MAPK3 and plasma cell myeloma: In addition, we observed the increased phosphorylation of ERK1/2, STAT1, STAT3, and Akt in myeloma cells cocultured with MSCs, while knockdown of integrin α6 in myeloma cells reduced those kinase phosphorylation (Figure 5B), suggesting that several signaling pathways were activated by integrin α6 in myeloma cells.