In another study comparing 50 HPV positive head neck carcinoma to 50 HPV negative HNSCC, the authors identified two differently expressed proteins: prostate stem cell antigen (PSCA), which was upregulated, and eukaryotic elongation factor 1 alpha (EEF1α), which was down regulated in HPV-positive cells [64]. This evidence concerns the gene PSCA and head and neck squamous cell carcinoma.