EN4 (50 μM;?for 60 hours) treatment significantly decreases the protein levels of representative MYC-regulated target genes, including CDK2 and CDC25A.?EN4 treatment also substantially reduces MYC levels.EN4 shows the strongest inhibition of both MYC/MAX binding to its DNA consensus sequence in vitro as well as MYC transcriptional activity in cells.?EN4 inhibited MYC/MAX binding to the E-box response element DNA consensus sequence in a dose-responsive manner with an IC50 value of 6.7 μM.?EN4 also inhibits MYC luciferase reporter activity in a dose-responsive manner with an IC50 value of 2.8 μM.EN4 (1-50 μM; for 72 hours) treatment significantly impaires 231MFP breast cancer cell proliferation in a dosedependent manner, with >90% inhibition of proliferation at 50 μM.EN4 (50 μM;?for 2 hours) treatment significantly reduced MYC thermal stability in 231MFP breast cancer cells.