MMP1 and head and neck squamous cell carcinoma: In this review, we will summarize the role of these MMPs that are highly expressed in HNSCCs, especially MMP-1, -3, -7, -9, -10, -12, -13 and -19, and also review the roles of MMP-14, which is one of the key molecules involved in HNSCC progression through invadopodia formation.