CD274 and cancer: There is increasing evidence suggesting that CSCs express diverse cytokines and growth factors that stimulate an immunosuppressive microenvironment in cancer,144–146 and are capable of escaping T-lymphocyte attack, while also being resistant to immunotherapy.147 In HNSCC, CSCs have been reported to express amplified levels of PD-L1.148 However, despite the recent advancements in cancer immunotherapy, there is a lack of studies investigating the effect of immune checkpoint MoAb on CSCs.