PI3K/Akt signaling is also essential for anchorage-independent growth in rat fibroblasts expressing RET-MEN2A (71); RET-MEN2A germline mutations are responsible for MEN2A, which leads to pheochromocytoma in approximately 50% of patients – therefore these results suggest that this pathway may be critical in tumorigenesis in these patients. This evidence concerns the gene PIK3CA and pheochromocytoma.