Genome-wide mapping of arsenic-activated Nrf2 reveals metabolic and epigenetic reprogramming in induced pluripotent stem cells

Arsenic (As³⁺) is a well-established environmental carcinogen known to induce malignant transformation and cancer stem-like cell (CSC) properties in somatic cells, with Nrf2 functioning as a central regulator. However, the impact of chronic As³⁺ exposure on pluripotent stem cells, particularly through Nrf2-mediated epigenetic and metabolic reprogramming, remains largely unexplored. In this study, we chronically exposed human induced pluripotent stem cells (iPSCs, Nips-B2) to an environmentally relevant concentration of trivalent arsenic (0.25 μM, As³⁺) for three months. The tumorigenic potential of exposed iPSCs was evaluated using anchorage-independent growth assays and xenograft models, while mechanistic insights were gained via chromatin immunoprecipitation sequencing (ChIP-seq) for Nrf2 and key histone modifications (H3K4me3, H3K9me3, H3K27me3, H3K36me3, and H4K20me3), alongside transcriptomic profiling by RNA sequencing (RNA-seq). Prolonged exposure markedly enhanced tumor sphere formation in vitro and accelerated tumor growth in vivo, indicating the acquisition of CSC-like traits. Integrated ChIP-seq and RNA-seq analyses revealed widespread Nrf2 chromatin binding and global epigenetic remodeling, characterized by increased levels of H3K27me3, H3K36me3, and H4K20me3, a modest rise in H3K9me3, and reduced H3K4me3. Notably, As³⁺ exposure enhanced Nrf2 binding at loci regulating glycolysis, cholesterol biosynthesis, self-renewal, and oncogenesis. Functional analyses confirmed that transcriptional and metabolic changes were Nrf2-driven and closely linked to H3K36me3 and H3K27me3 dynamics. Collectively, our findings demonstrate that chronic As³⁺ exposure reprograms iPSCs through Nrf2 activation and coordinated epigenetic remodeling, revealing a novel mechanism by which environmental carcinogens exploit stem cell plasticity to initiate CSC-like transformation.