Pathologic correlates of primary central nervous system lymphoma defined in an orthotopic xenograft model.

PURPOSE: The prospect for advances in the treatment of patients with primary central nervous system lymphoma (PCNSL) is likely dependent on the systematic evaluation of its pathobiology. Animal models of PCNSL are needed to facilitate the analysis of its molecular pathogenesis and for the efficient evaluation of novel therapeutics. EXPERIMENTAL DESIGN: We characterized the molecular pathology of CNS lymphoma tumors generated by the intracerebral implantation of Raji B lymphoma cells in athymic mice. Lymphoma cells were modified for bioluminescence imaging to facilitate monitoring of tumor growth and response to therapy. In parallel, we identified molecular features of lymphoma xenograft histopathology that are evident in human PCNSL specimens. RESULTS: Intracerebral Raji tumors were determined to faithfully reflect the molecular pathogenesis of PCNSL, including the predominant immunophenotypic state of differentiation of lymphoma cells and their reactive microenvironment. We show the expression of interleukin-4 by Raji and other B lymphoma cell lines in vitro and by Raji tumors in vivo and provide evidence for a role of this cytokine in the M2 polarization of lymphoma macrophages both in the murine model and in diagnostic specimens of human PCNSL. CONCLUSION: Intracerebral implantation of Raji cells results in a reproducible and invasive xenograft model, which recapitulates the histopathology and molecular features of PCNSL, and is suitable for preclinical testing of novel agents. We also show for the first time the feasibility and accuracy of tumor bioluminescence in the monitoring of a highly infiltrative brain tumor.

Bioluminescence imaging of invasive intracranial xenografts: implications for translational research and targeted therapeutics of brain tumors.

Despite decades of study, the etiology of brain cancer remains elusive. However, extensive molecular characterization of primary brain tumors has been accomplished, outlining recurrent features that are proving useful for devising targeted therapies. There are far too few patients available for comparing the efficacy of therapeutic combinations, especially when variations in dosing, frequency, and sequencing are taken into account. Consequently, there is a substantial need for increasing preclinical testing throughput using clinically relevant models. We review luminescent optical imaging for its potential in facilitating in vivo assessment of intracranial tumor growth and response to therapy in rodent orthotopic xenograft models of primary brain malignancies. We review the rationale behind the need of an in vivo model, why orthotopic tumor models displaying an invasive phenotype may be a superior choice when compared to flank-implanted tumors, and what advantages may be drawn from the use of modified cells, suitable for sequential monitoring by in vivo optical imaging. Studies show that luminescent signal correlates highly both with tumor burden and Kaplan-Meier survival curves of rodents bearing intracranial xenografts. We conclude that bioluminescent imaging is a highly sensitive technique for assessment of tumor burden, response to therapy, tumor recurrence, and behavior to salvage therapy, making it a superior option for longitudinal monitoring in intracranial rodent models of primary brain tumors.

Bioluminescence monitoring of intracranial glioblastoma xenograft: response to primary and salvage temozolomide therapy.

OBJECT: Bioluminescence imaging (BLI) offers a rapid and accurate means for longitudinal study of tumor cell growth and response to therapy in rodent models. Because this technology has only recently come into use in the field of small animal imaging, applications in this area have been limited. In the current study we have applied BLI to the analysis of clinically relevant issues involving use of the DNA methylating agent temozolomide (TMZ) in a mouse model. METHODS: An invasive glioblastoma multiforme xenograft was modified for BLI via transduction with a luciferase-encoding lentivirus. Supratentorial tumors were established in athymic nude mice that were subsequently assigned randomly to control and TMZ treatment groups, and the extent of intracranial tumor was monitored using BLI. RESULTS: In an experiment designed to compare the extent of antitumor effect between a single high-dose TMZ treatment and a protracted low-dose TMZ regimen, BLI revealed the protracted regimen as having superior antitumor effect, and this interpretation was consistent with results from a survival comparison between the two TMZ treatment groups. In a second experiment designed to assess the utility of BLI for testing therapies against recurrent glioblastoma multiforme, mice with intracranial tumors were retreated with TMZ at a time when BLI monitoring revealed tumor regrowth following initial TMZ treatment, and retreatment was successful in providing additional survival benefit. CONCLUSIONS: The results of these experiments indicate that BLI monitoring can be used as a surrogate for predicting survival benefit from TMZ treatment, permits early determination of relative survival benefit associated with distinct TMZ therapeutic regimens, and offers a means of investigating secondary/salvage therapy efficacy following tumor regrowth from initial therapy.