Label-free detection of brain tumors in a 9L gliosarcoma rat model using stimulated Raman scattering-spectroscopic optical coherence tomography

SIGNIFICANCE

In neurosurgery, it is essential to differentiate between tumor and healthy brain regions to maximize tumor resection while minimizing damage to vital healthy brain tissue. However, conventional intraoperative imaging tools used to guide neurosurgery are often unable to distinguish tumor margins, particularly in infiltrative tumor regions and low-grade gliomas.

AIM

The aim of this work is to assess the feasibility of a label-free molecular imaging tool called stimulated Raman scattering-spectroscopic optical coherence tomography (SRS-SOCT) to differentiate between healthy brain tissue and tumor based on (1) structural biomarkers derived from the decay rate of signals as a function of depth and (2) molecular biomarkers based on relative differences in lipid and protein composition extracted from the SRS signals.

APPROACH

SRS-SOCT combines the molecular sensitivity of SRS (based on vibrational spectroscopy) with the spatial and spectral multiplexing capabilities of SOCT to enable fast, spatially and spectrally resolved molecular imaging. SRS-SOCT is applied to image a 9L gliosarcoma rat tumor model, a well-characterized model that recapitulates human high-grade gliomas, including high proliferative capability, high vascularization, and infiltration at the margin. Structural and biochemical signatures acquired from SRS-SOCT are extracted to identify healthy and tumor tissues.

RESULTS

Data show that SRS-SOCT provides light-scattering-based signatures that correlate with the presence of tumors, similar to conventional OCT. Further, nonlinear phase changes from the SRS interaction, as measured with SRS-SOCT, provide an additional measure to clearly separate tumor tissue from healthy brain regions. We also show that the nonlinear phase signals in SRS-SOCT provide a signal-to-noise advantage over the nonlinear amplitude signals for identifying tumors.

CONCLUSIONS

SRS-SOCT can distinguish both spatial and spectral features that identify tumor regions in the 9L gliosarcoma rat model. This tool provides fast, label-free, nondestructive, and spatially resolved molecular information that, with future development, can potentially assist in identifying tumor margins in neurosurgery.

A practical method for multimodal registration and assessment of whole-brain disease burden using PET, MRI, and optical imaging

Many neurological diseases present with substantial genetic and phenotypic heterogeneity, making assessment of these diseases challenging. This has led to ineffective treatments, significant morbidity, and high mortality rates for patients with neurological diseases, including brain cancers and neurodegenerative disorders. Improved understanding of this heterogeneity is necessary if more effective treatments are to be developed. We describe a new method to measure phenotypic heterogeneity across the whole rodent brain at multiple spatial scales. The method involves co-registration and localized comparison of in vivo radiologic images (e.g. MRI, PET) with ex vivo optical reporter images (e.g. labeled cells, molecular targets, microvasculature) of optically cleared tissue slices. Ex vivo fluorescent images of optically cleared pathology slices are acquired with a preclinical in vivo optical imaging system across the entire rodent brain in under five minutes, making this methodology practical and feasible for most preclinical imaging labs. The methodology is applied in various examples demonstrating how it might be used to cross-validate and compare in vivo radiologic imaging with ex vivo optical imaging techniques for assessing hypoxia, microvasculature, and tumor growth.

Biological characteristics and outcomes of Gliosarcoma

Gliosarcoma is a highly aggressive primary brain tumour. It is a relatively rare tumour and comprises of two histological components, glial and sarcomatous. Gliosarcomas carry a poorer prognosis than that of Glioblastoma Multiforme (GBM). The current review highlights important histological and radiological features of gliosarcoma in the light of recent literature, and also touches upon the treatment options and outcomes of various types of gliosarcoma.

[A Patient with Primary Intraventricular Gliosarcoma and Long-term Survival - a Case Report]

BACKGROUND

Gliosarcoma is a rare, malignant CNS tumor with a very poor prognosis. Gliosarcoma is a variant of glioblastoma multiforme, which is characterized by the presence of both glial and mesenchymal components. The treatment strategy for gliosarcomas has not yet been determined clearly.

CASE PRESENTATION

This case report presents a 23-year-old female patient who complained of increasing headaches, nausea and vomiting, and slight motor weakness in her left arm. An MRI scan of the brain showed a tumor filling the anterior part of the right lateral ventricle and extending into the right frontal lobe. Tumor extirpation was performed. Histology revealed gliosarcoma. Subsequently, the patient received concomitant chemoradiotherapy with temozolomide in the Stupp regimen. Following the fourth cycle of maintenance temozolomide chemotherapy, at eight months after diagnosis, an MRI scan detected progression of the tumor residue. The patient underwent another surgery and then received 10 cycles of second-line chemotherapy in the ICE (ifosfamide, carboplatin, and etoposide) regimen. She completed oncological therapy with minimal toxicity and follow-up MRI scans showed virtually no residual tumor. Another follow-up MRI scan, performed 28 months after diagnosis, demonstrated progression of the tumor residue again. A third tumor resection was performed 29 months after initial diagnosis. Histology again confirmed gliosarcoma. An early postoperative MRI scan showed subtotal resection with a tumor residue in eloquent areas and also suspected implantation metastasis in the spinal canal at the C2 level. From the neurological perspective, the patient was fully self-sufficient, and had only a very mild motor deficit in her left arm. Currently, at 31 months after initial diagnosis, the patient is in a stable condition and fully self-sufficient.

CONCLUSION

Our case report shows that long-term survival can be achieved in a gliosarcoma patient exhibiting all the unfavorable features in clinical-pathological terms. The minimal recommended treatment is maximal resection followed by adjuvant radiotherapy. Our patient also underwent chemoradiotherapy with temozolomide in the Stupp regimen. Recurrence at eight months after diagnosis was managed by a repeat operation and high-dose combination chemotherapy, which kept the disease in remission for 20 months after the initial relapse. The lack of unequivocal rules for chemotherapy provides an opportunity to test less common treatment regimens.Key words: gliosarcoma - surgery - chemotherapy - radiotherapy - survivalThis study was supported in part by the grant No. NT13581-4/2012(86-91) of the Internal Grant Agency of the Czech Ministry of Health.The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study.The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 26. 3. 2016Accepted: 27. 4. 2016.

Detection of experimentally induced brain tumors in rats using high resolution computed tomography

OBJECTIVE

The feasibility of high resolution CT imaging for evaluating experimentally-induced brain tumors in rats was assessed.

METHODS

The gliosarcoma cell line (9 L/lacZ) was inoculated in 34 male Fischer 344 rats and CT studies were performed prior to and at 4, 7, 9, 12 and 14 days post-tumor cell implantation. Brain imaging pre- and post-contrast was performed and correlated with autopsy findings.

RESULTS

Tumors were identified by CT in 19 of the 34 animals after contrast administration and their presence was confirmed at autopsy. Tumors were present at autopsy and not identified by CT scanning in eight additional animals and in the remaining seven animals, the CT scan was normal and no tumors were present at autopsy. The sensitivity and specificity of CT scanning with contrast in detecting tumors in this rat model of gliosarcoma was 70 and 100%, respectively.

CONCLUSION

The improved CT technology currently available can be used to identify and follow tumor burden in a rat model of gliosarcoma, and be a good tool to utilize in determining treatment outcomes experimentally, especially when MR imaging is not available.

[Utility of 11C-methionine PET/CT in neuro-oncology]

Positron emission tomography (PET) with 11C-methionine (11C-methionine PET/CT) is a new technique used to evaluate primary central nervous system (CNS) tumors. We describe our experience regarding the first 4 patients with glial tumors and 11C-methionine PET/CT. This is a descriptive, observational and prospective study of 4 patients between 38-50 years of age, with different gliomas (WHO classification). MRI and 11C-methionine PET/CT were performed in all cases. Case 1, gliomatosis cerebri grade II post-radiotherapy. Case 2, oligodendroglioma grade II diagnosed and treated with radiotherapy in 1993. Case 3, glioblastoma grade IV post-radiotherapy + temozolomide. Case 4, anaplastic oligoastrocytoma grade III post-radiotherapy + temozolomide. The pattern of 11C-methionine uptake compared with MRI showed tumor progression in cases 1, 3 and 4, and in case 2 showed uptake although the final diagnosis was pseudoprogression. Unlike 18fluordeoxiglucose PET/TC, 11C-methionine uptake in normal brain tissue and pseudoprogression is low, and gliomas are displayed as metabolically active areas. The 11C-methionine PET/CT provided valuable information on the tumoral behavior and extension, although in one case presented did not differentiate tumor progression from pseudoprogression. 11C-methionine PET/CT could be a useful tool in the study and follow-up to patients with gliomas.

Click synthesis and biologic evaluation of (R)- and (S)-2-amino-3-[1-(2-[18F]fluoroethyl)-1H-[1,2,3]triazol-4-yl]propanoic acid for brain tumor imaging with positron emission tomography

The (R)- and (S)-enantiomers of 2-amino-3-[1-(2-[18F]fluoroethyl)-1H-[1,2,3]triazol-4-yl]propanoic acid (4) were synthesized and evaluated in the rat 9L gliosarcoma brain tumor model using cell uptake assays, biodistribution studies, and micro-positron emission tomography (microPET). The (R)- and (S)-enantiomers of [18F]4 were radiolabeled separately using the click reaction in 57% and 51% decay-corrected yields, respectively. (S)-[18F]4 was a substrate for cationic amino acid transport and, to a lesser extent, system L transport in vitro. In vivo biodistribution studies demonstrated that (S)-[18F]4 provided higher tumor uptake and higher tumor to brain ratios (15:1 at the 30- and 60-minute time points) compared to the (R)-enantiomer (7:1 at the 30- and 60-minute time points). MicroPET studies with (S)-[18F]4 confirmed that this tracer provides good target to background ratios for both subcutaneous and intracranial 9L gliosarcoma tumors. Based on these results, the 1H-[1,2,3]triazole-substituted amino acid (S)-[18F]4 has promising PET properties for brain tumors and represents a novel class of radiolabeled amino acids for tumor imaging.

Gliosarcoma with osteosarcomatous features: a short illustrated review

INTRODUCTION

Gliosarcoma is a rare, malignant, biphasic brain tumor formed by both glioblastoma and sarcomatous components. Various lines of differentiation are described in the latter component, but most commonly fibrosarcomatous and pleomorphic sarcoma are present. Osteosarcomatous features are exceedingly rare.

OBJECTIVE

We report a case of gliosarcoma with osteosarcomatous features in a 33-year-old woman.

METHODS

Histologically, the sarcomatous portion displayed a typical pattern of fibrosarcoma associated with areas of osteoid formation.

RESULTS AND CONCLUSION

Immunohistochemical glial fibrillary acid protein (GFAP) expression was seen only in the glioblastoma portion. Clinicopathological characteristics and radiological data of this rare condition were reviewed. Possible differential diagnoses and potential histogenesis were also discussed.

Synthesis and evaluation of [123I] labeled iodovinyl amino acids syn-, anti-1-amino-3-[2-iodoethenyl]-cyclobutane-1-carboxylic acid, and 1-amino-3-iodomethylene-cyclobutane-1-carboxylic acid as potential SPECT brain tumor imaging agents

syn- and anti-1-amino-3-[2-iodoethenyl]-cyclobutane-1-carboxylic acid (syn-, anti-IVACBC 16, 17) and their analogue 1-amino-3-iodomethylene-cyclobutane-1-carboxylic acid (gem-IVACBC 18) were synthesized and radioiodoinated with [(123)I] in 34-43% delay-corrected yield. All these amino acids entered 9L gliosarcoma cells primarily via L-type transport in vitro with high uptake of 8-10% ID/1 x 10(6) cells. Biodistribution studies of [(123)I]16, 17 and 18 in rats with 9L gliosarcoma brain tumors demonstrated high tumor to brain ratios (4.7-7.3:1 at 60 min post-injection). In this model, syn-, anti-, and gem-[(123)I]IVACBC are promising radiotracers for SPECT brain tumor imaging.

Gliosarcoma With Features of Osteoblastic Osteosarcoma: A Review

Context.—Gliosarcoma is a rare tumor of the central nervous system characterized by a biphasic histologic pattern, consisting of a gliomatous and a sarcomatous component, respectively. In most instances the sarcomatous component is represented by a fibrosarcoma, but other stromal malignancies have also been described. Osteosarcomatous differentiation in gliosarcoma has been rarely reported.

Objective.—To review characteristic radiologic and histopathologic features of this rare neoplasm, to debate about possible differential diagnoses that should be taken into consideration, and to provide an overview of the potential histopathogenesis of gliosarcomas.

Data Sources.—Relevant articles indexed in PubMed (National Library of Medicine) and reference medical texts.

Conclusions.—Recent molecular studies suggest that sarcomatous and gliomatous components of gliosarcoma might be derived from a single precursor cell clone, progressing in 2 subclones with distinct morphologic features during tumor evolution. Nonetheless, events determining splitting of the original clone into 2 histologic populations remain to be investigated.

Application of arsenazo III in the preparation and characterization of an albumin-linked, gadolinium-based macromolecular magnetic resonance contrast agent

A macromolecular magnetic resonance contrast agent (MMCA) was prepared by linking bovine serum albumin (BSA) to gadolinium (Gd) via a chelating agent, diethylenetriaminepentaacetic acid (DTPA). Colorimetric testing with 2,7-bis(o-arsenophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (arsenazo III) was performed to check for the appearance of free gadolinium during preparation and to quantify the Gd content in the final product. The complex was purified by dialysis, concentrated by lyophilyzation and characterized by magnetic resonance (MR) proton relaxation times. The resultant product had a molecular weight of about 90 kDa, Gd:BSA ratio of 14:1, and T1 and T2 relaxation times of 128.3 and 48.9 ms, respectively, at a field strength of 7Tesla (T) and at 20% concentration. Contrast enhancement of Gadomer-17 (a dendritic MMCA) and Gd-linked to BSA (Gd-BSA) was sequentially evaluated in a rat brain gliosarcoma model (n = 5) by MR imaging (MRI). Following intravenous injection, the blood concentration of Gadomer-17 fell rapidly, whereas that of Gd-BSA was almost constant for the duration of imaging. The areas of enhancement of both MMCAs were comparable. The spatial distribution of Gd-BSA showed good agreement with Evans blue-tagged albumin. Treatment with dexamethasone decreased Gd-BSA enhancement in the tumor. These results suggest that the arsenazo III method is applicable in preparing Gd-BSA to image brain tumors and their response to treatment. This simple method may also be useful for preparing other gadolinium-linked MMCAs.

Reirradiation of recurrent high-grade gliomas using amino acid PET (SPECT)/CT/MRI image fusion to determine gross tumor volume for stereotactic fractionated radiotherapy

PURPOSE

To develop a valid treatment strategy for recurrent high-grade gliomas using stereotactic hypofractionated reirradiation based on biologic imaging and temozolomide.

PATIENTS AND METHODS

The trial included a total of 44 patients with recurrent high-grade gliomas (1 patient with anaplastic oligodendroglioma, 8 with anaplastic astrocytoma, 33 with glioblastoma multiforme, and 2 with gliosarcoma) after previous surgery and postoperative conventional radiotherapy +/- chemotherapy. For fractionated stereotactic radiotherapy (SFRT) treatment planning, the gross tumor volume was defined by (11)C-methionine positron emission tomography (MET-PET) or (123)I-alpha-methyl-tyrosine (IMT) single-photon computed emission tomography (SPECT)/computed tomography (CT)/magnetic resonance imaging (MRI) fusion in 82% of the patients and by CT/T1+gadolinium-MRI image fusion in 18% of the patients. Six fractions of 5 Gy were administered in 6 days. In 29 of 44 patients (66%), chemotherapy with temozolomide (200 mg/m(2) body surface/day) was given in one to two cycles before and four to five cycles after SFRT. The patients were evaluated in follow-up by clinical investigators and MRI or CT every 3 months after SFRT until death. In cases suspicious for radiation necrosis, a MET-PET or IMT-SPECT investigation was performed.

RESULTS

The median survival time in the whole group was 8 months. Treatment planning based on PET(SPECT)/CT/MRI imaging was associated with improved survival in comparison to treatment planning using CT/MRI alone: median survival time 9 months vs. 5 months (p = 0.03, log-rank). Median survival time were 11 months for patients who received SFRT based on biologic imaging plus temozolomide and significantly lower, 6 months for patients treated with SFRT without biologic imaging, without temozolomide or without both (p = 0.008, log rank). The most important prognostic factor in univariate analysis was a long interval between initial diagnosis and recurrence (p = 0.0002, log-rank). In the multivariate model, time interval to retreatment (p = 0.006) and temozolomide (p = 0.04) remained statistically significant. No acute neurologic toxicity Grade 3 or higher and no Grade 4 hematologic toxicity was observed.

CONCLUSION

This is the first study of biologic imaging optimized SFRT plus temozolomide in recurrent high-grade gliomas. It demonstrates the feasibility and safety of this approach. The most striking result of the trial is the statistically significant longer survival time in the univariate analysis for patients reirradiated using MET-PET or IMT-SPECT/CT/MRI image fusion in the treatment planning, in comparison to patients treated based on MRI/CT alone. Multivariate analysis confirmed a significant survival benefit from multimodal treatment (i.e., addition of temozolomide), despite the limited number of patients. Whether treatment planning with SPECT/PET independently influences survival has to be studied in a larger series of patients.

A novel brainstem tumor model: guide screw technology with functional, radiological, and histopathological characterization

OBJECT

Survival rates for high-grade brainstem tumors are approximately 10% and optimal therapy has yet to be determined. Development of a satisfactory brainstem tumor model is necessary for testing new therapeutic paradigms that may prolong survival. The authors report the technique, functional progression, radiological appearance, and histopathological features of a novel brainstem tumor model in rats.

METHODS

Thirty female Fischer 344 rats were randomized (10 animals/group) to receive an injection of either 3 ml of 9L gliosarcoma cells (100,000 cells), 3 ml of F98 glioma cells (100,000 cells), or 3 ml of medium (Dulbecco modified Eagle medium) into the pontine tegmentum of the brainstem. Using a cannulated guide screw system implanted in the skull of the animal, rats in each group were injected at coordinates 1.4 mm to the right of the sagittal and 1 mm anterior to the lambdoid sutures, at a depth of 7 mm from the dura mater. The angle of the syringe during injection was anteflexed 5 degrees from the vertical. Postoperatively, the rats were evaluated for neurological deficits by using an automated rotarod test. High-resolution [18F]fluorodeoxyglucose-positron emission tomography (FDG-PET) fused with computerized tomography (CT) scans were acquired pre- and postoperatively through the onset of hemiparesis and correlated accordingly. Kaplan-Meier curves were generated for survival and disease progression, and brains were processed postmortem for histopathological investigation. The 9L and F98 tumor cells grew in 95% of the animals in which they were injected and resulted in a statistically significant mean onset of hemiparesis of 16.5 6 0.56 days (p = 0.001, log-rank test), compared with animals in the control group, which had no neurological deficits by Day 45. The FDG-PET studies coregistered with CT scans demonstrated space-occupying brainstem lesions, and this finding was confirmed by histological studies. Animals in the control group showed no functional, radiological, or pathological signs of tumor.

CONCLUSIONS

Progression to hemiparesis was consistent in all tumor-injected animals, with predictable onset of symptoms occurring approximately 17 days postsurgery. The histopathological and radiological characteristics of the 9L and F98 brainstem tumors were comparable to those of aggressive primary human brainstem tumors. Establishment of this animal tumor model will facilitate the testing of new therapeutic paradigms for the treatment of these lesions.

Image-Guided Robotic Radiosurgery in a Rat Glioma Model

Despite the proven efficacy of radiosurgery for the treatment of brain tumors, limited histological information is available after treatment that might allow a better understanding of the relationship between radiation dose, the volume treated, and the response of the surrounding brain to the delivered radiation. The use of an animal model could provide the opportunity to clarify these relationships and answer several other key questions arising in clinical practice. We show here that treatment of small animals with radiosurgery is feasible using a robotically controlled linear accelerator, which offers the advantages of radiosurgery and preserves the potential for fractionated regimens without rigid immobilization. Specifically, we demonstrate the use of a robotically driven linear accelerator to provide radiosurgical treatment to a rat brain tumor model.

Gliosarcoma with osteosarcomatous differentiation: review of radiological and pathological features

Gliosarcoma is a rare tumor of the central nervous system, consisting of gliomatous and sarcomatous elements. We present an unusual case of gliosarcoma which demonstrated a variation in phenotype over a six month period, changing from a gliosarcoma with osteosarcomatous differentiation, to a gliosarcoma with no osteosarcomatous component. The initial histological diagnosis was glioblastoma multiforme. Fifteen months later the tumor had transformed into a gliosarcoma demonstrating osteosarcomatous differentiation, with the majority of the tumor consisting of osteoid matrix. Further samples taken six months later revealed gliosarcoma with almost no osteosarcomatous component. It is recognized that glioblastoma can undergo a change in phenotype, transforming into a gliosarcoma. This case demonstrates that ongoing changes in phenotype can occur, especially when the tumor has been treated with chemotherapy and radiotherapy. An understanding of the pathological progression of gliosarcoma will become increasingly important as novel treatments for gliosarcoma and glioblastoma become available.

Synthesis and evaluation of 2-amino-4-[(18)F]fluoro-2-methylbutanoic acid (FAMB): relationship of amino acid transport to tumor imaging properties of branched fluorinated amino acids

Radiolabeled amino acids represent a promising class of tumor imaging agents, and the determination of the optimal characteristics of these tracers remains an area of active investigation. A new (18)F-labeled branched amino acid, 2-amino-4-[(18)F]fluoro-2-methylbutanoic acid (FAMB), has been prepared in 36% decay-corrected yield using no-carrier-added [(18)F]fluoride. In vitro uptake assays with rat 9L gliosarcoma cells suggest that [(18)F]FAMB was transported primarily via the L type amino acid transport system. In vivo studies with [(18)F]FAMB demonstrated tumor to normal brain ratios of 14:1 in rats with intracranial 9L gliosarcoma tumors at 60 minutes after injection. Comparison of [(18)F]FAMB with structurally related (18)F-labeled branched amino acids demonstrated that A type transport in vitro was positively correlated with the tumor to brain ratios observed in vivo.

A case of gliosarcoma appearing as ischaemic stroke

OBJECTIVES

Ischaemic stroke attributable to malignant brain tumour is a rarely reported phenomenon and even various imaging techniques including angiography do not necessarily lead to an accurate diagnosis.

CASE DESCRIPTION

A 46-year-old, previously healthy man developed apoplectic symptoms with slight right sided hemiparesis and global aphasia. The computed tomography (CT) scan showed lesions of the left temporal lobe and the paraventricular white matter suggestive of left middle cerebral artery (MCA) infarction. Carotid angiography demonstrated compression of the M1 segment of the MCA and occlusion of temporal MCA. The patient initially refused magnetic resonance imaging (MRI) because of claustrophobia. Because of fluctuating symptoms and successive worsening of the condition over weeks an MRI scan was conducted under general anaesthesia. Beneath temporal, opercular, and subcortical infarctions it revealed a left temporal tumour. A tumour biopsy disclosed a gliosarcoma (WHO grade IV). Microscopical examination of the surgical specimen demonstrated invasion of tumour cells into the wall of a greater pre-existing blood vessel.

CONCLUSIONS

Malignant brain tumours may cause ischaemic infarction. This is a rare but important differential diagnosis for the origin of strokes. The authors describe the first case with infiltration of intracranial blood vessels by tumour cells of a gliosarcoma.

Postradiation gliosarcoma with osteosarcomatous components

A 49-year-old man developed a gliosarcoma with prominent osteoid components 15 months after surgical resection and postoperative radiation and chemotherapy for a right frontal glioblastoma multiforme. The recurrent tumor was distinguished from the original lesion by the presence of dense ossification, visible on CT, at the original tumor site. The relevant literature is reviewed.

Tumor uptake of copper-diacetyl-bis(N(4)-methylthiosemicarbazone): effect of changes in tissue oxygenation

We showed previously that, in vitro, copper-diacetyl-bis(N(4)-methylthiosemicarbazone) (Cu-ATSM) uptake is dependent on the oxygen concentration (pO2). We also showed that, in vivo, Cu-ATSM uptake is heterogeneous in animal tumors known to contain hypoxic fractions. This study was undertaken to confirm the pO2 dependence of this selective uptake in vivo by correlating Cu-ATSM uptake with measured tumor pO2.

METHODS

Experiments were performed with the 9L gliosarcoma rat model using a needle oxygen electrode to measure tissue pO2. Using PET and electronic autoradiography, Cu-ATSM uptake was measured in tumor tissue under various pO2 levels. The oxygen concentration within implanted tumors was manipulated by chemical means or by altering the inhaled oxygen content.

RESULTS

A good correlation between low pO2 and high Cu-ATSM accumulation was observed. Hydralazine administration in animals caused a decrease in the average tumor pO2 from 28.61 +/- 8.74 mm Hg to 20.81 +/- 7.54 mm Hg in untreated control animals breathing atmospheric oxygen. It also caused the tumor uptake of Cu-ATSM to increase by 35%. Conversely, in animals breathing 100% oxygen, the average tumor pO2 increased to 45.88 +/-15.9 mm Hg, and the tumor uptake of Cu-ATSM decreased to 48% of that of the control animals. PET of animals treated in a similar fashion yielded time-activity curves showing significantly higher retention of the tracer in hypoxic tissues than in oxygenated tissues.

CONCLUSION

These data confirm that Cu-ATSM uptake in tissues in vivo is dependent on the tissue pO2, and that significantly greater uptake and retention occur in hypoxic tumor tissue. Therefore, the possible use of Cu-ATSM PET as a prognostic indicator in the management of cancer is further validated.

Gliosarcoma with thallium-201 SPECT

Thallium-201 (201Tl) chloride scintigraphy is the imaging method use for the detection of various tumors including glioblastoma, but only limited information on 201Tl uptake in gliosarcoma is available. We investigated a patient with gliosarcoma by means of 201Tl single-photon emission computed tomography (SPECT) and MRI. SPECT imaging revealed high 201Tl uptake in the tumor, which was closely correlated with contrast-enhancement on MRI. These results suggest that SPECT with 201Tl may be useful for detecting gliosarcoma and provide physiological information on this tumor.

Ultrasound enhancement of liposome-mediated cell transfection is caused by cavitation effects

Cationic liposomes (CL) are widely used vectors for gene transfer. Recently, ultrasound (US) was reported to enhance liposome-mediated gene transfer to eucaryotic cells in culture. The present study was aimed at studying the effects of 2-MHz pulsed Doppler US on malignant brain tumor cells transfection by cationic liposome/plasmid-DNA complexes (lipoplexes). Cationic liposomes consisting of DOSPA/DOPE were complexed with a plasmid carrying the cDNA encoding green autofluorescent protein (EGFP). Rodent (9L) and canine (J3T) glioma cells were exposed to pulsed US in the presence of EGFP-lipoplexes. A diagnostic transcranial Doppler device (MultiDop L) was used for insonation for 30, 60, and 90 s at 2 MHz/0.5 W/cm(2). To eliminate US reflection and cavitation, a custom-made absorption chamber was designed, where US is applied through a water tank before interacting with the cells and is fully absorbed after passing through the cell layer. Expression of the marker gene EGFP was quantified by FACS analysis and intravital fluorescent microscopy. Cell viability was accessed by Trypan Blue staining. US treatment of tumor cells on microplates for 60 s yielded a significant increase in transfection rates without damaging the cells, but 90-s treatment killed most of the cells. In the absorption chamber, no significant effects of US on transfection were noted. Additional experiments employed US contrast agent (Levovist, Schering) which was able to significantly increase tumor cell transfection rate by enhancing cavitation effects, and also severely damaged most cells when applied at a concentration of 200 mg/mL. In conclusion, our results support the assumption that US effects on lipoplex transfection rates in brain tumor cells in culture are mediated by cavitation effects.

Enhanced uptake of [11C]TPMP in canine brain tumor: a PET study

In vitro studies have demonstrated the membrane potential-dependent enhanced uptake of phosphonium salts, including [3H]triphenylmethylphosphonium (TPMP), into mitochondria of carcinoma and glioma-derived tumor cells, suggesting the potential use of phosphonium salts as tracers for tumor imaging. This study characterizes the in vivo uptake of [11C]TPMP in canine brain glioma using PET.

METHODS

Dynamic paired PET studies of [11C]TPMP followed by [68Ga]ethylenediaminetetraacetic acid (EDTA) were performed 4 d before and 9 d after tumor cell inoculation. Graphical analysis was used to evaluate [11C]TPMP retention in tumor tissue. Distribution of tracer uptake was compared with tumor histological sections.

RESULTS

[11C]TPMP exhibited enhanced uptake and prolonged retention in tumor cells. Patlak plot was linear over the 20- to 95-min postinjection period (r = 0.97 +/- 0.1). [68Ga]EDTA exhibited a gradual washout from the tumor tissue. The tumor-to-normal brain uptake ratio at 55 to 95 min postinjection was 47.5 for [11C]TPMP and 8.1 for [68Ga]EDTA. Qualitative comparison with histological sections indicated that [11C]TPMP enhanced uptake was restricted to the tumor area.

CONCLUSION

The enhanced uptake and prolonged retention in tumor suggest [11C]TPMP as a promising means for imaging of gliomas in dogs. The need for studies in humans is indicated.

Bystander effect-mediated therapy of experimental brain tumor by genetically engineered tumor cells

Transfer of the herpes simplex virus-thymidine kinase (HSV-tk) gene, followed by administration of ganciclovir (GCV), generates the "bystander effect," in which HSV-tk-negative wild-type cells, as well as HSV-tk-expressing cells, are killed by GCV. To eradicate an intracranial tumor by this bystander effect, we injected the tumor cells transduced with the HSV-tk gene (TK cells) in the vicinity of the preimplanted wild-type tumor and then administered GCV. Wild-type 9L-gliosarcoma cells (1 x 10[5]) were implanted into the brain of syngeneic Fisher rats. On the next day, rats were injected with TK cells (1 x 10(5) or 3 x 10[5]) or medium alone at the same brain coordinate and then treated with GCV or saline. Administration of GCV significantly prolonged the survival of the rats injected with TK cells compared with that injected with medium alone (p < 0.01). Reduction in tumor size and retardation of tumor growth were observed by serial magnetic resonance imaging in the rats that received the combination of TK cells and GCV. The results show that the bystander effect is also achieved in vivo even when TK cells and wild-type cells are not simultaneously implanted. This treatment modality circumvents potential risks accompanied with in vivo gene transfer. Because there remained substantially no HSV-tk-positive cells in the recurrent tumors, this modality offers a "safe" therapeutic strategy against human malignant gliomas.

Comparison of uptake of 99mTc-alkylisonitriles in the rat 9L gliosarcoma tumor model

The accumulation of three 99mTc(I) alkyl isonitriles was compared in vitro and in vivo using 9L gliosarcoma cells. In vitro, the uptake of 99mTc-EIBI and 99mTc-EPI was higher than that of 99mTc-MIBI. In vivo, however, there was no difference in the tumor concentration at 15 or 60 min postinjection and only a small difference at 24 h. The differences in uptake observed in vitro are apparently offset in vivo by differences in delivery of the tracers to the tumor.

The effect of thymidine kinase transduction and ganciclovir therapy on tumor vasculature and growth of 9L gliomas in rats

Eradication of malignant brain tumors by in situ intratumoral, retrovirally mediated transfer of the herpes simplex virus thymidine kinase (HSVtk) gene, which sensitizes the tumor cells to ganciclovir, has recently been demonstrated in animal models. The observation that tumors studied in vitro and in animals can be completely eliminated despite only partial transduction of the tumor suggests a bystander mechanism that affects nontransduced tumor cells. Such a bystander effect is not completely understood and may represent a combination of several factors that lead to tumor eradication. Endothelial cells of the tumor blood vessels were shown to occasionally integrate the retroviral vector and thus become sensitized to ganciclovir. In the presence of vector-producer cells, which continuously release infectious viral particles, diffuse multifocal hemorrhages occurred during ganciclovir administration. When the tumor was composed of cells that had been transduced with the thymidine kinase gene before inoculation, no infectious viral particles were present within the tumor, no transduction of endothelial cells occurred, and no hemorrhages were observed during ganciclovir therapy. These observations suggest that tumor regression may be due, in part, to destruction of in vivo HSVtk-transduced endothelial cells after exposure to ganciclovir, resulting in tumor ischemia as one possible bystander mechanism. The authors investigated this hypothesis using the subcutaneous 9L gliosarcoma tumor model in Fischer rats. The tumors were evaluated with Doppler color-flow and ultrasound imaging during the various phases of the study. Twenty rats received intratumoral injections of HSVtk retroviral vector-producer cells (6 x 10(7) cells/ml) 21 days after bilateral flank tumor inoculation. Ten rats were subsequently treated with intraperitoneal ganciclovir (15 mg/kg/ml twice a day) for 14 days starting on Day 7 after producer cell injection; 10 control rats received intraperitoneal saline injections (1 ml twice a day) instead of ganciclovir. Ultrasound and flow images were obtained before cell injection, before and during ganciclovir or saline administration, and after cessation of treatment. The number, location, and ultrasonographic appearance of tumor vessels and the tumor volumes were recorded. The number of blood vessels in the tumors increased over time in both groups before treatment. Intratumoral cell injection without ganciclovir administration did not influence tumor growth or intratumoral vasculature. However, tumor vasculature decreased after initiation of ganciclovir therapy in the HSVtk-transduced tumors (p < 0.05). Early patchy or diffuse necrotic changes associated with ultrasonographic evidence of scattered intratumoral hemorrhage occurred in tumors treated with ganciclovir.(ABSTRACT TRUNCATED AT 400 WORDS)

Linear contrast enhancement at the operative site on early post-operative CT after removal of brain tumors

It is unclear whether a linear contrast enhancement at the edges of the operative site on early CT scan indicates a residual tumor or rather reflects postoperative changes. We have studied 15 patients treated with surgical removal of malignant brain tumor, submitted to periodic CT scan. The enhancement of linear contrast was due to a residual tumor, when seen on very early CT scan (within 24 hours after surgery). If occurring later, this enhancement was either generated by a residual tumor or by post-operative changes.

Unusual evolution and computerized tomographic appearance of a gliosarcoma

A patient with a remote infarct, seizures, mild hemiparesis, and dysphasia became obtunded over four months and died. Computerized tomography (CT) over 5 years showed a consistent, large, wedge-shaped left hemisphere hypodensity with a central calcification, but without signs of mass effect. This was interpreted as an infarct of the left middle cerebral artery territory. Post-mortem examination of the brain revealed the entire area appearing as infarct on CT was a gliosarcoma. We suspect that the unusual CT appearance of the lesion was likely caused by multiple pathologies: a low grade glioma transforming into a gliosarcoma that was able to spread throughout the area of infarct encephalomalacia without revealing a typical CT appearance of mass effect. The patient's brief period of deterioration probably coincided with transformation of the tumor into a gliosarcoma. The variable CT characteristics of gliosarcomas are reviewed.