MMP9 and head and neck squamous cell carcinoma: Cho et al. demonstrated that the combined treatment of citarinostat and the bromodomain and extra-terminal (BET) domain inhibitor JQ1 synergistically suppresses metastasis of head and neck squamous cell carcinoma (HNSCC) via desregulating matrix metalloproteinase (MMP)-2, MMP-9, and MMP-14 [29].