MCL1 and plasma cell myeloma: To examine whether silencing MCL-1 upstream signaling modulators STAT3, PI3K and MAPK could abrogate IL-6 triggered MCL-1 expression in myeloma cells, we constructed lentiviral GV217 vectors carrying small hairpin RNAs (shRNA) [13] for STAT3 (shSTAT3), PI3K (shPI3K) and MAPK1/2 (shMAPK1 or shMAPK2), and transfected the lentiviral vectors into myeloma cells.