Alteration of MDM2 by the Small Molecule YF438 Exerts Antitumor Effects in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) exhibits a high mortality rate and is the most aggressive subtype of breast cancer. As previous studies have shown that histone deacetylases (HDAC) may represent molecular targets for TNBC treatment, we screened a small library of synthetic molecules and identified a potent HDAC inhibitor (HDACi), YF438, which exerts effective anti-TNBC activity both in vitro and in vivo. Proteomic and biochemical studies revealed that YF438 significantly downregulated mouse double minute 2 homolog (MDM2) expression. In parallel, loss of MDM2 expression or blocking MDM2 E3 ligase activity rendered TNBC cells less sensitive to YF438 treatment, revealing an essential role of MDM2 E3 ligase activity in YF438-induced inhibition of TNBC. Mechanistically, YF438 disturbed the interaction between HDAC1 and MDM2, induced the dissociation of MDM2-MDMX, and subsequently increased MDM2 self-ubiquitination to accelerate its degradation, which ultimately inhibited growth and metastasis of TNBC cells. In addition, analysis of clinical tissue samples demonstrated high expression levels of MDM2 in TNBC, and MDM2 protein levels closely correlated with TNBC progression and metastasis. Collectively, these findings show that MDM2 plays an essential role in TNBC progression and targeting the HDAC1-MDM2-MDMX signaling axis with YF438 may provide a promising therapeutic option for TNBC. Furthermore, this novel underlying mechanism of a hydroxamate-based HDACi in altering MDM2 highlights the need for further development of HDACi for TNBC treatment. SIGNIFICANCE: This study uncovers the essential role of MDM2 in TNBC progression and suggests that targeting the HDAC1-MDM2-MDMX axis with a hydroxamate-based HDACi could be a promising therapeutic strategy for TNBC. ©2021 American Association for Cancer Research.