Perturbation of Iron Metabolism by Cisplatin through Inhibition of Iron Regulatory Protein 2

Iron promotes ovarian cancer malignancy and advances platinum resistance by enhancing DNA repair via FTH1/FTL/POLQ/RAD51 axis

Iron is crucial for cell DNA synthesis and repair, but an excess of free iron can lead to oxidative stress and subsequent cell death. Although several studies suggest that cancer cells display characteristics of 'Iron addiction', an ongoing debate surrounds the question of whether iron can influence the malignant properties of ovarian cancer. In the current study, we initially found iron levels increase during spheroid formation. Furthermore, iron supplementation can promote cancer cell survival, cancer spheroid growth, and migration; vice versa, iron chelators inhibit this process. Notably, iron reduces the sensitivity of ovarian cancer cells to platinum as well. Mechanistically, iron downregulates DNA homologous recombination (HR) inhibitor polymerase theta (POLQ) and relieves its antagonism against the HR repair enzyme RAD51, thereby promoting DNA damage repair to resist chemotherapy-induced damage. Additionally, iron tightly regulated by ferritin (FTH1/FTL) which is indispensable for iron-triggered DNA repair. Finally, we discovered that iron chelators combined with platinum exhibit a synergistic inhibitory effect on ovarian cancer in vitro and in vivo. Our findings affirm the pro-cancer role of iron in ovarian cancer and reveal that iron advances platinum resistance by promoting DNA damage repair through FTH1/FTL/POLQ/RAD51 pathway. Our findings highlight the significance of iron depletion therapy, revealing a promising avenue for advancing ovarian cancer treatment.

Quantum chemistry calculation-aided discovery of potent small-molecule mimics of glutathione peroxidases for the treatment of cisplatin-induced hearing loss

Hearing loss (HL) is a health burden that seriously affects the quality of life of cancer patients receiving platinum-based chemotherapy, and few FDA-approved treatment specifically targets this condition. The main mechanisms that contribute to cisplatin-induced hearing loss are oxidative stress and subsequent cell death, including ferroptosis revealed by us as a new mechanism recently. In this study, we employed the frontier molecular orbital (FMO) theory approach as a convenient prediction method for the glutathione peroxidase (GPx)-like activity of isoselenazolones and discovered new isoselenazolones with great GPx-like activity. Notably, compound 19 exhibited significant protective effects against cisplatin-induced hair cell (HC) damage in vitro and in vivo and effectively reverses cisplatin-induced hearing loss through oral administration. Further investigations revealed that this compound effectively alleviated hair cell oxidative stress, apoptosis and ferroptosis. This research highlights the potential of GPx mimics as a therapeutic strategy against cisplatin-induced hearing loss. The application of quantum chemistry (QC) calculations in the study of GPx mimics sheds light on the development of new, innovative treatments for hearing loss.

Molecular targets of cisplatin in HeLa cells explored through competitive activity-based protein profiling strategy

Cisplatin is widely used as anticancer drugs, and DNA is considered as the main target. Considering its high affinity towards cysteines and the important role of cystine containing proteins, we applied a competitive activity-based protein profiling strategy to identify protein cysteines that bind with cisplatin in HeLa cells. Living cells were treated with cisplatin at cytotoxic concentrations, then the protein was extracted. After labeling with desthiobiotin iodoacetamide (DBIA) probe, protein was precipitated, digested and isotopically labeled, subsequently the peptides were combined, and the biotinylated cysteine-containing peptides were enriched and quantified by LC-MS/MS. A total of 3571 peptides which originated from 1871 proteins were identified using the DBIA probe. Among them, 46 proteins were screened as targets, including proteins that have been identified as binding proteins by previous study. A novel cisplatin target, calpain-1 (CAPN1), was identified and validated as binding with cisplatin in vitro.

Anti-aging Factor GRSF1 Attenuates Cerebral Ischemia-Reperfusion Injury in Mice by Inhibiting GPX4-Mediated Ferroptosis

Abnormal accumulation of senescent cells in tissues has been shown to facilitate the onset and progression of various diseases. As an important protein involving in the regulation of cellular senescence process, researches suggested GRSF1 as a potential senolytic target to improve multiple physiological and pathological processes. However, the underlying mechanism of cellular senescence on cerebral ischemia-reperfusion injury (CIRI) has not been revealed. Here, we investigated the effect of GRSF1 on CIRI and delved into its specific mechanisms. In the present study, we established a mouse model of cerebral ischemia-reperfusion (CIR) and observed low expression of anti-aging factor GRSF1, along with greatly increased levels of senescence-related markers p16 and p21 and senescence-associated secretory phenotype TNF-α. Furthermore, we found that the expression of GPX4 was elevated parallel to GRSF1 in CIR mice with overexpression of GRSF1, oxidative stress, and iron metabolism-related proteins were inhibited. Functionally, overexpressing GRSF1 significantly ameliorated infarct volume and neurological function scores and suppressed apoptosis in CIR mice, while administration of GPX4 inhibitors reversed these beneficial phenotypes. Taken together, our results indicate cellular senescence as an important pathological mechanism to exacerbate cerebral injury during CIRI, while GRSF1 could inhibit oxidative stress-mediated ferroptosis through upregulating GPX4 to attenuate reperfusion injury, which makes senolytic treatment, especially GRSF1, a promising therapeutic target for CIRI.

Divergent iron-regulatory states contribute to heterogeneity in breast cancer aggressiveness

Primary tumors with similar mutational profiles can progress to vastly different outcomes where transcriptional state, rather than mutational profile, predicts prognosis. A key challenge is to understand how distinct tumor cell states are induced and maintained. In triple negative breast cancer cells, invasive behaviors and aggressive transcriptional signatures linked to poor patient prognosis can emerge in response to contact with collagen type I. Herein, collagen-induced migration heterogeneity within a TNBC cell line was leveraged to identify transcriptional programs associated with invasive versus non-invasive phenotypes and implicate molecular switches. Phenotype-guided sequencing revealed that invasive cells upregulate iron uptake and utilization machinery, anapleurotic TCA cycle genes, actin polymerization promoters, and a distinct signature of Rho GTPase activity and contractility regulating genes. The non-invasive cell state is characterized by actin and iron sequestration modules along with glycolysis gene expression. These unique tumor cell states are evident in patient tumors and predict divergent outcomes for TNBC patients. Glucose tracing confirmed that non-invasive cells are more glycolytic than invasive cells, and functional studies in cell lines and PDO models demonstrated a causal relationship between phenotype and metabolic state. Mechanistically, the OXPHOS dependent invasive state resulted from transient HO-1 upregulation triggered by contact with dense collagen that reduced heme levels and mitochondrial chelatable iron levels. This induced expression of low cytoplasmic iron response genes regulated by ACO1/IRP1. Knockdown or inhibition of HO-1, ACO1/IRP1, MRCK, or OXPHOS abrogated invasion. These findings support an emerging theory that heme and iron flux serve as important regulators of TNBC aggressiveness.

Transferrin receptor in primary and metastatic breast cancer: Evaluation of expression and experimental modulation to improve molecular targeting

BACKGROUND

Conjugation of transferrin (Tf) to imaging or nanotherapeutic agents is a promising strategy to target breast cancer. Since the efficacy of these biomaterials often depends on the overexpression of the targeted receptor, we set out to survey expression of transferrin receptor (TfR) in primary and metastatic breast cancer samples, including metastases and relapse, and investigate its modulation in experimental models.

METHODS

Gene expression was investigated by datamining in twelve publicly-available datasets. Dedicated Tissue microarrays (TMAs) were generated to evaluate matched primary and bone metastases as well as and pre and post chemotherapy tumors from the same patient. TMA were stained with the FDA-approved MRQ-48 antibody against TfR and graded by staining intensity (H-score). Patient-derived xenografts (PDX) and isogenic metastatic mouse models were used to study in vivo TfR expression and uptake of transferrin.

RESULTS

TFRC gene and protein expression were high in breast cancer of all subtypes and stages, and in 60-85% of bone metastases. TfR was detectable after neoadjuvant chemotherapy, albeit with some variability. Fluorophore-conjugated transferrin iron chelator deferoxamine (DFO) enhanced TfR uptake in human breast cancer cells in vitro and proved transferrin localization at metastatic sites and correlation of tumor burden relative to untreated tumor mice.

CONCLUSIONS

TfR is expressed in breast cancer, primary, metastatic, and after neoadjuvant chemotherapy. Variability in expression of TfR suggests that evaluation of the expression of TfR in individual patients could identify the best candidates for targeting. Further, systemic iron chelation with DFO may upregulate receptor expression and improve uptake of therapeutics or tracers that use transferrin as a homing ligand.

Radiometal-Labeled Photoactivatable Pt(IV) Anticancer Complex for Theranostic Phototherapy

A novel photoactivatable Pt(IV) diazido anticancer agent, Pt-succ-DFO, bearing a pendant deferoxamine (DFO) siderophore for radiometal chelation, has been synthesized for the study of its in vivo behavior with radionuclide imaging. Pt-succ-DFO complexation of Fe(III) and Ga(III) ions yielded new heterobimetallic complexes that maintain the photoactivation properties and photocytotoxicity of the parent Pt complex in human cancer cell lines. Radiolabeled Pt-succ-DFO-68Ga (t1/2 = 68 min, positron emitter) was readily prepared under mild conditions and was stable in the dark upon incubation with human serum. PET imaging of Pt-succ-DFO-68Ga in healthy mice revealed a promising biodistribution profile with rapid renal excretion and limited organ accumulation, implying that little off-target uptake is expected for this class of agents. Overall, this research provides the first in vivo imaging study of the whole-body distribution of a photoactivatable Pt(IV) azido anticancer complex and illustrates the potential of radionuclide imaging as a tool for the preclinical development of novel light-activated agents.

Evaluation of the therapeutic efficacy of Vitex agnus-castus extract on cisplatin-induced hematotoxicity in female Wistar rats

Background and Aim

Cisplatin (CP) is a preferred drug for cancer treatment but it has dose-dependent side effects. Vitex agnus-castus (VAC) berry extract has antioxidant, free-radical scavenging, and anti-inflammatory activities. This study explored the mitigating effects of VAC extract (VACE) on acute hematotoxicity induced by CP in female Wistar rats.

Materials and Methods

Female Wistar rats (n = 30) were randomly divided into five groups (n = 6/group). The normal control (NC) group received no treatment. The CP control group received CP (7 mg/kg.b.w. ip, single dose) and the drug control group (VACE-650) received VACE (650 mg/kg b.w. oral, daily) for 7 days. Both groups received a single dose of CP (7 mg/kg b.w. ip), followed by 350 and 650 mg/kg.b.w. of VACE daily orally (CPVACE-350 and CPVACE-650 groups, respectively) for 7 days.

Results

After a single dose of CP (7 mg/kg b.w.), the red blood cells (RBC), hematocrit (HCT), white blood cells (WBC), and platelets significantly decreased. In the VAC-350 group, the reduction in total WBC count was less than that in the VAC-650 group on the 3rd day. The RBC and HCT values of the VACE groups were better than that of the CP control, but the VACE-350 treatment group showed significant improvement only on the 3rd day.

Conclusion

Our findings showed that VACE can mitigate CP-induced damage to peripheral blood cells at lower doses.

Role of Mouse Organic Cation Transporter 2 for Nephro- and Peripheral Neurotoxicity Induced by Chemotherapeutic Treatment with Cisplatin

Cisplatin (CDDP) is an efficient chemotherapeutic agent broadly used to treat solid cancers. Chemotherapy with CDDP can cause significant unwanted side effects such as renal toxicity and peripheral neurotoxicity. CDDP is a substrate of organic cation transporters (OCT), transporters that are highly expressed in renal tissue. Therefore, CDDP uptake by OCT may play a role in causing unwanted toxicities of CDDP anticancer treatment. In this study, the contribution of the mouse OCT2 (mOCT2) to CDDP nephro- and peripheral neurotoxicity was investigated by comparing the effects of cyclic treatment with low doses of CDDP on renal and neurological functions in wild-type (WT) mice and mice with genetic deletion of OCT2 (OCT2-/- mice). This CDDP treatment protocol caused significant impairment of kidneys and peripherical neurological functions in WT mice. These effects were significantly reduced in OCT2-/- mice, however, less profoundly than what was previously measured in mice with genetic deletion of both OCT1 and 2 (OCT1-2-/- mice). Comparing the apparent affinities (IC50) of mOCT1 and mOCT2 for CDDP, the mOCT1 displayed a higher affinity for CDDP than the mOCT2 (IC50: 9 and 558 µM, respectively). Also, cellular toxicity induced by incubation with 100 µM CDDP was more pronounced in cells stably expressing mOCT1 than in cells expressing mOCT2. Therefore, in mice, CDDP uptake by both OCT1 and 2 contributes to the development of CDDP undesired side effects. OCT seem to be suitable targets for establishing treatment protocols aimed at decreasing unwanted CDDP toxicity and improving anticancer treatment with CDDP.

KLF14 regulates the growth of hepatocellular carcinoma cells via its modulation of iron homeostasis through the repression of iron-responsive element-binding protein 2

BACKGROUND

Hepatocellular carcinoma (HCC) is a multifactor-driven malignant tumor with rapid progression, which causes the difficulty to substantially improve the prognosis of HCC. Limited understanding of the mechanisms in HCC impedes the development of efficacious therapies. Despite Krüpple-Like factors (KLFs) were reported to be participated in HCC pathogenesis, the function of KLF14 in HCC remains largely unexplored.

METHODS

We generated KLF14 overexpressed and silenced liver cancer cells, and nude mouse xenograft models for the in vitro and in vivo study. Luciferase reporter assay, ChIP-qPCR, Co-IP, immunofluorescence were performed for mechanism research. The expression of KLF14 in HCC samples was analyzed by quantitative RT-PCR, Western blotting, and immunohistochemistry (IHC) analysis.

RESULTS

KLF14 was significantly downregulated in human HCC tissues, which was highly correlated with poor prognosis. Inhibition of KLF14 promoted liver cancer cells proliferation and overexpression of KLF14 suppressed cells growth. KLF14 exerts its anti-tumor function by inhibiting Iron-responsive element-binding protein 2 (IRP2), which then causes transferrin receptor-1(TfR1) downregulation and ferritin upregulation on the basis of IRP-IREs system. This then leading to cellular iron deficiency and HCC cells growth suppression in vitro and in vivo. Interestingly, KLF14 suppressed the transcription of IRP2 via recruiting SIRT1 to reduce the histone acetylation of the IRP2 promoter, resulting in iron depletion and cell growth suppression. More important, we found fluphenazine is an activator of KLF14, inhibiting HCC cells growth through inducing iron deficiency.

CONCLUSION

KLF14 acts as a tumor suppressor which inhibits the proliferation of HCC cells by modulating cellular iron metabolism via the repression of IRP2. We identified Fluphenazine, as an activator of KLF14, could be a potential compound for HCC therapy. Our findings therefore provide an innovative insight into the pathogenesis of HCC and a promising therapeutic target.

Targeting critical pathways in ferroptosis and enhancing antitumor therapy of Platinum drugs for colorectal cancer

Colorectal cancer (CRC) can be resistant to platinum drugs, possibly through ferroptosis suppression, albeit the need for further work to completely understand this mechanism. This work aimed to sum up current findings pertaining to oxaliplatin resistance (OR) or resistance to ascertain the potential of ferroptosis to regulate oxaliplatin effects. In this review, tumor development relating to iron homeostasis, which includes levels of iron that ascertain cells' sensitivity to ferroptosis, oxidative stress, or lipid peroxidation in colorectal tumor cells that are connected with ferroptosis initiation, especially the role of c-Myc/NRF2 signaling in regulating iron homeostasis, coupled with NRF2/GPX4-mediated ferroptosis are discussed. Importantly, ferroptosis plays a key role in OR and ferroptotic induction may substantially reverse OR in CRC cells, which in turn could inhibit the imbalance of intracellular redox induced by oxaliplatin and ferroptosis, as well as cause chemotherapeutic resistance in CRC. Furthermore, fundamental research of small molecules, ferroptosis inducers, GPX4 inhibitors, or natural products for OR coupled with their clinical applications in CRC have also been summarized. Also, potential molecular targets and mechanisms of small molecules or drugs are discussed as well. Suggestively, OR of CRC cells could significantly be reversed by ferroptosis induction, wherein this result is discussed in the current review. Prospectively, the existing literature discussed in this review will provide a solid foundation for scientists to research the potential use of combined anticancer drugs which can overcome OR via targeting various mechanisms of ferroptosis. Especially, promising therapeutic strategies, challenges ,and opportunities for CRC therapy will be discussed.

Single-cell and bulk ICP-MS investigation of accumulation patterns of Pt-based metallodrugs in cisplatin-sensitive and -resistant cell models

In research enabling preclinical development and attaining a deeper understanding of the behavior of metallodrugs in cancer cells with acquired resistance, intracellular Pt accumulation could be considered an important biomarker and analytical focus. In this work, Pt accumulation patterns in terms of the number of cells and Pt mass in single cells were precisely defined by using inductively coupled plasma-mass spectrometry (ICP-MS) operating in a fast time-resolved analysis mode. This technique is otherwise known as single-cell (SC)-ICP-MS. By applying the nascent and validated SC-ICP-MS technique, comparisons across three Pt drugs (cisplatin, carboplatin, and oxaliplatin) in the A2780 and A2780cis ovarian cancer cell models could be made. Additional roles of transporters on top of passive diffusion and the drugs' bioactivity could be postulated. The SC-ICP-MS-based observations also served as a cross-validation point to augment preexisting research findings on Pt-resistance mechanisms. Conjectures regarding S and Fe metabolism were also derived based on an additional and direct ICP-MS analysis of endogenous elements. Overall, our work not only confirms the utility of SC-ICP-MS in chemotherapeutic research, but also provided insights into further ICP-MS-based analytical capacities to be developed.

Iron metabolism: pathways and proteins in homeostasis

Iron is essential to human survival. The biological role and trafficking of this trace essential inorganic element which is also a potential toxin is constantly being researched and unfolded. Vital for oxygen transport, DNA synthesis, electron transport, neurotransmitter biosynthesis and present in numerous other heme and non-heme enzymes the physiological roles are immense. Understanding the molecules and pathways that regulate this essential element at systemic and cellular levels are of importance in improving therapeutic strategies for iron related disorders. This review highlights the progress in understanding the metabolism and trafficking of iron along with the pathophysiology of iron related disorders.

A genome-wide CRISPR-Cas9 screen identifies CENPJ as a host regulator of altered microtubule organization during Plasmodium liver infection

Prior to initiating symptomatic malaria, a single Plasmodium sporozoite infects a hepatocyte and develops into thousands of merozoites, in part by scavenging host resources, likely delivered by vesicles. Here, we demonstrate that host microtubules (MTs) dynamically reorganize around the developing liver stage (LS) parasite to facilitate vesicular transport to the parasite. Using a genome-wide CRISPR-Cas9 screen, we identified host regulators of cytoskeleton organization, vesicle trafficking, and ER/Golgi stress that regulate LS development. Foci of γ-tubulin localized to the parasite periphery; depletion of centromere protein J (CENPJ), a novel regulator identified in the screen, exacerbated this re-localization and increased infection. We demonstrate that the Golgi acts as a non-centrosomal MT organizing center (ncMTOC) by positioning γ-tubulin and stimulating MT nucleation at parasite periphery. Together, these data support a model where the Plasmodium LS recruits host Golgi to form MT-mediated conduits along which host organelles are recruited to PVM and support parasite development.

Effect of Cisplatin on Renal Iron Homeostasis Components: Implication in Nephropathy

Cisplatin is an important chemotherapeutic drug for the treatment of solid tumors but often causes nephropathy as part of the off-target toxicity. Iron accumulation and related damage were implicated in cisplatin-induced kidney injury. However, the role of cisplatin in the renal iron sensing mechanism and its target genes responsible for iron uptake, storage, and release have not been investigated. Cellular iron homeostasis is controlled by the interaction of iron regulatory proteins (IRP1 and IRP2) and iron-responsive elements (IREs) present in the untranslated regions of iron transport and storage components. Here, we report that cisplatin does not influence the expressions of IRP targets such as transferrin receptor-1 (TfR1), divalent metal transporter-1 (DMT1), and ferroportin in renal cells despite the increased heme oxygenase-1 (HO-1) level. Ferritin subunits (Ft-H and Ft-L) are elevated in different magnitudes due to the increased mRNA expression. Intriguingly, a higher expression of Ft-L mRNA is detected than that of Ft-H mRNA. The inability of cisplatin in altering the IRE-IRP interaction is confirmed by examining IRE-containing luciferase activity, RNA electrophoretic mobility shift assay, and activation of IRPs. The labile iron pool is depleted but reversed by silencing of either Ft-H or Ft-L, suggesting increased iron storage by ferritin. Silencing of Ft-H or Ft-L promotes cell death, suggesting that ferritin acts to protect the renal cells from cisplatin-mediated toxicity. A differential increase of transcripts and equivalent increase of proteins of Ft-H and Ft-L and unaltered TfR1 and DMT1 transcripts are found in the kidneys of cisplatin-treated rats along with iron accumulation. Our results reveal that cisplatin does not influence the IRE-IRP interaction despite alteration of the cellular iron pool in renal cells. This insensitivity of the IRE-IRP system may be implicated in the accumulation of iron to contribute to cisplatin-induced nephropathy.

Cisplatin causes covalent inhibition of protein-tyrosine phosphatase 1B (PTP1B) through reaction with its active site cysteine: Molecular, cellular and in vivo mice studies

Protein tyrosine phosphatase 1B (PTP1B) is a critical regulator of different signalling cascades such as the EGFR pathway. The biological importance of PTP1B is further evidenced by knockout mice studies and the identification of recurrent mutations/deletions in PTP1B linked to metabolic and oncogenic alterations. Cisplatin is among the most widely used anticancer drug. The biological effects of cisplatin are thought to arise primarily from DNA damaging events involving cisplatin-DNA adducts. However, increasing evidence indicate that the biological properties of cisplatin could also rely on the perturbation of other processes such as cell signalling through direct interaction with certain cysteine residues in proteins. Here, we provide molecular, cellular and in vivo evidence suggesting that PTP1B is a target of cisplatin. Mechanistic studies indicate that cisplatin inhibited PTP1B in an irreversible manner and binds covalently to the catalytic cysteine residue of the enzyme. Accordingly, experiments conducted in cells and mice exposed to cisplatin showed inhibition of endogenous PTP1B and concomitant increase in tyrosine phosphorylation of EGFR. These findings are consistent with previous studies showing tyrosine phosphorylation-dependent activation of the EGFR pathway by cisplatin and with recent studies suggesting PTP1B inhibition by cisplatin and other platinum complexes. Importantly, our work provides novel mechanistic evidence that PTP1B is a protein target of cisplatin and is inhibited by this drug at molecular, cellular and in vivo levels. In addition, our work may contribute to the understanding of the pathways undergoing modulation upon cisplatin administration beyond of the established genotoxic effect of cisplatin.

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.

A Ferroptosis-Related Gene Signature for Predicting the Prognosis and Drug Sensitivity of Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers worldwide and has a high mortality. Ferroptosis, an iron-dependent form of programmed cell death, plays a crucial role in tumor suppression and chemotherapy resistance in cancer. However, the prognostic and clinical values of ferroptosis-related genes (FRGs) in HNSCC remain to be further explored. In the current study, we constructed a ferroptosis-related prognostic model based on the Cancer Genome Atlas database and then explored its prognostic and clinical values in HNSCC via a series of bioinformatics analyses. As a result, we built a four-gene prognostic signature, including FTH1, BNIP3, TRIB3, and SLC2A3. Survival analysis showed that the high-risk group presented significantly poorer overall survival than the low-risk group. Moreover, the ferroptosis-related signature was found to be an independent prognostic predictor with high accuracy in survival prediction for HNSCC. According to immunity analyses, we found that the low-risk group had higher anti-tumor immune infiltration cells and higher expression of immune checkpoint molecules and meanwhile corelated more closely with some anti-tumor immune functions. Meanwhile, all the above results were validated in the independent HSNCC cohort GSE65858. Besides, the signature was found to be remarkably correlated with sensitivity of common chemotherapy drugs for HNSCC patients and the expression levels of signature genes were also significantly associated with drug sensitivity to cancer cells. Overall, we built an effective ferroptosis-related prognostic signature, which could predict the prognosis and help clinicians to perform individualized treatment strategy for HNSCC patients.

Integrated analysis identifies TfR1 as a prognostic biomarker which correlates with immune infiltration in breast cancer

Breast cancer (BC) is the most common malignancy with high morbidity and mortality in females worldwide. Emerging evidence indicates that transferrin receptor 1 (TfR1) plays vital roles in regulating cellular iron import. However, the distinct role of TfR1 in BC remains elusive. TfR1 expression was investigated using the TCGA, GEO, TIMER, UALCAN and Oncomine databases. The prognostic potential of TfR1 was evaluated by Kaplan-Meier (KM) plotter and univariate and multivariate Cox regression analyses. Moreover, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene set enrichment analysis (GSEA) were used to explore the molecular mechanism of TfR1. The potential link between TfR1 expression and infiltrating abundances of immune cells was examined through the TIMER and CIBERSORT algorithm. The expression of TfR1 was dramatically upregulated in BC tissues. Increased TfR1 expression and decreased methylation levels of TfR1 were strongly correlated with multiple clinicopathological parameters. Elevated TfR1 expression was associated with a poor survival rate in BC patients. The nomogram model further confirmed that TfR1 could act as an independent prognostic biomarker in BC. The results of GO, KEGG and GSEA revealed that TfR1 was closely correlated with multiple signaling pathways and immune responses. Additionally, TfR1 was positively associated with the infiltration abundances of six major immune cells, including CD4+ T cells, CD8+ T cells, B cells, neutrophils, macrophages, and dendritic cells in BC. Interestingly, TfR1 influenced prognosis partially through immune infiltration. These comprehensive bioinformatics analyses suggest that TfR1 is a new independent prognostic biomarker and a potential target for immunotherapy in BC.

Iron regulatory protein 1 promotes ferroptosis by sustaining cellular iron homeostasis in melanoma

Melanoma, the most aggressive skin cancer, is mainly treated with BRAF inhibitors or immunotheareapy. However, most patients who initially responded to BRAF inhibitors or immunotheareapy become resistant following relapse. Ferroptosis is a form of regulated cell death characterized by its dependence on iron ions and the accumulation of lipid reactive oxygen species (ROS). Recent studies have demonstrated that ferroptosis is a good method for tumor treatment, and iron homeostasis is closely associated with ferroptosis. Iron regulatory protein (IRP)1 and 2 play important roles in maintaining iron homeostasis, but their functions in ferroptosis have not been investigated. The present study reported that the expression of IRP1 and IRP2 was increased by the ferroptosis inducers erastin and RSL3 in melanoma cells. Depletion of IRP1 significantly suppressed erastin- and RSL3-induced ferroptosis. IRP2 had a weak effect but could enhance the promoting function of IRP1 on ferroptosis. Further, erastin and RSL3 promoted the transition of aconitase 1 to IRP1, which regulated downstream iron metabolism proteins, including transferrin receptor (TFRC), ferroportin (FPN) and ferritin heavy chain 1 (FTH1). Moreover, overexpression of TFRC and knockdown of FPN and FTH1 significantly promoted erastin- and RSL3-induced ferroptosis in IRP1 knockdown melanoma cells. Collectively, the present findings indicate that IRP1 plays an essential role in erastin- and RSL3-induced ferroptosis by regulating iron homeostasis.

Iron metabolism: an emerging therapeutic target underlying the anti-cancer effect of quercetin

Iron, an essential micronutrient for all kinds of cells, is essential for the balance of body internal environment. Notably, cancer cells exhibit a strong dependence on iron and require a large amount of iron for proliferation. A growing number of studies suggested that iron metabolism imbalance and subsequent excess iron accumulation are closely related to the occurrence and progression of cancer. Precisely, excess iron promotes the development of cancer due to the pro-oxidative nature of iron and its damaging effects on DNA. Simultaneously, tumor cells acquire large amounts of iron to maintain rapid growth and proliferation. Therefore, targeting iron metabolism may provide a new way for the treatment of cancer. Quercetin, a natural flavonoid, has long been regarded as potential drug for cancer treatments owing to its anti-inflammatory, antioxidant and anti-tumor effects. It is proven that quercetin possesses a high iron-chelating capacity, depriving cancer cells of iron or altering iron metabolism. Herein, we conduct a review on the mechanisms of iron imbalance in tumors and the role of quercetin in iron chelation, which will provide insight into the potential for quercetin as an anti-cancer drug.

Iron Metabolism in the Tumor Microenvironment: Contributions of Innate Immune Cells

Cells of the innate immune system are a major component of the tumor microenvironment. They play complex and multifaceted roles in the regulation of cancer initiation, growth, metastasis and responses to therapeutics. Innate immune cells like neutrophils and macrophages are recruited to cancerous tissues by chemotactic molecules released by cancer cells and cancer-associated stromal cells. Once they reach the tumor, they can be instructed by a network of proteins, nucleic acids and metabolites to exert protumoral or antitumoral functions. Altered iron metabolism is a feature of cancer. Epidemiological studies suggest that increased presence of iron and/or iron binding proteins is associated with increased risks of cancer development. It has been shown that iron metabolism is involved in shaping the immune landscapes in inflammatory/infectious diseases and cancer-associated inflammation. In this article, we will dissect the contribution of macrophages and neutrophils to dysregulated iron metabolism in malignant cells and its impact on cancer growth and metastasis. The mechanisms involved in regulating the actions of macrophages and neutrophils will also be discussed. Moreover, we will examine the effects of iron metabolism on the phenotypes of innate immune cells. Both iron chelating and overloading agents are being explored in cancer treatment. This review highlights alternative strategies for management of iron content in cancer cells by targeting the iron donation and modulation properties of macrophages and neutrophils in the tumor microenvironment.

Protein regulation strategies of the mouse spleen in response to Babesia microti infection

BACKGROUND

Babesia is a protozoan parasite that infects red blood cells in some vertebrates. Some species of Babesia can induce zoonoses and cause considerable harm. As the largest immune organ in mammals, the spleen plays an important role in defending against Babesia infection. When infected with Babesia, the spleen is seriously injured but still actively initiates immunomodulatory responses.

METHODS

To explore the molecular mechanisms underlying the immune regulation and self-repair of the spleen in response to infection, this study used data-independent acquisition (DIA) quantitative proteomics to analyse changes in expression levels of global proteins and in phosphorylation modification in spleen tissue after Babesia microti infection in mice.

RESULTS

After mice were infected with B. microti, their spleens were seriously damaged. Using bioinformatics methods to analyse dynamic changes in a large number of proteins, we found that the spleen still initiated immune responses to combat the infection, with immune-related proteins playing an important role, including cathepsin D (CTSD), interferon-induced protein 44 (IFI44), interleukin-2 enhancer-binding factor 2 (ILF2), interleukin enhancer-binding factor 3 (ILF3) and signal transducer and activator of transcription 5A (STAT5A). In addition, some proteins related to iron metabolism were also involved in the repair of the spleen after B. microti infection, including serotransferrin, lactoferrin, transferrin receptor protein 1 (TfR1) and glutamate-cysteine ligase (GCL). At the same time, the expression and phosphorylation of proteins related to the growth and development of the spleen also changed, including protein kinase C-δ (PKC-δ), mitogen-activated protein kinase (MAPK) 3/1, growth factor receptor-bound protein 2 (Grb2) and P21-activated kinase 2 (PAK2).

CONCLUSIONS

Immune-related proteins, iron metabolism-related proteins and growth and development-related proteins play an important role in the regulation of spleen injury and maintenance of homeostasis. This study provides an important basis for the diagnosis and treatment of babesiosis.

Iron regulatory protein 2 is required for artemether -mediated anti-hepatic fibrosis through ferroptosis pathway

BACKGROUND

Currently, the existing treatments have not cured the liver fibrosis thoroughly. Ferroptosis is a newly discovered way of cell death, which is closely related to many diseases. Previous studies have shown that ferroptosis plays an important role in the occurrence and development of liver fibrosis, but the further mechanism remains to be discovered.

METHODS

LX-2 cells were used as the research object, fibrosis activation index was detected by Western blot, PCR and Immunofluorescence, ferroptosis was detected by kits, the binding and interaction between IRP2 (iron regulatory protein 2) and STUB1 (STIP1 homology and U-box containing protein 1) were detected by Immunoprecipitation and ubiquitin test, and IRP2 knockdown mice were constructed by interfering plasmid to verify the results of in vitro experiment.

RESULT

Our research showed that ART (artemether) had a good anti-fibrosis effect in vivo and in vitro, and ferroptosis played an important role in this process. Further studies have found that ART could lead to the accumulation of IRP 2 a in hepatic stellate cell by inhibiting the ubiquitination of it, thus inducing the increase of iron in HSC (hepatic stellate cell), which could product a large number of ROS (reactive oxide species), resulting the occurrence of ferroptosis in cells. Our findings provided an experimental basis for ART to become a drug for the treatment of liver fibrosis.

CONCLUSION

Our results show that IRP2-Iron-ROS axis is necessary for ART to induce ferroptosis in HSC and play an anti-fibrotic effect.

Nano liposomal and cubosomal formulations with platinum-based anticancer agents: therapeutic advances and challenges

Nephrotoxicity, neurotoxicity and multidrug resistance in tumor cells can result from platinum-based anticancer (PBA) agents which can be reduced by nano formulations. Recently, novel formulations based on liposomes and cubosomes have been described as efficient strategies to overcome nephrotoxicity, ototoxicity, neurotoxicity, cardiotoxicity, hematological toxicities, hepatotoxicity and gastrointestinal toxicity as well as multidrug resistance. The co-delivery of anticancer agents concomitant with PBAs via biocompatible and biodegradable smart liposomes and cubosomes can augment therapeutic results of chemotherapy as well as radiotherapy owing to their high accessibility of surface and internal modification. For this purpose, surface, bilayer or core sections of these formulations can be functionalized by pure PBAs or modified PBAs. In this review, recent significant advances and challenges related to various liposomal and cubosomal formulations of PBA are presented in order to emphasize suitable formulations for anticancer applications with critical thoughts provided on how the field can progress.

Iron and Cancer: 2020 Vision

New and provocative insights into the relationships between iron and cancer have been uncovered in recent years. These include delineation of connections that link cellular iron to DNA repair, genomic integrity, and oncogenic signaling as well as the discovery of ferroptosis, a novel iron-dependent form of cell death. In parallel, new molecules and pathways that regulate iron influx, intracellular iron trafficking, and egress in normal cells, and their perturbations in cancer have been discovered. In addition, insights into the unique properties of iron handling in tumor-initiating cells (cancer stem cells), novel contributions of the tumor microenvironment to the uptake and regulation of iron in cancer cells, and new therapeutic modalities that leverage the iron dependence of cancer have emerged.

Polyphosphate Functions In Vivo as an Iron Chelator and Fenton Reaction Inhibitor

How do organisms deal with free iron? On the one hand, iron is an essential metal that plays crucial structural and functional roles in many organisms. On the other hand, free iron is extremely toxic, particularly under aerobic conditions, where iron rapidly undergoes the Fenton reaction and produces highly reactive hydroxyl radicals. Our study now demonstrates that we have discovered one of the first physiologically relevant nonproteinaceous iron chelators and Fenton inhibitors. We found that polyphosphate, a highly conserved and ubiquitous inorganic polyanion, chelates iron and, through its multivalency, prevents the interaction of iron with peroxide and therefore the formation of hydroxyl radicals. We show that polyP provides a crucial iron reservoir for metalloproteins under nonstress conditions and effectively chelates free iron during iron stress. Importantly, polyP is present in all cells and organisms and hence is likely to take on this crucial function in both prokaryotic and eukaryotic cells.

Maintaining cellular iron homeostasis is critical for organismal survival. Whereas iron depletion negatively affects the many metabolic pathways that depend on the activity of iron-containing enzymes, any excess of iron can cause the rapid formation of highly toxic reactive oxygen species (ROS) through Fenton chemistry. Although several cellular iron chelators have been identified, little is known about if and how organisms can prevent the Fenton reaction. By studying the effects of cisplatin, a commonly used anticancer drug and effective antimicrobial, we discovered that cisplatin elicits severe iron stress and oxidative DNA damage in bacteria. We found that both of these effects are successfully prevented by polyphosphate (polyP), an abundant polymer consisting solely of covalently linked inorganic phosphates. Subsequent in vitro and in vivo studies revealed that polyP provides a crucial iron reservoir under nonstress conditions and effectively complexes free iron and blocks ROS formation during iron stress. These results demonstrate that polyP, a universally conserved biomolecule, plays a hitherto unrecognized role as an iron chelator and an inhibitor of the Fenton reaction.

Transmembrane protein western blotting: Impact of sample preparation on detection of SLC11A2 (DMT1) and SLC40A1 (ferroportin)

Western blotting has been widely used for investigation of protein expression, posttranslational modifications, and interactions. Because western blotting usually involves heat-denaturation of samples prior to gel loading, clarification of detailed procedures for sample preparation have been omitted or neglected in many publications. We show here the case that even excellent primary antibodies failed to detect a specific protein of interest due to a routine heating practice of protein samples. We performed western blotting for transmembrane iron transporter proteins; SLC11A2 (divalent metal transporter 1, DMT1), SLC40A1 (ferroportin 1, Fpn1), and transferrin receptor-1 (TfR1), along with cytoplasmic iron storage protein ferritin H. Our results in 12 human culture cell lysates indicated that only unheated samples prior to gel loading gave rise to clear resolution of DMT1 protein, while heated samples (95°C, 5min) caused the loss of resolution due to DMT1 protein aggregates. Unheated samples also resulted in better resolution for Fpn1 and TfR1 western blots. Conversely, only heated samples allowed to detect ferritin H, otherwise ferritin polymers failed to get into the gel. Neither different lysis/sample loading buffers nor sonication improved the resolution of DMT1 and Fpn1 western blots. Thus, heating samples most critically affected the outcome of western blotting, suggesting the similar cases for thousands of other transmembrane and heat-sensitive proteins.

Enhancing the chemotherapeutic efficacy of platinum prodrug nanoparticles and inhibiting cancer metastasis by targeting iron homeostasis

Iron plays important roles in tumor growth and metastasis, and iron depletion has become a new therapeutic strategy for iron overload cancers. Cisplatin is widely applied in the clinical therapy of various malignancies, but it has no inhibitory effect on cancer metastasis. In the present study, we found that the combination of cisplatin and iron chelator Dp44mT resulted in enhanced cell apoptosis as well as attenuated cell mobility and migration in vitro. Next, we developed a nano-carrier system to promote intracellular drug accumulation and reduce the side effects in cancer cells. Results showed that the as-synthesized nanoparticles (NPs) exhibited excellent antitumor efficiency when combined with Dp44mT. In breast tumor-bearing mice, the combination of the NPs and Dp44mT dramatically prevented orthotopic mammary tumor growth and inhibited metastasis via downregulation of VEGFα, MMP2 and Vimentin. In conclusion, as a versatile nano-platform for the combination of chemotherapy and iron chelators, the current design holds great potential for metastasis-inhibited cancer therapy.

Altered Iron Metabolism and Impact in Cancer Biology, Metastasis, and Immunology

Iron is an essential nutrient that plays a complex role in cancer biology. Iron metabolism must be tightly controlled within cells. Whilst fundamental to many cellular processes and required for cell survival, excess labile iron is toxic to cells. Increased iron metabolism is associated with malignant transformation, cancer progression, drug resistance and immune evasion. Depleting intracellular iron stores, either with the use of iron chelating agents or mimicking endogenous regulation mechanisms, such as microRNAs, present attractive therapeutic opportunities, some of which are currently under clinical investigation. Alternatively, iron overload can result in a form of regulated cell death, ferroptosis, which can be activated in cancer cells presenting an alternative anti-cancer strategy. This review focuses on alterations in iron metabolism that enable cancer cells to meet metabolic demands required during different stages of tumorigenesis in relation to metastasis and immune response. The strength of current evidence is considered, gaps in knowledge are highlighted and controversies relating to the role of iron and therapeutic targeting potential are discussed. The key question we address within this review is whether iron modulation represents a useful approach for treating metastatic disease and whether it could be employed in combination with existing targeted drugs and immune-based therapies to enhance their efficacy.

Cyclophosphamide induces a significant increase in iron content in the liver and spleen of mice

Objective:

Oxidative stress is one of the major mechanisms of cyclophosphamide (CPX)-induced toxicities. However, it is unknown how CPX induces oxidative stress. Based on the available information, we speculated that CPX could increase iron content in the tissues and then induce oxidative stress.

Method:

We tested this hypothesis by investigating the effects of CPX on iron and ferritin contents, expression of transferrin receptor 1 (TfR1), ferroportin 1 (Fpn1), iron regulatory proteins (IRPs), hepcidin, and nuclear factor erythroid 2-related factor-2 (Nrf2) in the liver and spleen, and also on reticulocyte count, immature reticulocyte fraction, and hemoglobin (Hb) in the blood in c57/B6 mouse.

Results:

We demonstrated that CPX could induce a significant increase in iron contents and ferritin expression in the liver and spleen, notably inhibit erythropoiesis and Hb synthesis and lead to a reduction in iron usage. The reduced expression in TfR1 and Fpn1 is a secondary effect of CPX-induced iron accumulation in the liver and spleen and also partly associated with the suppressed IRP/iron-responsive element system, upregulation of hepcidin, and downregulation of Nrf2.

Conclusions:

The reduced iron usage is one of the causes for iron overload in the liver and spleen and the increased tissue iron might be one of the mechanisms for CPX to induce oxidative stress and toxicities.

Ferritin Nanocages for Protein Delivery to Tumor Cells

The delivery of therapeutic proteins is one of the greatest challenges in the treatment of human diseases. In this frame, ferritins occupy a very special place. Thanks to their hollow spherical structure, they are used as modular nanocages for the delivery of anticancer drugs. More recently, the possibility of encapsulating even small proteins with enzymatic or cytotoxic activity is emerging. Among all ferritins, particular interest is paid to the Archaeoglobus fulgidus one, due to its peculiar ability to associate/dissociate in physiological conditions. This protein has also been engineered to allow recognition of human receptors and used in vitro for the delivery of cytotoxic proteins with extremely promising results.

Iron-induced transferrin receptor-1 mRNA destabilization: A response to "Neither miR-7-5p nor miR-141-3p is a major mediator of iron-responsive transferrin receptor-1 mRNA degradation"

We read with great interest the Divergent Views article by Connell and colleagues disputing our recent publication describing a role for two microRNAs in the iron-mediated regulation of transferrin receptor 1 (TfR1) mRNA stability. Our publication sought to shed light on a long-standing question in the field of cellular iron metabolism, and we welcome commentary and critique. However, there are several critical issues contained in the article by Connell and colleagues that require further consideration. We appreciate the opportunity to reply here.

DIBI, a novel 3-hydroxypyridin-4-one chelator iron-binding polymer, inhibits breast cancer cell growth and functions as a chemosensitizer by promoting S-phase DNA damage

Breast cancer is a leading cause of cancer-related death in women; however, chemotherapy of breast cancer is often hindered by dose-limiting toxicities, demonstrating the need for less toxic approaches to treatment. Since the rapid growth and metabolism of breast cancer cells results in an increased requirement for iron, withdrawal of bioavailable iron using highly selective iron chelators has been suggested to represent a new approach to breast cancer treatment. Here we show that the recently developed iron-binding polymer DIBI inhibited the growth of five different breast cancer cell lines (SK-BR3, MDA-MB-468, MDA-MB-231, MCF-7, and T47D). In cultures of MDA-MB-468 breast cancer cells, which were most sensitive to DIBI-mediated growth inhibition, iron withdrawal was associated with increased expression of transferrin receptor 1 and ferritin H mRNA but decreased expression of ferroportin mRNA. MDA-MB-468 cells that were exposed to DIBI experienced double-strand DNA breaks during the S phase of the cell cycle. DNA damage was not mediated by reactive oxygen species (ROS) since DIBI-treated MDA-MB-468 cells exhibited a reduction in intracellular ROS. DIBI-treated MDA-MB-468 cells also showed increased sensitivity to growth inhibition by the chemotherapeutic drugs cisplatin, doxorubicin, and 4-hydroperoxy cyclophosphamide (active metabolite of cyclophosphamide). Combination treatment of MDA-MB-468 cells with DIBI and cisplatin caused greater DNA damage than either treatment alone, which was also associated with an increase in apoptotic cell death. Taken together, these findings suggest that DIBI-mediated iron withdrawal may enhance the effect of chemotherapeutic agents used in breast cancer treatment.