KLK6 and head and neck squamous cell carcinoma: In summary, our data demonstrate for the first time that low KLK6 expression serves as unfavorable risk factor for progression-free and overall survival of HNSCC patients, and we provide experimental evidence that KLK6 is a key regulator of tumor cell migration, invasion and response to radiotherapy by modulating EMT and β-catenin signaling (Fig. 6).