Protein translation inhibitor Cycloheximide (CHX) enhanced MI-503 induced reduction of menin protein levels, but the reduction was blocked by MG132 treatment. MV4;11 and THP-1 cell lines were treated for up to 8 hours followed by analysis of protein levels by Western blotting, 10 μM CHX, 3 μM MI-503, 10 μM MG132. (A, C) Typical Western blot of menin expression in MV4;11 and THP-1 cell lines. (B, D) Image J Western Blot quantification of menin protein levels and analyzed by t-test, compared with vehicle (n=3). *P<0.05, **P<0.01, ***P<0.001. (E) Calculated menin half-life equations in MI treated MV4;11 and THP-1 cells from (B) and (D).