Transferrin-receptor-mediated iron accumulation controls proliferation and glutamate release in glioma cells

High expression of BCAT1 sensitizes AML cells to PARP inhibitor by suppressing DNA damage response

Previous evidence has confirmed that branched-chain aminotransferase-1 (BCAT1), a key enzyme governing branched-chain amino acid (BCAA) metabolism, has a role in cancer aggression partly by restricting αKG levels and inhibiting the activities of the αKG-dependent enzyme family. The oncogenic role of BCAT1, however, was not fully elucidated in acute myeloid leukemia (AML). In this study, we investigated the clinical significance and biological insight of BCAT1 in AML. Using q-PCR, we analyzed BCAT1 mRNAs in bone marrow samples from 332 patients with newly diagnosed AML. High BCAT1 expression independently predicts poor prognosis in patients with AML. We also established BCAT1 knockout (KO)/over-expressing (OE) AML cell lines to explore the underlying mechanisms. We found that BCAT1 affects cell proliferation and modulates cell cycle, cell apoptosis, and DNA damage/repair process. Additionally, we demonstrated that BCAT1 regulates histone methylation by reducing intracellular αKG levels in AML cells. Moreover, high expression of BCAT1 enhances the sensitivity of AML cells to the Poly (ADP-ribose) polymerase (PARP) inhibitor both in vivo and in vitro. Our study has demonstrated that BCAT1 expression can serve as a reliable predictor for AML patients, and PARP inhibitor BMN673 can be used as an effective treatment strategy for patients with high BCAT1 expression. KEY MESSAGES: High expression of BCAT1 is an independent risk factor for poor prognosis in patients with CN-AML. High BCAT1 expression in AML limits intracellular αKG levels, impairs αKG-dependent histone demethylase activity, and upregulates H3K9me3 levels. H3K9me3 inhibits ATM expression and blocks cellular DNA damage repair process. Increased sensitivity of BCAT1 high expression AML to PARP inhibitors may be used as an effective treatment strategy in AML patients.

Potent in vivo efficacy of oral gallium maltolate in treatment-resistant glioblastoma

Background

Treatment-resistant glioblastoma (trGBM) is an aggressive brain tumor with a dismal prognosis, underscoring the need for better treatment options. Emerging data indicate that trGBM iron metabolism is an attractive therapeutic target. The novel iron mimetic, gallium maltolate (GaM), inhibits mitochondrial function via iron-dependent and -independent pathways.

Methods

In vitro irradiated adult GBM U-87 MG cells were tested for cell viability and allowed to reach confluence prior to stereotactic implantation into the right striatum of male and female athymic rats. Advanced MRI at 9.4T was carried out weekly starting two weeks after implantation. Daily oral GaM (50mg/kg) or vehicle were provided on tumor confirmation. Longitudinal MRI parameters were processed for enhancing tumor ROIs in OsiriX 8.5.1 (lite) with Imaging Biometrics Software (Imaging Biometrics LLC). Statistical analyses included Cox proportional hazards regression models, Kaplan-Meier survival plots, linear mixed model comparisons, and t-statistic for slopes comparison as indicator of tumor growth rate.

Results

In this study we demonstrate non-invasively, using longitudinal MRI surveillance, the potent antineoplastic effects of GaM in a novel rat xenograft model of trGBM, as evidenced by extended suppression of tumor growth (23.56 mm3/week untreated, 5.76 mm3/week treated, P < 0.001), a blunting of tumor perfusion, and a significant survival benefit (median overall survival: 30 days untreated, 56 days treated; P < 0.001). The therapeutic effect was confirmed histologically by the presence of abundant cytotoxic cellular swelling, a significant reduction in proliferation markers (P < 0.01), and vessel normalization characterized by prominent vessel pruning, loss of branching, and uniformity of vessel lumina. Xenograft tumors in the treatment group were further characterized by an absence of an invasive edge and a significant reduction in both, MIB-1% and mitotic index (P < 0.01 each). Transferrin receptor and ferroportin expression in GaM-treated tumors illustrated cellular iron deprivation. Additionally, treatment with GaM decreased the expression of pro-angiogenic markers (von Willebrand Factor and VEGF) and increased the expression of anti-angiogenic markers, such as Angiopoietin-2.

Conclusion

Monotherapy with the iron-mimetic GaM profoundly inhibits trGBM growth and significantly extends disease-specific survival in vivo.

Homeostatic iron regulatory protein drives glioblastoma growth via tumor cell-intrinsic and sex-specific responses

Background

Glioblastoma (GBM) displays alterations in iron that drive proliferation and tumor growth. Iron regulation is complex and involves many regulatory mechanisms, including the homeostatic iron regulator (HFE) gene, which encodes the homeostatic iron regulatory protein. While HFE is upregulated in GBM and correlates with poor survival outcomes, the function of HFE in GBM remains unclear.

Methods

We interrogated the impact of cell-intrinsic Hfe expression on proliferation and survival of intracranially implanted animals through genetic gain- and loss-of-function approaches in syngeneic mouse glioma models, along with in vivo immune assessments. We also determined the expression of iron-associated genes and their relationship to survival in GBM using public data sets and used transcriptional profiling to identify differentially expressed pathways in control compared to Hfe-knockdown cells.

Results

Overexpression of Hfe accelerated GBM proliferation and reduced animal survival, whereas suppression of Hfe induced apoptotic cell death and extended survival, which was more pronounced in females and associated with attenuation of natural killer cells and CD8+ T cell activity. Analysis of iron gene signatures in Hfe-knockdown cells revealed alterations in the expression of several iron-associated genes, suggesting global disruption of intracellular iron homeostasis. Further analysis of differentially expressed pathways revealed oxidative stress as the top pathway upregulated following Hfe loss. Hfe knockdown indeed resulted in enhanced 55Fe uptake and generation of reactive oxygen species.

Conclusions

These findings reveal an essential function for HFE in GBM cell growth and survival, as well as a sex-specific interaction with the immune response.

Antisense-oligonucleotide co-micelles with tumor targeting peptides elicit therapeutic effects by inhibiting microRNA-21 in the glioblastoma animal models

INTRODUCTION

miRNA-21 (miR-21) is highly expressed in glioblastoma, facilitating tumor growth by blocking the expression of apoptosis-related genes. Therefore, an antisense microRNA oligonucleotide (AMO) against miR-21 was suggested as a therapeutic nucleic acid for glioblastoma.

OBJECTIVES

AMO21 co-micelles were developed with tumor-targeting T7 peptides as an AMO21 delivery system by intranasal administration.

METHODS

Cholesterol-conjugated AMO21 (AMO21c) was mixed with cholesterol-conjugated T7 peptides (T7c) to produce tumor-targeted co-micelles. Physical characterization was performed by dynamic light scattering, gel retardation assay, scanning electron microscope and heparin competition assay. In vitro transfection efficiency to C6 glioblastoma cells was measured by flow cytometry. The AMO21c/T7c co-micelles were administered by intranasal instillation into the brain of intracranial glioblastoma rat models. Scrambled T7 (scrT7) and scrambled AMO21c (scrAMO21c) were used as a negative control. The therapeutic effects of the AMO21c/T7c co-micelles were evaluated by real time RT-PCR, immunohistochemistry, TUNEL assay, and Nissl staining.

RESULTS

The formation of the AMO21c/T7c co-micelles was confirmed in gel retardation and heparin competition assays. The highest delivery efficiency in vitro was achieved at a 1:10 wt ratio of AMO21c/T7c. The AMO21c/T7c co-micelles had higher delivery efficiency into C6 glioblastoma cells than naked AMO21c or AMO21c/lipofectamine complexes. After intranasal administration into the intracranial glioblastoma models, the delivery efficiency of the co-micelles into the brain was also higher than those of naked AMO21c and AMO21c/scrambled T7c. Thanks to their enhanced delivery efficiency, the AMO21c/T7c co-micelles downregulated miR-21, inducing the production of the pro-apoptotic phosphatase and tensin homolog (PTEN) and programmed cell death 4 (PDCD4) proteins in the tumor tissues. The tumor size was reduced by the AMO21c/T7c co-micelles more effectively than naked AMO21c, AMO21c/lipofectamine, or scrAMO21c/T7c treatment.

CONCLUSION

The results suggest that the co-micelles of AMO21c and T7c may be an efficient delivery system into a brain tumor through intranasal administration.

Ferroptosis-related gene MTF-1 as a novel prognostic biomarker in low-grade glioma and its correlation with immune infiltration

Background

Metal-responsive transcription factor-1 performs a necessary position in a range of cancers. It is unknown, though, how the prognosis of patients with low-grade gliomas is related to immune infiltration.

Method

The Cancer Genome Atlas database was used in this investigation to evaluate MTF-1 transcription in low-grade glioma and healthy brain tissues, and immunohistochemistry was used to confirm MTF-1 levels. By using functional enrichment analysis and R software, the putative biological roles and signaling pathways connected to MTF-1 in LGG as well as its prognostic significance were investigated. Further research was done on the connection involving MTF-1 and tumor mutational burden in LGG. Finally, the research evaluated how MTF-1 and immune cell infiltration are related.

Results

We noticed that the WHO grade, 1p/19q codeletion, and older age were all substantially linked with MTF-1 overexpression in low-grade gliomas. OS and disease-specific survival were significantly lowered as a result of MTF-1 transcription. MTF-1 was recognized as an independent OS prognostic predictor with a poor prognosis by multifactorial Cox analysis. Functional enrichment analysis revealed that the primary enrichment pathways were chemical carcinogenesis-receptor activation and the generation of miRNAs implicated in gene suppression by miRNA. Additionally, there was a negative correlation between MTF-1 overexpression and the degree of immune cell infiltration in neutrophils and DC.

Conclusion

MTF-1 may be a novel prognostic biomarker.

Ferroptosis and PPAR-gamma in the limelight of brain tumors and edema

Human malignant brain tumors such as gliomas are devastating due to the induction of cerebral edema and neurodegeneration. A major contributor to glioma-induced neurodegeneration has been identified as glutamate. Glutamate promotes cell growth and proliferation in variety of tumor types. Intriguently, glutamate is also an excitatory neurotransmitter and evokes neuronal cell death at high concentrations. Even though glutamate signaling at the receptor and its downstream effectors has been extensively investigated at the molecular level, there has been little insight into how glutamate enters the tumor microenvironment and impacts on metabolic equilibration until recently. Surprisingly, the 12 transmembrane spanning tranporter xCT (SLC7A11) appeared to be a major player in this process, mediating glutamate secretion and ferroptosis. Also, PPARγ is associated with ferroptosis in neurodegeneration, thereby destroying neurons and causing brain swelling. Although these data are intriguing, tumor-associated edema has so far been quoted as of vasogenic origin. Hence, glutamate and PPARγ biology in the process of glioma-induced brain swelling is conceptually challenging. By inhibiting xCT transporter or AMPA receptors in vivo, brain swelling and peritumoral alterations can be mitigated. This review sheds light on the role of glutamate in brain tumors presenting the conceptual challenge that xCT disruption causes ferroptosis activation in malignant brain tumors. Thus, interfering with glutamate takes center stage in forming the basis of a metabolic equilibration approach.

SCARA5 induced ferroptosis to effect ESCC proliferation and metastasis by combining with Ferritin light chain

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) remains one of the most lethal cancers worldwide accompany with an extremely poor prognosis. Therefore, this study aims to screen for new molecules affecting ESCC and explore their mechanisms of action to provide ideas for targeted therapies for ESCC.

METHODS

Firstly, we screened out the membrane protein SCARA5 by high-throughput sequencing of the ESCC patient tissues, and RT-qPCR and WB were used to verify the differential expression of SCARA5 in esophageal cell lines, and IHC analyzed the expression localization of SCARA5 in ESCC tissue. Then, flow cytometry, wound healing assay, Transwell assay and CCK-8 assay were used to explore the effects of SCARA5 on cell cycle, migration and invasion as well as cell proliferation activity of esophageal squamous carcinoma cells. Meanwhile, transmission electron microscopy was used to detect changes in cellular mitochondrial morphology, and flow cytometry were used to detect changes in intracellular reactive oxygen metabolism, and immunofluorescence and flow cytometry were used to detect changes in intracellular Fe²⁺. Mechanistically, co-immunoprecipitation was used to detect whether SCARA5 binds to ferritin light chain, and ferroptosis-related protein expression was detected by WB. Finally, the tumor xenograft model was applied to validation the role of SCARA5 tumor growth inhibition in vivo.

RESULTS

We found that SCARA5 was aberrantly decreased in ESCC tissues and cell lines. Furthermore, we confirmed that SCARA5 suppressed the cell cycle, metastasis and invasion of ESCC cells. Meanwhile, we also found that overexpression of SCARA5 caused changes in mitochondrial morphology, accumulation of intracellular reactive oxygen species and increased intracellular Fe²⁺ in ESCC cells, which induced ferroptosis in ESCC cells. Mechanically, we validated that SCARA5 combined with ferritin light chain and increased intracellular Fe²⁺. As well as, overexpression SCARA5 induced ferroptosis by increasing ferritin light chain in nude mice subcutaneous tumors and inhibited the growth of nude mice subcutaneous tumors.

CONCLUSION

Collectively, our findings demonstrated that SCARA5 suppressed the proliferation and metastasis of ESCC by triggering ferroptosis through combining with ferritin light chain.

Emerging roles of ferroptosis in glioma

Glioma is the most common primary malignant tumor in the central nervous system, and directly affects the quality of life and cognitive function of patients. Ferroptosis, is a new form of regulated cell death characterized by iron-dependent lipid peroxidation. Ferroptosis is mainly due to redox imbalance and involves multiple intracellular biology processes, such as iron metabolism, lipid metabolism, and antioxidants synthesis. Induction of ferroptosis could be a new target for glioma treatment, and ferroptosis-related processes are associated with chemoresistance and radioresistance in glioma. In the present review, we provide the characteristics, key regulators and pathways of ferroptosis and the crosstalk between ferroptosis and other programmed cell death in glioma, we also proposed the application and prospect of ferroptosis in the treatment of glioma.

A role for ceruloplasmin in the control of human glioblastoma cell responses to radiation

Background

Glioblastoma (GB) is the most common and most aggressive malignant brain tumor. In understanding its resistance to conventional treatments, iron metabolism and related pathways may represent a novel avenue. As for many cancer cells, GB cell growth is dependent on iron, which is tightly involved in red-ox reactions related to radiotherapy effectiveness. From new observations indicating an impact of RX radiations on the expression of ceruloplasmin (CP), an important regulator of iron metabolism, the aim of the present work was to study the functional effects of constitutive expression of CP within GB lines in response to beam radiation depending on the oxygen status (21% O₂ versus 3% O₂).

Methods and results

After analysis of radiation responses (Hoechst staining, LDH release, Caspase 3 activation) in U251-MG and U87-MG human GB cell lines, described as radiosensitive and radioresistant respectively, the expression of 9 iron partners (TFR1, DMT1, FTH1, FTL, MFRN1, MFRN2, FXN, FPN1, CP) were tested by RTqPCR and western blots at 3 and 8 days following 4 Gy irradiation. Among those, only CP was significantly downregulated, both at transcript and protein levels in the two lines, with however, a weaker effect in the U87-MG, observable at 3% O₂. To investigate specific role of CP in GB radioresistance, U251-MG and U87-MG cells were modified genetically to obtain CP depleted and overexpressing cells, respectively. Manipulation of CP expression in GB lines demonstrated impact both on cell survival and on activation of DNA repair/damage machinery (γH2AX); specifically high levels of CP led to increased production of reactive oxygen species, as shown by elevated levels of superoxide anion, SOD1 synthesis and cellular Fe2 + .

Conclusions

Taken together, these in vitro results indicate for the first time that CP plays a positive role in the efficiency of radiotherapy on GB cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09808-6.

Correlation of Ferroptosis and Other Types of Cell Death in Neurodegenerative Diseases

Ferroptosis is defined as an iron-dependent, non-apoptotic cell death pathway, with specific morphological phenotypes and biochemical changes. There is a growing realization that ferroptosis has significant implications for several neurodegenerative diseases. Even though ferroptosis is different from other forms of programmed death such as apoptosis and autophagic death, they involve a number of common protein molecules. This review focuses on current research on ferroptosis and summarizes the cross-talk among ferroptosis, apoptosis, and autophagy that are implicated in neurodegenerative diseases. We hope that this information provides new ideas for understanding the mechanisms and searching for potential therapeutic approaches and prevention of neurodegenerative diseases.

Altered Elemental Distribution in Male Rat Brain Tissue as a Predictor of Glioblastoma Multiforme Growth-Studies Using SR-XRF Microscopy

Glioblastoma multiforme (GBM) is a particularly malignant primary brain tumor. Despite enormous advances in the surgical treatment of cancer, radio- and chemotherapy, the average survival of patients suffering from this cancer does not usually exceed several months. For obvious ethical reasons, the search and testing of the new drugs and therapies of GBM cannot be carried out on humans, and for this purpose, animal models of the disease are most often used. However, to assess the efficacy and safety of the therapy basing on these models, a deep knowledge of the pathological changes associated with tumor development in the animal brain is necessary. Therefore, as part of our study, the synchrotron radiation-based X-ray fluorescence microscopy was applied for multi-elemental micro-imaging of the rat brain in which glioblastoma develops. Elemental changes occurring in animals after the implantation of two human glioma cell lines as well as the cells taken directly from a patient suffering from GBM were compared. Both the extent and intensity of elemental changes strongly correlated with the regions of glioma growth. The obtained results showed that the observation of elemental anomalies accompanying tumor development within an animal's brain might facilitate our understanding of the pathogenesis and progress of GBM and also determine potential biomarkers of its extension. The tumors appearing in a rat's brain were characterized by an increased accumulation of Fe and Se, whilst the tissue directly surrounding the tumor presented a higher accumulation of Cu. Furthermore, the results of the study allow us to consider Se as a potential elemental marker of GBM progression.

Identification of Iron Metabolism-Related Genes as Prognostic Indicators for Lower-Grade Glioma

Lower-grade glioma (LGG) is characterized by genetic and transcriptional heterogeneity, and a dismal prognosis. Iron metabolism is considered central for glioma tumorigenesis, tumor progression and tumor microenvironment, although key iron metabolism-related genes are unclear. Here we developed and validated an iron metabolism-related gene signature LGG prognosis. RNA-sequence and clinicopathological data from The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) were downloaded. Prognostic iron metabolism-related genes were screened and used to construct a risk-score model via differential gene expression analysis, univariate Cox analysis, and the Least Absolute Shrinkage and Selection Operator (LASSO)-regression algorithm. All LGG patients were stratified into high- and low-risk groups, based on the risk score. The prognostic significance of the risk-score model in the TCGA and CGGA cohorts was evaluated with Kaplan-Meier (KM) survival and receiver operating characteristic (ROC) curve analysis. Risk- score distributions in subgroups were stratified by age, gender, the World Health Organization (WHO) grade, isocitrate dehydrogenase 1 (IDH1) mutation status, the O6-methylguanine-DNA methyl-transferase (MGMT) promoter-methylation status, and the 1p/19q co-deletion status. Furthermore, a nomogram model with a risk score was developed, and its predictive performance was validated with the TCGA and CGGA cohorts. Additionally, the gene set enrichment analysis (GSEA) identified signaling pathways and pathological processes enriched in the high-risk group. Finally, immune infiltration and immune checkpoint analysis were utilized to investigate the tumor microenvironment characteristics related to the risk score. We identified a prognostic 15-gene iron metabolism-related signature and constructed a risk-score model. High risk scores were associated with an age of > 40, wild-type IDH1, a WHO grade of III, an unmethylated MGMT promoter, and 1p/19q non-codeletion. ROC analysis indicated that the risk-score model accurately predicted 1-, 3-, and 5-year overall survival rates of LGG patients in the both TCGA and CGGA cohorts. KM analysis showed that the high-risk group had a much lower overall survival than the low-risk group (P < 0.0001). The nomogram model showed a strong ability to predict the overall survival of LGG patients in the TCGA and CGGA cohorts. GSEA analysis indicated that inflammatory responses, tumor-associated pathways, and pathological processes were enriched in high-risk group. Moreover, a high risk score correlated with the infiltration immune cells (dendritic cells, macrophages, CD4+ T cells, and B cells) and expression of immune checkpoint (PD1, PDL1, TIM3, and CD48). Our prognostic model was based on iron metabolism-related genes in LGG, can potentially aid in LGG prognosis, and provides potential targets against gliomas.

WDR45 Mutation Impairs the Autophagic Degradation of Transferrin Receptor and Promotes Ferroptosis

WDR45 is an autophagy-related protein that involves in the formation of autophagosome. Mutations in WDR45 lead to the impairment of autophagy which is associated with the human β-propeller protein-associated neurodegeneration (BPAN). However, the relationship between autophagy and brain iron accumulation in patients with BPAN remains unclear. Here, we demonstrated that transferrin receptor (TfRC) which is critical for the iron import of cells was degraded via autophagy. TfRC was accumulated after the inhibition of autophagy by treatment with autophagic inhibitor chloroquine or knockdown of ATG2A. The intracellular iron content was increased in cells overexpressing TfRC or mutant WDR45, however, ferritin H (FTH) chain was decreased. Increased TfRC and simultaneously decreased FTH consequently resulted in an elevated level of ferrous iron (Fe²⁺) which further promoted cell ferroptosis, demonstrated by the increased lipid peroxidation and reactive oxygen species (ROS) and the decreased glutathione peroxidase 4 (GPX4) and cell viability. Taken together, these findings provide a piece of important evidence that WDR45 deficiency impairs autophagic degradation of TfRC, therefore leading to iron accumulation, and the elevated iron promotes ferroptosis which may contribute to the progression of BPAN.

Value of Ferritin Heavy Chain (FTH1) Expression in Diagnosis and Prognosis of Renal Cell Carcinoma

BACKGROUND Serum ferritin is a useful tumor marker for renal cell carcinoma (RCC). However, the expression of ferritin heavy chain (FTH1), the main subunit of ferritin, is unclear in primary RCC tissues. In this study, we investigated FTH1 mRNA expression and its diagnostic and prognostic value in RCC. MATERIAL AND METHODS The mRNA expression of FTH1 was analyzed using including Oncomine, Gene Expression Omnibus, and Cancer Genome Atlas datasets, while the protein level of FTH1 was analyzed using the Human Protein Atlas database. The associations between FTH1 and clinicopathologic characteristics and survival time and Cox multivariate survival analysis were analyzed using SPSS 22.0 software. A meta-analysis was performed to assess consistency of FTH1 expression. GO, KEGG, and PPI analyses were used to predict biological functions. RESULTS According to TCGA data, overexpression of FTH1 was detected in 890 RCC tissues (15.2904±0.63157) compared to 129 normal kidney tissues (14.4502±0.51523, p<0.001). Among the clinicopathological characteristics evaluated, patients with increased pathologic T staging, lymph node metastasis, and distant metastasis were significantly associated with higher expression of FTH1. Elevated FTH1 mRNA levels were correlated with worse prognosis of RCC patients. Cox multivariate survival analysis indicated that age, stage, and M stage were predictors of poor prognosis in patients with RCC. CONCLUSIONS Our data suggest that FTH1 expression is an effective prognostic and diagnosis biomarker for RCC.

Alterations in Cellular Iron Metabolism Provide More Therapeutic Opportunities for Cancer

Iron is an essential element for the growth and proliferation of cells. Cellular iron uptake, storage, utilization and export are tightly regulated to maintain iron homeostasis. However, cellular iron metabolism pathways are disturbed in most cancer cells. To maintain rapid growth and proliferation, cancer cells acquire large amounts of iron by altering expression of iron metabolism- related proteins. In this paper, normal cellular iron metabolism and the alterations of iron metabolic pathways in cancer cells were summarized. Therapeutic strategies based on targeting the altered iron metabolism were also discussed and disrupting redox homeostasis by intracellular high levels of iron provides new insight for cancer therapy. Altered iron metabolism constitutes a promising therapeutic target for cancer therapy.

Vacuolar ATPase as a possible therapeutic target in human acute myeloid leukemia

INTRODUCTION

V-ATPase is a proton pump expressed both in the membrane of intracellular organelles (e.g. endosomes, lysosomes, Golgi structures) and the plasma membrane. It is an important regulator of organellar functions, intracellular molecular trafficking, intercellular communication and intracellular signaling. It is therefore considered as a possible therapeutic target in the treatment of human malignancies. Areas covered: Relevant publications were identified through literature searches in the PubMed database. We searched for original articles and reviews describing the possible importance of V-ATPase for leukemogenesis and chemosensitivity in human myeloid cells, especially acute myeloid leukemia (AML) cells. Expert commentary: The expression of V-ATPase in the primary human AML cells varies between patients, and high levels are associated with high constitutive release of a wide range of soluble mediators. Several of the molecules included in the V-ATPase interactome may also be important in leukemogenesis and/or development of chemoresistance in human AML. Therapeutic targeting of V-ATPase should therefore be regarded as a possible therapeutic strategy in human AML, but the efficiency of such targeting will probably differ between patients. The possibility of toxicity, especially hematological toxicity and immunosuppression, also has to be clarified.

Patients with acute myeloid leukemia can be subclassified based on the constitutive cytokine release of the leukemic cells; the possible clinical relevance and the importance of cellular iron metabolism

OBJECTIVE

Acute myeloid leukaemia (AML) is a heterogeneous malignancy; we studied how the constitutive cytokine release by the AML cells varies among patients.

METHODS

We investigated the constitutive release of 28 mediators during in vitro culture for 79 consecutive patients.

RESULTS

Constitutive cytokine release profiles differed among patients, and hierarchical clustering identified three subsets with high, intermediate and low release, respectively. The high-release subset showed high levels of most mediators, usually monocytic differentiation as well as altered mRNA expression of proteins involved in intracellular iron homeostasis and molecular trafficking; this subset also included 4 out of 6 patients with inv(16). Spontaneous in vitro apoptosis did not differ among the subsets. For the high-release patients, cytokines were released both by CD34⁺ and CD34^- cells. The mRNA and released protein levels showed statistically significant correlations only for eleven of the cytokines. The overall survival after intensive anti-leukemic therapy was significantly higher for high-release compared with low-release patients. Pharmacological targeting of iron metabolism (iron chelation, transferrin receptor blocking) altered the cytokine release profile.

CONCLUSIONS

Subclassification of AML patients based on the constitutive cytokine release may be clinically relevant and a part of a low-risk (i.e. chemosensitive) AML cell phenotype.

Aberrations in the Iron Regulatory Gene Signature Are Associated with Decreased Survival in Diffuse Infiltrating Gliomas

Iron is a tightly regulated micronutrient with no physiologic means of elimination and is necessary for cell division in normal tissue. Recent evidence suggests that dysregulation of iron regulatory proteins may play a role in cancer pathophysiology. We use public data from The Cancer Genome Atlas (TCGA) to study the association between survival and expression levels of 61 genes coding for iron regulatory proteins in patients with World Health Organization Grade II-III gliomas. Using a feature selection algorithm we identified a novel, optimized subset of eight iron regulatory genes (STEAP3, HFE, TMPRSS6, SFXN1, TFRC, UROS, SLC11A2, and STEAP4) whose differential expression defines two phenotypic groups with median survival differences of 52.3 months for patients with grade II gliomas (25.9 vs. 78.2 months, p< 10⁻³), 43.5 months for patients with grade III gliomas (43.9 vs. 87.4 months, p = 0.025), and 54.0 months when considering both grade II and III gliomas (79.9 vs. 25.9 months, p < 10⁻⁵).

RNA Editing-Systemic Relevance and Clue to Disease Mechanisms?

Recent advances in sequencing technologies led to the identification of a plethora of different genes and several hundreds of amino acid recoding edited positions. Changes in editing rates of some of these positions were associated with diseases such as atherosclerosis, myopathy, epilepsy, major depression disorder, schizophrenia and other mental disorders as well as cancer and brain tumors. This review article summarizes our current knowledge on that front and presents glycine receptor C-to-U RNA editing as a first example of disease-associated increased RNA editing that includes assessment of disease mechanisms of the corresponding gene product in an animal model.

Low molecular weight protein tyrosine phosphatase: Multifaceted functions of an evolutionarily conserved enzyme

Originally identified as a low molecular weight acid phosphatase, LMW-PTP is actually a protein tyrosine phosphatase that acts on many phosphotyrosine-containing cellular proteins that are primarily involved in signal transduction. Differences in sequence, structure, and substrate recognition as well as in subcellular localization in different organisms enable LMW-PTP to exert many different functions. In fact, during evolution, the LMW-PTP structure adapted to perform different catalytic actions depending on the organism type. In bacteria, this enzyme is involved in the biosynthesis of group 1 and 4 capsules, but it is also a virulence factor in pathogenic strains. In yeast, LMW-PTPs dephosphorylate immunophilin Fpr3, a peptidyl-prolyl-cis-trans isomerase member of the protein chaperone family. In humans, LMW-PTP is encoded by the ACP1 gene, which is composed of three different alleles, each encoding two active enzymes produced by alternative RNA splicing. In animals, LMW-PTP dephosphorylates a number of growth factor receptors and modulates their signalling processes. The involvement of LMW-PTP in cancer progression and in insulin receptor regulation as well as its actions as a virulence factor in a number of pathogenic bacterial strains may promote the search for potent, selective and bioavailable LMW-PTP inhibitors.

Iron metabolism: a double-edged sword in the resistance of glioblastoma to therapies

Glioblastoma (GBM), the deadliest primary tumor of the central nervous system (CNS), is a clear illustration of the resistance of cancer cells to conventional therapies. Application of combinatorial strategies able to overcome pivotal factors of GBM resistance, particularly within the resection margins, represents an essential issue. This review focuses on the role of iron metabolism in GBM progression and resistance to therapy, and the impact of its pharmaceutical modulation on the disease. Iron, through its involvement in many biological processes, is a key factor in the control of cell behavior and cancer biology. Therefore, targeting cellular iron signaling or taking advantage of its dysregulation in cancer cells may lead to new opportunities for improving treatments and drug delivery in GBM.

Effects of iron ions and iron chelation on the efficiency of experimental radiotherapy of animals with gliomas

We evaluated the effect of iron ion chelation on the growth of gliomas and radiotherapy efficiency in tumor-bearing animals. The rats with transplanted glioma-35 received iron-containing water; desferroxamine was injected for metal chelation. Long-term treatment with iron-containing water promoted glioma growth in rats and improved the efficiency of radiotherapy due to combination of apoptosis and ferroptosis. Desferroxamine reduced the efficiency of this treatment and was inessential for the efficiency of radiotherapy alone.

A novel model for brain iron uptake: introducing the concept of regulation

Neurologic disorders such as Alzheimer's, Parkinson's disease, and Restless Legs Syndrome involve a loss of brain iron homeostasis. Moreover, iron deficiency is the most prevalent nutritional concern worldwide with many associated cognitive and neural ramifications. Therefore, understanding the mechanisms by which iron enters the brain and how those processes are regulated addresses significant global health issues. The existing paradigm assumes that the endothelial cells (ECs) forming the blood-brain barrier (BBB) serve as a simple conduit for transport of transferrin-bound iron. This concept is a significant oversimplification, at minimum failing to account for the iron needs of the ECs. Using an in vivo model of brain iron deficiency, the Belgrade rat, we show the distribution of transferrin receptors in brain microvasculature is altered in luminal, intracellular, and abluminal membranes dependent on brain iron status. We used a cell culture model of the BBB to show the presence of factors that influence iron release in non-human primate cerebrospinal fluid and conditioned media from astrocytes; specifically apo-transferrin and hepcidin were found to increase and decrease iron release, respectively. These data have been integrated into an interactive model where BBB ECs are central in the regulation of cerebral iron metabolism.

Targeting fibronectins of glioma extracellular matrix by CLT1 peptide-conjugated nanoparticles

The abundant extracellular matrix (ECM) in the glioma microenvironment play a critical role in the maintenance of glioma morphology, glioma cells differentiation and proliferation, but little has been done to understand the feasibility of ECM as the therapeutic target for glioma therapy. In this study, a drug delivery system targeting fibronectins (FNs), a prevailing component in the ECM of many solid tumors, was constructed for glioma therapy based on the interaction between the abundant FNs in glioma tissues and the FNs-targeting moiety CLT1 peptide. CLT1 peptide was successfully conjugated to PEG-PLA nanoparticles (CNP). FNs were demonstrated to be highly expressed in the ECM of glioma spheroids in vitro and glioma tissues in vivo. CLT1 modification favored targeting nanoparticles penetration into the core of glioma spheroids and consequently induced more severe inhibitive effects on glioma spheroids growth than traditional NP. In vivo imaging, ex vivo imaging and glioma tissue slides showed that CNP enhanced nanoparticles retention in glioma site, distributed more extensively and more deeply into glioma tissues than that of conventional NP, and mainly located in glioma cells rather than in extracellular matrix as conventional NP. Pharmacodynamics outcomes revealed that the median survival time of glioma-bearing mice models treated with paclitaxel-loaded CNP (CNP-PTX) was significantly prolonged when compared with that of any other group. TUNEL assay demonstrated that more extensive cell apoptosis was induced by CNP-PTX treatment compared with other treatments. Altogether, these promising results indicated that this ECM-targeting drug delivery system enhanced retention and glioma cell uptake of nanoparticles and might have a great potential for glioma therapy in clinical applications.

Neural and oligodendrocyte progenitor cells: transferrin effects on cell proliferation

NSC (neural stem cells)/NPC (neural progenitor cells) are multipotent and self-renew throughout adulthood in the SVZ (subventricular zone) of the mammalian CNS (central nervous system). These cells are considered interesting targets for CNS neurodegenerative disorder cell therapies, and understanding their behaviour in vitro is crucial if they are to be cultured prior to transplantation. We cultured the SVZ tissue belonging to newborn rats under the form of NS (neurospheres) to evaluate the effects of Tf (transferrin) on cell proliferation. The NS were heterogeneous in terms of the NSC/NPC markers GFAP (glial fibrillary acidic protein), Nestin and Sox2 and the OL (oligodendrocyte) progenitor markers NG2 (nerve/glia antigen 2) and PDGFRα (platelet-derived growth factor receptor α). The results of this study indicate that aTf (apoTransferrin) is able to increase cell proliferation of SVZ-derived cells in vitro, and that these effects were mediated at least in part by the TfRc1 (Tf receptor 1). Since OPCs (oligodendrocyte progenitor cells) represent a significant proportion of the proliferating cells in the SVZ-derived primary cultures, we used the immature OL cell line N20.1 to show that Tf was able to augment the proliferation rate of OPC, either by adding aTf to the culture medium or by overexpressing rat Tf in situ. The culture medium supplemented with ferric iron, together with aTf, increased the DNA content, while ferrous iron did not. The present work provides data that could have a potential application in human cell replacement therapies for neurodegenerative disease and/or CNS injury that require the use of in vitro amplified NPCs.

Immunogenicity and toxicity of transferrin receptor-targeted hybrid peptide as a potent anticancer agent

PURPOSE

Transferrin receptor (TfR) is a cell membrane-associated glycoprotein involved in the cellular uptake of iron and the regulation of cell growth. Recent studies have shown elevated expression levels of TfR on cancer cells compared with normal cells. We previously designed a TfR-lytic hybrid peptide, which combines the TfR-binding peptide and a lytic peptide, and reported that it bound specifically to TfR and selectively killed cancer cells. Furthermore, the intravenous administration of TfR-lytic peptide in an athymic mouse model significantly inhibited tumor progression. To evaluate the immunogenicity of this peptide as a novel and potent anticancer agent, we investigated whether TfR-lytic hybrid peptide elicits cellular and humoral immune responses to produce antibodies. We also examined the toxicity of this peptide in syngeneic mice.

METHODS

We performed hematologic and blood chemistry test and histological analysis and assessed hemolytic activity to check toxicity. To evaluate the immunogenicity, measurement of murine interferon-gamma and detection of TfR-lytic-specific antibody by ELISA were demonstrated.

RESULTS

No T cell immune response or antibodies were detected in the group treated with TfR-lytic hybrid peptide. No hematologic toxicity, except for a decrease in leukocytes, was observed, and no remarkable influence on metabolic parameters and organs (liver, kidney, and spleen) was noted.

CONCLUSIONS

Therefore, TfR-lytic hybrid peptide might provide an alternative therapeutic option for patients with cancer.

Conjugation of functionalized SPIONs with transferrin for targeting and imaging brain glial tumors in rat model

Currently, effective and specific diagnostic imaging of brain glioma is a major challenge. Nanomedicine plays an essential role by delivering the contrast agent in a targeted manner to specific tumor cells, leading to improvement in accurate diagnosis by good visualization and specific demonstration of tumor cells. This study investigated the preparation and characterization of a targeted MR contrast agent, transferrin-conjugated superparamagnetic iron oxide nanoparticles (Tf-SPIONs), for brain glioma detection. MR imaging showed the obvious contrast change of brain glioma before and after administration of Tf-SPIONs in C6 glioma rat model in vivo on T2 weighted imaging. Significant contrast enhancement of brain glioma could still be clearly seen even 48 h post injection, due to the retention of Tf-SPIONs in cytoplasm of tumor cells which was proved by Prussian blue staining. Thus, these results suggest that Tf-SPIONs could be a potential targeting MR contrast agent for the brain glioma.

MR imaging features of high-grade gliomas in murine models: how they compare with human disease, reflect tumor biology, and play a role in preclinical trials

Murine models are the most commonly used and best investigated among the animal models of HGG. They constitute an important weapon in the development and testing of new anticancer drugs and have long been used in preclinical trials. Neuroimaging methods, particularly MR imaging, offer important advantages for the evaluation of treatment response: shorter and more reliable treatment end points and insight on tumor biology and physiology through the use of functional imaging DWI, PWI, BOLD, and MR spectroscopy. This functional information has been progressively consolidated as a surrogate marker of tumor biology and genetics and may play a pivotal role in the assessment of specifically targeted drugs, both in clinical and preclinical trials. The purpose of this Research Perspectives was to compile, summarize, and critically assess the available information on the neuroimaging features of different murine models of HGGs, and explain how these correlate with human disease and reflect tumor biology.

Transferrin receptor 2 is frequently and highly expressed in glioblastomas

Under physiological conditions, transferrin receptor 2 (TfR2) is expressed in the liver and its balance is related to the cell cycle rather than to intracellular iron levels. We recently showed that TfR2 is highly expressed in glioblastoma cell lines. Here, we demonstrate that, in these cells, TfR2 appears to localize in lipid rafts, induces extracellular signal-regulated kinase 1/2 phosphorylation after transferrin binding, and contributes to cell proliferation, as shown by RNA silencing experiments. In vitro hypoxic conditions induce a significant TfR2 up-regulation, suggesting a role in tumor angiogenesis. As assessed by immunohistochemistry, the level of TfR2 expression in astrocytic tumors is related to histologic grade, with the highest expression observed in glioblastomas. The level of TfR2 expression represents a favorable prognostic factor, which is associated with the higher sensitivity to temozolomide of TfR2-positive tumor cells in vitro. The endothelial cells of glioblastoma vasculature also stain for TfR2, whereas those of the normal brain vessels do not. Importantly, TfR2 is expressed by the subpopulation of glioblastoma cells with properties of cancer-initiating cells. TfR2-positive glioblastoma cells retain their TfR2 expression on xenografting in immunodeficient mice. In conclusion, our observations demonstrate that TfR2 is a neoantigen for astrocytomas that seems attractive for developing target therapies.

Quantitative proteomic analysis of oligodendrogliomas with and without 1p/19q deletion

Approximately 50-80% of oligodendrogliomas demonstrate a combined loss of chromosome 1p and 19q. Chromosome 1p/19q deletion, appearing early in tumorigenesis, is associated with improved clinical outcomes, including response to chemotherapy and radiation. Although many hypotheses have been proposed, the molecular mechanisms underlying improved clinical outcomes with 1p/19q deletion in oligodendrogliomas have not been characterized fully. To investigate the molecular differences between oligodendrogliomas, we employed an unbiased proteomic approach using microcapillary liquid chromatography mass spectrometry, along with a quantitative technique called isotope-coded affinity tags, on patient samples of grade II oligodendrogliomas. Following conventional biochemical separation of pooled tumor tissue from five samples of undeleted and 1p/19q deleted grade II oligodendrogliomas into nuclei-, mitochondria-, and cytosol-enriched fractions, relative changes in protein abundance were quantified. Among the 442 total proteins identified, 163 nonredundant proteins displayed significant changes in relative abundance in at least one of the three fractions between oligodendroglioma with and without 1p/19q deletion. Bioinformatic analyses of differentially regulated proteins supported the potential importance of metabolism and invasion/migration to the codeleted phenotype. A subset of altered proteins, including the pro-invasive extracellular matrix protein BCAN, was further validated by Western blotting as candidate markers for the more aggressive undeleted phenotype. These studies demonstrate the utility of proteomic analysis to identify candidate biological motifs and molecular mechanisms that drive differential malignancy related to 1p19q phenotypes. Future analysis of larger patient samples are warranted to further refine biomarker panels to predict biological behavior and assist in the identification of deleted gene products that define the 1p/19q phenotype.