CCND1 and head and neck squamous cell carcinoma: Notably, several circRNAs, including circ_0000045, circ_0000052, circ_0023028, circ_0032822, circZNF609, circPVT1, circHIPK2, and circ-CCND1, are upregulated in both HNSCC tissues and cells, actively promoting HNSCC cell proliferation76-83.