TK6/RFP-luciferase cells are derived from the human lymphoblastoid TK6 cell line by stably integration of a constitutive RFP-firefly luciferase expression construct. TK6 cells are heterozygous for thymidine kinase (TK), are commonly used in research related to genotoxicity, mutagenesis, and DNA repair, as well as evaluating the safety of new drug candidates. TK6/RFP-Luciferase cells stably express both RFP and firefly luciferase reporters, can be used for in vitro assays and in vivo imaging.