CBR1 and head and neck squamous cell carcinoma: Consistently, the promoter reporter assay (Additional file 2: Figure S6) showed that IR dramatically increases the luciferase-activity of the plasmid-containing CBR1 promoter by more than 4-fold compared with the control (Fig. 4c), meaning that CBR1 is transcriptionally upregulated by IR in a variety of HNSCC cells.