Rat Brain Tumor Research Articles

Different effects of K Ca and K ATP agonists on brain tumor permeability between syngeneic and allogeneic rat models

The blood–brain tumor barrier (BTB) significantly limits delivery of effective concentrations of chemotherapeutic drugs to brain tumors. Previous studies suggest that BTB permeability may be modulated via alteration in the activity of potassium channels. In this study, we studied the relationship of BTB permeability increase mediated by potassium channel agonists to channel expression in two rat brain tumor models. Intravenous infusion of KCO912 (K ATP agonist), minoxidil sulfate (K ATP agonist) or NS1619 (K Ca agonist) increased tumor permeability more in the 9L allogeneic brain tumor model than in the syngeneic brain tumor model. Consistently, expression of both K ATP and K Ca channels in 9L tumors was increased to a significantly greater extent in Wistar rats (allogeneic) as compared to Fischer rats (syngeneic). Furthermore, as a preliminary effort to understand clinical implication of potassium channels in brain tumor treatment, we determined the expression of K ATP in surgical specimens. K ATP mRNA was detected in glioblastoma multiforme (GBM) from nineteen patients examined, with a wide range of expression levels. Interestingly, in paired GBM tissues from seven patients before and after vaccination therapy, increased levels of K ATP were detected in five patients after vaccination that had positive response to chemotherapy after vaccination. The present study indicates that the effects of potassium channel agonists on BTB permeability are different between syngeneic and allogeneic models which have different expression levels of potassium channels. The expression of potassium channels in brain tumors is variable, which may be associated with different tumor permeability to therapeutic agents among patients.

188Re-loaded lipid nanocapsules as a promising radiopharmaceutical carrier for internal radiotherapy of malignant gliomas

Lipid nanocapsules (LNC) entrapping lipophilic complexes of (188)Re ((188)Re(S(3)CPh)(2)(S(2)CPh) [(188)Re-SSS]) were investigated as a novel radiopharmaceutical carrier for internal radiation therapy of malignant gliomas. The present study was designed to evaluate the efficacy of intra-cerebral administration of (188)Re-SSS LNC by means of convection-enhanced delivery (CED) on a 9L rat brain tumour model. Female Fischer rats with 9L glioma were treated with a single injection of (188)Re-SSS LNC by CED 6 days after cell implantation. Rats were put into random groups according to the dose infused: 12, 10, 8 and 3 Gy in comparison with blank LNC, perrhenate solution (4 Gy) and non-treated animals. The radionuclide brain retention level was evaluated by measuring (188)Re elimination in faeces and urine over 72 h after the CED injection. The therapeutic effect of (188)Re-SSS LNC was assessed based on animal survival. CED of (188)Re perrhenate solution resulted in rapid drug clearance with a brain T (1/2) of 7h. In contrast, when administered in LNC, (188)Re tissue retention was greatly prolonged, with only 10% of the injected dose being eliminated at 72 h. Rat median survival was significantly improved for the group treated with 8 Gy (188)Re-SSS LNC compared to the control group and blank LNC-treated animals. The increase in the median survival time was about 80% compared to the control group; 33% of the animals were long-term survivors. The dose of 8 Gy proved to be a very effective dose, between toxic (10-12 Gy) and ineffective (3-4 Gy) doses. These findings show that CED of (188)Re-loaded LNC is a safe and potent anti-tumour system for treating malignant gliomas. Our data are the first to show the in vivo efficacy of (188)Re internal radiotherapy for the treatment of brain malignancy.

Lack of a co‐promotion effect of 60 Hz rotating magnetic fields on N‐ethyl‐N‐nitrosourea induced neurogenic tumors in F344 rats

The present study was conducted to investigate the possible effect of 60 Hz magnetic fields as promoters of brain tumors initiated transplacentally by ethylnitrosourea (ENU) in F344 rats. One hundred twenty mated animals were divided into six different groups and exposed in utero on day 18 of gestation to a single intravenous dose of either Saline (vehicle control, Group I), or ENU 10 mg/kg (Groups II-VI). In the present study, a total of 480 offspring was used. The offspring in group II were given no further treatment while the offspring in Groups III-VI were exposed to four different intensities of magnetic fields. Animals received exposure to 60 Hz magnetic field at field strengths of 0 Tesla (sham control, T1, Group III), 5 muT (T2, Group IV), 83.3 muT (T3, Group V), or 500 muT (T4, Group VI), for 21 h/day from the age of 4 weeks to the age of 32 or 42 weeks. At histopathological examination, tumors of the nervous system were seen in all the ENU-treated groups. The tumor incidence of the ENU group at 32nd and 42nd week necropsy was higher than that of the vehicle control group. The incidence of glial tumors at 42nd week necropsy was higher than the 32nd week necropsy. However, there were no differences in the tumor incidence between the sham control (T1) and ENU + magnetic field exposure groups (T2-T4). In conclusion, there was no evidence that exposure of offspring to 60 Hz at magnetic field strengths up to 500 muT to the age of 32 or 42 weeks promoted ENU-initiated brain tumors in rats.

A novel rat model for glioblastoma multiforme using a bioluminescent F98 cell line

In experimental neuro-oncology there remains a need for animal models that can be used to assess the efficacy of new and innovative treatment methodologies for glioblastoma multiforme (GBM). Rat models have remained the mainstay of neuro-oncology research for over 30 years; however, despite extensive experimentation, there is no one rat model that truly reflects the features of human tumours. We have developed a novel rat brain tumour model that closely resembles human GBM in biological behaviour and that utilizes bioluminescence imaging (BLI) to follow day-to-day in vivo progress of the tumour. F98 glioma cells were transfected with the firefly luciferase gene and injected orthotopically into the brains of 24 rats. Weekly BLI after subcutaneous injection of luciferin allowed for in vivo monitoring of the progress of the brain tumours. Euthanasia and histological analysis of the rodent brains at varying stages post-implantation, allowed for statistically significant correlation between tumour size and luminescence ( p = 0.002). The utility of this model is readily apparent, allowing us a way of examining the effects of new and novel therapeutics in these rats.

Imaging of metals and metal-containing species in biological tissues and on gels by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS): A new analytical strategy for applications in life sciences

Abstract Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has become established as a very efficient and sensitive trace, ultratrace, and surface analytical technique in the life sciences. We have developed a new analytical imaging technique using LA-ICP-MS to study element distribution in biological tissues. Nowadays, LA imaging ICP-MS using double-focusing sector field (LA-ICP-SFMS) or quadrupole-based mass spectrometers (LA-ICP-QMS) can be applied as an exciting tool providing new information on the pathophysiology, pharmacology, and toxicology of elements of interest in biological systems. The quantitative determination of elements (e.g., Cu, Fe, Zn, Se, and others) in biological tissues is of growing interest especially in brain research (e.g., for studying neurodegenerative diseases such as Alzheimer's or Parkinson's disease). LA-ICP-SFMS was employed to produce images of detailed regionally specific element distributions in thin tissue sections of different sizes (such as control human or rat brain tissues or tumor regions). In addition, imaging MS using LA-ICP-QMS was applied to study the uptake and transport of nutrient and toxic elements in plant tissues. Besides the quantitative imaging of essential and toxic elements in tissues, powerful analytical techniques are also required for the determination and characterization of phosphoproteins and metal-containing proteins within a large pool of proteins, after electrophoretic separation (e.g., blue native, BN and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SDS-PAGE) into 1D and 2D gels. LA-ICP-MS was used to detect metalloproteins in protein bands of 1D gels or protein spots separated after 2D gel electrophoresis (2D-GE). In addition to elemental determination by LA-ICP-MS, matrix-assisted laser desorption/ionization (MALDI)-MS was employed to identify metal-containing proteins. Recent progress will be discussed in applying LA-ICP-MS in the life sciences, including the imaging of thin slices of tissue and applications in proteome analysis in combination with MALDI-MS to investigate phosphoproteins and metal-containing proteins.

Imaging of essential and toxic elements in biological tissues by LA-ICP-MS

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using double-focusing sector field (LA-ICP-SFMS) or quadrupole-based mass spectrometers (LA-ICP-QMS) was employed as powerful imaging (mapping) techniques to produce images of detailed regionally specific element distributions in thin tissue sections of different sizes such as control rat brain tissues or tumor regions to study tumor growing. LA-ICP-QMS was employed to investigate the uptake and the transport of nutrient elements in plant tissues or imaging of metals in proteins separated by native 2D BN-PAGE.

Comparative imaging of P, S, Fe, Cu, Zn and C in thin sections of rat brain tumor as well as control tissues by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of selected elements (P, S, Fe, Cu, Zn and C) in thin sections of rat brain samples (thickness 20 μm). The sample surface was scanned (raster area ~ 2 cm 2) with a focused laser beam (wavelength 266 nm, diameter of laser crater 50 μm, and irradiance 1 × 10 9 W cm − 2 ). The laser ablation system was coupled to a double-focusing sector field. The possibility was evaluated of using carbon (via measurement of 13C +) as an internal standard element for imaging element distribution as part of this method. The LA-ICP-MS images obtained for P, S, Fe Cu and Zn were quantified using synthetically prepared matrix-matched laboratory standards. Depending on the sample analyzed, concentrations of Cu and Zn in the control tissue were found to be in the range of 8–10 μg g − 1 and 10–12 μg g − 1 , while in the tumor tissue these concentrations were in the range of 12–15 μg g − 1 and 15–17 μg g − 1 , respectively. The measurements of P, S and Fe distribution revealed the depletion of these elements in tumor tissue. In all the samples, the shape of the tumor could be clearly distinguished from the surrounding healthy tissue by the depletion in carbon. Additional experiments were performed in order to study the influence of the water content of the analyzed tissue on the intensity signal of the analyte. The results of these measurements show the linear correlation ( R 2 = 0.9604) between the intensity of analyte and amount of water in the sample. The growth of a brain tumor was thus studied for the first time by imaging mass spectrometry.

Unique patterns of diffusion directionality in rat brain tumors revealed by high‐resolution diffusion tensor MRI

Diffusion tensor imaging (DTI) is a new technique that uses the microscopic motion of water molecules to probe tissue 3D microstructures. In this study, high-resolution DTI was performed on rats bearing intracranial 9L gliosarcoma, F98 glioma, and human glioblastoma. It was found that the tumors consisted of central zones with low diffusion anisotropy and peripheral structures (rim) with high diffusion anisotropy. In the rims, water diffusion directionality formed a circular pattern for the 9L and F98 tumors, and a radial pattern for the human glioblastoma xenografts. These well-organized diffusion patterns appeared at an early stage postimplantation and continued to exist with tumor growth in all three models. High-resolution ex vivo imaging and histology confirmed the in vivo findings. These distinct patterns, undetectable with conventional MRI, may reflect tumor organization and growth patterns at the cellular level.

99mTc‐MIBI imaging for prediction of therapeutic effects of second‐generation MDR1 inhibitors in malignant brain tumors

The aim of this study was to explore whether (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) is suitable to elucidate multidrug resistance and prediction of potentiation of antitumor agents by second-generation MDR1 inhibitors (PSC833, MS-209) in malignant brain tumors in rat. Malignant tumor cells (RG2 and C6 gliomas, Walker 256 carcinoma) were incubated with low dose vincristine (VCR) to induce multidrug resistance. MTT assay demonstrated a significant increase of surviving fractions in VCR-resistant sublines compared to those of drug-naive cells. Reverse transcriptase polymerase chain reaction revealed higher expression of MDR1 mRNA in VCR-resistant cells than drug-naive cells in each line. Volume distribution (V(d)) of (99m)Tc-MIBI was negatively correlated with MDR1 mRNA expression among drug-naive and VCR-resistant cells. MDR1 inhibitors decreased surviving fractions and increased V(d) of (99m)Tc-MIBI significantly in VCR-resistant sublines, whereas MDR1 mRNA expression was unchanged. These findings indicate that (99m)Tc-MIBI efflux was functionally suppressed by MDR1 inhibitors. Autoradiographic images of (99m)Tc-MIBI revealed higher uptake in drug-naive cells at basal ganglia compared with VCR-resistant cells at the opposite basal ganglia of rats. Oral administration of the second-generation MDR1 inhibitors significantly increased (99m)Tc-MIBI accumulation of both tumors. Therapeutic effects of VCR with or without the MDR1 inhibitors were also evaluated autoradiographically using (14)C-methyl-L-methionine ((14)C-Met) and MIB-5 index. (14)C-Met uptake and MIB-5 index of both tumors treated with VCR following the MDR1 inhibitor treatment significantly decreased compared with tumors treated with VCR alone. Analysis of (99m)Tc-MIBI accumulation is considered informative for detecting MDR1-mediated drug resistance and for monitoring the therapeutic effects of MDR1 inhibitors in malignant brain tumors.

Validation of Dynamic Contrast-Enhanced Magnetic Resonance Imaging-Derived Vascular Permeability Measurements Using Quantitative Autoradiography in the RG2 Rat Brain Tumor Model

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely used to evaluate tumor permeability, yet measurements have not been directly validated in brain tumors. Our purpose was to compare estimates of forward leakage Ktrans derived from DCE-MRI to the estimates K obtained using [14C]aminoisobutyric acid quantitative autoradiography ([14C]AIB OAR), an established method of evaluating blood-tumor barrier permeability. Both DCE-MRI and [14C]AIB OAR were performed in five rats 9 to 11 days following tumor implantation. Ktrans in the tumor was estimated from DCE-MRI using the threeparameter general kinetic model and a measured vascular input function. Ki was estimated from OAR data using regions of interest (ROI) closely corresponding to those used to estimate Ktrans. Ktrans and Ki correlated with each other for two independent sets of central tumor ROI (R = 0.905, P = .035; R = 0.933, P = .021). In an additional six rats, Ktrans was estimated on two occasions to show reproducibility (intraclass coefficient = 0.9993; coefficient of variance = 6.07%). In vivo blood-tumor permeability parameters derived from DCE-MRI are reproducible and correlate with the gold standard for quantifying blood tumor barrier permeability, [14C]AIB OAR.

Spheres Isolated from 9L Gliosarcoma Rat Cell Line Possess Chemoresistant and Aggressive Cancer Stem‐Like Cells

The rat 9L gliosarcoma is a widely used syngeneic rat brain tumor model that closely simulates glioblastoma multiforme when implanted in vivo. In this study, we sought to isolate and characterize a subgroup of cancer stem-like cells (CSLCs) from the 9L gliosarcoma cell line, which may represent the tumor-initiating subpopulation of cells. We demonstrate that these CSLCs form clonal-derived spheres in media devoid of serum supplemented with the mitogens epidermal growth factor and basic fibroblast growth factor, express the NSC markers Nestin and Sox2, self-renew, and differentiate into neuron-like and glial cells in vitro. More importantly, these cells can propagate and recapitulate tumors when implanted into the brain of syngeneic Fisher rats, and they display a more aggressive course compared with 9L gliosarcoma cells grown in monolayer cultures devoid of mitogens. Furthermore, we compare the chemosensitivity and proliferation rate of 9L gliosarcoma cells grown as a monolayer to those of cells grown as floating spheres and show that the sphere-generated cells have a lower proliferation rate, are more chemoresistant, and express several antiapoptosis and drug-related genes, which may prove to have important clinical implications. Disclosure of potential conflicts of interest is found at the end of this article.

C-Met Antisense Oligodeoxynucleotides as a Novel Therapeutic Agent for Glioma: In Vitro and In Vivo Studies of Uptake, Effects, and Toxicity

c-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor, are critical in cellular proliferation, motility, and invasion and are known to be overexpressed in gliomas. The aim of our study was to investigate the uptake and effects of c-Met antisense oligodeoxynucleotides (ASODNs) on rat and human glioma cells in vitro and the uptake and toxicity of these nucleotides in rat carcinomatosis and brain tumor models. The three human cell lines (U87, BT325, SHG44) and the C6 rat glioma cell line were cultured. To study the uptake of oligodeoxynucleotides (ODNs) by glioma cells in vitro, cultured glioma cells readily incorporated caroboxyfluorescein-5-succimidyl ester (FAM) labeled phosphorothioate oligodeoxynucleotides, as demonstrated by immunofluorescence microscopy and flow cytometry. To study the effect of ASODNs treatment on c-Met expression in vitro, Expression of c-Met was assessed by immunofluorescence microscopy and reverse transcriptase polymerase chain reaction (RT-PCR) analysis. For animal studies of ODNs toxicity and uptake, eight rats underwent placement of cisternal catheters, under general anesthesia. Four rats were given 24 mug FAM-labeled ASODNs while the others were given a saline control injection. After a 24 h observation period, rats were sacrificed by barbiturate overdose, and their brains were studied. For all cell lines, fluorescence was seen to increase with increasing ASODNs concentration. Cells treated in similar fashion were also analyzed by flow cytometry to graphically illustrate the differing fluorescence. Multiple glioma cell lines were tested, with similar results. c-Met ASODNs was found to be successfully incorporated from the media into cultured human glioma cells, even at concentrations as low as 2 muM. In addition, maintenance of the pH-dependent green fluorescence color, as seen by immunofluorescence microscopy and by using flow cytometry, indicated that the FAM was not contained within lysosomes. Immunofluorescence microscopy and RT-PCR analysis showed decreases in c-Met expression with oligodeoxynucleotides treatment. Uptake into tumor cells was also demonstrated in vivo, with no detectable toxicity at concentrations exceeding expected therapeutic levels. These data are encouraging for further study of c-Met antisense oligodeoxynucleotides as a therapeutic modality for glioma.

Dexamethasone enhances adenosine 5′-triphosphate-sensitive potassium channel expression in the blood–brain tumor barrier in a rat brain tumor model

This study was performed to determine whether dexamethasone (DEX) had an effect on ATP-sensitive potassium channels ( K ATP channels) in blood–brain tumor barrier (BTB). Using a rat brain glioma model, we found that DEX could significantly increase the expression of K ATP channels protein at tumor sites. And bradykinin-induced increase of K ATP channels protein was further enhanced after DEX pretreatment for 3 consecutive days via Western blots and immunohistochemistry methods. In addition, DEX pretreatment enhanced bradykinin-mediated increase of the density of I KATP in the cultured rat C6 glioma cells using the patch-clamp technique in a whole-cell configuration. DEX significantly decreased the BTB permeability, but it did not reduce bradykinin-mediated BTB permeability increase, which were significantly attenuated by the K ATP channel antagonist glibenclamide. This led to the conclusion that DEX-mediated change in BTB permeability is, at least partly, due to accelerated formation of K ATP channel, an important target in the biochemical regulation of this process.

Photodynamic effects of SIM01, a new sensitizer, on experimental brain tumors in rats

Background Glioblastomas are the third most common cause of cancer death in patients between 15 and 35 years old. Literature suggests that PDT could represent a promising treatment, providing that sensitizers could accumulate within the cancer tissues despite the blood-brain barrier. Methods Distribution and PDT effect of SIM01, a promising photosensitizer, have been evaluated on orthotopic C6 tumor model in rats by comparison with HPD and m-THPC. Pharmacokinetics had been analyzed with fluorescence and ROS. Photodynamic treatment was done using a 630-nm light with an energy density of 100 J cm −2 for HPD and a 652-nm light with an energy density of 20 J cm −2 for m-THPC and SIM01. Results The correlation between fluorescence and ROS dosimetry was found to be excellent. An optimal concentration was found after 12 hours for SIM01 (4 mg/kg), 24 hours for HPD (10 mg/kg), and 48 hours for m-THPC (4 mg/kg). The best normal tissue/cancer ratio of concentration had been found after 12 hours for SIM01 and 48 hours for HPD and m-THPC. Pathological examinations after PDT showed that the criteria for histology of glioblastic origin were absent in SIM01-treated rats 12 hours after injection but were present in 50% of rats treated 24 hours after injection and in all after a 48-hour delay. Mean survival of rats treated 12 or 24 hours after SIM01 injection was significantly improved compared with controls, HPD-, or m-THPC-treated groups. Survival of rats treated 12 or 24 hours after SIM01 injection reached 20 days but decreased for longer delays. On the contrary, survival reached 18 days at the maximum for rats treated 48 hours after m-THPC or HPD injection. Conclusions Our results confirm that PDT is a promising treatment for glioblastomas. SIM01 efficacy is as efficient as m-THPC but with much more favorable pharmacokinetics.

Diffusion tensor MRI in rat models of invasive and well‐demarcated brain tumors

Diffusion tensor imaging (DTI) and its metrics, such as mean diffusivity (MD) and fractional anisotropy (FA), have been used to detect the extent of brain tumors and understand tumor growth and its influence on the surrounding tissue. However, there are conflicting reports on how DTI metrics can be used for tumor diagnosis. The physiological interpretation of these metrics in terms of tumor growth is also not clear. The objective of this study was to investigate the DTI parameters in two rat brain tumor models (9L and F98) with different patterns of aggressiveness by longitudinal monitoring of tumor growth and comparing the DTI parameters of these two tumor models. In addition to the standard DTI metrics, MD and FA, we measured other metrics representing diffusion tensor shape, such as linear and planar anisotropy coefficients (CL and CP), and orientational coherence measured by lattice index (LI), to characterize the two tumor models. The 9L tumor had higher FA, CL, and LI than the F98 tumor. F98 had a larger difference in anisotropies between tumor and peritumor regions than 9L. From the eigenvalues, it was found that the increase in CL and trace of the 9L tumor was due to an increase in the primary eigenvalue, whereas the increase in CP in the peritumor region was due to an increase in both primary and secondary eigenvalues and a decrease in tertiary eigenvalue. Our results indicate that shape-oriented anisotropy measures, such as CL and CP, and orientational coherence measures, such as LI, can provide useful information in differentiating these two tumor models and also differentiating tumor from peritumoral regions.

Lack of promoting effects of chronic exposure to 1.95‐GHz W‐CDMA signals for IMT‐2000 cellular system on development of N‐ethylnitrosourea‐induced central nervous system tumors in F344 rats

The present study was performed to evaluate effects of a 2-year exposure to an electromagnetic near-field (EMF) equivalent to that generated by cellular phones on tumor development in the central nervous system (CNS) of rats. For this purpose, pregnant F344 rats were given a single administration of N-ethylnitrosourea (ENU) on gestational day 18. A total of 500 pups were divided into five groups, each composed of 50 males and 50 females: Group 1, untreated controls; Group 2, ENU alone; Groups 3 to 5, ENU + EMF (sham exposure and two exposure levels). A 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is a feature of the International Mobile Telecommunication 2000 (IMT-2000) cellular system was employed for exposure of the rat head starting from 5 weeks of age, 90 min a day, 5 days a week, for 104 weeks. Brain average specific absorption rates (SARs) were designed to be .67 and 2.0 W/kg for low and high exposures, respectively. The incidence and numbers of brain tumors in female rats exposed to 1.95-GHz W-CDMA signals showed tendencies to increase but without statistical significance. Overall, no significant increase in incidences or numbers, either in the males or females, was detected in the EMF-exposed groups. In addition, no clear changes in tumor types in the brain were evident. Thus, under the present experimental conditions, exposure of heads of rats to 1.95-GHz W-CDMA signals for IMT-2000 for a 2-year period was not demonstrated to accelerate or otherwise affect ENU-initiated brain tumorigenesis.

Quantifying the A1AR distribution in peritumoural zones around experimental F98 and C6 rat brain tumours

Quantification of growth in experimental F98 and C6 rat brain tumours was performed on 51 rat brains, 17 of which have been further assessed by 3D tumour reconstruction. Brains were cryosliced and radio-labelled with a ligand of the peripheral type benzodiazepine-receptor (pBR), (3)H-Pk11195 [(1-(2-chlorophenyl)-N-methyl-N-(1-methyl-propylene)-3-isoquinoline-carboxamide)] by receptor autoradiography. Manually segmented and automatically registered tumours have been 3D-reconstructed for volumetric comparison on the basis of (3)H-Pk11195-based tumour recognition. Furthermore automatically computed areas of -300 microm inner (marginal) zone as well as 300 microm and 600 microm outer tumour space were quantified. These three different regions were transferred onto other adjacent slices that had been labelled by receptor autoradiography with the A(1) Adenosine receptor (A(1)AR)-ligand (3)H-CPFPX ((3)H-8-cyclopentyl-3-(3-fluorpropyl)-1-propylxanthine) for quantitative assessment of A(1)AR in the three different tumour zones. Hence, a method is described for quantifying various receptor protein systems in the tumour as well as in the marginal invasive zones around experimentally implanted rat brain tumours and their representation in the tumour microenvironment as well as in 3D space. Furthermore, a tool for automatically reading out radio-labelled rat brain slices from auto radiographic films was developed, reconstructed into a consistent 3D-tumour model and the zones around the tumour were visualized. A(1)AR expression was found to depend upon the tumour volume in C6 animals, but is independent on the time of tumour development. In F98 animals, a significant increase in A(1)AR receptor protein was found in the Peritumoural zone as a function of time of tumour development and tumour volume.

Assessment of the morphological and functional effects of the anti‐angiogenic agent SU11657 on 9L gliosarcoma vasculature using dynamic susceptibility contrast MRI

To investigate the influence of anti-angiogenic agents on tumor perfusion, we employed a dynamic susceptibility contrast (DSC)-MRI method that utilizes a simultaneous gradient-echo (GE) and spin-echo (SE) imaging sequence to derive perfusion parameters (blood flow, blood volume, and mean transit time (MTT)). These parameters are sensitive to both the total vasculature (from the GE data) and the microvasculature (from the SE data), and can also provide a measure of the mean vessel diameter (mVD). This approach was used to evaluate the response of a 9L rat brain tumor model to 20 mg/kg and 40 mg/kg of the anti-angiogenic agent SU11657. The 20-mg/kg dose significantly decreased mVD by 29.9% (P = 0.02). The 40-mg/kg dose significantly decreased mVD by 30.4% (P = 0.0007), SE blood volume by 31.8% (P = 0.03), GE and SE MTT by 46.9% (P = 0.03) and 62.0% (P = 0.0005), and increased GE and SE blood flow by 36.6% (P = 0.04) and 52.6% (P = 0.02). These findings demonstrate that DSC-MRI perfusion methods can play a key role in the noninvasive evaluation of morphological and functional changes in tumor vasculature in response to therapy.

Utility of the F98 Rat Glioma Model for Photodynamic Therapy

A syngeneic rat brain tumor model consisting of F98 glioma cells in Fischer rats was investigated for its utility in PDT studies. Results of in vitro studies demonstrated that the F98 cell line was sensitive to ALA-PDT, especially at low light irradiances. Histological examination revealed that F98 tumors share many fundamental characteristics with human GBMs, including rapid growth and infiltrative behavior. ALA-PDT in normal brain showed that high light fluences (26 J) delivered at relatively low powers (10 mW) are capable of causing significant edema. These findings suggest that light irradiation parameters should be chosen carefully when treating tumor-bearing animals. Rats inoculated with F98 cells preincubated in ALA showed a significant survival advantage following light exposure. Taken together, the results suggest that the F98 rat glioma model is appropriate for PDT studies of malignant gliomas.

Genetically engineered neural stem cells migrate and suppress glioma cell growth at distant intracranial sites

Our previous study demonstrated successful treatment of an established rat brain tumor through the bystander effect by intra-tumoral injection of neural stem cells transduced with herpes simplex virus-thymidine kinase gene (NSCtk) followed by systemic ganciclovir (GCV) administration (NSCtk therapy). Since glioma has a strong tendency to infiltrate into surrounding brain tissue and that is one of the main causes of local treatment failure, we, in the present study, injected NSCtk cells at distant sites of rat brain tumors and evaluated migratory potential of NSCtk toward the tumor and anti-tumor effects of the NSCtk therapy of this experimental setting. NSCtk cells were intracranially implanted either at 2 mm medial in the ipsilateral hemisphere or at the mirror point in the contralateral hemisphere to the C6 rat glioma cell implantation. Active migration of NSCtk cells toward C6 cells was observed even when NSCtk cells were implanted in the contralateral hemisphere. When GCV was systemically administered, growth of intracranial tumor was markedly inhibited and the survival was significantly prolonged through the bystander effect by NSCtk cells migrated from distant injection sites of the tumor. The results of the present study suggest that NSCtk therapy is still effective in the area far from the NSCtk injection site and, therefore, suitable for treatment of malignant gliomas that deeply infiltrate and widely disseminate in the brain.