Linking Cancer Metabolic Dysfunction and Genetic Instability through the Lens of Iron Metabolism

Balanced Duality: H2O2-Based Therapy in Cancer and Its Protective Effects on Non-Malignant Tissues

Conventional cancer therapy strategies, although centered around killing tumor cells, often lead to severe side effects on surrounding normal tissues, thus compromising the chronic quality of life in cancer survivors. Hydrogen peroxide (H2O2) is a secondary signaling molecule that has an array of functions in both tumor and normal cells, including the promotion of cell survival pathways and immune cell modulation in the tumor microenvironment. H2O2 is a reactive oxygen species (ROS) crucial in cellular homeostasis and signaling (at concentrations maintained under nM levels), with increased steady-state levels in tumors relative to their normal tissue counterparts. Increased steady-state levels of H2O2 in tumor cells, make them vulnerable to oxidative stress and ultimately, cell death. Recently, H2O2-producing therapies-namely, pharmacological ascorbate and superoxide dismutase mimetics-have emerged as compelling complementary treatment strategies in cancer. Both pharmacological ascorbate and superoxide dismutase mimetics can generate excess H2O2 to overwhelm the impaired H2O2 removal capacity of cancer cells. This review presents an overview of H2O2 metabolism in the physiological and malignant states, in addition to discussing the anti-tumor and normal tissue-sparing mechanism(s) of, and clinical evidence for, two H2O2-based therapies, pharmacological ascorbate and superoxide dismutase mimetics.

The Role of Iron Metabolism in Sepsis-associated Encephalopathy: a Potential Target

Sepsis-associated encephalopathy (SAE) is an acute cerebral dysfunction secondary to infection, and the severity can range from mild delirium to deep coma. Disorders of iron metabolism have been proven to play an important role in a variety of neurodegenerative diseases by inducing cell damage through iron accumulation in glial cells and neurons. Recent studies have found that iron accumulation is also a potential mechanism of SAE. Systemic inflammation can induce changes in the expression of transporters and receptors on cells, especially high expression of divalent metal transporter1 (DMT1) and low expression of ferroportin (Fpn) 1, which leads to iron accumulation in cells. Excessive free Fe2+ can participate in the Fenton reaction to produce reactive oxygen species (ROS) to directly damage cells or induce ferroptosis. As a result, it may be of great help to improve SAE by treatment of targeting disorders of iron metabolism. Therefore, it is important to review the current research progress on the mechanism of SAE based on iron metabolism disorders. In addition, we also briefly describe the current status of SAE and iron metabolism disorders and emphasize the therapeutic prospect of targeting iron accumulation as a treatment for SAE, especially iron chelator. Moreover, drug delivery and side effects can be improved with the development of nanotechnology. This work suggests that treating SAE based on disorders of iron metabolism will be a thriving field.

Mechanisms of Action in FLASH Radiotherapy: A Comprehensive Review of Physicochemical and Biological Processes on Cancerous and Normal Cells

The advent of FLASH radiotherapy (FLASH-RT) has brought forth a paradigm shift in cancer treatment, showcasing remarkable normal cell sparing effects with ultra-high dose rates (>40 Gy/s). This review delves into the multifaceted mechanisms underpinning the efficacy of FLASH effect, examining both physicochemical and biological hypotheses in cell biophysics. The physicochemical process encompasses oxygen depletion, reactive oxygen species, and free radical recombination. In parallel, the biological process explores the FLASH effect on the immune system and on blood vessels in treatment sites such as the brain, lung, gastrointestinal tract, skin, and subcutaneous tissue. This review investigated the selective targeting of cancer cells and the modulation of the tumor microenvironment through FLASH-RT. Examining these mechanisms, we explore the implications and challenges of integrating FLASH-RT into cancer treatment. The potential to spare normal cells, boost the immune response, and modify the tumor vasculature offers new therapeutic strategies. Despite progress in understanding FLASH-RT, this review highlights knowledge gaps, emphasizing the need for further research to optimize its clinical applications. The synthesis of physicochemical and biological insights serves as a comprehensive resource for cell biology, molecular biology, and biophysics researchers and clinicians navigating the evolution of FLASH-RT in cancer therapy.

Quantitative MRI Evaluation of Ferritin Overexpression in Non-Small-Cell Lung Cancer

Cancer cells frequently present elevated intracellular iron levels, which are thought to facilitate an enhanced proliferative capacity. Targeting iron metabolism within cancer cells presents an avenue to enhance therapeutic responses, necessitating the use of non-invasive models to modulate iron manipulation to predict responses. Moreover, the ubiquitous nature of iron necessitates the development of unique, non-invasive markers of metabolic disruptions to develop more personalized approaches and enhance the clinical utility of these approaches. Ferritin, an iron storage enzyme that is often upregulated as a response to iron accumulation, plays a central role in iron metabolism and has been frequently associated with unfavorable clinical outcomes in cancer. Herein, we demonstrate the successful utility, validation, and functionality of a doxycycline-inducible ferritin heavy chain (FtH) overexpression model in H1299T non-small-cell lung cancer (NSCLC) cells. Treatment with doxycycline increased the protein expression of FtH with a corresponding decrease in labile iron in vitro and in vivo, as determined by calcein-AM staining and EPR, respectively. Moreover, a subsequent increase in TfR expression was observed. Furthermore, T2* MR mapping effectively detected FtH expression in our in vivo model. These results demonstrate that T2* relaxation times can be used to monitor changes in FtH expression in tumors with bidirectional correlations depending on the model system. Overall, this study describes the development of an FtH overexpression NSCLC model and its correlation with T2* mapping for potential use in patients to interrogate iron metabolic alterations and predict clinical outcomes.

Cancer Metabolism under Limiting Oxygen Conditions

Molecular oxygen (O2) is essential for cellular bioenergetics and numerous biochemical reactions necessary for life. Solid tumors outgrow the native blood supply and diffusion limits of O2, and therefore must engage hypoxia response pathways that evolved to withstand acute periods of low O2 Hypoxia activates coordinated gene expression programs, primarily through hypoxia inducible factors (HIFs), to support survival. Many of these changes involve metabolic rewiring such as increasing glycolysis to support ATP generation while suppressing mitochondrial metabolism. Since low O2 is often coupled with nutrient stress in the tumor microenvironment, other responses to hypoxia include activation of nutrient uptake pathways, metabolite scavenging, and regulation of stress and growth signaling cascades. Continued development of models that better recapitulate tumors and their microenvironments will lead to greater understanding of oxygen-dependent metabolic reprogramming and lead to more effective cancer therapies.

Magnetic Resonance Imaging of Iron Metabolism with T2* Mapping Predicts an Enhanced Clinical Response to Pharmacologic Ascorbate in Patients with GBM

PURPOSE

Pharmacologic ascorbate (P-AscH-) is hypothesized to be an iron (Fe)-dependent tumor-specific adjuvant to chemoradiation in treating glioblastoma (GBM). This study determined the efficacy of combining P-AscH- with radiation and temozolomide in a phase II clinical trial while simultaneously investigating a mechanism-based, noninvasive biomarker in T2* mapping to predict GBM response to P-AscH- in humans.

PATIENTS AND METHODS

The single-arm phase II clinical trial (NCT02344355) enrolled 55 subjects, with analysis performed 12 months following the completion of treatment. Overall survival (OS) and progression-free survival (PFS) were estimated with the Kaplan-Meier method and compared across patient subgroups with log-rank tests. Forty-nine of 55 subjects were evaluated using T2*-based MRI to assess its utility as an Fe-dependent biomarker.

RESULTS

Median OS was estimated to be 19.6 months [90% confidence interval (CI), 15.7-26.5 months], a statistically significant increase compared with historic control patients (14.6 months). Subjects with initial T2* relaxation < 50 ms were associated with a significant increase in PFS compared with T2*-high subjects (11.2 months vs. 5.7 months, P < 0.05) and a trend toward increased OS (26.5 months vs. 17.5 months). These results were validated in preclinical in vitro and in vivo model systems.

CONCLUSIONS

P-AscH- combined with temozolomide and radiotherapy has the potential to significantly enhance GBM survival. T2*-based MRI assessment of tumor iron content is a prognostic biomarker for GBM clinical outcomes. See related commentary by Nabavizadeh and Bagley, p. 255.

Depletion of Labile Iron Induces Replication Stress and Enhances Responses to Chemoradiation in Non-Small-Cell Lung Cancer

The intracellular redox-active labile iron pool (LIP) is weakly chelated and available for integration into the iron metalloproteins that are involved in diverse cellular processes, including cancer cell-specific metabolic oxidative stress. Abnormal iron metabolism and elevated LIP levels are linked to the poor survival of lung cancer patients, yet the underlying mechanisms remain unclear. Depletion of the LIP in non-small-cell lung cancer cell lines using the doxycycline-inducible overexpression of the ferritin heavy chain (Ft-H) (H1299 and H292), or treatment with deferoxamine (DFO) (H1299 and A549), inhibited cell growth and decreased clonogenic survival. The Ft-H overexpression-induced inhibition of H1299 and H292 cell growth was also accompanied by a significant delay in transit through the S-phase. In addition, both Ft-H overexpression and DFO in H1299 resulted in increased single- and double-strand DNA breaks, supporting the involvement of replication stress in the response to LIP depletion. The Ft-H and DFO treatment also sensitized H1299 to VE-821, an inhibitor of ataxia telangiectasis and Rad2-related (ATR) kinase, highlighting the potential of LIP depletion, combined with DNA damage response modifiers, to alter lung cancer cell responses. In contrast, only DFO treatment effectively reduced the LIP, clonogenic survival, cell growth, and sensitivity to VE-821 in A549 non-small-cell lung cancer cells. Importantly, the Ft-H and DFO sensitized both H1299 and A549 to chemoradiation in vitro, and Ft-H overexpression increased the efficacy of chemoradiation in vivo in H1299. These results support the hypothesis that the depletion of the LIP can induce genomic instability, cell death, and potentiate therapeutic responses to chemoradiation in NSCLC.

JAK/STAT signaling and cellular iron metabolism in hepatocellular carcinoma: therapeutic implications

Iron metabolism plays a crucial role in the development and progression of hepatocellular carcinoma (HCC), the most common type of primary liver cancer. Iron is an essential micronutrient that is involved in many physiological processes, including oxygen transport, DNA synthesis, and cellular growth and differentiation. However, excessive iron accumulation in the liver has been linked to oxidative stress, inflammation, and DNA damage, which can increase the risk of HCC. Studies have shown that iron overload is common in patients with HCC and that it is associated with a poor prognosis and reduced survival rates. Various iron metabolism-related proteins and signaling pathways such as the JAK/STAT pathway are dysregulated in HCC. Moreover, reduced hepcidin expression was reported to promote HCC in a JAK/STAT pathway-dependent manner. Therefore, it is important to understand the crosstalk between iron metabolism and the JAK/STAT pathway to prevent or treat iron overload in HCC. Iron chelators can bind to iron and remove it from the body, but its effect on JAK/STAT pathway is unclear. Also, HCC can be targeted by using the JAK/STAT pathway inhibitors, but their effect on hepatic iron metabolism is not known. In this review, for the first time, we focus on the role of the JAK/STAT signaling pathway in regulating cellular iron metabolism and its association with the development of HCC. We also discuss novel pharmacological agents and their therapeutic potential in manipulating iron metabolism and JAK/STAT signaling in HCC.

Machine learning-aided metallomic profiling in serum and urine of thyroid cancer patients and its environmental implications

The incidence rate of thyroid cancer has been growing worldwide. Thyroid health is closely related with multiple trace metals, and the nutrients are essential in maintaining thyroid function while the contaminants can disturb thyroid morphology and homeostasis. In this study, we conducted metallomic analysis in thyroid cancer patients (n = 40) and control subjects (n = 40) recruited in Shenzhen, China with a high incidence of thyroid cancer. We found significant alterations in serumal and urinary metallomic profiling (including Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Cd, I, Ba, Tl, and Pb) and elemental correlative patterns between thyroid cancer patients and controls. Additionally, we also measured the serum Cu isotopic composition and found a multifaceted disturbance in Cu metabolism in thyroid disease patients. Based on the metallome variations, we built and assessed the thyroid cancer-predictive performance of seven machine learning algorithms. Among them, the Random Forest model performed the best with the accuracy of 1.000, 0.858, and 0.813 on the training, 5-fold cross-validation, and test set, respectively. The high performance of machine learning has demonstrated the great promise of metallomic analysis in the identification of thyroid cancer. Then, the Shapley Additive exPlanations approach was used to further interpret the variable contributions of the model and it showed that serum Pb contributed the most in the identification process. To the best of our knowledge, this is the first study that combines machine learning and metallome data for cancer identification, and it supports the indication of environmental heavy metal-related thyroid cancer etiology.

Convergent Total Synthesis of Exochelin 772SM

A convergent total synthesis of the natural mycobacterial iron chelator desferri-exochelin 772SM (D-EXO) is described. The synthetic procedure proceeds in 11 steps in the longest linear sequence, with an overall yield of 8.6%. The described procedure uses cheap starting materials and requires a limited number of chromatographic purifications. The concise strategy divides the exochelin into five key building blocks, allowing easy alternation of each single building block. Herein, the presented synthetic strategy is well suited to facilitate the synthesis of analogues and medicinal chemistry development efforts in a time- and resource-efficient manner.

Evaluating the iron chelator function of sirtinol in non-small cell lung cancer

A distinctive feature of cancer is the upregulation of sirtuin proteins. Sirtuins are class III NAD+-dependent deacetylases involved in cellular processes such as proliferation and protection against oxidative stress. SIRTs 1 and 2 are also overexpressed in several types of cancers including non-small cell lung cancer (NSCLC). Sirtinol, a sirtuin (SIRT) 1 and 2 specific inhibitor, is a recent anti-cancer agent that is cytotoxic against several types of cancers including NSCLC. Thus, sirtuins 1 and 2 represent valuable targets for cancer therapy. Recent studies show that sirtinol functions as a tridentate iron chelator by binding Fe3+ with 3:1 stoichiometry. However, the biological consequences of this function remain unexplored. Consistent with preliminary literature, we show that sirtinol can deplete intracellular labile iron pools in both A549 and H1299 non-small cell lung cancer cells acutely. Interestingly, a temporal adaptive response occurs in A549 cells as sirtinol enhances transferrin receptor stability and represses ferritin heavy chain translation through impaired aconitase activity and apparent IRP1 activation. This effect was not observed in H1299 cells. Holo-transferrin supplementation significantly enhanced colony formation in A549 cells while increasing sirtinol toxicity. This effect was not observed in H1299 cells. The results highlight the fundamental genetic differences that may exist between H1299 and A549 cells and offer a novel mechanism of how sirtinol kills NSCLC cells.

Magnetite nanoparticles as a kinetically favorable source of iron to enhance GBM response to chemoradiosensitization with pharmacological ascorbate

Ferumoxytol (FMX) is an FDA-approved magnetite (Fe3O4) nanoparticle used to treat iron deficiency anemia that can also be used as an MR imaging agent in patients that can't receive gadolinium. Pharmacological ascorbate (P-AscH-; IV delivery; plasma levels ≈ 20 mM) has shown promise as an adjuvant to standard of care chemo-radiotherapy in glioblastoma (GBM). Since ascorbate toxicity mediated by H2O2 is enhanced by Fe redox cycling, the current study determined if ascorbate catalyzed the release of ferrous iron (Fe2+) from FMX for enhancing GBM responses to chemo-radiotherapy. Ascorbate interacted with Fe3O4 in FMX to produce redox-active Fe2+ while simultaneously generating increased H2O2 fluxes, that selectively enhanced GBM cell killing (relative to normal human astrocytes) as opposed to a more catalytically active Fe complex (EDTA-Fe3+) in an H2O2 - dependent manner. In vivo, FMX was able to improve GBM xenograft tumor control when combined with pharmacological ascorbate and chemoradiation in U251 tumors that were unresponsive to pharmacological ascorbate therapy. These data support the hypothesis that FMX combined with P-AscH- represents a novel combined modality therapeutic approach to enhance cancer cell selective chemoradiosentization in the management of glioblastoma.

What Is the Correlation between Preeclampsia and Cancer? The Important Role of Tachykinins and Transition Metal Ions

Metal ions are irreplaceable in many biological processes. They are components of numerous metalloproteins and serve as cofactors or structural elements for enzymes. Interestingly, iron, copper and zinc play important roles in accelerating or preventing neoplastic cell transformation. Noteworthily, a lot of proliferative and invasive mechanisms are exploited by both malignant tumors and pregnancy. Cancer cells, as well as developing placenta cells, create a microenvironment supportive of immunologic privilege and angiogenesis. Therefore, pregnancy and cancer progression share many similarities. Moreover, during preeclampsia and cancer, significant changes in relevant trace element concentrations, tachykinin levels, expressions of neurokinin receptors, oxidative stress and angiogenic imbalance are observed. This sheds a new light on the role of metal ions and tachykinins in cancer progression and pregnancy, especially in preeclamptic women.

Dietary Antioxidant-Constructed Nanodrugs Can High-Efficiently Kill Cancer Cells while Protecting Noncancer Cells

Despite great advances, the development of cancer drugs that can efficiently kill cancer cells while protecting noncancer cells has not been achieved. By using only dietary antioxidants vitamin C (VC) and (R)-(+)-lipoic acid (LA), we herein develop a nanodrug VC@cLAV featuring the above function. After entering cells, cLAV dissociates into LA and DHLA (dihydrolipoic acid, reduced form of LA) and releases VC and DHA (dehydroascorbate, oxidized form of VC). In cancer cells, the two redox pairs recycle each other and dramatically promote the intracellular reactive oxygen species production to kill cancer cells at low doses comparable to cytotoxic drugs. Oppositely in noncancer cells, the LA/DHLA and VC/DHA pairs exert anti-oxidant action to actively protect the organism by preventing the normal cells from oxidative stress and repairing cells suffering from oxidative stress. When compared with the first-line cytotoxic drug, VC@cLAV displayed superior therapeutic outcomes yet without side effects in diverse tumor models including patient-derived xenograft (PDX). This drug with efficient cancer cell killing and noncancer cell protection represents a new cancer therapy.

Iron-Sulfur Clusters: A Key Factor of Regulated Cell Death in Cancer

Iron-sulfur clusters are ancient cofactors that play crucial roles in myriad cellular functions. Recent studies have shown that iron-sulfur clusters are closely related to the mechanisms of multiple cell death modalities. In addition, numerous previous studies have demonstrated that iron-sulfur clusters play an important role in the development and treatment of cancer. This review first summarizes the close association of iron-sulfur clusters with cell death modalities such as ferroptosis, cuprotosis, PANoptosis, and apoptosis and their potential role in cancer activation and drug resistance. This review hopes to generate new cancer therapy ideas and overcome drug resistance by modulating iron-sulfur clusters.

Ferroptosis: A New Development Trend in Periodontitis

Periodontitis is a chronic inflammatory disease associated with bacterial biofilm. It is characterized by loss of periodontal support tissue and has long been considered as a "silent disease". Because it is difficult to prevent and has a health impact that can not be ignored, researchers have been focusing on a mechanism-based treatment model. Ferroptosis is an iron-dependent regulatory form of cell death, that directly or indirectly affects glutathione peroxidase through different signaling pathways, resulting in a decrease in cell antioxidant capacity, accumulation of reactive oxygen species and lipid peroxidation, which cause oxidative cell death and tissue damage. Recently, some studies have proven that iron overload, oxidative stress, and lipid peroxidation exist in the process of periodontitis. Based on this, this article reviews the relationship between periodontitis and ferroptosis, in order to provide a theoretical reference for future research on the prevention and treatment of periodontal disease.

Boosting cisplatin chemotherapy by nanomotor-enhanced tumor penetration and DNA adducts formation

Despite many nano-based strategies devoted to delivering cisplatin for tumor therapy, its clinical benefits are compromised by poor tissue penetration and limited DNA adducts formation of the drug. Herein, a cisplatin loading nanomotor based janus structured Ag-polymer is developed for cisplatin delivery of deeper tissue and increased DNA adducts formation. The nanomotor displayed a self‐propelled tumor penetration fueled by hydrogen peroxide (H₂O₂) in tumor tissues, which is catalytically decomposed into a large amount of oxygen bubbles by Ag nanoparticles (NPs). Notably, cisplatin could elevate the intracellular H₂O₂ level through cascade reactions, further promote the degradation of Ag NPs accompanied with the Ag⁺ release, which could downregulate intracellular Cl⁻ through the formation of AgCl precipitate, thereby enhancing cisplatin dechlorination and Pt–DNA formation. Moreover, polymer can also inhibit the activity of ALKBH2 (a Fe²⁺-dependent DNA repair enzyme) by chelating intracellular Fe²⁺ to increase the proportion of irreparable Pt–DNA cross-links. It is found that deep tissue penetration, as well as the increased formation and maintenance of Pt–DNA adducts induced by the nanomotor afford 80% of tumor growth inhibition with negligible toxicity. This work provides an important perspective of resolving chemotherapeutic barriers for boosting cisplatin therapy.

Detection of Ferritin Expression in Soft Tissue Sarcomas With MRI: Potential Implications for Iron Metabolic Therapy

BACKGROUND

Cancer cells often have altered iron metabolism relative to non-malignant cells with increased transferrin receptor and ferritin expression. Targeting iron regulatory proteins as part of a cancer therapy regimen is currently being investigated in various malignancies. Anti-cancer therapies that exploit the differences in iron metabolism between malignant and non-malignant cells (e.g. pharmacological ascorbate and iron chelation therapy) have shown promise in various cancers, including glioblastoma, lung, and pancreas cancers. Non-invasive techniques that probe tissue iron metabolism may provide valuable information for the personalization of iron-based cancer therapies. T₂* mapping is a clinically available MRI technique that assesses tissue iron content in the heart and liver. We aimed to investigate the capacity of T₂* mapping to detect iron stores in soft tissue sarcomas (STS).

METHODS

In this study, we evaluated T₂* relaxation times ex vivo in five STS samples from subjects enrolled on a phase Ib/IIa clinical trial combining pharmacological ascorbate with neoadjuvant radiation therapy. Iron protein expression levels (ferritin, transferrin receptor, iron response protein 2) were evaluated by Western blot analysis. Bioinformatic data relating clinical outcomes in STS patients and iron protein expression levels were evaluated using the KMplotter database.

RESULTS

There was a high level of inter-subject variability in the expression of iron protein and T₂* relaxation times. We identified that T₂* relaxation time is capable of accurately detecting ferritin-heavy chain expression (r = -0.96) in these samples. Bioinformatic data acquired from the KMplot database revealed that transferrin receptor and iron-responsive protein 2 may be negative prognostic markers while ferritin expression may be a positive prognostic marker in the management of STS.

CONCLUSION

These data suggest that targeting iron regulatory proteins may provide a therapeutic approach to enhance STS management. Additionally, T₂* mapping has the potential to be used a clinically accessible, non-invasive marker of STS iron regulatory protein expression and influence cancer therapy decisions that warrants further investigation. Level of Evidence: IV.

Neuronal Death Mechanisms and Therapeutic Strategy in Ischemic Stroke

Ischemic stroke caused by intracranial vascular occlusion has become increasingly prevalent with considerable mortality and disability, which gravely burdens the global economy. Current relatively effective clinical treatments are limited to intravenous alteplase and thrombectomy. Even so, patients still benefit little due to the short therapeutic window and the risk of ischemia/reperfusion injury. It is therefore urgent to figure out the neuronal death mechanisms following ischemic stroke in order to develop new neuroprotective strategies. Regarding the pathogenesis, multiple pathological events trigger the activation of cell death pathways. Particular attention should be devoted to excitotoxicity, oxidative stress, and inflammatory responses. Thus, in this article, we first review the principal mechanisms underlying neuronal death mediated by these significant events, such as intrinsic and extrinsic apoptosis, ferroptosis, parthanatos, pyroptosis, necroptosis, and autophagic cell death. Then, we further discuss the possibility of interventions targeting these pathological events and summarize the present pharmacological achievements.

The Role of Iron in Cancer Progression

Iron is an essential trace element for the human body, and its deficiency or excess can induce a variety of biological processes. Plenty of evidences have shown that iron metabolism is closely related to the occurrence and development of tumors. In addition, iron plays an important role in cell death, which is very important for the development of potential strategies for tumor treatment. Here, we reviewed the latest research about iron metabolism disorders in various types of tumors, the functions and properties of iron in ferroptosis and ferritinophagy, and new opportunities for iron-based on treatment methods for tumors, providing more information regarding the prevention and treatment of tumors.

Utilization of Pharmacological Ascorbate to Enhance Hydrogen Peroxide-Mediated Radiosensitivity in Cancer Therapy

Interest in the use of pharmacological ascorbate as a treatment for cancer has increased considerably since it was introduced by Cameron and Pauling in the 1970s. Recently, pharmacological ascorbate has been used in preclinical and early-phase clinical trials as a selective radiation sensitizer in cancer. The results of these studies are promising. This review summarizes data on pharmacological ascorbate (1) as a safe and efficacious adjuvant to cancer therapy; (2) as a selective radiosensitizer of cancer via a mechanism involving hydrogen peroxide; and (3) as a radioprotector in normal tissues. Additionally, we present new data demonstrating the ability of pharmacological ascorbate to enhance radiation-induced DNA damage in glioblastoma cells, facilitating cancer cell death. We propose that pharmacological ascorbate may be a general radiosensitizer in cancer therapy and simultaneously a radioprotector of normal tissue.

Iron-Sulfur Cluster Biogenesis as a Critical Target in Cancer

Cancer cells preferentially accumulate iron (Fe) relative to non-malignant cells; however, the underlying rationale remains elusive. Iron-sulfur (Fe-S) clusters are critical cofactors that aid in a wide variety of cellular functions (e.g., DNA metabolism and electron transport). In this article, we theorize that a differential need for Fe-S biogenesis in tumor versus non-malignant cells underlies the Fe-dependent cell growth demand of cancer cells to promote cell division and survival by promoting genomic stability via Fe-S containing DNA metabolic enzymes. In this review, we outline the complex Fe-S biogenesis process and its potential upregulation in cancer. We also discuss three therapeutic strategies to target Fe-S biogenesis: (i) redox manipulation, (ii) Fe chelation, and (iii) Fe mimicry.

A Combined Drug Treatment That Reduces Mitochondrial Iron and Reactive Oxygen Levels Recovers Insulin Secretion in NAF-1-Deficient Pancreatic Cells

Decreased insulin secretion, associated with pancreatic β-cell failure, plays a critical role in many human diseases including diabetes, obesity, and cancer. While numerous studies linked β-cell failure with enhanced levels of reactive oxygen species (ROS), the development of diabetes associated with hereditary conditions that result in iron overload, e.g., hemochromatosis, Friedreich's ataxia, and Wolfram syndrome type 2 (WFS-T2; a mutation in CISD2, encoding the [2Fe-2S] protein NAF-1), underscores an additional link between iron metabolism and β-cell failure. Here, using NAF-1-repressed INS-1E pancreatic cells, we observed that NAF-1 repression inhibited insulin secretion, as well as impaired mitochondrial and ER structure and function. Importantly, we found that a combined treatment with the cell permeant iron chelator deferiprone and the glutathione precursor N-acetyl cysteine promoted the structural repair of mitochondria and ER, decreased mitochondrial labile iron and ROS levels, and restored glucose-stimulated insulin secretion. Additionally, treatment with the ferroptosis inhibitor ferrostatin-1 decreased cellular ROS formation and improved cellular growth of NAF-1 repressed pancreatic cells. Our findings reveal that suppressed expression of NAF-1 is associated with the development of ferroptosis-like features in pancreatic cells, and that reducing the levels of mitochondrial iron and ROS levels could be used as a therapeutic avenue for WFS-T2 patients.

The epigenetic and morphogenetic effects of molecular oxygen and its derived reactive species in development

The development of multicellular organisms involves the unpacking of a complex genetic program. Extensive characterization of discrete developmental steps has revealed the genetic program is controlled by an epigenetic state. Shifting the epigenome is a group of epigenetic enzymes that modify DNA and proteins to regulate cell type specific gene expression. While the role of these modifications in development has been established, the input(s) responsible for electing changes in the epigenetic state remains unknown. Development is also associated with dynamic changes in cellular metabolism, redox, free radical production, and oxygen availability. It has previously been postulated that these changes are causal in development by affecting gene expression. This suggests that oxygen is a morphogenic compound that impacts the removal of epigenetic marks. Likewise, metabolism and reactive oxygen species influence redox signaling through iron and glutathione to limit the availability of key epigenetic cofactors such as α-ketoglutarate, ascorbate, NAD⁺ and S-adenosylmethionine. Given the close relationship between these cofactors and epigenetic marks it seems likely that the two are linked. Here we describe how changing these inputs might affect the epigenetic state during development to drive gene expression. Combined, these cofactors and reactive oxygen species constitute the epigenetic landscape guiding cells along differing developmental paths.

Utilization of redox modulating small molecules that selectively act as pro-oxidants in cancer cells to open a therapeutic window for improving cancer therapy

There is a rapidly growing body of literature supporting the notion that differential oxidative metabolism in cancer versus normal cells represents a metabolic frailty that can be exploited to open a therapeutic window into cancer therapy. These cancer cell-specific metabolic frailties may be amenable to manipulation with non-toxic small molecule redox active compounds traditionally thought to be antioxidants. In this review we describe the potential mechanisms and clinical applicability in cancer therapy of four small molecule redox active agents: melatonin, vitamin E, selenium, and vitamin C. Each has shown the potential to have pro-oxidant effects in cancer cells while retaining antioxidant activity in normal cells. This dichotomy can be exploited to improve responses to radiation and chemotherapy by opening a therapeutic window based on a testable biochemical rationale amenable to confirmation with biomarker studies during clinical trials. Thus, the unique pro-oxidant/antioxidant properties of melatonin, vitamin E, selenium, and vitamin C have the potential to act as effective adjuvants to traditional cancer therapies, thereby improving cancer patient outcomes.

The Biological Function, Mechanism, and Clinical Significance of m6A RNA Modifications in Head and Neck Carcinoma: A Systematic Review

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers, yet the molecular mechanisms underlying its onset and development have not yet been fully elucidated. Indeed, an in-depth understanding of the potential molecular mechanisms underlying HNSCC oncogenesis may aid the development of better treatment strategies. Recent epigenetic studies have revealed that the m6A RNA modification plays important roles in HNSCC. In this review, we summarize the role of m6A modification in various types of HNSCC, including thyroid, nasopharyngeal, hypopharyngeal squamous cell, and oral carcinoma. In addition, we discuss the regulatory roles of m6A in immune cells within the tumor microenvironment, as well as the potential molecular mechanisms. Finally, we review the development of potential targets for treating cancer based on the regulatory functions of m6A, with an aim to improving targeted therapies for HNSCC. Together, this review highlights the important roles that m6A modification plays in RNA synthesis, transport, and translation, and demonstrates that the regulation of m6A-related proteins can indirectly affect mRNA and ncRNA function, thus providing a novel strategy for reengineering intrinsic cell activity and developing simpler interventions to treat HNSCC.

Nanoneedle-Based Materials for Intracellular Studies

Nanoneedles, defined as high aspect ratio structures with tip diameters of 5 to approximately 500 nm, are uniquely able to interface with the interior of living cells. Their nanoscale dimensions mean that they are able to penetrate the plasma membrane with minimal disruption of normal cellular functions, allowing researchers to probe the intracellular space and deliver or extract material from individual cells. In the last decade, a variety of strategies have been developed using nanoneedles, either singly or as arrays, to investigate the biology of cancer cells in vitro and in vivo. These include hollow nanoneedles for soluble probe delivery, nanocapillaries for single-cell biopsy, nano-AFM for direct physical measurements of cytosolic proteins, and a wide range of fluorescent and electrochemical nanosensors for analyte detection. Nanofabrication has improved to the point that nanobiosensors can detect individual vesicles inside the cytoplasm, delineate tumor margins based on intracellular enzyme activity, and measure changes in cell metabolism almost in real time. While most of these applications are currently in the proof-of-concept stage, nanoneedle technology is poised to offer cancer biologists a powerful new set of tools for probing cells with unprecedented spatial and temporal resolution.

Magnetic resonance imaging (MRI) of pharmacological ascorbate-induced iron redox state as a biomarker in subjects undergoing radio-chemotherapy

Pharmacological ascorbate (P-AscH^-) combined with standard of care (SOC) radiation and temozolomide is being evaluated in a phase 2 clinical trial (NCT02344355) in the treatment of glioblastoma (GBM). Previously published data demonstrated that paramagnetic iron (Fe³⁺) catalyzes ascorbate's oxidation to form diamagnetic iron (Fe²⁺). Because paramagnetic Fe³⁺ may influence relaxation times observed in MR imaging, quantitative MR imaging of P-AscH^--induced changes in redox-active Fe was assessed as a biomarker for therapy response. Gel phantoms containing either Fe³⁺ or Fe²⁺ were imaged with T2* and quantitative susceptibility mapping (QSM). Fifteen subjects receiving P-AscH^- plus SOC underwent T2* and QSM imaging four weeks into treatment. Subjects were scanned: pre-P-AscH^- infusion, post-P-AscH^- infusion, and post-radiation (3-4 h between scans). Changes in T2* and QSM relaxation times in tumor and normal tissue were calculated and compared to changes in Fe³⁺ and Fe²⁺ gel phantoms. A GBM mouse model was used to study the relationship between the imaging findings and the labile iron pool. Phantoms containing Fe³⁺ demonstrated detectable changes in T2* and QSM relaxation times relative to Fe²⁺ phantoms. Compared to pre-P-AscH^-, GBM T2* and QSM imaging were significantly changed post-P-AscH^- infusion consistent with conversion of Fe³⁺ to Fe²⁺. No significant changes in T2* or QSM were observed in normal brain tissue. There was moderate concordance between T2* and QSM changes in both progression free survival and overall survival. The GBM mouse model showed similar results with P-AscH^- inducing greater changes in tumor labile iron pools compared to the normal tissue. CONCLUSIONS: T2* and QSM MR-imaging responses are consistent with P-AscH^- reducing Fe³⁺ to Fe²⁺, selectively in GBM tumor volumes and represent a potential biomarker of response. This study is the first application using MR imaging in humans to measure P-AscH^--induced changes in redox-active iron.

YTHDF1-enhanced iron metabolism depends on TFRC m6A methylation

Background: Among head and neck squamous cell carcinomas (HNSCCs), hypopharyngeal squamous cell carcinoma (HPSCC) has the worst prognosis. Iron metabolism, which plays a crucial role in tumor progression, is mainly regulated by alterations to genes and post-transcriptional processes. The recent discovery of the N6-methyladenosine (m⁶A) modification has expanded the realm of previously undiscovered post-transcriptional gene regulation mechanisms in eukaryotes. Many studies have demonstrated that m⁶A methylation represents a distinct layer of epigenetic deregulation in carcinogenesis and tumor proliferation. However, the status of m⁶A modification and iron metabolism in HPSCC remains unknown.

Methods: Bioinformatics analysis, sample analysis, and transcriptome sequencing were performed to evaluate the correlation between m⁶A modification and iron metabolism. Iron metabolic and cell biological analyses were conducted to evaluate the effect of the m⁶A reader YTHDF1 on HPSCC proliferation and iron metabolism. Transcriptome-wide m⁶A-seq and RIP-seq data were mapped to explore the molecular mechanism of YTHDF1 function in HPSCC.

Results: YTHDF1 was found to be closely associated with ferritin levels and intratumoral iron concentrations in HPSCC patients at Sir Run Run Shaw Hospital. YTHDF1 induced-HPSCC tumorigenesis depends on iron metabolism in vivo in vitro. Mechanistically, YTHDF1 methyltransferase domain interacts with the 3'UTR and 5'UTR of TRFC mRNA, then further positively regulates translation of m⁶A-modified TFRC mRNA. Gain-of-function and loss-of-function analyses validated the finding showing that TFRC is a crucial target gene for YTHDF1-mediated increases in iron metabolism.

Conclusion: YTHDF1 enhanced TFRC expression in HPSCC through an m⁶A-dependent mechanism. From a therapeutic perspective, targeting YTHDF1 and TFRC-mediated iron metabolism may be a promising strategy for HPSCC.

Spectroscopic study of in situ-formed metallocomplexes of proton pump inhibitors in water

Proton pump inhibitors, such as omeprazole, pantoprazole and lansoprazole, are an important group of clinically used drugs. Generally, they are considered safe without direct toxicity. Nevertheless, their long-term use can be associated with a higher risk of some serious pathological states (e.g. amnesia and oncological and neurodegenerative states). It is well known that dysregulation of the metabolism of transition metals (especially iron ions) plays a significant role in these pathological states and that the above drugs can form complexes with metal ions. However, to the best of our knowledge, this phenomenon has not yet been described in water systems. Therefore, we studied the interaction between these drugs and transition metal ions in the surrounding water environment (water/DMSO, 99:1, v/v) by absorption spectroscopy. In the presence of Fe(III), a strong redshift was observed, and more importantly, the affinities of the drugs (represented as binding constants) were strong enough, especially in the case of omeprazole, so that the formation of a metallocomplex cannot be excluded during the explanation of their side effects.

Iron chelators in cancer therapy

Iron chelators have long been a target of interest as anticancer agents. Iron is an important cellular resource involved in cell replication, metabolism and growth. Iron metabolism is modulated in cancer cells reflecting their increased replicative demands. Originally, iron chelators were first developed for use in iron overload disorders, however, their potential as anticancer agents has been gaining increasing interest. This is due, in part, to the downstream effects of iron depletion such as the inhibition of proliferation through ribonucleotide reductase activity. Additionally, some chelators form redox active metal complexes with iron resulting in the production of reactive oxygen species and oxidative stress. Newer synthetic iron chelators such as Deferasirox, Triapine and di-2-pyridylketone-4,4,-dimethyl-3-thiosemicrbazone (Dp44mt) have improved pharmacokinetic properties over the older chelator Deferoxamine. This review examines and discusses the various iron chelators that have been trialled for cancer therapy including both preclinical and clinical studies. The successes and shortcomings of each of the chelators and their use in combination therapies are highlighted and future potential in the cancer therapy world is considered.

Photodynamic therapy regulates fate of cancer stem cells through reactive oxygen species

Photodynamic therapy (PDT) is an effective and promising cancer treatment. PDT directly generates reactive oxygen species (ROS) through photochemical reactions. This oxygen-dependent exogenous ROS has anti-cancer stem cell (CSC) effect. In addition, PDT may also increase ROS production by altering metabolism, endoplasmic reticulum stress, or potential of mitochondrial membrane. It is known that the half-life of ROS in PDT is short, with high reactivity and limited diffusion distance. Therefore, the main targeting position of PDT is often the subcellular localization of photosensitizers, which is helpful for us to explain how PDT affects CSC characteristics, including differentiation, self-renewal, apoptosis, autophagy, and immunogenicity. Broadly speaking, excess ROS will damage the redox system and cause oxidative damage to molecules such as DNA, change mitochondrial permeability, activate unfolded protein response, autophagy, and CSC resting state. Therefore, understanding the molecular mechanism by which ROS affect CSCs is beneficial to improve the efficiency of PDT and prevent tumor recurrence and metastasis. In this article, we review the effects of two types of photochemical reactions on PDT, the metabolic processes, and the biological effects of ROS in different subcellular locations on CSCs.

Emerging strategies to target cancer metabolism and improve radiation therapy outcomes

Cancer-specific metabolic changes support the anabolic needs of the rapidly growing tumor, maintain a favorable redox balance, and help cells adapt to microenvironmental stresses like hypoxia and nutrient deprivation. Radiation is extensively applied in a large number of cancer treatment protocols but despite its curative potential, radiation resistance and treatment failures pose a serious problem. Metabolic control of DNA integrity and genomic stability can occur through multiple processes, encompassing cell cycle regulation, nucleotide synthesis, epigenetic regulation of gene activity, and antioxidant defenses. Given the important role of metabolic pathways in oxidative damage responses, it is necessary to assess the potential for tumor-specific radiosensitization by novel metabolism-targeted therapies. Additionally, there are opportunities to identify molecular and functional biomarkers of vulnerabilities to combination treatments, which could then inform clinical decisions. Here, we present a curated list of metabolic pathways in the context of ionizing radiation responses. Glutamine metabolism influences DNA damage responses by mechanisms such as synthesis of nucleotides for DNA repair or of glutathione for ROS detoxification. Repurposed oxygen consumption inhibitors have shown promising radiosensitizing activity against murine model tumors and are now in clinical trials. Production of 2-hydroxy glutarate by isocitrate dehydrogenase1/2 neomorphic oncogenic mutants interferes with the function of α-ketoglutarate-dependent enzymes and modulates Ataxia Telangiectasia Mutated (ATM) signaling and glutathione pools. Radiation-induced oxidative damage to membrane phospholipids promotes ferroptotic cell loss and cooperates with immunotherapies to improve tumor control. In summary, there are opportunities to enhance the efficacy of radiotherapy by exploiting cell-inherent vulnerabilities and dynamic microenvironmental components of the tumor.

Understanding Metal Dynamics Between Cancer Cells and Macrophages: Competition or Synergism?

Metal ions, such as selenium, copper, zinc, and iron are naturally present in the environment (air, drinking water, and food) and are vital for cellular functions at chemical, molecular, and biological levels. These trace elements are involved in various biochemical reactions by acting as cofactors for many enzymes and control important biological processes by binding to the receptors and transcription factors. Moreover, they are essential for the stabilization of the cellular structures and for the maintenance of genome stability. A body of preclinical and clinical evidence indicates that dysregulation of metal homeostasis, both at intracellular and tissue level, contributes to the pathogenesis of many different types of cancer. These trace minerals play a crucial role in preventing or accelerating neoplastic cell transformation and in modulating the inflammatory and pro-tumorigenic response in immune cells, such as macrophages, by controlling a plethora of metabolic reactions. In this context, macrophages and cancer cells interact in different manners and some of these interactions are modulated by availability of metals. The current review discusses the new findings and focuses on the involvement of these micronutrients in metabolic and cellular signaling mechanisms that influence macrophage functions, onset of cancer and its progression. An improved understanding of "metallic" cross-talk between macrophages and cancer cells may pave the way for innovative pharmaceutical or dietary interventions in order to restore the balance of these trace elements and also strengthen the chemotherapeutic treatment.

Hypoxia-activated nanomedicines for effective cancer therapy

Hypoxia, a common characteristic in solid tumors, is found in phenotypically aggressive cancers that display resistance to typical cancer interventions. Due to its important role in tumor progression, tumor hypoxia has been considered as a primary target for cancer diagnosis and treatment. An advantage of hypoxia-activated nanomedicines is that they are inactive in normoxic cells. In hypoxic tumor tissues and cells, these nanomedicines undergo reduction by activated enzymes (usually through 1 or 2 electron oxidoreductases) to produce cytotoxic substances. In this review, we will focus on approaches to design nanomedicines that take advantage of tumor hypoxia. These approaches include: i) inhibitors of hypoxia-associated signaling pathways; ii) prodrugs activated by hypoxia; iii) nanocarriers responsive to hypoxia, and iv) bacteria mediated hypoxia targeting therapy. These strategies have guided and will continue to guide nanoparticle design in the near future. These strategies have the potential to overcome tumor heterogeneity to improve the efficiency of radiotherapy, chemotherapy and diagnosis.

Metabolic Reprogramming and Vulnerabilities in Cancer

Metabolic programs are rewired in tumors to support growth, progression, and immune evasion. A wealth of work in the past decade has delineated how these metabolic rearrangements are facilitated by signaling pathways downstream of oncogene activation and tumor suppressor loss. More recently, this field has expanded to include metabolic interactions among the diverse cell types that exist within a tumor and how this impacts the immune system. In this special issue, 17 review articles discuss these phenomena, and, alongside four original research manuscripts, the vulnerabilities associated with deregulated metabolic programming are highlighted and examined.

Magnetic Silica-Coated Iron Oxide Nanochains as Photothermal Agents, Disrupting the Extracellular Matrix, and Eradicating Cancer Cells

Cancerous cells and the tumor microenvironment are among key elements involved in cancer development, progression, and resistance to treatment. In order to tackle the cells and the extracellular matrix, we herein propose the use of a class of silica-coated iron oxide nanochains, which have superior magnetic responsiveness and can act as efficient photothermal agents. When internalized by different cancer cell lines and normal (non-cancerous) cells, the nanochains are not toxic, as assessed on 2D and 3D cell culture models. Yet, upon irradiation with near infrared light, the nanochains become efficient cytotoxic photothermal agents. Besides, not only do they generate hyperthermia, which effectively eradicates tumor cells in vitro, but they also locally melt the collagen matrix, as we evidence in real-time, using engineered cell sheets with self-secreted extracellular matrix. By simultaneously acting as physical (magnetic and photothermal) effectors and chemical delivery systems, the nanochain-based platforms offer original multimodal possibilities for prospective cancer treatment, affecting both the cells and the extracellular matrix.

Systematic analysis of concentrations of 52 elements in tumor and counterpart normal tissues of patients with non-small cell lung cancer

BACKGROUND

Many studies have documented the abnormal concentrations of major/trace elements in serum or malignant tissues of patients, but very few works systematically tested the concentrations of elements in tumor tissues in comparison with paired adjacent normal tissues from the same patients.

METHODS

Tumor and adjacent normal lung tissues were obtained from 93 patients with previously untreated NSCLC, and 43 patients whose tumor and paired normal lung tissues reached 200 mg or more were selected for measurement of the elements' concentrations using an inductively coupled plasma-atomic emission spectrometer.

RESULTS

We found that the concentrations of the 52 elements varied from 0.4 ng/g tissue (Lu, Pd, and Tm) to 1 658 000 ng/g (Na), 1 951 000 ng/g (P), and 2 495 000 ng/g (K). Thirty eight of the 52 (73.1%) elements showed approximately equal concentrations in tumor and adjacent normal lung tissues of the patients. The concentrations of nine elements (K, P, Mg, Zn, Rb, Cu, Se, Cs, and Tl) in tumor samples were significantly higher than their paired normal lung tissues, and five elements (Na, Fe, Cr, Cd, and Ge) exhibited decreased concentrations in cancer samples compared to counterpart normal lung tissues. Low Fe in tumor samples was associated with smoking history, whereas low Cr was associated with histology (squamous cell carcinoma) of the patients.

CONCLUSIONS

Our results demonstrate that measurement of elements' concentrations in both cancer and paired normal tissues is important to get insights into the roles of these elements in carcinogenesis, and therapeutic approaches to normalize the elements are warranted to treat NSCLCs.