Bone morphogenetic proteins (BMPs), members of the transforming growth factor beta (TGF-β) superfamily, play important roles in the development of the heart, central nervous system and cartilage. Disruption of BMP signaling affects the body plan of the developing embryo. BMPs propagate their signal by activating Activin receptor-like kinase (ALK), which in turn mediates the phosphorylation of R-Smads. Phosphorylated R-Smad associates with Smad4 and then translocates to the nucleus regulating gene expression. A375 cells are human malignant melanoma cells containing endogenous Smad signaling pathway. SBE-bla A375 cell line was engineered to express beta-lactamase under the control of Smad binding element. This cell line has been validated for Z' and EC50 under optimized conditions using BMP-4. This cell line has also responded to Nodal and was tested for assay performance under variable conditions, including DMSO concentration, cell number, stimulation time, substrate loading time. Additional information using various small molecule inhibitors and StealthTM RNAi is also provided.