SIRT7 and head and neck squamous cell carcinoma: However, in head and neck squamous cell carcinoma (HNSCC), ovarian serous cystadenocarcinoma (OSC), and bladder urothelial carcinoma (BUC), SIRT7 low expression levels dramatically reduce the median survival time in p53MUT tumors, but not in p53WT tumors (Figure 4).