MAP2K1 and plasma cell myeloma: Since inhibitors of MEK/ERK signaling pathway may induce some non-specific effects on myeloma cell growth and survival, we constitutively activated the MEK/ ERK signaling pathway by lentivirus-vector-mediated MEK1-cDNA transfection in CKS1B-silenced KMS28PE, OCI-MY5 and XG1 cells.