Discovery of a Small-Molecule Bromodomain-Containing Protein 4 (BRD4) Inhibitor That Induces AMP-Activated Protein Kinase-Modulated Autophagy-Associated Cell Death in Breast Cancer

Upon the basis of The Cancer Genome
Atlas (TCGA) data set, we identified
that several autophagy-related proteins such as AMP-activated protein
kinase (AMPK) were remarkably downregulated in breast cancer. Combined
with coimmuno­precipitation assay, we demonstrated that BRD4
might interact with AMPK. After analyses of the pharmacophore and
WPF interaction optimization, we designed a small-molecule inhibitor
of BRD4, 9f (FL-411)
which was validated by cocrystal structure with BD1 of BRD4. Subsequently, 9f was discovered to induce ATG5-dependent autophagy-associated
cell death (ACD) by blocking BRD4-AMPK interaction and thus activating
AMPK-mTOR-ULK1-modulated autophagic pathway in breast cancer cells.
Interestingly, the iTRAQ-based proteomics analyses revealed that 9f induced ACD pathways involved in HMGB1, VDAC1/2, and eEF2.
Moreover, 9f displayed a therapeutic potential on both
breast cancer xenograft mouse and zebrafish models. Together, these
results demonstrate that a novel small-molecule inhibitor of BRD4
induces BRD4-AMPK-modulated ACD in breast cancer, which may provide
a candidate drug for future cancer therapy.