PDCD1LG2 and head and neck squamous cell carcinoma: The analysis of the expression of immune-modulating surface markers on the HNSCC also shows for Cal-33 that on the one hand RT mainly contributes to the regulation of these markers, but on the other hand the expression level of PD-L1 and PD-L2 on the cell surface contributes to a significant reduction of these markers by the additional administration of ATMi to RT.