PER2 and neoplasm: QRT-PCR was then performed on the above OSCC cells to detect the expression levels of tumor-associated genes, including TP53 (tumor protein p53), MMP1 (matrix metallopeptidase 1), ZEB1/2 (zinc finger E-box binding homeobox 1/2), and TWIST1/2 (twist family bHLH transcription factor 1/2), based on our previous RNA-sequencing results in PER2-overexpressed OSCC cells.