Menin inhibitor MI-503 reduced menin protein levels in MLL-FP transformed leukemia cell lines, but did not affect the menin mRNA level. MV4;11 and THP-1 cells were treated for 0-24 hours with analysis of mRNA levels at various time points. MV4;11, THP-1, and Jurkat cell lines were treated for 8 hours followed by analysis of protein levels by Western Blotting. Cells were counted by hand after treatment for 24 hours. A-C. MEN1 mRNA levels were detected by qRT-PCR. D. Western Blot of menin expression for MV4;11, THP-1, and Jurkat cell lines with treatment of 0, 1, or 3 μM MI-503. E. Western Blot of menin expression for MV4;11 with 8-hour treatment of 2 different menin inhibitors, MI-503 or MI-463, at varying concentrations. F. MV4;11, THP-1, and Jurkat cell lines were treated for 24 hours and cells were counted by hand.