Expression and clinical significance of phosphoglycerate dehydrogenase and squamous cell carcinoma antigen in cervical cancer

MAPK-mediated PHGDH induction is essential for melanoma formation and represents an actionable vulnerability

Overexpression of PHGDH, the rate-limiting enzyme in the serine synthesis pathway, promotes melanomagenesis, melanoma cell proliferation, and survival of metastases in serine-low environments such as the brain. While PHGDH amplification explains PHGDH overexpression in a subset of melanomas, we find that PHGDH levels are universally increased in melanoma cells due to oncogenic BRAFV600E promoting PHGDH transcription through mTORC1-mediated translation of ATF4. Importantly, PHGDH expression was critical for melanomagenesis as depletion of PHGDH in genetic mouse models blocked melanoma formation. Despite BRAFV600E-mediated upregulation, PHGDH was further induced by exogenous serine restriction. Surprisingly, BRAFV600E inhibition diminished serine restriction-mediated PHGDH expression by preventing ATF4 induction, creating a potential vulnerability whereby melanoma cells could be specifically starved of serine by combining BRAFV600E inhibition with exogenous serine restriction. Indeed, we show that this combination promoted cell death in vitro and attenuated melanoma growth in vivo. This study identified a melanoma cell-specific PHGDH-dependent vulnerability.

Serine-associated one-carbon metabolic reprogramming: a new anti-cancer therapeutic strategy

Tumour metabolism is a major focus of cancer research, and metabolic reprogramming is an important feature of malignant tumours. Serine is an important non-essential amino acid, which is a main resource of one-carbon units in tumours. Cancer cells proliferate more than normal cells and require more serine for proliferation. The cancer-related genes that are involved in serine metabolism also show changes corresponding to metabolic alterations. Here, we reviewed the serine-associated one-carbon metabolism and its potential as a target for anti-tumour therapeutic strategies.

Comprehensive analysis of PHGDH for predicting prognosis and immunotherapy response in patients with endometrial carcinoma

BACKGROUND

PHGDH (Phosphoglycerate Dehydrogenase) is the first branch enzyme in the serine biosynthetic pathway and plays a vital role in several cancers. However, little is known about the clinical significance of PHGDH in endometrial cancer.

METHODS

Clinicopathological data of endometrial cancer were downloaded from the Cancer Genome Atlas database (TCGA). First, the expression of PHGDH in pan-cancer was investigated, as well as the expression and prognostic value of PHGDH in endometrial cancer. The effect of PHGDH expression on the prognosis of endometrial cancer was analyzed by Kaplan-Meier plotter and Cox regression. The relationship between PHGDH expression and clinical characteristics of endometrial cancer was investigated by logistic regression. Receiver operating characteristic (ROC) curves and nomograms were developed. Possible cellular mechanisms were explored using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, the Gene Ontology (GO), and gene set enrichment analysis (GSEA). Finally, TIMER and CIBERSORT were used to analyze the relationship between PHGDH expression and immune infiltration. CellMiner™ was used to analyze the drug sensitivity of PHGDH.

RESULTS

The results showed that PHGDH expression was significantly higher in endometrial cancer tissues than in normal tissues at mRNA and protein levels. Kaplan-Meier survival curves showed that patients in the high expression group had shorter overall survival (OS) and disease free survival (DFS) than patients in the low PHGDH expression group. Multifactorial COX regression analysis further supported that high PHGDH expression was an independent risk factor associated with prognosis in patients with endometrial cancer. The results showed estrogen response, mTOR, K-RAS, and epithelial mesenchymal transition (EMT) were differentially elevated in the high-expression group of the PHGDH group. CIBERSORT analysis showed that PHGDH expression is related to the infiltration of multiple immune cells. When PHGDH is highly expressed, the number of CD8⁺T cells decreases.

CONCLUSION

PHGDH plays a vital role in the development of endometrial cancer, which is related to tumor immune infiltration, and can be used as an independent diagnostic and prognostic marker for endometrial cancer.

Circulating metabolites associated with tumor hypoxia and early response to treatment in bevacizumab-refractory glioblastoma after combined bevacizumab and evofosfamide

Glioblastomas (GBM) are the most common and aggressive form of primary malignant brain tumor in the adult population, and, despite modern therapies, patients often develop recurrent disease, and the disease remains incurable with median survival below 2 years. Resistance to bevacizumab is driven by hypoxia in the tumor and evofosfamide is a hypoxia-activated prodrug, which we tested in a phase 2, dual center (University of Texas Health Science Center in San Antonio and Dana Farber Cancer Institute) clinical trial after bevacizumab failure. Tumor hypoxic volume was quantified by 18F-misonidazole PET. To identify circulating metabolic biomarkers of tumor hypoxia in patients, we used a high-resolution liquid chromatography-mass spectrometry-based approach to profile blood metabolites and their specific enantiomeric forms using untargeted approaches. Moreover, to evaluate early response to treatment, we characterized changes in circulating metabolite levels during treatment with combined bevacizumab and evofosfamide in recurrent GBM after bevacizumab failure. Gamma aminobutyric acid, and glutamic acid as well as its enantiomeric form D-glutamic acid all inversely correlated with tumor hypoxia. Intermediates of the serine synthesis pathway, which is known to be modulated by hypoxia, also correlated with tumor hypoxia (phosphoserine and serine). Moreover, following treatment, lactic acid was modulated by treatment, likely in response to a hypoxia mediated modulation of oxidative vs glycolytic metabolism. In summary, although our results require further validation in larger patients’ cohorts, we have identified candidate metabolic biomarkers that could evaluate the extent of tumor hypoxia and predict the benefit of combined bevacizumab and evofosfamide treatment in GBM following bevacizumab failure.

Metabolic targeting of malignant tumors: a need for systemic approach

PURPOSE

Dysregulated metabolism is now recognized as a fundamental hallmark of carcinogenesis inducing aggressive features and additional hallmarks. In this review, well-established metabolic changes displayed by tumors are highlighted in a comprehensive manner and corresponding therapeutical targets are discussed to set up a framework for integrating basic research findings with clinical translation in oncology setting.

METHODS

Recent manuscripts of high research impact and relevant to the field from PubMed (2000-2021) have been reviewed for this article.

RESULTS

Metabolic pathway disruption during tumor evolution is a dynamic process potentiating cell survival, dormancy, proliferation and invasion even under dismal conditions. Apart from cancer cells, though, tumor microenvironment has an acting role as extracellular metabolites, pH alterations and stromal cells reciprocally interact with malignant cells, ultimately dictating tumor-promoting responses, disabling anti-tumor immunity and promoting resistance to treatments.

CONCLUSION

In the field of cancer metabolism, there are several emerging prognostic and therapeutic targets either in the form of gene expression, enzyme activity or metabolites which could be exploited for clinical purposes; both standard-of-care and novel treatments may be evaluated in the context of metabolism rewiring and indeed, synergistic effects between metabolism-targeting and other therapies would be an attractive perspective for further research.

Dynamic transcriptome profiling reveals essential roles of the Receptor Tyrosine Kinases (RTK) family in feather development of duck

1. Chicken primary myoblasts (CPMs) are precursors that form muscle fibres. The proliferation and differentiation of CPMs is an essential stage in muscle development. Previous RNA-seq analysis showed that phosphoglycerate dehydrogenase (PHGDH) is a differentially expressed gene in chicken muscle tissue at different growth stages. Therefore, the following study explored the effect of PHGDH on the proliferation and differentiation of CPMs.2. The effect on the proliferation of CPMs by RT-qPCR, CCK-8, and EdU assays after the overexpression and knockdown of PHGDH was evaluated. RT-qPCR, western blotting, and indirect immunofluorescence were used to detect the effect of PHGDH on the differentiation of the CPMs. The expression was observed at different time points for differentiation induced by the CPMs.3. The results showed that PHGDH significantly promoted proliferation and differentiation in CPMs. The results showed that overexpression of PHGDH significantly upregulated CPM proliferation, while knockdown had the opposite effect. Marker genes showed that overexpression of PHGDH significantly upregulated the expression of P21, MYOG and MYOD genes, significantly downregulated the expression of the MSTN gene and promoted the expression of the MYHC protein. In contrast, PHGDH knockdown had the opposite effect.4. Desmin immunofluorescence analysis of myotube differentiation in primary myoblasts showed that overexpression of PHGDH significantly increased the area of myotube differentiation and promoted the proliferation and differentiation of myoblasts. Knockdown of PHGDH had the opposite effect.5. In summary, PHGDH was shown to play a positive role in regulating myoblast proliferation and differentiation. This provided a theoretical basis for further analysis of the regulatory mechanism of the PHGDH gene in chicken muscle development and for improving poultry production.

PHGDH promotes the proliferation and differentiation of primary chicken myoblasts

1. Chicken primary myoblasts (CPMs) are precursors that form muscle fibres. The proliferation and differentiation of CPMs is an essential stage in muscle development. Previous RNA-seq analysis showed that phosphoglycerate dehydrogenase (PHGDH) is a differentially expressed gene in chicken muscle tissue at different growth stages. Therefore, the following study explored the effect of PHGDH on the proliferation and differentiation of CPMs.2. The effect on the proliferation of CPMs by RT-qPCR, CCK-8, and EdU assays after the overexpression and knockdown of PHGDH was evaluated. RT-qPCR, western blotting, and indirect immunofluorescence were used to detect the effect of PHGDH on the differentiation of the CPMs. The expression was observed at different time points for differentiation induced by the CPMs.3. The results showed that PHGDH significantly promoted proliferation and differentiation in CPMs. The results showed that overexpression of PHGDH significantly upregulated CPM proliferation, while knockdown had the opposite effect. Marker genes showed that overexpression of PHGDH significantly upregulated the expression of P21, MYOG and MYOD genes, significantly downregulated the expression of the MSTN gene and promoted the expression of the MYHC protein. In contrast, PHGDH knockdown had the opposite effect.4. Desmin immunofluorescence analysis of myotube differentiation in primary myoblasts showed that overexpression of PHGDH significantly increased the area of myotube differentiation and promoted the proliferation and differentiation of myoblasts. Knockdown of PHGDH had the opposite effect.5. In summary, PHGDH was shown to play a positive role in regulating myoblast proliferation and differentiation. This provided a theoretical basis for further analysis of the regulatory mechanism of the PHGDH gene in chicken muscle development and for improving poultry production.

Identification of Novel Diagnostic Markers for Malignant Pleural Mesothelioma Using a Reverse Translational Approach Based on a Rare Synchronous Tumor

Although the routine use of immunohistochemistry has improved the accuracy of histopathologic diagnosis in clinical practice, new methods for discovering novel diagnostic markers are still needed. We sought new diagnostic markers for malignant pleural mesothelioma (MPM) using a reverse translational approach with limited archival tissues from a very rare case. Total RNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues of a synchronous collision tumor consisting of MPM and pulmonary adenocarcinoma (PAC) was employed for gene expression profiling (GEP) analysis. Among the 54 genes selected by GEP analysis, we finally identified the following two candidate MPM marker genes: PHGDH and TRIM29. Immunohistochemical analysis of 48 MM and 20 PAC cases showed that both PHGDH and TRIM29 had sensitivity and specificity almost equivalent to those of calretinin (sensitivity 50% and 46% vs. 63%, and specificity 95% and 100% vs. 100%, respectively). Importantly, of the 23 epithelioid MMs, all 3 calretinin-negative cases were positive for TRIM29. These two markers may be diagnostically useful for immunohistochemical distinction between MPMs and PACs. This successful reverse translational approach based on FFPE samples from one very rare case encourages the further use of such samples for the development of novel diagnostic markers.

Cancer Cell Metabolism in Hypoxia: Role of HIF-1 as Key Regulator and Therapeutic Target

In order to meet the high energy demand, a metabolic reprogramming occurs in cancer cells. Its role is crucial in promoting tumor survival. Among the substrates in demand, oxygen is fundamental for bioenergetics. Nevertheless, tumor microenvironment is frequently characterized by low-oxygen conditions. Hypoxia-inducible factor 1 (HIF-1) is a pivotal modulator of the metabolic reprogramming which takes place in hypoxic cancer cells. In the hub of cellular bioenergetics, mitochondria are key players in regulating cellular energy. Therefore, a close crosstalk between mitochondria and HIF-1 underlies the metabolic and functional changes of cancer cells. Noteworthy, HIF-1 represents a promising target for novel cancer therapeutics. In this review, we summarize the molecular mechanisms underlying the interplay between HIF-1 and energetic metabolism, with a focus on mitochondria, of hypoxic cancer cells.

Phgdh serves a protective role in Il‑1β induced chondrocyte inflammation and oxidative‑stress damage

The primary pathological changes observed in osteoarthritis (OA) involve inflammation and degeneration of chondrocytes. 3‑phosphoglycerate dehydrogenase (Phgdh), a rate‑limiting enzyme involved in the conversion of 3‑phosphoglycerate to serine, serves as a crucial molecular component of cell growth and metabolism. However, its effects on chondrocytes in OA have not been determined. In the present study, a rat model of OA was used to investigate the expression levels of Phgdh in vivo and in vitro. Additionally, the role of Phgdh in extracellular matrix (ECM) synthesis, inflammation, apoptosis and oxidative stress levels of chondrocytes was detected in vitro. Phgdh expression was decreased in OA, and Phgdh overexpression promoted ECM synthesis, decreased levels inflammatory cytokines, such as Il‑6, TNF‑α, a disintegrin and metalloproteinase with thrombospondin motifs 5 and MMP13, and decreased apoptosis. Furthermore, expression of Phgdh effectively increased expression levels of the cellular antioxidant enzymes catalase and superoxide dismutase 1, and decreased the levels of reactive oxygen species in chondrocytes; and this may have been regulated by a Kelch like ECH associated protein 1/nuclear factor erythroid 2‑related factor 2 axis. Taken together, these results suggest that Phgdh may be used to manage the progression of OA.

3-Phosphoglycerate dehydrogenase: a potential target for cancer treatment

BACKGROUND

Metabolic changes have been recognized as an important hallmark of cancer cells. Cancer cells can promote their own growth and proliferation through metabolic reprogramming. Particularly, serine metabolism has frequently been reported to be dysregulated in tumor cells. 3-Phosphoglycerate dehydrogenase (PHGDH) catalyzes the first step in the serine biosynthesis pathway and acts as a rate-limiting enzyme involved in metabolic reprogramming. PHGDH upregulation has been observed in many tumor types, and inhibition of PHGDH expression has been reported to inhibit the proliferation of PHGDH-overexpressing tumor cells, indicating that it may be utilized as a target for cancer treatment. Recently identified inhibitors targeting PHGDH have already shown effectiveness. A further in-depth analysis and concomitant development of PHGDH inhibitors will be of great value for the treatment of cancer.

CONCLUSIONS

In this review we describe in detail the role of PHGDH in various cancers and inhibitors that have recently been identified to highlight progression in cancer treatment. We also discuss the development of new drugs and treatment modalities based on PHGDH targets. Overexpression of PHGDH has been observed in melanoma, breast cancer, nasopharyngeal carcinoma, parathyroid adenoma, glioma, cervical cancer and others. PHGDH may serve as a molecular biomarker for the diagnosis, prognosis and treatment of these cancers. The design and development of novel PHGDH inhibitors may have broad implications for cancer treatment. Therapeutic strategies of PHGDH inhibitors in combination with traditional chemotherapeutic drugs may provide new perspectives for precision medicine and effective personalized treatment for cancer patients.

PHGDH as a mechanism for resistance in metabolically-driven cancers

At the forefront of cancer research is the rapidly evolving understanding of metabolic reprogramming within cancer cells. The expeditious adaptation to metabolic inhibition allows cells to evolve and acquire resistance to targeted treatments, which makes therapeutic exploitation complex but achievable. 3-phosphoglycerate dehydrogenase (PHGDH) is the rate-limiting enzyme of de novo serine biosynthesis and is highly expressed in a variety of cancers, including breast cancer, melanoma, and Ewing’s sarcoma. This review will investigate the role of PHGDH in normal biological processes, leading to the role of PHGDH in the progression of cancer. With an understanding of the molecular mechanisms by which PHGDH expression advances cancer growth, we will highlight the known mechanisms of resistance to cancer therapeutics facilitated by PHGDH biology and identify avenues for combatting PHGDH-driven resistance with inhibitors of PHGDH to allow for the development of effective metabolic therapies.

Oncology Therapeutics Targeting the Metabolism of Amino Acids

Amino acid metabolism promotes cancer cell proliferation and survival by supporting building block synthesis, producing reducing agents to mitigate oxidative stress, and generating immunosuppressive metabolites for immune evasion. Malignant cells rewire amino acid metabolism to maximize their access to nutrients. Amino acid transporter expression is upregulated to acquire amino acids from the extracellular environment. Under nutrient depleted conditions, macropinocytosis can be activated where proteins from the extracellular environment are engulfed and degraded into the constituent amino acids. The demand for non-essential amino acids (NEAAs) can be met through de novo synthesis pathways. Cancer cells can alter various signaling pathways to boost amino acid usage for the generation of nucleotides, reactive oxygen species (ROS) scavenging molecules, and oncometabolites. The importance of amino acid metabolism in cancer proliferation makes it a potential target for therapeutic intervention, including via small molecules and antibodies. In this review, we will delineate the targets related to amino acid metabolism and promising therapeutic approaches.

Increased PHGDH expression promotes aberrant melanin accumulation

BACKGROUND

Copy number gain of the D-3-phosphoglycerate dehydrogenase (PHGDH) gene, which encodes the first enzyme in serine biosynthesis, is found in some human cancers including a subset of melanomas.

METHODS

In order to study the effect of increased PHGDH expression in tissues in vivo, we generated mice harboring a PHGDH^tetO allele that allows tissue-specific, doxycycline-inducible PHGDH expression, and we analyzed the phenotype of mice with a ubiquitous increase in PHGDH expression.

RESULTS

Tissues and cells derived from PHGDH^tetO mice exhibit increased serine biosynthesis. Histological examination of skin tissue from PHGDH^tetO mice reveals the presence of melanin granules in early anagen hair follicles, despite the fact that melanin synthesis is closely coupled to the hair follicle cycle and does not normally begin until later in the cycle. This phenotype occurs in the absence of any global change in hair follicle cycle timing. The aberrant presence of melanin early in the hair follicle cycle following PHGDH expression is also accompanied by increased melanocyte abundance in early anagen skin.

CONCLUSIONS

These data suggest increased PHGDH expression impacts normal melanocyte biology, but PHGDH expression alone is not sufficient to cause cancer.

Deletion of PHGDH in adipocytes improves glucose intolerance in diet-induced obese mice

Serine is a nonessential amino acid and plays an important role in cellular metabolism. In mammalian serine biosynthesis, 3-phosphoglycerate dehydrogenase (PHGDH) is considered a rate-limiting enzyme and is required for normal development. Although the biological functions of PHGHD in the nervous system have been intensively studied, its function in adipose tissue is unknown. In this study, we found that PHGDH is abundantly expressed in mature adipocytes of white adipose tissue. We generated an adipocyte-specific PHGDH knockout mouse (PHGDH FKO) and used it to investigate the role of serine biosynthesis in adipose tissues. Although PHGDH FKO mice had no apparent defects in adipose tissue development, these mice ameliorated glucose intolerance upon diet-induced obesity. Additionally, we found that the serine levels increase drastically in the adipose tissues of obese wild type mice, whereas no significant rise was observed in PHGDH FKO mice. Furthermore, wild type mice fed a serine-deficient diet also exhibited better glucose tolerance. These results suggest that PHGDH-mediated serine biosynthesis has important roles in adipose tissue glucose metabolism and could be a therapeutic target for diabetes in humans.

Links between Serine Biosynthesis Pathway and Epigenetics in Cancer Metabolism

Cancer metabolism is considered as one of major cancer hallmarks. It is important to understand cancer-specific metabolic changes and its impact on cancer biology to identify therapeutic potentials. Among cancer-specific metabolic changes, a role of serine metabolism has been discovered in various cancer types. Upregulation of serine synthesis pathway (SSP) supports cell proliferation and metastasis. The change of serine metabolism is, in part, mediated by epigenetic modifiers, such as Euchromatic histone-lysine N-methyltransferase 2 and Lysine Demethylase 4C. On the other hand, SSP also influences epigenetic landscape such as methylation status of nucleic acids and histone proteins via affecting S-adenosyl methionine production. In the review, we highlight recent evidences on interactions between SSP and epigenetic regulation in cancer. It may provide an insight on roles and regulation of SSP in cancer metabolism and the potential of serine metabolism for cancer therapy.

Metabolic adaptation of cancer and immune cells mediated by hypoxia-inducible factors

Cancer cells are characterized by high metabolic demand. The substrates in demand include oxygen, glucose, glutamine and lipids. Oxygen serves as a key substrate in cellular metabolism and bioenergetics. Hypoxia or low oxygen abundance is a common feature of the tumor microenvironment that occurs due to an imbalance in supply and demand. Many of the metabolic responses to hypoxia in both cancer cells and stromal cells are orchestrated by hypoxia-inducible factors (HIFs). In this review we summarize our current understanding of how HIFs modulate the metabolism of hypoxic cancer cells and immune cells, and how altered metabolism plays a role in cancer progression.

Validating and enabling phosphoglycerate dehydrogenase (PHGDH) as a target for fragment-based drug discovery in PHGDH-amplified breast cancer

3-Phosphoglycerate dehydrogenase (PHGDH) has recently been identified as an attractive target in cancer therapy as it links upregulated glycolytic flux to increased biomass production in cancer cells. PHGDH catalyses the first step in the serine synthesis pathway and thus diverts glycolytic flux into serine synthesis. We have used siRNA-mediated suppression of PHGDH expression to show that PHGDH is a potential therapeutic target in PHGDH-amplified breast cancer. Knockdown caused reduced proliferation in the PHGDH-amplified cell line MDA-MB-468, whereas breast cancer cells with low PHGDH expression or with elevated PHGDH expression in the absence of genomic amplification were not affected. As a first step towards design of a chemical probe for PHGDH, we report a fragment-based drug discovery approach for the identification of PHGDH inhibitors. We designed a truncated PHGDH construct that gave crystals which diffracted to high resolution, and could be used for fragment soaking. 15 fragments stabilising PHGDH were identified using a thermal shift assay and validated by X-ray crystallography and ITC competition experiments to exhibit 1.5-26.2 mM affinity for PHGDH. A structure-guided fragment growing approach was applied to the PHGDH binders from the initial screen, yielding greater understanding of the binding site and suggesting routes to achieve higher affinity NAD-competitive inhibitors.

Cervical cancer systemic inflammation score: a novel predictor of prognosis

Inflammation contributes to development and progression in a variety of cancers, including cervical cancer. We developed a novel cervical cancer systemic inflammation score (CCSIS) based on the preoperative platelet-to-lymphocyte ratio (PLR) and serum albumin levels. A retrospective analysis of clinical data from 795 patients with operable cervical cancer was then conducted to investigate the prognostic value of CCSIS and its association with the patients' clinicopathological features, overall survival (OS), and disease-free survival (DFS). CCSIS was predictive of OS and DFS. High CCSIS was correlated with more advanced FIGO stages, poor tumor differentiation, and the presence of PLN and LVSI. Both albumin levels and the PLR were independent prognostic indicators for operable cervical cancer. The use of the CCSIS could improve risk stratification and traditional clinicopathological analysis in cervical cancer.

Serine Synthesis Helps Hypoxic Cancer Stem Cells Regulate Redox

Phosphoglycerate dehydrogenase (PHGDH) is the metabolic enzyme responsible for shunting the glycolytic intermediate 3-phosphoglycerate to the serine synthesis pathway. In breast cancer and several other types of cancer, increased PHGDH expression is associated with patient mortality. Early studies focused on the role of PHGDH in promoting cell proliferation in the small percentage of breast cancers with PHGDH gene amplification. However, recent studies have revealed a critical role for PHGDH and downstream enzymes of the serine synthesis pathway and one carbon metabolism in NADPH production and the maintenance of redox homeostasis, which are required for enrichment of breast cancer stem cells in response to hypoxia or chemotherapy. These results provide a mechanism for PHGDH overexpression in breast cancers in which PHGDH is not amplified and have implications for improving the response of triple-negative breast cancers to cytotoxic chemotherapy. Cancer Res; 76(22); 6458-62. ©2016 AACR.

Phosphoglycerate dehydrogenase is a novel predictor for poor prognosis in gastric cancer

PURPOSE

Phosphoglycerate dehydrogenase (PHGDH) acts as a key metabolic enzyme in the rate-limiting step in serine biosynthesis and plays an important role in metastasis of several cancers. The aim of this study was to investigate the prognostic value of PHGDH in gastric cancer (GC).

METHODS

The messenger RNA expression of PHGDH was determined in 20 pairs of cancerous and adjacent nontumor tissues by real-time polymerase chain reaction. Immunohistochemistry of PHGDH was performed on tissue microarray, composed of 482 GC and 64 matched adjacent nontumor tissues acquired from surgery, 20 chronic gastritis, 18 intestinal metaplasia, and 31 low-grade and 66 high-grade intraepithelial neoplasias acquired through gastric endoscopic biopsy. Univariate and multivariate Cox proportional hazard models were used to perform survival analyses.

RESULTS

Both PHGDH messenger RNA and protein product exhibited GC tissue-preferred expression, when compared with benign tissues. The high PHGDH expression was significantly correlated with histological type (P=0.011), tumor stage (P=0.014), and preoperative carcinoembryonic antigen (P<0.001). A negative correlation was found between PHGDH expression and the 5-year survival rate of patients with GC. Furthermore, multivariate analysis indicated that PHGDH was an independent prognostic factor for outcome in GC.

CONCLUSION

PHGDH is important in predicting patient outcomes and is a potential target for the development of therapeutic approaches to GC.

The importance of serine metabolism in cancer

Serine metabolism is frequently dysregulated in cancers; however, the benefit that this confers to tumors remains controversial. In many cases, extracellular serine alone is sufficient to support cancer cell proliferation, whereas some cancer cells increase serine synthesis from glucose and require de novo serine synthesis even in the presence of abundant extracellular serine. Recent studies cast new light on the role of serine metabolism in cancer, suggesting that active serine synthesis might be required to facilitate amino acid transport, nucleotide synthesis, folate metabolism, and redox homeostasis in a manner that impacts cancer.

Pathogenic Network Analysis Predicts Candidate Genes for Cervical Cancer

Purpose. The objective of our study was to predicate candidate genes in cervical cancer (CC) using a network-based strategy and to understand the pathogenic process of CC. Methods. A pathogenic network of CC was extracted based on known pathogenic genes (seed genes) and differentially expressed genes (DEGs) between CC and normal controls. Subsequently, cluster analysis was performed to identify the subnetworks in the pathogenic network using ClusterONE. Each gene in the pathogenic network was assigned a weight value, and then candidate genes were obtained based on the weight distribution. Eventually, pathway enrichment analysis for candidate genes was performed. Results. In this work, a total of 330 DEGs were identified between CC and normal controls. From the pathogenic network, 2 intensely connected clusters were extracted, and a total of 52 candidate genes were detected under the weight values greater than 0.10. Among these candidate genes, VIM had the highest weight value. Moreover, candidate genes MMP1, CDC45, and CAT were, respectively, enriched in pathway in cancer, cell cycle, and methane metabolism. Conclusion. Candidate pathogenic genes including MMP1, CDC45, CAT, and VIM might be involved in the pathogenesis of CC. We believe that our results can provide theoretical guidelines for future clinical application.

Downregulation of phosphoglycerate dehydrogenase inhibits proliferation and enhances cisplatin sensitivity in cervical adenocarcinoma cells by regulating Bcl-2 and caspase-3

Phosphoglycerate dehydrogenase (PHGDH) is the key enzyme of de novo serine biosynthesis. Previous reports have demonstrated that PHGDH plays an important role in some malignancies. However, the biological role of PHGDH in human cervical adenocarcinoma has not been explored. We examined the expression of PHGDH in 54 cervical adenocarcinoma samples by immunohistochemistry and evaluated the association with clinicopathological parameters and prognosis. We performed shRNA transfection to knock down PHGDH gene expression in HeLa cells. A cell proliferation test, cisplatin cytotoxicity test and apoptosis test examined the HeLa cell line after PHGDH knockdown in vitro. In vivo tumorigenesis was assessed using a mouse xenograft model. Moreover, we examined the effects on Bcl-2 and cleaved caspase-3 expression after knockdown of PHGDH and treatment of cisplatin for 48h by Western blot. In this study, we demonstrated that elevated PHGDH expression was found in cervical adenocarcinoma and was associated with tumor size and prognosis. Knocking down PHGDH in HeLa cells significantly inhibited cell proliferation and increased cisplatin chemotherapy sensitivity. Silencing PHGDH resulted in inhibition of tumorigenesis in vivo. Furthermore, PHGDH knockdown reduced Bcl-2 and increased cleaved caspase-3 expression. Collectively, our study indicates the novel roles of PHGDH in cervical adenocarcinoma and identifies PHGDH as a new anticancer target.

Phosphoglycerate dehydrogenase: potential therapeutic target and putative metabolic oncogene

Exemplified by cancer cells' preference for glycolysis, for example, the Warburg effect, altered metabolism in tumorigenesis has emerged as an important aspect of cancer in the past 10–20 years. Whether due to changes in regulatory tumor suppressors/oncogenes or by acting as metabolic oncogenes themselves, enzymes involved in the complex network of metabolic pathways are being studied to understand their role and assess their utility as therapeutic targets. Conversion of glycolytic intermediate 3-phosphoglycerate into phosphohydroxypyruvate by the enzyme phosphoglycerate dehydrogenase (PHGDH)—a rate-limiting step in the conversion of 3-phosphoglycerate to serine—represents one such mechanism. Forgotten since classic animal studies in the 1980s, the role of PHGDH as a potential therapeutic target and putative metabolic oncogene has recently reemerged following publication of two prominent papers near-simultaneously in 2011. Since that time, numerous studies and a host of metabolic explanations have been put forward in an attempt to understand the results observed. In this paper, I review the historic progression of our understanding of the role of PHGDH in cancer from the early work by Snell through its reemergence and rise to prominence, culminating in an assessment of subsequent work and what it means for the future of PHGDH.

p53 Protein-mediated regulation of phosphoglycerate dehydrogenase (PHGDH) is crucial for the apoptotic response upon serine starvation

Although p53 is frequently mutated in human cancers, about 80% of human melanomas retain wild-type p53. Here we report that PHGDH, the key metabolic enzyme that catalyzes the rate-limiting step of the serine biosynthesis pathway, is a target of p53 in human melanoma cells. p53 suppresses PHGDH expression and inhibits de novo serine biosynthesis. Notably, upon serine starvation, p53-mediated cell death is enhanced dramatically in response to Nutlin-3 treatment. Moreover, PHGDH has been found recently to be amplified frequently in human melanomas. We found that PHGDH overexpression significantly suppresses the apoptotic response, whereas RNAi-mediated knockdown of endogenous PHGDH promotes apoptosis under the same treatment. These results demonstrate an important role of p53 in regulating the serine biosynthesis pathway through suppressing PHGDH expression and reveal serine deprivation as a novel approach to sensitize p53-mediated apoptotic responses in human melanoma cells.