BCATc modulates crosstalk between the PI3K/Akt and the Ras/ERK pathway regulating proliferation in triple negative breast cancer

Rational Design of Stapled Covalent Peptide Modifiers of Oncoprotein E6 from Human Papillomavirus

Human Papillomavirus (HPV) is linked to multiple cancers, most significantly cervical cancer, for which HPV infection is associated with nearly all cases. Essential to the oncogenesis of HPV is the function of the viral protein E6 and its role in degrading the cell cycle regulator p53. Degradation of p53, and the resultant loss of cell cycle control, is mediated by E6 recruitment of the E3 ubiquitin ligase E6AP and subsequent ubiquitination of p53. Here, we report the design of a stapled peptide that mimics the LxxLL α-helical domain of E6AP to bind and covalently label a cysteine residue specific to HPV-16 E6. Several acrylamide- and haloacetamide-based warheads were evaluated for reactivity and specificity, and a panel of hydrocarbon-stapled peptides was evaluated for enhanced binding affinity and increased proteolytic stability. Structure-based modeling was used to rationalize the observed trends in the reactivity of the warheads and the impact of the hydrocarbon staple position on the binding affinity of the stapled peptides. The development of a proteolytically stable and reactive peptide represents a new class of peptide-based inhibitors of protein-protein interactions with a potential therapeutic value toward HPV-derived cancers.

ASF1B promotes gastric cancer progression by modulating H2AC20 and activating PI3K/AKT and ERK1/2 pathways

Background

Gastric cancer (GC) ranks among the most prevalent malignant neoplasms globally and is associated with a significant mortality rate. Despite the availability of various therapeutic interventions for GC, the overall prognosis for this disease remains unfavorable. This can be attributed to several factors, including delayed diagnosis and the inherent heterogeneity of the tumors. With the continuous enrichment of treatment methods, GC has entered an era of comprehensive treatment oriented toward precision and standardization.

Methods

Through the application of bioinformatics and assessments of tissue microarrays, this study has selected the histone chaperone Anti-Silencing Function 1B (ASF1B) for detailed analysis, including clinical specimens. We then constructed ASF1B knockout and overexpression cell lines, and conducted biological function tests on this basis, validated at mouse and organoid levels. Additionally, human immunereconstitution was performed in NOD-PrkdcscidIl2rgem1/Smoc (NSG) mice, followed by flow cytometry analysis of mouse blood. Mechanically, protein-protein interaction analyses were conducted utilizing Immunoprecipitation-Mass Spectrometry (IP-MS) and Tandem mass tagging (TMT) methodologies to identify protein clusters.

Results

The analysis demonstrated that ASF1B is significantly upregulated in GC tissues and correlates with unfavorable prognostic outcomes. Biological function tests provided that ASF1B contributes to tumor cell proliferation, colony formation, invasion and migration, and plays an important role in the progression of GC in vivo. These findings were validated at both the mouse and organoid levels. Additionally, we observed that ASF1B is involved in the tumor microenvironment, where ASF1B knockdown increases CD8+ T cell infiltration, indicating a negative correlation with immune activation. Mechanically, our investigation revealed that ASF1B emerged as a promoter of GC progression by downregulating H2A clustered histone 20 (H2AC20), thereby influencing the activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) and extracellular regulated protein kinases (ERK)1/2 signaling pathways.

Conclusion

ASF1B, recognized as an oncogene, contributes to the initiation and progression of tumors, positioning it as a prospective target for therapeutic intervention in GC.

Steroidal saponins: Natural compounds with the potential to reverse tumor drug resistance (Review)

Steroidal saponins are a type of natural product that have been widely used in Chinese herbal medicine, with a variety of pharmacological activities, such as antitumor, anti-inflammatory and anti-bacterial effects. Cancer has become a growing global health problem, and drug therapy is currently the most important clinical antitumor treatment. However, drug resistance is a major obstacle to the effectiveness of chemotherapy, resulting in >90% of deaths of patients with cancer receiving conventional chemotherapy. It has been found that steroidal saponins may exert an effect on the reversal of drug resistance in tumor cells by regulating apoptosis, autophagy, epithelial-mesenchymal transition and drug efflux through multiple related signaling pathways. The present study reviews the role and mechanism of steroidal saponins in the treatment of tumor drug resistance, aiming to provide a scientific basis and research ideas for the future development and clinical application of natural steroidal saponins.

Tumor microenvironment-like conditions alter pancreatic cancer cell metabolism and behavior

The tumor microenvironment is complex and dynamic, characterized by poor vascularization, limited nutrient availability, hypoxia, and an acidic pH. This environment plays a critical role in driving cancer progression. However, standard cell culture conditions used to study cancer cell biology in vitro fail to replicate the in vivo environment of tumors. Recently, "physiological" cell culture media that closely resemble human plasma have been developed (e.g., Plasmax, HPLM), along with more frequent adoption of physiological oxygen conditions (1%-8% O2). Nonetheless, further refinement of tumor-specific culture conditions may be needed. In this study, we describe the development of a tumor microenvironment medium (TMEM) based on murine pancreatic ductal adenocarcinoma (PDAC) tumor interstitial fluid. Using RNA-sequencing, we show that murine PDAC cells (KPCY) cultured in tumor-like conditions (TMEM, pH 7.0, 1.5% O2) exhibit profound differences in gene expression compared with plasma-like conditions (mouse plasma medium, pH 7.4, 5% O2). Specifically, the expression of genes and pathways associated with cell migration, biosynthesis, angiogenesis, and epithelial-to-mesenchymal transition were altered, suggesting tumor-like conditions promote metastatic phenotypes and metabolic remodeling. Using functional assays to validate RNA-seq data, we confirmed increased motility at 1.5% O2/TMEM, despite reduced cell proliferation. Moreover, a hallmark shift to glycolytic metabolism was identified via measurement of glucose uptake/lactate production and mitochondrial respiration. Taken together, these findings demonstrate that growth in 1.5% O2/TMEM alters several biological responses in ways relevant to cancer biology, and more closely models hallmark cancerous phenotypes in culture. This highlights the importance of establishing tumor microenvironment-like conditions in standard cancer research. NEW & NOTEWORTHY Standard cell culture conditions do not replicate the complex tumor microenvironment experienced by cells in vivo. Although currently available plasma-like media are superior to traditional supraphysiological media, they fail to model tumor-like conditions. Using RNA-seq analysis and functional metabolic and migratory assays, we show that tumor microenvironment medium (TMEM), used with representative tumor hypoxia, better models cancerous phenotypes in culture. This emphasizes the critical importance of accurately modeling the tumor microenvironment in cancer research.

Macrophage extracellular traps promote tumor-like biologic behaviors of fibroblast-like synoviocytes through cGAS-mediated PI3K/Akt signaling pathway in patients with rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disease characterized by synovium hyperplasia and bone destruction. Macrophage extracellular traps are released from macrophages under various stimuli and may generate stable autoantigen-DNA complexes, as well as aggravate autoantibody generation and autoimmune responses. We aimed to investigate the role of macrophage extracellular traps on the biologic behaviors of rheumatoid arthritis fibroblast-like synoviocytes. Synovial tissues and fibroblast-like synoviocytes were obtained from patients with rheumatoid arthritis. Extracellular traps in synovium and synovial fluids were detected by immunofluorescence, immunohistochemistry, and SYTOX Green staining. Cell viability, migration, invasion, and cytokine expression of rheumatoid arthritis fibroblast-like synoviocytes were assessed by CCK-8, wound-healing assay, Transwell assays, and quantitative real-time polymerase chain reaction, respectively. RNA sequencing analysis was performed to explore the underlying mechanism, and Western blot was used to validate the active signaling pathways. We found that extracellular trap formation was abundant in rheumatoid arthritis and positively correlated to anti-CCP. Rheumatoid arthritis fibroblast-like synoviocytes stimulated with purified macrophage extracellular traps demonstrated the obvious promotion in tumor-like biologic behaviors. The DNA sensor cGAS in rheumatoid arthritis fibroblast-like synoviocytes was activated after macrophage extracellular trap stimuli. RNA sequencing revealed that differential genes were significantly enriched in the PI3K/Akt signaling pathway, and cGAS inhibitor RU.521 effectively reversed the promotion of tumor-like biologic behaviors in macrophage extracellular trap-treated rheumatoid arthritis fibroblast-like synoviocytes and downregulated the PI3K/Akt activation. In summary, our study demonstrates that macrophage extracellular traps promote the pathogenically biological behaviors of rheumatoid arthritis fibroblast-like synoviocytes through cGAS-mediated activation of the PI3K/Akt signaling pathway. These findings provide a novel insight into the pathogenesis of rheumatoid arthritis and the mechanisms of macrophages in modulating rheumatoid arthritis fibroblast-like synoviocyte tumor-like behaviors.

Amino acid metabolism in health and disease

Amino acids are the building blocks of protein synthesis. They are structural elements and energy sources of cells necessary for normal cell growth, differentiation and function. Amino acid metabolism disorders have been linked with a number of pathological conditions, including metabolic diseases, cardiovascular diseases, immune diseases, and cancer. In the case of tumors, alterations in amino acid metabolism can be used not only as clinical indicators of cancer progression but also as therapeutic strategies. Since the growth and development of tumors depend on the intake of foreign amino acids, more and more studies have targeted the metabolism of tumor-related amino acids to selectively kill tumor cells. Furthermore, immune-related studies have confirmed that amino acid metabolism regulates the function of effector T cells and regulatory T cells, affecting the function of immune cells. Therefore, studying amino acid metabolism associated with disease and identifying targets in amino acid metabolic pathways may be helpful for disease treatment. This article mainly focuses on the research of amino acid metabolism in tumor-oriented diseases, and reviews the research and clinical research progress of metabolic diseases, cardiovascular diseases and immune-related diseases related to amino acid metabolism, in order to provide theoretical basis for targeted therapy of amino acid metabolism.

PI3K/AKT/mTOR signaling transduction pathway and targeted therapies in cancer

The PI3K/AKT/mTOR (PAM) signaling pathway is a highly conserved signal transduction network in eukaryotic cells that promotes cell survival, cell growth, and cell cycle progression. Growth factor signalling to transcription factors in the PAM axis is highly regulated by multiple cross-interactions with several other signaling pathways, and dysregulation of signal transduction can predispose to cancer development. The PAM axis is the most frequently activated signaling pathway in human cancer and is often implicated in resistance to anticancer therapies. Dysfunction of components of this pathway such as hyperactivity of PI3K, loss of function of PTEN, and gain-of-function of AKT, are notorious drivers of treatment resistance and disease progression in cancer. In this review we highlight the major dysregulations in the PAM signaling pathway in cancer, and discuss the results of PI3K, AKT and mTOR inhibitors as monotherapy and in co-administation with other antineoplastic agents in clinical trials as a strategy for overcoming treatment resistance. Finally, the major mechanisms of resistance to PAM signaling targeted therapies, including PAM signaling in immunology and immunotherapies are also discussed.

BCAT1, as a prognostic factor for HCC, can promote the development of liver cancer through activation of the AKT signaling pathway and EMT

More and more studies have shown that Branched chain amino acid transaminase 1 (BCAT1) is involved in the occurrence and development of a variety of tumors. However, the mechanism of its occurrence and development in hepatocellular carcinoma (HCC) remains unclear. Here, we demonstrated the relationship between BCAT1 and AKT signaling pathway, as well as EMT, and the clinical significance of BCAT1 by using BCAT1 expression in 5 cell lines and 113 liver cancer and non-liver cancer tissue samples. The results showed that the expression of AKT was positively correlated with BCAT1 in HCC tissues, and BCAT1 could promote the progression of HCC cells through the AKT signaling pathway. Clinical analysis and Bioinformatics technology analysis revealed that BCAT1 was correlated with poor prognosis, and BCAT1 expression in the HCC tissues was evidently correlated with tumor number, vascular invasion, Edmondson grade and TNM stage (P < 0.05). In vitro studies showed that BCAT1 increased the invasion and migration of in MHCC-97H cells a d Huh7 cells. By inhibiting the expression of the BCAT1 gene, we detected the corresponding changes in the expression levels of Twist, E-cadherin and Vimentin, confirming that BCAT1 may promote the invasion and migration of HCC cells through epithelial-mesenchymal transformation (EMT). Overall, BCAT1 can activate AKT signaling pathway and EMT to promote the development and metastasis of HCC cells. this study may provide new ideas and directions for cancer diagnosis and treatment.

The mechanism of branched-chain amino acid transferases in different diseases: Research progress and future prospects

It is well known that the enzyme catalyzes the first step of branched-chain amino acid (BCAA) catabolism is branched-chain amino transferase (BCAT), which is involved in the synthesis and degradation of leucine, isoleucine and valine. There are two main subtypes of human branched chain amino transferase (hBCAT), including cytoplasmic BCAT (BCAT1) and mitochondrial BCAT (BCAT2). In recent years, the role of BCAT in tumors has attracted the attention of scientists, and there have been continuous research reports that BCAT plays a role in the tumor, Alzheimer's disease, myeloid leukaemia and other diseases. It plays a significant role in the growth and development of diseases, and new discoveries about this gene in some diseases are made every year. BCAT usually promotes cancer proliferation and invasion by activating the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin pathway and activating Wnt/β-catenin signal transduction. This article reviews the role and mechanism of BCAT in different diseases, as well as the recent biomedical research progress. This review aims to make a comprehensive summary of the role and mechanism of BCAT in different diseases and to provide new research ideas for the treatment, prognosis and prevention of certain diseases.

The Emerging Role of Branched-Chain Amino Acids in Liver Diseases

Chronic liver diseases pose a substantial health burden worldwide, with approximately two million deaths each year. Branched-chain amino acids (BCAAs)-valine, leucine, and isoleucine-are a group of essential amino acids that are essential for human health. Despite the necessity of a dietary intake of BCAA, emerging data indicate the undeniable correlation between elevated circulating BCAA levels and chronic liver diseases, including non-alcoholic fatty liver diseases (NAFLD), cirrhosis, and hepatocellular carcinoma (HCC). Moreover, circulatory BCAAs were positively associated with a higher cholesterol level, liver fat content, and insulin resistance (IR). However, BCAA supplementation was found to provide positive outcomes in cirrhosis and HCC patients. This review will attempt to address the contradictory claims found in the literature, with a special focus on BCAAs' distribution, key signaling pathways, and the modulation of gut microbiota. This should provide a better understanding of BCAAs' possible contribution to liver health.

Abnormal phenotype of Nrf2 is associated with poor prognosis through hypoxic/VEGF-A-Rap1b/VEGFR2 pathway in gastric cancer

Metastasis is the major cause of death in gastric cancer patients and altered expression of Nrf2 is associated with cancer development. This study assessed Nrf2 and HO-1 expression and hypoxia-induced Nrf2 expression in the promotion of metastatic potential of gastric cancer cells, the relationship of Rap1b and Nrf2 was also discussed. Nrf2 and HO-1 expression were significantly associated with clinicopathological characteristic and were independent prognostic predictors in gastric cancer patients. Hypoxia up-regulated the expression of Nrf2, HO-1 and HIF-1α, whereas knockdown of Nrf2 inhibited cell invasion capacity and reduced the expression of Nrf2, HO-1 and HIF-1α. Patients in the Rap1b (+) Nrf2 (+) group had worst overall survival compared with those from other groups. Knockdown of Rap1b and Nrf2 significantly inhibited cell invasion capacity in the common group compared with the other groups. Hypoxia or VEGF-A facilitated the nuclear translocation of Nrf2 through Rap1b or VEGFR2. Hypoxia or VEGF-A did not induce the phosphorylation of P-Erk1/2 and P-Akt after knockdown of Rap1b or VEGFR2. Hypoxia promoted the gastric cancer malignant behavior through the upregulation of Rap1b and Nrf2. Hypoxia/VEGF-A-Rap1b/VEGFR2 facilitated the nuclear translocation of Nrf2. Targeting Rap1b and Nrf2 may be a novel therapeutic strategy for gastric cancer.

Regulation of the Leucine Metabolism in Mortierella alpina

The oleaginous fungus Mortierella alpina is a safe source of polyunsaturated fatty acids (PUFA) in industrial food and feed production. Besides PUFA production, pharmaceutically relevant surface-active and antimicrobial oligopeptides were isolated from this basal fungus. Both production of fatty acids and oligopeptides rely on the biosynthesis and high turnover of branched-chain-amino acids (BCAA), especially l-leucine. However, the regulation of BCAA biosynthesis in basal fungi is largely unknown. Here, we report on the regulation of the leucine, isoleucine, and valine metabolism in M. alpina. In contrast to higher fungi, the biosynthetic genes for BCAA are hardly transcriptionally regulated, as shown by qRT-PCR analysis, which suggests a constant production of BCAAs. However, the enzymes of the leucine metabolism are tightly metabolically regulated. Three enzymes of the leucine metabolism were heterologously produced in Escherichia coli, one of which is inhibited by allosteric feedback loops: The key regulator is the α-isopropylmalate synthase LeuA1, which is strongly disabled by l-leucine, α-ketoisocaproate, and propionyl-CoA, the precursor of the odd-chain fatty acid catabolism. Its gene is not related to homologs from higher fungi, but it has been inherited from a phototrophic ancestor by horizontal gene transfer.

Emerging Moonlighting Functions of the Branched-Chain Aminotransferase Proteins

Significance: Unique to the branched-chain aminotransferase (BCAT) proteins is their redox-active CXXC motif. Subjected to post-translational modification by reactive oxygen species and reactive nitrogen species, these proteins have the potential to adopt numerous cellular roles, which may be fundamental to their role in oncogenesis and neurodegenerative diseases. An understanding of the interplay of the redox regulation of BCAT with important cell signaling mechanisms will identify new targets for future therapeutics. Recent Advances: The BCAT proteins have been assigned novel thiol oxidoreductase activity that can accelerate the refolding of proteins, in particular when S-glutathionylated, supporting a chaperone role for BCAT in protein folding. Other metabolic proteins were also shown to have peroxide-mediated redox associations with BCAT, indicating that the cellular function of BCAT is more diverse. Critical Issues: While the role of branched-chain amino acid metabolism and its metabolites has dominated aspects of cancer research, less is known about the role of BCAT. The importance of the CXXC motif in regulating the BCAT activity under hypoxic conditions, a characteristic of tumors, has not been addressed. Understanding how these proteins operate under various cellular redox conditions will become important, in particular with respect to their moonlighting roles. Future Directions: Advances in the quantification of thiols, their measurement, and the manipulation of metabolons that rely on redox-based interactions should accelerate the investigation of the cellular role of moonlighting proteins such as BCAT. Given the importance of cross talk between signaling pathways, research should focus more on these "housekeeping" proteins paying attention to their wider application. Antioxid. Redox Signal. 34, 1048-1067.

Differential expression of the BCAT isoforms between breast cancer subtypes

Background

Biological characterisation of breast cancer subtypes is essential as it informs treatment regimens especially as different subtypes have distinct locoregional patterns. This is related to metabolic phenotype, where altered cellular metabolism is a fundamental adaptation of cancer cells during rapid proliferation. In this context, the metabolism of the essential branched-chain amino acids (BCAAs), catalysed by the human branched-chain aminotransferase proteins (hBCAT), offers multiple benefits for tumour growth. Upregulation of the cytosolic isoform of hBCAT (hBCATc), regulated by c-Myc, has been demonstrated to increase cell migration, tumour aggressiveness and proliferation in gliomas, ovarian and colorectal cancer but the importance of the mitochondrial isoform, hBCATm has not been fully investigated.

Methods

Using immunohistochemistry, the expression profile of metabolic proteins (hBCAT, IDH) was assessed between breast cancer subtypes, HER2 + , luminal A, luminal B and TNBC. Correlations between the percentage and the intensity of protein expression/co-expression with clinical parameters, such as hormone receptor status, tumour stage, lymph-node metastasis and survival, were determined.

Results

We show that hBCATc expression was found to be significantly associated with the more aggressive HER2 + and luminal B subtypes, whilst hBCATm and IDH1 associated with luminal A subtype. This was concomitant with better prognosis indicating a differential metabolic reliance between these two subtypes, in which enhanced expression of IDH1 may replenish the α-ketoglutarate pool in cells with increased hBCATm expression.

Conclusion

The cytosolic isoform of BCAT is associated with tumours that express HER2 receptors, whereas the mitochondrial isoform is highly expressed in tumours that are ER + , indicating that the BCAT proteins are regulated through different signalling pathways, which may lead to the identification of novel targets for therapeutic applications targeting dysregulated cancer metabolism.