Elevated AMPKα2 expression driven by CITED2-dependent CBP/p300 mediated H3K27 acetylation confers doxorubicin resistance in triple-negative breast cancer stem cells.

Previous studies demonstrate that the protein kinase AMP-activated catalytic subunit alpha 2 (AMPKα2), one of two isoforms of catalytic subunit of AMPK encoded by PRKAA2, is highly expressed and contributes to cell survival and chemo-resistance in TNBC. However, the mechanisms underlying AMPKα2 upregulation is poorly understood. Here, we found that AMPKα2 expression was decreased in primary TNBC but paradoxically increased in doxorubicin (DOX) resistant TNBC cancer stem cells (TBCSCs). DOX treatment led to an enrichment of TBCSCs and a concomitant increase in AMPKα2 expression. Mechanistically, enhanced AMPKα2 expression in TBCSCs was driven by H3K27 acetylation at PRKAA2 promoter. This epigenetic modification was facilitated by the histone acetyltransferases CBP/p300. Moreover, CITED2 was essential for CBP/p300-mediated H3K27 acetylation. Loss of CITED2 disrupted CBP/p300 localization and reduced H3K27 acetylation at PRKAA2 promoter. CITED2 directly bound to p300 via its C-terminal LPEL domain, promoting the formation and localization of the CBP/p300/CITED2 complex at PRKAA2 promoter. Disruption of CITED2/p300/CBP complex using an exogenous LPEL peptide inhibited H3K27 acetylation at the PRKAA2 promoter, decreasing AMPKα2 expression. Up-regulation of AMPKα2 promoted stemness properties and conferred DOX resistance in both cell line-derived and patient-derived TBCSCs. Further, we found LPEL peptide significantly suppressing TBCSCs stemness properties. Importantly, this approach sensitized DOX-resistant TBCSCs to DOX treatment. Our findings revealed a critical role of CITED2-dependent p300/CBP mediated H3K27 acetylation in promoting AMPKα2 expression within TBCSCs and contributing to DOX resistance. Targeting the CITED2/p300/CBP complex with an exogenous LPEL peptide represents a promising strategy to overcome DOX resistance in TNBC.