STAT1 and plasma cell myeloma: When we added the inhibitor specific for ERK1/2, STAT1, STAT3, or Akt to cocultures of myeloma cells and MSCs, we found that the kinase inhibitor alone or in combination reduced the expression of CXCL1, CXCL2, SDF1, and MCP1 in myeloma cells (Figure 5C).