CCND1 and head and neck squamous cell carcinoma: Moreover, upregulated cyclin D1 could reverse the inactivation of WNT pathway-related proteins (Figure 4c) and the inhibitory cell effect (Figure 4(d,e)) caused by the knockdown of HCG18 in HN30 and SCC4 cells and vice versa, indicating that HCG18 might promote the tumorigenesis of HNSCC via cyclin D1 and subsequently activate WNT signaling.