MMP9 and lip and oral cavity carcinoma: Also, investigations have shown that P. gingivalis promotes the development and progression of oral cancer by promoting oral cell proliferation and inducing the expression of key molecules such as nuclear factor kappa B (NF-κB), IL-6, signal transducer and activator of transcription 3 (STAT3), cyclin D1, and matrix metallopeptidase 9 (MMP-9) [108].