SDHB and cancer: For instance, a heterotypic spheroid model (combined of pheochromocytoma cells and primary cancer-associated fibroblasts (CAFs)) was used to test the differential response of wild-type and SDHB/SDHD knock-down pheochromocytoma cells to the pro-migratory factors released by CAFs.59 To be noted, the 3D heterotypic spheroids displayed increased tumorigenic potential in terms of migratory capabilities compared to that of 3D homotypic cancer spheroids.