Overexpression of PSAT1 regulated by G9A sustains cell proliferation in colorectal cancer

PSAT1 regulated by STAT4 enhances the proliferation, invasion and migration of ovarian cancer cells via the PI3K/AKT pathway

Epithelial ovarian cancer, the most prevalent form of ovarian cancer, is a health concern worldwide. Phosphoserine aminotransferase 1 (PSAT1), as the rate‑limiting enzyme in serine synthesis, is key in the conversion of 3‑phosphoglycerate to serine. The present study explored the role of PSAT1 expression in epithelial ovarian tumors. Gene Expression Profiling Interactive Analysis was used for gene expression and survival analyses. The effects of PSAT1 overexpression and knockdown on invasion, migration, proliferation and cell cycle progression of ovarian cancer cell lines were investigated both in vitro and in vivo. Western blotting was conducted to assess alterations in PI3K/AKT signalling pathway proteins. Database and tissue sample data confirmed that PSAT1 was significantly upregulated in ovarian cancer. Preliminary functional investigations indicated that PSAT1 was involved in modulation of invasion and migration, demonstrating the capacity of PSAT1 to enhance expression of the PI3K/AKT signalling pathway. These findings suggested that PSAT1 served a critical role in the onset and progression of ovarian cancer, thereby offering a theoretical basis for early detection and therapeutic strategies.

PSAT1 promotes the progression of colorectal cancer by regulating Hippo-YAP/TAZ-ID1 axis via AMOT

Colorectal cancer (CRC) ranks third for morbidity and second for mortality among all digestive malignant tumors worldwide, but its pathogenesis remains not entirely clear. Bioinformatic analyses were performed to find out important biomarkers for CRC. For validation, reverse transcription-quantitative PCR, western blotting, and immunohistochemistry were performed. Then, cell transfection, gain- and loss-of-function assays, immunofluorescence, cell line RNA-sequencing and analyses, and in vivo tumorigenesis assay were also performed to further explore the mechanism. We prioritized phosphoserine aminotransferase 1 (PSAT1) as an important biomarker in CRC. PSAT1 expression was gradually up-regulated as the CRC disease progresses and may relate to poor prognosis. PSAT1 promoted the malignant behaviors of CRC cells. Although PSAT1 is an enzyme essential to serine biosynthesis, an exogenous supplement of serine did not completely rescue the malignant behaviors in PSAT1-knockdown CRC cells. Interestingly, PSAT1 inhibited the Hippo tumor-suppressor pathway by promoting the nucleus-localization of YAP/TAZ and increasing the expression of ID1 in CRC cells. Furthermore, AMOT, a vascular-related molecule that molecularly interacts with YAP/TAZ, was up-regulated upon PSAT1 knockdown in CRC cells. Knocking down AMOT partially rescued the inhibition of proliferation and the reduced nuclear localization of YAP/TAZ caused by PSAT1 knockdown in CRC cells. Moreover, PSAT1 was closely related to vascular-related pathways, in which AMOT might act as a mediator. Finally, PSAT1 promoted CRC proliferation by negatively regulating AMOT in vivo. PSAT1 could enhance the progression of colorectal cancer by regulating Hippo-YAP/TAZ-ID1 axis via AMOT, which is independent of the metabolic function of PSAT1.

The inhibitory receptor LAG3 affects NK cell IFN-γ production through glycolysis and the PSAT1/STAT1/IFNG pathway

Natural killer (NK) cells are integral to the innate immune system and crucial for antiviral defense. NK cell activation and functional state are suppressed by inhibitory receptors. Lymphocyte activation gene 3 (LAG3) is an important inhibitory receptor, but the associated signaling pathways that regulate lymphocyte function remain to be elucidated. In addition, the effect of LAG3 on NK cell function during HIV infection and its specific mechanisms are unclear. In this study, we observed that LAG3 expression by NK cells is elevated in HIV-infected individuals and inversely correlated with CD4/CD8 ratio and CD4+ T cell count. LAG3+ NK cells produce lower levels of interferon-gamma (IFN-γ), but LAG3-Fc protein significantly enhances NK cell function. The activation of LAG3 significantly inhibits IFN-γ production and Ki67 expression by NK cells. Our transcriptome sequencing and in vitro data show for the first time that LAG3 not only regulates the transcription of MYC and several glycolysis-related enzyme genes via the PI3K/AKT/mTOR signaling pathway to inhibit glycolysis in NK cells but also suppresses the STAT1/IFNG pathway by upregulating PSAT1 expression, thus limiting IFN-γ production by NK cells via these two different pathways. Overall, these results provide new insights and identify potential targets for immunotherapy of HIV infection.

IMPORTANCE

We demonstrate that lymphocyte activation gene 3 (LAG3) expression is upregulated on natural killer (NK) cells during HIV infection. LAG3 inhibits glycolysis in NK cells and also upregulates PSAT1 expression to suppress activation of the STAT1/IFNG pathway, thus restricting interferon-gamma production by NK cells. These results provide new clues to study the effects of LAG3 on the metabolism and functional exhaustion of NK cells and offer a potential target for the treatment of HIV.

Serine metabolism in tumor progression and immunotherapy

Serine plays a vital role in various metabolic processes including the synthesis of proteins and other amino acids, which are essential for the cell proliferation and growth. Cancer cells either absorb exogenous serine or produce it through the serine synthesis pathway, enabling the generation of intracellular glycine and one-carbon units, which are crucial for nucleotide biosynthesis. This metabolic process, referred to as serine-glycine-one-carbon (SGOC) metabolism, is essential for tumorigenesis and exhibits considerable complexity and clinical significance. Enzymes involved in the SGOC pathway are linked to tumor growth, metastasis, and resistance to therapies. The SGOC pathway is a vital metabolic network that facilitates cell survival and proliferation, especially in aggressive cancers. Understanding how this network is regulated is crucial for tackling tumor heterogeneity and recurrence. This review emphasizes recent advancements in understanding the roles and effects of the SGOC metabolic pathway in the context of cancer progression. Additionally, it outlines the complex influences of the SGOC metabolic pathway on the tumor microenvironment (TME), offering potential strategies to enhance cancer immunotherapy.

Current and Emerging Approaches Targeting G9a for the Treatment of Various Diseases

G9a, a histone lysine methyltransferase, is instrumental in regulating gene expression through epigenetic modifications. Its overexpression is closely linked to the progression of various human diseases, including cancers. Therefore, targeting G9a enzyme is a promising strategy for treating various diseases. Although no G9a inhibitors have yet reached clinical trials, several small molecule inhibitors have demonstrated strong preclinical efficacy. For instance, the orally available inhibitor 16 (DS79932728) shows significant potential for treating sickle cell disease, while 34 (compound 15h) has shown promising treatment of rhabdomyosarcoma. This Perspective summarizes the protein structure and biological functions of G9a, along with its association with various diseases. We highlight the design strategies, structure-activity relationships, and biological activity assessments of G9a inhibitors. Additionally, we discuss the unique advantages of the mechanisms of novel G9a inhibitors, offering insights for the future development of more effective drugs targeting G9a.

Bioinformatics analysis of PSAT1 loss identifies downstream pathways regulated in EGFR mutant NSCLC and a selective gene signature for predicting the risk of relapse

The majority of malignant tumors exhibit an altered metabolic phenotype that ultimately provides the required energy and molecular precursors necessary for unregulated cell division. Within this, phosphoserine aminotransferase 1 (PSAT1) is involved in de novo serine biosynthesis and its activity promotes various biochemical processes, including one-carbon metabolism. It also directly generates α-ketoglutarate (α-KG), a Kreb cycle intermediate and epigenetic-regulating metabolite. Prior studies examining PSAT1 depletion have identified individual affected downstream pathways, such as GSK3β and E2F, in several cancer types, including non-small-cell lung cancer (NSCLC). However, global gene expression examination in response to PSAT1 loss, particularly in EGFR mutant NSCLC, has not been unexplored. Transcriptional profiling of EGFR mutant NSCLC cells with or without stable knock-down of PSAT1 identified differentially expressed genes (DEGs) enriched in several metabolic pathways required for cell division, including amino acid and nucleotide biosynthesis. Supplementation studies involving non-essential amino acids, nucleosides and α-KG partially restored defects in anchorage-independent growth due to the knockdown of PSAT1. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analysis identified potential impacts on actin cytoskeleton arrangement and β-catenin activity, which were rescued by PSAT1 re-expression. Finally, a comparative analysis of PSAT1 DEGs against transcripts enriched in patient EGFR mutant lung tumors identified a gene signature that is associated with overall and relapse-free survival (RFS) and was able to distinguish low or high-risk populations for RFS in early-stage EGFR mutant NSCLC. Overall, investigating genes altered by PSAT1 loss confirmed known PSAT1-regulated cellular pathways, identified a previously unknown role in the mediation of cytoskeleton arrangement in EGFR mutant NSCLC cells and allowed for the characterization of a gene signature with putative predictive potential for RFS in early-stage disease.

Identification and Validation of Serum Biomarkers to Improve Colorectal Cancer Diagnosis

BACKGROUND

The pressing need for reliable biomarkers in colorectal cancer (CRC) diagnosis and prognosis is a major global health concern. Current diagnostic methods rely heavily on invasive procedures like colonoscopy, and existing biomarkers such as Carbohydrate Antigen 19-9 (CA19-9) and Carcinoembryonic Antigen (CEA) exhibit limitations in accuracy and specificity.

AIMS

This study aims to identify and validate novel biomarkers that can enhance the early detection and diagnostic precision of CRC while overcoming the shortcomings of conventional biomarkers.

MATERIALS AND METHODS

Leveraging advancements in genomic and proteomic technologies, gene expression datasets were obtained from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA). We identified differentially expressed genes (DEGs) and conducted further analyses, including Gene Ontology (GO) enrichment and Protein-Protein Interaction (PPI) network construction. Five promising biomarkers-INHBA, MMP7, PSAT1, SLC7A5, and TGFBI-were selected based on their robust performance in Receiver Operating Characteristic (ROC) curve analysis. Serum concentrations of these biomarkers were measured in 200 CRC patients and 100 healthy controls.

RESULTS

The study revealed significantly elevated expression levels of the selected biomarkers in CRC tissues compared to normal tissues. Additionally, serum concentrations of INHBA, MMP7, PSAT1, SLC7A5, and TGFBI were notably higher in CRC patients than in healthy individuals, with Area Under the Curve (AUC) values ranging from 0.8361 to 0.9869 indicating high diagnostic accuracy. Optimal cutoff values for diagnosis ranged from 38.9 pg/mL to 280.7 pg/mL, yielding sensitivity and specificity values between 74.5% and 92.9%.

DISCUSSION

The findings underscore the potential of INHBA, MMP7, PSAT1, SLC7A5, and TGFBI as effective non-invasive biomarkers for CRC detection. Their elevated serum concentrations and robust discriminatory abilities highlight their promise in improving diagnostic accuracy and patient outcomes compared to traditional biomarkers.

CONCLUSION

The identification and validation of these novel biomarkers represent a significant advancement in CRC diagnosis and management. Further studies are required to validate their clinical applicability in larger cohorts and to elucidate their functional roles in CRC pathogenesis, ultimately enhancing diagnostic strategies and personalized treatment approaches.

Interplay between acetylation and ubiquitination controls PSAT1 protein stability in lung adenocarcinoma

Serine is essential to maintain maximal growth and proliferation of cancer cells by providing adequate intermediate metabolites and energy. Phosphoserine aminotransferase 1 (PSAT1) is a key enzyme in de novo serine synthesis. However, little is known about the mechanisms underlying PSAT1 degradation. We found that acetylation was the switch that regulated the degradation of PSAT1 in lung adenocarcinoma (LUAD). Deacetylation of PSAT1 on Lys51 by histone deacetylase 7 (HDAC7) enhanced the interaction between PSAT1 and the deubiquitinase ubiquitin-specific processing protease 14 (USP14), leading to the deubiquitination and stabilization of PSAT1; while acetylation of PSAT1 promoted its interaction with the E3 ligase ubiquitination factor E4B (UBE4B), leading to proteasomal degradation. Acetylation of PSAT1 on Lys51 regulated serine metabolism and tumor proliferation in LUAD. Thus, acetylation and ubiquitination cooperatively regulated the protein homeostasis of PSAT1. In conclusion, our study reveals a key regulatory mechanism for maintaining PSAT1 protein homeostasis in LUAD.

Prognostic Signature in Osteosarcoma Based on Amino Acid Metabolism-Associated Genes

Background: Osteosarcoma (OS) is undeniably a formidable bone malignancy characterized by a scarcity of effective treatment options. Reprogramming of amino acid (AA) metabolism has been associated with OS development. The present study was designed to identify metabolism-associated genes (MAGs) that are differentially expressed in OS and to construct a MAG-based prognostic risk signature for this disease. Methods: Expression profiles and clinicopathological data were downloaded from Gene Expression Omnibus (GEO) and UCSC Xena databases. A set of AA MAGs was obtained from the MSigDB database. Differentially expressed genes (DEGs) in GEO dataset were identified using "limma." Prognostic MAGs from UCSC Xena database were determined through univariate Cox regression and used in the prognostic signature development. This signature was validated using another dataset from GEO database. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, single sample gene set enrichment analysis, and GDSC2 analyses were performed to explore the biological functions of the MAGs. A MAG-based nomogram was established to predict 1-, 3-, and 5-year survival. Real-time quantitative polymerase chain reaction, Western blot, and immunohistochemical staining confirmed the expression of MAGs in primary OS and paired adjacent normal tissues. Results: A total of 790 DEGs and 62 prognostic MAGs were identified. A MAG-based signature was constructed based on four MAGs: PIPOX, PSMC2, SMOX, and PSAT1. The prognostic value of this signature was successfully validated, with areas under the receiver operating characteristic curves for 1-, 3-, and 5-year survival of 0.714, 0.719, and 0.715, respectively. This MAG-based signature was correlated with the infiltration of CD56dim natural killer cells and resistance to several antiangiogenic agents. The nomogram was accurate in predictions, with a C-index of 0.77. The expression of MAGs verified by experiment was consistent with the trends observed in GEO database. Conclusion: Four AA MAGs were prognostic of survival in OS patients. This MAG-based signature has the potential to offer valuable insights into the development of treatments for OS.

N6-methyladenosine modification of LATS2 promotes hepatoblastoma progression by inhibiting ferroptosis through the YAP1/ATF4/PSAT1 axis

Ferroptosis has attracted extensive interest from cancer researchers due to its substantial potential as a therapeutic target. The role of LATS2, a core component of the Hippo pathway cascade, in ferroptosis initiation in hepatoblastoma (HB) has not yet been investigated. Furthermore, the underlying mechanism of decreased LATS2 expression remains largely unknown. In the present study, we demonstrated decreased LATS2 expression in HB and that LATS2 overexpression inhibits HB cell proliferation by inducing ferroptosis. Increased LATS2 expression reduced glycine and cysteine concentrations via the ATF4/PSAT1 axis. Physical binding between YAP1/ATF4 and the PSAT1 promoter was confirmed through ChIP‒qPCR. Moreover, METTL3 was identified as the writer of the LATS2 mRNA m6A modification at a specific site in the 5' UTR. Subsequently, YTHDF2 recognizes the m6A modification site and recruits the CCR4-NOT complex, leading to its degradation by mRNA deadenylation. In summary, N6-methyladenosine modification of LATS2 facilitates its degradation. Reduced LATS2 expression promotes hepatoblastoma progression by inhibiting ferroptosis through the YAP1/ATF4/PSAT1 axis. Targeting LATS2 is a potential strategy for HB therapy.

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.

A telomere-related gene risk model for predicting prognosis and treatment response in acute myeloid leukemia

Acute myeloid leukemia (AML) is a prevalent hematological malignancy among adults. Recent studies suggest that the length of telomeres could significantly affect both the risk of developing AML and the overall survival (OS). Despite the limited focus on the prognostic value of telomere-related genes (TRGs) in AML, our study aims at addressing this gap by compiling a list of TRGs from TelNet, as well as collecting clinical information and TRGs expression data through the Gene Expression Omnibus (GEO) database. The GSE37642 dataset, sourced from GEO and based on the GPL96 platform, was divided into training and validation sets at a 6:4 ratio. Additionally, the GSE71014 dataset (based on the GPL10558 platform), GSE12417 dataset (based on the GPL96 and GPL570 platforms), and another portion of the GSE37642 dataset (based on the GPL570 platform) were designated as external testing sets. Univariate Cox regression analysis identified 96 TRGs significantly associated with OS. Subsequent Lasso-Cox stepwise regression analysis pinpointed eight TRGs (MCPH1, SLC25A6, STK19, PSAT1, KCTD15, DNMT3B, PSMD5, and TAF2) exhibiting robust predictive potential for patient survival. Both univariate and multivariate survival analyses unveiled TRG risk scores and age as independent prognostic variables. To refine the accuracy of survival prognosis, we developed both a nomogram integrating clinical parameters and a predictive risk score model based on TRGs. In subsequent investigations, associations were emphasized not solely regarding the TRG risk score and immune infiltration patterns but also concerning the response to immune-checkpoint inhibitor (ICI) therapy. In summary, the establishment of a telomere-associated genetic risk model offers a valuable tool for prognosticating AML outcomes, thereby facilitating informed treatment decisions.

Lycorine eliminates B-cell acute lymphoblastic leukemia cells by targeting PSAT1 through the serine/glycine metabolic pathway

B-cell acute lymphoblastic leukemia (B-ALL) has been confirmed as the most common malignant hematologic neoplasm among children. A novel antitumor mechanism of lycorine was elucidated in this study. As revealed by the result of this study, lycorine significantly inhibited the growth and proliferation of REH and NALM-6 and induced their apoptosis. The result of the RNA-seq analysis suggested that lycorine targeted PSAT1 of serine/glycine metabolism in B-ALL cells. As indicated by the result of the GSEA analysis, the genes enriched in the amino acid metabolic pathways were down-regulated by lycorine. As revealed by the results of ectopic expression, shRNA knockdown assays, and further liquid-phase tandem mass spectrometry (LC-MS) analysis, lycorine reduced serine/glycine metabolites by down-regulating PSAT1, further disrupting carbon metabolism and eliminating B-ALL cells. Furthermore, lycorine showed a synergistic effect with cytarabine in ALL treatments. Lastly, lycorine significantly down-regulated leukemia progression in the cell line-derived xenograft (CDX) model. In brief, this study has suggested for the first time that lycorine is a promising anti-ALL drug, and a novel amino acid metabolism-associated property of lycorine was identified.

Depletion of G9A attenuates imiquimod-induced psoriatic dermatitis via targeting EDAR-NF-κB signaling in keratinocyte

Psoriasis is a common and recurrent inflammatory skin disease characterized by inflammatory cells infiltration of the dermis and excessive proliferation, reduced apoptosis, and abnormal keratosis of the epidermis. In this study, we found that G9A, an important methyltransferase that mainly mediates the mono-methylation (me1) and di-methylation (me2) of histone 3 lysine 9 (H3K9), is highly expressed in lesions of patients with psoriasis and imiquimod (IMQ)-induced psoriasis-like mouse model. Previous studies have shown that G9A is involved in the pathogenesis of various tumors by regulating apoptosis, proliferation, differentiation, and invasion. However, the role of G9A in skin inflammatory diseases such as psoriasis remains unclear. Our data so far suggest that topical administration of G9A inhibitor BIX01294 as well as keratinocyte-specific deletion of G9A greatly alleviated IMQ-induced psoriatic alterations in mice for the first time. Mechanistically, the loss function of G9A causes the downregulation of Ectodysplasin A receptor (EDAR), consequently inhibiting the activation of NF-κB pathway, resulting in impaired proliferation and increased apoptosis of keratinocytes, therefore ameliorating the psoriatic dermatitis induced by IMQ. In total, we show that inhibition of G9A improves psoriatic-like dermatitis mainly by regulating cell proliferation and apoptosis rather than inflammatory processes, and that this molecule may be considered as a potential therapeutic target for keratinocyte hyperproliferative diseases such as psoriasis.

Downregulation of PSAT1 inhibits cell proliferation and migration in uterine corpus endometrial carcinoma

Phosphoserine aminotransferase 1 (PSAT1) has been associated with the occurrence and development of various carcinomas; however, its function in uterine corpus endometrial carcinoma (UCEC) is unknown. We aimed to explore the relationship between PSAT1 and UCEC using The Cancer Genome Atlas database and functional experiments. PSAT1 expression levels in UCEC were employed using the paired sample t-test, Wilcoxon rank-sum test, the Clinical Proteomic Tumor Analysis Consortium database, and the Human Protein Atlas database, while survival curves were constructed using the Kaplan-Meier plotter. We performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis to explore the possible functions and related pathways of PSAT1. Furthermore, single-sample gene set enrichment analysis was performed to detect the relationship between PSAT1 and tumor immune infiltration. StarBase and quantitative PCR were used to predict and verify the interactions between miRNAs and PSAT1. The Cell Counting Kit-8, EdU assay, clone formation assay, western blotting and flow cytometry were used to evaluate cell proliferation. Finally, Transwell and Wound healing assays were used to assess cell invasion and migration. Our study found that PSAT1 was significantly overexpressed in UCEC, and this high expression was associated with a worse prognosis. A high level of PSAT1 expression was associated with a late clinical stage and, histological type. In addition, the results of GO and KEGG enrichment analysis showed that PSAT1 was mainly involved in the regulation of cell growth, immune system and cell cycle in UCEC. In addition, PSAT1 expression was positively correlated with Th2 cells and negatively correlated with Th17 cells. Furthermore, we also found that miR-195-5P negatively regulated the expression of PSAT1 in UCEC. Finally, the knockdown of PSAT1 resulted in the inhibition of cell proliferation, migration, and invasion in vitro. Overall, PSAT1 was identified as a potential target for the diagnosis and immunotherapy of UCEC.

Targeting PSAT1 to mitigate metastasis in tumors with p53-72Pro variant

The single-nucleotide polymorphism (SNP) of p53, in particular the codon 72 variants, has recently been implicated as a critical regulator in tumor progression. However, the underlying mechanism remains elusive. Here we found that cancer cells carrying codon 72-Pro variant of p53 showed impaired metastatic potential upon serine supplementation. Proteome-wide mapping of p53-interacting proteins uncovered a specific interaction of the codon 72 proline variant (but not p53^72R) with phosphoserine aminotransferase 1 (PSAT1). Interestingly, p53^72P-PSAT1 interaction resulted in dissociation of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) that otherwise bound to p53^72P, leading to subsequent nuclear translocation of PGC-1α and activation of oxidative phosphorylation (OXPHOS) and tricarboxylic acid (TCA) cycle. Depletion of PSAT1 restored p53^72P-PGC-1α interaction and impeded the OXPHOS and TCA function, resulting in mitochondrial dysfunction and metastasis suppression. Notably, pharmacological targeting the PSAT1-p53^72P interaction by aminooxyacetic acid (AOA) crippled the growth of liver cancer cells carrying the p53^72P variant in both in vitro and patient-derived xenograft models. Moreover, AOA plus regorafenib, an FDA-proved drug for hepatocellular carcinoma and colorectal cancer, achieved a better anti-tumor effect on tumors carrying the p53^72P variant. Therefore, our findings identified a gain of function of the p53^72P variant on mitochondrial function and provided a promising precision strategy to treat tumors vulnerable to p53^72P-PSAT1 perturbation.

Metabolic reprogramming in colorectal cancer: regulatory networks and therapy

With high prevalence and mortality, together with metabolic reprogramming, colorectal cancer is a leading cause of cancer-related death. Metabolic reprogramming gives tumors the capacity for long-term cell proliferation, making it a distinguishing feature of cancer. Energy and intermediate metabolites produced by metabolic reprogramming fuel the rapid growth of cancer cells. Aberrant metabolic enzyme-mediated tumor metabolism is regulated at multiple levels. Notably, tumor metabolism is affected by nutrient levels, cell interactions, and transcriptional and posttranscriptional regulation. Understanding the crosstalk between metabolic enzymes and colorectal carcinogenesis factors is particularly important to advance research for targeted cancer therapy strategies via the investigation into the aberrant regulation of metabolic pathways. Hence, the abnormal roles and regulation of metabolic enzymes in recent years are reviewed in this paper, which provides an overview of targeted inhibitors for targeting metabolic enzymes in colorectal cancer that have been identified through tumor research or clinical trials.

An integrated pan-cancer analysis of PSAT1: A potential biomarker for survival and immunotherapy

Phosphoserine aminotransferase 1 (PSAT1) may be an oncogene that plays an important role in various cancer types. However, there are still many gaps in the expression of PSAT1 gene and its biological impact in different types of tumors. Here, we performed an integrated pan-cancer analysis to explore the potential molecular mechanisms of PSAT1 in cancers. We found that most human tumors express higher levels of PSAT1 than normal tissues, and that higher PSAT1 expression is associated with worse prognosis in Lung adenocarcinoma (LUAD), Pan-kidney cohort (KIPAN) and breast invasive carcinoma (BRCA), etc. In BRCA cases, the prognosis of patients with altered PSAT1 was worse than that of patients without alteration. In addition, PSAT1 hypermethylation is associated with T cell dysfunction and shortened survival time in BRCA. The Gene Set Enrichment Analysis (GSEA) analysis showed that PSAT1 can be enriched into the classic signaling pathways of cancer such as mTORC1 signaling, MYC targets and JAK STAT3. Further analysis demonstrated that PSAT1 was enriched in immune related signaling pathways in LUAD and BRCA. The results of immunoassay showed that PSAT1 was associated with immune cell infiltration in multiple cancer species. Furthermore, expression of PSAT1 was correlated with both tumor mutational burden (TMB) and microsatellite instability (MSI) in BRCA. Additionally, a remarkable correlation was found between PSAT1 expression and TMB in LUAD, and the expression of PSAT1 was negatively correlated with the Tumor Immune Dysfunction and Exclusion (TIDE) value, suggesting a good effect of immunotherapy. Together, these data suggest that PSAT1 expression is associated with the clinical prognosis, DNA methylation, gene mutations, and immune cell infiltration, contributing to clarify the role of PSAT1 in tumorigenesis from a variety of perspectives. What’s more, PSAT1 may be a new biomarker for survival and predicting the efficacy of immunotherapy for LUAD and BRCA.

Emerging role of G9a in cancer stemness and promises as a therapeutic target

The histone methyltransferase G9a is well-documented for its implication in neoplastic growth. However, recent investigations have demonstrated a key involvement of this chromatin writer in maintaining the self-renewal and tumor-initiating capacities of cancer stem cells (CSCs). Direct inhibition of G9a’s catalytic activity was reported as a promising therapeutic target in multiple preclinical studies. Yet, none of the available pharmacological inhibitors of G9a activity have shown success at the early stages of clinical testing. Here, we discuss central findings of oncogenic expression and activation of G9a in CSCs from different origins, as well as the impact of the suppression of G9a histone methyltransferase activity in such contexts. We will explore the challenges posed by direct and systemic inhibition of G9a activity in the perspective of clinical translation of documented small molecules. Finally, we will discuss recent advances in drug discovery as viable strategies to develop context-specific drugs, selectively targeting G9a in CSC populations.

Research progress of dual inhibitors targeting crosstalk between histone epigenetic modulators for cancer therapy

Abnormal epigenetics is a critical hallmark of human cancers. Anticancer drug discovery directed at histone epigenetic modulators has gained impressive advances with six drugs available for cancer therapy and numerous other candidates undergoing clinical trials. However, limited therapeutic profile, drug resistance, narrow safety margin, and dose-limiting toxicities pose intractable challenges for their clinical utility. Because histone epigenetic modulators undergo intricate crosstalk and act cooperatively to shape an aberrant epigenetic profile, co-targeting histone epigenetic modulators with a different mechanism of action has rapidly emerged as an attractive strategy to overcome the limitations faced by the single-target epigenetic inhibitors. In this review, we summarize in detail the crosstalk of histone epigenetic modulators in regulating gene transcription and the progress of dual epigenetic inhibitors targeting this crosstalk.

LncRNA MEG8 promotes NSCLC progression by modulating the miR-15a-5p-miR-15b-5p/PSAT1 axis

BACKGROUND

Non-small cell lung cancer (NSCLC) is the most common tumor with severe morbidity and high mortality. Long non-coding RNAs (lncRNAs) as crucial regulators participate in multiple cancer progressions. However, the role of lncRNA MEG8 in the development of NSCLC remains unclear. Here, we aimed to investigate the effect of lncRNA MEG8 on the progression of NSCLC and the underlying mechanism.

METHODS

Cell proliferation was analyzed by EdU assays. The impacts of lncRNA MEG8, miR-15a-5p, and miR-15b-5p on cell invasion and migration of NSCLC were assessed by transwell assay. The luciferase reporter gene assay was performed using the Dual-luciferase Reporter Assay System. The effect of lncRNA MEG8, miR-15a-5p, and miR-15b-5p on tumor growth was evaluated in nude mice of Balb/c in vivo.

RESULTS

We revealed that the expression levels of MEG8 were elevated in the NSCLC patient tissues compared to that in adjacent normal tissues. The expression of MEG8 was negatively relative to that of miR-15a-5p and miR-15b-5p in the NSCLC patient tissues. The expression of MEG8 was upregulated, while miR-15a-5p and miR-15b-5p were downregulated in NSCLC cell lines. The depletion of MEG8 inhibited NSCLC cell proliferation, migration, and invasion in vitro. MEG8 contributed to NSCLC progression by targeting miR-15a-5p/miR-15b-5p in vitro. LncRNA MEG8 contributes to tumor growth of NSCLC via the miR-15a/b-5p/PSAT1 axis in vivo. Thus, we concluded that lncRNA MEG8 promotes NSCLC progression by modulating the miR-15a/b-5p/PSAT1 axis.

CONCLUSIONS

Our findings demonstrated that lncRNA MEG8 plays a critical role in NSCLC development. LncRNA MEG8, miR-15a-5p, miR-15b-5p, and PSAT1 may serve as potential targets for NSCLC therapy.

G9a controls pluripotent-like identity and tumor-initiating function in human colorectal cancer

Colorectal tumors are hierarchically organized and governed by populations of self-renewing cancer stem cells, representing one of the deadliest types of cancers worldwide. Emergence of cancer stemness phenotype depends on epigenetic reprogramming, associated with profound transcriptional changes. As described for pluripotent reprogramming, epigenetic modifiers play a key role in cancer stem cells by establishing embryonic stem-like transcriptional programs, thus impacting the balance between self-renewal and differentiation. We identified overexpression of histone methyltransferase G9a as a risk factor for colorectal cancer, associated with shorter relapse-free survival. Moreover, using human transformed pluripotent cells as a surrogate model for cancer stem cells, we observed that G9a activity is essential for the maintenance of embryonic-like transcriptional signature promoting self-renewal, tumorigenicity, and undifferentiated state. Such a role was also applicable to colorectal cancer, where inhibitors of G9a histone methyltransferase function induced intestinal differentiation while restricting tumor-initiating activity in patient-derived colorectal tumor samples. Finally, by integrating transcriptome profiling with G9a/H3K9me2 loci co-occupancy, we identified the canonical Wnt pathway, epithelial-to-mesenchyme transition, and extracellular matrix organization as potential targets of such a chromatin regulation mechanism in colorectal cancer stem cells. Overall, our findings provide novel insights on the role of G9a as a driver of cancer stem cell phenotype, promoting self-renewal, tumorigenicity, and undifferentiated state.

Colitis-induced IL11 promotes colon carcinogenesis

Colitis increases the risk of colorectal cancer; however, the mechanism of the association between colitis and cancer remains largely unknown. To identify colitis-associated cancer promoting factors, we investigated gene expression changes caused by dextran sulfate sodium (DSS)-induced colitis in mice. By analyzing gene expression profiles, we found that IL11 was upregulated in DSS-induced colitis tissue and 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP)/DSS-induced colon tumours in mice as well as in human colorectal cancer. By characterizing the activation/phosphorylation of STAT3 (pSTAT3), we found that pSTAT3 was induced transiently in colitis, but maintained at higher levels from hyper-proliferative dysplastic lesions to tumours. Using the IL11 receptor (IL11Rα1) knockout mice, we found that pSTAT3 in the newly regenerated crypt epithelial cells in colitis is abolished in IL11Rα1+/- and -/- mice, suggesting that colitis-induced IL11 activates STAT3 in colon crypt epithelial cells. Moreover, colitis-promoted colon carcinogenesis was significantly reduced in IL11Rα1+/- and -/- mice. To determine the roles of the IL11 in colitis, we found that the inhibition of IL11 signalling by recombinant IL11 antagonist mutein during colitis was sufficient to attenuate colitis-promoted carcinogenesis. Together, our results demonstrated that colitis-induced IL11 plays critical roles in creating cancer promoting microenvironment to facilitate the development of colon cancer from dormant premalignant cells.

G9a Is SETting the Stage for Colorectal Oncogenesis

Recently, Kato et al. reported recurrent activating mutations in the SET domain of histone methyltransferase G9a, driving an oncogenic cascade in melanoma. The authors also reported correlations between G9a expression and the regulation of the canonical WNT pathway. Although we could not observe such mutations in human colorectal adenocarcinoma, newly reported findings are of high relevance to colorectal cancer, as WNT target gene signatures were closely associated with G9a expression. Here, we put into perspective such new results on G9a expression in colorectal cancers and the potential relationship with tumor heterogeneity and acquisition of neoplastic stemness.