Proliferating Cells Conserve Nitrogen to Support Growth

Metabolism and mRNA translation: a nexus of cancer plasticity

Tumors often face energy deprivation due to mutations, hypoxia, and nutritional deficiencies within the harsh tumor microenvironment (TME), and as an effect of anticancer treatments. This metabolic stress triggers adaptive reprogramming of mRNA translation, which in turn adjusts metabolic plasticity and associated signaling pathways to ensure tumor cell survival. Emerging evidence is beginning to reveal the complex interplay between metabolism and mRNA translation, shedding light on the mechanisms that synchronize ribosome assembly and reconfigure translation programs under metabolic stress. This review explores recent advances in our understanding of the coordination between metabolism and mRNA translation, offering insights that could inform therapeutic strategies targeting both cancer metabolism and translation, with the aim of disrupting cancer cell plasticity and survival.

Targeting glutamine metabolism in hepatic stellate cells alleviates liver fibrosis

Glutamine metabolism plays an essential role in cell growth, and glutamate dehydrogenase (GDH) is a key enzyme. GDH promotes the metabolism of glutamate and glutamine to generate ATP, which is profoundly increased in multiple human cancers. Through in vitro and in vivo experiments, we verified that the small-molecule GDH inhibitor EGCG slowed the progression of fibrosis by inhibiting GDH enzyme activity and glutamine metabolism. SIRT4 is a mitochondrial enzyme with NAD that promotes ADP ribosylation and downregulates GDH activity. The role of SIRT4 in liver fibrosis and the related mechanisms are unknown. In this study, we measured the expression of SIRT4 and found that it was downregulated in liver fibrosis. Modest overexpression of SIRT4 protected the liver from fibrosis by inhibiting the transformation of glutamate to 2-ketoglutaric acid (α-KG) in the tricarboxylic acid cycle (TCA), thereby reducing the proliferative activity of hepatic stellate cells (HSCs). Collectively, our study reveals that SIRT4 controls GDH enzyme activity and expression, targeting glutamine metabolism in HSCs and alleviating liver fibrosis.

Glutamine Metabolism Is Required for Collagen Protein Synthesis in Lung Fibroblasts

Idiopathic pulmonary fibrosis (IPF) is characterized by the transforming growth factor (TGF)-β-dependent differentiation of lung fibroblasts into myofibroblasts, leading to excessive deposition of extracellular matrix proteins, which distort lung architecture and function. Metabolic reprogramming in myofibroblasts is emerging as an important mechanism in the pathogenesis of IPF, and recent evidence suggests that glutamine metabolism is required in myofibroblasts, although the exact role of glutamine in myofibroblasts is unclear. In the present study, we demonstrate that glutamine and its conversion to glutamate by glutaminase are required for TGF-β-induced collagen protein production in lung fibroblasts. We found that metabolism of glutamate to α-ketoglutarate by glutamate dehydrogenase or the glutamate-pyruvate or glutamate-oxaloacetate transaminases is not required for collagen protein production. Instead, we discovered that the glutamate-consuming enzymes phosphoserine aminotransferase 1 (PSAT1) and aldehyde dehydrogenase 18A1 (ALDH18A1)/Δ¹-pyrroline-5-carboxylate synthetase (P5CS) are required for collagen protein production by lung fibroblasts. PSAT1 is required for de novo glycine production, whereas ALDH18A1/P5CS is required for de novo proline production. Consistent with this, we found that TGF-β treatment increased cellular concentrations of glycine and proline in lung fibroblasts. Our results suggest that glutamine metabolism is required to promote amino acid biosynthesis and not to provide intermediates such as α-ketoglutarate for oxidation in mitochondria. In support of this, we found that inhibition of glutaminolysis has no effect on cellular oxygen consumption and that knockdown of oxoglutarate dehydrogenase has no effect on the ability of fibroblasts to produce collagen protein. Our results suggest that amino acid biosynthesis pathways may represent novel therapeutic targets for treatment of fibrotic diseases, including IPF.

Label-free cervicovaginal fluid proteome profiling reflects the cervix neoplastic transformation

Cervicovaginal fluid (CVF) is a valuable source of clinical information about the female reproductive tract in both nonpregnant and pregnant women. The aim of this study is to specify the CVF proteome at different stages of cervix neoplastic transformation by label-free quantitation approach based on liquid chromatography tandem mass spectrometry (LC-MS/MS) method. The proteome composition of CVF from 40 women of reproductive age with human papillomavirus (HPV)-associated cervix neoplastic transformation (low-grade squamous intraepithelial lesion [LSIL], high-grade squamous intraepithelial lesion [HSIL], and CANCER) was investigated. Hierarchical clustering and principal component analysis (PCA) of the proteomic data obtained by a label-free quantitation approach show the distribution of the sample set between four major clusters (no intraepithelial lesion or malignancy [NILM], LSIL, HSIL and CANCER) depending on the form of cervical lesion. Multisample ANOVA with subsequent Welch's t test resulted in 117 that changed significantly across the four clinical stages, including 27 proteins significantly changed in cervical cancer. Some of them were indicated as promising biomarkers previously (ACTN4, VTN, ANXA1, CAP1, ANXA2, and MUC5B). CVF proteomic data from the discovery stage were analyzed by the partial least squares-discriminant analysis (PLS-DA) method to build a statistical model, allowing to differentiate severe dysplasia (HSIL and CANCER) from the mild/normal stage (NILM and LSIL), and receiver operating characteristic (ROC) area under the curve (AUC) were obtained on an independent set of 33 samples. The sensitivity of the model was 77%, and the specificity was 94%; AUC was equal to 0.87. CVF proteome proved to be reflect the stage of cervical epithelium neoplastic process.

Undercover: gene control by metabolites and metabolic enzymes

In this review, van der Knapp and Verrijzer discuss the current understanding of the molecular mechanisms connecting metabolism to gene expression and their implications for development and disease.

To make the appropriate developmental decisions or maintain homeostasis, cells and organisms must coordinate the expression of their genome and metabolic state. However, the molecular mechanisms that relay environmental cues such as nutrient availability to the appropriate gene expression response remain poorly understood. There is a growing awareness that central components of intermediary metabolism are cofactors or cosubstrates of chromatin-modifying enzymes. As such, their concentrations constitute a potential regulatory interface between the metabolic and chromatin states. In addition, there is increasing evidence for a direct involvement of classic metabolic enzymes in gene expression control. These dual-function proteins may provide a direct link between metabolic programing and the control of gene expression. Here, we discuss our current understanding of the molecular mechanisms connecting metabolism to gene expression and their implications for development and disease.

Deep-proteome mapping of WM-266-4 human metastatic melanoma cells: From oncogenic addiction to druggable targets

Cutaneous melanoma is a malignant tumor of skin melanocytes that are pigment-producing cells located in the basal layer (stratum basale) of epidermis. Accumulation of genetic mutations within their oncogenes or tumor-suppressor genes compels melanocytes to aberrant proliferation and spread to distant organs of the body, thereby resulting in severe and/or lethal malignancy. Metastatic melanoma's heavy mutational load, molecular heterogeneity and resistance to therapy necessitate the development of novel biomarkers and drug-based protocols that target key proteins involved in perpetuation of the disease. To this direction, we have herein employed a nano liquid chromatography-tandem mass spectrometry (nLC-MS/MS) proteomics technology to profile the deep-proteome landscape of WM-266-4 human metastatic melanoma cells. Our advanced melanoma-specific catalogue proved to contain 6,681 unique proteins, which likely constitute the hitherto largest single cell-line-derived proteomic collection of the disease. Through engagement of UNIPROT, DAVID, KEGG, PANTHER, INTACT, CYTOSCAPE, dbEMT and GAD bioinformatics resources, WM-266-4 melanoma proteins were categorized according to their sub-cellular compartmentalization, function and tumorigenicity, and successfully reassembled in molecular networks and interactomes. The obtained data dictate the presence of plastically inter-converted sub-populations of non-cancer and cancer stem cells, and also indicate the oncoproteomic resemblance of melanoma to glioma and lung cancer. Intriguingly, WM-266-4 cells seem to be subjected to both epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial (MET) programs, with 1433G and ADT3 proteins being identified in the EMT/MET molecular interface. Oncogenic addiction of WM-266-4 cells to autocrine/paracrine signaling of IL17-, DLL3-, FGF(2/13)- and OSTP-dependent sub-routines suggests their critical contribution to the metastatic melanoma chemotherapeutic refractoriness. Interestingly, the 1433G family member that is shared between the BRAF- and EMT/MET-specific interactomes likely emerges as a novel and promising druggable target for the malignancy. Derailed proliferation and metastatic capacity of WM-266-4 cells could also derive from their metabolic addiction to pathways associated with glutamate/ammonia, propanoate and sulfur homeostasis, whose successful targeting may prove beneficial for advanced melanoma-affected patients.