Ptpmt1 induced by HIF-2α regulates the proliferation and glucose metabolism in erythroleukemia cells

The role of glycometabolic plasticity in cancer

Dysregulated glycometabolism represented by the Warburg effect is well recognized as a hallmark of cancer that can be driven by oncogenes (e.g., c-Myc, K-ras, and BRAF) and contribute to cellular malignant transformation. The Warburg effect reveals the different glycometabolic patterns of cancer cells, but this unique glycometabolic pattern has the characteristic of plasticity rather than changeless which can vary with different internal or external stimuli during evolution. Glycometabolic plasticity enables cancer cells to modulate glycometabolism to support progression, metastasis, treatment resistance and recurrence. In this review, we report the characteristics of glycometabolic plasticity during different stages of cancer evolution, providing insight into the molecular mechanisms of glycometabolic plasticity in cancer. In addition, we discussed the challenges and future research directions of glycometabolism research in cancer.

Splicing factor SRSF1 promotes breast cancer progression via oncogenic splice switching of PTPMT1

Background

Intensive evidence has highlighted the effect of aberrant alternative splicing (AS) events on cancer progression when triggered by dysregulation of the SR protein family. Nonetheless, the underlying mechanism in breast cancer (BRCA) remains elusive. Here we sought to explore the molecular function of SRSF1 and identify the key AS events regulated by SRSF1 in BRCA.

Methods

We conducted a comprehensive analysis of the expression and clinical correlation of SRSF1 in BRCA based on the TCGA dataset, Metabric database and clinical tissue samples. Functional analysis of SRSF1 in BRCA was conducted in vitro and in vivo. SRSF1-mediated AS events and their binding motifs were identified by RNA-seq, RNA immunoprecipitation-PCR (RIP-PCR) and in vivo crosslinking followed by immunoprecipitation (CLIP), which was further validated by the minigene reporter assay. PTPMT1 exon 3 (E3) AS was identified to partially mediate the oncogenic role of SRSF1 by the P-AKT/C-MYC axis. Finally, the expression and clinical significance of these AS events were validated in clinical samples and using the TCGA database.

Results

SRSF1 expression was consistently upregulated in BRCA samples, positively associated with tumor grade and the Ki-67 index, and correlated with poor prognosis in a hormone receptor-positive (HR+) cohort, which facilitated proliferation, cell migration and inhibited apoptosis in vitro and in vivo. We identified SRSF1-mediated AS events and discovered the SRSF1 binding motif in the regulation of splice switching of PTPMT1. Furthermore, PTPMT1 splice switching was regulated by SRSF1 by binding directly to its motif in E3 which partially mediated the oncogenic role of SRSF1 by the AKT/C-MYC axis. Additionally, PTPMT1 splice switching was validated in tissue samples of BRCA patients and using the TCGA database. The high-risk group, identified by AS of PTPMT1 and expression of SRSF1, possessed poorer prognosis in the stage I/II TCGA BRCA cohort.

Conclusions

SRSF1 exerts oncogenic roles in BRCA partially by regulating the AS of PTPMT1, which could be a therapeutic target candidate in BRCA and a prognostic factor in HR+ BRCA patient.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01978-8.

Alleles in metabolic and oxygen-sensing genes are associated with antagonistic pleiotropic effects on life history traits and population fitness in an ecological model insect

Genes with opposing effects on fitness at different life stages are the mechanistic basis for evolutionary theories of aging and life history. Examples come from studies of mutations in model organisms, but there is little knowledge of genetic bases of life history tradeoffs in natural populations. Here, we test the hypothesis that alleles affecting oxygen sensing in Glanville fritillary butterflies have opposing effects on larval versus adult fitness-related traits. Intermediate-frequency alleles in Succinate dehydrogenase d, and to a lesser extent Hypoxia inducible factor 1α, are associated in larvae with variation in metabolic rate and activation of the hypoxia inducible factor (HIF) pathway, which affects tracheal development and delivery of oxygen to adult flight muscles. A dominant Sdhd allele is likely to cause antagonistic pleiotropy for fitness through its opposing effects on larval metabolic and growth rate versus adult flight and dispersal, and may have additional effects arising from sensitivity to low-iron host plants. Prior results in Glanville fritillaries indicate that fitness of alleles in Sdhd and another antagonistically pleiotropic metabolic gene, Phosphoglucose isomerase, depend strongly on the size and distribution of host plant patches. Hence, these intermediate-frequency alleles are involved in ecoevolutionary dynamics involving life history tradeoffs.

Dietary Dityrosine Induces Mitochondrial Dysfunction by Diminished Thyroid Hormone Function in Mouse Myocardia

Oxidized tyrosine products (OTP) have been detected in commercial foods with high protein content, such as meat and milk products. OTP intake induces tissue oxidative stress and affects the normal activity of the hypothalamic-pituitary-thyroid axis (HPT). This study aims to investigate the effects of OTP and their main product, dityrosine (Dityr), on mouse myocardial function and myocardial energy metabolism. Mice received daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), Dityr (420 μg/kg body weight), or OTP (1909 μg/kg body weight) for 35 days. Additionally, H9c2 cells were incubated with various concentrations of Dityr for 72 h. We found that OTP and pure Dityr induced oxidative stress in growing mice and in H9c2 cells, resulting in a redox state imbalance, myocardial injury, mitochondrial dysfunction, and energy metabolism disorder. Dityr interferes with T3 regulation of the myocardium via the PI3K/AKT/GSK3β pathway, leading to myocardial mitochondrial damage and energy metabolism disorders. Food-borne OTP, especially Dityr, can disrupt thyroid hormone function in mouse myocardia leading to mitochondrial dysfunction, energy metabolism disorder, and oxidative stress.

CircHIPK3 Promotes Metastasis of Gastric Cancer via miR-653-5p/miR-338-3p-NRP1 Axis Under a Long-Term Hypoxic Microenvironment

As a vital feature of the microenvironment, hypoxia, especially long-term hypoxia, is known to promote metastasis and lead to poor prognosis in solid tumors. Circular RNAs (circRNAs) participate in important processes of cell proliferation and metastasis in cancers. However, the contribution of circRNAs to metastasis under long-term hypoxia is obscure. In this study, we aim to explore specific functions of circHIPK3 in long-term hypoxia-promoting metastasis of gastric cancer (GC). The hypoxic resistant gastric cancer (HRGC) cell lines we established previously, which were tolerant to 2% O₂ conditions, were used as the long-term hypoxia model. We found that circHIPK3 was upregulated by HIF-2α in HRGC cells, and circHIPK3 facilitated the migration and invasion ability of HRGC cells. Further investigation proved that circHIPK3 promoted metastasis of HRGC cells directly by interacting with miR-653-5p and miR-338-3p to relieve the suppression of neuropilin 1 (NRP1), resulting in the activation of downstream ERK and AKT pathways. Our study identified oncogene functions of circHIPK3 under a long-term hypoxic microenvironment and the possibility of using circHIPK3 as a potential biomarker of long-term hypoxia in GC. In conclusion, circHIPK3 could promote GC metastasis via the miR-653-5p/miR-338-3p-NRP1 axis under a long-term hypoxic microenvironment.

Phosphoproteomic analysis of longissimus lumborum of different altitude yaks

Yaks in high altitude regions display good adaptability to hypoxic environment. However, the mechanism involved in regulating muscle protein expression in hypoxic environment is not completely clear yet. To explore the mechanisms modulating postmortem alterations, quantitative phosphoproteomic analysis was performed on muscles of yaks raised at two different altitudes. The results indicated that 475 differentially expressed proteins (DEPS) were identified in high-altitude yaks, among which, 439 DEPs were up-regulated and 36 DEPs were down-regulated. Of these, 26 phosphoproteins clustered into energy metabolism and hypoxic adaption were selected after bioinformatics analysis. In addition, some glycolytic enzymes were detected to be differentially phosphorylated. The difference in protein phosphorylation levels between the two groups may be the key factor involved in the regulation of muscle hypoxic adaption. The present results could provide proteomic insights into changes occurring in yak muscles at different altitudes and may be a valuable resource for future investigations.

Adaptation to HIF1α Deletion in Hypoxic Cancer Cells by Upregulation of GLUT14 and Creatine Metabolism

Hypoxia-inducible factor 1α is a key regulator of the hypoxia response in normal and cancer tissues. It is well recognized to regulate glycolysis and is a target for therapy. However, how tumor cells adapt to grow in the absence of HIF1α is poorly understood and an important concept to understand for developing targeted therapies is the flexibility of the metabolic response to hypoxia via alternative pathways. We analyzed pathways that allow cells to survive hypoxic stress in the absence of HIF1α, using the HCT116 colon cancer cell line with deleted HIF1α versus control. Spheroids were used to provide a 3D model of metabolic gradients. We conducted a metabolomic, transcriptomic, and proteomic analysis and integrated the results. These showed surprisingly that in three-dimensional growth, a key regulatory step of glycolysis is Aldolase A rather than phosphofructokinase. Furthermore, glucose uptake could be maintained in hypoxia through upregulation of GLUT14, not previously recognized in this role. Finally, there was a marked adaptation and change of phosphocreatine energy pathways, which made the cells susceptible to inhibition of creatine metabolism in hypoxic conditions. Overall, our studies show a complex adaptation to hypoxia that can bypass HIF1α, but it is targetable and it provides new insight into the key metabolic pathways involved in cancer growth. IMPLICATIONS: Under hypoxia and HIF1 blockade, cancer cells adapt their energy metabolism via upregulation of the GLUT14 glucose transporter and creatine metabolism providing new avenues for drug targeting.

Therapeutic Potential of Novel Twin Compounds Containing Tetramethylpyrazine and Carnitine Substructures in Experimental Ischemic Stroke

Although studies have seen dramatic advances in the understanding of the pathogenesis of stroke such as oxidative stress, inflammation, excitotoxicity, calcium overload and apoptosis, the delivery of stroke therapies is still a great challenge. In this study, we designed and synthesized a series of novel twin compounds containing tetramethylpyrazine and carnitine substructures and explored their therapeutic potential and mechanism in stroke-related neuronal injury. We first screened the neuroprotective effects of candidate compounds and found that among the tested compounds, LR134 and LR143 exhibited significant neuroprotection as evidenced by reducing cerebral infarct and edema, improving neurological function as well as blood-brain barrier integrity in rats after cerebral ischemia/reperfusion injury. We further demonstrated that the neuroprotective effects of compounds LR134 and LR143 were associated with the reduced inflammatory responses and NADPH oxidase- (NOX2-) mediated oxidative stress and the protection of mitochondria accompanied by the improvement of energy supply. In summary, this study provides direct evidence showing that the novel twin compounds containing tetramethylpyrazine and carnitine substructures have neuroprotective effects with multiple therapeutic targets, suggesting that modulation of these chemical structures may be an innovative therapeutic strategy for treating patients with stroke.

Critical Roles of Dual-Specificity Phosphatases in Neuronal Proteostasis and Neurological Diseases

Protein homeostasis or proteostasis is a fundamental cellular property that encompasses the dynamic balancing of processes in the proteostasis network (PN). Such processes include protein synthesis, folding, and degradation in both non-stressed and stressful conditions. The role of the PN in neurodegenerative disease is well-documented, where it is known to respond to changes in protein folding states or toxic gain-of-function protein aggregation. Dual-specificity phosphatases have recently emerged as important participants in maintaining balance within the PN, acting through modulation of cellular signaling pathways that are involved in neurodegeneration. In this review, we will summarize recent findings describing the roles of dual-specificity phosphatases in neurodegeneration and offer perspectives on future therapeutic directions.

Monocarboxylate transporter 1 (MCT1), a tool to stratify acute myeloid leukemia (AML) patients and a vehicle to kill cancer cells

Dysregulation of glucose/lactate dynamics plays a role in cancer progression, and MCTs are key elements in metabolic remodeling. VEGF is a relevant growth factor in the maintenance of bone marrow microenvironment and it is also important in hematological diseases.

Our aim was to investigate the role of VEGF in the metabolic adaptation of Acute myeloid leukemia (AML) cells by evaluating the metabolic profiles and cell features according to the AML lineage and testing lactate as a metabolic coin.

Our in vitro results showed that AML promyelocytic (HL60) and monocytic (THP1) (but not erythroid- HEL) lineages are well adapted to VEGF and lactate rich environment. Their metabolic adaptation relies on high rates of glycolysis to generate intermediates for PPP to support cell proliferation, and on the consumption of glycolysis-generated lactate to supply biomass and energy production. VEGF orchestrates this metabolic network by regulating MCT1 expression. Bromopyruvic acid (BPA) was proven to be an effective cytotoxic in AML, possibly transported by MCT1.

Our study reinforces that targeting metabolism can be a good strategy to fight cancer. MCT1 expression at the time of diagnosis can assist on the identification of AML patients that will benefit from BPA therapy. Additionally, MCT1 can be used in targeted delivery of conventional cytotoxic drugs.