Strain-specific metastatic phenotypes in pheochromocytoma allograft mice

Abstract

Somatostatin receptor-targeting endoradiotherapy offers potential for treating metastatic pheochromocytomas and paragangliomas, an approach likely to benefit from combination radiosensitization therapy. To provide reliable preclinical in vivo models of metastatic disease, this study characterized the metastatic spread of luciferase-expressing mouse pheochromocytoma (MPC) cells in mouse strains with different immunologic conditions. Bioluminescence imaging showed that, in contrast to subcutaneous non-metastatic engraftment of luciferase-expressing MPC cells in NMRI-nude mice, intravenous cell injection provided only suboptimal metastatic spread in both NMRI-nude mice and hairless SCID (SHO) mice. Treatment of NMRI-nude mice with anti-Asialo GM1 serum enhanced metastatic spread due to substantial depletion of natural killer (NK) cells. However, reproducible metastatic spread was only observed in NK cell-defective SCID/beige mice and in hairless immunocompetent SKH1 mice bearing disseminated or liver metastases, respectively. Liquid chromatography tandem mass spectrometry of urine samples showed that subcutaneous and metastasized tumor models exhibit comparable renal monoamine excretion profiles characterized by increasing urinary dopamine, 3-methoxytyramine, norepinephrine and normetanephrine. Metastases-related epinephrine and metanephrine were only detectable in SCID/beige mice. Positron emission tomography and immunohistochemistry revealed that all metastases maintained somatostatin receptor-specific radiotracer uptake and immunoreactivity, respectively. In conclusion, we demonstrate that intravenous injection of luciferase-expressing MPC cells into SCID/beige and SKH1 mice provides reproducible and clinically relevant spread of catecholamine-producing and somatostatin receptor-positive metastases. These standardized preclinical models allow for precise monitoring of disease progression and should facilitate further investigations on theranostic approaches against metastatic pheochromocytomas and paragangliomas.

Advances in paraganglioma–pheochromocytoma cell lines and xenografts

“…While the development of mouse and cell models was originally 'plan A', as in any disease-related field of investigation, over the last two decades this task has proved more challenging than expected and has thus effectively been relegated to 'plan B' status by many groups. Nevertheless, seasoned figures in the field continue their efforts (Powers et al 2017 and others are adapting existing models to new circumstances (Richter et al 2018, Ullrich et al 2018, so research using these models continues and in light of hopeful recent developments from the Tischler/Powers lab, the coming years will hopefully see the introduction of new models from both rodent, and more importantly, human tumor sources. Do we even need a model in a field in which the primary clinical challenge is metastatic SDHB-mutated paraganglioma?…”

“…The MPC and MTT mouse cell lines have formed the basis of a variety of studies, including the investigation of PI3K/ AKT, mTORC1 and RAS/RAF/ERK signaling (Nolting et al 2012), the action of lovastatin and 13-cisretinoic acid (Nolting et al 2014), evaluation of the topoisomerase I inhibitor, LMP-400 (Schovanek et al 2015), and the patterns and reproducibility of metastatic spread (Ullrich et al 2018).…”

“…Overall, the MPC/MTT cell lines and their use in mouse models represent the most relevant pheochromocytoma model system currently available. It has been claimed that an MPC-based model 'provides an appropriate model for pre-clinical investigations on metastatic PPGLs' (Ullrich et al 2018). Although we agree that better alternatives were not yet available at the time, it is important not to lose sight of the serious shortcomings of this model, especially regarding SDHB-related metastatic PPGLs.…”

Targeting Cyclooxygenase-2 in Pheochromocytoma and Paraganglioma: Focus on Genetic Background

“…Mouse pheochromocytoma cells (MPC clone 4/30PRR [48]) were cultivated as previously described [49]. Spheroids were generated from MPC cells passage 34 as described elsewhere [66,67].…”

“…To address the above hypothesis, we evaluated COX-2 status of PPGLs with known mutational status for VHL , SDHx , EPAS1 , NF1 , RET , and HRAS on both mRNA and protein level. Furthermore, we characterized COX-2 immunoreactivity in tumor spheroids and allografts derived from mouse pheochromocytoma (MPC) cells with a heterozygous Nf1 knockout [48,49] in order to assess the usefulness of these models for preclinical testing of COX-2-targeting adjuvant and, in particular, radiosensitizing treatments.…”