Exposure of ACC cells to the MELK inhibitor, OTSSP167, was associated with dose-dependent decrease in rates of proliferation and colony formation. (A) MELK protein expression in H295R, CU-ACC1, and CU-ACC2 cell lines. (B) MELK inhibition using OTSSP167, the MELK inhibitor, was associated with decreased proliferation in H295R cells at doses >5 nM, (C) in CU-ACC1 cells at doses >25 nM, and (D) in CU-ACC2 cells at doses >5 nM. (E) Exposure to OTSSP167 was associated with decreases in clonogenicity of H295R cells at doses >0.5 nM, (F) in CU-ACC1 cells at doses >10 nM, and (G) in CU-ACC2 cells at doses >5 nM (*P < 0.05; **P < 0.01).