The proof of correlation of TNFR1 cell surface expression of primary myeloma cells with their TNF/MLN4924 sensitivity was not possible because standard FACS analysis of TNFR1 expression is too insensitive to detect functionally relevant amounts of this receptor, while more sensitive binding studies with iodinated or luciferase labeled TNFR1-specific antibodies or TNFR1-specific TNF mutants were not feasible with the limited quantities of primary MM cells available. Here, TNF is linked to plasma cell myeloma.