SOX2 and head and neck squamous cell carcinoma: The transcription factor STAT3 is the primary signaling molecule in the JAK/STAT3 pathway, and the activation of STAT3 is associated with CSCs in HNSCC,[16, 17] Western blot showed that the knockdown of STAT3 by shRNA drastically reduced the level of STAT3 and phospho‐STAT3 (Tyr705) (pSTAT3) and inhibited the expression of SOX2 in SCC23 and SCC1 cells (Figure 4B).