PER2 and head and neck squamous cell carcinoma: Modulate cell proliferation, apoptosis and cell cycle progression Associated with carcinogenesis and later cancer stages; Perl via the AKT/mTOR pathway promotes OSCC progression; Regulation of the cycle in CDK/CKI cell cycle network in OSCC; Per2 suppresses oral squamous cell carcinoma progression by activating autophagy via the PDNAKT/mTOR pathway Associates with tumor development stage in HNSCC