Identification of LanC as an inhibitor of the Otub1/c-Maf axis. FDA-approved drugs (A) and natural products (B) provided by TargetMol were subjected to screen inhibitors of the Otub1/c-Maf axis as described in “Materials and methods.” (C) RPMI-8226 and LP1 were incubated with LanC at 100 nM for 24 hours, followed by IP/IB assays. (D) RPMI-8226 cells were treated with LanC for 24 hours, followed by IP/IB assays. (E) HEK293T cells were transfected with an HA-c-Maf plasmid and siOtub1 for 48 hours, followed by LanC treatment (24 hours) before being subjected to IP/IB assays. (F) HEK293T cells were cotransfected with c-Maf, MARE.Luci, and siOtub1 for 24 hours, followed by LanC treatment (8 hours) and a luciferase assay. (G-H) MM cells were incubated with LanC overnight, followed by IB (G) or RT-PCR (H) assays for indicated proteins or genes. (I) HEK293T cells were cotransfected with c-Maf and Otub1 for 24 hours, followed by LanC treatment (8 hours) and IP/IB assays to examine the interaction between Otub1 and c-Maf. *P < .05; **P < .01; ***P < .001. NS, not significant.