MKI67 and head and neck squamous cell carcinoma: Expression of mitochondrial tumor-suppressor genes (SIRT3, SIRT4, and MTUS1), a mitochondrial DNA repair gene (OGG1) and a proliferation marker (Ki-67) was measured by reverse transcription-quantitative polymerase chain reaction and real-time fluorescence quantitative polymerase chain reaction in HNSCC patients and controls by Mahjabeen and colleagues.