Upregulation of phosphoserine phosphatase contributes to tumor progression and predicts poor prognosis in non-small cell lung cancer patients

PHGDH: a novel therapeutic target in cancer

Serine is a key contributor to the generation of one-carbon units for DNA synthesis during cellular proliferation. In addition, it plays a crucial role in the production of antioxidants that prevent abnormal proliferation and stress in cancer cells. In recent studies, the relationship between cancer metabolism and the serine biosynthesis pathway has been highlighted. In this context, 3-phosphoglycerate dehydrogenase (PHGDH) is notable as a key enzyme that functions as the primary rate-limiting enzyme in the serine biosynthesis pathway, facilitating the conversion of 3-phosphoglycerate to 3-phosphohydroxypyruvate. Elevated PHGDH activity in diverse cancer cells is mediated through genetic amplification, posttranslational modification, increased transcription, and allosteric regulation. Ultimately, these characteristics allow PHGDH to not only influence the growth and progression of cancer but also play an important role in metastasis and drug resistance. Consequently, PHGDH has emerged as a crucial focal point in cancer research. In this review, the structural aspects of PHGDH and its involvement in one-carbon metabolism are investigated, and PHGDH is proposed as a potential therapeutic target in diverse cancers. By elucidating how PHGDH expression promotes cancer growth, the goal of this review is to provide insight into innovative treatment strategies. This paper aims to reveal how PHGDH inhibitors can overcome resistance mechanisms, contributing to the development of effective cancer treatments.

Cycling back to folate metabolism in cancer

Metabolic changes contribute to cancer initiation and progression through effects on cancer cells, the tumor microenvironment and whole-body metabolism. Alterations in serine metabolism and the control of one-carbon cycles have emerged as critical for the development of many tumor types. In this Review, we focus on the mitochondrial folate cycle. We discuss recent evidence that, in addition to supporting nucleotide synthesis, mitochondrial folate metabolism also contributes to metastasis through support of antioxidant defense, mitochondrial protein synthesis and the overflow of excess formate. These observations offer potential therapeutic opportunities, including the modulation of formate metabolism through dietary interventions and the use of circulating folate cycle metabolites as biomarkers for cancer detection.

Targeting serine/glycine metabolism improves radiotherapy response in non-small cell lung cancer

BACKGROUND

Lung cancer is the most lethal cancer, and 85% of cases are classified as non-small cell lung cancer (NSCLC). Metabolic rewiring is a cancer hallmark that causes treatment resistance, and lacks insights into serine/glycine pathway adaptations upon radiotherapy.

METHODS

We analyzed radiotherapy responses using mass-spectrometry-based metabolomics in NSCLC patient's plasma and cell lines. Efficacy of serine/glycine conversion inhibitor sertraline with radiotherapy was investigated by proliferation, clonogenic and spheroid assays, and in vivo using a serine/glycine dependent NSCLC mouse model by assessment of tumor growth, metabolite and cytokine levels, and immune signatures.

RESULTS

Serine/glycine pathway metabolites were significantly consumed in response to radiotherapy in NSCLC patients and cell models. Combining sertraline with radiotherapy impaired NSCLC proliferation, clonogenicity and stem cell self-renewal capacity. In vivo, NSCLC tumor growth was reduced solely in the sertraline plus radiotherapy combination treatment group. Tumor weights linked to systemic serine/glycine pathway metabolite levels, and were inhibited in the combination therapy group. Interestingly, combination therapy reshaped the tumor microenvironment via cytokines associated with natural killer cells, supported by eradication of immune checkpoint galectin-1 and elevated granzyme B levels.

CONCLUSION

Our findings highlight that targeting serine/glycine metabolism using sertraline restricts cancer cell recovery from radiotherapy and provides tumor control through immunomodulation in NSCLC.

Evaluating Metabolite-Based Biomarkers for Early Diagnosis of Pancreatic Cancer: A Systematic Review

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers, with five-year survival rates around 10%. The only curative option remains complete surgical resection, but due to the delay in diagnosis, less than 20% of patients are eligible for surgery. Therefore, discovering diagnostic biomarkers for early detection is crucial for improving clinical outcomes. Metabolomics has become a powerful technology for biomarker discovery, and several metabolomic-based panels have been proposed for PDAC diagnosis, but these advances have not yet been translated into the clinic. Therefore, this review focused on summarizing metabolites identified for the early diagnosis of PDAC in the last five years. Bibliographic searches were performed in the PubMed, Scopus and WOS databases, using the terms "Biomarkers, Tumor", "Pancreatic Neoplasms", "Early Diagnosis", "Metabolomics" and "Lipidome" (January 2018-March 2023), and resulted in the selection of fourteen original studies that compared PDAC patients with subjects with other pancreatic diseases. These investigations showed amino acid and lipid metabolic pathways as the most commonly altered, reflecting their potential for biomarker research. Furthermore, other relevant metabolites such as glucose and lactate were detected in the pancreas tissue and body fluids from PDAC patients. Our results suggest that the use of metabolomics remains a robust approach to improve the early diagnosis of PDAC. However, these studies showed heterogeneity with respect to the metabolomics techniques used and further studies will be needed to validate the clinical utility of these biomarkers.

Curcuminoids as Anticancer Drugs: Pleiotropic Effects, Potential for Metabolic Reprogramming and Prospects for the Future

The number of published studies on curcuminoids in cancer research, including its lead molecule curcumin and synthetic analogs, has been increasing substantially during the past two decades. Insights on the diversity of inhibitory effects they have produced on a multitude of pathways involved in carcinogenesis and tumor progression have been provided. As this wealth of data was obtained in settings of various experimental and clinical data, this review first aimed at presenting a chronology of discoveries and an update on their complex in vivo effects. Secondly, there are many interesting questions linked to their pleiotropic effects. One of them, a growing research topic, relates to their ability to modulate metabolic reprogramming. This review will also cover the use of curcuminoids as chemosensitizing molecules that can be combined with several anticancer drugs to reverse the phenomenon of multidrug resistance. Finally, current investigations in these three complementary research fields raise several important questions that will be put among the prospects for the future research related to the importance of these molecules in cancer research.

Serine and glycine metabolism-related gene expression signature stratifies immune profiles of brain gliomas, and predicts prognosis and responses to immunotherapy

Glioma is one of the most lethal cancers and causes more than 200,000 deaths every year. Immunotherapy was an inspiring therapy for multiple cancers but failed in glioma treatment. The importance of serine and glycine and their metabolism has been well-recognized in the physiology of immune cells and microenvironment in multiple cancers. However, their correlation with prognosis, immune cells, and immune microenvironment of glioma remains unclear. In this study, we investigated the relationships between the expression pattern of serine and glycine metabolism-related genes (SGMGs) and clinicopathological features, prognosis, and tumor microenvironment in glioma based on comprehensive analyses of multiple public datasets and our cohort. According to the expression of SGMGs, we conducted the consensus clustering analysis to stratify all patients into four clusters with remarkably distinctive clinicopathological features, prognosis, immune cell infiltration, and immune microenvironment. Subsequently, a serine and glycine metabolism-related genes signature (SGMRS) was constructed based on five critical SGMGs in glioma to stratify patients into SGMRS high- and low-risk groups and tested for its prognostic value. Higher SGMRS expressed genes associated with the synthesis of serine and glycine at higher levels and manifested poorer prognosis. Besides, we confirmed that SGMRS was an independent prognostic factor and constructed nomograms with satisfactory prognosis prediction performance based on SGMRS and other factors. Analyzing the relationship between SGMRS and immune landscape, we found that higher SGMRS correlated with 'hotter' immunological phenotype and more immune cell infiltration. Furthermore, the expression levels of multiple immunotherapy-related targets, including PD-1, PD-L1, and B7-H3, were positively correlated with SGMRS, which was validated by the better predicted response to immune checkpoint inhibitors. In conclusion, our study explored the relationships between the expression pattern of SGMGs and tumor features and created novel models to predict the prognosis of glioma patients. The correlation of SGMRS with immune cells and microenvironment in gliomas suggested an essential role of serine and glycine metabolism in reforming immune cells and microenvironment. Finally, the results of our study endorsed the potential application of SGMRS to guide the selection of immunotherapy for gliomas.

The ins and outs of serine and glycine metabolism in cancer

Cancer cells reprogramme their metabolism to support unrestrained proliferation and survival in nutrient-poor conditions. Whereas non-transformed cells often have lower demands for serine and glycine, several cancer subtypes hyperactivate intracellular serine and glycine synthesis and become addicted to de novo production. Copy-number amplifications of serine- and glycine-synthesis genes and genetic alterations in common oncogenes and tumour-suppressor genes enhance serine and glycine synthesis, resulting in high production and secretion of these oncogenesis-supportive metabolites. In this Review, we discuss the contribution of serine and glycine synthesis to cancer progression. By relying on de novo synthesis pathways, cancer cells are able to enhance macromolecule synthesis, neutralize high levels of oxidative stress and regulate methylation and tRNA formylation. Furthermore, we discuss the immunosuppressive potential of serine and glycine, and the essentiality of both amino acids to promoting survival of non-transformed neighbouring cells. Finally, we point to the emerging data proposing moonlighting functions of serine- and glycine-synthesis enzymes and examine promising small molecules targeting serine and glycine synthesis.

LKB1 deficiency-induced metabolic reprogramming in tumorigenesis and non-neoplastic diseases

Background

Live kinase B1 (LKB1) is a tumor suppressor that is mutated in Peutz-Jeghers syndrome (PJS) and a variety of cancers. Lkb1 encodes serine-threonine kinase (STK) 11 that activates AMP-activated protein kinase (AMPK) and its 13 superfamily members, regulating multiple biological processes, such as cell polarity, cell cycle arrest, embryo development, apoptosis, and bioenergetics metabolism. Increasing evidence has highlighted that deficiency of LKB1 in cancer cells induces extensive metabolic alterations that promote tumorigenesis and development. LKB1 also participates in the maintenance of phenotypes and functions of normal cells through metabolic regulation.

Scope of review

Given the important role of LKB1 in metabolic regulation, we provide an overview of the association of metabolic alterations in glycolysis, aerobic oxidation, the pentose phosphate pathway (PPP), gluconeogenesis, glutamine, lipid, and serine induced by aberrant LKB1 signals in tumor progression, non-neoplastic diseases, and functions of immune cells.

Major conclusions

In this review, we summarize layers of evidence demonstrating that disordered metabolisms in glucose, glutamine, lipid, and serine caused by LKB1 deficiency promote carcinogenesis and non-neoplastic diseases. The metabolic reprogramming resulting from the loss of LKB1 confers cancer cells with growth or survival advantages. Nevertheless, it also causes a metabolic frangibility for LKB1-deficient cancer cells. The metabolic regulation of LKB1 also plays a vital role in maintaining cellular phenotype in the progression of non-neoplastic diseases. In addition, lipid metabolic regulation of LKB1 plays an important role in controlling the function, activity, proliferation, and differentiation of several types of immune cells. We conclude that in-depth knowledge of metabolic pathways regulated by LKB1 is conducive to identifying therapeutic targets and developing drug combinations to treat cancers and metabolic diseases and achieve immunoregulation.

PSPH induces cell autophagy and promotes cell proliferation and invasion in the hepatocellular carcinoma cell line Huh7 via the AMPK/mTOR/ULK1 signaling pathway

Phosphoserine phosphatase (PSPH), a key enzyme of the l-serine synthesis pathway, has been involved in cancer progression and survival. However, limited evidence revealed the PSPH influence on hepatocellular carcinoma (HCC). Herein, we observed that PSPH expression was upregulated in both HCC tissues and cell lines, which was determined by western blotting. TCGA database showed that the PSPH protein levels were significantly upregulated and affected patient survival rates in HCC. Then gain- and loss-of-function manipulations were performed by transfection with a pcDNA-PSPH expression vector or a specific short interfering RNA against PSPH in Huh7 cells. Huh7 cell proliferation, stemness, invasion, and apoptosis were assessed by using CCK-8 test, colony formation assay, Transwell assay, and Flow cytometry analysis, respectively, and levels of autophagy-related proteins were detected by using western blotting. The results showed that PSPH could induce Huh7 cell autophagy, promote cell proliferation and invasion, and inhibit apoptosis. The knockdown of PSPH could inhibit Huh7 cell proliferation, invasion, and autophagy. Furthermore, PSPH activated Liver kinase B1 (LKB1) and TGF beta-activated kinase 1 (TAK1), affected the adenosine 5'-monophosphate-activated protein kinase (AMPK)/mTOR/ULK1 signaling pathway, but could not activate calcium/calmodulin-dependent protein kinase kinase (CaMKK) in Huh7 cells. Inhibition of either LKB1, TAK1, or AMPK could eliminate the effect of PSPH overexpression on Huh7 cell behaviors. However, inhibition of CaMKK could not influence the effect of PSPH overexpression on Huh7 cell behaviors. In conclusion, PSPH could induce autophagy, promote proliferation and invasion, and inhibit apoptosis in HCC cells via the AMPK/mTOR/ULK1 signaling pathway.