EPCAM and head and neck squamous cell carcinoma: To further confirm whether circFAT1 controlled the tumorigenic potential of CSCs, we isolated CSCs from HNSCC patient‐derived xenograft (PDX) using EpCAM+ALDHhigh markers as described previously.[14] Consistently, qRT‐PCR found that circFAT1 was higher in EpCAM+ALDHhigh CSCs than in EpCAM+ALDHlow nonstem tumor cells (Figure 3H).