PTGS2 and hereditary pheochromocytoma-paraganglioma: 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.