MM.1R/STAT5 Reporter (GFP) cells are derived from the human B lymphoblast MM.1R cell line by stably integration of a STAT5 GFP reporter construct. MM.1R cells have been used in to study the molecular and cellular mechanisms that drive multiple myeloma progression, and test the efficacy of new drugs or treatment strategies for multiple myeloma. MM.1R and MM.1S, were independently created from the parental cell line MM.1 to represent models of resistance and sensitivity, respectively, to dexamethasone. MM.1R/STAT5 Reporter (GFP) cells stably express GFP under the control of the STAT5 response elements, can be used for monitoring the activity of STAT5 signaling pathway.