CLOCK-mediated acetylation of NF-κB p65 drives immune evasion in breast cancer

Disruption of circadian rhythm (DCR) has been connected with breast cancer (BC) susceptibility; whereas it is unclear whether status of key clock genes could be used in predicting BC prognosis, tumor immune microenvironment, and immunotherapy responses.

Circadian clock genes demonstrate significant dysregulation in BC, where elevated CLOCK expression emerges as an independent prognostic factor strongly correlated with adverse clinical outcomes. CLOCK-overexpressing BC cells exhibit enhanced proliferative ability and strong resistance to chemotherapy drugs doxorubicin and gemcitabine. High CLOCK expression correlates with reduced CD8⁺ T cell infiltration and increased M2 macrophage polarization, consistent with increased immune checkpoint molecule PD-L1 expression in the TCGA BC dataset. Additionally, patients with high CLOCK expression display lower Tumor Immune Dysfunction and Exclusion (TIDE) score. Mechanistically, RNA-sequencing identified suppressed NF-κB, TNF, MAPK pathways, and PD-L1 expression in sh-CLOCK MCF-7 cells. Subsequent in vitro validation demonstrated that CLOCK mediates NF-κB p65 acetylation at K56 site, potentiating its transcriptional activation of PD-L1, thereby facilitating immune evasion in BC.

CLOCK functions as a critical prognostic biomarker in BC by promoting tumor proliferation, chemoresistance, and immune evasion. Mechanistically, CLOCK mediates NF-κB p65 acetylation to enhance PD-L1 transcription, promoting immune evasion in BC.