circPARPBP promotes cancer stemness and chemoresistance in triple-negative breast cancer through recruiting SRCAP complex to activate CCL20 transcription.

The identification of novel therapeutic targets and agents to overcome chemoresistance remains a central challenge in triple-negative breast cancer (TNBC). Here, we report three key innovations: the discovery of a novel oncogenic circRNA, circPARPBP, as a driver of chemoresistance; the elucidation of its mechanism through the recruitment of the SRCAP complex to activate CCL20 transcription and cancer stemness; and the demonstration that the natural compound isoliquiritigenin (ISL) effectively suppresses this axis to overcome chemoresistance. TNBC is the most aggressive subtype of breast cancer with poor prognosis and limited treatment options. In this study, we identified circPARPBP, a circRNA (hsa_circ_0000432) derived from PARPBP gene, which was aberrantly upregulated in TNBC tissues and cells. Clinically, the upregulation of circPARPBP was notably associated with TNBC chemoresistance. In vitro and in vivo experiments demonstrated that circPARPBP promoted TNBC progression and chemoresistance. Mechanistically, circPARPBP recruited the SNF2-related CBP activator protein (SRCAP) complex to activate C-C motif chemokine ligand 20 (CCL20) transcription and thus contributed to cancer stemness and chemoresistance. ISL, a key bioactive substance extracted from licorice root, effectively suppressed the circPARPBP-SRCAP-CCL20 signaling pathway. Notably, patient-derived xenograft models demonstrated that ISL treatment effectively overcame TNBC chemoresistance, with a superior benefit when in combination with conventional chemotherapy. Collectively, our study identifies circPARPBP as a novel regulator of TNBC progression and chemoresistance via SRCAP-mediated CCL20 activation, and provides a preclinical rationale for the clinical development of ISL as a potential therapy targeting this axis.