The polyamine catabolic enzyme SAT1 modulates tumorigenesis and radiation response in GBM

The MUC1-HIF-1α signaling axis regulates pancreatic cancer pathogenesis through polyamine metabolism remodeling

Dysregulation of polyamine metabolism has been implicated in cancer initiation and progression; however, the mechanism of polyamine dysregulation in cancer is not fully understood. In this study, we investigated the role of MUC1, a mucin protein overexpressed in pancreatic cancer, in regulating polyamine metabolism. Utilizing pancreatic cancer patient data, we noted a positive correlation between MUC1 expression and the expression of key polyamine metabolism pathway genes. Functional studies revealed that knockdown of spermidine/spermine N1-acetyltransferase 1 (SAT1), a key enzyme involved in polyamine catabolism, attenuated the oncogenic functions of MUC1, including cell survival and proliferation. We further identified a regulatory axis whereby MUC1 stabilized hypoxia-inducible factor (HIF-1α), leading to increased SAT1 expression, which in turn induced carbon flux into the tricarboxylic acid cycle. MUC1-mediated stabilization of HIF-1α enhanced the promoter occupancy of the latter on SAT1 promoter and corresponding transcriptional activation of SAT1, which could be abrogated by pharmacological inhibition of HIF-1α or CRISPR/Cas9-mediated knockout of HIF1A. MUC1 knockdown caused a significant reduction in the levels of SAT1-generated metabolites, N1-acetylspermidine and N8-acetylspermidine. Given the known role of MUC1 in therapy resistance, we also investigated whether inhibiting SAT1 would enhance the efficacy of FOLFIRINOX chemotherapy. By utilizing organoid and orthotopic pancreatic cancer mouse models, we observed that targeting SAT1 with pentamidine improved the efficacy of FOLFIRINOX, suggesting that the combination may represent a promising therapeutic strategy against pancreatic cancer. This study provides insights into the interplay between MUC1 and polyamine metabolism, offering potential avenues for the development of treatments against pancreatic cancer.

Ferroptosis, a subtle talk between immune system and cancer cells: To be or not to be?

Ferroptosis, an established form of programmed cell death discovered in 2012, is characterized by an imbalance in iron metabolism, lipid metabolism, and antioxidant metabolism. Activated CD8 + T cells can trigger ferroptosis in tumor cells by releasing interferon-γ, which initiates the ferroptosis program. Despite the remarkable progress made in treating various tumors with immunotherapy, such as anti-PD1/PDL1, there are still significant challenges to overcome, including limited treatment options and drug resistance. In this review, we exam the potential biological significance of the ferroptosis phenotype using bioinformatics and review the latest advancements in understanding the mechanism of ferroptosis-mediated anti-tumor immunotherapy. Furthermore, we revisit the host immune system, immune microenvironment, ferroptotic defense system, metabolic reprogramming, and key genes that regulate the occurrence and resistance of ferroptosis of tumor cell. Additionally, several immune-combined ferroptosis treatment strategies were put forward to improve immunotherapy efficacy and to provide new insights into reversing anti-tumor immune drug resistance.

MYC-driven U2SURP regulates alternative splicing of SAT1 to promote triple-negative breast cancer progression

Triple-negative breast cancer (TNBC), although highly lethal, lacks validated therapeutic targets. Here, we report that U2 snRNP-associated SURP motif-containing protein (U2SURP), a poorly defined member of the serine/arginine rich protein family, was significantly upregulated in TNBC tissues, and its high expression was associated with poor prognosis of TNBC patients. MYC, a frequently amplified oncogene in TNBC tissues, enhanced U2SURP translation through an eIF3D (eukaryotic translation initiation factor 3 subunit D)-dependent mechanism, resulting in the accumulation of U2SURP in TNBC tissues. Functional assays revealed that U2SURP played an important role in facilitating tumorigenesis and metastasis of TNBC cells both in vitro and in vivo. Intriguingly, U2SURP had no significant effects on proliferative, migratory, and invasive potential of normal mammary epithelial cells. Furthermore, we found that U2SURP promoted alternative splicing of spermidine/spermine N1-acetyltransferase 1 (SAT1) pre-mRNA by removal of intron 3, resulting in an increase in the stability of SAT1 mRNA and subsequent protein expression levels. Importantly, spliced SAT1 promoted the oncogenic properties of TNBC cells, and re-expression of SAT1 in U2SURP-depleted cells partially rescued the impaired malignant phenotypes of TNBC cells caused by U2SURP knockdown both in vitro and in mice. Collectively, these findings reveal previously unknown functional and mechanism roles of the MYC-U2SURP-SAT1 signaling axis in TNBC progression and highlight U2SURP as a potential therapy target for TNBC.

Spermidine/Spermine N1-Acetyltransferase 1 (SAT1)-A Potential Gene Target for Selective Sensitization of Glioblastoma Cells Using an Ionizable Lipid Nanoparticle to Deliver siRNA

Spermidine/spermine N1-acetyltransferase 1 (SAT1) responsible for cell polyamine catabolism is overexpressed in glioblastoma multiforme (GB). Its role in tumor survival and promoting resistance towards radiation therapy has made it an interesting target for therapy. In this study, we prepared a lipid nanoparticle-based siRNA delivery system (LNP-siSAT1) to selectively knockdown (KD) SAT1 enzyme in a human glioblastoma cell line. The LNP-siSAT1 containing ionizable DODAP lipid was prepared following a microfluidics mixing method and the resulting nanoparticles had a hydrodynamic size of around 80 nm and a neutral surface charge. The LNP-siSAT1 effectively knocked down the SAT1 expression in U251, LN229, and 42MGBA GB cells, and other brain-relevant endothelial (hCMEC/D3), astrocyte (HA) and macrophage (ANA-1) cells at the mRNA and protein levels. SAT1 KD in U251 cells resulted in a 40% loss in cell viability. Furthermore, SAT1 KD in U251, LN229 and 42MGBA cells sensitized them towards radiation and chemotherapy treatments. In contrast, despite similar SAT1 KD in other brain-relevant cells no significant effect on cytotoxic response, either alone or in combination, was observed. A major roadblock for brain therapeutics is their ability to cross the highly restrictive blood-brain barrier (BBB) presented by the brain microcapillary endothelial cells. Here, we used the BBB circumventing approach to enhance the delivery of LNP-siSAT1 across a BBB cell culture model. A cadherin binding peptide (ADTC5) was used to transiently open the BBB tight junctions to promote paracellular diffusion of LNP-siSAT1. These results suggest LNP-siSAT1 may provide a safe and effective method for reducing SAT1 and sensitizing GB cells to radiation and chemotherapeutic agents.

Ferroptosis and Its Multifaceted Role in Cancer: Mechanisms and Therapeutic Approach

Ferroptosis, a new type of non-apoptotic cell death modality, is different from other modes of cell death and has been primarily found in tumor cells. Previous studies have reported that ferroptosis can be triggered by specific modulators (e.g., drugs, nutrients, and iron chelators), leading to increased intracellular lipid reactive oxygen species (ROS) accumulation and iron overload. Recent reports have shown that ferroptosis at the cellular and organism levels can prevent an inflammatory storm and cancer development. Emerging evidence suggests potential mechanisms (e.g., system Xc-, glutathione peroxidase 4 (GPX4), lipid peroxidation, glutathione (GSH), and iron chelators) are involved in ferroptosis, which may mediate biological processes such as oxidative stress and iron overload to treat cancer. To date, there are at least three pathways that mediate ferroptosis in cancer cells: system Xc-/GSH/GPX4, FSP1/CoQ10/NAD(P)H, and ATG5/ATG7/NCOA4. Here, we summarize recent advances in the occurrence and development of ferroptosis in the context of cancer, the associations between ferroptosis and various modulators, and the potential mechanisms and therapeutic strategies targeting ferroptosis for the treatment of cancer.

The Association between Spermidine/Spermine N1-Acetyltransferase (SSAT) and Human Malignancies

Spermidine/spermine N¹-acetyltransferase (SSAT) functions as a critical enzyme in maintaining the homeostasis of polyamines, including spermine, spermidine, and putrescine, in mammalian cells. SSAT is a catalytic enzyme that indirectly regulates cellular physiologies and pathways through interaction with endogenous and exogenous polyamines. Normally, SSAT exhibits only at a low cellular level, but upon tumorigenesis, the expression, protein level, and activities of SSAT are altered. The alterations induce cellular damages, including oxidative stress, cell cycle arrest, DNA dynamics, and proliferation by influencing cellular mechanisms and signaling pathways. The expression of SSAT has been reported in various studies to be altered in different cancers, and it has been correlated with tumor development and progression. Tumor grades and stages are associated with the expression levels of SSAT. SSAT can be utilized as a target for substrate binding, and excreted metabolites may be used as a novel cancer biomarker. There is also potential for SSAT to be developed as a therapeutic target. Polyamine analogs could increase SSAT expression and increase the cytotoxicity of chemotherapy to tumor cells. Drugs targeting polyamines and SSAT expression have the potential to be developed into new cancer treatments in the future.

Abundant expression of ferroptosis-related SAT1 is related to unfavorable outcome and immune cell infiltration in low-grade glioma

Background

Low-grade glioma (LGG) is susceptible to ferroptosis, which is involved in TMZ resistance. Ferroptosis induction can enhance the sensitivity to TMZ and synergistically kill glioma cells. T cell-promoted tumor ferroptosis is a vital anti-tumor mechanism of immune checkpoint inhibitors. The SAT1 activation is closely related to ferroptosis upon ROS induction due to the upregulation of arachidonate 15-lipoxygenase (ALOX15) expression.

Methods

The expression of SAT1 in pan-cancer and corresponding normal tissue from the TCGA data portal was primarily explored. The landscape of SAT1 and immune cell infiltration and their corresponding gene marker sets in different tissues were further explored. Additionally, we evaluated the relationships between SAT1 and the clinicopathologic parameters of LGG, and the disease-specific survival (DSS), progression-free interval (PFI), and overall survival (OS) were also assessed using KM survival curves and multivariate analysis in LGG. Meanwhile, the Gene Set Enrichment Analysis (GSEA) was also implemented to determine the potential effect of the SAT1 gene in LGG. Furthermore, the predictive power of SAT1 was validated using an independent LGG cohort from the Chinese Glioma Genome Atlas (CGGA) data.

Results

In general, the expression of SAT1 is different between most tumors and their adjacent normal tissues. The results demonstrated that SAT1 expression is positively associated with TMB in LGG, BRCA, and THYM. The results displayed that the expression level of SAT1 is obviously correlated with the level of infiltrating macrophages and CD8 + T cells, and the levels of most immune gene sets were associated with the SAT1 expression in LGG. Interestingly, univariate and multivariate models significantly indicated that the OS and PFI of patients with LGG with high SAT1 levels were poorer than those with low SAT1 expression in the TCGA LGG cohort. GSEA showed that SAT1 was involved in immune regulation and multiple signaling pathways. Finally, our analysis demonstrated that SAT1 was closely associated with IDH mutation, 1p19q codeletion, chemoradiotherapy resistance and disease recurrence.

Conclusions

Abundant expression of SAT1 was related to poor disease prognosis and abundant immune cell infiltration in LGG.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09313-w.

Ferroptosis, as the most enriched programmed cell death process in glioma, induces immunosuppression and immunotherapy resistance

BACKGROUND

Immunosuppressive microenvironment is a major cause of immunotherapeutic resistance in glioma. In addition to secreting compounds, tumor cells under programmed cell death (PCD) processes release abundant mediators to modify the neighboring microenvironment. However, the complex relationship among PCD status, immunosuppressive microenvironment, and immunotherapy is still poorly understood.

METHODS

Four independent glioma cohorts comprising 1,750 patients were enrolled for analysis. The relationships among PCD status, microenvironment cellular components, and biological phenotypes were fully explored. Tissues from our hospital and experiments in vitro and in vivo were used to confirm the role of ferroptosis in glioma.

RESULTS

Analyses to determine enriched PCD processes showed that ferroptosis was the main type of PCD in glioma. Enriched ferroptosis correlated with progressive malignancy, poor outcomes, and aggravated immunosuppression in glioblastoma (GBM) patients. Enhanced ferroptosis was shown to induce activation and infiltration of immune cells but attenuated antitumor cytotoxic killing. Tumor-associated macrophages (TAMs) were found to participate in ferroptosis-mediated immunosuppression. Preclinically, ferroptosis inhibition combined with Programmed Cell Death 1 (PD-1) and Programmed Cell Death Ligand-1 (PD-L1) blockade generated a synergistic therapeutic outcome in GBM murine models.

CONCLUSIONS

This work provides a molecular, clinical, and biological landscape of ferroptosis, suggesting a role of ferroptosis in glioma malignancy and a novel synergic immunotherapeutic strategy that combines immune checkpoint blockade treatment with ferroptosis inhibition.

TRIM32 promotes radioresistance by disrupting TC45-STAT3 interaction in triple-negative breast cancer

Radioresistance is common in the treatment of triple-negative breast cancer (TNBC), but the molecular mechanisms involved remain unclear. Herein, we reveal that tripartite motif-containing protein 32 (TRIM32) is upregulated in TNBC and is negatively associated with survival of TNBC patients. Radiotherapy resulted in enhanced expression of TRIM32, whereas TRIM32 depletion reduced TNBC radioresistance in vitro and in vivo. Mechanistically, radiotherapy promoted the association between TRIM32 and nuclear STAT3, which suppressed TC45-induced dephosphorylation of STAT3, resulting in increased STAT3 transcriptional activation and TNBC radioresistance. Finally, we demonstrated that TRIM32 and STAT3 phosphorylation are co-expressed in TNBC tissues. Moreover, high expression of TRIM32 and STAT3 phosphorylation is positively linked to poor prognosis of TNBC patients. Our study demonstrates that TRIM32 is a novel target for predicting radioresistance in TNBC patients.

Therapeutic Effects of Dietary Soybean Genistein on Triple-Negative Breast Cancer via Regulation of Epigenetic Mechanisms

Consumption of dietary natural components such as genistein (GE) found in soy-rich sources is strongly associated with a lower risk of breast cancer. However, bioactive dietary component-based therapeutic strategies are largely understudied in breast cancer treatment. Our investigation sought to elucidate the potential mechanisms linking bioactive dietary GE to its breast cancer chemotherapeutic potential in a special subtype of aggressive breast cancer-triple-negative breast cancer (TNBC)-by utilizing two preclinical patient-derived xenograft (PDX) orthotopic mouse models: BCM-3204 and TM00091. Our study revealed that administration of GE resulted in a delay of tumor growth in both PDX models. With transcriptomics analyses in TNBC tumors isolated from BCM-3204 PDXs, we found that dietary soybean GE significantly influenced multiple tumor-regulated gene expressions. Further validation assessment of six candidate differentially expressed genes (DEGs)-Cd74, Lpl, Ifi44, Fzd9, Sat1 and Wwc1-demonstrated a similar trend at gene transcriptional and protein levels as observed in RNA-sequencing results. Mechanistically, GE treatment-induced Cd74 downregulation regulated the NF-κB/Bcl-xL/TAp63 signal pathway, which may contribute to soybean GE-mediated therapeutic effects on TNBC tumors. Additionally, our findings revealed that GE can modify expression levels of key epigenetic-associated genes such as DNA methyltransferases (Dnmt3b), ten-eleven translocation (Tet3) methylcytosine dioxygenases and histone deacetyltransferase (Hdac2), and their enzymatic activities as well as genomic DNA methylation and histone methylation (H3K9) levels. Collectively, our investigation shows high significance for potential development of a novel therapeutic approach by using bioactive soybean GE for TNBC patients who have few treatment options.

Adaptive translational pausing is a hallmark of the cellular response to severe environmental stress

To survive, mammalian cells must adapt to environmental challenges. While the cellular response to mild stress has been widely studied, how cells respond to severe stress remains unclear. We show here that under severe hyperosmotic stress, cells enter a transient hibernation-like state in anticipation of recovery. We demonstrate this adaptive pausing response (APR) is a coordinated cellular response that limits ATP supply and consumption through mitochondrial fragmentation and widespread pausing of mRNA translation. This pausing is accomplished by ribosome stalling at translation initiation codons, which keeps mRNAs poised to resume translation upon recovery. We further show that recovery from severe stress involves ISR (integrated stress response) signaling that permits cell cycle progression, resumption of growth, and reversal of mitochondria fragmentation. Our findings indicate that cells can respond to severe stress via a hibernation-like mechanism that preserves vital elements of cellular function under harsh environmental conditions.

A High-throughput Approach to Identify Effective Systemic Agents for the Treatment of Anaplastic Thyroid Carcinoma

BACKGROUND

Despite the use of aggressive multimodality treatment, most anaplastic thyroid carcinoma (ATC) patients die within a year of diagnosis. Although the combination of BRAF and MEK inhibitors has recently been approved for use in BRAF-mutated ATC, they remain effective in a minority of patients who are likely to develop drug resistance. There remains a critical clinical need for effective systemic agents for ATC with a reasonable toxicity profile to allow for rapid translational development.

MATERIAL AND METHODS

Twelve human thyroid cancer cell lines with comprehensive genomic characterization were used in a high-throughput screening (HTS) of 257 compounds to select agents with maximal growth inhibition. Cell proliferation, colony formation, orthotopic thyroid models, and patient-derived xenograft (PDX) models were used to validate the selected agents.

RESULTS

Seventeen compounds were effective, and docetaxel, LBH-589, and pralatrexate were selected for additional in vitro and in vivo analysis as they have been previously approved by the US Food and Drug Administration for other cancers. Significant tumor growth inhibition (TGI) was detected in all tested models treated with LBH-589; pralatrexate demonstrated significant TGI in the orthotopic papillary thyroid carcinoma model and 2 PDX models; and docetaxel demonstrated significant TGI only in the context of mutant TP53.

CONCLUSIONS

HTS identified classes of systemic agents that demonstrate preferential effectiveness against aggressive thyroid cancers, particularly those with mutant TP53. Preclinical validation in both orthotopic and PDX models, which are accurate in vivo models mimicking tumor microenvironment, may support initiation of early-phase clinical trials in non-BRAF mutated or refractory to BRAF/MEK inhibition ATC.

Identification of the Ferroptosis-Associated Gene Signature to Predict the Prognostic Status of Endometrial Carcinoma Patients

Endometrial carcinoma (EC) is one of the most common gynecological carcinomas. As previously described, ferroptosis was reported to exhibit a significant association with the development of malignant neoplasms. Nevertheless, there are few studies towards the association between the implication of ferroptosis-related genes (FRGs) and the prognostic status of patients with EC. Our study demonstrated that ferroptosis-related genes were evidently differently expressed in EC. Further analysis showed that SLC7A11, SAT1, CDKN1A, and TP5MC3 expression was linked to the low stage, grade of pTNM, and longer survival time. Bioinformatics analysis demonstrated that these ferroptosis-related regulators played a crucial role in EC by modulating multiple biological processes, such as cell cycle, citrate cycle (TCA cycle), metabolism-related pathways, ERK activation, p53 signaling pathway, cellular senescence, TAp63 pathway, and Notch signaling pathway. Of note, our results showed that ATP5MC3, CDKN1A, and SLC7A11 expression was dramatically positively related with the tumor mutational burden (TMB) score in EC. However, we did not observe a significant correlation between SAT1 and the TMB score in EC. These findings for the first time demonstrated that ferroptosis was displayed crucially in EC progression. We speculated that our findings offered novel targets and strategies for personalized treatment.

Circulating acetylated polyamines correlate with Covid-19 severity in cancer patients

Cancer patients are particularly susceptible to the development of severe Covid-19, prompting us to investigate the serum metabolome of 204 cancer patients enrolled in the ONCOVID trial. We previously described that the immunosuppressive tryptophan/kynurenine metabolite anthranilic acid correlates with poor prognosis in non-cancer patients. In cancer patients, we observed an elevation of anthranilic acid at baseline (without Covid-19 diagnosis) and no further increase with mild or severe Covid-19. We found that, in cancer patients, Covid-19 severity was associated with the depletion of two bacterial metabolites, indole-3-proprionate and 3-phenylproprionate, that both positively correlated with the levels of several inflammatory cytokines. Most importantly, we observed that the levels of acetylated polyamines (in particular N1-acetylspermidine, N1,N8-diacetylspermidine and N1,N12-diacetylspermine), alone or in aggregate, were elevated in severe Covid-19 cancer patients requiring hospitalization as compared to uninfected cancer patients or cancer patients with mild Covid-19. N1-acetylspermidine and N1,N8-diacetylspermidine were also increased in patients exhibiting prolonged viral shedding (>40 days). An abundant literature indicates that such acetylated polyamines increase in the serum from patients with cancer, cardiovascular disease or neurodegeneration, associated with poor prognosis. Our present work supports the contention that acetylated polyamines are associated with severe Covid-19, both in the general population and in patients with malignant disease. Severe Covid-19 is characterized by a specific metabolomic signature suggestive of the overactivation of spermine/spermidine N1-acetyl transferase-1 (SAT1), which catalyzes the first step of polyamine catabolism.

Combination LSD1 and HOTAIR-EZH2 inhibition disrupts cell cycle processes and induces apoptosis in glioblastoma cells

Glioblastoma (GBM) is the most common primary central nervous system tumor and has a poor prognosis, with a median survival time of only 14 months from diagnosis. Abnormally expressed long noncoding RNAs (lncRNAs) are important epigenetic regulators of chromatin modification and gene expression regulation in tumors, including GBM. We previously showed that the lncRNA HOTAIR is related to the cell cycle progression and can be used as an independent predictor in GBM. Lysine-specific demethylase 1 (LSD1), binding to 3' domain of HOTAIR, specifically removes mono- and di-methyl marks from H3 lysine 4 (H3K4) and plays key roles during carcinogenesis. In this study, we combined a HOTAIR-EZH2 disrupting agent and an LSD1 inhibitor, AC1Q3QWB (AQB) and GSK-LSD1, respectively, to block the two functional domains of HOTAIR and potentially provide therapeutic benefit in the treatment of GBM. Using an Agilent Human ceRNA Microarray, we identified tumor suppressor genes upregulated by AQB and GSK-LSD1, followed by Chromatin immunoprecipitation (ChIP) assays to explore the epigenetic mechanisms of genes activation. Microarray analysis showed that AQB and GSK-LSD1 regulate cell cycle processes and induces apoptosis in GBM cell lines. Furthermore, we found that the combination of AQB and GSK-LSD1 showed a powerful effect of inhibiting cell cycle processes by targeting CDKN1A, whereas apoptosis promoting effects of combination therapy were mediated by BBC3 in vitro. ChIP assays revealed that GSK-LSD1 and AQB regulate P21 and PUMA, respectively via upregulating H3K4me2 and downregulating H3K27me3. Combination therapy with AQB and GSK-LSD1 on tumor malignancy in vitro and GBM patient-derived xenograft (PDX) models shows enhanced anti-tumor efficacy and appears to be a promising new strategy for GBM treatment through its effects on epigenetic regulation.

Metabolic Alterations in Preneoplastic Development Revealed by Untargeted Metabolomic Analysis

Metabolic rewiring is a critical hallmark of tumorigenesis and is essential for the development of cancer. Although many key features of metabolic alteration that are crucial for tumor cell survival, proliferation and progression have been identified, these are obtained from studies with established tumors and cancer cell lines. However, information on the essential metabolic changes that occur during pre-neoplastic cell (PNC) development that enables its progression to full blown tumor is still lacking. Here, we present an untargeted metabolomics analysis of human oncogene HRASG12V induced PNC development, using a transgenic inducible zebrafish larval skin development model. By comparison with normal sibling controls, we identified six metabolic pathways that are significantly altered during PNC development in the skin. Amongst these altered pathways are pyrimidine, purine and amino acid metabolism that are common to the cancer metabolic changes that support rapid cell proliferation and growth. Our data also suggest alterations in post transcriptional modification of RNAs that might play a role in PNC development. Our study provides a proof of principle work flow for identifying metabolic alterations during PNC development driven by an oncogenic mutation. In the future, this approach could be combined with transcriptomic or proteomic approaches to establish the detailed interaction between signaling networks and cellular metabolic pathways that occur at the onset of tumor progression.

Adaptive Changes Allow Targeting of Ferroptosis for Glioma Treatment

Ferroptosis is a type of regulated cell death that plays an essential role in various brain diseases, including cranial trauma, neuronal diseases, and brain tumors. It has been reported that cancer cells rely on their robust antioxidant capacity to escape ferroptosis. Therefore, ferroptosis exploitation could be an effective strategy to prevent tumor proliferation and invasion. Glioma is a common malignant craniocerebral tumor exhibiting complicated drug resistance and survival mechanisms, resulting in a high mortality rate and short survival time. Recent studies have determined that metabolic alterations in glioma offer exploitable therapeutic targets. These metabolic alterations allow targeted therapy to achieve some initial efficacy but have failed to inhibit glioma growth, invasion, and drug resistance effectively. It has been proposed that the reason for the high malignancy and drug resistance observed with glioma is that these tumors can effectively evade ferroptosis. Ferroptosis-inducing drugs were found to exert a positive effect by targeting this particular characteristic of glioma cells. Moreover, gliomas develop enhanced drug resistance through anti-ferroptosis mechanisms. In this study, we provided an overview of the mechanisms by which glioma aggressiveness and drug resistance are mediated by the evasion of ferroptosis. This information might provide new targets for glioma therapy as well as new insights and ideas for future research.

Roles of nitric oxide and polyamines in brain tumor growth

Nitric oxide (NO) and polyamines: putrescine, spermidine and spermine, are key arginine metabolites in mammalian tissues that play critical roles i.a. in regulation of vascular tone (NO), and cell cycle regulation (polyamines). In the brain, both classes of molecules additionally have neuromodulatory and neuroprotective potential, and NO also a neurotoxic potential. Here we review evidence that brain tumors use the NO- and polyamine-synthesizing machineries to the benefit of their differentiation and growth from healthy glia and neurons. With a few exceptions, brain tumors show increased activities of one or all of the three arginine (Arg) to NO-converting nitric oxide synthase (NOS) isoforms (iNOS, eNOS, nNOS), but also elevated activities of polyamines-generating and modifying enzymes: arginase I/II, ornithine decarboxylase and spermidine/spermine N¹-acetyltransferase. The degree of stimulation of NO- and polyamine synthesis often correlates with brain tumor malignancy. Excess NO, but also spermine, spermidine and their N¹-acetylated forms, are tumor- and context-dependently involved in angiogenesis, tumor initiation and growth, and resistance to chemo- or radiotherapy. Hypothetically, increased demand for NO and/or polyamines is likely to contribute to Arg auxotrophy of malignant brain tumors, albeit the causal nexus awaits experimental verification.

Polyamines drive myeloid cell survival by buffering intracellular pH to promote immunosuppression in glioblastoma

Glioblastoma is characterized by the robust infiltration of immunosuppressive tumor-associated myeloid cells (TAMCs). It is not fully understood how TAMCs survive in the acidic tumor microenvironment to cause immunosuppression in glioblastoma. Metabolic and RNA-seq analysis of TAMCs revealed that the arginine-ornithine-polyamine axis is up-regulated in glioblastoma TAMCs but not in tumor-infiltrating CD8+ T cells. Active de novo synthesis of highly basic polyamines within TAMCs efficiently buffered low intracellular pH to support the survival of these immunosuppressive cells in the harsh acidic environment of solid tumors. Administration of difluoromethylornithine (DFMO), a clinically approved inhibitor of polyamine generation, enhanced animal survival in immunocompetent mice by causing a tumor-specific reduction of polyamines and decreased intracellular pH in TAMCs. DFMO combination with immunotherapy or radiotherapy further enhanced animal survival. These findings indicate that polyamines are used by glioblastoma TAMCs to maintain normal intracellular pH and cell survival and thus promote immunosuppression during tumor evolution.

Ferroptosis-Related Gene Signature Predicts Glioma Cell Death and Glioma Patient Progression

Glioma is a fatal brain tumor characterized by rapid proliferation and treatment resistance. Ferroptosis is a newly discovered programmed cell death and plays a crucial role in the occurrence and progression of tumors. In this study, we identified ferroptosis specific markers to reveal the relationship between ferroptosis-related genes and glioma by analyzing whole transcriptome data from Chinese Glioma Genome Atlas, The Cancer Genome Atlas dataset, GSE16011 dataset, and the Repository of Molecular Brain Neoplasia Data dataset. Nineteen ferroptosis-related genes with clinical and pathological features of glioma were identified as highly correlated. Functional assays in glioma cell lines indicated the association of ferroptosis with temozolomide resistance, autophagy, and glioma cell migration. Therefore, the identified ferroptosis-related genes were significantly correlated with glioma progression.

Effects of Genetic Variation on Urinary Small Molecule Signatures of Mice after Exposure to Ionizing Radiation: A Study of p53 Deficiency

Due to risks from potential exposures to ionizing radiation (IR), improved radiological countermeasures are required, as well as rapid high-throughput biodosimetry. Genotypic variation in the general population contributes to differences in radiosensitivity that may affect biodosimetry accuracy. Previous studies utilized radiosensitive mutant mouse models (Parp1^−/− and Atm^−/−) to determine the effects of genotypic deficiency on radiation signatures. Here, we extend this approach by examining changes in the urinary metabolome in a hematopoietic (HP) resistant mouse model (p53^−/−) after IR exposure. As p53 is a primary regulator in radiation response and apoptosis, limited hematopoietic stem cell apoptosis leads to reduced mortality at doses of ~8–10 Gy but increased mortality at higher doses (>15 Gy) due to mitotic catastrophe in gastrointestinal (GI) crypt cells. Urine was collected from mice (wild-type (WT), p53^+/−, and p53^−/−) pre-irradiation and at 4 and 24 h after total body irradiation (TBI) (WT: 8 and 10 Gy; p53^−/−: 10 Gy) for metabolic phenotyping using an ultra-performance liquid chromatography mass spectrometry (UPLC-MS) platform. Minimal differences were detected between unirradiated WT, p53^+/−, and p53^−/− mice. While similar perturbations were observed for metabolites involved in tryptophan, vitamin B6, and histamine pathways, glycine conjugation, and redox metabolism for WT and p53^−/− mice after TBI, an overall dampened response was observed in p53-deficient mice. Despite comparable metabolite patterns between genotypes, differentiation was achieved through receiver operating characteristic curve analysis with high specificity and sensitivity for carnitine, N1-acetylspermidine, and creatine. These studies highlight that both attenuated and dampened metabolic responses due to genetic variability in the general population need to be addressed in biodosimetry frameworks.

Alternative polyadenylation drives oncogenic gene expression in pancreatic ductal adenocarcinoma

Alternative polyadenylation (APA) is a gene regulatory process that dictates mRNA 3'-UTR length, resulting in changes in mRNA stability and localization. APA is frequently disrupted in cancer and promotes tumorigenesis through altered expression of oncogenes and tumor suppressors. Pan-cancer analyses have revealed common APA events across the tumor landscape; however, little is known about tumor type-specific alterations that may uncover novel events and vulnerabilities. Here, we integrate RNA-sequencing data from the Genotype-Tissue Expression (GTEx) project and The Cancer Genome Atlas (TCGA) to comprehensively analyze APA events in 148 pancreatic ductal adenocarcinomas (PDACs). We report widespread, recurrent, and functionally relevant 3'-UTR alterations associated with gene expression changes of known and newly identified PDAC growth-promoting genes and experimentally validate the effects of these APA events on protein expression. We find enrichment for APA events in genes associated with known PDAC pathways, loss of tumor-suppressive miRNA binding sites, and increased heterogeneity in 3'-UTR forms of metabolic genes. Survival analyses reveal a subset of 3'-UTR alterations that independently characterize a poor prognostic cohort among PDAC patients. Finally, we identify and validate the casein kinase CSNK1A1 (also known as CK1alpha or CK1a) as an APA-regulated therapeutic target in PDAC. Knockdown or pharmacological inhibition of CSNK1A1 attenuates PDAC cell proliferation and clonogenic growth. Our single-cancer analysis reveals APA as an underappreciated driver of protumorigenic gene expression in PDAC via the loss of miRNA regulation.

Population and single‑cell transcriptome analyses reveal diverse transcriptional changes associated with radioresistance in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a tumor composed of heterogeneous cells that easily become radioresistant, which leads to tumor recurrence. The most commonly used treatment for ESCC is fractionated irradiation (FIR) therapy that utilizes ionizing radiation to directly induce cytotoxic cell death. However, this treatment may not be able to eliminate all cancer cells due to high adaptive evolution. To determine whether the transcriptome dynamics during ESCC recurrence formation are associated with FIR response, an in vitro cell culture model for ESCC radioresistance that mimics the common radiotherapy process in patients with ESCC was established in the present study. High‑throughput sequencing analysis of in vitro cultured ESCC cells was performed using different cumulative irradiation doses, as well as tumor samples from FIR‑treated patients with ESCC before and after the development of radioresistance. Radioresistance‑associated genes and signaling pathways that were aberrantly expressed in radioresistant ESCC cells were identified, including autophagy‑related 9B (regulation of autophagy), DNA damage‑inducible transcript 4, myoglobin and plasminogen activator tissue type, which are associated with response to hypoxia, Bcl2‑binding component 3, tumor protein P63 and interferon γ‑inducible protein 16, which are associated with DNA damage response. The heterogeneity and dynamic gene expression of ESCC cells during acquired radioresistance were further studied in primary (41 single cells), 12 Gy FIR‑treated (87 single cells) and 30 Gy FIR‑treated (89 single cells) cancer cells using a single‑cell RNA sequencing approach. The results of the present study comprehensively characterized the transcriptome dynamics during acquired radioresistance in an in vitro model of ESCC and patient tumor samples at the population and single cell level. Single‑cell RNA sequencing revealed the heterogeneity of irradiated ESCC cells and an increase in the radioresistant ESCC cell subpopulation during acquired radioresistance. Overall, these results are of potential clinical relevance as they identify a number of signaling molecules associated with radioresistance, as well as opportunities for the development of novel therapeutic options for the treatment of ESCC.

Spermidine/spermine N1-acetyltransferase 1 is a gene-specific transcriptional regulator that drives brain tumor aggressiveness

Spermidine/spermine N1-acetyltransferase 1 (SAT1), the rate limiting enzyme in polyamine catabolism, has broad regulatory roles due to near ubiquitous polyamine binding. We describe a novel function of SAT1 as a gene-specific transcriptional regulator through local polyamine acetylation. SAT1 expression is elevated in aggressive brain tumors and promotes resistance to radiotherapy. Expression profiling in glioma cells identified SAT1 target genes that distinguish high and low grade tumors, in support of the prognostic utility of SAT1 expression. We further discovered mechanisms of SAT1-driven tumor aggressiveness through promotion of expression of both DNA damage response pathways as well as cell cycle regulatory genes. Mechanistically, SAT1 associates specifically with the promoter of the MELK gene, which functionally controls other SAT1 targets, and leads biologically to maintenance of neurosphere stemness in conjunction with FOXM1 and EZH2. CRISPR knockin mutants demonstrate the essentiality of the polyamine acetyl transferase activity of SAT1 for its function as a transcriptional regulator. Together, the data demonstrate that gene-specific polyamine removal is a major transcriptional regulatory mechanism active in high grade gliomas that drives poor outcomes.

The Ig superfamily protein PTGFRN coordinates survival signaling in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most malignant primary brain tumor with a median survival of approximately 14 months. Despite aggressive treatment of surgical resection, chemotherapy and radiation therapy, only 3-5% of GBM patients survive more than 3 years. Contributing to this poor therapeutic response, it is believed that GBM contains both intrinsic and acquired mechanisms of resistance, including resistance to radiation therapy. In order to define novel mediators of radiation resistance, we conducted a functional knockdown screen, and identified the immunoglobulin superfamily protein, PTGFRN. In GBM, PTGFRN is found to be overexpressed and to correlate with poor survival. Reducing PTGFRN expression radiosensitizes GBM cells and potently decreases the rate of cell proliferation and tumor growth. Further, PTGFRN inhibition results in significant reduction of PI3K p110β and phosphorylated AKT, due to instability of p110β. Additionally, PTGFRN inhibition decreases nuclear p110β leading to decreased DNA damage sensing and DNA damage repair. Therefore overexpression of PTGFRN in glioblastoma promotes AKT-driven survival signaling and tumor growth, as well as increased DNA repair signaling. These findings suggest PTGFRN is a potential signaling hub for aggressiveness in GBM.

Lipolytic inhibitor G0S2 modulates glioma stem-like cell radiation response

BACKGROUND

Ionizing radiation (IR) therapy is the standard first-line treatment for newly diagnosed patients with glioblastoma (GBM), the most common and malignant primary brain tumor. However, the effects of IR are limited due to the aberrant radioresistance of GBM.

METHODS

Transcriptome analysis was performed using RNA-seq in radioresistant patient-derived glioma stem-like cells (GSCs). Survival of glioma patient and mice bearing-brain tumors was analyzed by Kaplan-Meier survival analysis. Lipid droplet and γ-H2AX foci-positive cells were evaluated using immunofluorescence staining.

RESULTS

Lipolytic inhibitor G0/G1 switch gene 2 (G0S2) is upregulated in radioresistant GSCs and elevated in clinical GBM. GBM patients with high G0S2 expression had significantly shorter overall survival compared with those with low expression of G0S2. Using genetic approaches targeting G0S2 in glioma cells and GSCs, we found that knockdown of G0S2 promoted lipid droplet turnover, inhibited GSC radioresistance, and extended survival of xenograft tumor mice with or without IR. In contrast, overexpression of G0S2 promoted glioma cell radiation resistance. Mechanistically, high expression of G0S2 reduced lipid droplet turnover and thereby attenuated E3 ligase RNF168-mediated 53BP1 ubiquitination through activated the mechanistic target of rapamycin (mTOR)-ribosomal S6 kinase (S6K) signaling and increased 53BP1 protein stability in response to IR, leading to enhanced DNA repair and glioma radioresistance.

CONCLUSIONS

Our findings uncover a new function for lipolytic inhibitor G0S2 as an important regulator for GSC radioresistance, suggesting G0S2 as a potential therapeutic target for treating gliomas.

Epigenetic modulation of metabolism in glioblastoma

Epigenetic and metabolic alterations incancer cells are highly associated. Glioblastoma multiforme (GBM) is a complicated pathological process with dysregulated methylation and histone modifications. Metabolic modulation of epigenetics in gliomas was previously summarized. However, epigenetic modulation is also important in metabolic decision. Recently, there has been a tremendous increase in understanding of DNA methylation, chromatin modulation, and non-coding RNAs in the regulation of cell metabolism, especially glycolytic metabolism in GBM. In this review, we summarize DNA methylation, histone alteration, and non-coding RNA mediated epigenetic modulation of metabolism in GBM and discuss the future research directions in this area and its applications in GBM treatment.

Characterization of the SSAT1 gene and its expression profiling in various tissues and follicles in geese

Spermidine/spermine N1-acetyltransferase (SSAT ) is a catabolic regulator of polyamines, ubiquitous molecules essential for cell proliferation and differentiation. In this study, the molecular characterization of the SSAT1 gene of the Sichuan white goose was analyzed, as well as its expression profiles in various follicles and tissues. The open reading frame of the SSAT1 cDNA (GenBank No. KM925008) is 516 bp in length and encodes a 171-amino acid protein with a putative molecular weight of 20 kDa. The predicted SSAT1 protein is highly conserved with those of other species, especially Gallus gallus. SSAT1 mRNA was ubiquitously expressed in all the examined tissues. The highest level of SSAT1 mRNA expression was found in the pineal gland (P<0.05), and was 12-fold greater than in the heart. The level of SSAT1 mRNA expression was relatively lower in preovulatory follicles, while it was higher in postovulatory follicles (POFs), particularly in POF1. Furthermore, as postovulatory follicles degenerated, SSAT1 expression gradually decreased. Our findings suggest that SSAT1 might play important roles in mediating the physiological function of the pineal gland and regulating the regression of POFs.

Oil for the cancer engine: The cross-talk between oncogenic signaling and polyamine metabolism

The study of metabolism has provided remarkable information about the biological basis and therapeutic weaknesses of cancer cells. Classic biochemistry established the importance of metabolic alterations in tumor biology and revealed the importance of various metabolite families to the tumorigenic process. We have evidence of the central role of polyamines, small polycatonic metabolites, in cell proliferation and cancer growth from these studies. However, how cancer cells activate this metabolic pathway and the molecular cues behind the oncogenic action of polyamines has remained largely obscure. In contrast to the view of metabolites as fuel (anabolic intermediates) for cancer cells, polyamines are better defined as the oil that lubricates the cancer engine because they affect the activity of biological processes. Modern research has brought back to the limelight this metabolic pathway, providing a strong link between genetic, metabolic, and signaling events in cancer. In this review, we enumerate and discuss current views of the regulation and activity of polyamine metabolism in tumor cell biology.

Arginine auxotrophic gene signature in paediatric sarcomas and brain tumours provides a viable target for arginine depletion therapies

Paediatric sarcomas and brain tumours, remain cancers of significant unmet need, with a poor prognosis for patients with high risk disease or those who relapse, and significant morbidities from treatment for those that survive using standard treatment approaches. Novel treatment strategies, based on the underlying tumour biology, are needed to improve outcomes. Arginine is a semi-essential amino acid that is imported from the extracellular microenvironment or recycled from intracellular precursors through the combined expression of the enzymes ornithine transcarbamylase (OTC), argininosuccinate synthase (ASS) and argininosuccinate lyase (ASL) enzymes. The failure to express at least one of these recycling enzymes makes cells reliant on extracellular arginine - a state known as arginine auxotrophism. Here we show in large in silico patient cohorts that paediatric sarcomas and brain tumours express predominately the arginine transporter SLC7A1 and the arginine metabolising enzyme Arginase 2 (ARG2), but have low-absent expression of OTC. The arginine metabolic pathway correlated with the expression of genes associated with tumour pathogenesis, and overall survival in paediatric sarcomas. This gene signature of arginine auxotrophism indicates paediatric sarcomas and brain tumours are a viable target for therapeutic arginase drugs under current clinical trial development.

Cholecystokinin attenuates radiation-induced lung cancer cell apoptosis by modulating p53 gene transcription

The deregulation of p53 in cancer cells is one of the important factors by which cancer cells escape from the immune surveillance. Cholecystokinin (CCK) has strong bioactivity in the regulation of a number of cell activities. This study tests a hypothesis that CCK interferes with p53 expression to affect the apoptotic process in lung cancer (tumor) cells. In this study, tumor-bearing mice and A549 cells (a tumor cell line) were irradiated. The expression of CCK and p53 in tumor cells was assessed with RT-qPCR and Western blotting. The binding of p300 to the promoter of p53 was evaluated by chromatin immunoprecipitation. We observed that, with a given amount and within a given period, small doses/more sessions of irradiation markedly increased the levels of CCK in the sera and tumor cells, which were positively correlated with the tumor growth in mice and negatively correlated with tumor cell apoptosis. CCK increased the levels of histone acetyltransferase p300 and repressed the levels of nuclear factor-kB at the p53 promoter locus in tumor cells, which suppressed the expression of p53. In conclusion, CCK plays an important role in attenuating the radiation-induced lung cancer cell apoptosis. CCK may be a novel therapeutic target in the treatment of lung cancers.

Cancer-secreted AGR2 induces programmed cell death in normal cells

Anterior Gradient 2 (AGR2) is a protein expressed in many solid tumor types including prostate, pancreatic, breast and lung. AGR2 functions as a protein disulfide isomerase in the endoplasmic reticulum. However, AGR2 is secreted by cancer cells that overexpress this molecule. Secretion of AGR2 was also found in salamander limb regeneration. Due to its ubiquity, tumor secretion of AGR2 must serve an important role in cancer, yet its molecular function is largely unknown. This study examined the effect of cancer-secreted AGR2 on normal cells. Prostate stromal cells were cultured, and tissue digestion media containing AGR2 prepared from prostate primary cancer 10-076 CP and adenocarcinoma LuCaP 70CR xenograft were added. The control were tissue digestion media containing no AGR2 prepared from benign prostate 10-076 NP and small cell carcinoma LuCaP 145.1 xenograft. In the presence of tumor-secreted AGR2, the stromal cells were found to undergo programmed cell death (PCD) characterized by formation of cellular blebs, cell shrinkage, and DNA fragmentation as seen when the stromal cells were UV irradiated or treated by a pro-apoptotic drug. PCD could be prevented with the addition of the monoclonal AGR2-neutralizing antibody P3A5. DNA microarray analysis of LuCaP 70CR media-treated vs. LuCaP 145.1 media-treated cells showed downregulation of the gene SAT1 as a major change in cells exposed to AGR2. RT-PCR analysis confirmed the array result. SAT1 encodes spermidine/spermine N1-acetyltransferase, which maintains intracellular polyamine levels. Abnormal polyamine metabolism as a result of altered SAT1 activity has an adverse effect on cells through the induction of PCD.

SAT1 and glioblastoma multiforme: Disarming the resistance

Glioblastoma multiforme is the most common and most detrimental form of brain tumor, with a current survival time of as little as 14 months. We have recently identified a novel mechanism of therapeutic resistance based on overexpression of the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase, which promotes DNA repair via chromatin modification.

Tumour-specific metabolic adaptation to acidosis is coupled to epigenetic stability in osteosarcoma cells

The glycolytic-based metabolism of cancers promotes an acidic microenvironment that is responsible for increased aggressiveness. However, the effects of acidosis on tumour metabolism have been almost unexplored. By using capillary electrophoresis with time-of-flight mass spectrometry, we observed a significant metabolic difference associated with glycolysis repression (dihydroxyacetone phosphate), increase of amino acid catabolism (phosphocreatine and glutamate) and urea cycle enhancement (arginino succinic acid) in osteosarcoma (OS) cells compared with normal fibroblasts. Noteworthy, metabolites associated with chromatin modification, like UDP-glucose and N(8)-acetylspermidine, decreased more in OS cells than in fibroblasts. COBRA assay and acetyl-H3 immunoblotting indicated an epigenetic stability in OS cells than in normal cells, and OS cells were more sensitive to an HDAC inhibitor under acidosis than under neutral pH. Since our data suggest that acidosis promotes a metabolic reprogramming that can contribute to the epigenetic maintenance under acidosis only in tumour cells, the acidic microenvironment should be considered for future therapies.

Multifunctional pH-Sensitive Amino Lipids for siRNA Delivery

RNA interference (RNAi) represents a powerful modality for human disease therapy that can regulate gene expression signature using small interfering RNA (siRNA). Successful delivery of siRNA into the cytoplasm of target cells is imperative for efficient RNAi and also constitutes the primary stumbling block in the clinical applicability of RNAi. Significant progress has been made in the development of lipid-based siRNA delivery systems, which have practical advantages like simple chemistry and easy formulation of nanoparticles with siRNA. This review discusses the recent development of pH-sensitive amino lipids, with particular focus on multifunctional pH-sensitive amino lipids for siRNA delivery. The key components of these multifunctional lipids include a protonatable amino head group, distal lipid tails, and two cross-linkable thiol groups, which together facilitate the facile formation of stable siRNA-nanoparticles, easy surface modification for target-specific delivery, endosomal escape in response to the pH decrease during subcellular trafficking, and reductive dissociation of the siRNA-nanoparticles for cytoplasmic release of free siRNA. By virtue of these properties, multifunctional pH-sensitive lipids can mediate efficient cytosolic siRNA delivery and gene silencing. Targeted siRNA nanoparticles can be readily formulated with these lipids, without the need for other helper lipids, to promote systemic delivery of therapeutic siRNAs. Such targeted siRNA nanoparticles have been shown to effectively regulate the expression of cancer-related genes, resulting in significant efficacy in the treatment of aggressive tumors, including metastatic triple negative breast cancer. These multifunctional pH-sensitive lipids constitute a promising platform for the systemic and targeted delivery of therapeutic siRNA for the treatment of human diseases. This review summarizes the structure-property relationship of the multifunctional pH-sensitive lipids and their efficacy in in vitro and in vivo siRNA delivery and gene silencing.

Inhibition of tribbles protein-1 attenuates radioresistance in human glioma cells

Radiotherapy is one of the remedies in the treatment of glioma. The radioresistance is a major drawback, of which the mechanism is unclear. Tribble protein and histone deacetylase are involved in the cancer pathogenesis. This study aims to test a hypothesis that the histone deacetylase inhibitors attenuate the radioresistance in human glioma cells. In this study, human glioma cells were cultured. The cells were treated with irradiation with or without a histone deacetylase inhibitor, butyrate. Apoptosis of the glioma cells was assessed by flow cytometry. The results showed that human glioma cells expressed a low level of Trib1, which was significantly up regulated by exposure to small doses (2 Gy/day for 4 days) of irradiation. Trib1-deficient glioma cells showed an enhanced response to irradiation-induced apoptosis. Exposure to small doses of irradiation, Trib1 formed a complex with pHDAC1 (phosphor histone deacetylase-1) to inhibit p53 expression in glioma cells. The presence of HDAC1 inhibitor, butyrate or parthenolide, significantly enforced irradiation-induced glioma cell apoptosis. In conclusion, the Trib1 plays a critical role in the development of radioresistance of glioma cells. The data suggest that inhibition of Trib1 or HDAC1 has the potential to prevent or attenuate the radioresistance.