Infections by P. gingivalis and F. nucleatum have been proven to cause cancer through pathways of MMP9 and upregulation of cytokines such as TNF-α, IL-1β, and IL-6 (Herrero et al., 2003; Whitmore and Lamont, 2014; Jahanshahi and Shirani, 2015). Here, MMP9 is linked to infection.