CD8A and head and neck squamous cell carcinoma: Consistent with previous studies that used CD8 T cell as a prognostic biomarker [26], we found that PIK3CAAmp/TP53Mutated HNSCC patients expressed significantly lower levels of CD8 T cell gene signature in their tumor biopsy than PIK3CAWT/TP53WT and PIK3CAAmp/TP53WT patients (Figure 1D).