2-Deoxy-D-glucose and 6-aminonicotinamide-mediated Nrf2 down regulation leads to radiosensitization of malignant cells via abrogation of GSH-mediated defense

Blockade of glucose-6-phosphate dehydrogenase induces immunogenic cell death and accelerates immunotherapy

BACKGROUND

Enhanced glucose metabolism has been reported in many cancers. Glucose-6-phosphate dehydrogenase (G6PD) is a rate-limiting enzyme involved in the pentose phosphate pathway, which maintains NADPH levels and protects cells from oxidative damage. We recently found that low G6PD expression correlates with active tumor immunity. However, the mechanism involving G6PD and tumor immunity remained unclear.

METHODS

We conducted in vitro studies using G6PD-knocked down malignant melanoma cells, pathway analysis using the GEO dataset, in vivo studies in combination with immune checkpoint inhibitors (ICIs) using a mouse melanoma model, and prognostic analysis in 42 melanoma patients and 30 lung cancer patients who were treated with ICIs.

RESULTS

Inhibition of G6PD, both chemically and genetically, has been shown to decrease the production of NADPH and reduce their oxidative stress tolerance. This leads to cell death, which is accompanied by the release of high mobility group box 1 and the translocation of calreticulin to the plasma membrane. These findings suggested that inhibiting G6PD can induce immunogenic cell death. In experiments with C57BL/6 mice transplanted with G6PD-knockdown B16 melanoma cells and treated with anti-PD-L1 antibody, a significant reduction in tumor size was observed. Interestingly, inhibiting G6PD in only a part of the lesions increased the sensitivity of other lesions to ICI. Additionally, out of 42 melanoma patients and 30 lung cancer patients treated with ICIs, those with low G6PD expression had a better prognosis than those with high G6PD expression (p=0.0473; melanoma, p=0.0287; lung cancer).

CONCLUSION

G6PD inhibition is a potent therapeutic strategy that triggers immunogenic cell death in tumors, significantly augmenting the efficacy of immunotherapies.

Targeting AKT-Dependent Regulation of Antioxidant Defense Sensitizes AKT-E17K Expressing Cancer Cells to Ionizing Radiation

Aberrant activation of the phosphatidyl-inositol-3-kinase/protein kinase B (AKT) pathway has clinical relevance to radiation resistance, but the underlying mechanisms are incompletely understood. Protection against reactive oxygen species (ROS) plays an emerging role in the regulation of cell survival upon irradiation. AKT-dependent signaling participates in the regulation of cellular antioxidant defense. Here, we were interested to explore a yet unknown role of aberrant activation of AKT in regulating antioxidant defense in response to IR and associated radiation resistance.

We combined genetic and pharmacologic approaches to study how aberrant activation of AKT impacts cell metabolism, antioxidant defense, and radiosensitivity. Therefore, we used TRAMPC1 (TrC1) prostate cancer cells overexpressing the clinically relevant AKT-variant AKT-E17K with increased AKT activity or wildtype AKT (AKT-WT) and analyzed the consequences of direct AKT inhibition (MK2206) and inhibition of AKT-dependent metabolic enzymes on the levels of cellular ROS, antioxidant capacity, metabolic state, short-term and long-term survival without and with irradiation.

TrC1 cells expressing the clinically relevant AKT1-E17K variant were characterized by improved antioxidant defense compared to TrC1 AKT-WT cells and this was associated with increased radiation resistance. The underlying mechanisms involved AKT-dependent direct and indirect regulation of cellular levels of reduced glutathione (GSH). Pharmacologic inhibition of specific AKT-dependent metabolic enzymes supporting defense against oxidative stress, e.g., inhibition of glutathione synthase and glutathione reductase, improved eradication of clonogenic tumor cells, particularly of TrC1 cells overexpressing AKT-E17K.

We conclude that improved capacity of TrC1 AKT-E17K cells to balance antioxidant defense with provision of energy and other metabolites upon irradiation compared to TrC1 AKT-WT cells contributes to their increased radiation resistance. Our findings on the importance of glutathione de novo synthesis and glutathione regeneration for radiation resistance of TrC1 AKT-E17K cells offer novel perspectives for improving radiosensitivity in cancer cells with aberrant AKT activity by combining IR with inhibitors targeting AKT-dependent regulation of GSH provision.

The antioxidative stress regulator Nrf2 potentiates radioresistance of oral squamous cell carcinoma accompanied with metabolic modulation

Nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates the expression of critical antioxidant proteins, was recently demonstrated to play a key role in cancer progression. Resistance to radiotherapy is a major obstacle in treating oral squamous cell carcinoma (OSCC). However, little is known about the association between Nrf2 and radioresistance in OSCC. Two OSCC cell lines (SAS and HSC-2) and their clinically relevant radioresistant (CRR) clones (SAS-R, HSC-2-R) were used. The effects of Nrf2 downregulation on radiosensitivity and the involvement of glycolysis in Nrf2-mediated radioresistance were evaluated. Immunohistochemistry of phosphorylated Nrf2 (p-Nrf2) was performed in 110 patients with OSCC who underwent preoperative chemoradiotherapy and surgery. Nrf2 was stably upregulated in CRR cells in vitro and in a mouse xenograft model. Moreover, elevated Nrf2 expression was associated with radioresistance. The enhancement of Nrf2-dependent glycolysis and glutathione synthesis was involved in the development of radioresistance. Additionally, p-Nrf2 expression was closely related to the pathological response to chemoradiotherapy, and its expression was predictive of prognosis in patients with advanced OSCC. Our results suggest that Nrf2 plays an important role in the radioresistance of OSCC accompanied by metabolic reprogramming. Targeting Nrf2 antioxidant pathway may represent a promising treatment strategy for highly malignant OSCC.

Sphingosine kinase inhibitor, SKI-II confers protection against the ionizing radiation by maintaining redox homeostasis most likely through Nrf2 signaling

Exposure to ionizing radiation (IR) set a series of deleterious events causing acute radiation syndrome and mortality, posing the need for a potent and safe radio-protective drug. IR induces cell death predominantly by causing oxidative stress and macromolecular damage. The pre-existing antioxidant defence machinery of the cellular system plays a crucial role in protecting the cells against oxidative stress by activation of Nrf2. The current study was undertaken to investigate the radio-protective potential of sphingosine kinase inhibitor (SKI-II), which was demonstrated to activate Nrf2 signaling. The safety and efficacy of SKI-II were evaluated with cell cytotoxicity, proliferation index, and clonogenic survival assays in different cell lines, namely Raw 264.7, INT-407, IEC-6 and NIH/3T3 cell lines. A safe dose of SKI-II was found radio-protective in all the cell lines linked with the activated antioxidant defence system, thereby resulting in the amelioration of IR induced oxidative stress. SKI-II pretreatment also significantly reduced DNA damage, micronuclei expression, and accelerated DNA repair kinetics as compared to IR exposed cells. Reduced oxidative stress and enhanced DNA repair significantly reduced apoptosis and suppressed the pro-death signaling associated with IR exposure. Furthermore, the in-vitro observation was verified in the in-vivo model (C57 BL/6). The Intra-peritoneal (IP) administration of SKI-II, 2 h before a lethal dose of IR exposure (7.5 Gy) resulted in 75% survival. These results imply that SKI-II ameliorates IR-induced oxidative stress and cell death by inducing anti-oxidant defence system and DNA repair pathways, thus strengthening its potential to be used as radiation countermeasure.

Glucose 6-phosphate dehydrogenase inhibition sensitizes melanoma cells to metformin treatment

Most cancer cells exacerbate the pentose phosphate pathway (PPP) to enhance biosynthetic precursors and antioxidant defenses. Metformin, which is used as a first-line oral drug for the treatment of type 2 diabetes, has been proposed to inhibit the malignant progression of different types of cancers. However, metformin has shown poor efficacy as single agent in several clinical trials. Thus, the aim of the present work was to investigate whether the pharmacological inhibition of G6PDH, the first and rate-limiting enzyme of the PPP, by 6-amino nicotinamide (6-AN) potentiates the antitumoral activity of metformin on different human melanoma cell lines. Our results showed that 6-AN has sensitizing properties to metformin cytotoxicity. The combination of metformin and 6-AN decreased glucose consumption and lactate production, altered the mitochondrial potential and redox balance, and thereby blocked melanoma cell progression, directing cells to apoptosis and necrosis. To our knowledge, this is the first study describing the effect of this combination. Future preclinical studies should be performed to reveal the biological relevance of this finding.

Overcoming radioresistance in WiDr cells with heavy ion irradiation and radiosensitization by 2-deoxyglucose with photon irradiation

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2-DG acts as a radiosensitizer to photons depending on the time of its application.

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There is no sensitization to ¹²C irradiation by 2-DG.

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¹²C combination therapy still has the higher dose effectiveness.

Background and purpose

Radiosensitizers and heavy ion irradiation could improve therapy for female patients with malignant tumors located in the pelvic region through dose reduction. Aim of the study was to investigate the radiosensitizing potential of 2-deoxy-d-glucose (2-DG) in combination with carbon ion-irradiation (¹²C) in representative cell lines of cancer in the female pelvic region.

Materials and methods

The human cervix carcinoma cell line CaSki and the colorectal carcinoma cell line WiDr were used. 2-DG was employed in two different settings, pretreatment and treatment simultaneous to irradiation. Clonogenic survival, α and β values for application of the linear quadratic model and relative biological effectiveness (RBE) were determined. ANOVA tests were used for statistical group comparison. Isobolograms were generated for curve comparisons.

Results

The comparison of monotherapy with ¹²C versus photons yielded RBE values of 2.4 for CaSki and 3.5 for WiDr along with a significant increase of α values in the ¹²C setting. 2-DG monotherapy reduced the colony formation of both cell lines. Radiosensitization was found in WiDr for the combination of photon irradiation with synchronous application of 2-DG. The same setup for ¹²C showed no radiosensitization, but rather an additive effect. In all settings with CaSki, the combination of irradiation and 2-DG exhibited additive properties.

Conclusion

The combination of 2-DG and photon therapy, as well as irradiation with carbon ions can overcome radioresistance of tumor cells such as WiDr.

Berberine Effects on NFκB, HIF1A and NFE2L2/AP-1 Pathways in HeLa Cells

Background:

Berberine has multitudinous anti-cancer stem cells effects making it a highly promising candidate substance for the next-generation cancer therapy. However, berberine modes of action predispose it to significant side-effects that probably limit its clinical testing and application.

Materials and Methods:

HeLa cells were treated with two concentrations of berberine (30 and 100 µM) for 24 hours to assess the functioning of the NFE2L2/AP-1, NFκB and HIF1A pathways using 22 RNAs expression qPCR-based analysis.

Results:

Berberine effects appeared to be highly dose-dependent, with the lower concentration being capable of suppressing the NFκB functioning and the higher concentration causing severe signaling side-effects seen in the HIF1A pathway and the NFE2L2 sub-pathways, and especially and more importantly in the AP-1 sub-pathway.

Conclusion:

The results of the study suggest that berberine has clinically valuable anti-NFκB effects however jeopardized by its side effects on the HIF1A and especially NFE2L2/AP-1 pathways, its therapeutic window phenomenon and its cancer type-specificity. These, however, may be ameliorated using the cocktail approach, provided there is enough data on signaling effects of berberine.

Impact and Relevance of the Unfolded Protein Response in HNSCC

Head and neck squamous cell carcinomas (HNSCC) encompass a heterogeneous group of solid tumors that arise from the upper aerodigestive tract. The tumor cells face multiple challenges including an acute demand of protein synthesis often driven by oncogene activation, limited nutrient and oxygen supply and exposure to chemo/radiotherapy, which forces them to develop adaptive mechanisms such as the Unfolded Protein Response (UPR). It is now well documented that the UPR, a homeostatic mechanism, is induced at different stages of cancer progression in response to intrinsic (oncogenic activation) or extrinsic (microenvironment) perturbations. This review will discuss the role of the UPR in HNSCC as well as in the key processes that characterize the physiology of HNSCC. The role of the UPR in the clinical context of HNSCC will also be addressed.

Modulators of Redox Metabolism in Head and Neck Cancer

SIGNIFICANCE

Head and neck squamous cell cancer (HNSCC) is a complex disease characterized by high genetic and metabolic heterogeneity. Radiation therapy (RT) alone or combined with systemic chemotherapy is widely used for treatment of HNSCC as definitive treatment or as adjuvant treatment after surgery. Antibodies against epidermal growth factor receptor are used in definitive or palliative treatment. Recent Advances: Emerging targeted therapies against other proteins of interest as well as programmed cell death protein 1 and programmed death-ligand 1 immunotherapies are being explored in clinical trials.

CRITICAL ISSUES

The disease heterogeneity, invasiveness, and resistance to standard of care RT or chemoradiation therapy continue to constitute significant roadblocks for treatment and patients' quality of life (QOL) despite improvements in treatment modality and the emergence of new therapies over the past two decades.

FUTURE DIRECTIONS

As reviewed here, alterations in redox metabolism occur at all stages of HNSCC management, providing opportunities for improved prevention, early detection, response to therapies, and QOL. Bioinformatics and computational systems biology approaches are key to integrate redox effects with multiomics data from cells and clinical specimens and to identify redox modifiers or modifiable target proteins to achieve improved clinical outcomes. Antioxid. Redox Signal.

Targeting antioxidant enzymes as a radiosensitizing strategy

Radiotherapy represents a major anti-cancer modality and effectively kills cancer cells through generation of reactive oxygen species (ROS). However, cancer cells are commonly characterized by increased activity of ROS-scavenging enzymes in adaptation to intrinsic oxidative stress, leading to radioresistance. Abrogation of this defense network by pharmacological ROS insults therefore is shown to improve radioresponse in preclinical models; some of them are then tested in clinical trials. In this review, we address (1) the importance of ROS in radioresponse, (2) the main systems regulating redox homeostasis with a special focus on their prognostic effect and predictive role in radiotherapy, and (3) the potential radiosensitizers acting through inhibition of antioxidant enzymes.

Modulation of G6PD affects bladder cancer via ROS accumulation and the AKT pathway in vitro

Glucose-6-phosphate dehydrogenase (G6PD) is a rate-limiting enzyme of the pentose phosphate pathway. Multiple studies have previously revealed that elevated G6PD levels promote cancer progression in numerous tumor types; however, the underlying mechanism remains unclear. In the present study, it was demonstrated that high G6PD expression is a poor prognostic factor in bladder cancer, and the levels of G6PD expression increase with increasing tumor stage. Patients with bladder cancer with high G6PD expression had worse survival rates compared with those with lower G6PD expression in resected tumors. In vitro experiments revealed that knockdown of G6PD suppressed cell viability and growth in Cell Counting Kit-8 and colony formation assays, and increased apoptosis in bladder cancer cell lines compared with normal cells. Further experiments indicated that the weakening of the survival ability in G6PD-knockdown bladder cancer cells may be explained by intracellular reactive oxygen species accumulation and protein kinase B pathway suppression. Furthermore, it was additionally revealed that 6-aminonicotinamide (6-AN), a competitive G6PD inhibitor, may be a potential therapy for bladder cancer, particularly in cases with high G6PD expression, and that the combination of cisplatin and 6-AN may optimize the clinical dose or minimize the side effects of cisplatin.

Preclinical Rationale and Clinical Considerations for Radiotherapy Plus Immunotherapy: Going Beyond Local Control

The use of radiation for cancer therapy has expanded and sparked interest in possible synergistic effects by combining it with current immunotherapies. In this review, we present a case of a patient who responded to programmed cell death 1 (PD1) blockade and radiation therapy and discuss possible mechanisms. We provide background on the blockade of the cytotoxic T-lymphocyte antigen 4 (CTLA-4) and PD1 checkpoints and highlight future immune-based therapies that may synergize with radiation, including cytosine-phosphate-guanine vaccines, OX40 agonists, CD40 agonists, regulatory T-cell depletion, and metabolic "rewiring" of cancer cells. Clinical considerations are noted for combining radiation with immunotherapies to extend the benefit of immunotherapy to more patients. New trials are needed to appropriately investigate the best sequencing and radiation dose to prime an immune response and to identify predictive biomarkers of such responses.

Deltamethrin induced RIPK3-mediated caspase-independent non-apoptotic cell death in rat primary hepatocytes

Deltamethrin (DLM), a synthetic pyrethroid insecticide, is used all over the world for indoor and field pest management. In the present study, we investigated the elicited pathogenesis of DLM-induced hepatotoxicity in rat primary hepatocytes. DLM-induced cell death was accompanied with increased ROS generation, decreased mitochondrial membrane potential and G2/M arrest. Pre-treatment with N-acetyl cysteine/butylated hydroxyanisole/IM54 could partly rescue hepatocytes suggesting that ROS might play a role in DLM-induced toxicity. Interestingly, DLM treatment resulted in a caspase-independent but non-apoptotic cell death. Pre-treatment with pan-caspase inhibitor (ZVAD-FMK) could not rescue hepatocytes. Unaltered caspase-3 activity and absence of cleaved caspase-3 also corroborated our findings. Further, LDH release and Transmission electron microscopy (TEM) analysis demonstrated that DLM incites membrane disintegrity and necrotic damage. Immunochemical staining revealed an increased expression of inflammatory markers (TNFα, NFκB, iNOS, COX-2) following DLM treatment. Moreover, the enhanced RIPK3 expression in DLM treated groups and prominent rescue from cell death by GSK-872 indicated that DLM exposure could induce programmed necrosis in hepatocytes. The present study demonstrates that DLM could induce hepatotoxicity via non-apoptotic mode of cell death.

The greedy nature of mutant RAS: a boon for drug discovery targeting cancer metabolism?

RAS oncogene mutations are frequently detected in human cancers. Among RAS-mediated tumorigenesis, KRAS-driven cancers are the most frequently diagnosed and resistant to current therapies. Despite more than three decades of intensive efforts, there are still no specific therapies for mutant RAS proteins. While trying to block those well-established downstream pathways, such as the RAF-MAPK pathway and the PI3K-AKT pathway, attentions have been paid to potential effects of RAS on metabolic pathways and the feasibility for targeting these pathways. Recent studies have proved that RAS not only promotes aerobic glycolysis and glutamine metabolism reprograming to provide energy, but it also facilitates branched metabolism pathways, autophagy, and macropinocytosis. These alterations generate building blocks for tumor growth and strengthen antioxidant defense in tumor cells. All of these metabolic changes meet different demands of RAS-driven cancers, making them distinct from normal cells. Indeed, some achievements have been made to inhibit tumor growth through targeting specific metabolism rewiring in preclinical models. Although there is still a long way to elucidate the landscape of altered metabolism, we believe that specific metabolic enzymes or pathways could be therapeutically targeted for selective inhibition of RAS-driven cancers.

Energy metabolism in a matched model of radiation resistance for head and neck squamous cell cancer

While radiation therapy is commonly used for treating cancer, radiation resistance can limit long-term control of the disease. In this study, we investigated the reprogramming of the energy metabolism in radiosensitive and radioresistant head and neck squamous cell carcinomas (HNSCC) using a preclinical matched model of radiation resistance. Our investigation found that radioresistant rSCC-61 cells: 1. They display increased glucose uptake and decreased fatty acid uptake; 2. They deviate from the classical Warburg effect by diverting the glycolytic flux into the pentose phosphate pathway; 3. They are more dependent on glucose than glutamine metabolism to support growth; 4. They have decreased mitochondrial oxidative phosphorylation; 5. They have enhanced fatty acid biosynthesis by increasing the expression of fatty acid synthase; and 6. They utilize endogenous fatty acids to meet the energy demands for proliferation. Inhibition of fatty acid synthase with orlistat or FASN siRNA resulted in increased cytotoxicity and sensitivity to radiation in rSCC-61 cells. These results demonstrate the potential of combination therapy using radiation and orlistat or other inhibitors of lipid and energy metabolism for treating radiation resistance in HNSCC.

Cytoprotection "gone astray": Nrf2 and its role in cancer

Nrf2 has gained great attention with respect to its pivotal role in cell and tissue protection. Primarily defending cells against metabolic, xenobiotic and oxidative stress, Nrf2 is essential for maintaining tissue integrity. Owing to these functions, Nrf2 is regarded as a promising drug target in the chemoprevention of diseases, including cancer. However, much evidence has accumulated that the beneficial role of Nrf2 in cancer prevention essentially depends on the tight control of its activity. In fact, the deregulation of Nrf2 is a critical determinant in oncogenesis and found in many types of cancer. Therefore, amplified Nrf2 activity has profound effects on the phenotype of tumor cells, including radio/chemoresistance, apoptosis protection, invasiveness, antisenescence, autophagy deficiency, and angiogenicity. The deregulation of Nrf2 can result from various epigenetic and genetic alterations directly affecting Nrf2 control or from the complex interplay of Nrf2 with numerous oncogenic signaling pathways. Additionally, alterations of the cellular environment, eg, during inflammation, contribute to Nrf2 deregulation and its persistent activation. Therefore, the status of Nrf2 as anti- or protumorigenic is defined by many different modalities. A better understanding of these modalities is essential for the safe use of Nrf2 as an activation target for chemoprevention on the one hand and as an inhibition target in cancer therapy on the other. The present review mainly addresses the conditions that promote the oncogenic function of Nrf2 and the resulting consequences providing the rationale for using Nrf2 as a target structure in cancer therapy.

Targeting the NF-E2-related factor 2 pathway: a novel strategy for glioblastoma (review)

Glioblastoma is the most common and malignant subtype among all brain tumors. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential component of cellular defense against a variety of endogenous and exogenous stresses. A marked increase in research over the past few decades focusing on Nrf2 and its role in regulating glioblastoma has revealed the potential value of Nrf2 in the treatment of glioblastoma. In the present review, we discuss a novel framework of Nrf2 in the regulation of glioblastoma and the mechanisms regarding the downregulation of Nrf2 in treating glioblastoma. The candidate mechanisms include direct and indirect means. Direct mechanisms target tumor molecular pathways in order to overcome resistance to chemotherapy and radiotherapy, to inhibit proliferation, to block invasion and migration, to induce apoptosis, to promote differentiation, to enhance autophagy and to target glioblastoma stem cells. Indirect mechanisms target the reaction between glioblastoma cells and the surrounding microenvironment. Overall, the value of the Nrf2 pathway in glioblastoma provides a promising opportunity for new approaches by which to treat glioblastoma.

Redox proteins and radiotherapy

Although conventional radiotherapy can directly damage DNA and other organic molecules within cells, most of the damage and the cytotoxicity of such ionising radiation, comes from the production of ions and free radicals produced via interactions with water. This 'indirect effect', a form of oxidative stress, can be modulated by a variety of systems within cells that are in place to, in normal situations, maintain homeostasis and redox balance. If cancer cells express high levels of antioxidant redox proteins, they may be more resistant to radiation and so targeting such systems may be a profitable strategy to increase therapeutic efficacy of conventional radiotherapy. An overview, with exemplars, of the main systems regulating redox homeostasis is supplied and discussed in relation to their use as prognostic and predictive biomarkers, and how targeting such proteins and systems may increase radiosensitivity and, potentially, improve the radiotherapeutic response.

Hyperdiploid tumor cells increase phenotypic heterogeneity within Glioblastoma tumors

Here we report the identification of a proliferative, viable, and hyperdiploid tumor cell subpopulation present within Glioblastoma (GB) patient tumors. Using xenograft tumor models, we demonstrate that hyperdiploid cell populations are maintained in xenograft tumors and that clonally expanded hyperdiploid cells support tumor formation and progression in vivo. In some patient tumorsphere lines, hyperdiploidy is maintained during long-term culture and in vivo within xenograft tumor models, suggesting that hyperdiploidy can be a stable cell state. In other patient lines hyperdiploid cells display genetic drift in vitro and in vivo, suggesting that in these patients hyperdiploidy is a transient cell state that generates novel phenotypes, potentially facilitating rapid tumor evolution. We show that the hyperdiploid cells are resistant to conventional therapy, in part due to infrequent cell division due to a delay in the G₀/G₁ phase of the cell cycle. Hyperdiploid tumor cells are significantly larger and more metabolically active than euploid cancer cells, and this correlates to an increased sensitivity to the effects of glycolysis inhibition. Together these data identify GB hyperdiploid tumor cells as a potentially important subpopulation of cells that are well positioned to contribute to tumor evolution and disease recurrence in adult brain cancer patients, and suggest tumor metabolism as a promising point of therapeutic intervention against this subpopulation.

Nrf2 is a potential therapeutic target in radioresistance in human cancer

Radiation therapy can effectively kill cancer cells through ROS generation. Cancer cells with upregulated antioxidant systems can develop high radioresistance ability, and the transcription factor NF-E2-related factor 2 (Nrf2) is a key regulator of the antioxidant system. Currently, there are numerous data indicating the important role of Nrf2 in cancer radioresistance. In this review, we summarize the aberrant regulation of Nrf2 in radioresistant cells and discuss the effects and underlying mechanism of Nrf2 in promoting radioresistance. These findings suggest that Nrf2 might be a potential therapeutic target in cancer radiation resistance or a promising radioprotector for normal organs during radiation therapy in the future.