Identification of glycogene-type and validation of ST3GAL6 as a biomarker predicts clinical outcome and cancer cell invasion in urinary bladder cancer

Glycan-Lectin interactions between platelets and tumor cells drive hematogenous metastasis

Glycosylation is a ubiquitous cellular or microenvironment-specific post-translational modification that occurs on the surface of normal cells and tumor cells. Tumor cell-associated glycosylation is involved in hematogenous metastasis. A wide variety of tumors undergo aberrant glycosylation to interact with platelets. As platelets have many opportunities to engage circulating tumor cells, they represent an important avenue into understanding the role glycosylation plays in tumor metastasis. Platelet involvement in tumor metastasis is evidenced by observations that platelets protect tumor cells from damaging shear forces and immune system attack, aid metastasis through the endothelium at specific sites, and facilitate tumor survival and colonization. During platelet-tumor-cell interactions, many opportunities for glycan-ligand binding emerge. This review integrates the latest information about glycans, their ligands, and how they mediate platelet-tumor interactions. We also discuss adaptive changes that tumors undergo upon glycan-lectin binding and the impact glycans have on targeted therapeutic strategies for treating tumors in clinical settings.

Identification of potential therapeutic target SPP1 and related RNA regulatory pathway in keloid based on bioinformatics analysis

OBJECTIVE

To explore the complex mechanisms of keloid, new approaches have been developed by different strategies. However, conventional treatment did not significantly reduce the recurrence rate. This study aimed to identify new biomarkers and mechanisms for keloid progression through bioinformatics analyses.

METHODS

In our study, microarray datasets for keloid were downloaded from the GEO database. Differentially expressed genes (DEGs) were identified by R software. Multiple bioinformatics tools were used to identify hub genes, and reverse predict upstream miRNAs and lncRNA molecules of target hub genes. Finally, the total RNA-sequencing technique and miRNA microarray were combined to validate the identified genes.

RESULTS

Thirty-one DEGs were screened out and the upregulated hub gene SPP1 was finally identified, which was consistent with our RNA-sequencing analysis results and validation dataset. In addition, a ceRNA network of mRNA (SPP1)-miRNA (miR-181a-5p)-lncRNA (NEAT1, MALAT1, LINC00667, NORAD, XIST and MIR4458HG) was identified by the bioinformatics databases. The results of our miRNA microarray showed that miR-181a-5p was upregulated in keloid, also we found that the lncRNA NEAT1 could affect keloid progression by retrieving the relevant literature.

CONCLUSIONS

We speculate that SPP1 is a potential candidate biomarker and therapeutic target for patients with keloid, and NEAT1/miR-181a-5p/SPP1 might be the RNA regulatory pathway that regulates keloid formation.

Identification and validation of sialyltransferase ST3Gal5 in bladder cancer through bioinformatics and experimental analysis

BACKGROUND

Bladder cancer (BLCA) is one of the top ten most common cancers in the world. Aberrant sialylation is a common feature in tumorigenesis and tumor immunity. This study seeks to explore the potential impact of sialyltransferase ST3Gal5 on BLCA.

METHODS

Initially, glycosyltransferase-related DEGs (GRDEGs) were identified using multiple bioinformatics approaches in TCGA-BLCA cohort and validated using GEO databases. Clinical prognosis integration facilitated the determination of ST3Gal5 as an independent prognostic factor in BLCA, employing univariate and multivariate Cox regression analyses. Immune cell infiltration was assessed via CIBERSORT and ssGSEA analyses, while HLA and immune checkpoint genes' levels, along with drug sensitivity, were evaluated in low- and high-ST3Gal5 groups. The TIDE and IPS scores were used to gauge the immune checkpoint blockade (ICB) response. Furthermore, functional experiments, both in vivo and in vitro, were conducted to elucidate the biological roles of ST3Gal5.

RESULTS

In agreement with bioinformatics findings, ST3Gal5 expression was down-regulated in BLCA tissues and cells, correlating with poorer prognostic outcomes. The StromalScore, ImmuneScore, and ESTIMATEScore were significantly elevated in low-ST3Gal5 group. Moreover, the levels of HLA and immune checkpoint genes were upregulated in low-ST3Gal5 group. Down-regulated ST3Gal5 promoted the proliferation, migration, and invasion of BLCA cells in vivo and in vitro.

CONCLUSION

Our findings demonstrated that low ST3Gal5 level promoted tumorigenesis and progression of BLCA, implying its potential as a predictive biomarker and therapeutic target.

A metabolic reprogramming-related gene signature correlates with prognosis and proliferation of BLCA

Bladder cancer (BLCA) is one of the most frequent urothelium carcinoma, but with poor prognosis due to lack of reliable predictive biomarkers. Metabolic reprogramming involving in various nutrients, and is reported to be closely associated with malignant progression in BLCA. With the use of transcriptome sequencing data profiles of 349 patients from The Cancer Genome Atlas, we established a three-gene glycolysis-related signature to predict the prognosis of BLCA patients. Our signature constructed on the basis of AK3, GALK1 and NUP205 expression, detail features and interactions between these three genes were further explored. We established a nomogram by integrating clinical variables and the risk score. Glycolytic level and proliferation ability were detected to study the role and mechanisms of NUP205 on BLCA. The connections between three genes in our signature were independent. We found our signature gains more value for patients with highly malignant stage. The established nomogram also confirmed that the signature had a eligible clinically predict capacity. After inhibited NUP205 expression, we found the glycolysis level of BLCA cells decreased and proliferation ability suppressed, mainly through AMPK signaling pathway inactivation. Collectively, our study explored a three-gene glycolysis-related signature that predict the prognosis of patients with BLCA, and highlights NUP205 as a potential therapeutic target for inhibiting glycolytic processes and proliferation in BLCA cells.

Metabolic Signaling in Cancer Metastasis

Metastases, which are the leading cause of death in patients with cancer, have metabolic vulnerabilities. Alterations in metabolism fuel the energy and biosynthetic needs of metastases but are also needed to activate cell state switches in cells leading to invasion, migration, colonization, and outgrowth in distant organs. Specifically, metabolites can activate protein kinases as well as receptors and they are crucial substrates for posttranslational modifications on histone and nonhistone proteins. Moreover, metabolic enzymes can have moonlighting functions by acting catalytically, mainly as protein kinases, or noncatalytically through protein-protein interactions. Here, we summarize the current knowledge on metabolic signaling in cancer metastasis.

SIGNIFICANCE

Effective drugs for the prevention and treatment of metastases will have an immediate impact on patient survival. To overcome the current lack of such drugs, a better understanding of the molecular processes that are an Achilles heel in metastasizing cancer cells is needed. One emerging opportunity is the metabolic changes cancer cells need to undergo to successfully metastasize and grow in distant organs. Mechanistically, these metabolic changes not only fulfill energy and biomass demands, which are often in common between cancer and normal but fast proliferating cells, but also metabolic signaling which enables the cell state changes that are particularly important for the metastasizing cancer cells.

Sialyltransferase ST3GAL6 silencing reduces α2,3-sialylated glycans to regulate autophagy by decreasing HSPB8-BAG3 in the brain with hepatic encephalopathy

End-stage liver diseases, such as cirrhosis and liver cancer caused by hepatitis B, are often combined with hepatic encephalopathy (HE); ammonia poisoning is posited as one of its main pathogenesis mechanisms. Ammonia is closely related to autophagy, but the molecular mechanism of ammonia's regulatory effect on autophagy in HE remains unclear. Sialylation is an essential form of glycosylation. In the nervous system, abnormal sialylation affects various physiological processes, such as neural development and synapse formation. ST3 β‍-galactoside α2,‍3-sialyltransferase 6 (ST3GAL6) is one of the significant glycosyltransferases responsible for adding α2,3-linked sialic acid to substrates and generating glycan structures. We found that the expression of ST3GAL6 was upregulated in the brains of mice with HE and in astrocytes after ammonia induction, and the expression levels of α2,3-sialylated glycans and autophagy-related proteins microtubule-associated protein light chain 3 (LC3) and Beclin-1 were upregulated in ammonia-induced astrocytes. These findings suggest that ST3GAL6 is related to autophagy in HE. Therefore, we aimed to determine the regulatory relationship between ST3GAL6 and autophagy. We found that silencing ST3GAL6 and blocking or degrading α2,3-sialylated glycans by way of Maackia amurensis lectin-II (MAL-II) and neuraminidase can inhibit autophagy. In addition, silencing the expression of ST3GAL6 can downregulate the expression of heat shock protein β8 (HSPB8) and Bcl2-associated athanogene 3 (BAG3). Notably, the overexpression of HSPB8 partially restored the reduced autophagy levels caused by silencing ST3GAL6 expression. Our results indicate that ST3GAL6 regulates autophagy through the HSPB8-BAG3 complex.

Identification of glycogene-based prognostic signature and validation of B3GNT7 as a potential biomarker and therapeutic target in breast cancer

BACKGROUND

Breast cancer is the most common cancer worldwide, with the fifth highest mortality rate among all cancers and high risk of metastasis. However, potential biomarkers and molecular mechanisms underlying the stratification of breast cancer in terms of clinical outcomes remain to be investigated. Therefore, we aimed to find a novel prognostic biomarker and therapeutic target for breast cancer patients.

METHODS

Unsupervised hierarchical clustering was used to perform comprehensive transcriptomic study of total 185 glycogenes in public datasets of breast cancer with clinicopathological and survival information. A glycogene-based signature for subtype classification was discovered using Limma packages, and relevance to four known molecular features was identified by GSVA. Experimental verification was performed and biological functions of B3GNT7 were characterized by quantitative RT-PCR, western blot, transwell assays, and lectin immunofluorescence staining in breast cancer cells.

RESULTS

A 23-glycogene signature was identified for the classification of breast cancer. Among the 23 glycogenes, B3GNTs showed significantly positive associations with ER-/Her2- subtype in breast cancer patients (n = 2655). Overexpressed B3GNT7 were correlated with poor prognosis in breast cancer patients based on public datasets. B3GNT7 depletion inhibited cell proliferation, migration, and invasion, and decreased global fucosylation in MDA-MB-231 and HCC1937 breast cancer cells.

CONCLUSIONS

Herein, we discovered a unique 23-gene signature for breast cancer patient glycogene-type classification. Among these genes, B3GNT7 was shown to be a potential biomarker for unfavorable outcomes and therapeutic target of breast cancer.

Integrating Bulk and Single-Cell RNA Sequencing Reveals Heterogeneity, Tumor Microenvironment, and Immunotherapeutic Efficacy Based on Sialylation-Related Genes in Bladder Cancer

Background

As known abnormal sialylation exerts crucial roles in the growth, metastasis, and immune evasion of cancers, but the molecular characteristics and roles in bladder cancer (BLCA) remain unclear. This study intends to establish BLCA risk stratification based on sialylation-related genes and elucidate its role in prognosis, tumor microenvironment, and immunotherapy of BLCA.

Methods

Bulk RNA-seq and scRNA-seq data were downloaded from open-access databases. The scRNA-seq data were processed using the R package "Seurat" to identify the core cell types. The tumor sub-typing of BLCA samples was performed by the R package "ConsensusClusterPlus" in the bulk RNA-seq data. Signature genes were identified by the R package "limma" and univariate regression analysis to calculate risk scores using the R package "GSVA" and establish risk stratification of BLCA patients. Finally, the differences in clinicopathological characteristics, tumor microenvironment, and immunotherapy efficacy between the different groups were investigated.

Results

5 core cell types were identified in the scRNA-seq dataset, with monocytes and macrophages presenting the greatest percentage, sialylation-related gene expression, and sialylation scores. The bulk RNA-seq samples were classified into 3 tumor subtypes based on 19 prognosis-related sialylation genes. The 10 differential expressed genes (DEGs) with the smallest p-values were collected as signature genes, and the risk score was calculated, with the samples divided into high and low-risk score groups. The results showed that patients in the high-risk score group exhibited worse survival outcomes, higher tumor grade, more advanced stage, more frequency of gene mutations, higher expression levels of immune checkpoints, and lower immunotherapy response.

Conclusion

We established a novel risk stratification of BLCA from a glycomics perspective, which demonstrated good accuracy in determining the prognostic outcome, clinicopathological characteristics, immune microenvironment, and immunotherapy efficacy of patients, and we are proposing to apply it to direct the choice of clinical treatment options for patients.

Integrative analysis of the ST6GALNAC family identifies GATA2-upregulated ST6GALNAC5 as an adverse prognostic biomarker promoting prostate cancer cell invasion

BACKGROUND

ST6GALNAC family members function as sialyltransferases and have been implicated in cancer progression. However, their aberrant expression levels, prognostic values and specific roles in metastatic prostate cancer (PCa) remain largely unclear.

METHODS

Two independent public datasets (TCGA-PRAD and GSE21032), containing 648 PCa samples in total, were employed to comprehensively examine the mRNA expression changes of ST6GALNAC family members in PCa, as well as their associations with clinicopathological parameters and prognosis. The dysregulation of ST6GALNAC5 was further validated in a mouse PCa model and human PCa samples from our cohort (n = 64) by immunohistochemistry (IHC). Gene Set Enrichment Analysis, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes and drug sensitivity analyses were performed to enrich the biological processes most related to ST6GALNAC5. Sulforhodamine B, transwell, luciferase reporter and chromatin immunoprecipitation (ChIP) assays were used to examine the PCa cell proliferation, invasion and transcriptional regulation, respectively.

RESULTS

Systematical investigation of six ST6GALNAC family members in public datasets revealed that ST6GALNAC5 was the only gene consistently and significantly upregulated in metastatic PCa, and ST6GALNAC5 overexpression was also positively associated with Gleason score and predicted poor prognosis in PCa patients. IHC results showed that (1) ST6GALNAC5 protein expression was increased in prostatic intraepithelial neoplasia and further elevated in PCa from a PbCre;Pten^F/F mouse model; (2) overexpressed ST6GALNAC5 protein was confirmed in human PCa samples comparing with benign prostatic hyperplasia samples from our cohort (p < 0.001); (3) ST6GALNAC5 overexpression was significantly correlated with perineural invasion of PCa. Moreover, we first found transcription factor GATA2 positively and directly regulated ST6GALNAC5 expression at transcriptional level. ST6GALNAC5 overexpression could partially reverse GATA2-depletion-induced inhibition of PCa cell invasion. The GATA2-ST6GALNAC5 signature exhibited better prediction on the poor prognosis in PCa patients than GATA2 or ST6GALNAC5 alone.

CONCLUSIONS

Our results indicated that GATA2-upregulated ST6GALNAC5 might serve as an adverse prognostic biomarker promoting prostate cancer cell invasion.

Sialylation: A Cloak for Tumors to Trick the Immune System in the Microenvironment

The tumor microenvironment (TME), where the tumor cells incite the surrounding normal cells to create an immune suppressive environment, reduces the effectiveness of immune responses during cancer development. Sialylation, a type of glycosylation that occurs on cell surface proteins, lipids, and glycoRNAs, is known to accumulate in tumors and acts as a "cloak" to help tumor cells evade immunological surveillance. In the last few years, the role of sialylation in tumor proliferation and metastasis has become increasingly evident. With the advent of single-cell and spatial sequencing technologies, more research is being conducted to understand the effects of sialylation on immunity regulation. This review provides updated insights into recent research on the function of sialylation in tumor biology and summarizes the latest developments in sialylation-targeted tumor therapeutics, including antibody-mediated and metabolic-based sialylation inhibition, as well as interference with sialic acid-Siglec interaction.

A Multigene Signature Associated with Progression-Free Survival after Treatment for IDH Mutant and 1p/19q Codeleted Oligodendrogliomas

BACKGROUND

IDH mutant and 1p/19q codeleted oligodendrogliomas are the gliomas associated with the best prognosis. However, despite their sensitivity to treatment, patient survival remains heterogeneous. We aimed to identify gene expressions associated with response to treatment from a national cohort of patients with oligodendrogliomas, all treated with radiotherapy +/- chemotherapy.

METHODS

We extracted total RNA from frozen tumor samples and investigated enriched pathways using KEGG and Reactome databases. We applied a stability selection approach based on subsampling combined with the lasso-pcvl algorithm to identify genes associated with progression-free survival and calculate a risk score.

RESULTS

We included 68 patients with oligodendrogliomas treated with radiotherapy +/- chemotherapy. After filtering, 1697 genes were obtained, including 134 associated with progression-free survival: 35 with a better prognosis and 99 with a poorer one. Eight genes (ST3GAL6, QPCT, NQO1, EPHX1, CST3, S100A8, CHI3L1, and OSBPL3) whose risk score remained statistically significant after adjustment for prognostic factors in multivariate analysis were selected in more than 60% of cases were associated with shorter progression-free survival.

CONCLUSIONS

We found an eight-gene signature associated with a higher risk of rapid relapse after treatment in patients with oligodendrogliomas. This finding could help clinicians identify patients who need more intensive treatment.

LC-MS based urine untargeted metabolomic analyses to identify and subdivide urothelial cancer

Introduction

Urine metabolomics has been a promising technique in the liquid biopsy of urothelial cancer (UC). The comparison of upper tract urothelial cancer (UTUC), lower tract urothelial cancer (BCa), and healthy controls (HCs) need to be performed to find related biomarkers.

Methods

In our investigation, urine samples from 35 UTUCs, 44 BCas, and 53 gender- and age-matched HCs were analyzed using liquid chromatography-high resolution mass spectrometry (LC-HRMS). In different groups, the differential metabolites and the disturbed metabolism pathways were explored. Transcriptomics and urine metabolomics are combined to identify the probably disturbed gene in BCa.

Results

With an area under the curve (AUC) of 0.815, the panel consisting of prostaglandin I2, 5-methyldeoxycytidine, 2,6-dimethylheptanoyl carnitine, and deoxyinosine was able to discriminate UC from HCs. With an AUC of 0.845, the validation group also demonstrated strong predictive ability. UTUC and BCa without hematuria could be distinguished using the panel of 5'-methylthioadenosine, L-beta-aspartyl-L-serine, dehydroepiandrosterone sulfate, and N'-formylkynurenine (AUC=0.858). The metabolite panel comprising aspartyl-methionine, 7-methylinosine, and alpha-CEHC glucuronide could discriminate UTUC from BCa with hematuria with an AUC of 0.83. Fatty acid biosynthesis, purine metabolism, tryptophan metabolism, pentose and glucuronate interconversions, and arachidonic acid metabolism were dysregulated when comparing UC with HCs. PTGIS and BCHE, the genes related to the metabolism of prostaglandin I2 and myristic acid respectively, were significantly associated with the survival of BCa.

Discussion

Not only could LC-HRMS urine metabolomic investigations distinguish UC from HCs, but they could also identify UTUC from BCa. Additionally, urine metabolomics combined with transcriptomics can find out the potential aberrant genes in the metabolism.

Altered Glycosylation in Progression and Management of Bladder Cancer

Bladder cancer (BC) is the 10th most common malignancy worldwide, with an estimated 573,000 new cases and 213,000 deaths in 2020. Available therapeutic approaches are still unable to reduce the incidence of BC metastasis and the high mortality rates of BC patients. Therefore, there is a need to deepen our understanding of the molecular mechanisms underlying BC progression to develop new diagnostic and therapeutic tools. One such mechanism is protein glycosylation. Numerous studies reported changes in glycan biosynthesis during neoplastic transformation, resulting in the appearance of the so-called tumor-associated carbohydrate antigens (TACAs) on the cell surface. TACAs affect a wide range of key biological processes, including tumor cell survival and proliferation, invasion and metastasis, induction of chronic inflammation, angiogenesis, immune evasion, and insensitivity to apoptosis. The purpose of this review is to summarize the current information on how altered glycosylation of bladder cancer cells promotes disease progression and to present the potential use of glycans for diagnostic and therapeutic purposes.

Development of a novel pyroptosis-related LncRNA signature with multiple significance in acute myeloid leukemia

Background: Pyroptosis, a programmed cell death (PCD) with highly inflammatory form, has been recently found to be associated with the origin of hematopoietic malignancies. Long noncoding RNA (lncRNA) had emerged as an essential mediator to regulate gene expression and been involved in oncogenesis. However, the roles of pyroptosis-related lncRNA (PRlncRNA) in acute myeloid leukemia (AML) have not yet been completely clarified. Methods: We collected AML datasets from public databases to obtain PRlncRNA associated with survival and constructed a PRlncRNA signature using Lasso-Cox regression analysis. Subsequently, we employed RT-PCR to confirm its expression difference and internal training to further verify its reliability. Next, AML patients were classified into two subgroups by the median risk score. Finally, the differences between two groups in immune infiltration, enrichment analysis and drug sensitivity were further explored. Results: A PRlncRNA signature and an effective nomogram combined with clinicopathological variables to predict the prognosis of AML were constructed. The internal validations showed that the PRlncRNA risk score model was an accurate and productive indicator to predict the outcome of AML. Furthermore, this study indicated that higher inflammatory cell and immunosuppressive cells, and less sensitive to conventional chemotherapy drugs were highlighted in the high-risk group. Conclusion: Through comprehensive analysis of PRlncRNA model, our study may offer a valuable basis for future researches in targeting pyroptosis and tumor microenvironment (TME) and provide new measures for prevention and treatment in AML.

The Synthesis of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine Kinase (GNE), α-dystroglycan, and β-galactoside α-2,3-sialyltransferase 6 (ST3Gal6) By Skeletal Muscle Cell As a Response To Infection with Trichinella Spiralis

The Nurse cell of the parasitic nematode Trichinella spiralis is a unique structure established after genetic, morphological and functional modification of a small portion of invaded skeletal muscle fiber. Even if the newly developed cytoplasm of the Nurse cell is no longer contractile, this structure remains well integrated within the surrounding healthy tissue. Our previous reports suggested that this process is accompanied by an increased local biosynthesis of sialylated glycoproteins. In this work we examined the expressions of three proteins, functionally associated with the process of sialylation. The enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) is a key initiator of the sialic acid biosynthetic pathway. The α-dystroglycan was the only identified sialylated glycoprotein in skeletal muscles by now, bearing sialyl-α-2,3-Gal-β-1,4-Gl-cNAc-β-1,2-Man-α-1-O-Ser/Thr glycan. The third protein of interest for this study was the enzyme β-galactoside α-2,3-sialyltransferase 6 (ST3Gal6), which transfers sialic acid preferably onto Gal-β-1,4-GlcNAc as an acceptor, and thus it was considered as a suitable candidate for the sialylation of the α-dystroglycan. The expressions of the three proteins were analyzed by real time-PCR and immunohistochemistry on modified methacarn fixed paraffin tissue sections of mouse skeletal muscle samples collected at days 0, 14 and 35 post infection. According to our findings, the up-regulation of GNE was a characteristic of the early and the late stage of the Nurse cell development. Additional features of this process were the elevated expressions of α-dystroglycan and the enzyme ST3Gal6. We provided strong evidence that an increased local synthesis of sialic acids is a trait of the Nurse cell of T. spiralis, and at least in part due to an overexpression of α-dystroglycan. In addition, circumstantially we suggest that the enzyme ST3Gal6 is engaged in the process of sialylation of the major oligosaccharide component of α-dystroglycan.

Notch signaling pathway: a comprehensive prognostic and gene expression profile analysis in breast cancer

Breast cancer is a complex disease exhibiting a great degree of heterogeneity due to different molecular subtypes. Notch signaling regulates the differentiation of breast epithelial cells during normal development and plays a crucial role in breast cancer progression through the abnormal expression of the Notch up-and down-stream effectors. To date, there are only a few patient-centered clinical studies using datasets characterizing the role of Notch signaling pathway regulators in breast cancer; thus, we investigate the role and functionality of these factors in different subtypes using publicly available databases containing records from large studies. High-throughput genomic data and clinical information extracted from TCGA were analyzed. We performed Kaplan-Meier survival and differential gene expression analyses using the HALLMARK_NOTCH_SIGNALING gene set. To determine if epigenetic regulation of the Notch regulators contributes to their expression, we analyzed methylation levels of these factors using the TCGA HumanMethylation450 Array data. Notch receptors and ligands expression is generally associated with the tumor subtype, grade, and stage. Furthermore, we showed gene expression levels of most Notch factors were associated with DNA methylation rate. Modulating the expression levels of Notch receptors and effectors can be a potential therapeutic approach for breast cancer. As we outline herein, elucidating the novel prognostic and regulatory roles of Notch implicate this pathway as an essential mediator controlling breast cancer progression.

Sialyltransferases and Neuraminidases: Potential Targets for Cancer Treatment

Cancers are the leading cause of death, causing around 10 million deaths annually by 2020. The most common cancers are those affecting the breast, lungs, colon, and rectum. However, it has been noted that cancer metastasis is more lethal than just cancer incidence and accounts for more than 90% of cancer deaths. Thus, early detection and prevention of cancer metastasis have the capability to save millions of lives. Finding novel biomarkers and targets for screening, determination of prognosis, targeted therapies, etc., are ways of doing so. In this review, we propose various sialyltransferases and neuraminidases as potential therapeutic targets for the treatment of the most common cancers, along with a few rare ones, on the basis of existing experimental and in silico data. This compilation of available cancer studies aiming at sialyltransferases and neuraminidases will serve as a guide for scientists and researchers working on possible targets for various cancers and will also provide data about the existing drugs which inhibit the action of these enzymes.

Identification of glycogene signature as a tool to predict the clinical outcome and immunotherapy response in breast cancer

Background

Breast cancer is one of the most important diseases in women around the world. Glycosylation modification correlates with carcinogenesis and roles of glycogenes in the clinical outcome and immune microenvironment of breast cancer are unclear.

Methods

A total of 1297 breast cancer and normal cases in the TCGA and GTEx databases were enrolled and the transcriptional and survival information were extracted to identify prognostic glycogenes using Univariate Cox, LASSO regression, Multivariate Cox analyses and Kaplan-Meier method. The immune infiltration pattern was explored by the single sample gene set enrichment method. The HLA and immune checkpoint genes expression were also compared in different risk groups. The expressions of a glycogene MGAT5 as well as its products were validated by immunohistochemistry and western blotting in breast cancer tissues and cells.

Results

A 19-glycogene signature was identified to separate breast cancer patients into high- and low-risk groups with distinct overall survival rates (P < 0.001). Compared with the high-risk group, proportion of naive B cells, plasma cells and CD8⁺ T cells increased in the low-risk group (P < 0.001). Besides, expressions of HLA and checkpoint genes, such as CD274, CTLA4, LAG3 and TIGIT3, were upregulated in low-risk group. Additionally, highly expressed MGAT5 was validated in breast cancer tissues and cells. Downstream glycosylation products of MGAT5 were all increased in breast cancer.

Conclusions

We identified a 19-glycogene signature for risk prediction of breast cancer patients. Patients in the low-risk group demonstrated a higher immune infiltration and better immunotherapy response. The validation of MGAT5 protein suggests a probable pathway and target for the development and treatment of breast cancer.

Identification of ST3GAL5 as a prognostic biomarker correlating with CD8+ T cell exhaustion in clear cell renal cell carcinoma

Aberrant sialylation is frequently observed in tumor development, but which sialyltransferases are involved in this event are not well known. Herein, we performed comprehensive analyses on six ST3GAL family members, the α-2,3 sialyltransferases, in clear cell renal cell carcinoma (ccRCC) from public datasets. Only ST3GAL5 was consistently and significantly overexpressed in ccRCC (n = 791 in total), compared with normal kidney tissues. Its overexpression was positively correlated with tumor stage, grade, and the poor prognosis in ccRCC patients. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated the involvement of ST3GAL5 in tumor immunoregulation. Then we revealed that ST3GAL5 expression showed a positive correlation with CD8⁺ T cell infiltration, using multiple tools on TIMER2.0 web server. Notably, ST3GAL5 overexpression was further identified to be associated with expression signature of CD8⁺ T cell exhaustion in ccRCC samples from three datasets (n = 867 in total; r > 0.3, p < 0.001). In our own ccRCC cohort (n = 45), immunohistochemistry and immunofluorescence staining confirmed that ST3GAL5 overexpression was accompanied by high CD8⁺ T cell infiltration with the increased exhaustion markers. Altogether, ST3GAL5 as a promising prognostic biomarker with CD8⁺ T cell exhaustion in ccRCC is indicated.

Identification of hexosamine biosynthesis pathway as a novel prognostic signature and its correlation with immune infiltration in bladder cancer

Background: Urinary bladder cancer (UBC) is one of the common urological malignancies, lacking reliable biomarkers to predict clinical outcomes in UBC patients. Thus, it is needed to identify the novel diagnostic/prognostic biomarkers to stratify the high-risk UBC patients. As a shunt pathway of glycolysis, the hexosamine biosynthesis pathway (HBP) has been implicated in carcinogenesis. However, its prognostic value in UBC remains unclear.

Methods: The RNA sequencing and mRNA microarray datasets were downloaded from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus databases. The expression levels of five HBP genes were analyzed in normal and UBC samples, and their associations with stage, grade and survival were plotted. The performance of HBP risk group was evaluated by receiver-operating characteristics (ROC) curve. The HBP signature was generated by Gene Set Variation Analysis (GSVA) and its association with clinicopathological parameters and survival were analyzed. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were carried out to examine the potential biological functions of HBP using DAVID online tool. The infiltration estimation fraction of immune cells was performed using CIBERSORT-ABS algorithm. Gene set enrichment analysis (GSEA) was used to explore the potential function of HBP in tumor immunoregulation.

Results: Four HBP genes were upregulated in UBCs compared to normal tissues in TCGA-BLCA dataset. The upregulation of all five HBP genes was significantly associated with tumor grade and stage of UBC in three independent UBC datasets. The expression of HBP genes predicted poor clinical outcomes in UBC patients in both TCGA-BLCA and GSE13507 datasets. The high-risk group based on HBP genes showed a poor prognosis. Furthermore, HBP signature was positively associated with tumor grade and stage in TCGA-BLCA dataset and with tumor grade, stage, distal metastasis and poor survival in GSE13507 dataset. Interestingly, high-HBP signature group exhibited a high infiltration of immune cells, particularly the macrophage population.

Conclusion: We identified that HBP was a promising prognostic biomarker in UBC patients and strongly associated with immune infiltration.

Comprehensive landscape of the ST3GAL family reveals the significance of ST3GAL6-AS1/ST3GAL6 axis on EGFR signaling in lung adenocarcinoma cell invasion

Sialylation aberration has been implicated in lung cancer development by altering signaling pathways. Hence, it is urgent to identify key sialyltransferases in the development of lung adenocarcinoma (LUAD), which is a common malignant subtype of non-small cell lung cancer. Herein, by systematically investigating the expression levels of ST3GAL family members in several public databases, we consistently found the frequent downregulation of ST3GAL6 in LUAD samples. Its downregulation is significantly negatively associated with stage, and significantly reduced in proximal-proliferative molecular subtype and predicts poor clinical outcomes. By protein–protein interaction network analysis and validation, we found that ST3GAL6 deficiency promotes LUAD cell invasiveness with the activated EGFR/MAPK signaling, accompanied by the elevated expression levels of matrix metalloproteinases 2 and 9, which can be partially reversed by EGFR inhibitor, gefitinib. Additionally, the ST3GAL6 level was positively regulated by ST3GAL6-AS1, an antisense long non-coding RNA to its host gene. The downregulation of ST3GAL6-AS1 also heralds a worse prognosis in LUAD patients and promotes LUAD cell invasiveness, recapitulating the function of its host gene, ST3GAL6. Altogether, ST3GAL6-AS1-regulated ST3GAL6 is a frequently downregulated sialyltransferase in LUAD patients and negatively regulates EGFR signaling, which can serve as a promising independent prognostic marker in LUAD patients.

An Immunosenescence-Related Gene Signature to Evaluate the Prognosis, Immunotherapeutic Response, and Cisplatin Sensitivity of Bladder Cancer

Immunosenescence refers to the immune system undergoing a series of degenerative changes with advancing age and is tightly associated with the initiation and progression of cancers. However, the immunosenescence-related genes as critical biomarkers for bladder cancer (BLCA) have not been systematically analyzed. We retrieved the immunosenescence-related genes from the public database and verified their association with hallmarks of immunosenescence based on The Cancer Genome Atlas (TCGA) cohort. Through gene pairing, Lasso, and univariate Cox regression, an 8-gene pair model was constructed to evaluate the overall survival of BLCA, which was then validated in the training cohort (P < 0.001, n = 396), two external validation cohorts (P < 0.05, n = 165; P < 0.001, n = 224), and local samples (P < 0.05, n = 10). We also downloaded the clinical information and gene expression matrices of other 32 different cancers from TCGA. The established model showed significant predictive value for the prognosis in 15 cancers (P < 0.05). The risk model could also serve as a promising predictor for immunotherapeutic response, which has been verified by the TIDE algorithm (P < 0.05), IMvigor210 dataset (P < 0.01, n = 298), and other two datasets correlated with immunotherapy (P < 0.05, n = 56; P = 0.17, n = 27). The TCGA dataset, in vitro cell experiments, and pan-cancer analysis displayed that the gene signature was associated with cisplatin sensitivity (P < 0.05). Overall, we proposed a novel immunosenescence-related gene signature to predict prognosis, immunotherapeutic response, and cisplatin sensitivity of BLCA, which were validated in different independent cohorts, local samples, and pan-cancer analyses.

The novel role of circular RNA ST3GAL6 on blocking gastric cancer malignant behaviours through autophagy regulated by the FOXP2/MET/mTOR axis

Gastric cancer (GC) ranks third in mortality among all cancers worldwide. Circular RNAs (circRNAs) play an important role in the occurrence and development of gastric cancer. Forkhead box P2 (FOXP2), as a transcription factor, is closely associated with the development of many types of tumours. However, the regulatory network between FOXP2 and circRNAs remains to be explored. In our study, circST3GAL6 was significantly downregulated in GC and was associated with poor prognosis in GC patients. Overexpression of circST3GAL6 inhibited the malignant behaviours of GC cells, which was mediated by inducing apoptosis and autophagy. In addition, we demonstrated that circST3GAL6 regulated FOXP2 through the mir-300 sponge. We further found that FOXP2 inhibited MET Proto-Oncogene (MET), which was the initiating factor that regulated the classic AKT/mTOR pathway of autophagy. In conclusion, our results suggested that circST3GAL6 played a tumour suppressive role in gastric cancer through miR-300/FOXP2 axis and regulated apoptosis and autophagy through FOXP2-mediated transcriptional inhibition of the MET axis, which may become a potential target for GC therapy.

The Distinct Roles of Sialyltransferases in Cancer Biology and Onco-Immunology

Aberrant glycosylation is a key feature of malignant transformation. Hypersialylation, the enhanced expression of sialic acid-terminated glycoconjugates on the cell surface, has been linked to immune evasion and metastatic spread, eventually by interaction with sialoglycan-binding lectins, including Siglecs and selectins. The biosynthesis of tumor-associated sialoglycans involves sialyltransferases, which are differentially expressed in cancer cells. In this review article, we provide an overview of the twenty human sialyltransferases and their roles in cancer biology and immunity. A better understanding of the individual contribution of select sialyltransferases to the tumor sialome may lead to more personalized strategies for the treatment of cancer.

Glycation Interferes with the Expression of Sialyltransferases in Meningiomas

Meningiomas are the most common non-malignant intracranial tumors and prefer, like most tumors, anaerobic glycolysis for energy production (Warburg effect). This anaerobic glycolysis leads to an increased synthesis of the metabolite methylglyoxal (MGO) or glyoxal (GO), which is known to react with amino groups of proteins. This reaction is called glycation, thereby building advanced glycation end products (AGEs). In this study, we investigated the influence of glycation on sialylation in two meningioma cell lines, representing the WHO grade I (BEN-MEN-1) and the WHO grade III (IOMM-Lee). In the benign meningioma cell line, glycation led to differences in expression of sialyltransferases (ST3GAL1/2/3/5/6, ST6GAL1/2, ST6GALNAC2/6, and ST8SIA1/2), which are known to play a role in tumor progression. We could show that glycation of BEN-MEN-1 cells led to decreased expression of ST3Gal5. This resulted in decreased synthesis of the ganglioside GM3, the product of ST3Gal5. In the malignant meningioma cell line, we observed changes in expression of sialyltransferases (ST3GAL1/2/3, ST6GALNAC5, and ST8SIA1) after glycation, which correlates with less aggressive behavior.

CBX7 suppresses urinary bladder cancer progression via modulating AKR1B10-ERK signaling

The chromobox (CBX) proteins mediate epigenetic gene silencing and have been implicated in the cancer development. By analyzing eight CBX family members in TCGA dataset, we found that chromobox 7 (CBX7) was the most strikingly downregulated CBX family member in urinary bladder cancer (UBC), as compared to normal tissues. Though dysregulation of CBX7 has been reported in multiple cancers, its specific role and clinical relevance in UBC remain unclear. Herein, we found that frequent downregulation of CBX7 in UBC specimens, which was due to its promoter hypermethylation, was correlated with poor prognosis. The ectopic expression of CBX7 suppressed UBC cell proliferation, migration, invasion, and cancer stemness, whereas CBX7 depletion promoted cancer cell aggressiveness. Importantly, CBX7 overexpression in UBC cells inhibited tumorigenicity, whereas CBX7 depletion promoted the tumor development, indicating its tumor-suppressive role in UBC. Using RNA-seq and chromosome immunoprecipitation (ChIP) assays, we identified aldo-keto reductase family 1 member 10 (AKR1B10) as a novel downstream target of CBX7, which was negatively modulated by CBX7 in a PRC1-dependent manner and involved in stimulating ERK signaling. Consistently, AKR1B10 overexpression induced cancer cell aggressiveness, whereas suppression of AKR1B10 by siRNA or its small molecular inhibitor, oleanolic acid, reversed the CBX7 deficiency-induced cellular effects. AKR1B10 overexpression was negatively associated with CBX7 downregulation and predicted poor clinical outcomes in UBC patients. Taken together, our results indicate that CBX7 functions as a tumor suppressor to downregulate AKR1B10 and further inactivates ERK signaling. This CBX7/AKR1B10/ERK signaling axis may provide a new therapeutic strategy against UBC.

Aberrant Sialylation in Cancer: Biomarker and Potential Target for Therapeutic Intervention?

Simple Summary

Sialylation is a post-translational modification that consists in the addition of sialic acid to growing glycan chains on glycoproteins and glycolipids. Aberrant sialylation is an established hallmark of several types of cancer, including breast, ovarian, pancreatic, prostate, colorectal and lung cancers, melanoma and hepatocellular carcinoma. Hypersialylation can be the effect of increased activity of sialyltransferases and results in an excess of negatively charged sialic acid on the surface of cancer cells. Sialic acid accumulation contributes to tumor progression by several paths, including stimulation of tumor invasion and migration, and enhancing immune evasion and tumor cell survival. In this review we explore the mechanisms by which sialyltransferases promote cancer progression. In addition, we provide insights into the possible use of sialyltransferases as biomarkers for cancer and summarize findings on the development of sialyltransferase inhibitors as potential anti-cancer treatments.

Abstract

Sialylation is an integral part of cellular function, governing many biological processes including cellular recognition, adhesion, molecular trafficking, signal transduction and endocytosis. Sialylation is controlled by the levels and the activities of sialyltransferases on glycoproteins and lipids. Altered gene expression of these enzymes in cancer yields to cancer-specific alterations of glycoprotein sialylation. Mounting evidence indicate that hypersialylation is closely associated with cancer progression and metastatic spread, and can be of prognostic significance in human cancer. Aberrant sialylation is not only a result of cancer, but also a driver of malignant phenotype, directly impacting key processes such as tumor cell dissociation and invasion, cell-cell and cell-matrix interactions, angiogenesis, resistance to apoptosis, and evasion of immune destruction. In this review we provide insights on the impact of sialylation in tumor progression, and outline the possible application of sialyltransferases as cancer biomarkers. We also summarize the most promising findings on the development of sialyltransferase inhibitors as potential anti-cancer treatments.