HEY1 and head and neck squamous cell carcinoma: Interestingly, siRNA mediated DCLK1 depletion in 3 HNSCC cell lines (JHU-011 JHU-022 and JHU-029) substantially downregulated the expression levels of the NOTCH1 intracellular domain (NICD) and its downstream targets, such as HES1, HES5 and HEY1 (Figure 5A), confirming that NOTCH signaling was functionally inhibited.