The CSF1R SRE HEK293 recombinant cell line has been transfected with full-length human CSF1R cDNA under a CMV promoter for high constitutive expression. The SRE–luciferase reporter is also stably integrated into the genome. The firefly luciferase gene is controlled by 4 copies of the Serum Response Element upstream of a minimal promoter. Upon ligand binding, active CSF1R will initiate the MAPK/ERK signaling pathway, leading to expression of the SRE-controlled luciferase reporter.