Pharmacological modulation of blood-brain barrier increases permeability of doxorubicin into the rat brain

Our group recently demonstrated in a rat model that pretreatment with morphine facilitates doxorubicin delivery to the brain in the absence of signs of increased acute systemic toxicity. Morphine and other drugs such as dexamethasone or ondansetron seem to inhibit MDR proteins localized on blood-brain barrier, neurons and glial cells increasing the access of doxorubicin to the brain by efflux transporters competition. We explored the feasibility of active modification of the blood-brain barrier protection, by using morphine dexamethasone or ondansetron pretreatment, to allow doxorubicin accumulation into the brain in a rodent model. Rats were pretreated with morphine (10 mg/kg, i.p.), dexamethasone (2 mg/kg, i.p.) or ondansetron (2 mg/kg, i.p.) before injection of doxorubicin (12 mg/kg, i.p.). Quantitative analysis of doxorubicin was performed by mass spectrometry. Acute hearth and kidney damage was analyzed by measuring doxorubicin accumulation, LDH activity and malondialdehyde plasma levels. The concentration of doxorubicin was significantly higher in all brain areas of rats pretreated with morphine (P < 0.001) or ondansetron (P < 0.05) than in control tissues. The concentration of doxorubicin was significantly higher in cerebral hemispheres and brainstem (P < 0.05) but not in cerebellum of rats pretreated with dexamethasone than in control tissues. Pretreatment with any of these drugs did not increase LDH activity or lipid peroxidation compared to controls. Our data suggest that morphine, dexamethasone or ondansetron pretreatment is able to allow doxorubicin penetration inside the brain by modulating the BBB. This effect is not associated with acute cardiac or renal toxicity. This finding might provide the rationale for clinical applications in the treatment of refractory brain tumors and pave the way to novel applications of active but currently inapplicable chemotherapeutic drugs.     

钙激活性钾通道在缓激肽选择性开放血脑肿瘤屏障机制中的大鼠在体研究

目的:探讨钙激活性钾通道(calciumactivatedpotassiumchannel,KCa)在缓激肽(bradykininBK)选择性开放血脑肿瘤屏障(bloodbraintumorbarrier,BTB)中的作用。方法:建立大鼠脑胶质瘤模型,颈内动脉分别灌注BK、KCa通道激动剂NS1619以及灌注BK后再灌注KCa通道阻断剂IBTX,取肿瘤标本电镜观察毛细血管内皮细胞的变化;颈内动脉灌注BK后采用免疫组化ABC法和Westernblot法测定肿瘤组织KCa通道蛋白的分布和含量的变化。结果:大鼠脑胶质瘤模型经颈内动脉分别灌注BK和NS1619后,肿瘤毛细血管内皮细胞的吞饮小泡增加,依次灌注BK和IBTX后,未观察到肿瘤毛细血管内皮细胞的吞饮小泡增加;脑胶质瘤大鼠模型经颈内动脉灌注BK后,其肿瘤内血管内皮细胞的KCa通道蛋白增加,且灌注后10min增加最为显著。结论:KCa通道蛋白的表达增多可能是BK选择性开放BTB机制中的重要因素之一。     

Growth of human lung tumor in the brain of the nude rat as a model to evaluate antitumor agent delivery across the blood-brain barrier

We have developed a brain tumor model in the nude rat utilizing NCI-N417D human small cell carcinoma of the lung grown both intracerebrally and s.c. The median latency period from the time of intracerebral tumor inoculation to the onset of neurological symptoms is 13 days with an intracerebral tumor take rate of 91% (29 of 32). The median survival is 13 days, and all animals were dead by Day 26. The tumor is discrete, well circumscribed, with occasional leptomeningeal spread and with minimal evidence of surrounding cerebral edema. Intracerebrally, this tumor is usually impermeable to Evan's blue:albumin (Mr 68,500) but not fluorescein (Mr 376). Although variable, the intracerebral tumor is less permeable to methotrexate than is the same tumor grown s.c. in the same animal (P less than 0.005). The intraarterial and i.v. routes of methotrexate administration in the presence and absence of blood-brain barrier opening were evaluated. Drug delivery to the intracerebral tumor and ipsilateral brain was significantly (P less than 0.025) greater when the methotrexate was given intraarterially and was significantly (P less than 0.0025) increased after osmotic blood-brain barrier opening. After barrier opening, methotrexate concentration was enhanced 3- to 4-fold in tumor and 10- to 20-fold in brain around tumor. Thus, the nude rat provides a model to investigate the biology and therapeutic responsiveness of human small cell carcinoma of the lung grown intracerebrally where it develops a blood-tumor barrier similar to that seen in humans. This model further provides the unique opportunity to investigate the role of osmotic blood-brain barrier opening in the treatment of a tumor which is sensitive to chemotherapeutic agents and for which tumor-specific monoclonal antibodies are available.     

全脑常规分割外照射对大鼠血脑屏障药物通透性的影响

目的 探讨放射线全脑常规外照射后对血脑屏障通透性的影响,为临床颅内肿瘤放化疗的序贯性和最佳化疗时机提供理论基础.方法 100只正常成熟Sprague-Dawley大鼠被随机分为0、10、20、30、40Gy组,每组20只.采用60^Co γ线进行全脑常规分割外照射,2 Gy/次,1个野/d,5次/周.各组完成计划照射剂量后16 h经尾静脉注射氨甲蝶呤（MTX）25mg/kg,2 h后采集静脉血及脑脊液,用RP-HPLC法监测其中的MTX浓度.结果 对照组、10、20、30、40Gy组脑脊液中MTX平均浓度分别为0.07、0.08、0.12、0.24、0.23mg/L.经秩变换检验方差分析,10Gy组与对照组、30Gy与40Gy组脑脊液中MTX浓度比较差异无统计学意义（P＞0.05）,其余各组间两两比较差异均有统计学意义（P值均＜0.05）.血液中MTX平均浓度各组比较均无统计学意义（P＞0.05）结论 放射线具有降低血脑屏障功能的作用,照射20～30Gy其通透性明显增加,故20～30Gy时为化疗最佳时机.     

Evaluation of blood-brain barrier permeability and the effect of interferon in mouse glioma model

Summary The aim of this study was to evaluate whether interferon [IFN] can affect intracerebrally grown glioma and how alteration of the blood-brain barrier [BBB] may influence this effect. An intracerebrally implanted glioma G-26 (G-26) mouse brain-tumor model was developed and used in these studies. Histological characterization of this intracerebrally grown tumor revealed its anaplastic character. The astrocytic origin of G-26 was evidenced by glial fibrillary acidic protein staining and electron microscopic visualization of glial filaments. A study of tumor progression and animal survival showed development of a well defined tumor nodule within approximately seven days after the implantation. The median animal survival time was 27 ±3.8 days. The integrity of the blood-brain barrier [BBB] within the tumor was evaluated by the intravenous injection of horseradish peroxidase at days 3, 7,10 and 20 after brain tumor implant and compared to sham controls. The tumor-induced BBB alteration was progressive from day 3 to day 20.Glioma-26 subcutaneously passed in C57BL/6 mice was also continously cultured in vitro. Its proliferation was inhibited by homologous mouse interferon / [MuIFN / but not by human interferon a lymphoblastoid or human interferon ß. The in vivo studies of G-26 glioma treatment with MuIFN / were performed using single bolus of IFN in osmotically altered animals or slow IFN infusion through osmotic micro-pumps. The slow infusion of IFN had no effect on animal survival. However, a statistically significant increase in animal survival was observed after single bolus IFN treatment following osmotic BBB alteration.     

Controllable permeability of blood-brain barrier and reduced brain injury through low-intensity pulsed ultrasound stimulation

It has been shown that the blood-brain barrier (BBB) can be locally disrupted by focused ultrasound (FUS) in the presence of microbubbles (MB) while sustaining little damage to the brain tissue. Thus, the safety issue associated with FUS-induced BBB disruption (BBBD) needs to be investigated for future clinical applications. This study demonstrated the neuroprotective effects induced by low-intensity pulsed ultrasound (LIPUS) against brain injury in the sonicated brain. Rats subjected to a BBB disruption injury received LIPUS exposure for 5 min after FUS/MB application. Measurements of BBB permeability, brain water content, and histological analysis were then carried out to evaluate the effects of LIPUS. The permeability and time window of FUS-induced BBBD can be effectively modulated with LIPUS. LIPUS also significantly reduced brain edema, neuronal death, and apoptosis in the sonicated brain. Our results show that brain injury in the FUS-induced BBBD model could be ameliorated by LIPUS and that LIPUS may be proposed as a novel treatment modality for controllable release of drugs into the brain.     

Effects of fractionated radiation on the brain vasculature in a murine model: blood-brain barrier permeability, astrocyte proliferation, and ultrastructural changes

PURPOSE: Radiation therapy of CNS tumors damages the blood-brain barrier (BBB) and normal brain tissue. Our aims were to characterize the short- and long-term effects of fractionated radiotherapy (FRT) on cerebral microvasculature in mice and to investigate the mechanism of change in BBB permeability in mice. METHODS AND MATERIALS: Intravital microscopy and a cranial window technique were used to measure BBB permeability to fluorescein isothiocyanate (FITC)-dextran and leukocyte endothelial interactions before and after cranial irradiation. Daily doses of 2 Gy were delivered 5 days/week (total, 40 Gy). We immunostained the molecules to detect the expression of glial fibrillary acidic protein and to demonstrate astrocyte activity in brain parenchyma. To relate the permeability changes to endothelial ultrastructural changes, we used electron microscopy. RESULTS: Blood-brain barrier permeability did not increase significantly until 90 days after FRT, at which point it increased continuously until 180 days post-FRT. The number of adherent leukocytes did not increase during the study. The number of astrocytes in the cerebral cortex increased significantly; vesicular activity in endothelial cells increased beginning 90 days after irradiation, and most tight junctions stayed intact, although some were shorter and less dense at 120 and 180 days. CONCLUSIONS: The cellular and microvasculature response of the brain to FRT is mediated through astrogliosis and ultrastructural changes, accompanied by an increase in BBB permeability. The response to FRT is delayed as compared with single-dose irradiation treatment, and does not involve leukocyte adhesion. However, FRT induces an increase in the BBB permeability, as in the case of single-dose irradiation.     

Sagopilone crosses the blood-brain barrier in vivo to inhibit brain tumor growth and metastases

The aim of this study was to determine the efficacy of sagopilone (ZK-EPO), a novel epothilone, compared with other anticancer agents in orthotopic models of human primary and secondary brain tumors. Autoradiography and pharmacokinetic analyses were performed on rats and mice to determine passage across the blood-brain barrier and organ distribution of sagopilone. Mice bearing intracerebral human tumors (U373 or U87 glioblastoma, MDA-MB-435 melanoma, or patient-derived non-small-cell lung cancer [NSCLC]) were treated with sagopilone 5-10 mg/kg, paclitaxel 8-12.5 mg/kg (or temozolomide, 100 mg/kg) or control (vehicle only). Tumor volume was measured to assess antitumor activity. Sagopilone crossed the blood-brain barrier in both rat and mouse models, leading to therapeutically relevant concentrations in the brain with a long half-life. Sagopilone exhibited significant antitumor activity in both the U373 and U87 models of human glioblastoma, while paclitaxel showed a limited effect in the U373 model. Sagopilone significantly inhibited the growth of tumors from CNS metastasis models (MDA-MB-435 melanoma and patient-derived Lu7187 and Lu7466 NSCLC) implanted in the brains of nude mice, in contrast to paclitaxel or temozolomide. Sagopilone has free access to the brain. Sagopilone demonstrated significant antitumor activity in orthotopic models of both glioblastoma and CNS metastases compared with paclitaxel or temozolomide, underlining the value of further research evaluating sagopilone in the treatment of brain tumors. Sagopilone is currently being investigated in a broad phase II clinical trial program, including patients with glioblastoma, NSCLC, breast cancer, and melanoma.     

Selective blood-brain barrier permeabilization of brain metastases by a type 1 receptor-selective tumor necrosis factor mutein

BackgroundMetastasis to the brain is a major challenge with poor prognosis. The blood-brain barrier (BBB) is a significant impediment to effective treatment, being intact during the early stages of tumor development and heterogeneously permeable at later stages. Intravenous injection of tumor necrosis factor (TNF) selectively induces BBB permeabilization at sites of brain micrometastasis, in a TNF type 1 receptor (TNFR1)-dependent manner. Here, to enable clinical translation, we have developed a TNFR1-selective agonist variant of human TNF that induces BBB permeabilization, while minimizing potential toxicity.MethodsA library of human TNF muteins (mutTNF) was generated and assessed for binding specificity to mouse and human TNFR1/2, endothelial permeabilizing activity in vitro, potential immunogenicity, and circulatory half-life. The permeabilizing ability of the most promising variant was assessed in vivo in a model of brain metastasis.ResultsThe primary mutTNF variant showed similar affinity for human TNFR1 than wild-type human TNF, similar affinity for mouse TNFR1 as wild-type mouse TNF, undetectable binding to human/mouse TNFR2, low potential immunogenicity, and permeabilization of an endothelial monolayer. Circulatory half-life was similar to mouse/human TNF and BBB permeabilization was induced selectively at sites of micrometastases in vivo, with a time window of ≥24 hours and enabling delivery of agents within a therapeutically relevant range (0.5-150 kDa), including the clinically approved therapy, trastuzumab.ConclusionsWe have developed a clinically translatable mutTNF that selectively opens the BBB at micrometastatic sites, while leaving the rest of the cerebrovasculature intact. This approach will open a window for brain metastasis treatment that currently does not exist.     

The fibrinolytic system facilitates tumor cell migration across the blood-brain barrier in experimental melanoma brain metastasis

Background  

Patients with metastatic tumors to the brain have a very poor prognosis. Increased metastatic potential has been associated with the fibrinolytic system. We investigated the role of the fibrinolytic enzyme plasmin in tumor cell migration across brain endothelial cells and growth of brain metastases in an experimental metastatic melanoma model.     

Adenosine A2A receptor activation reduces brain metastasis via SDF-1/CXCR4 axis and protecting blood-brain barrier

Brain metastasis is a leading cause of death worldwide, but the mechanism involved remains unclear. Stromal cell-derived factor-1 (SDF-1)/C-X-C motif chemokine receptor 4 (CXCR4) signaling has been reported to induce the directed metastasis of cancers, and adenosine A2A receptor activation suppresses the SDF-1/CXCR4 interaction. However, whether A2A receptor activation implicates the SDF-1/CXCR4 signaling pathway and thus modulates brain metastasis remains unclear. In this study, Western blot was performed to evaluate the protein levels. Cell invasion and migration assays were used to estimate the metastasis ability of PC-9 cells. The viability of cells was demonstrated by lactate dehydrogenase and cell proliferation assays. And the findings in vitro were further identified in nude mice. Notably, adenosine A2A receptor activation inhibited the proliferation and viability of PC-9 cells and thus suppressed the brain metastasis. A2A receptor stimulation protected the function of blood-brain barrier (BBB). The suppression of brain metastasis and the protection of BBB by A2A receptor relied on SDF-1/CXCR4 signaling, and treatment using A2A receptor agonist and CXCR4 antagonist protected the nude mice from malignancy metastasis in vivo. Adenosine A2A receptor activation suppressed the brain metastasis by implicating the SDF-1/CXCR4 axis and protecting the BBB.     

Involvement of P-glycoprotein in an in vitro blood-brain barrier model

The P-glycoprotein (P-gp) multidrug transporter is present at the luminal face of the brain capillary endothelial cells that contribute to the blood-brain barrier. To study its role in transendothelial anticancer drug transport, we made use of a co-culture system formed of bovine brain capillary endothelial cells and astrocytes which allows the in vitro maintenance of specialized properties of the brain endothelial cells, including expression of P-gp as assessed by Northern and Western blot analyses. Vinblastine, an anticancer drug substrate for P-gp and known not to enter the brain, was found to be poorly transferred across the endothelial cell monolayer. This low vinblastine transport was however strongly increased in the presence of verapamil, a well known P-gp blocker. Moreover, verapamil was shown to increase the accumulation of the anticancer drug in the brain endothelial cells through inhibition of drug efflux. These results suggest that P-gp activity evidenced in the co-culture model is involved in the low transendothelial transport of vinblastine, thus supporting the conclusion that P-gp expressed at the blood-brain barrier level may prevent xenobiotics, including anticancer drugs, from entering the central nervous system.     

Intracerebral chemotherapy in the 9L rat brain tumor model

Summary We have used the 9L rat brain tumor model to search for effective chemotherapeutic approaches to the management of brain tumors. Several antineoplastic agents which have been proposed or are currently being used for human brain tumors, including 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU), bleomycin, aziridinylbenzoquinone (AZQ), cis-Platinum, and acivicin, were administered intravenously (iv), intraperitoneally (ip), or intracerebrally (ic) to rats burdened with the intracranial 9L gliosarcoma. The results confirm that BCNU is the most effective systemic agent among the chemotherapeutic agents tested as indicated by its ability to significantly increase the median survival time (MST) and life span of the tumor-burdened animals. Bleomycin is an effective agent against the intracranial 9L tumor when administered ic. While neither systemic single iv dose AZQ (0.5–2.5 mg/kg) nor multiple ip treatments (0.5–1.0 mg/kg × 5, q 6 h) were effective in prolonging the survival, single is dose AZQ (5–50 g/rat) treatment significantly increased the MST of the treated animals (P < 0.05). Systemic AZQ treatments using higher doses produced a hematological toxicity, resulting in a decrease in MST of the treated animals. Cis-Platinum, either administered ip or ic, produced only a marginal effect on survival, although acute neurologic toxicity limited the dose of cis-Patinum that could be administered ic. Acivicin, either administered ip or ic, produced no effect on the survival of treated animals. Our results suggest that local treatment with certain antineoplastic agents may be an efficient therapy in the management of brain tumors.     

Sequential change of capillary permeability in the rat brain after surgical removal of an experimental brain tumor

Summary Experimental brain tumors were excised from rats for sequential observation of changes in local capillary permeability during the postsurgical period. Experimental brain tumor-bearing rats were prepared by stereotaxic transplantation of cultured tumor cells and the resultant tumor was delineated by administration of a dye. Following excision of the stained tumor by craniotomy, sequential changes in local capillary permeability were quantitatively followed-up by autoradiography, using¹⁴C-amino-isobutyric acid as a tracer. Capillary permeability was enhanced following surgery, reaching a maximum both in the extent and degree on the third day. After undergoing a gradual reduction, it showed a marked increase for the second time in a very small area on the 10th postoperative day. A recurrence of the tumor was responsible for this late but marked increase. For a control group, the caudate nucleus was excised from normal rats, followed by observation of the sequential changes in the local capillary permeability. Due to surgical procedure, capillary permeability reached a maximum both in the extent and degree on the 5th postoperative day (slightly later than in the tumor group). This change in capillary permeability was less pronounced than in the tumor group. The difference in the conditions of surgery — tumor excision and partial excision of a normal brain tissue — appeared to explain this difference. The results of this study indicated that it is more desirable to give water-soluble antineoplastic agents early during the postoperative period for chemotherapy of a malignant brain tumor after surgery.     

Measurements of blood-brain barrier permeability in patients undergoing radiotherapy and chemotherapy for primary cerebral lymphoma

Positron emission tomography (PET) has been used to measure changes in regional blood-brain barrier (BBB) permeability in patients with primary cerebral lymphoma undergoing radiotherapy and chemotherapy. The method employed is to measure the rate of wash-out of a radioactive tracer (⁶⁸Ga-EDTA) from blood into brain tissue using time-sequence PET imaging. Preliminary studies carried out on patients with more common primary cerebral tumours show that time-activity data are reproducible to ∼10%. Measurements made in 2 patients with primary cerebral lymphoma treated with initial chemotherapy showed significant changes in permeability in the region of the tumour. Within 5 weeks of the start of treatment, permeability values reached the levels of normal brain. No changes in BBB permeability in normal brain were seen immediately after radiotherapy.     

Putrescine diffusion in cat brain and capillary permeability in rat brain: Relation to CSF putrescine levels in brain tumor patients

Cerebrospinal fluid (CSF) putrescine (Pu) levels are extremely useful measures of active tumor growth in patients harboring medulloblastoma but not in patients harboring most supratentorial malignant gliomas. This study was designed to determine the diffusion coefficient (D) for Pu in cat brain and the capillary permeability coefficient (P_c) in rat brain to explain the failure of supratentorial gliomas to manifest a consistent increase in CSF Pu with progressive tumor growth. The P_c for Pu was found to be greater than the P_c for urea, while the apparent brain D for Pu was lower than that for urea. This implies that Pu crosses capillaries and enters cells more rapidly than urea, which would reduce the amount of Pu that might ultimately reach the CSF by diffusion from tumor. These data explain why CSF levels of Pu are correlated best in medulloblastoms—generally located adjacent to the CSF pathways—and why levels are correlated least in malignant supratentorial gliomas—usually located within the brain hemispheres, from which diffusion to the ventricles and into the CSF would be difficult.     

Influence of blood-brain barrier efflux pumps on the distribution of vincristine in brain and brain tumors

Vincristine (VCR) is efficacious in some but not all brain cancers and an established substrate of Pgp and Mrp1. However, the extent to which such transporters affect the VCR penetration through the blood-brain barrier (BBB) is poorly understood. To evaluate the role of Pgp and Mrp1 in VCR CNS distribution, VCR concentrations were analyzed under steady-state conditions in normal brain, brain tumor, and bone marrow in wild-type (WT), Mrp1 ko (mrp1−/−), Pgp ko (mdr1a−/−:mdr1b−/−), and TKO (mdr1a−/−:mdr1b−/−:mrp1−/−) mice. VCR normal brain partition coefficients (i.e. tissue/plasma VCR concentrations) in TKO mice were greater than those in WT mice at both targeted 10 and 50 ng/mL plasma VCR concentrations, and ranged from 1.3- to 3.6-fold. VCR brain tumor partition coefficients in Mrp1 mice were greater than WT mice at both doses, being 1.5- and 2.4-fold higher at low and high doses, respectively. TKO mice also showed elevated VCR brain tumor penetration with a brain tumor partition coefficient of 1.9-fold greater than that in WT mice at the high-dose level. The bone marrow partition coefficient in Mrp1 ko mice was 1.65-fold greater than that in WT mice. Within strain comparisons revealed that VCR brain tumor concentrations were significantly greater than normal brain in all strains, ranging from 9- to 40-fold. These findings indicate that disruption of the BBB caused the largest enhancement in VCR tumor concentrations, yet the absence of Mrp1 on the brain tumor vasculature could enhance the penetration compared with that in normal brain.     

Serum S100beta: a noninvasive marker of blood-brain barrier function and brain lesions

BACKGROUND: S100beta protein is expressed constitutively by brain astrocytes. Elevated S100beta levels in cerebrospinal fluid and serum reported after head trauma, subarachnoid hemorrhage, and stroke were correlated with the extent of brain damage. Because elevated serum S100beta also was shown to indicate blood-brain barrier (BBB) dysfunction in the absence of apparent brain injury, it remains unclear whether elevation of serum levels of S100beta reflect BBB dysfunction, parenchymal damage, or both. METHODS: The authors conducted a prospective study of serum S100beta levels in six patients who underwent hyperosmotic BBB disruption (BBBD) with intraarterial chemotherapy for primary central nervous system lymphoma. In addition, 53 serum S100beta samples were measured in 51 patients who had a variety of primary or metastatic brain lesions at the time of neuroimaging. RESULTS: S100beta was correlated directly with the degree of clinical and radiologic signs of BBBD in patients who were enrolled in the hyperosmotic study. In patients with neoplastic brain lesions, gadolinium enhancement on a magnetic resonance image was correlated with elevated S100beta levels (n = 45 patients; 0.16 +/- 0.1 microg/L; mean +/- standard error of the mean) versus nonenhancing scans (n = 8 patients; 0.069 +/- 0.04 microg/L). Primary brain tumors (n = 8 patients; 0.12 +/- 0.08) or central nervous system metastases also presented with elevated serum S100beta levels (n = 27 patients; 0.14 +/- 0.34). Tumor volume was correlated with serum S100beta levels only in patients with vestibular schwannoma (n = 6 patients; 0.13 +/- 0.10 microg/L) but not in patients with other brain lesions. CONCLUSIONS: S100beta was correlated directly with the extent and temporal sequence of hyperosmotic BBBD, further suggesting that S100beta is a marker of BBB function. Elevated S100beta levels may indicate the presence of radiologically detectable BBB leakage. Larger prospective studies may better determine the true specificity of S100beta as a marker for BBB function and as an early detection or follow-up marker of brain tumors.     

Chemotherapy administered in conjunction with osmotic blood-brain barrier modification in patients with brain metastases

Clinical experience in seven patients with systemic malignancies (breast, lung and testicular) metastatic to the central nervous system treated with chemotherapy given in association with reversible osmotic blood-brain barrier modification is reviewed. A combination chemotherapy regimen including intra-arterial methotrexate, intravenous cytoxan and oral procarbazine in conjunction with intra-arterial mannitol infusions was successfully carried out with minimal toxicity. The results in these patients demonstrate some therapeutic efficacy to the increased drug delivery achieved with this technique. Although suggestive, additional studies will be required to confirm that barrier modification is a key parameter in such efficacy.