Prognostic significance of branched-chain amino acid transferase 1 and CD133 in triple-negative breast cancer

Small-molecule targeting BCAT1-mediated BCAA metabolism inhibits the activation of SHOC2-RAS-ERK to induce apoptosis of Triple-negative breast cancer cells

INTRODUCTION

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer with the worst prognosis. Exploring novel carcinogenic factors and therapeutic drugs for TNBC remains a focus to improve prognosis. Branched-chain amino acid transaminase 1 (BCAT1), a crucial enzyme in branched-chain amino acid (BCAA) metabolism, has been linked to various tumor developments, but its carcinogenic function and mechanism in TNBC remain unclear. Eupalinolide B (EB) is a naturally-derived small-molecule with anti-tumor activity, but its role in TNBC remains unknown.

OBJECTIVES

By exploring the targets and pharmacological mechanisms of EB in inhibiting TNBC, this study aimed to discover novel therapeutic targets and potential inhibitors for TNBC, and elucidate novel pathogenic mechanisms of TNBC.

METHODS

The inhibitory effect of EB on TNBC was investigated using mouse models and cellular phenotypic experiments. Activity-based protein profiling (ABPP) technology, pull down-WB, CETSA-WB and MST were utilized to discover and validate the targets of EB. The oncogenic role of BCAT1 was determined through clinical data analysis and biochemical experiments. To elucidate the mechanism by which EB inhibited TNBC, many methods, including but not limited to HPLC and proteomic sequencing were used.

RESULTS

We found that EB significantly inhibited TNBC progression. We identified BCAT1 as the direct target of EB and confirmed that BCAT1 was critical for TNBC development. EB inhibited BCAT1-involved BCAA metabolism to reduce the synthesis of BCAAs (including Leu, Ile, and Val), thereby inhibiting SHOC2 (a Leu-rich repeat protein) expression and the downstream SHOC2-participating RAS-ERK signaling pathway, ultimately leading to apoptosis of TNBC cells.

CONCLUSION

Collectively, this study not only elucidates the oncogenic role of BCAT1 and its downstream SHOC2-RAS-ERK signaling axis in TNBC progression but also opens up avenues for potential therapies targeting BCAT1 or BCAA metabolism (using EB alone or in combination with its inhibitor candesartan) for TNBC treatment.

Identify BCAT1 plays an oncogenic role and promotes EMT in KIRC via single cell RNA-seq and experiment

Background

Kidney renal clear cell carcinoma (KIRC) is a major subtype of renal cell carcinoma with poor prognosis due to its invasive and metastatic nature. Despite advances in understanding the molecular underpinnings of various cancers, the role of branched-chain amino acid transferase 1 (BCAT1) in KIRC remains underexplored. This study aims to fill this gap by investigating the oncogenic role of BCAT1 in KIRC using single-cell RNA-seq data and experimental validation.

Methods

Single-cell transcriptomic data GSE159115 was utilized to investigate potential biomarkers in KIRC. After screening, we used BCAT1 as a target gene and investigated its function and mechanism in KIRC through databases such as TCGA-GTEx, using genome enrichment analysis (GSEA), genome variation analysis (GSVA), gene ontology (GO) and Kyoto Encyclopedia of the Genome (KEGG). BCAT1 expression was detected in clinical tissue samples using Western Blotting (WB) and immunohistochemical (IHC) staining techniques. We established cell lines stably overexpressing and knocking down BCAT1 and performed WB, qRT-PCR, cell scratch assay and transwell assay.

Results

BCAT1 was highly expressed in KIRC and was associated with disease prognosis and TME. Patients with mutations in the BCAT1 gene had shorter overall survival (OS) and disease-free survival (DFS). patients with high BCAT1 expression had shorter OS, progression-free interval (PFI), and disease-specific survival (DSS). GSEA showed that BCAT1 was significantly enriched in epithelial mesenchymal transition (EMT). Bioinformatics analysis and WB and IHC staining showed that BCAT1 expression was higher in KIRC than in paracancerous tissues. In vitro experiments confirmed that BCAT1 in KIRC cells may promote EMT affecting its invasion, migration. We constructed a protein interaction network (PPI) to hypothesize proteins that may interact with BCAT1. Single-sample gene set enrichment analysis (ssGSEA) revealed the immune infiltration environment of BCAT1. Furthermore, hypomethylation of the BCAT1 promoter region in KIRC may contribute to disease progression by promoting BCAT1 expression.

Conclusion

BCAT1 promotes KIRC invasion and metastasis through EMT and has prognostic predictive value and potential as a biomarker. It may become a novel biomarker.

Association of CD133, ALDH1, CD117 and OCT4 expression with prognosis of patients with cervical cancer

Cancer stem cells (CSC), a small population of neoplastic cells, are associated with worse prognosis. The aim of this study was to evaluate the expression of ALDH1, CD117, CD133 and OCT4; potential markers of CSC; and their associations with the prognosis of women diagnosed with cervical cancer. This retrospective cohort study included 126 women diagnosed with cervical cancer whose biopsies were analyzed by immunohistochemistry. Median values of marked cells were used to define cutoff points for low and high expression. For specific survival, multivariate analyses showed statistical significance for lymph node metastases (HR 8.15; 95% CI 3.00-22.18) and borderline significance for high CD133 expression (p = 0.058). For overall survival, multivariate analyses showed statistical significance for IIA-IVB staging (HR 4.60; 95% CI 1.46-14.56), lymph node metastases (HR 5.13; 95% CI 12.02-13.03) and high CD133 expression (2.67; 95% CI 1.11-6.43). Considering only women with SCC, the same clinicopathological variables were associated with worse specific and overall survival in univariate analyses. However, higher expression of CD 133 (HR 11.10; 95% CI 2.42-50.94 and 6.00; 95% CI 2.02-17.87) and staging IIA-IVB (HR 5.96; 95% CI 1.30-27.34 and HR 12.47; 95% CI 2.45-63.54) respectively impacted negatively specific and overall survival, as multivariate analyses showed. Secondarily, it was observed that ALDH1 expression was associated with adenocarcinoma and CD117 expression with squamous cells carcinoma. Higher expression of CD133 was associated with worse specific and overall survival, indicating that it could have relevance as a clinical marker and therapeutic target.

DNA methylation profile of inflammatory breast cancer and its impact on prognosis and outcome

BACKGROUND

Inflammatory breast cancer (IBC) is a rare disease characterized by rapid progression, early metastasis, and a high mortality rate.

METHODS

Genome-wide DNA methylation analysis (EPIC BeadChip platform, Illumina) and somatic gene variants (105 cancer-related genes) were performed in 24 IBCs selected from a cohort of 140 cases.

RESULTS

We identified 46,908 DMPs (differentially methylated positions) (66% hypomethylated); CpG islands were predominantly hypermethylated (39.9%). Unsupervised clustering analysis revealed three clusters of DMPs characterized by an enrichment of specific gene mutations and hormone receptor status. The comparison among DNA methylation findings and external datasets (TCGA-BRCA stages III-IV) resulted in 385 shared DMPs mapped in 333 genes (264 hypermethylated). 151 DMPs were associated with 110 genes previously detected as differentially expressed in IBC (GSE45581), and 68 DMPs were negatively correlated with gene expression. We also identified 4369 DMRs (differentially methylated regions) mapped on known genes (2392 hypomethylated). BCAT1, CXCL12, and TBX15 loci were selected and evaluated by bisulfite pyrosequencing in 31 IBC samples. BCAT1 and TBX15 had higher methylation levels in triple-negative compared to non-triple-negative, while CXCL12 had lower methylation levels in triple-negative than non-triple-negative IBC cases. TBX15 methylation level was associated with obesity.

CONCLUSIONS

Our findings revealed a heterogeneous DNA methylation profile with potentially functional DMPs and DMRs. The DNA methylation data provided valuable insights for prognostic stratification and therapy selection to improve patient outcomes.

Integrated single-cell and bulk characterization of branched chain amino acid metabolism-related key gene BCAT1 and association with prognosis and immunogenicity of clear cell renal cell carcinoma

BACKGROUND

The relationship between clear cell renal cell carcinoma (ccRCC) and branched-chain amino acids (BCAA) metabolism has yet to be thoroughly explored.

METHODS

The BCAA metabolism-related clusters were constructed using non-negative matrix factorization (NMF). The features of BCAA metabolism in ccRCC were evaluated by building a prognostic model using least absolute shrinkage and selection operator (LASSO) regression algorithm. Real-time quantitative PCR (RT-qPCR) was employed to analyze differential expression of branched-chain amino acid transaminase 1 (BCAT1) between cancer and paracancer tissues and between different cell lines. Cell counting kit-8, wound healing and Transwell chamber assays were conducted to determine changes in proliferative and metastatic abilities of A498 and 786-O cells.

RESULTS

Two BCAA metabolism-related clusters with distinct prognostic and immune infiltration characteristics were identified in ccRCC. The BCAA metabolic signature (BMS) was capable of distinguishing immune features, tumor mutation burden, responses to immunotherapy, and drug sensitivity among ccRCC patients. RT-qPCR revealed overexpression of BCAT1 in ccRCC tissues and cell lines. Additionally, single-gene RNA sequencing analysis demonstrated significant enrichment of BCAT1 in macrophages and tumor cells. BCAT1 played tumor-promoting role in ccRCC and was closely associated with immunosuppressive cells and checkpoints. BCAT1 promoted ccRCC cell proliferation and metastasis.

CONCLUSIONS

The BMS played a crucial role in determining the prognosis, tumor mutation burden, responses to immunotherapy and drug sensitivity of ccRCC patients, as well as the immune cell infiltration features. BCAT1 was linked to immunosuppressive microenvironments and may offer new sights into ccRCC immunotherapeutic targets.

The combination of the HDAC1 inhibitor SAHA and doxorubicin has synergic efficacy in triple negative breast cancer in vivo

Vorinostat (SAHA) is a histone deacetylase inhibitor that exerts its effects through epigenetic regulation. Specifically, SAHA can inhibit the proliferation of triple-negative breast cancer (TNBC) cells alone or in combination with other chemotherapeutic agents. Doxorubicin (DOX), a traditional chemotherapeutic drug, exhibits a potent cytotoxic effect on cancer cells while also inducing strong toxic effects. In this study, we investigated the synergistic potential of these two drugs in combination against TNBC. Our results suggested that the combination of these two drugs could enhance the inhibitory effect on cancer cell proliferation, resulting in alterations in cell mitotic phase, and suppression of cancer cell stemness. Moreover, our in vivo study unveiled that when SAHA was combined with DOX, it not only exhibited an inhibitory effect on tumor metastasis but also played a role in regulating the immune microenvironment within tumors. Overall, the combination of DOX and SAHA presents a promising avenue for innovative combination chemotherapy in the context of TNBC.

Histone deacetylase inhibitor panobinostat in combination with rapamycin confers enhanced efficacy against triple-negative breast cancer

Triple-negative breast cancer (TNBC) accounts for about 15% of diagnosed breast cancer patients, which has a poor survival outcome owing to a lack of effective therapies. This study aimed to explore the in vitro and in vivo efficiency of histone deacetylase (HDAC) inhibitor panobinostat (PANO) in combination with mTOR inhibitor rapamycin (RAPA) against TNBC. TNBC cells were treated with PANO, RAPA alone or the combination of drugs, then cell growth and apoptosis were evaluated by CCK-8, colony formation and flow cytometry. Cell migration and invasion were detected by wound healing assay and transwell assay, respectively. ROS production was detected by DCFH-DA staining. Western blotting was performed to detect protein levels. In vivo tumor growth was assessed in nude mice. The expression of cleaved caspase-3 and Ki-67 in tumor tissues was detected by immunofluorescence staining. H&E staining was conducted to observe the pathological changes in heart, liver, and kidney tissues. The combination of PANO and RAPA exerted a stronger role in repressing growth, migration, invasion, and inducing apoptosis of TNBC cells compared with monotherapy. Furthermore, this combination presented a more effective anti-cancer efficacy than a single treatment in the xenograft model without apparent toxic side effects. Importantly, mechanistic studies indicated that PANO and RAPA combination led to ROS overproduction, which subsequently activated endoplasmic reticulum stress. Conclusion: PANO in combination with RAPA exhibits enhanced efficacy against TNBC, which may be considered a promising therapeutic candidate.

Photodynamic therapy with zinc phthalocyanine enhances the anti-cancer effect of tamoxifen in breast cancer cell line: Promising combination treatment against triple-negative breast cancer?

Photodynamic therapy (PDT) is a light-based anti-neoplastic therapeutic approach. Growing evidence indicates that combining conventional anti-cancer therapies with PDT can be a promising approach to treat malignancies. Herein, we aimed to investigate anti-cancer effects of the combination treatment of zinc phthalocyanine (ZnPc)-PDT with tamoxifen (TA) on MDA-MB-231 cells (as a triple-negative breast cancer (TNBC) cell line). For this purpose, we investigated the cytotoxicity of TA and ZnPc-PDT on MDA-MB-231 cells performing the MTT assay. The effect of TA and ZnPc-PDT on the apoptosis of MDA-MB-231 cells was studied using Annexin V/PI and DAPI staining. The wound-healing assay, and colony formation assay were performed to study the effect of TA and ZnPc-PDT on the migration, and clonogenicity of MDA-MB-231 cells, respectively. The qRT-PCR was done to study the gene expression of caspase-8, caspase-9, caspase-3, ZEB1, ROCK1, SNAIL1, CD133, CD44, SOX2, and ABCG2 (ATP-binding cassette sub-family G member 2). Based on our results, monotherapies with TA and ZnPc-PDT can remarkably increase cell cytotoxicity effects, stimulate apoptosis via downregulating Bcl-2 and upregulating caspase-3 and caspase-9, inhibit migration via downregulating SNAIL1 and ZEB1, and suppress clonogenicity via downregulating SOX2 and CD44 in MDA-MB-231 cells. Besides, these monotherapies can downregulate the expression of ABCG2 in MDA-MB-231 cells. Nevertheless, the combination treatment can potentiate the above-mentioned anti-cancer effects compared to monotherapy with TA. Of interest, the combined treatment of TA with ZnPc-PDT can synergically increase cell cytotoxicity effects on MDA-MB-231 cells. In fact, synergistic effects were estimated by calculation of Combination Index (CI); that synergistic outcomes were observed in all groups. Also, this combination treatment can significantly upregulate the caspase-8 gene expression and downregulate ROCK1 and CD133 gene expression in MDA-MB-231 cells. Overall, our results show that ZnPc-PDT can more sensitize the MDA-MB-231 cells to TA treatment. Based on our knowledge and experiment, the synergistic effects of ZnPc-PDT and TA deserve further evaluation in cancer research.

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.

Detection of hypermethylated BCAT1 and IKZF1 DNA in blood and tissues of colorectal, breast and prostate cancer patients

BACKGROUND: Detection of circulating cell-free DNA (ccfDNA) methylated in BCAT1 and IKZF1 is a sensitive for detection of colorectal cancer (CRC), but it is not known if these biomarkers are present in other common adenocarcinomas. OBJECTIVE: Compare methylation levels of BCAT1 and IKZF1 in tissue and plasma from breast, prostate, and colorectal cancer patients. METHODS: Blood was collected from 290 CRC, 32 breast and 101 prostate cancer patients, and 606 cancer-free controls. Tumor and matched normal tissues were collected at surgery: 26 breast, 9 prostate and 15 CRC. DNA methylation in BCAT1 and IKZF1 was measured in blood and tissues. RESULTS: Either biomarker was detected in blood from 175/290 (60.3%) of CRC patients. The detection rate was higher than that measured in controls (48/606 (8.1%), OR = 18.2, 95%CI: 11.1–29.0). The test positivity rates in breast and prostate cancer patients were 9.4% (3/32) and 6.9% (7/101), respectively, and not significantly different to that measured in gender-matched controls (8.0% (33/382) females (OR = 0.84, 95%CI: 0.23–3.1) and 7.6% (26/318) males (OR = 0.86, 95%CI: 0.65–2.1). In tumor and non-neoplastic tissues, 93.5% (14/15) of CRC tumors were methylated in BCAT1 and/or IKZF1 (p< 0.004). Only 11.5% (3/26) and 44.4% (4/9) (p= 0.083) of breast and prostate tumors were hypermethylated in these two genes. CONCLUSIONS: Detection of circulating DNA methylated in BCAT1 and IKZF1 is sensitive and specific for CRC but not breast or prostate cancer.

Novel insights linking BRCA1-IRIS role in mammary gland development to formation of aggressive PABCs: the case for longer breastfeeding

Pregnancy-associated breast cancer (PABC) is diagnosed during or shortly after pregnancy. Although rare, PABC is a serious occurrence often of the triple negative (TNBC) subtype. Here we show progesterone, prolactin, and RANKL upregulate BRCA1-IRIS (IRIS) in separate and overlapping subpopulations of human mammary epithelial cell lines, which exacerbates the proliferation, survival, and the TNBC-like phenotype in them. Conversely, vitamin D₃ reduces IRIS expression in TNBC cell lines, which attenuates growth, survival, and the TNBC-like phenotype in them. In the mouse, Brca1-Iris (Iris, mouse IRIS homolog) is expressed at low-level in nulliparous mice, increases ~10-fold in pregnant/lactating mice, to completely disappear in involuting mice, and reappears at low-level in regressed glands. Mice underwent 3 constitutive pregnancies followed by a forced involution (after 5 days of lactation) contained ~10-fold higher Iris in their mammary glands compared to those underwent physiological involution (after 21 days of lactation). While protein extracts from lactating glands promote proliferation in IRIS^low and IRIS overexpressing (IRISOE) cells, extracts from involuting glands promote apoptosis in IRIS^low, and aneuploidy in IRISOE cells. In a cohort of breast cancer patients, lack of breastfeeding was associated with formation of chemotherapy resistant, metastatic IRISOE breast cancers. We propose that terminal differentiation triggered by long-term breastfeeding reduces IRIS expression in mammary cells allowing their elimination by the inflammatory microenvironment during physiological involution. No/short-term breastfeeding retains in the mammary gland IRISOE cells that thrive in the inflammatory microenvironment during forced involution to become precursors for aggressive breast cancers shortly after pregnancy.

Metabolomics Strategy Assisted by Transcriptomics Analysis to Identify Potential Biomarkers Associated with Tuberculosis

Purpose

To investigate the dysregulated pathways and identify reliable diagnostic biomarkers for tuberculosis using integrated analysis of metabolomics and transcriptomics.

Methods

Three groups of samples, untargeted metabolomics analysis of healthy controls (HC), latent tuberculosis infection patients (LTBI), and active tuberculosis patients (TB), were analyzed using gas chromatography time-of-flight mass spectrometry (GC-TOF MS) and ultra-high performance liquid chromatography-quantitative mass spectrometry (UHPLC-QE-MS). Both univariate and multivariate and statistical analyses were used to select differential metabolites (DMs) among group comparison, and LASSO regression analysis was employed to discover potential diagnostic biomarkers. Metabolite set enrichment analysis was performed to identify the altered metabolic pathways specifically in patients with TB. Meanwhile, a transcriptomic dataset GSEG4992 was downloaded from the GEO database to explore the differentially expressed genes (DEGs) between TB and HC identified in significantly enriched pathways. Finally, an integrative analysis of DMs and DEGs was performed to investigate the possible molecular mechanisms of TB.

Results

Thirty-three specific metabolites were significantly different between TB and HC, of which 7 (5-hydroxyindoleacetic acid, isoleucyl-isoleucine, heptadecanoic acid, indole acetaldehyde, 5-ethyl-2,4-dimethyloxazole, and 2-hydroxycaproic acid, unknown 71) were chosen as combinational potential biomarkers for TB. The area under the curve (AUC) value of these biomarkers was 0.97 (95% CI: 0.92–1.00). Metabolites set enrichment analysis (MSEA) displayed that there were 3 significantly enriched pathways among all. The genes in 3 significantly enriched pathways were further analyzed, of which 9(ALDH3B1, BCAT1, BCAT2, GLYAT, GOT1, IL4I1, MIF, SDS, SDSL) were expressed differentially. The area under the curve (AUC) values of these DEGs enriched in pathways mostly were greater than 0.8. As a result, a connected network of metabolites and genes in the pathways were established, which provides insights into the credibility of selected metabolites.

Conclusion

The newly identified metabolic biomarkers display a high potential to be developed into a promising tool for TB screening, diagnosis, and therapeutic effect monitoring.

An overview of branched-chain amino acid aminotransferases: functional differences between mitochondrial and cytosolic isozymes in yeast and human

Branched-chain amino acid aminotransferase (BCAT) catalyzes bidirectional transamination in the cell between branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) and branched-chain α-keto acids (BCKAs; α-ketoisovalerate, α-ketoisocaproate, and α-keto-β-methylvalerate). Eukaryotic cells contain two types of paralogous BCATs: mitochondrial BCAT (BCATm) and cytosolic BCAT (BCATc). Both isozymes have identical enzymatic functions, so they have long been considered to perform similar physiological functions in the cells. However, many studies have gradually revealed the differences in physiological functions and regulatory mechanisms between them. In this article, we present overviews of BCATm and BCATc in both yeast and human. We also introduce BCAT variants found natively or constructed artificially, which could have significant implications for research into the relationship between the primary structures and protein functions of BCATs. KEY POINTS: • BCAT catalyzes bidirectional transamination in the cell between BCAAs and BCKAs. • BCATm and BCATc are different in the metabolic roles and regulatory mechanisms. • BCAT variants offer insight into a relationship between the structure and function.

Nuclear Receptor-Mediated Metabolic Reprogramming and the Impact on HR+ Breast Cancer

Simple Summary

Breast cancer is the most commonly diagnosed and second leading cause of cancer-related deaths in women in the United States, with hormone receptor positive (HR+) tumors representing more than two-thirds of new cases. Recent evidence has indicated that dysregulation of multiple metabolic programs, which can be driven through nuclear receptor activity, is essential for tumor genesis, progression, therapeutic resistance and metastasis. This study will review the current advances in our understanding of the impact and implication of altered metabolic processes driven by nuclear receptors, including hormone-dependent signaling, on HR+ breast cancer.

Abstract

Metabolic reprogramming enables cancer cells to adapt to the changing microenvironment in order to maintain metabolic energy and to provide the necessary biological macromolecules required for cell growth and tumor progression. While changes in tumor metabolism have been long recognized as a hallmark of cancer, recent advances have begun to delineate the mechanisms that modulate metabolic pathways and the consequence of altered signaling on tumorigenesis. This is particularly evident in hormone receptor positive (HR+) breast cancers which account for approximately 70% of breast cancer cases. Emerging evidence indicates that HR+ breast tumors are dependent on multiple metabolic processes for tumor progression, metastasis, and therapeutic resistance and that changes in metabolic programs are driven, in part, by a number of key nuclear receptors including hormone-dependent signaling. In this review, we discuss the mechanisms and impact of hormone receptor mediated metabolic reprogramming on HR+ breast cancer genesis and progression as well as the therapeutic implications of these metabolic processes in this disease.

miR-98-5p inhibits gastric cancer cell stemness and chemoresistance by targeting branched-chain aminotransferases 1

AIMS

Gastric cancer stem cells (GCSCs) have been used as a therapeutic target. This study aims to estimate the role of miR-98-5p (termed miR-98) in the development of GCSCs.

MAIN METHODS

The expression of miR-98 in CD44+ GCSCs was verified by RT-PCR. The miR-98 was overexpressed in CD44+ GCSCs by Lentivirus. The ability of self-renewal, invasion, chemoresistance and tumorigenicity was detected in vitro or in vivo after overexpression of miR-98. The target genes of miR-98 were predicted and verified by luciferase reporter assays. The effects miR-98/BCAT1 signaling on the chemoresistance and tumorigenicity of CD44+ GCSCs were investigated in a xenograft model by rescue experiments.

KEY FINDINGS

We have shown that miR-98 was decreased in CD44+ GCSCs. The overexpression of miR-98 could inhibit the expression of stem-related genes and the ability of self-renewal, invasion, and tumorigenicity of GCSCs. Also, we found that miR-98 overexpression enhances the sensitivity to cisplatin treatment in vitro. Using a xenograft model, we showed that miR-98 overexpression reversed paclitaxel resistance to CD44+ GCSCs. Finally, we found that branched-chain aminotransferases 1 (BCAT1) is a target gene of miR-98. Overexpressed BCAT1 reversed xenograft tumor formation ability and attenuated the paclitaxel chemosensitivity induced by miR-98 downregulation. Furthermore, BCAT1 restoration affected the expression of invasion and drug resistance-related genes.

SIGNIFICANCE

This study revealed miR-98 inhibits gastric cancer cell stemness and chemoresistance by targeting BCAT1, suggesting that this miR-98/BCAT1 axis represents a potential therapeutic target in gastric cancer.

BCAT1 Activates PI3K/AKT/mTOR Pathway and Contributes to the Angiogenesis and Tumorigenicity of Gastric Cancer

BACKGROUND

Focusing on antiangiogenesis may provide promising choices for treatment of gastric cancer (GC). This study aimed to investigate the mechanistic role of BCAT1 in the pathogenesis of GC, particularly in angiogenesis.

METHODS

Bioinformatics and clinical samples analysis were used to investigate the expression and potential mechanism of BCAT1 in GC. BGC823 cells with BCAT1 overexpression or silencing were induced by lentiviral transduction. Cell phenotypes and angiogenesis were evaluated. The relevant proteins were quantized by Western blotting, immunohistochemistry, or immunofluorescence. Xenograft models were constructed to confirm the role of BCAT1 in vivo.

RESULTS

BCAT1 was overexpressed in GC patients and associated with lower survival. BCAT1 expression was correlated with proliferation-, invasion-, or angiogenesis-related markers expression and pathways. Silencing BCAT1 expression suppressed cell viability, colony formation, cycle progression, invasion, and angiogenesis of BGC823 cells, as well as the tumor growth of xenograft models, whereas overexpressing BCAT1 had the opposite results both in vitro and in vivo. Bioinformatics analysis and Western blotting demonstrated that BCAT1 activated the PI3K/AKT/mTOR pathway. The addition of LY294002 reversed the tumor growth induced by BCAT1 overexpression, further verifying this mechanism.

CONCLUSION

BCAT1 might act as an oncogene by facilitating proliferation, invasion, and angiogenesis through activation of the PI3K/AKT/mTOR pathway. This finding could aid the optimization of antiangiogenesis strategies.