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.

Introduction: FBW7, a tumor suppressive E3 ubiquitin ligase frequently mutated in colorectal cancer (CRC), mediates chemotherapy resistance. While irinotecan (via its active metabolite SN38) is a first‐line TOP1 inhibitor for advanced CRC, the mechanistic link between FBW7 dysfunction and irinotecan resistance remains elusive. Methods: CRISPR/Cas9 gene editing and RNA interference were applied to establish FBW7‐knockout and ‐knockdown CRC cells. CCK8 assay was performed to detect the inhibition ratio of SN38 and Maritoclax on CRC cells. Western blot, immunochemistry, RT‐qPCR and co‐immunoprecipitation were performed to detect the expression and interaction of FBW7 and MCL1. The conformational change of the FBW7 R465C mutation and its interaction with substrates were elucidated through AlphaFold. An animal experiment was performed to detect the in vivo therapeutic effect of irinotecan and Maritoclax. Results: FBW7 deficiency (including loss, low expression and mutation) reduced SN38 sensitivity and upregulated MCL1 expression in both CRC cells and patient tissues. The R465C mutation disrupted FBW7‐MCL1 binding and stabilized MCL1. Moreover, SN38 modulated MCL1 expression, elevated MCL1 expression led to SN38 resistance in CRC cells. Maritoclax, a specific MCL1 inhibitor, reversed irinotecan/SN38 resistance in FBW7‐deficient CRC cells and xenograft models, synergizing with irinotecan to suppress tumor growth. Conclusions: FBW7 deficiency induces irinotecan resistance via MCL1 stabilization, which is therapeutically exploitable by Maritoclax. Our work identifies MCL1 inhibition as a precision strategy for FBW7‐deficient CRC and supports clinical translation of Maritoclax‐irinotecan combinations.

Circadian rhythm (CR) governs systemic and tissue physiological homeostasis by regulating sleep-wake cycles, hormone secretion, and metabolism. CR disruption (CRD), such as shift work, has been associated with increased cancer risk, particularly female breast cancer (BC), yet the mechanisms underlying breast tumorigenesis and immunosuppression resulting from a specific clock gene dysfunction remain unclear. Here, we identify that circadian regulator Period 2 (PER2) is significantly downregulated in BC and correlates with poor prognosis. PER2 functional deficiency mice ( PAS-B domain deletion, Per2 ^m/m ) display high susceptibility to DMBA/MPA-induced breast tumors. Tumor microenvironment (TME) profiling reveals that compared with Per2 ^wt tumors induced in Per2 ^wt mice, Per2 ^m/m tumors generated in Per2 ^m/m mice show reduced CD8⁺ T cells and M1-like macrophages infiltration and increased Foxp3 ⁺ Tregs and M2-like macrophages. Of note, reciprocal transplantation of Per2 ^m/m and Per2 ^wt tumors into Per2 ^wt or Per2 ^m/m mouse hosts reveals that systemic PER2 functional deficiency status not only boosts tumor growth but also promotes immunosuppression in TME. Consistently, Per2 knockdown in tumor cells enhances tumor cell proliferation and immune evasion in WT hosts. Mechanistically, PER2 knockdown leads to aberrant CLOCK transactivation, which upregulates the co-expression of HER2 and CD47, thereby leading to tumor aggressive growth with limited macrophage immune checkpoint surveillance. Collectively, our findings suggest that PER2 functional deficiency-driven CLOCK-HER2/CD47 axis promotes BC susceptibility and tumor immunosuppression, which provides a potential therapeutic target to mitigate CRD-associated BC risk and aggressiveness.

Nucleic acids are essential dietary components with diverse physiological functions. Numerous studies have focused on the biological functions of nucleotides, nucleosides, and functional RNAs such as microRNAs. However, the nutritional value of ribosomal RNA (rRNA)-derived oligonucleotides, which are likely the predominant nucleic acid-derived components in foods, remains largely unexplored. Here, yeast was used as a food-associated eukaryotic model organism to investigate the uptake and utilization of rRNA-derived oligonucleotides. Yeast efficiently utilized short RNA oligonucleotides (approximately 5–30 nt) as nutrient sources, supporting robust cell growth. Confocal microscopy confirmed rapid uptake of Cy5-labeled RNA oligonucleotides by yeast cells. Proteomic analysis further revealed marked upregulation of proteins involved in endocytosis and autophagy in yeast cultured with RNA oligonucleotides. Collectively, these findings demonstrate that yeast can internalize and metabolize rRNA-derived oligonucleotides as efficient nutrient sources, likely through coordinated endocytic and autophagic pathways. This study highlights the nutritional potential of rRNA-derived oligonucleotides and provides a foundation for their future application in functional foods and fermentation systems.