The CellSensor® LEF/TCF-bla SW480 cell line contains a beta-lactamase reporter gene under control of the lymphoid enhancer factor/T cell factor (LEF/TCF) consensus binding sequence stably integrated into SW480 cells, which express a truncated form of the tumor suppressor protein adenomatous polyposis coli (APC). This cell line is a clonal population isolated by flow cytometry, with the pathway validated using RNAi against beta-catenin. The truncated, loss-of-function version of APC expressed in this cell line prevents the proper assembly of the beta-catenin destruction complex. This results in the accumulation of noncomplexed beta-catenin and constitutive activation of this signaling pathway, which is not susceptible to further stimulation with Wnt ligand. This cell line has been tested for assay performance under variable DMSO concentrations and cell numbers. Due to the constitutive activity of this pathway and the absence of known inhibitors, all optimization studies for this CellSensor® line were performed using the beta-lactamase inhibitor clavulonic acid. Treatment with clavulonic acid mimics complete inhibition of the signaling pathway and allows determination of the maximum assay window. Wnt signaling via beta-catenin plays a central role in development and homeostasis. This pathway is invariably disrupted in colorectal tumors and commonly affected by mutation in other cancers. Wnt ligand binding and activation of the frizzled transmembrane receptors transduces the signal to a cytoplasmic protein known as dishevelled, which then inhibits the serine/threonine kinase glycogen synthase kinase 3 beta (GSK3B). This signal leads to functional inactivation and dissociation of a multiprotein beta-catenin destruction complex made up of APC, GSK3B, and a scaffold of axin. This results in dephosphorylation and dissociation of beta-catenin. Unphosphorylated beta-catenin is stabilized and accumulates in the cytoplasm of the cell. Beta-catenin then associates with the LEF/TCF family of transcription factors in the nucleus, leading to transcription and expression of target genes such as c-myc, c-jun, fra, and cyclin D1. Academic and non-profit customers, please inquire for special pricing.