Intracerebral 9L Gliosarcoma Research Articles

An in vivo multimodal feasibility study in a rat brain tumour model using flexible multinuclear MR and PET systems

BackgroundIn addition to the structural information afforded by 1H MRI, the use of X-nuclei, such as sodium-23 (23Na) or phosphorus-31 (31P), offers important complementary information concerning physiological and biochemical parameters. By then combining this technique with PET, which provides valuable insight into a wide range of metabolic and molecular processes by using of a variety of radioactive tracers, the scope of medical imaging and diagnostics can be significantly increased. While the use of multimodal imaging is undoubtedly advantageous, identifying the optimal combination of these parameters to diagnose a specific dysfunction is very important and is advanced by the use of sophisticated imaging techniques in specific animal models.MethodsIn this pilot study, rats with intracerebral 9L gliosarcomas were used to explore a combination of sequential multinuclear MRI using a sophisticated switchable coil set in a small animal 9.4 T MRI scanner and, subsequently, a small animal PET with the tumour tracer O-(2-[18F]-fluoroethyl)-L-tyrosine ([18F]FET). This made it possible for in vivo multinuclear MR-PET experiments to be conducted without compromising the performance of either multinuclear MR or PET.ResultsHigh-quality in vivo images and spectra including high-resolution 1H imaging, 23Na-weighted imaging, detection of 31P metabolites and [18F]FET uptake were obtained, allowing the characterisation of tumour tissues in comparison to a healthy brain. It has been reported in the literature that these parameters are useful in the identification of the genetic profile of gliomas, particularly concerning the mutation of the isocitrate hydrogenase gene, which is highly relevant for treatment strategy.ConclusionsThe combination of multinuclear MR and PET in, for example, brain tumour models with specific genetic mutations will enable the physiological background of signal alterations to be explored and the identification of the optimal combination of imaging parameters for the non-invasive characterisation of the molecular profile of tumours.

Synchrotron microbeam radiation therapy induces hypoxia in intracerebral gliosarcoma but not in the normal brain

PurposeSynchrotron microbeam radiation therapy (MRT) is an innovative irradiation modality based on spatial fractionation of a high-dose X-ray beam into lattices of microbeams. The increase in lifespan of brain tumor-bearing rats is associated with vascular damage but the physiological consequences of MRT on blood vessels have not been described. In this manuscript, we evaluate the oxygenation changes induced by MRT in an intracerebral 9L gliosarcoma model. MethodsTissue responses to MRT (two orthogonal arrays (2×400Gy)) were studied using magnetic resonance-based measurements of local blood oxygen saturation (MR_SO2) and quantitative immunohistology of RECA-1, Type-IV collagen and GLUT-1, marker of hypoxia. ResultsIn tumors, MR_SO2 decreased by a factor of 2 in tumor between day 8 and day 45 after MRT. This correlated with tumor vascular remodeling, i.e. decrease in vessel density, increases in half-vessel distances (×5) and GLUT-1 immunoreactivity. Conversely, MRT did not change normal brain MR_SO2, although vessel inter-distances increased slightly. ConclusionWe provide new evidence for the differential effect of MRT on tumor vasculature, an effect that leads to tumor hypoxia. As hypothesized formerly, the vasculature of the normal brain exposed to MRT remains sufficiently perfused to prevent any hypoxia.

Preferential Effect of Synchrotron Microbeam Radiation Therapy on Intracerebral 9L Gliosarcoma Vascular Networks

Synchrotron microbeam radiation therapy (MRT) relies on spatial fractionation of the incident photon beam into parallel micron-wide beams. Our aim was to analyze the effects of MRT on normal brain and 9L gliosarcoma tissues, particularly on blood vessels. Responses to MRT (two arrays, one lateral, one anteroposterior (2 × 400 Gy), intersecting orthogonally in the tumor region) were studied during 6 weeks using MRI, immunohistochemistry, and vascular endothelial growth factor Western blot. MRT increased the median survival time of irradiated rats (×3.25), significantly increased blood vessel permeability, and inhibited tumor growth; a cytotoxic effect on 9L cells was detected 5 days after irradiation. Significant decreases in tumoral blood volume fraction and vessel diameter were measured from 8 days after irradiation, due to loss of endothelial cells in tumors as detected by immunochemistry. Edema was observed in the normal brain exposed to both crossfired arrays about 6 weeks after irradiation. This edema was associated with changes in blood vessel morphology and an overexpression of vascular endothelial growth factor. Conversely, vascular parameters and vessel morphology in brain regions exposed to one of the two arrays were not damaged, and there was no loss of vascular endothelia. We show for the first time that preferential damage of MRT to tumor vessels versus preservation of radioresistant normal brain vessels contributes to the efficient palliation of 9L gliosarcomas in rats. Molecular pathways of repair mechanisms in normal and tumoral vascular networks after MRT may be essential for the improvement of such differential effects on the vasculature.

Evaluation of treatment-associated inflammatory response on diffusion-weighted magnetic resonance imaging and 2-[18F]-fluoro-2-deoxy-D-glucose-positron emission tomography imaging biomarkers.

Functional imaging biomarkers of cancer treatment response offer the potential for early determination of outcome through the assessment of biochemical, physiologic, and microenvironmental readouts. Cell death may result in an immunologic response, thus complicating the interpretation of biomarker readouts. This study evaluated the temporal effect of treatment-associated inflammatory activity on diffusion magnetic resonance imaging and 2-[(18)F]-fluoro-2-deoxy-D-glucose-positron emission tomography imaging (FDG-PET) biomarkers to delineate the effects of the inflammatory response on imaging readouts. Rats with intracerebral 9L gliosarcomas were separated into four groups consisting of control, an immunosuppressive agent dexamethasone (Dex), 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and BCNU+Dex. Animals were imaged using diffusion-weighted magnetic resonance imaging and FDG-PET at 0, 3, and 7 days posttreatment. In the BCNU- and BCNU+Dex-treated animal groups, diffusion values increased progressively over the 7-day study period to approximately 23% over baseline. The FDG percentage change of standard uptake value decreased at day 3 (-30.9%) but increased over baseline levels at day 7 (+20.1%). FDG-PET of BCNU+Dex-treated animals were found to have percentage of standard uptake value reductions of -31.4% and -24.7% at days 3 and 7, respectively, following treatment. Activated macrophages were observed on day 7 in the BCNU treatment group with much fewer found in the BCNU+Dex group. Results revealed that treatment-associated inflammatory response following tumor therapy resulted in the accentuation of tumor diffusion response along with a corresponding increase in tumor FDG uptake due to the presence of glucose-consuming activated macrophages. The dynamics and magnitude of potential inflammatory response should be considered when interpreting imaging biomarker results.

Irradiation of intracerebral 9L gliosarcoma by a single array of microplanar x-ray beams from a synchrotron: balance between curing and sparing

The purpose of this work was the understanding of microbeam radiation therapy at the ESRF in order to find the best compromise between curing of tumors and sparing of normal tissues, to obtain a better understanding of survival curves and to report its efficiency. This method uses synchrotron-generated x-ray microbeams. Rats were implanted with 9L gliosarcomas and the tumors were diagnosed by MRI. They were irradiated 14 days after implantation by arrays of 25 µm wide microbeams in unidirectional mode, with a skin entrance dose of 625 Gy. The effect of using 200 or 100 µm center-to-center spacing between the microbeams was compared. The median survival time (post-implantation) was 40 and 67 days at 200 and 100 µm spacing, respectively. However, 72% of rats irradiated at 100 µm spacing showed abnormal clinical signs and weight patterns, whereas only 12% of rats were affected at 200 µm spacing. In parallel, histological lesions of the normal brain were found in the 100 µm series only. Although the increase in lifespan was equal to 273% and 102% for the 100 and 200 µm series, respectively, the 200 µm spacing protocol provides a better sparing of healthy tissue and may prove useful in combination with other radiation modalities or additional drugs.

Synergy of gene-mediated immunoprophylaxis and microbeam radiation therapy for advanced intracerebral rat 9L gliosarcomas

Microbeam radiation therapy (MRT), a novel experimental radiosurgery that largely spares the developing CNS and other normal tissues, is tolerated well by developing animals and palliates advanced 9LGS tumors. This report, to our knowledge, is the first demonstration that gene-mediated immunotherapy (GMIMPR) enhances the efficacy of MRT for advanced 9LGS tumors. Seventy-six male Fischer 344 rats were implanted ic with 10(4)9LGS cells on d0. By d14, the cells had generated approximately approximately 40 mm3 ic 9LGS tumours, experimental models for therapy of moderately aggressive human malignant astrocytomas. Each of the 14 untreated (control) rats died from a large (>100 mg) ic tumor before d29 (median, d21). On d14, the remaining 62 rats were given deliberately suboptimal microbeam radiation therapy (MRT) by a single lateral exposure of the tumor-bearing zone of the head to a 10.1 mm-wide, approximately approximately 11 mm-high array of 20-39 microm-wide, nearly parallel beams of synchrotron wiggler-generated radiation (mainly approximately 50-150 keV X-rays) that delivered 625 Gy peak skin doses at approximately approximately 211 microm ctc intervals in approximately approximately 300 ms either without additional treatments (MRT-only, 25 rats), with post-MRT GMIMPR (MRT+GMIMPR, 23 rats: multiple sc injections of irradiated (clonogenically-disabled) GM-CSF gene-transfected 9LGS cells), or with post-MRT IMPR (MRT+IMPR, 14 rats: multiple sc injections of irradiated (clonogenically-disabled) 9LGS cells. The median post-implantation survivals of rats in the MRT-only, MRT+GMIMPR and MRT+IMPR groups were over twice that of controls; further, approximately approximately 20% of rats in MRT-only and MRT+IMPR groups survived >1 yr with no obvious disabilities. Moreover, over 40% of MRT+GMIMPR rats survived >1 yr with no obvious disabilities, a significant (P<0.04) increase over the MRT-only and MRT+IMPR groups. These data suggest that the combination of MRT+GMIMPR might be better than MRT only for unifocal CNS tumors, particularly in infants and young children.

A cyclooxygenase-2 (COX-2) inhibitor compared with dexamethasone in a survival study of rats with intracerebral 9L gliosarcomas.

Although dexamethasone is very effective for controlling peritumoral cerebral edema, it is associated with distressing side effects that decrease the quality of life for many patients. One potential mechanism to explain the ability of dexamethasone to repair blood-brain barrier dysfunction is through the inhibition of cyclooxygenase-2 (COX-2). The purpose of this study was to determine in a rat brain tumor model whether SC-236, a selective COX-2 inhibitor, is as effective as dexamethasone. Twenty-nine adult male Fischer 344 rats were implanted with intracerebral 9L gliosarcomas and divided into 3 treatment groups. One group (n = 9) served as controls, another (n = 9) was treated with dexamethasone (3 mg/kg p.o. daily), and a third group (n = 11) received SC-236 (3 mg/kg p.o. daily). A survival study was performed. The median survival in the control group was 16 days, compared with 23 days for the dexamethasone group and 23 days for the COX-2 inhibitor group. Kaplan-Meier analysis on pairwise group comparisons showed improved survival that was statistically significant for each treatment group compared with the control group (log-rank test P = 0.009 for dexamethasone to control and P = 0.005 for COX-2 to control), and no significant difference in survival for the COX-2 compared with dexamethasone (log-rank test P = 0.2). These results suggest that a selective COX-2 inhibitor appears to be as effective as dexamethasone in prolonging survival in a rat brain tumor model.

A cyclooxygenase-2 (COX-2) inhibitor compared with dexamethasone in a survival study of rats with intracerebral 9L gliosarcomas

A cyclooxygenase-2 (COX-2) inhibitor compared with dexamethasone in a survival study of rats with intracerebral 9L gliosarcomas

A cyclooxygenase-2 (COX-2) inhibitor compared with dexamethasone in a survival study of rats with intracerebral 9L gliosarcomas

A cyclooxygenase-2 (COX-2) inhibitor compared with dexamethasone in a survival study of rats with intracerebral 9L gliosarcomas

The combination of X-ray-mediated radiosurgery and gene-mediated immunoprophylaxis for advanced intracerebral gliosarcomas in rats.

Rats with advanced, imminently lethal, approximately 4 mm diameter, left-sided intracerebral 9L gliosarcoma (9LGS), a well characterized malignant tumor with some similarities to human high-grade astrocytomas, were used as a therapy model 14 days post-implantation of 10(4) cells. Such tumor-bearing rats die within two weeks (median, 6 days) thereafter if untreated. However, if these tumors are exposed on day 14 to 12-25 Gy of an electron-equilibrated 6 MV photon beam (radiosurgery), survival is extended about 5-6 fold to a median of 34 days, but long-term survival (> 1 year) is increased only to approximately 18%. Multiple subcutaneous inoculations of radiation-disabled 9LGS cells post-radiosurgery (immunoprophylaxis) extended lifespan and long-term (> 1 year) survival minimally (median, 37 days; 25%, respectively). In sharp contrast, radiosurgery followed by multiple subcutaneous inoculations of radiation-disabled 9LGS cells that had been transfected with granulocyte macrophage colony stimulating factor (GMCSF), a cytokine with demonstrated immune-enhancing properties (i.e. gene-mediated immunoprophylaxis, GMIMPR) increased long-term survival to approximately 67%. To our knowledge, these results are the first to show that the combination of photon radiosurgery and GMIMPR is effective for an advanced, imminently lethal brain tumor in a mammal. These data raise the possibility that GMIMPR following radiation therapy might prove effective for the treatment of some human malignant gliomas.

Intraarterial delivery of adenovirus vectors and liposome-DNA complexes to experimental brain neoplasms.

This study investigated the intraarterial delivery of genetically engineered replication-deficient adenovirus vectors (AVs) and cationic liposome-plasmid DNA complexes (lipoDNA) to experimental brain tumors. Adenovirus or lipoDNA was injected into the internal carotid artery (ICA) of F344 rats harboring intracerebral 9L gliosarcomas, using bradykinin (BK) to selectively permeabilize the blood-tumor barrier (BTB). Brain and internal organs of the animals were collected 48 hr after vector injection and stained for expression of the marker gene product, beta-galactosidase (beta-Gal). Intracarotid delivery of AV to 9L rat gliosarcoma without BTB disruption resulted in transgene expression in 3-10% of tumor cells distributed throughout the tumor. Virus-mediated expression of beta-gal gene products in this tumor model was particularly high in small foci (< or = 0.5 mm), which had invaded the normal brain tissue surrounding the main tumor mass. In these foci more than 50% of tumor cells were transduced. BK infusion increased the amount of transgene-expressing cells in larger tumor foci to 15-30%. In the brain parenchyma only a few endothelial cells expressed beta-gal owing to AV-mediated gene transfer. Intracarotid delivery of lipoDNA bearing a cytoplasmic expression cassette rendered more than 30% of the tumor cells positive for the marker gene without BTB disruption. The pattern of distribution was in general homogeneous throughout the tumor. BK infusion was able to increase further the number of transduced tumor cells to more than 50%. Although lipoDNA-mediated gene transfer showed increased efficacy as compared with AV-mediated gene transfer, it had less specificity since a larger number of endothelial and glial cells also expressed the transgene. AV and lipoDNA injections, in the absence and presence of BK, also resulted in transduction of peripheral organs. AV showed its known predilection for liver and lung. In the case of lipoDNA, parenchymal organs such as liver, lung, testes, lymphatic nodes, and especially spleen, were transduced. These findings indicate that intracarotid application of AV and lipoDNA vectors can effectively transduce tumor cells in the brain, and that BTB modulation by BK infusion can further increase the number of transgene-expressing tumor cells.

Comparative Assessment of Single-Dose and Fractionated Boron Neutron Capture Therapy

The effects of fractionating boron neutron capture therapy (BNCT) were evaluated in the intracerebral rat 9L gliosarcoma and rat spinal cord models using the Brookhaven Medical Research Reactor (BMRR) thermal neutron beam. The amino acid analog p-boronophenylalanine (BPA) was administered prior to each exposure to the thermal neutron beam. The total physical absorbed dose to the tumor during BNCT using BPA was 91% high-linear energy transfer (LET) radiation. Two tumor doses of 5.1 Gy spaced 48 h apart (n = 14) or three tumor doses of 5.2 Gy, each separated by 48 h (n = 10), produced 43 and 70% long-term (> 1 year) survivors, respectively [corrected]. The outcome of neither the two nor the three fractions of radiation was statistically different from that of the corresponding single-fraction group. In the rat spinal cord, the ED50 for radiation myelopathy (as indicated by limb paralysis within 7 months) after exposure to the thermal beam alone was 13.6 +/- 0.4 Gy. Dividing the beam-only irradiation into two or four consecutive daily fractions increased the ED50 to 14.7 +/- 0.2 Gy and 15.5 +/- 0.4 Gy, respectively. Thermal neutron irradiation in the presence of BPA resulted in an ED50 for myelopathy of 13.8 +/- 0.6 Gy after a single fraction and 14.9 +/- 0.9 Gy after two fractions. An increase in the number of fractions to four resulted in an ED50 of 14.3 +/- 0.6 Gy. The total physical absorbed dose to the blood in the vasculature of the spinal cord during BNCT using BPA was 80% high-LET radiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective uptake of viral and monocrystalline particles delivered intra-arterially to experimental brain neoplasms.

In this study we investigated the intra-arterial delivery of viral and nonviral particles to experimental brain tumors. A herpes simplex virus (HSV) vector and monocrystalline iron oxide nanoparticles (MION) were injected into the internal carotid artery of Fisher 344 rats harboring intracerebral 9L gliosarcomas, using bradykinin to disrupt the blood-tumor barrier. Brain and internal organs were stained both for virus-mediated gene expression and for iron. Quantitative comparisons of gene expression and MION uptake with and without blood-tumor barrier disruption were performed in the center and at the periphery of the tumor mass, as well as in normal brain. In addition, MION distribution was traced in vivo by MR imaging. Delivery of HSV into 9L gliosarcoma cells was greatly enhanced by intra-carotid bradykinin infusion. Virus-mediated expression of the HSV-thymidine kinase (TK) and beta-galactosidase gene products was highest at the tumor periphery as compared to the tumor center. Selective HSV infection of multiple tumor foci was achieved in both hemispheres without affecting normal brain. MION uptake was high at the tumor periphery even without blood-tumor barrier disruption. Bradykinin increased MION uptake predominantly in the center of the tumor with virtually no effect at the periphery. These findings show that selective blood-tumor barrier disruption by bradykinin can be used to enhance HSV-mediated gene delivery to tumor cells in the periphery of brain tumors. A crucial aspect in the treatment of malignant brain tumors is the eradication of tumor cells infiltrating the brain; bradykinin may facilitate access of vectors to these areas by selective disruption of their neovasculature.

Design of a multislit, variable width collimator for microplanar beam radiotherapy

Microbeam radiation therapy of the intracerebral 9L gliosarcoma in rats, an experimental surrogate for human malignant gliomas, using mainly 30–130 keV wiggler-generated x rays, extended the residual lifespans of some rats ten or more times over those of untreated, similar gliosarcoma-bearing rats. The rats were exposed 300 or 600 times to an upright, 25-μm-wide, 4-mm-high x-ray beam. A multislit collimator has been designed to shorten the time required for the therapy.

Neutron capture therapy of the 9l rat gliosarcoma using the P-boronophenylalanine-fructose complex

Purpose : Intraperitoneal (IP) injection of the solubilized fructose complex of L- p-boronophenylalanine (BPA-F) produced higher boron concentrations in a rat brain tumor model than was possible using intragastric (IG) administration of L- p-boronophenylalanine (BPA). The effectiveness of IP BPA-F was compared to IG BPA in boron neutron capture therapy irradiations of the 9L rat brain tumor model. Methods and Materials : The time course of boron accumulation in tumor and normal tissues was determined in male F344 rats bearing either SC or intracerebral 9L gliosarcomas following a single IP injection of BPA-F. On day 14 after inoculation of intracranial tumors, rats were irradiated with single doses of either: 250 kVp X rays; the thermal neutron beam of the Brookhaven Medical Research Reactor following IG administration of BPA; or thermal neutrons following IP injection of BPA-F. Magnetic resonance imaging was used to visualize the tumor scars and to assess damage to the normal brain in long-term survivors. Results : 4 h after IP injection of 1200 mg/kg of BPA-F the boron concentrations in tumor, blood, and normal brain were 89.6 ± 7.6, 27.7 ± 2.8 and 17.5 ± 1.5 μg 10B/g, respectively. Two IG doses of BPA (750 mg/kg each, 3 h apart) produced 39 ± 5, 12 ± 1 and 10 ± 1 μg 10B/g in tumor, blood and brain, respectively at 5 h after the second dose. Three groups of rats were treated with thermal neutrons: one following IG BPA and two groups following IP BPA-F. The total physical absorbed doses to the tumor in the three BNCT groups were 15.5 Gy (IG BPA, n = 12), 17.0 Gy (IP BPA-F, n = 8), and 31.5 Gy (IP BPA-F, n = 8), respectively. The median survival of the untreated controls was 22 days. The median survival of the rats treated with 22.5 Gy of 250 kVp X rays ( n = 23) was 35 days with 20% long-term survivors. Fifty percent of the rats in the IG BPA + thermal neutrons group survived over 1 year. All rats in both groups that received IP BPA-F + thermal neutrons have survived over 8 months. Magnetic resonance imaging of the brains of the long-term boron neutron capture therapy survivors showed a scar at the site of tumor implantation in all animals. In the IP BPA-F high-dose group one rat showed evidence of edema and one rat showed a fluid-filled cyst replacing the tumor. Conclusion : The use of IP BPA-F has significantly improved long-term survival compared to IG BPA. The high percentage of long-term tumor control (100%, n = 16) in the intracerebral rat 9L gliosarcoma brain tumor model, together with little or no damage to the surrounding normal brain in the majority of surviving animals, demonstrate the substantial therapeutic gain produced by boron neutron capture therapy.

The effect of interleukin-2 on the blood-brain barrier in the 9L gliosarcoma rat model.

Carbon-14-labeled aminoisobutyric acid was used to determine local blood-to-tissue transfer constants in 22 Fischer rats with intracerebral 9L gliosarcomas that received either high-dose parenteral interleukin-2 (IL-2) or a control injection. In tumor and peritumoral tissue, the transfer constants in the IL-2-treated animals (89.6 +/- 14.6 and 35.8 +/- 6.0, respectively, mean +/- standard error of the mean) were larger (p less than 0.05) than in control animals (61.4 +/- 6.4 and 14.6 +/- 2.2, respectively). In contrast, in normal frontal and occipital tissue contralateral to the tumor-bearing hemisphere, there was no significant difference between the transfer constants in IL-2-treated and control animals. Furthermore, treatment of animals with IL-2 excipient caused no change in permeability as compared to animals treated with Hanks' balanced salt solution. Parenteral injection of IL-2 increases blood-brain barrier disruption in tumor-bearing rat brain but does not increase the vascular permeability of normal brain. Methods to prevent this increased tumor vessel permeability are required before parenteral IL-2 can be used safely for the treatment of primary or metastatic brain tumors.

Distribution of hematoporphyrin derivative in the rat 9l gliosarcoma brain tumor analyzed by digital video fluorescence microscopy.

A digital video fluorescence microscopy technique was used to evaluate the distribution of hematoporphyrin derivative (HPD) in the rat intracerebral 9L gliosarcoma brain-tumor model at 4, 24, 48, and 72 hours after intravenous administration of 10 mg/kg of the drug. Compared to surrounding normal brain, there was significant preferential uptake of HPD into the tumor. In sections surveyed, fluorescence reached a maximum value by 24 hours; however, only 33% to 44% of the tumor was fluorescent. In contrast, fluorescence within the surrounding normal brain was maximum at 4 hours, but was present in less than 1% of the brain tissue evaluated. The effect of HPD sensitization to a laser light dose (633 nm) of 30 joules/sq cm delivered through the intact skull was evaluated histologically in 10 rats. A patchy coagulation necrosis, possibly corresponding to the distribution of HPD fluorescence seen within the tumor, was observed. There was evidence that photoradiation therapy (PRT) affects defective tumor vasculature and that a direct tumor cell toxicity spared normal brain tissue. Despite these findings, limited uptake of HPD in tumor and the brain adjacent to tumor may decrease the effectiveness of PRT in the 9L gliosarcoma brain-tumor model. Because of the similarity between the capillary system of the 9L tumor and human brain tumors, PRT may have a limited therapeutic effect in patients with malignant brain tumors.

Combination Therapy with 1,3-Bis(2-chloroethyl)-1-nitrosourea and Low Dose Rate Radiation in the 9L Rat Brain Tumor and Spheroid Models: Implications for Brain Tumor Brachytherapy

We studied the effects of combination treatment with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and low dose rate radiation in the 9L rat brain tumor in vivo model and the 9L multicellular tumor spheroid model. F-344 rats bearing intracerebral 9L gliosarcomas were implanted with removable 125I sources. Minimal (peripheral) tumor doses of 6387 rad produced an increased life-span (ILS) of 28% over that of control rats implanted with dummy sources, BCNU alone (13.3 mg/kg) produced in an ILS of 67%, and combination treatment with BCNU and implanted 125I sources produced an ILS of 167%. As measured by a colony-forming efficiency assay, the greatest cell kill in 9L spheroids occurred when BCNU was administered 24 hours before irradiation from a 137Cs source at a low dose rate of 5 rad/minute. At a higher dose rate of 210 rad/minute, the time dependence of the effects of combination treatment was identical and therefore independent of dose rate.

Combination Therapy with 1,3-Bis(2-chloroethyl)-1-nitrosourea and Low Dose Rate Radiation in the 9L Rat Brain Tumor and Spheroid Models: Implications for Brain Tumor Brachytherapy

We studied the effects of combination treatment with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and low dose rate radiation in the 9L rat brain tumor in vivo model and the 9L multicellular tumor spheroid model. F-344 rats bearing intracerebral 9L gliosarcomas were implanted with removable 125I sources. Minimal (peripheral) tumor does of 6387 rad produced an increased life-span (ILS) of 28% over that of control rats implanted with dummy sources, BCNU alone (13.3 mg/kg) produced in an ILS of 67%, and combination treatment with BCNU and implanted 125I sources produced an ILS of 167%. As measured by a colony-forming efficiency assay, the greatest cell kill in 9L spheroids occurred when BCNU was administered 24 hours before irradiation from a 137Cs source at a low dose rate of 5 rad/minute. At a higher dose rate of 210 rad/minute, the time dependence of the effects of combination treatment was identical and therefore independent of dose rate.

Response of the 9L rat brain tumor to combination treatment with radiation and bleomycin

The therapeutic efficacy of combined modality treatment with radiation therapy and bleomycin was investigated in rats burdened with the intracerebral 9L gliosarcoma. Both radiation (single or fractionated exposures) and bleomycin (injected intracerebrally directly into the tumor region) are effective in prolonging survival when used as single agents. Bleomcyin (1.0 mg/kg/week) combined with low-dose radiation therapy (15.3 Gy in 6 fractions in 2 weeks) prolonged survival over that of radiation alone, but not to the extent of high-dose radiation therapy (30.6 Gy in the same schedule). Bleomycin was effective whether given simultaneously or following fractionated radiation therapy-the important factor being delivery of radiation therapy early in the disease process. The greatest enhancement in survival caused by combination therapy compared to that by single agent therapy was observed when single exposure radiation therapy (20 Gy) followed single bleomycin administration by 4 hr. These results suggest the possibility of using bleomycin as an adjunct to radiation therapy for the treatment of patients with malignant brain tumors.