Nrf2 orchestrates epigenetic regulations and serves as the master regulator of KLF4 expression and activity during arsenic-induced transformation

Abstract

Emerging evidence suggests that Nrf2 plays a pro-carcinogenic role in cancer. Our previous study showed that arsenic-induced Nrf2 activation triggers metabolic reprogramming, leading to the formation of cancer stem-like cells. Here, we further demonstrated that KLF4, a key pluripotency factor, is a direct transcriptional target of Nrf2 in arsenic-exposed human bronchial epithelial cells. ChIP-seq analysis identified multiple Nrf2 binding peaks at the Klf4 gene locus, which overlap with the enhancer markers H3K4me1 and H3K27Ac. Nrf2 knockout reduced both KLF4 expression and enhancer marker enrichment, accompanied by a global decrease in KLF4 binding across the genome. In wild-type (WT) cells, arsenic treatment increased KLF4 binding on genes involved in oncogenic pathways such as STAT3, SOX2, Nrf2, cell growth, Hedgehog, and EMT. We also found that KLF4 engages in a self-feedback loop in response to Nrf2 signaling. Lastly, our data showed that the co-occupancy of Nrf2 and KLF4 is crucial for establishing active enhancer hubs in the genome. These findings suggest that Nrf2s oncogenic effects are, in part, mediated by Nrf2 dependent self-amplification of KLF4 expression and function. Thus, targeting both Nrf2 and KLF4 could be a promising therapeutic strategy for eliminating cancer stem-like cells.