XIAP and head and neck squamous cell carcinoma: In contrast to these HPV(−) HNSCC tissues and cell lines, in this study we observed that most HPV(+) HNSCC tissues and cell lines did not exhibit FADD and BIRC2 amplification and mRNA overexpression (Figs. 1, 2, Supplemental Figure 1), although protein expression of cIAP1 and XIAP were abundant (Fig. 3A).