HES1 (hes family bHLH transcription factor 1) is a basic helix-loop-helix transcriptional repressor that plays critical roles in cell fate determination and developmental processes 1. The protein functions as a key downstream effector of Notch signaling pathways, regulating cell cycle control, proliferation, differentiation, survival, and apoptosis across multiple cell types including neuronal, endocrine, and T-lymphocyte progenitors 1. In human hematopoietic development, HES1 maintains stem cell quiescence by preserving a quiescent stem cell signature in CD34+ progenitor cells and is essential for early T-cell development, working non-redundantly with HES4 2. HES1 demonstrates significant clinical relevance in multiple contexts. In skin aging, HES1 expression declines early during the aging process, and its inhibition in fibroblasts compromises cell proliferation while increasing inflammation and cellular senescence 3. Conversely, genetic activation of HES1 or pharmacological treatment with quercetin can alleviate cellular senescence in dermal fibroblasts 3. In cancer, HES1 contributes to drug resistance mechanisms, as demonstrated in lung adenocarcinoma where the NOTCH4-HES1 pathway mediates resistance to EGFR tyrosine kinase inhibitors 4. Additionally, HES1 is crucial for proper organ development, as genetic mutations in HES1 can abolish biliary specification potential during hepato-biliary-pancreatic organogenesis 5.