To explore the potential interactions among the three signaling molecules on MCL-1 expression in IL-6 treated myeloma cells, the protein expressions of STAT3, PI3K, MAPK and MCL-1 was profiled by Western blot in human 8226 myeloma cells transfected with shSTAT3-, shPI3K-, shMAPK1- or shMAPK3-bearing lentivirus. The gene discussed is MCL1; the disease is plasma cell myeloma.