GGT6 and head and neck squamous cell carcinoma: Its expression pattern at the protein level is unknown, however, GGT6 mRNA level was recently found to correlate with disease progression and patient outcomes in oral squamous cell carcinoma (15), papillary renal cell carcinoma (16), glioblastoma (17), hepatocellular carcinoma (18), and head-neck squamous cell carcinoma (19).