CD74 and neoplasm: Mechanically, the inhibition of MIF activity with 4-IPP, or silencing of cell-surface CD74 by siRNA, in A375 and SB2, attenuated the antiproliferative effect of sCD74 released from THP-1 MΦ (Supplementary Fig. 7A, B), indicating that tumor-cell growth might be regulated by sCD74 released from THP-1 MΦ via modulation of MIF–CD74 interaction.