Reduction of cyclin D1 expression is also found in nasopharyngeal cancer (C666-1), prostate cancer (LNCaP) and head and neck squamous cell carcinoma (FaDU and Detroit 562) incubated with 5-20 mM metformin for 72 h (Sahra et al., 2008; Zhao et al., 2011; Sikka et al., 2012). This evidence concerns the gene CCND1 and head and neck squamous cell carcinoma.