U937 SMAD/TGFbeta Reporter (Luc) cells are derived from the human pro-monocytic cell line U937 by stably integration of a SMAD/TGFbeta firefly luciferase reporter construct. U937 cells are able to differentiate into either dendritic cells or macrophages, depending on the surrounding signals. U937 cells are widely used for studies of monocyte/macrophage differentiation, the macrophage-tumor cell interaction and anti-cancer drug screening. U937 SMAD/TGFbeta Reporter (Luc) cells stably express firefly luciferase under the control of the SMAD/TGFbeta response elements, can be used for monitoring the activity of TGF?/SMAD signaling pathway.