Adoptive transfer via immune T-lymphocytes of effective anti-tumor immunity against a malignant rat glioma in the brain

The aim of the present study was to develop an animal model to test the therapeutic potential of purified CD4 and CD8 T-lymphocytes against the intracerebrally implanted rat glioma cell line TZ363. Peripheral immunization of donor rats was performed by subcutaneous injection of viable TZ363 tumor cells while control animals received buffer injection. Donor splenic T-lymphocytes were prepared 14 days later and enriched by immune-bead MACS sorting. FACScan analysis revealed that of the pooled and sorted cells 91% of the tumor immune group were T-lympocytes and from the control animals 96%. The purified immune CD4/CD8 T-lymphocytes (1.2 to 5x10(7) cells) were injected intraperitoneally into 12 adult rats (three groups; each four animals), which were challenged five days later by an intracerebral injection of 5x10(4) TZ363 glioma cells. Four rats received 1.4x10(7) T-cells from control animals. While 3 of 4 animals developed a brain tumor and died in the control group, all animals, which received 5x10(7) immune T-cells survived the intracerebral tumor challenge. In the other groups survival rate depended on the amount of T-cells given. All other rats were sacrificed 32 days after intracerebral grafting. No tumor was found in these animals. Our data demonstrate that an anti-tumor T-cell response can be raised against the malignant rat glioma TZ363 and that purified CD4 and CD8 T-lymphocytes from tumor immunized donors can transfer protective immunity across the blood-brain barrier into recipient rats which are tumor challenged intracerebrally.     

A combination of chemoimmunotherapies can efficiently break self-tolerance and induce antitumor immunity in a tolerogenic murine tumor model

Her-2/neu is a well-characterized tumor-associated antigen overexpressed in human carcinomas such as breast cancer. Because Her-2/neu is a self-antigen with poor immunogenicity due to immunologic tolerance, active immunotherapy targeting Her-2/neu should incorporate methods to overcome immunologic tolerance to self-proteins. In this study, we developed a tolerogenic tumor model in mice using mouse Her-2/neu as self-antigen and investigated whether genetic vaccination with DNA plasmid and/or adenoviral vector expressing the extracellular and transmembrane domain of syngeneic mouse Her-2/neu or xenogenic human Her-2/neu could induce mouse Her-2/neu-specific CTL responses. Interestingly, adenoviral vectors expressing xenogenic human Her-2/neu (AdhHM) proved capable of breaking immune tolerance and of thereby inducing self-reactive CTL and antibodies, but not to the degree required to induce therapeutic antitumor immunity. In attempting to generate therapeutic antitumor immunity against established tumors, we adopted several approaches. Treatment with agonistic anti-glucocorticoid-induced TNFR family-related receptor (GITR) antibody plus AdhHM immunization significantly increased self-reactive CTL responses, and alpha-galactosylceramide (alphaGalCer)-loaded dendritic cells (DC) transduced with AdhHM were shown to break self-tolerance in a tolerogenic murine tumor model. Furthermore, gemcitabine treatment together with either AdhHM plus agonistic anti-GITR antibody administration or alphaGalCer-loaded DC transduced with AdhHM showed potent therapeutic antitumor immunity and perfect protection against preexisting tumors. Gemcitabine treatment attenuated the tumor-suppressive environment by eliminating CD11b(+)/Gr-1(+) myeloid-derived suppressor cells. When combined with immunotherapies, gemcitabine offers a promising strategy for the Ag-specific treatment of human cancer.     

Oncolytic poliovirus therapy and immunization with poliovirus-infected cell lysate induces potent antitumor immunity against neuroblastoma in vivo

In a previous study, we demonstrated that neuroblastoma subcutaneously implanted in immuno-competent mice is eliminated by intratumoral administration of neuroattenuated poliovirus (PV). Our results also suggested that the in vivo destruction of neuroblastoma cells by virotherapy lead to a robust antitumor immune response. In this work, splenocytes harvested from neuroblastoma-bearing animals treated with neuroattenuated PV exhibited significantly higher lytic activity against tumor target cells than did those from splenocytes derived from control mice. In vitro T-cell depletion experiments indicated that CD8(+) T cells were essential for the cytotoxic antitumor activity of splenocytes. Moreover, adoptive transfer of splenocytes obtained from mice cured of neuroblastoma by PV virotherapy markedly delayed the tumor growth of previously established neuroblastomas in recipient na?ve mice. These results confirmed that treatment with a neuroattenuated oncolytic PV strain induces antitumor immunity against neuroblastoma that is mainly mediated by cytotoxic CD8(+) T cells. Immunocompetent mice, on the other hand, were immunized with PV-infected neuroblastoma cell lysate prior intravenous challenge with neuroblastoma cells. As a control, mice were vaccinated with either non-infected neuroblastoma cell lysate alone or mixed with PV, or with PBS prior tumor cell injection. Results showed that survival is significantly prolonged only in mice immunized with PV-infected tumor lysate. This finding clearly suggested that in vitro poliovirus infection of neuroblastoma cells turns these cells into a potent tumor immunogen. Further studies in oncolytic treatment of neuroblastoma using attenuated PV alone or in combination with immunotherapy with PV oncolysate should improve the probability for successful translation in the clinic.     

Interstitial delivery of carboplatin via biodegradable Polymers is effective against experimental glioma in the rat

 Purpose: Carboplatin has shown promise experimentally as an antineoplastic agent against both primary central nervous system (CNS) tumors and several solid tumors that frequently metastasize to the brain. Unfortunately, carboplatin is limited in its clinical use for tumors in the CNS by systemic toxicity and poor penetration through the blood–brain barrier. Recent advances in polymer technology have made feasible the intracranial implantation of a biodegradable polymer capable of local sustained delivery of chemotherapy for brain neoplasms. This study assessed the toxicity and efficacy of carboplatin delivered from intracranial sustained release polymers in the treatment of experimental gliomas in rodents. Methods: Two biodegradable anhydride polymer systems were tested: a copolymer of 1,3-bis-(p-carboxyphenoxy propane) and sebacic acid, and a copolymer of fatty acid dimer and sebacic acid. The polymers were loaded with carboplatin and dose escalation studies evaluating toxicity were performed by implanting carboplatin-loaded polymers into the brains of rats. Next, efficacy was tested. F-98 glioma cells were injected intracranially into rats, and 5 days later polymers containing the highest tolerated doses were implanted at the site of tumor growth. The survival of animals receiving carboplatin-loaded polymer was compared with that of animals receiving intraperitoneal doses of the same agent. Results: Carboplatin-polymer was well tolerated at doses up to 5% loading in both polymer systems. Locally delivered carboplatin effectively prolonged survival of rats with F98 gliomas. Maximal treatment effect was seen with 5% loading of either polymer, with median survival increased threefold over control (P<0.004). Systemic carboplatin also significantly prolonged survival, but the best intracranial polymer dose was significantly more effective than the best systemic dose tested. Conclusions: Carboplatin can be safely delivered intracranially by biodegradable sustained-release polymers. This treatment improves survival in rodents with experimental gliomas, with locally delivered carboplatin being more effective than systemic carboplatin. Received: 25 August 1995/Accepted: 21 February 1996     

O6-benzylguanine potentiates the antitumor effect of locally delivered carmustine against an intracranial rat glioma

Local delivery of carmustine (BCNU) via biodegradable polymers prolongs survival against experimental brain tumors and in human clinical trials. O6-benzylguanine (O6-BG), a potent inhibitor of the DNA repair protein, O6-alkylguanine-DNA alkyltransferase (AGT), has been shown to reduce nitrosourea resistance and, thus, enhance the efficacy of systemic BCNU therapy in a variety of tumor models. In this report, we demonstrate that O6-BG can potentiate the activity of BCNU delivered intracranially via polymers in rats challenged with a lethal brain tumor. Fischer 344 rats received a lethal intracranial challenge of 100,000 F98 glioma cells (F98 cells have significant AGT activity, 328 fmol/mg protein). Five days later, animals receiving an i.p. injection of O6-BG (50 mg/kg) 2 h prior to BCNU polymer (3.8% BCNU by weight) implantation had significantly improved survival (n = 7; median survival, 34 days) over animals receiving either O6-BG alone (n = 7; median survival, 22 days; P = 0.0002) or BCNU polymer alone (n = 8; median survival, 25 days; P = 0.0001). Median survival for the control group (n = 8) was 23.5 days. Moreover, there was no physical, behavioral, or pathological evidence of treatment-related toxicity. These findings suggest that O6-BG can potentiate the effects of interstitially delivered BCNU and, for tumors expressing significant AGT, may be necessary for the BCNU to provide a meaningful therapeutic benefit. Given the clinical use of BCNU polymers against malignant gliomas, concurrent treatment with O6-BG may provide an important addition to our therapeutic armamentarium.     

Expression of lymphocyte-specific chemokines in human malignant glioma: Essential role of LARC in cellular immunity of malignant glioma

Lymphocytes are frequently observed in human malignant glioma, the mechanism(s) underlying their appearance is not fully understood. To clarify tumor immunity in malignant gliomas, we analyzed the expression of 8 novel lymphocyte-specific chemokines in human glioma cell lines and glioma tissues by RT-PCR, Northern blot, immunoblot and immunohistochemistry, and examined the correlation with the infiltration of various subsets of lymphocytes. For the 8 chemokines examined (LARC, TARC, ELC, SLC, PARC, LEC, HCC-2, and SCM-1alpha), expression of LARC was clearly detectable in all 12 glioma cell lines by RT-PCR. Additionally, expression of TARC and SCM-1alpha was detectable in the majority of glioma cell lines. However, the expression level of most chemokines was low, so that Northern blot analysis could not demonstrate their expression with the exception of LARC in 2 cell lines. Expression of LARC mRNA and LARC protein was strongly induced by phorbol myristate ester in U87 MG cells. The production of LARC protein was demonstrated in 4 of 8 glioblastoma tissues by immunoblotting, and 9 of 33 samples (27.3%) by immunohistochemistry. Interestingly, the positivity of LARC staining was significantly correlated with the infiltration of CD8-, CD4-, and CD45R0-positive cells (p<0.001). Although the constitutive expression level of LARC is low, certain stimulations could strongly induce its expression, and play a crucial role in the tumor immunity of human malignant glioma.     

In vitro chemosensitivity test with several antitumor agents against eight malignant brain tumor cell-lines

We performed an in vitro chemosensitivity test with 8 malignant brain tumor cell lines, which were established in our Department. It was shown that ACNU was moderately tumoricidal against only one cell (ONS-86) line. IFN-beta (interferon-beta) was more active against 4 cell (ONS-6, -20, -76, and -81) lines. VCR (vincristine), MTX (methotrexate), and Ara-C (cytosine arabinoside) and FK 973 were most effective against all 8 cell lines. There were some difference in the drug sensitivities among the tumors with the same pathological diagnosis. Since IFN-beta was tumoricidal against to the cells, co-culture of IFN-beta and one of other antitumor agents seemed to induce more antitumor effects. With regard to the side effects of IFN-beta, the combined therapy with IFN-beta and other drugs induced more antitumor effects against malignant brain tumor cells and seemed to reduce the side effects.     

瘤内注射吉西他滨治疗大鼠脑胶质瘤的效果观察

目的 观察吉西他滨瘤内给药治疗大鼠脑胶质瘤的效果,探讨治疗脑胶质瘤的有效化疗途径及药物.方法 50只SD大鼠随机分为对照组（5只）,肿瘤组和治疗（1 mg/ml）组和治疗（4mg/ml）组,每组15只.除对照组外,所有大鼠均在纹状体部埋植导管,并接种9L胶质瘤细胞株以建立在体脑胶质瘤模型.治疗组于植入瘤细胞第9天,通过导管将吉西他滨（10μl,1 mg/ml和4 mg/ ml）分别注入瘤内.于给药第9天,每组随机取脑抽检（5只）,观察瘤形态及大小;余者（每组10只）观察其饮食、行为、体质量及存活期,评价吉西他滨对大鼠脑胶质瘤的治疗效果.结果 于瘤内注入吉西他滨第9天取脑,发现各组肿瘤大小分别为：肿瘤组（44.69±7.52） mm3、治疗（1 mg/ml）组（22.44±5.37） mm3和治疗（4 mg/ml）组（18.72±7.13）mm3,肿瘤组与两治疗组间差异有统计学意义（P＜0.05）,但两治疗组之间差异无统计学意义（P＞0.05）.治疗组大鼠体质量下降较肿瘤组为轻.肿瘤组平均存活期为23.8d.4 mg/ml组1只存活期比肿瘤组短,剩余4只及全部1 mg/ml组（10只）均长于肿瘤组.结论 吉西他滨可抑制脑胶质瘤生长,缓解大鼠体质量下降,延长模型动物存活期,对大鼠脑胶质瘤具有抑制作用.     

Cytotoxicity of taxol in vitro against human and rat malignant brain tumors

Taxol is a novel antitumor alkaloid that has shown clinical activity against several tumors, including ovarian and breast carcinoma and melanoma. To evaluate taxol's potential as a therapy for malignant brain tumors, we measured the sensitivity of four human (U87, U373, H80, and D324) and two rat (9L, F98) brain-tumor cell lines to taxol. The cells were exposed to taxol in vitro using a clonogenic assay. Log cell kill (LD₉₀) occurred at concentrations of 42 (9L), 25 (F98), 19 (H80), 7.2 (U373), 9.1 (U87), and 3.9 nM (D324) when cells were continuously exposed to taxol for 6–8 days. The human cell lines were uniformly more sensitive to taxol than were the rat lines. The duration of exposure had a significant effect on taxol's cytotoxicity. When cells were exposed to taxol for 1 h the LD₉₀ increased to 890 nM for the 9L rat line and 280 nM for the human U373 line. On the basis of these results, we conclude that taxol has significant potency in vitro against malignant brain tumors and that the activity occurs at concentrations of taxol that have previously been shown to be effective for several tumors against which the drug is currently being evaluated clinically.     

Modification in the diet can induce beneficial effects against breast cancer

The population tends to consume foods that in addition to their nutritional values can offer some benefits to their health. There are many epidemiological evidences and research studies in animal models suggesting that diet plays an important role in breast cancer prevention or progression. This review summarized some of the relevant researches about nutrition and cancer during the last years, especially in breast cancer. The analysis of probiotics and fermented products containing lactic acid bacteria in cancer prevention and/or treatment was especially discussed. It was observed that a balance of fatty acids similar to those of traditional Mediterranean diet, the consumption of fruits and vegetables, dietary fiber intake, vitamin supplementation are, along with the intake of probiotic products, the most extensively studied by the negative association to breast cancer risk. The consumption of probiotics and fermented products containing lactic acid bacteria was associated to reduce breast cancer risk in some epidemiological studies. The use of animal models showed the modulation of the host’s immune response as one of the important effects associated to the benefices observed with most probiotics. However; future assays in human are very important before the medical community can accept the addition of probiotic or fermented milks containing lactic acid bacteria as supplements for cancer patients.     

Fas ligand-expressing tumors induce tumor-specific protective immunity in the inoculated hosts but vaccination with the apoptotic tumors suppresses antitumor immunity

The interaction between Fas and Fas ligand (FasL) is involved in the apoptotic death of a number of cells including lymphocytes. Forced expression of FasL in tumors can induce apoptosis of infiltrating Fas-positive T cells; accordingly, tumors can survive in the milieu of systemic immune responses. However, FasL-expressing murine lung carcinoma (A11) and melanoma (B16) cells did not develop subcutaneous tumors and FasL-expressing A11 (A11/FasL) cells produced few spontaneous lung metastatic foci in syngeneic mice. The mice that rejected A11/FasL cells were resistant to subsequent challenge of parent A11 but not irrelevant B16 cells. Vaccination of mice with UV-treated A11/FasL, but not UV-treated A11 cells, however, augmented the growth rate of A11 but not B16 tumors, both of which were subsequently inoculated. The number of lung metastatic foci of A11 cells was also increased in the mice that received UV-treated A11/FasL but not UV-treated A11 cells. Intraperitoneal injection of UV-treated A11/FasL cells resulted in the production of larger amounts of immunosuppressive TGF-beta in peritoneal exudate than that of UV-treated A11 cells. Expression of the CD80 costimulatory molecule in tissues where UV-treated A11/FasL cells were inoculated was lower than the expression at an untreated A11/FasL-injected site. Our results indicated that apoptotic FasL-expressing tumor cells could impair host immune responses against the tumors, in contrast to potent antitumor immunity generated by viable FasL-expressing tumors.     

Convection-enhanced delivery of Ls-TPT enables an effective, continuous, low-dose chemotherapy against malignant glioma xenograft model

Treatment of malignant gliomas represents one of the most formidable challenges in oncology. The combination of surgery, radiation, and chemotherapy yields median survivals of less than one year. Here we demonstrate the use of a minimally invasive surgical technique, convection-enhanced delivery (CED), for local administration of a novel nanoparticle liposome containing topotecan. CED of this liposomal topotecan (Ls-TPT) resulted in extended brain tissue retention (t1/2 = 1.5 days), whereas free topotecan was rapidly cleared (t1/2 = 0.1 days) after CED. The favorable pharmacokinetic profile of extended topotecan release for about seven days, along with biodistribution featuring perivascular accumulation of the nanoparticles, provided, in addition to the known topoisomerase I inhibition, an effective antiangiogenic therapy. In the rat intracranial U87MG tumor model, vascular targeting of Ls-TPT with CED was associated with reductions in laminin expression and vascular density compared to free topotecan or control treatments. A single CED treatment on day 7 showed that free topotecan conferred no survival benefit versus control. However, Ls-TPT produced a significant (P = 0.0002) survival benefit, with six of seven complete cures. Larger U87MG tumors, where CED of Ls-TPT on day 12 resulted in one of six cures, indicated the necessity to cover the entire tumor with the infused therapeutic agent. CED of Ls-TPT was also efficacious in the intracranial U251MG tumor model (P = 0.0005 versus control). We conclude that the combination of a novel nanoparticle Ls-TPT and CED administration was very effective in treating experimental brain tumors.     

9-Amino acridine pharmacokinetics, brain distribution, and in vitro/in vivo efficacy against malignant glioma

Purpose

The delivery of drugs to the brain is a major obstacle in the design and development of useful treatments for malignant glioma. Previous studies by our laboratory have identified a series of 9-amino acridine compounds that block the catalytic cycle of topoisomerase II resulting in apoptosis and cell death in a variety of cancer cell lines.

Methods

This study reports the in vitro and in vivo activity of two promising lead compounds, [{9-[2-(1H-Indol-3-yl)-ethylamino]-acridin-4-yl}-(4-methyl-piperazin-1-yl)-methanone (1) and [9-(1-Benzyl-piperidin-4-ylamino)-acridin-3-yl]-(4-methyl-piperazin-1-yl)-methanone] (2), using an orthotopic glioblastoma mouse model. In addition, the absorption, distribution, and metabolism properties are characterized by determining metabolic stability, MDCK accumulation, Pgp efflux transport, plasma protein binding, and brain distribution in mouse pharmacokinetic studies.

Results

The efficacy results indicate low micromolar ED₅₀ values against glioma cells and a significant increase in the survival of glioma-bearing mice dosed with (2) (p?1 and 2 showed both compounds penetrate the blood–brain barrier yielding peak concentrations of 0.25?μM and 0.6?μM, respectively. Peak plasma concentrations were determined to be 2.25?μM (1) and 20.38?μM (2). The results were further compared with data collected using a 15?mg/kg intravenous dose of 2 which yielded a peak concentration in the brain of 1.7 μM at 2.0?h relative to a 2.04 μM peak plasma concentration. The bioavailability was calculated to be 83.8%.

Conclusion

Taken overall, the results suggest compounds in this series may offer new strategies for the design of chemotherapeutics for treating brain cancers with high oral bioavailability and improved efficacy.     

Transfection of the gene for B7-1 but not B7-2 can induce immunity to murine malignant mesothelioma

Transfection of the genes encoding the co-stimulatory molecules B7-1 and B7-2 has enhanced the development of immunity to a variety of experimental tumors, although most of these were inherently immunogenic. We have determined the effect of expression of these genes on the induction of immunity to 2 non-immunogenic murine malignant mesothelioma (MM) cell lines (AC29 and AB1). We had previously shown that B7-1 transfection into AC29 delayed but did not prevent tumor development by certain of the transfectant clones. Here we demonstrate that over-expression of B7-1 can inhibit tumor development by certain AB1-B7-1 clones, that inhibition of transfectant growth is dependent on CD4⁺ and CD8⁺ T cells and that mice that reject some of these transfectant clones are capable of rejecting subsequent inocula of the parental cell line, AB1. The transfectant clones can generate tumor-specific cytotoxic T cells. By contrast, expression of B7-2 in several clones derived from either AB1 or AC29 had no significant effect on the development of tumors in vivo. Our data are consistent with data from other systems that show differences in the effect of modification by B7-1 or B7-2 on the modulation of anti-tumor immune responses. They demonstrate that such modifications can induce protective immunity against an MM cell line but confirm the intra- and inter-tumoral heterogeneity in the effect of genetic modification on the induction of immunity. Our observations are relevant to human MM because these cell lines have been derived from asbestos-induced tumors and share many properties with human cell lines of the same histological type. Int. J. Cancer 71:476-482, 1997. © 1997 Wiley-Liss Inc.     

Selective retention of rhodamine-123 by malignant glioma in the rat

Levels of rhodamine 123 (Rh-123), a new antineoplastic drug, were measured using high performance liquid chromatography in normal brain, malignant glioma and brain adjacent to tumor after a single intravenous injection of drug into rats with intracerebral tumors. Consistently higher levels of Rh-123 were seen in tumor compared to normal brain at all times. Tumor levels of Rh-123 increased up to a maximum level of 9.35 nm/mg at 5 hours after intravenous injection (10 mg/kg), afterwhich Rh-123 levels slowly decreased. Rh-123 concentration in serum reached a maximum level immediately after intravenous injection and Rh-123 was eliminated from the serum according to first order kinetics. The delayed (5 hours after injection) increase in tumor concentration of Rh-123 may reflect tumor hypoperfusion and/or the time required for the compound to diffuse from the blood to the cells within the tumor due to the blood brain barrier. These findings have directed us to study low dose continuous infusion and direct intratumoral injection of Rh-123 as ways of achieving higher Rh-123 levels in tumor with less risk of systemic toxicity due to elevated serum Rh-123 levels.     

Target volumes in radiotherapy for high-grade malignant glioma of the brain.

Delineation of the clinical target volume (CTV) in radiation treatment planning of high-grade glioma is a controversial issue. The use of computerized tomography (CT) and magnetic resonance imaging (MRI) has greatly improved the accuracy of tumor localization in three-dimensional planning. This review aims at critically analyzing available literature data in which tumor extent of high-grade glioma has been assessed using CT and/or MRI and relating this to postmortem observations. Attention is given to the pattern of tumor spread at initial presentation and to tumor recurrence pattern after external beam irradiation. Special emphasis is given to the site of tumor regrowth after radiation treatment in relation to the boundaries of the CTV. Guidelines for delineating CTV will be inferred from this information, taking data on radiation effects on the normal brain into account.     

The mechanism of chemoresistance against tyrosine kinase inhibitors in malignant glioma

Glioblastoma (GBM) is one of the most lethal malignancies in humans, and novel therapeutic strategies are urgently required for its treatment. Tyrosine kinases (TKs) play a pivotal role in intercellular signal transduction and regulate crucial processes of tumor cell biological activities in GBM. This information provides the basis for the molecular target therapies for GBMs. TK inhibitors (TKIs) are expected to be effective therapeutic strategies. However, one important limitation is that GBMs exhibit marked resistance to the TKIs currently available, yet the mechanisms underlying TKI resistance have not been fully characterized. In the current review, we will address the varieties of chemoresistance mechanisms against TKIs in GBM. The mechanisms responsible for TKI refractoriness in GBMs are divided into 2 aspects. The first includes tumor-related concerns, such as a lack of target expression, the multiplicity of targets, redundancy, the appearance of resistant cells, and tumor changes in characteristics. The second includes drug-related concerns, such as inefficient drug effects, delivery, pharmacokinetics, and intolerable side effects. A better understanding of these mechanisms is needed to develop accurate tests to predict the lack of response to TKIs and for developing novel approaches aimed at overcoming the resistance to TKIs.     

Potent antitumor effect of SN‐38‐incorporating polymeric micelle,NK012, against malignant glioma

Recent published reports on clinical trials of CPT‐11 indicate the effectiveness of this compound, a prodrug of SN‐38, against malignant glioma in combination with anti‐vascular endothelial growth factor antibody. Here, we determined if NK012, and SN‐38 incorporating micelle, can be an appropriate formulation for glioblastoma treatment compared with CPT‐11. In vitro cytotoxicity was evaluated against several glioma lines with NK012, CPT‐11, SN‐38, ACNU, CDDP and etoposide. For the in vivo test, a human glioma line (U87MG) transfected with the luciferase gene was inoculated into nude mice brain for pharmacokinetic analysis by fluorescence microscopy and high‐performance liquid chromatography after intravenous injection of NK012 and CPT‐11. In vivo antitumor activity of NK012 and CPT‐11 was evaluated by bioluminescence image and Kaplan‐Meier analyses. The growth‐inhibitory effects of NK012 were 34‐ to 444‐fold more potent than those of CPT‐11. Markedly enhanced and prolonged distribution of free SN‐38 in the xenografts was observed after NK012 injection compared with CPT‐11. NK012 showed significantly potent antitumor activity against an orthotopic glioblastoma multiforme xenograft and significantly longer survival rate than CPT‐11 (p = 0.0014). This implies that NK012 can pass through the blood brain tumor barrier effectively. NK012, which combines enhanced distribution with prolonged sustained release, may be ideal for glioma treatment. Currently, a phase I study of NK012 is almost complete in Japan and the US. The present translational study warrants the clinical phase II study of NK012 in patients with malignant glioma. © 2008 Wiley‐Liss, Inc.