NRF2 controls iron homeostasis and ferroptosis through HERC2 and VAMP8

Abstract

Enhancing the intracellular labile iron pool (LIP) represents a powerful, yet untapped strategy for driving ferroptotic death of cancer cells. Here, we show that NRF2 maintains iron homeostasis by controlling HERC2 (E3 ubiquitin ligase for NCOA4 and FBXL5) and VAMP8 (mediates autophagosome-lysosome fusion). NFE2L2/NRF2 knockout cells have low HERC2 expression, leading to a simultaneous increase in ferritin and NCOA4 and recruitment of apoferritin into the autophagosome. NFE2L2/NRF2 knockout cells also have low VAMP8 expression, which leads to ferritinophagy blockage. Therefore, deletion of NFE2L2/NRF2 results in apoferritin accumulation in the autophagosome, an elevated LIP, and enhanced sensitivity to ferroptosis. Concordantly, NRF2 levels correlate with HERC2 and VAMP8 in human ovarian cancer tissues, as well as ferroptosis resistance in a panel of ovarian cancer cell lines. Last, the feasibility of inhibiting NRF2 to increase the LIP and kill cancer cells via ferroptosis was demonstrated in preclinical models, signifying the impact of NRF2 inhibition in cancer treatment.

Anti-Ferroptotic Effects of Nrf2: Beyond the Antioxidant Response

“…Recently, our group showed that Nrf2 regulates iron homeostasis by controlling both ferritin synthesis and degradation as illustrated in Fig. 3 ( Anandhan et al, 2023 ). First, HERC2 , encoding an E3 ubiquitin ligase for NCOA4 (a cargo adapter for ferritin degradation by autophagy [ferritinophagy]) and FBXL5 (an iron-dependent regulator of IRP1/2 that binds to the iron responsive element in the 5’-UTR of FTH1 and FTL mRNA thereby repressing their translation and preventing ferritin synthesis) was identified as a novel Nrf2 target gene.…”

“…Thus, Nrf2 regulates ferritin protein stability at both the translational and ferritinophagy-dependent turnover levels. Critically, we showed that these two mechanisms are vital to mediating Nrf2-driven resistance to ferroptosis induction in cancer cells, as deletion of Nrf2 resulted in ferritinophagy blockage, NCOA4-dependent recruitment of apoferritin to the autophagosome, an elevated LIP, and enhanced sensitivity to the ferroptosis inducer imidazole ketone erastin ( Anandhan et al, 2023 ). Overall, Nrf2 regulation of iron homeostasis is a critical determinant of a cell’s sensitivity or resistance to ferroptosis, which is independent of its antioxidant function, as discussed below.…”

“…This was demonstrated in a study using the alkaloid trigonelline (a potent, but non-specific Nrf2 inhibitor), which enhanced the anticancer activity of erastin and sorafenib in HCC cells ( Sun et al, 2016 ), as well as artesunate sensitivity in HNC cells ( Roh et al, 2017 ). We have shown that brusatol, the first NRF2 inhibitor developed by our group ( Ren et al, 2011 ), enhanced the efficacy of imidazole ketone erastin in promoting ferroptosis and preventing tumor growth in several pre-clinical models of ovarian cancer ( Anandhan et al, 2023 ). Another study indicated that cotreatment with brusatol and erastin was more effective than either single treatment in killing NSCLC cells, which was partly due to Nrf2 regulation of the FOCAD-FAK signaling pathway ( Liu et al, 2020 ).…”

The Multifaceted Roles for NRF2 in Regulating Tumor Development and Progression: An Update

“…Recent studies have indicated that NRF2 regulates the expression of genes controlling ferroptosis. By maintaining iron homeostasis and mitigating lipid peroxidation, NRF2 protects the cancer cells against ferroptotic cell death ( Anandhan et al, 2023 ). By extending this finding, Aryatara Shakya et al discuss the anti-ferroptic function of NRF2, which indicates the feasibility of inhibiting NRF2 to increase the intracellular labile iron pool and thus sensitize cancer cells to ferroptosis.…”

Editorial: Emerging strategies for cancer therapy targeting ferroptosis

“…Recent studies have shown that small molecules can induce cancer ferroptosis through ferroptosis center molecules such as GPX4, Xc- system, and NRF2. These compounds that induce ferroptosis have the common characteristic of high iron activity, which provides ideas for drug development ( 8 , 9 ). The papers we included suggest that Wogomin, Manolide, and the compound zoledronic acid can induce ferroptosis in cancer cells.…”