Drug resistance in brain tumors

2-Deoxy-D-glucose increases the sensitivity of glioblastoma cells to BCNU through the regulation of glycolysis, ROS and ERS pathways: In vitro and in vivo validation

Chloroethylnitrosoureas (CENUs) exert antitumor activity via producing dG-dC interstrand crosslinks (ICLs). However, tumor resistance make it necessary to find novel strategies to improve the therapeutic effect of CENUs. 2-Deoxy-D-glucose (2-DG) is a well-known glycolytic inhibitor, which can reprogram tumor energy metabolism closely related to tumor resistance. Here, we investigated the chemosensitization effect of 2-DG on l,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) against glioblastoma cells and the underlying mechanisms. We found that 2-DG significantly increased the inhibitory effects of BCNU on tumor cells compared with BCNU alone, while 2-DG showed no obvious enhancing effect on the BCNU-induced cytotoxicity for normal HaCaT and HA1800 cells. Proliferation, migration and invasion determinations presented the same trend as survival on tumor cells. 2-DG plus BCNU increased the energy deficiency through a more effective inhibition of glycolytic pathway. Notably, the combination of 2-DG and BCNU aggravated oxidative stress in glioblastoma cells, along with a significant decrease in glutathione (GSH) levels, and an increase in intracellular reactive oxygen species (ROS). Subsequently, we demonstrated that the combination treatment led to increased apoptosis via activating mitochondria and endoplasmic reticulum stress (ERS) related apoptosis pathways. Finally, we found that the dG-dC level was significantly increased after 2-DG pretreatment compared to BCNU alone by HPLC-ESI-MS/MS analysis. Finally, in vivo, 2-DG plus BCNU significantly suppressed tumor growth with lower side effects compared with BCNU alone in tumor-bearing mice. In summary, we proposed that 2-DG may have potential to increase the sensitivity of glioblastoma cells to BCNU by regulating glycolysis, ROS and ERS pathways in clinical setting.

3-Bromopyruvate regulates the status of glycolysis and BCNU sensitivity in human hepatocellular carcinoma cells

Chloroethylnitrosoureas (CENUs) are bifunctional antitumor alkylating agents, which exert their antitumor activity through inducing the formation of dG-dC interstrand crosslinks (ICLs) within DNA double strand. However, the complex process of tumor biology enables tumor cells to escape the killing triggered by CENUs, as for instance with the detoxifying activity of O⁶-methylguanine DNA methyltransferase (MGMT) to accomplish DNA damage repair. Considering the fact that most tumor cells highly depend on aerobic glycolysis to provide energy for survival even in the presence of oxygen (Warburg effect), inhibition of aerobic glycolysis may be an attractive strategy to overcome the resistance and improve the chemotherapeutic effects of CENUs. Especially, 3-bromopyruvate (3-BrPA), a small molecule alkylating agent, has been emerged as an effective glycolytic inhibitor (energy blocker) in cancer treatment. In view of its tumor specificity and inhibition on cellular multiple targets, it is likely to reduce the chemoresistance when chemotherapeutic drugs are combined with 3-BrPA. In this study, we investigated the effects of 3-BrPA on the chemosensitivity of two human hepatocellular carcinoma (HCC) cell lines to the cytotoxic effects of l,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and the underlying molecular mechanism. The sensitivity of SMMC-7721 and HepG2 cells to BCNU was significantly increased by 2 h pretreatment with micromolar dosage of 3-BrPA. Moreover, 3-BrPA decreased the cellular ATP and GSH levels, and extracellular lactate excreted by tumor cells, and the effects were more effective when 3-BrPA was combined with BCNU. Cellular hexokinase-II (HK-II) activity was also reduced after exposure to the treatment of 3-BrPA plus BCNU. Based on the above results, the effects of 3-BrPA on the formation of dG-dC ICLs induced by BCNU was investigated by stable isotope dilution high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The results indicated that BCNU produced higher levels of dG-dC ICLs in SMMC-7721 and HepG2 cells pretreated with 3-BrPA compared to that without 3-BrPA pretreatment. Notably, in MGMT-deficient HepG2 cells, the levels of dG-dC ICLs were significantly higher than MGMT-proficient SMMC-7721 cells. In general, these findings revealed that 3-BrPA, as an effective glycolytic inhibitor, may be considered as a potential clinical chemosensitizer to optimize the therapeutic index of CENUs.

The State of Cellular Adoptive Immunotherapy for Neuroblastoma and Other Pediatric Solid Tumors

Research on adult cancer immunotherapy is proceeding at a rapid pace resulting in an impressive success rate exemplified by a few high profile cases. However, this momentum is not readily extended to pediatric immunotherapy, and it is not for lack of trying. Though reasons for the slower advance are not apparent, some issues can be raised. Pediatric cancer patients represent a distinct demographic group whose immune system is inherently different from that of mature adults. Treating pediatric patients with immunotherapy designed for adults may not yield objective clinical responses. Here, we will present an update on adoptive T-cell and natural killer-cell therapies for neuroblastoma and other childhood solid tumors. Additionally, we will delineate key differences between human fetal/neonatal and adult immune systems. We hope this will generate interests leading to the discussion of potential future directions for improving adoptive cancer immunotherapy for children.

Development and Characterization of Methylene Blue Oleate Salt-Loaded Polymeric Nanoparticles and their Potential Application as a Treatment for Glioblastoma

Glioblastoma (GBM) is an aggressive, grade IV brain tumor that develops from astrocytes located within the cerebrum, resulting in poor prognosis and survival rates following an accepted treatment regimen of surgery, radiation, and temozolomide. Thus, development of new therapeutics is necessary. During the last two decades, methylene blue (MB) has received increased attention as a potential neurotherapeutic due to its duality in brain cancers and neurodegenerative diseases. While MB is capable of easily permeating the blood-brain barrier, its therapeutic concentrations in GBM are known to induce off-target cytotoxicity and thus, another mode of drug delivery must be considered. To this end, encapsulation of formerly unusable compounds into nanoparticles (NPs) made from the biodegradable/biocompatible, FDA approved co-polymer poly (lactide-co-glycolide) (PLGA) has been more commonplace when developing novel therapeutics. In this study, we formulated and characterized Pluronic F68-coated PLGA NPs containing a sodium oleate conjugate of MB (MBOS) via solvent displacement. Conjugation of sodium oleate to MB was shown to reduce its release from PLGA NPs compared to unmodified MB, leading to potential improvements in drug accumulation and therapeutic effectiveness. Our drug-loaded NP preparations, which were ~170 nm in size and had drug loading values of ~2%, were shown to reduce cell viability and cell compartment-specific, as well as overall cell, functions equivalenty, if not more so, when compared to free drug in two GBM cell lines. Following bio-distribution analysis of free MBOS compared to its nano-encapsulated counterpart, drug-loaded NPs were shown to more effectively permeate the BBB, which could lead to improvements in therapeutic effectiveness upon further examination in a tumor-bearing mouse model. Based on these results, we believe that the further development and eventual utilization of this nanoformulation could lead to an effective GBM therapy that could extend patient survival rates.

A new anti-glioma therapy, AG119: pre-clinical assessment in a mouse GL261 glioma model

BACKGROUND

High grade gliomas (HGGs; grades III and IV) are the most common primary brain tumors in adults, and their malignant nature ranks them fourth in incidence of cancer death. Standard treatment for glioblastomas (GBM), involving surgical resection followed by radiation and chemotherapy with temozolomide (TMZ) and the anti-angiogenic therapy bevacizumab, have not substantially improved overall survival. New therapeutic agents are desperately needed for this devastating disease. Here we study the potential therapeutic agent AG119 in a pre-clinical model for gliomas. AG119 possesses both anti-angiogenic (RTK inhibition) and antimicrotubule cytotoxic activity in a single molecule.

METHODS

GL261 glioma-bearing mice were either treated with AG119, anti-VEGF (vascular endothelial growth factor) antibody, anti c-Met antibody or TMZ, and compared to untreated tumor-bearing mice. Animal survival was assessed, and tumor volumes and vascular alterations were monitored with morphological magnetic resonance imaging (MRI) and perfusion-weighted imaging, respectively.

RESULTS

Percent survival of GL261 HGG-bearing mice treated with AG119 was significantly higher (p < 0.001) compared to untreated tumors. Tumor volumes (21-31 days following intracerebral implantation of GL261 cells) were found to be significantly lower for AG119 (p < 0.001), anti-VEGF (p < 0.05) and anti-c-Met (p < 0.001) antibody treatments, and TMZ-treated (p < 0.05) mice, compared to untreated controls. Perfusion data indicated that both AG119 and TMZ were able to reduce the effect of decreasing perfusion rates significantly (p < 0.05 for both), when compared to untreated tumors. It was also found that IC50 values for AG119 were much lower than those for TMZ in T98G and U251 cells.

CONCLUSIONS

These data support further exploration of the anticancer activity AG119 in HGG, as this compound was able to increase animal survival and decrease tumor volumes in a mouse GL261 glioma model, and that AG119 is also not subject to methyl guanine transferase (MGMT) mediated resistance, as is the case with TMZ, indicating that AG119 may be potentially useful in treating resistant gliomas.

CD133 and DNA-PK regulate MDR1 via the PI3K- or Akt-NF-κB pathway in multidrug-resistant glioblastoma cells in vitro

Chemotherapy is an adjuvant treatment for glioblastomas, however, chemotherapy remains palliative because of the development of multidrug resistance (MDR). Following prolonged chemotherapy, MDR protein 1 (MDR1) and CD133 increase in recurrent glioblastomas. CD133 positive (CD133+) glioma cancer stem-like cells (GCSCs) markedly promote drug resistance and exhibit increased DNA damage repair capability; thus they have a key role in determining tumor chemosensitivity. Although CD133, DNA-dependent protein kinase (DNA-PK), and MDR1 are elevated in CD133+ GCSCs, the relationship among these molecules has not been elucidated. In this study, MDR glioblastoma cell lines were created in response to prolonged doxorubicin chemotherapy. CD133, DNA-PK and MDR1 were markedly elevated in these cells. CD133 and DNA-PK may increase MDR1 via the phosphatidylinositol-3-kinase (PI3K)-Akt signal pathway. PI3K downstream targets Akt and nuclear factor (NF)-κB, which interacts with the MDR1 promoter, were also elevated in these cells. Downregulation of CD133 and DNA-PK by small interfering RNA, or inhibition of PI3K or Akt, decreased Akt, NF-κB and MDR1 expression. The results indicate that CD133 and DNA-PK regulate MDR1 through the PI3K- or Akt-NF-κB signal pathway. Consequently, a novel chemotherapeutic regimen targeting CD133 and DNA-PK in combination with traditional protocols may increase chemotherapeutic efficacy and improve prognosis for individuals who present with glioblastoma.

Cellular immunotherapy for pediatric solid tumors

Substantial progress has been made in the treatment of pediatric solid tumors over the past 4 decades. However, children with metastatic and or recurrent disease continue to do poorly despite the aggressive multi-modality conventional therapies. The increasing understanding of the tumor biology and the interaction between the tumor and the immune system over the recent years have led to the development of novel immune-based therapies as alternative options for some of these high-risk malignancies. The safety and anti-tumor efficacy of various tumor vaccines and tumor-antigen specific immune cells are currently being investigated for various solid tumors. In early clinical trials, most of these cellular therapies have been well tolerated and have shown promising clinical responses. Although substantial work is being done in this field, the available knowledge for pediatric tumors remains limited. We review the contemporary early phase cell-based immunotherapy efforts for pediatric solid tumors and discuss the rationale and the challenges thereof.

Glutamate transporters in the biology of malignant gliomas

Malignant gliomas are relentless tumors that offer a dismal clinical prognosis. They develop many biological advantages that allow them to grow and survive in the unique environment of the brain. The glutamate transporters system x c (-) and excitatory amino acid transporters (EAAT) are emerging as key players in the biology and malignancy of these tumors. Gliomas manipulate glutamate transporter expression and function to alter glutamate homeostasis in the brain, which supports their own growth, invasion, and survival. As a consequence, malignant cells are able to quickly destroy and invade surrounding normal brain. Recent findings are painting a larger picture of these transporters in glioma biology, and as such are providing opportunities for clinical intervention for patients. This review will detail the current understanding of glutamate transporters in the biology of malignant gliomas and highlight some of the unique aspects of these tumors that make them so devastating and difficult to treat.

Glioma residual or recurrence versus radiation necrosis: accuracy of pentavalent technetium-99m-dimercaptosuccinic acid [Tc-99m (V) DMSA] brain SPECT compared to proton magnetic resonance spectroscopy (1H-MRS): initial results

We compared pentavalent technetium-99m dimercaptosuccinic acid (Tc-99m (V) DMSA) brain single photon emission computed tomography (SPECT) and proton magnetic resonance spectroscopy ((1)H-MRS) for the detection of residual or recurrent gliomas after surgery and radiotherapy. A total of 24 glioma patients, previously operated upon and treated with radiotherapy, were studied. SPECT was acquired 2-3 h post-administration of 555-740 MBq of Tc-99m (V) DMSA. Lesion to normal (L/N) delayed uptake ratio was calculated as: mean counts of tumor ROI (L)/mean counts of normal mirror symmetric ROI (N). (1)H-MRS was performed using a 1.5-T scanner equipped with a spectroscopy package. SPECT and (1)H-MRS results were compared with pathology or follow-up neuroimaging studies. SPECT and (1)H-MRS showed concordant residue or recurrence in 9/24 (37.5%) patients. Both were true negative in 6/24 (25%) patients. SPECT and (1)H-MRS disagreed in 9 recurrences [7/9 (77.8%) and 2/9 (22.2%) were true positive by SPECT and (1)H-MRS, respectively]. Sensitivity of SPECT and (1)H-MRS in detecting recurrence was 88.8 and 61.1% with accuracies of 91.6 and 70.8%, respectively. A positive association between the delayed L/N ratio and tumor grade was found; the higher the grade, the higher is the L/N ratio (r = 0.62, P = 0.001). Tc-99m (V) DMSA brain SPECT is more accurate compared to (1)H-MRS for the detection of tumor residual tissues or recurrence in glioma patients with previous radiotherapy. It allows early and non-invasive differentiation of residual tumor or recurrence from irradiation necrosis.

Identification of chemosensitivity nodes for vinblastine through small interfering RNA high-throughput screens

Discovering chemosensitivity pathways or nodes is an attractive strategy for formulating new drug combinations for cancer. Microtubules are among the most successful anticancer drug targets. Therefore, we implemented a small interfering RNA (siRNA) synthetic lethal screen targeting 5520 unique druggable genes to identify novel chemosensitivity nodes for vinblastine, a microtubule-destabilizing agent used clinically. We transiently transfected human glioblastoma cells with siRNAs for 48 h and then treated cells with a sublethal concentration of vinblastine. Forty-eight hours later, we analyzed cell viability and, using a series of statistical methods, identified 65 gene products that, when suppressed, sensitized glioblastoma cells to vinblastine. After completion of the secondary assays, we focused on one siRNA, B-cell lymphoma extra large (BCL-xL), because of its role in the intrinsic apoptosis signaling pathway as well as the availability of pharmacological inhibitors. We found that nontoxic concentrations of 4-[4-[[2-(4-chlorophenyl)-5,5-dimethylcyclohexen-1-yl]methyl]piperazin-1-yl]-N-[4-[[(2R)-4-morpholin-4-yl-1-phenylsulfanylbutan-2-yl]amino]-3-(trifluoromethylsulfonyl)phenyl]sulfonylbenzamide (ABT-263), an inhibitor of the BCL-2 family members (BCL-2, BCL-xL, and BCL-w), sensitized glioblastoma and non-small-cell lung cancer cells to vinblastine and induced apoptosis through the intrinsic cell death pathway. These results illustrate the usefulness of unbiased siRNA screens as a method for identifying potential novel anticancer therapeutic combinations.

Outcome of patients with recurrent medulloblastoma or central nervous system germinoma treated with low dose continuous intravenous etoposide along with dose-intensive chemotherapy followed by autologous hematopoietic stem cell rescue

BACKGROUND

Adults and children with recurrent malignant central nervous system (CNS) tumors have a poor prognosis despite high dose chemotherapy with a conventional stem cell rescue regimen. In this study we evaluated the results of low dose, continuous infusion etoposide over 21 days added to a conventional high-dose regimen of carboplatin and thiotepa in eight patients with relapsed pediatric CNS tumors.

PROCEDURE

Patients with high risk CNS tumors were treated with etoposide 25 mg/m(2)/day by continuous intravenous (IV) infusion from day -22 to day -2, carboplatin 667 mg/m(2)/dose IV (or area under the curve = 9 mg/ml/min according to the Calvert formula on days -8, -7, and -6, and thiotepa 300 mg/m(2)/dose IV on days -5, -4, and -3, followed by autologous hematopoietic stem cell rescue on day 0.

RESULTS

Eight adults and children, with a mean age of 12.9 years (age range 5.6-27.8 years), with relapsed primary CNS tumors (metastatic medulloblastoma (7), germinoma (1)), were enrolled. The mean survival post-transplant was 4.8+ years, (range 8-160+ months). The 2- and 5-year overall survival rates were 75% and 50% respectively. None of the survivors required additional salvage irradiation.

CONCLUSION

The strategy of low dose chronic exposure to a topoisomerase inhibitor along with ablative carboplatin and thiotepa with stem cell rescue showed promising survival outcomes in these relapsed patients. This treatment strategy deserves further evaluation in a larger group of high-risk or relapsed primary CNS tumors.

Myc down-regulation affects cyclin D1/cdk4 activity and induces apoptosis via Smac/Diablo pathway in an astrocytoma cell line

OBJECTIVES

We investigated the antiproliferative effect of Myc down-regulation via cell proliferation inhibition, cell cycle perturbation and apoptosis in two human astrocytoma models (T98G and ADF) steadily expressing an inducible c-myc Anti-sense RNA.

MATERIALS AND METHODS

Cell growth experiments were performed using the trypan blue dye exclusion test and cell cycle analysis was evaluated by flow cytometry. Cell cycle molecules were detected by Western blot analysis, co-immunoprecipitation and reverse transcription-polymerase chain reaction assays.

RESULTS

We showed that Myc down-regulation in astrocytoma cells led to G1 accumulation and an inhibition of cell proliferation characterized by S phase delay. Co-immunoprecipitation experiments detected formation of inactive cyclin D1/cdk4 complexes as evaluated by presence of an active unphosphorylated form of retinoblastoma protein, the best characterized target substrate for cyclin D1/cdk4 complex, in ADF pINDc-myc anti-sense 7 cells. We also found that either p57Kip2 "apice" or p27Kip1 "apice" inhibitors bound to cyclin D1/cdk4 complex, thus, suggesting that they cooperated to inhibit the activity of cyclin D1/cdk4. Moreover, c-Myc down-regulation led to activation of the apoptotic mitochondrial pathway, characterized by release of cytochrome c and Smac/Diablo proteins and by reduction of c-IAP levels through activation of proteasome-mediated protein degradation system.

CONCLUSIONS

Our results suggest that c-Myc could be considered as a good target for the study of new approaches in anticancer astrocytoma treatment.

Bcl-2 Up-Regulation and P-p53 Down-Regulation Account for the Low Sensitivity of Murine L929 Fibrosarcoma Cells to Oridonin-Induced Apoptosis

Drug resistance has been a major limitation to chemotherapy. There are many mechanisms that contribute to such resistance. In our study, we subcloned oridonin-sensitive and low sensitive L929 cells and both types of cells grew at almost the same growth rate. The acquired low sensitivity to oridonin-induced apoptosis was associated with Bcl-2 up-regulation and down-regulation of p53 phosphorylation. The p38 inhibitor SB203580 decreased Bcl-2 expression in the low sensitive L929 cells and made the cells more sensitive to oridonin. Moreover, a higher dose of oridonin promoted p53 phosphorylation, increased Bax expression and subsequently induced death of low sensitive L929 cells, however, it had no effect on Bcl-2 expression. The increased Bcl-2/Bax ratio in oridonin low sensitive L929 cells did not inhibit caspase-9 or -3 activation, but suppressed the cleavage of poly (ADP-ribose) polymerase (PARP), indicating the existence of caspase-9 or -3 independent PARP activation. These results indicated that in L929 cells, there was a relationship among the low sensitivity to oridonin, down-regulation of p53 phosphorylation and Bcl-2 up-regulation.

Differential responsiveness among "high risk" pediatric brain tumors in a pilot study of dose-intensive induction chemotherapy

BACKGROUND

These factors have been predictive for progressive disease on therapy (PDOT) among pediatric brain tumors: >1.5 cm(2) unresectable tumor, glioblastoma, supratentorial primitive neuroectodermal tumor, and metastatic medulloblastoma (MBL). This pilot study sought to correlate cytoreductive response with progression free survival.

PROCEDURES

Four courses of cisplatinum, cyclophosphamide, etoposide, and vincristine preceded hyperfractionated radiotherapy (RT). Maintenance chemotherapy consisted of eight cycles of carboplatin, etoposide, and vincristine. Biopsy specimens were immunohistochemically studied for labeling index, hypoxia, and multidrug resistance proteins.

RESULTS

Twenty newly diagnosed patients [nine primitive neuroectodermal tumors/MBL, one choroid plexus carcinoma, eight malignant gliomas, and two anaplastic ependymomas] were treated. Ten patients, who required neuraxis irradiation, constituted the "PNET" group. These demonstrated five complete and one partial response (PR), with an estimated median progression free survival of 44 months and median survival in excess of 53 months. Patients treated with involved field irradiation were designated the "Glioma" group. Induction chemotherapy produced partial and minor responses (MRs) among 5/10. Their estimated median progression free survival was 6.9 months (P = 0.035 relative to the PNET) with a median survival of 10.7 months (P = 0.04). Age, labeling index, the presence of hypoxia, and Pgp/MDR1 expression failed to discriminate between the two groups.

CONCLUSIONS

This induction regimen produced a cytoreductive response in 6/10 and achieved a significant improvement in progression free survival among 7/10 in the PNET group. Unfortunately, responses among Glioma patients did not translate into durable control. Expression of the biologic factors was similar between both groups and did not correlate with diagnosis or response.

Therapy of glioblastoma multiforme improved by the antimutagenic chloroquine

Object

Therapy of malignant tumors is frequently curtailed by the emergence of chemoresistant cell clones. Experimentally, the authors have demonstrated that chemotherapy for glioma in rats is markedly improved by the administration of the antimutagenic quinacrine. They studied the effects of chloroquine, an antimutagenic with an optimal pharmacological profile for human use, as adjuvant for the treatment of patients with glioblastoma multiforme (GBM).

Methods

In a prospective controlled randomized trial, 18 patients with GBM underwent standard treatment with surgery, chemotherapy, and radiotherapy; nine received an additional 150-mg dose of chloroquine daily starting 1 day after surgery and continued through the observation period. Nine matched patients were included as controls. Neuroimaging studies and clinical response were periodically compared. The follow-up period ranged from 24 to 50 months.

Survival time was defined as the main outcome measure. Survival was significantly longer in chloroquine-treated patients than in controls (33 ± 5 and 11 ± 2 months, respectively [p < 0.0002]). At the end of the observation period, four patients (46%) treated with chloroquine were alive, two had evidence of tumor remission after 2 years; in another two, tumor recurrence developed after 2 and 4 years of remission, respectively. No control patient survived more than 22 months after surgery.

Conclusions

Chronic administration of chloroquine greatly enhanced the response of GBM to antineoplastic treatment. Because the cytotoxicity of chloroquine on malignant cells is negligible, these favorable results appear mediated by its strong antimutagenic effect that precludes the appearance of resistant clones during radiotherapy and chemotherapy.

The molecular genetics of therapeutic resistance in malignant astrocytomas

The adverse prognosis associated with malignant astrocytomas (MA) is due in part to the development of resistance by the tumor to chemo- and radiotherapy-induced cytotoxic damage. The mechanisms of resistance are poorly understood but function at the level of the endothelial cell, the blood-brain barrier and the neoplastic cell itself. The classic examples of drug resistance proteins, such as the p-glycoprotein/multidrug resistance protein 1, have been identified within MA biopsy specimens. However, it is questionable to what degree, if at all, these proteins contribute directly to the evolution and prognosis of the MA. Surprisingly, there are specific genes, not traditionally associated with resistance, which appear increasingly relevant to both tumor progression and insensitivity to cytotoxic damage. These genes are involved in cell cycle regulation, and include the retinoblastoma susceptibility gene (Rb), the tumor suppressor gene p53, as well as those encoding the cyclins, their kinases and inhibitors. The interaction between the products of these genes and intratumoral environmental factors appears to involve a dynamic and prognostically adverse selection process. It is from this perspective that the mechanism(s) of hypoxic-ischaemic selection for resistance and its therapeutic repercussions will be analyzed.

Effect of expression of P-glycoprotein on technetium-99m methoxyisobutylisonitrile single photon emission computed tomography of brain tumors

The expression of P-glycoprotein was investigated immunohistochemically in 26 brain tumor tissues and compared with the findings of technetium-99m methoxyisobutylisonitrile single photon emission computed tomography (99mTc-MIBI SPECT) to clarify the effect of P-glycoprotein on the diagnostic accuracy. P-glycoprotein labeling index of both tumor cells and vascular endothelial cells showed no clear relationship with the findings of 99mTc-MIBI SPECT imaging. Expression of P-glycoprotein has no effect on the diagnostic accuracy of 99mTc-MIBI SPECT.

Immunohistochemical markers for prognosis of cerebral glioblastomas

Glioblastoma is the commonest neuroectodermal tumor and the most malignant in the range of cerebral astrocytic gliomas. The prognostic utility of various biological markers for glioblastomas has been broadly tested but the results obtained are regarded as controversial. In the present study, 302 glioblastoma specimens were studied to evaluate a possible association between clinical outcome and expression of some immunohistochemical variables. Furthermore, tumors examined were subdivided on the three cytological subsets--small-cell (SGB), pleomorphic-cell (PGB) and gemistocytic (GGB). Immunohistochemical variables differed between various subsets: the number of p53-positive tumors was found to be prevailed among the PGB, whereas the number of tumors with EGFR and mdm2 positivity was significantly greater in SGB. GGB contained significantly lowest mean proliferating cell nuclear antigen (PCNA) labeling index (LI), greater number of p21ras positive cases, and higher mean apoptotic index (AI). Survival time in patients with SGB, EGFR and mdm2-positivity and PCNA LI >40% was found to be significantly shorter, whereas presence of p21ras and AI >0.5% were associated with prolonged survival. Multivariate analysis revealed that survival time is associated with SGB, EGFR-positivity, and AI (p = 0.0023, p = 0.0035 and p = 0.0029 respectively). We conclude that although some immunohistochemical variables were found to be significant for glioblastoma outcome, they appear to be closely related to biology of single cytological subsets. Furthermore, these variables exhibited no prognostic value when they were analyzed within each cytological subset separately. Therefore, the glioblastoma subdivision on three cytological subsets proposed by us is carrying some element of rationality but, undoubtedly, requires further prospective studies.

Molecular and functional MDR1-Pgp and MRPs expression in human glioblastoma multiforme cell lines

The aim of our study was to investigate the functional expression of P-glycoprotein (Pgp) and multidrug resistance-associated proteins (MRPs) in 2 distinct glioma cells (GL15 and 8MG) from patients with glioblastoma multiforme. MDR1 gene and Pgp expression was not detected in either cell line by RT-PCR and Western blotting, respectively. In contrast, MRP1 was detected at both mRNA and protein level in both cell lines, with a higher expression in the 8MG cells that occur predominantly at the cell membrane. Three other MRPs (MRP3, MRP4 and MRP5) were detected by RT-PCR in both cell lines, whereas MRP2 was not expressed. In addition, MRP3 protein was also detected by immunocytochemistry in both GL15 and 8MG cell lines. Indomethacin and probenecid, 2 modulators of MRPs activity, increased the accumulation of vincristine and etoposide, 2 substrates of MRPs, by both cell lines. These modulators also decreased the efflux of vincristine from both cell lines with a more pronounced effect in 8MG cells. In conclusion, our results show functional expression of MRPs leading to a decrease in the intracellular vincristine and etoposide concentrations in human glioblastoma cell lines. Furthermore, our results that exhibit protein expression of MRP1 and MRP3 and gene expression of MRP4 and MRP5 in these 2 glioblastoma cell lines suggest new mechanisms that could lead to a MDR phenotype of tumour cells in patients with glioblastoma multiforme.

Quinacrine enhances carmustine therapy of experimental rat glioma

OBJECTIVE

The high rate of mutagenesis in malignant cells has been considered to be a primary factor in the appearance of chemotherapy-resistant cell clones in glioblastomas. Quinacrine binds strongly to deoxyribonucleic acid, preventing mutagenesis. We investigated whether quinacrine could improve carmustine therapy in C6 cell cultures and in C6 malignant gliomas implanted subcutaneously into Wistar rats.

METHODS

A potential chemopreventive effect of quinacrine on acquired resistance to carmustine therapy was studied in vitro and in vivo. Deoxyribonucleic acid damage was measured in cultured C6 cells by using the micronucleus test. Wistar rats with subcutaneously implanted C6 gliomas were treated with carmustine, quinacrine, or carmustine plus quinacrine, using pharmacological schemes similar to those used for human patients.

RESULTS

The addition of quinacrine to cultured C6 cells did not modify carmustine-induced cytotoxicity; however, the deoxyribonucleic acid damage in surviving cells was minor, as indicated by the frequency of micronucleated cells. The surviving cells continued to be susceptible to a second exposure to carmustine, in contrast to non-quinacrine-treated control cells, which developed resistance to carmustine in a subsequent exposure (P < 0.05). The rate of tumor remission was higher for glioma-bearing rats treated with quinacrine plus carmustine, compared with rats treated with carmustine alone (P < 0.01).

CONCLUSION

The addition of quinacrine to carmustine therapy increases the antineoplastic effect of the carmustine therapy. Our results suggest that chemical inhibition of mutagenesis in malignant glial cells during chemotherapy prevents the appearance of resistant clones.

Antitumor efficacy of SarCNU in a human glioma xenograft model expressing both MGMT and extraneuronal monoamine transporter

Treatment of malignant brain tumors with chloroethylnitrosoureas (CENUs) in addition to surgical resection and radiotherapy remains the foundation of glioma therapy. However, the clinical response to CENUs is at best modest. A novel analogue of nitrosoureas, 2-chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU), as compared to the standard CENU, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), has been demonstrated to have increased anticancer effects both in vitro and in vivo. Unfortunately, many human tumors have been known to be resistant to CENUs since they express DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). In order to assess whether SarCNU has an effect on MGMT positive tumors, we evaluated its antitumor efficacy using an MGMT positive human glioma (SF-767) nude mouse xenograft model. Since SF-767 has high MGMT levels, BCNU treatment (20 mg/kg, Q4D x 3 i.p.) alone did not result in a satisfactory anticancer effect (p > 0.05). As expected, O6-benzylguanine (O6-BG) (100 mg/kg), which was given prior to BCNU treatment, by depleting MGMT activity, significantly enhanced BCNU antitumor efficacy (p < 0.001). Moreover, SarCNU treatment (167 mg/kg, Q4D x 3 i.p.) alone had a better antitumor effect than O6-BG plus BCNU treatment (F = 51.7, p = 0.0004). However, in this xenograft model, O6-BG did not significantly enhance the anticancer efficacy of SarCNU (F = 0.8, p = 0.411). The SF-767 human glioma xenograft is positive for extraneuronal monoamine transporter EMT (EMT) as determined by reverse-transcription polymerase chain reaction (RT-PCR). Our present results suggest that SarCNU is also effective for MGMT positive tumor if they exhibit EMT.

Intrinsic expression of drug resistance-associated factors in meningiomas

Meningiomas, commonly benign tumors, rarely display aggressive behavior by recurrences and invasion. In addition to surgery, irradiation is beneficial for recurrent, atypical, and malignant meningiomas. The role of chemotherapy, however, remains controversial, although there is evidence that meningiomas respond well to adjuvant chemotherapy. A major obstacle in chemotherapy remains drug resistance with reduced cellular drug accumulation through membrane efflux pumps, drug detoxification, and alterations in drug target specificity. In 84 classic, atypical, and malignant meningiomas, the immunohistochemical expression profile of P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), metallothionein, and topoisomerase IIalpha were studied. All types of meningiomas showed constant expression of P-gp, LRP, MRP, and topoisomerase IIalpha; metallothionein was found in 67% of the tumors, especially in atypical and malignant meningiomas. Furthermore, metallothionein. P-gp, LRP, and topoisomerase IIalpha were strongly expressed by normal and neoplastic vessels, which may confer to impaired penetration of therapeutic agents through the blood-brain and blood-tumor barrier. Neither recurrent nor previously irradiated meningiomas revealed any significant difference to primary tumors. These intrinsic drug resistances indicate that successful chemotherapy may require additional inhibition of these factors to be a promising approach in the management of meningiomas.

Anticancer drug resistance in primary human brain tumors

The difficult clinical situation still associated with most types of primary human brain tumors has fostered significant interest in defining novel therapeutic modalities for this heterogeneous group of neoplasms. Beginning in the 1980s chemotherapy has been incorporated into the treatment protocol of a number of intractable brain tumors. However, it has predominantly failed to improve patient outcome. The unsatisfactory results with chemotherapeutic intervention have chiefly been attributed to tumor cell resistance. In recent years, there has been a literal explosion in our understanding about the mechanisms by which cancer cells become chemoresistant. During the course of their evolution (intrinsic resistance) or in response to chemotherapy (acquired resistance) these cells may follow a number of pathways of genetic alterations to possess a common (multidrug) or drug-specific (individual drug) resistant phenotype. Genomic aberrations, deregulation of membrane transporting proteins and cellular enzymes, and an altered susceptibility to commit to apoptosis are among the steps on the way that contribute to the genesis of chemotherapeutic treatment failure. Although, through the years we have come to yield information and inferences as to the roles that different molecular events may have in the resistance phenotype of cancer cells, the actual involvement of single genetic alterations in conferring drug resistance in primary brain tumors remains debatable. This uncertainty and, besides, the lack of proper drug resistance diagnostics, in a vicious circle, hinder the development of effective resistance-modulation strategies. Clinical non-responsiveness to chemotherapy remains a formidable obstacle to the successful treatment of brain tumors and one of the most serious problems to be solved in the therapy of these lesions. Future advances in the chemotherapeutic management of these neoplasms will come with an improved understanding of the significance and interrelationship of the multiple biological systems operative in promoting resistance to this treatment modality. The focus of this review is to summarize current knowledge concerning major drug resistance-related markers, to describe their functional interaction en route to chemoresistance, and to discuss their implication in rendering human brain tumor cells resistant to chemotherapy.

A phase II study of temozolomide vs. procarbazine in patients with glioblastoma multiforme at first relapse

A randomized, multicentre, open-label, phase II study compared temozolomide (TMZ), an oral second-generation alkylating agent, and procarbazine (PCB) in 225 patients with glioblastoma multiforme at first relapse. Primary objectives were to determine progression-free survival (PFS) at 6 months and safety for TMZ and PCB in adult patients who failed conventional treatment. Secondary objectives were to assess overall survival and health-related quality of life (HRQL). TMZ was given orally at 200 mg/m(2)/day or 150 mg/m(2)/day (prior chemotherapy) for 5 days, repeated every 28 days. PCB was given orally at 150 mg/m(2)/day or 125 mg/m(2)/day (prior chemotherapy) for 28 days, repeated every 56 days. HRQL was assessed using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30 [+3]) and the Brain Cancer Module 20 (BCM20). The 6-month PFS rate for patients who received TMZ was 21%, which met the protocol objective. The 6-month PFS rate for those who received PCB was 8% (P = 0.008, for the comparison). Overall PFS significantly improved with TMZ, with a median PFS of 12.4 weeks in the TMZ group and 8.32 weeks in the PCB group (P = 0.0063). The 6-month overall survival rate for TMZ patients was 60% vs. 44% for PCB patients (P = 0.019). Freedom from disease progression was associated with maintenance of HRQL, regardless of treatment received. TMZ had an acceptable safety profile; most adverse events were mild or moderate in severity.

Phase II trial of cystemustine, a new nitrosourea, as treatment of high-grade brain tumors in adults

This study included 39 patients (37 evaluable, of whom 30 patients with recurrent gliomas and 7 patients with gliomas untreated by radiotherapy); they were enrolled into a phase II trial using a new nitrosourea, cystemustine, administrated every 2 weeks at 60 mg/m2 as a 15 min-infusion. Pathology at inclusion was (WHO classification): 14 glioblastomas, 20 grade 3-4 astrocytomas and 3 grade 3 oligodendrogliomas. Four partial responses have been obtained, giving an overall response rate of 10.8%. Four additional patients had a partial response, which for various reasons was not confirmed 4 weeks later; 12 patients had a stable disease for at least 8 weeks, 15 patients had progressive disease. Of the 4 responses, 2 were with a grade 3 oligodendroglioma and 2 glioblastoma. Toxicity (WHO grading) was mainly hematological: leukopenia (16.2% grade 3-4), neutropenia (29.7% grade 3-4), thrombopenia (27% grade 3-4). No other toxicity greater than grade 2 was observed. In conclusion, cystemustine at 60 mg/m2 has moderate clinical activity in relapsing glioma. Our results warrant further investigation of this agent with an increased dose or modified scheme.

Prognostic value of immunoexpression of the chemoresistance-related proteins in ependymomas: an analysis of 76 cases

Intracranial ependymomas are the third most common primary brain tumor in children. A variety of chemotherapy protocols have been introduced for the treatment of ependymoma although overall these have not contributed to patients outcome. To our knowledge, data on the prognostic value of immunoexpression of the chemoresistance-related proteins (ChRPs) in ependymomas are absent. Seventy-six patients with intracranial ependymomas who received combined treatment were studied retrospectively. Tumor specimens were immunohistochemically examined with antibodies to metallothioneins (MT), glutathione S-transferase pi (GST pi) and P-glycoprotein (P-GP). The results demonstrated significant preponderance of expression of all the above-mentioned ChRPs for the low-grade tumors. The progression-free survival time was found to be significantly shorter for immunonegative tumors in both tumor grades. Multivariate analysis using a Cox hazard model revealed that recurrence-free survival time is significantly associated with tumor grade, and MT and P-GP expression. Risk of recurrence increased for the high-grade ependymomas (hazard ratio 2.85; P = 0.004), and decreased for the MT-positive tumors (hazard ratio -2.72; P = 0.005) and for the P-GP-positive tumors (hazard ratio -2.02; P = 0.02). The obtained results allow one to conclude that ChRPs expression is closely associated with low-grade ependymomas and immunohistochemical findings may be estimated as a predictor for local tumor progression.

The usefulness of Tc-99m MIBI for evaluating brain tumors: comparative study with Tl-201 and relation with P-glycoprotein

PURPOSE: This study was undertaken to determine the usefulness of Tc-99m methoxyisobutylisonitrile (MIBI) in brain tumors compared with TI-201 imaging. The authors evaluated the correlation between MIBI uptake and the presence of P-glycoprotein, and also the relation between MIBI uptake in response to combined radiotherapy and chemotherapy in glioblastoma. MATERIALS AND METHODS: Thirty-four brain tumors composed of 15 glioblastoma multiforme (GBM), 5 anaplastic astrocytomas, 5 low-grade astrocytomas, and 9 metastases were evaluated. Early and delayed images were obtained for MIBI and Tl-201 scintigraphy. P-glycoprotein status in all GBM, 2 anaplastic astrocytomas, 2 low-grade astrocytomas, and 2 metastases were evaluated immunohistochemically. Patients with GBM were divided into an effective and a noneffective group according to the change in tumor size. MIBI uptake indices were compared for these two groups. RESULTS: Both radiopharmaceuticals accumulated in all GBM and anaplastic astrocytomas. In low-grade astrocytomas, only one case showed tracer uptake. In metastasis, two cases showed high uptake on early images and marked washout on delayed images. Uptake ratio values (early uptake ratio and delayed uptake ratio) in all tumors were significantly higher in MIBI than in Tl-201. Immunohistochemical studies showed that the metastases were positive for P-glycoprotein but the GBM were not. In low-grade astrocytomas, a few cells were positively stained. In relation to the therapeutic outcome of GBM, both the early and delayed uptake ratios of MIBI were significantly greater in the noneffective group. CONCLUSIONS: Although diagnostic ability was comparable in MIBI and Tl-201, the imaging quality was better in MIBI. Both radiopharmaceuticals are useful in differentiating low-grade glioma from high-grade glioma. MIBI delayed imaging could also reflect the presence of P-glycoprotein. Intense MIBI uptake was also predictive of a poor clinical outcome in GBM.

Causes of drug resistance and novel therapeutic opportunities for the treatment of glioblastoma

Malignant gliomas are among the most lethal and intractable of human tumors and drug resistance is one of the major obstacles to their successful treatment. Recent advances in the molecular biology and genetics of human cancers provide a detailed understanding of cellular and molecular responses to chemotherapy and how drug resistance may develop. Several oncogenes and tumor suppressor genes have been shown to confer resistance to tumor cells and should, therefore, provide novel and defined targets for cancer treatment. In addition to overcoming cellular resistance, special efforts to increase drug delivery to glial tumors need to be pursued because of the relatively unique problem of the blood-brain barrier. Treatments aimed at these targets will likely benefit from combined therapies including surgery, traditional chemotherapy and targeted disruption of other physiological processes such as angiogenesis. Copyright 1999 Harcourt Publishers Ltd.

Expression of multidrug resistance protein gene in patients with glioma after chemotherapy

Two different ATP-binding membrane glycoproteins, the 170 kDa P-glycoprotein (P-gp) and the 190 kDa multidrug resistance protein (MRP), are involved in the acquisition of multidrug resistance phenotypes in cancer cells. Overexpression of P-gp is often observed in various human tumors when treated with anticancer agents. In this study, we asked whether MRP was overexpressed in human gliomas after cancer chemotherapy. We investigated expression of MRP and P-gp before and after chemotherapy in tumor samples from patients with glioma. MRP expression was observed in 16 (70%) of 23 untreated patients, and the proportion of MRP-positive cells in the whole cell population ranged from 3 to 32% in the 16 MRP-positive patients. P-gp-positive tumors were observed in 4 (18%) of 23 patients, and the proportional rates of P-gp-positive cells in the whole cell population ranged from 4 to 23%. The proportional rate of MRP-positive or P-gp-positive glioma cells increased after chemotherapy when compared with that before chemotherapy in all patients examined. We could observe no statistically significant correlation between expression of MRP or P-gp and tumor grade. These results suggest that MRP as well as P-gp may be involved in acquired or intrinsic drug resistance in human glioma.

Drug resistance of human glioblastoma cells conferred by a tumor-specific mutant epidermal growth factor receptor through modulation of Bcl-XL and caspase-3-like proteases

Alterations of the epidermal growth factor receptor (EGFR) gene occur frequently in human malignant gliomas. The most common of these is deletion of exons 2-7, resulting in truncation of the extracellular domain (DeltaEGFR or EGFRvIII), which occurs in a large fraction of de novo malignant gliomas (but not in progressive tumors or those lacking p53 function) and enhances tumorigenicity, in part by decreasing apoptosis through up-regulation of Bcl-XL. Here, we demonstrate that the DeltaEGFR concomitantly confers resistance to the chemotherapeutic drug cisplatin (CDDP) by suppression of CDDP-induced apoptosis. Expression of Bcl-XL was elevated in U87MG.DeltaEGFR cells prior to and during CDDP treatment, whereas it decreased considerably in CDDP-treated parental cells. CDDP-induced activation of caspase-3-like proteases was suppressed significantly in U87MG.DeltaEGFR cells. These responses were highly specific to constitutively kinase-active DeltaEGFR, because overexpression of kinase-deficient DeltaEGFR (DK) or wild-type EGFR had no such effects. Correspondingly, DeltaEGFR specific tyrosine kinase inhibitors reduced Bcl-XL expression and potentiated CDDP-induced apoptosis in U87MG.DeltaEGFR cells. Ectopic overexpression of Bcl-XL in parental U87MG cells also resulted in suppression of both caspase activation and apoptosis induced by CDDP. These results may have important clinical implications for the use of CDDP in the treatment of those malignant gliomas expressing DeltaEGFR.

Excision repair cross-complementing rodent repair deficiency gene 2 expression and chloroethylnitrosourea resistance in human glioma cell lines

OBJECTIVE

Nitrosoureas are the standard chemotherapeutic agents for malignant brain tumors. However, their anticancer effects are limited because many tumors are resistant to these agents. Nucleotide excision repair can repair bulky deoxyribonucleic acid adducts, including deoxyribonucleic acid damage induced by ultraviolet light and some chemotherapeutic agents, and may be implicated in nitrosoureas resistance. In this study, we compared excision repair cross-complementing rodent repair deficiency Gene 2 (ERCC2), an important component of the nucleotide excision repair system, with 1 ,3-bis-(2-chloroethyl)-1-nitrosourea or (2-chloroethyl)-3-sarcosinamide-1-nitrosourea resistance in human glioma cell lines.

METHODS

ERCC2 expression was evaluated by using established quantitative reverse-transcription polymerase chain reaction. 1,3-Bis-(2-chloroethyl)-1-nitrosourea and (2-chloroethyl)-3-sarcosinamide-1-nitrosourea cytotoxicity were determined by a modification of the sulforhodamine B colorimetric anticancer drug screening assay.

RESULTS

A significant correlation between ERCC2 expression and 1 ,3-bis-(2-chloroethyl)-1-nitrosourea or (2-chloroethyl)-3-sarcosinamide-1-nitrosourea cytotoxicity was determined (r=0.737, P=0.0226 and r=0.789, P=0.0113, respectively).

CONCLUSION

Our results suggest that nucleotide excision repair, specifically ERCC2, may play an important role in nitrosoureas drug resistance in human gliomas.

Drug resistance and apoptosis in ENU-induced rat brain tumors treated with anti-cancer drugs

To cast light on the mechanisms of drug-resistance, experimental brain tumors were immunohistochemically evaluated for expression of glutathione S-transferase (GST)-alpha, mu, pi, p-glycoprotein and apoptosis-related factors, such as bcl-2 and p53, as well as by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) method. Rat brain tumors induced by means of prenatal exposure to ethylnitrosourea (ENU) were treated with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) and/or vincristine. Tumors more than 2 mm in size were considered to be drug resistant. The expression of GST-mu was strongly positive in ACNU-treated brain tumors, while p-glycoprotein was overexpressed in vincristine-treated brain tumors. Neither p53 nor bcl-2 expression directly correlated with apoptosis identified by TUNEL method, but tumors lacking apoptotic cells always demonstrated the expression of either GST-mu or p-glycoprotein. These results indicate that tumors resistant to chemotherapy might not be susceptible to induction of apoptosis, and therefore that mechanisms of drug resistance are related to programmed cell death in brain tumors.

Effects of hypoxia on drug resistance phenotype and genotype in human glioma cell lines

Recurrent gliomas are most often treated by chemotherapy. However, these tumors typically acquire resistance to most drugs administered, and patients will usually die of recurrent tumor. Factors which may play a role include overexpression of putative multidrug resistance genes, such as the multidrug resistance gene 1 (MDR1), multidrug resistance associated protein gene (MRP), 06-alkylguanine, DNA alkyltransferase gene (06MT) and excision repair cross complementing gene 1 (ERCC1). Tumor hypoxia has also been shown to be associated with drug resistance in other soft tissue tumors. Since gliomas have regions of diminished oxygenation, and have clinical resistance to chemotherapy, the relationship between phenotypic resistance to chemotherapy after hypoxic exposure and expression of drug resistance genes was investigated in glioma cell lines (U373 MG, PFAT-MT). After a 24 hour exposure to hypoxia, drugs 1, 3-bis, 2-chloroethyl-1-nitrosurea (BCNU) and cis-diammine, dichloroplatinum II (CDDP) were administered, and cell survival was determined. Hypoxic exposure was associated with increased survival of the cell lines after administration of BCNU and CDDP, with resistance to BCNU 15 to 30-fold when compared to cells which did not undergo hypoxic exposure. Both tumor cell lines also showed some degree of resistance to CDDP, although not to the extent of BCNU (2 to 3-fold increased resistance). The expression of the drug resistance genes was found to be unchanged when comparing cells which had undergone hypoxic exposure and those which had not. Thus, hypoxic exposure is associated with substantial drug resistance in brain tumor cell lines. The lack of correlation between the induced phenotype and known drug resistance genes suggests other mechanisms may be acting in these tumors in hypoxic conditions.

Genomic copy number changes of DNA repair genes ERCC1 and ERCC2 in human gliomas

Abnormalities of the genomic region of chromosome 19q13.2-13.4 are a common occurrence in brain malignancies and contain a possible tumor suppressor gene involved in gliomas. Since abnormalities of DNA repair are associated with malignancy, we assessed DNA status of the nucleotide excision repair genes located in this area, viz. ERCC1 and ERCC2. Radiodensitometry was used to assess gene copy number in samples obtained from brain tumor specimens from 24 patients. Nine tumors were of lower grade histology (3 pilocytic astrocytomas, 2 gangliogliomas, 4 astrocytomas); 15 tumors were pathologically higher grade (4 anaplastic astrocytomas, 11 glioblastomas). Tumor samples were obtained prior to radiation or chemotherapy. Abnormalities of gene copy number of ERCC1 and ERCC2 were observed in 11/24 specimens (46%). Whereas increased and decreased copy numbers were observed for ERCC1, only decreases in copy number of ERCC2 were seen. Three tumors (all lower grade) showed concurrent allelic loss of ERCC1 and ERCC2. Abnormalities of copy number for these genes were not associated with response to subsequent therapy nor survival. However, allelic loss of ERCC2 was associated with younger age at diagnosis when compared to those specimens which did not show loss. There were no significant differences between lower grade and higher grade tumors with respect to these investigations. Abnormalities in copy number of ERCC1 and ERCC2 are common in glial tumors. Further study of this genomic region is necessary to define the importance of these observations in tumor pathophysiology and treatment.