Characterization of ZJ12 as a BRD4 ligand and its cellular effects in the MV4-11 leukemia cells

Abstract Objectives Bromodomain-containing protein 4 (BRD4), a canonical epigenetic reader, is implicated in regulating the expression of various genes. The current research aimed to analyze the binding mechanism of ZJ12 to the BRD4 bromodomain. Another purpose was to explore the anticancer activity and underlying mechanisms of ZJ12 in acute myeloid leukemia (AML) cell lines, as well as to evaluate the drug-like properties of ZJ12. Methods The cocrystal structure of ZJ12-BRD4 was resolved via X-ray crystallography. The CellTiter-GLO method was employed to evaluate the viability of cells. Intracellular protein levels of cellular myelocytomatosis oncogene (c-Myc) and B-cell lymphoma 2 (Bcl-2) were examined through western blot, while mRNA levels of c-Myc and cyclin-dependent kinase 4 (CDK4) were quantified by quantitative real-time PCR (qPCR). Cell cycle and apoptosis rate were examined using flow cytometry. The in-silico tools SwissADME and ADMETlab were utilized to predict the drug-likeness and toxicity profile of ZJ12. Results The small molecule ZJ12 bound to the pocket of the BRD4 bromodomain in a shape-matched manner, forming critical interactions with key amino acids. ZJ12 significantly downregulated c-Myc as well as Bcl-2 expression in MV4-11. Concomitantly, ZJ12 suppressed cell growth, triggered cell cycle arrest at the G 0 /G 1 phase and increased the apoptosis ratio of MV4-11. Furthermore, ZJ12 exhibits favorable drug-likeness and promising predicted safety profiles. Conclusions ZJ12 is an effective small-molecule inhibitor of BRD4 bromodomain with good drug-likeness and safety profiles. ZJ12 promotes the downregulation of c-Myc and Bcl-2 levels by targeting BRD4 in MV4-11, which ultimately contributes to its antitumor activity.