PTTG2 and head and neck squamous cell carcinoma: In HNSCC, significant up-regulation of PTTG3P, PTTG1 and PTTG2 expressions between normal and cancer samples was observed (3.758 vs. 7.534; p = 1.62 × 10−12), (62.059 vs. 129.031; p = 1.62 × 10−12) and (0.776 vs. 1.533; p = 2.04 × 10−12), respectively, Figure 2A. Moreover, based on the National Institute of Health’s (NIH) classification, HNSCC patients were divided into three groups according to the localization of cancer and expression levels of PTTG3P, PTTG1 and PTTG2. Afterwards, these subgroups were analyzed.