The microenvironment induces collective migration in -silenced mouse pheochromocytoma spheroids.

Pheochromocytomas (Pheos) and paragangliomas (PGLs) are neuroendocrine tumors. Approximately 30-40% of Pheos/PGLs are due to germline mutations in one of the susceptibility genes, including those encoding the succinate dehydrogenase subunits A-D (). Up to 2/3 of patients affected by mutated Pheo/PGL develop metastatic disease with no successful cure at present. Here, for the first time, we evaluated the effects of silencing in a three dimension (3D) culture using spheroids of a mouse Pheo cell line silenced or not (wild type/wt/control) for the SDHB subunit. We investigated the role of the microenvironment on spheroid growth and migration/invasion by co-culturing -silenced or wt spheroids with primary cancer-activated fibroblasts (CAFs). When spheroids were co-cultured with fibroblasts, -silenced cells showed a significant increase in matrigel invasion as demonstrated by the computation of the migratory areas ( < 0.001). Moreover, cells detaching from the -silenced spheroids moved collectively, unlike the cells of wt spheroids that moved individually. Additionally, silenced spheroids developed long filamentous formations along which clusters of cells migrated far away from the spheroid, whereas these structures were not present in wt spheroids. We found that lactate, largely secreted by CAFs, plays a specific role in promoting migration only of -silenced cells. In this study, we demonstrated that silencing increases tumor cell migration/invasion and that microenvironment, as represented by CAFs, plays a pivotal role in enhancing collective migration/invasion in Pheo -silenced tumor cells, suggesting their role in increasing the tumor metastasizing potential.