Curcumin and Cancer Stem Cells: Epigenetic Mechanisms Underlying Therapeutic Resistance and Tumor Relapse

Cancer stem cells (CSCs) drive therapeutic resistance, metastasis, and tumor recurrence through reversible transitions among stem-like, differentiated, epithelial, and mesenchymal states, which are sustained by interconnected epigenetic mechanisms. To our knowledge, this is the first review to integrate curcumin-mediated regulation of DNA methylation, chromatin remodeling, and non-coding RNAs within a single CSC plasticity framework and to propose the concept of an “epigenetic collapse of CSC plasticity” as a mechanistic explanation for how curcumin may weaken stemness, state switching, and adaptive treatment resistance. Evidence was critically evaluated through structured searches of PubMed/MEDLINE, Scopus, Web of Science Core Collection, Google Scholar, and citation tracking, while direct curcumin–epigenetic evidence was distinguished from independent CSC evidence and inferential mechanistic links. Curcumin has been reported to modulate DNMT1 and locus-specific DNA methylation; regulate HDACs, p300/CBP, EZH2, H3K27me3, and BMI1; and alter selected microRNA, long non-coding RNA, and circular RNA pathways, with comparatively stronger evidence involving the miR-34 family, miR-200c, miR-21, H19, and circHN1. However, current evidence is constrained by the predominance of bulk cancer-cell models, heterogeneous formulations and exposure conditions, and the scarcity of epigenetic rescue experiments combined with rigorous functional CSC assays. By unifying previously fragmented epigenetic evidence, this review advances a new evidence-weighted model in which curcumin may suppress CSC persistence not through a single molecular target, but by destabilizing the multilayer epigenetic circuitry that enables plasticity. Curcumin should therefore be regarded as a context-dependent, multilayer epigenetic modulator rather than an established CSC-eradicating therapy, and its translational relevance requires validation in prospectively defined CSC models with pharmacologically justified delivery and exposure conditions.