In particular, a close relationship between the upregulation of tumor-restricted PD-L1 and human CSC markers, basal cell markers and vimentin expression has been reported in invasive BC [20], as well as constitutive and inducible expression of PD-L1 in the CD44-positive CSC subset of head and neck squamous cell carcinoma [21]. The gene discussed is CD274; the disease is head and neck squamous cell carcinoma.