CXCR4 and plasma cell myeloma: Given the potential role of CXCR4 in tumor growth and dissemination (Alsayed et al, 2007; Roccaro et al, 2015), its increased expression upon Dex exposure in a subset of MM.1S cells that do not express the proapoptotic gene BCL2L11 (Fig 6) raises the provocative possibility that minor populations of myeloma cells could proliferate in response to Dex.