Circadian Rhythm Disruption in Triple-Negative Breast Cancer: Molecular Insights and Treatment Strategies

Disruption of the circadian clock has been closely linked to the initiation, development, and progression of cancer. This study aims to explore the impact of circadian rhythm disruption (CRD) on triple-negative breast cancer (TNBC). We analyzed bulk and single-cell RNA sequencing data to assess circadian rhythm status in TNBC using multiple bioinformatic tools, alongside metabolomic profiles and tumor microenvironment evaluations to understand the influence of CRD on metabolic reprogramming and immune evasion. The results indicate that TNBC experiences profound CRD. Patients with a higher CRDscore exhibit significantly poorer relapse-free survival compared to those with a lower CRDscore. Cyclic ordering by periodic structure (CYCLOPS) identified significant changes in rhythmic gene expression patterns between TNBC and normal tissues, with TNBC showing a "rush hour" effect, where peak expression times are concentrated within specific time windows. Transcripts with disrupted circadian rhythms in TNBC were found to be involved in key pathways related to cell cycle regulation, metabolism, and immune response. Metabolomic analysis further revealed that TNBCs with high CRDscore are enriched in carbohydrate and amino acid metabolism pathways, notably showing upregulation of tryptophan metabolism. High CRDscore was also linked to an immunosuppressive tumor microenvironment, characterized by reduced immune cell infiltration, exhausted CD8⁺ T cells, and a diminished response to immune checkpoint blockade therapy. These findings suggest that the disrupted molecular clock in TNBC may activate tryptophan metabolism, thereby promoting immune evasion and potentially reducing the effectiveness of immunotherapy.