RARRES1 and head and neck squamous cell carcinoma: We chose multiple elements present in the vicinity of 5 genes known to be RA-responsive in cells of squamous epithelial origin, RAI1, GPRC5A (RAI3), SMYD5 (RAI15), RARRES1 and RARRES3, and assessed RAR binding to these elements in SCC25 cells, a relatively well-differentiated human head and neck squamous cell carcinoma (HNSCC) line [28].