Stabilization of Notch1 and β-catenin in response to ER- breast cancer-specific up-regulation of PSAT1 mediates distant metastasis

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.

Nanomaterials for delivery of drugs and genes to disrupt notch signaling pathway in breast cancer

Breast cancer, marked by considerable heterogeneity and intricate molecular subgroups, poses substantial obstacles to therapy. Epithelial-mesenchymal transition (EMT) and the existence of tumor-initiating cells (TICs) facilitate treatment resistance, metastasis, and worse prognosis. The Notch signaling system has garnered significant interest for its involvement in promoting epithelial-mesenchymal transition (EMT), maintaining tumor-initiating cells (TIC), and facilitating cancer progression, especially in truculent subtypes such as triple-negative breast cancer (TNBC). Targeting the Notch system represents a promising therapeutic strategy; nevertheless, traditional inhibitors frequently encounter obstacles, including inadequate selectivity and bioavailability. Nanocarrier-based drug delivery systems provide novel therapeutic strategies to these difficulties by augmenting the targeted delivery of Notch inhibitors and enhancing therapeutic efficacy. Solid lipid nanoparticles (SLNs), polymeric nanoparticles, lipid-based nanocarriers, and micelles exhibit promise in delivering Notch inhibitors to neoplastic cells, altering the Notch signaling pathway, and surmounting drug resistance. This review examines recent breakthroughs in nanocarrier systems aimed at the Notch signaling pathway in breast cancer, highlighting the therapeutic potential of integrating nanomedicine with Notch inhibition to disrupt epithelial-mesenchymal transition (EMT), tumor-initiating cells (TICs), and metastasis, thereby enhancing clinical outcomes.

De Novo Serine Synthesis Is a Metabolic Vulnerability That Can Be Exploited to Overcome Sunitinib Resistance in Advanced Renal Cell Carcinoma

Sunitinib is an oral tyrosine kinase inhibitor used in treating advanced renal cell carcinoma (RCC) that exhibits significant efficacy but faces resistance in 30% of patients. Identifying the molecular mechanisms underlying resistance could enable the development of strategies to enhance sunitinib sensitivity. In this study, we showed that sunitinib induces a metabolic shift leading to increased serine synthesis in RCC cells. Activation of the GCN2-ATF4 stress response pathway was identified as the mechanistic link between sunitinib treatment and elevated serine production. The increased serine biosynthesis supported nucleotide synthesis and sustained cell proliferation, migration, and invasion following sunitinib treatment. Inhibiting key enzymes in the serine synthesis pathway, such as phosphoglycerate dehydrogenase and phosphoserine aminotransferase 1, enhanced the sensitivity of resistant cells to sunitinib. Beyond RCC, similar activation of serine synthesis following sunitinib treatment occurred in a variety of other cancer types, suggesting a shared adaptive response to sunitinib therapy. Together, this study identifies the de novo serine synthesis pathway as a potential target to overcome sunitinib resistance, offering insights into therapeutic strategies applicable across diverse cancer contexts. Significance: Sunitinib treatment induces metabolic reprogramming to provide essential metabolite building blocks for tumor survival, resistance, and progression by upregulating serine biosynthesis, which represents a targetable dependency to enhance therapeutic efficacy.

PSAT1 regulates hair follicle growth and stem cell behavior in cashmere goats

BACKGROUND

The Arbas Cashmere Goat from Inner Mongolia is renowned for its superior-quality cashmere, which is primarily produced by secondary hair follicles (SHFs). Secondary hair follicle stem cells (SHFSCs) are critical regulators of SHF growth and development. However, the specific regulatory mechanisms of phosphoserine aminotransferase 1 (PSAT1) in SHFSCs remain unclear. This study aimed to examine the expression pattern of the PSAT1 gene during SHF cycle transitions in cashmere goats and analyze its effects on SHFSC survival and wound healing.

RESULTS

PSAT1 expression was significantly higher in the anagen phase than in the telogen phase, and was predominantly localized to the bulge region. Functional analyses revealed that elevated PSAT1 expression inhibited SHFSC survival and delayed wound healing; on the other hand, a reduced expression promoted SHFSC survival and accelerated healing. Transcriptomic profiling further demonstrated that PSAT1 expression levels markedly altered the gene expression landscape of SHFSCs. Notably, key signaling pathways essential for hair follicle growth and development, such as Wnt/β-catenin, MAPK, and TGF-β, were significantly affected by PSAT1 modulation.

CONCLUSIONS

This study highlights PSAT1 as a critical regulator of SHFSC function in cashmere goats, affecting both cellular survival and regenerative capacity. Through its modulation of multiple signaling pathways, PSAT1 plays a pivotal role in the SHF cycle and may serve as a potential molecular target for improving cashmere fiber production.

The role and research progress of serine metabolism in tumor cells

Serine is crucial for tumor initiation, progression, and adaptive immunity. Metabolic pathways for serine synthesis, acquisition, and utilization in tumors and tumor-associated cells are influenced by various physiological factors and the tumor microenvironment, leading to metabolic reprogramming and amplification. Excessive serine metabolism promotes abnormal macromolecule biosynthesis, mitochondrial dysfunction, and epigenetic modifications, driving malignant transformation, proliferation, metastasis, immune suppression, and drug resistance in tumor cells. Restricting dietary serine intake or reducing the expression of serine synthetic enzymes can effectively slow tumor growth and extend patient survival. Consequently, targeting serine metabolism has emerged as a novel and promising research focus in cancer research. This paper reviews serine metabolic pathways and their roles in tumor development. It summarizes the influencing factors of serine metabolism. The article explores the significance of serine synthesis and metabolizing enzymes, along with related biomarkers, in tumor diagnosis and treatment, providing new insights for developing targeted therapies that modulate serine metabolism in cancer.

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.

PSAT1 Promotes Metastasis via p-AKT/SP1/ITGA2 Axis in Estrogen Receptor-Negative Breast Cancer Cell

BACKGROUND

Accumulating evidence indicates that PSAT1 not only reprogrammed metabolic function but also exhibits "moonlighting" functions in promoting tumor malignancy. However, the underlying molecular mechanisms of PSAT1 promoting ER-negative breast cancer cell migration need further investigation.

METHODS

Briefly, the PSAT1 and ITGA2 expression in cells and tissues was detected using qRT-PCR, immunofluorescence staining and western blot assay. The effect of PSAT1 and ITGA2 was verified both in vitro and in vivo. RNA-seq analysis explored a series of differently expressed genes. The regulation between SP1 and ITGA2 was investigated by ChIP analysis.

RESULTS

We reported PSAT1 was highly expressed in ER-breast cancer tissues and tumor cells and positively correlated with metastasis. Moreover, RNA-seq analysis explored a series of differently expressed genes, including ITGA2, in PSAT1 overexpressed cells. Mechanistically, PSAT1 facilitated breast cancer metastasis via the p-AKT/SP1/ITGA2 axis. We further elucidated that PSAT1 promoted the entry of SP1 into the nucleus through the upregulation of p-AKT and confirmed ITGA2 is a target of SP1. In addition, enhanced cell migration was remarkably reversed by ITGA2 depletion or p-AKT inhibitor treatment.

CONCLUSION

This study clarified the mechanism of PSAT1 in promoting ER-negative breast cancer metastasis, which may provide mechanistic clues for attenuating breast cancer metastasis.

PSAT1 mediated EMT of colorectal cancer cells by regulating Pl3K/AKT signaling pathway

Background: The metastasis of colorectal cancer (CRC) is one of the significant barriers impeding its treated consequence and bring about high mortality, less surgical resection rate and poor prognosis of CRC patients. PSAT1 is an enzyme involved in serine biosynthesis. The studies showed that PSAT1 plays the part of a crucial character in the regulation of tumor metastasis. And Epithelial-Mesenchymal Transition (EMT) is a process of cell reprogramming in which epithelialcells obtain mesenchymal phenotypes. It is a crucial course in promoting cell metastasis and the progression of malignant tumors. The relationship between PSAT1 and EMT in colorectal cancer, as well as the underlying molecular mechanisms, remains enigmatic and warrants thorough exploration. These findings suggest that PSAT1 may serve as a promising therapeutic target for mitigating colorectal cancer metastasis and holds the potential to emerge as a valuable prognostic biomarker in forthcoming research endeavors. Materials and Methods: Utilizing TCGA dataset in conjunction with clinical CRC specimens, our initial focus was directed towards an in-depth examination of PSAT1 expression within CRC, specifically exploring its potential correlation with the adverse prognostic outcomes experienced by patients. Furthermore, we conducted a comprehensive investigation into the regulatory influence exerted by PSAT1 on CRC through the utilization of siRNA knockdown techniques. In the realm of in vitro experimentation, we meticulously evaluated the impact of PSAT1 on various facets of CRC progression, including cell migration, invasion, proliferation, and colony formation. In order to elucidate the intricate effects in question, we adopted a multifaceted methodology that encompassed a range of assays and analyses. These included wound healing assays, transwell assays, utilization of the Cell Counting Kit-8 (CCK-8) assay, and colony formation assays. By employing this diverse array of investigative techniques, we were able to achieve a comprehensive comprehension of the multifaceted role that PSAT1 plays in the pathogenesis of colorectal cancer. This multifarious analysis greatly contributed to our in-depth understanding of the complex mechanisms at play in colorectal cancer pathogenesis. Using WB and PCR experiments, we found that PSAT1 has a role in regulating EMT development in CRC.In terms of mechanism, we found that PSAT1 affected EMT by Regulating Pl3K/AKT Signaling Pathway. Results: Our investigation revealed a noteworthy down-regulation of PSAT1 expression in CRC specimens. Importantly, this down-regulation exhibited a significant positive correlation with the unfavorable prognosis of patients afflicted with CRC. Functionally, our study showcased that the siRNA-mediated knockdown of PSAT1 markedly enhanced various key aspects of CRC pathogenesis in an in vitro setting. Specifically, this included a substantial promotion of CRC cell migration, invasion, proliferation, and colony formation. Moreover, the silencing of PSAT1 also demonstrated a substantial promotion of the EMT process. Intriguingly, our research unveiled a hitherto unexplored mechanism underlying the regulatory role of PSAT1 in CRC and EMT. We have established, for the first time, that PSAT1 exerts its influence by modulating the activation of the PI3K/AKT Signaling Pathway. This mechanistic insight provides a valuable contribution to the understanding of the molecular underpinnings of CRC progression and EMT induction mediated by PSAT1. Conclusions: In unison, our research findings shed light on the previously uncharted and significant role of the PSAT1/PI3K/AKT axis in the initiation of the EMT process in CRC. Furthermore, our discoveries introduce a novel biomarker with potential implications for the clinical diagnosis and treatment of CRC.

Upregulation of serine metabolism enzyme PSAT1 predicts poor prognosis and promotes proliferation, metastasis and drug resistance of clear cell renal cell carcinoma

Serine metabolic reprogramming is known to be associated with oncogenesis and tumor development. The key metabolic enzyme PSAT1 has been identified as a potential prognostic marker for various cancers, but its role in ccRCC remains unkown. In this study, we investigated expression of PSAT1 in ccRCC using the TCGA database and clinical specimens. Our results showed that PSAT1 exhibited lower expression in tumor tissue compared to adjacent normal tissue, but its expression level increased with advancing stages and grades of ccRCC. Patients with elevated expression level of PSAT1 exhibited an unfavorable prognosis. Functional experiments have substantiated that the depletion of PSAT1 shows an effective activity in inhibiting the proliferation, migration and invasion of ccRCC cells, concurrently promoting apoptosis. RNA sequencing analysis has revealed that the attenuation of PSAT1 can diminish tumor resistance to therapeutic drugs. Furthermore, the xenograft model has indicated that the inhibition of PSAT1 can obviously impact the tumorigenic potential of ccRCC and mitigate lung metastasis. Notably, pharmacological targeting PSAT1 by Aminooxyacetic Acid (AOA) or knockdown of PSAT1 increased the susceptibility of sunitinib-resistant cells. Inhibition of PSAT1 increased the sensitivity of drug-resistant tumors to sunitinib in vivo. Collectively, our investigation identifies PSAT1 as an independent prognostic biomarker for advanced ccRCC patients and as a prospective therapeutic target.

The enzymes of serine synthesis pathway in cancer metastasis

Metastasis, the major cause of cancer mortality, requires cancer cells to reprogram their metabolism to adapt to and thrive in different environments, thereby leaving metastatic cells metabolic characteristics different from their parental cells. Mounting research has revealed that the de novo serine synthesis pathway (SSP), a glycolytic branching pathway that consumes glucose carbons for serine makeup and α-ketoglutarate generation and thus supports the proliferation, survival, and motility of cancer cells, is one such reprogrammed metabolic pathway. During different metastatic cascades, the SSP enzyme proteins or their enzymatic activity are both dynamically altered; manipulating their expression or catalytic activity could effectively prevent the progression of cancer metastasis; and the SSP enzymatic proteins could even conduce to metastasis via their nonenzymatic functions. In this article we overview the SSP dynamics during cancer metastasis and put the focuses on the regulatory role of the SSP in metastasis and the underlying mechanisms that mainly involve cellular anabolism/catabolism, redox balance, and epigenetics, aiming to provide a theoretical basis for the development of therapeutic strategies for targeting metastatic lesions.

The role of serine metabolism in lung cancer: From oncogenesis to tumor treatment

Metabolic reprogramming is an important hallmark of malignant tumors. Serine is a non-essential amino acid involved in cell proliferation. Serine metabolism, especially the de novo serine synthesis pathway, forms a metabolic network with glycolysis, folate cycle, and one-carbon metabolism, which is essential for rapidly proliferating cells. Owing to the rapid development in metabolomics, abnormal serine metabolism may serve as a biomarker for the early diagnosis and pathological typing of tumors. Targeting serine metabolism also plays an essential role in precision and personalized cancer therapy. This article is a systematic review of de novo serine biosynthesis and the link between serine and folate metabolism in tumorigenesis, particularly in lung cancer. In addition, we discuss the potential of serine metabolism to improve tumor treatment.

miRNA-195-5p/PSAT1 feedback loop in human triple-negative breast cancer cells

BACKGROUND

Substantial evidence suggests that non-coding RNAs, such as microRNAs (miRNAs), play a vital role in human cancer. Phosphoserine aminotransferase 1 (PSAT1) is a serine biosynthesis-related member of the aminotransferase family and is closely associated with worse prognosis in triple-negative breast cancer (TNBC).

OBJECTIVE

The present study elucidated the molecular mechanisms underlying PSAT1 regulation by miRNAs in TNBC.

METHODS

After collecting breast cancer and para-cancerous tissues, expression and functional testing of microRNA-195-5p (miR-195-5p) and PSAT1 were implemented both in vivo and in vitro.

RESULTS

Abnormally low miR-195-5p expression was confirmed in TNBC tissues and cells. The specific targeting effect of miR-195-5p on PSAT1 was screened. Our observations revealed that biological tumor behavior was inhibited after miR-195-5p upregulation and this inhibition could be reversed by PSAT1 overexpression both in vivo and in vitro.

CONCLUSION

Our study revealed the regulatory axis of miR-195-5p/PSAT1 in TNBC, suggesting a promising targeted therapy for clinical application.

Epigenetic regulator KDM4A activates Notch1-NICD-dependent signaling to drive tumorigenesis and metastasis in breast cancer

BACKGROUND

Altered epigenetic reprogramming and events contribute to breast cancer (Bca) progression and metastasis. How the epigenetic histone demethylases modulate breast cancer progression remains poorly defined. We aimed to elucidate the biological roles of KDM4A in driving Notch1 activation and Bca progression.

METHODS

The KDM4A expression in Bca specimens was analyzed using quantitative PCR and immunohistochemical assays. The biological roles of KDM4A were evaluated using wound-healing assays and an in vivo metastasis model. The Chromatin Immunoprecipitation (ChIP)-qPCR assay was used to determine the role of KDM4A in Notch1 regulation.

RESULTS

Here, we screened that targeting KDM4A could induce notable cell growth suppression. KDM4A is required for the growth and progression of Bca cells. High KDM4A enhances tumor migration abilities and in vivo lung metastasis. Bioinformatic analysis suggested that KDM4A was highly expressed in tumors and high KDM4A correlates with poor survival outcomes. KDM4A activates Notch1 expressions via directly binding to the promoters and demethylating H3K9me3 modifications. KDM4A inhibition reduces expressions of a list of Notch1 downstream targets, and ectopic expressions of ICN1 could restore the corresponding levels. KDM4A relies on Notch1 signaling to maintain cell growth, migration and self-renewal capacities. Lastly, we divided a panel of cell lines into KDM4A^high and KDM4A^low groups. Targeting Notch1 using specific LY3039478 could efficiently suppress cell growth and colony formation abilities of KDM4A^high Bca.

CONCLUSION

Taken together, KDM4A could drive Bca progression via triggering the activation of Notch1 pathway by decreasing H3K9me3 levels, highlighting a promising therapeutic target for Bca.