The transgenic construct was designed with a human keratin 14 promoter driving co-expression of both a turbo red fluorescent protein (tRFP) and a suicide gene, herpes simplex virus (HSV) thymidine kinase (TK), separated by a P2A peptide plus a neomycin selection cassette. The neomycin cassette was later removed. tRFP is a fast-maturing destabilized red (orange) fluorescent protein. (J:264089)