NFKB1 and plasma cell myeloma: That said, bortezomib was also shown to paradoxically activate NF-κB signaling in multiple myeloma cell lines, primary multiple myeloma cells, and in xenografts, indicating that bortezomib-induced cytotoxicity in multiple myeloma cells is not fully attributable to inhibition of NF-κB signaling [161, 162].