Characterization of the 9L gliosarcoma implanted in the Fischer rat: an orthotopic model for a grade IV brain tumor

Abstract

Among rodent models for brain tumors, the 9L gliosarcoma is one of the most widely used. Our 9L-European Synchrotron Radiation Facility (ESRF) model was developed from cells acquired at the Brookhaven National Laboratory (NY, USA) in 1997 and implanted in the right caudate nucleus of syngeneic Fisher rats. It has been largely used by the user community of the ESRF during the last decade, for imaging, radiotherapy, and chemotherapy, including innovative treatments based on particular irradiation techniques and/or use of new drugs. This work presents a detailed study of its characteristics, assessed by magnetic resonance imaging (MRI), histology, immunohistochemistry, and cytogenetic analysis. The data used for this work were from rats sampled in six experiments carried out over a 3-year period in our lab (total number of rats = 142). The 9L-ESRF tumors were induced by a stereotactic inoculation of 10(4) 9L cells in the right caudate nucleus of the brain. The assessment of vascular parameters was performed by MRI (blood volume fraction and vascular size index) and by immunostaining of vessels (rat endothelial cell antigen-1 and type IV collagen). Immunohistochemistry and regular histology were used to describe features such as tumor cell infiltration, necrosis area, nuclear pleomorphism, cellularity, mitotic characteristics, leukocytic infiltration, proliferation, and inflammation. Moreover, for each of the six experiments, the survival of the animals was assessed and related to the tumor growth observed by MRI or histology. Additionally, the cytogenetic status of the 9L cells used at ESRF lab was investigated by comparative genomics hybridization analysis. Finally, the response of the 9L-ESRF tumor to radiotherapy was estimated by plotting the survival curves after irradiation. The median survival time of 9L-ESRF tumor-bearing rats was highly reproducible (19-20 days). The 9L-ESRF tumors presented a quasi-exponential growth, were highly vascularized with a high cellular density and a high proliferative index, accompanied by signs of inflammatory responses. We also report an infiltrative pattern which is poorly observed on conventional 9 L tumor. The 9L-ESRF cells presented some cytogenetic specificities such as altered regions including CDK4, CDKN2A, CDKN2B, and MDM2 genes. Finally, the lifespan of 9L-ESRF tumor-bearing rats was enhanced up to 28, 35, and 45 days for single doses of 10, 20, and 2 × 20 Gy, respectively. First, this report describes an animal model that is used worldwide. Second, we describe few features typical of our model if compared to other 9L models worldwide. Altogether, the 9L-ESRF tumor model presents characteristics close to the human high-grade gliomas such as high proliferative capability, high vascularization and a high infiltrative pattern. Its response to radiotherapy demonstrates its potential as a tool for innovative radiotherapy protocols.

MR Vascular Fingerprinting in Stroke and Brain Tumors Models

“…Three different rat models of brain tumors (9 L, C6, F98) known to contain irregular microvascular architectures121314 were analyzed. We also studied a stroke model in which the geometry of blood vessels is less affected but blood flow and blood oxygenation have large variations4.…”

Ultrasmall theranostic gadolinium-based nanoparticles improve high-grade rat glioma survival

“…The 9L glioma (9LGS) cells were implanted in the brain of male 10-week-old Fisher 344 rats (Charles River, France) [27,28]. Anesthetized animals were placed on a stereotactic frame, and 10 4 9LGS cells suspended in 1 mL DMEM + 1% penicillin/streptomycin were pushed manually within 30 s using a Hamilton syringe inserted into the right caudate nucleus (3.5 mm lateral to the bregma, 6 mm depth below the skull surface).…”

Microbeam radiation therapy: Clinical perspectives

“…These characteristics of MRT have been extensively demonstrated by results of preclinical experiments [12,17]. Furthermore, MRT-associated bystander effects have been identified [18e21].…”

“…Furthermore, potentially antioncogenic apoptotic proteomic changes indicate that the collective interaction of such MB irradiation-induced bystander effect proteins might confer a protective effect on normal tissues [20]. (6) Transcriptional gene expression analysis of intracerebral gliosarcomas in rats [12,29] and EM6.5 breast tumours in mice [30] have identified MRT induced immunity-related modulations, clearly different from transcriptional changes induced by unsegmented broad beams.…”