CTLA4 and head and neck squamous cell carcinoma: Meta-analyses have shown polymorphisms, resulting in an increased expression of the immunosuppressive genes, CTLA4, IL10, and cytochrome P450 1A1, are associated with a higher risk of HNSCC, suggesting both a suppressed anti-tumour immunity and a reduced ability to metabolise and de-toxify carcinogens, may be significant causes of HNSCC (6–8).