusion. To our knowledge, this is the first report of CED infusion of liposomes into the CNS. We conclude that CED of liposomes in the CNS is a feasible approach, and offers a promising strategy for targeting therapeutic agents to brain tumors.

Novel Nanoliposomal CPT-11 Infused by Convection-Enhanced Delivery in Intracranial Tumors: Pharmacology and Efficacy

We hypothesized that combining convection-enhanced delivery (CED) with a novel, highly stable nanoparticle/liposome containing CPT-11 (nanoliposomal CPT-11) would provide a dual drug delivery strategy for brain tumor treatment. Following CED in rat brains, tissue retention of nanoliposomal CPT-11 was greatly prolonged, with >20% injected dose remaining at 12 days for all doses. Tissue residence was dose dependent, with doses of 60 microg (3 mg/mL), 0.8 mg (40 mg/mL), and 1.6 mg (80 mg/mL) resulting in tissue half-life (t(1/2)) of 6.7, 10.7, and 19.7 days, respectively. In contrast, CED of free CPT-11 resulted in rapid drug clearance (tissue t(1/2) = 0.3 day). At equivalent CED doses, nanoliposomal CPT-11 increased area under the time-concentration curve by 25-fold and tissue t(1/2) by 22-fold over free CPT-11; CED in intracranial U87 glioma xenografts showed even longer tumor retention (tissue t(1/2) = 43 days). Plasma levels were undetectable following CED of nanoliposomal CPT-11. Importantly, prolonged exposure to nanoliposomal CPT-11 resulted in no measurable central nervous system (CNS) toxicity at any dose tested (0.06-1.6 mg/rat), whereas CED of free CPT-11 induced severe CNS toxicity at 0.4 mg/rat. In the intracranial U87 glioma xenograft model, a single CED infusion of nanoliposomal CPT-11 at 1.6 mg resulted in significantly improved median survival (>100 days) compared with CED of control liposomes (19.5 days; P = 4.9 x 10(-5)) or free drug (28.5 days; P = 0.011). We conclude that CED of nanoliposomal CPT-11 greatly prolonged tissue residence while also substantially reducing toxicity, resulting in a highly effective treatment strategy in preclinical brain tumor models.

Analysis of IDH1 and IDH2 mutations in Japanese glioma patients

A recent study reported on mutations in the active site of the isocitrate dehydrogenase 1 (IDH1) gene in several types of gliomas. All mutations detected resulted in an amino acid exchange at position 132. We analyzed the genomic region spanning wild‐type R132 of IDH1 by direct sequencing in 125 glial tumors. A total of 39 IDH1 mutations were observed. Mutations of the IDH2 gene, homologous to IDH1, were often detected in gliomas without IDH1 mutations. In the present study, R172 mutation of the IDH2 gene was detected in one anaplastic astrocytoma. IDH1 or IDH2 mutations were frequently in oligodendrogliomas (67%), anaplastic astrocytomas (62%), anaplastic oligoastrocytomas (75%), anaplastic oligodendrogliomas (50%), secondary glioblastomas (67%), gangliogliomas (38%), and anaplastic gangliogliomas (60%). Primary glioblastomas were characterized by a low frequency of mutations (5%) at amino acid position 132 of IDH1. Mutations of the IDH1 or IDH2 genes were significantly associated with improved outcome in patients with anaplastic astrocytomas. Our data suggest that IDH1 or IDH2 mutation plays a role in early tumor progression of several types of glioma and might arise from a common glial precursor. The infrequency of IDH1 mutation in primary glioblastomas revealed that these subtypes are genetically distinct entities from other glial tumors. (Cancer Sci 2009; 100: 1996–1998)

Convection-Enhanced Delivery of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand with Systemic Administration of Temozolomide Prolongs Survival in an Intracranial Glioblastoma Xenograft Model

Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent activator of cell death, preferentially killing neoplastic cells over normal cells, the efficacy of TRAIL for the treatment of glioma might be limited due to cellular resistance and, importantly, poor distribution after systemic administration. TRAIL and temozolomide (TMZ) were recently shown to have a synergistic antitumor effect against U87MG glioma cells in vitro. Convection-enhanced delivery (CED) can effectively distribute TRAIL protein throughout a brain tumor mass. In this study, we evaluated CED of TRAIL, alone and in conjunction with systemic TMZ administration, for antitumor efficacy. CED of TRAIL demonstrated safe and effective distribution in both normal brain and a U87MG intracranial xenograft model. Individually, both CED of TRAIL and systemic TMZ administration prolonged survival in tumor-bearing rats. However, the combination of these two treatments was significantly more effective than either treatment alone. CED of TRAIL in conjunction with systemic TMZ treatment is a promising strategy for the treatment of malignant gliomas.

Human Gene Therapy for Malignant Gliomas (Glioblastoma Multiforme and Anaplastic Astrocytoma) by In Vivo Transduction with Human Interferon β Gene Using Cationic Liposomes

Transfer of interferon beta gene via cationic liposomes has been found to induce regression of experimental glioma. We performed a pilot clinical trial of safety and effectiveness of this interferon beta gene therapy in five patients with malignant glioma (glioblastoma multiforme or anaplastic astrocytoma). Transgene expression and antitumor activity were detected in four patients. Two patients showed a partial response (>50% tumor reduction) and two others had stable disease 10 weeks after beginning therapy. One patient could not be evaluated because of previous treatment with gamma-knife therapy. This study suggests the feasibility and safety of interferon beta gene therapy, which may become an important treatment option for patients with malignant glioma.

Symptomatic spinal dissemination of malignant astrocytoma

AbstractObject: Symptomatic spinal dissemination of malignant astrocytoma is rarely found except at autopsy. This study evaluated the clinical incidence and characteristics of spinal dissemination and the effect on outcome. Patients and methods: Patients treated for primary malignant astrocytoma, including 33 with anaplastic astrocytoma and 35 with glioblastoma, at our department between 1997 and 1999 were followed up until April 30, 2001. Head magnetic resonance (MR) imaging of all patients was obtained every 2–3 months. Signs and symptoms of leptomeningeal spread were checked at monthly outpatient examinations. Spinal MR imaging was performed if any symptoms indicating spinal dissemination were found. Results: Median survival times of patients with anaplastic astrocytoma and glioblastoma were 40.5 and 16.0 months, respectively. Seventeen patients (25%) developed intracranial dissemination and 15 of these died. Six patients (8.8%), one with anaplastic astrocytoma and five with glioblastoma, developed spinal dissemination. All patients with spinal dissemination also had intracranial dissemination. Five of the six patients died, despite systemic radiochemotherapy in four patients. All patients died of extensive whole brain and spinal dissemination or nodular mass enlargement at the upper cervical cord, not of local massive tumor progression. Conclusions: Symptomatic spinal dissemination of malignant astrocytoma is not so rare, and is the cause of death. The relatively high incidence of symptomatic leptomeningeal dissemination must be considered in the treatment of malignant astrocytomas.

Convection-enhanced delivery of polyethylene glycol–coated liposomal doxorubicin: characterization and efficacy in rat intracranial glioma models

OBJECT The characteristics of polyethylene glycol-coated liposomal doxorubicin (PLD), the only liposomal drug now clinically available for intravenous injection, were investigated after convection-enhanced delivery (CED) into the rat brain parenchyma. METHODS The distribution, tissue retention, and toxicity profile were evaluated after CED into the rat brain parenchyma. The antitumor efficacy was also determined in rodent intracranial U-251MG and U-87MG glioma models. RESULTS Convection-enhanced delivery of PLD achieved wider distributions and delayed onset of toxicity in the brain parenchyma compared with CED of free doxorubicin infusion. Fluorescence generated from doxorubicin infused as PLD was detected until at least 30 days after infusion. Local toxicity was not observed when a 10% dilution of the commercially available PLD solution was used (0.2 mg/ml doxorubicin), but was significant at higher concentrations. Results after 10% PLD was delivered locally with CED demonstrated significant survival prolongation in both intracranial U-251MG and U-87MG xenograft models. CONCLUSIONS Convection-enhanced delivery of PLD achieved extensive tissue distribution and sustained drug release. Convection-enhanced delivery of PLD is a promising chemotherapy for the treatment of malignant gliomas.

Regression of recurrent glioblastoma infiltrating the brainstem after convection-enhanced delivery of nimustine hydrochloride

This 13-year-old boy with a history of cranial irradiation for the CNS recurrence of acute lymphocytic leukemia developed a glioblastoma in the right cerebellum. Resection and chemo- and radiotherapy induced remission of the disease. However, recurrence was noted in the brainstem region 8 months later. Because no effective treatment was available for this recurrent lesion, the authors decided to use convection-enhanced delivery (CED) to infuse nimustine hydrochloride. On stereotactic insertion of the infusion cannula into the brainstem lesion, CED of nimustine hydrochloride was performed with real-time MR imaging to monitor the co-infused chelated gadolinium. The patients preinfusion symptom of diplopia disappeared after treatment. Follow-up MR imaging revealed the response of the tumor. The authors report on a case of recurrent glioblastoma infiltrating the brainstem that regressed after CED of nimustine hydrochloride.

Germ cell tumors in the basal ganglia: problems of early diagnosis and treatment

OBJECT Intracranial germ cell tumors (GCTs) originating in the basal ganglia are rare. The authors investigated factors related to the diagnosis of these lesions as well as outcome in order to help decrease the time to diagnosis and improve treatment efficacy. METHODS The authors reviewed the clinical features of 142 cases of intracranial GCT in their institute. Fourteen cases of basal ganglia GCT were identified. The symptoms, neuroimaging findings, delay between symptom onset and diagnosis or treatment, initial and further treatment, and outcome were investigated. RESULTS Major symptoms were motor weakness and precocious puberty. Gadolinium-enhanced T1-weighted MR images showed enhancement in 8 of 11 patients examined, but only slight hyperintensity without enhancement in 2 patients. Ipsilateral peduncle and hemispheric atrophy were found in 3 and 4 patients, respectively. Cases of basal ganglia GCT were characterized by a longer delay from the initial neuroimaging examination to diagnosis compared with GCT in other regions. Five patients had aggravated hemiparesis in the extremities due to the delay in diagnosis. Despite good response to the initial therapy, 5 patients experienced recurrence; 2 of these 5 had malignant GCTs, and 3 had been treated only with chemotherapy or radiochemotherapy with insufficient radiation dose and field. Finally, the 2 patients with malignant GCTs died of the disease, and 1 died of aspiration pneumonia due to dissemination around the brainstem. CONCLUSIONS Early diagnosis requires MR imaging with administration of contrast medium in young patients presenting with motor weakness and/or precocious puberty. Serial neuroimaging studies should be performed if any tiny lesion is detected in the basal ganglia. Since insufficient treatment resulted in early recurrence, radiation therapy with adequate dose and field is essential.