However, one report showed that the expression of PD-1 on the lymphocytes of tumor infiltrates was not associated with the smoking status of lung cancer patients [38], whereas another described that current smokers have significantly lower numbers of CD8+ cytotoxic T cells and PD-L1+ cells than non- and former smokers in head and neck squamous cell carcinoma [39]. Here, CD274 is linked to head and neck squamous cell carcinoma.