ST6GalNAcII mediates the invasive properties of breast carcinoma through PI3K/Akt/NF-κB signaling pathway

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.

Depletion of ST6GALNACIII retards A549 non-small cell lung cancer cell proliferation by downregulating transferrin receptor protein 1 expression

Alterations in sialylation of terminal residues of glycoproteins have been implicated in forming tumor-associated glycans. ST6GALNAC transfers sialyl moiety to N-acetylgalactosamine residue via α2,6 linkage. Although the oncogenic characteristics of ST6GALNACI or II have been demonstrated in various cancer cells, the impact of ST6GALNACIII on tumor progression remains undefined. In this study, we evaluated the effect of ST6GALNACIII knockdown on the growth of A549 non-small cell lung cancer cells. ST6GALNACIII depletion resulted in significant retardation in growth of A549 cells under various culture conditions, including collagen-supported 3D culture and anchorage-independent soft agar culture conditions. Liquid chromatography with tandem mass spectrometry revealed that two glycopeptides of transferrin receptor protein 1 (TFR1) containing N-acetylhexosamine-sialic acid were not detected in ST6GALNACIII-depleted A549 cells compared with control cells. Subsequent lectin binding assay, western blotting, and real-time RT-PCR indicated that TFR1 sialylation was not significantly changed, but TFR1 protein and mRNA expressions were decreased after ST6GALNACIII knockdown. However, cell growth retardation by ST6GALNACIII knockdown was partially rescued by TFR1 overexpression. Additionally, TFR1 mRNA degradation was accelerated following ST6GALNACIII knockdown with concomitant reduction in mRNA levels of iron regulatory protein 1 and 2, the upstream regulators of TFR1 mRNA stability. Therefore, our results indicated an important role of ST6GALNACIII in promoting A549 cell growth through quantitative regulation of TFR1 expression and provided therapeutic implications for ST6GALNACIII targeting in tumor growth suppression in vivo.

Role of Sulfur Metabolism Gene and High-Sulfur Gene Expression in Wool Growth Regulation in the Cashmere Goat

Sulfur, an essential mineral element for animals, mainly exists in the form of organic sulfur-containing amino acids (SAAs), such as cystine, methionine, and cysteine, within the body. The content, form, and structure of sulfur play an important role in determining the wool fiber quality. In addition, keratin-associated proteins, one of the most crucial wool fiber components, are rich in SAAs. However, sulfur metabolism from the blood to the skin and hair follicles remains unclear. In this study, we analyzed high-sulfur protein gene and sulfur metabolism genes in the cashmere goat and explored the effects of melatonin on their expression. In total, 53 high-sulfur protein genes and 321 sulfur metabolism genes were identified. We found that high-sulfur protein genes were distributed in the 3-4 and 144M regions of chromosome 1 and the 40-41M region of chromosome 19 in goats. Moreover, all year round, allele-specific expression (ASE) is higher in the 40-41M region of chromosome 19 than in the other regions. Total of 47 high-sulfur protein genes showed interaction with transcription factors and cofactors with ASE. These transcription factors and cofactors were inhibited after melatonin implantation. The network analysis revealed that melatonin may activate the sulfur metabolism process via the regulation of the genes related to cell energy metabolism and cell cycle in the skin, which provided sufficient SAAs for wool and cashmere growth. In conclusion, our findings provide a new insight into wool growth regulation by sulfur metabolism genes and high-sulfur protein genes in cashmere goats.

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.

Advances in molecular mechanisms of drugs affecting abnormal glycosylation and metastasis of breast cancer

Breast cancer remains the leading cause of cancer-related death among women worldwide, and its incidence is also increasing. High recurrence rate and metastasis rate are the key causes of poor prognosis and death. It is suggested that abnormal glycosylation plays an important role in the growth, invasion, metastasis and resistance to therapy of breast cancer cells. Meanwhile, it can be used as the biomarkers for the early detection and prognosis of breast cancer and the potential attractive targets for drug treatment. However, only a few attentions have been paid to the molecular mechanism of abnormal glycosylation in the epithelial-mesenchymal transition (EMT) of breast cancer cells and the related intervention of drugs. This manuscript thus investigated the relationship between abnormal glycosylation, the EMT, and breast cancer metastasis. Then, the process of abnormal glycosylation, the classification and their molecular regulatory mechanisms of breast cancer were analyzed in detail. Last, potential drugs are introduced in different categories, which are expected to reverse or intervene the abnormal glycosylation of breast cancer. This review is conducive to an in-depth understanding of the metastasis and drug resistance of breast cancer cells, which will provide new ideas for the clinical regulation of glycosylation and related drug treatments in breast cancer.

Quantitative Analysis of Proteome in Non-functional Pituitary Adenomas: Clinical Relevance and Potential Benefits for the Patients

Background: Non-functional pituitary adenoma (NFPA) is a common tumor that occurs in the pituitary gland, and generally without any symptoms at its early stage and without clinical elevation of hormones, which is commonly diagnosed when it grows up to compress its surrounding tissues and organs. Currently, the pathogenesis of NFPA has not been clarified yet. It is necessary to investigate molecular alterations in NFPA, and identify reliable biomarkers and drug therapeutic targets for effective treatments. Methods: Tandem mass tags (TMT)-based quantitative proteomics was used to identify and quantify proteins in NFPAs. GO and KEGG enrichment analyses were used to analyze the identified proteins. Differentially expressed genes (DEGs) between NFPA and control tissues were obtained from GEO datasets. These two sets of protein and gene data were analyzed to obtain overlapped molecules (genes; proteins), followed by further GO and KEGG pathway analyses of these overlapped molecules, and molecular network analysis to obtain the hub molecules with Cytoscape. Two hub molecules (SRC and AKT1) were verified with Western blotting. Results: Totally 6076 proteins in NFPA tissues were identified, and 3598 DEGs between NFPA and control tissues were identified from GEO database. Overlapping analysis of 6076 proteins and 3598 DEGs obtained 1088 overlapped molecules (DEGs; proteins). KEGG pathway analysis of 6076 proteins obtained 114 statistically significant pathways, including endocytosis, and spliceosome signaling pathways. KEGG pathway analysis of 1088 overlapped molecules obtained 52 statistically significant pathways, including focal adhesion, cGMP-PKG pathway, and platelet activation signaling pathways. These pathways play important roles in cell energy supply, adhesion, and maintenance of the tumor microenvironment. According to the association degree in Cytoscape, ten hub molecules (DEGs; proteins) were identified, including GAPDH, ALB, ACACA, SRC, ENO2, CALM1, POTEE, HSPA8, DECR1, and AKT1. Western-blotting analysis confirmed the upregulated expressions of SRC and PTMScan experiment confirmed the increased levels of pAKT1, in NFPAs compared to controls. Conclusions: This study established the large-scale quantitative protein profiling of NFPA tissue proteome. It offers a basis for subsequent in-depth proteomics analysis of NFPAs, and insight into the molecular mechanism of NFPAs. It also provided the basic data to discover reliable biomarkers and therapeutic targets for NFPA patients.

TMT-based quantitative proteomics revealed follicle-stimulating hormone (FSH)-related molecular characterizations for potentially prognostic assessment and personalized treatment of FSH-positive non-functional pituitary adenomas

BACKGROUND

Non-functional pituitary adenoma (NFPA) is highly heterogeneous with different hormone expression subtypes. Of them, follicle-stimulating hormone (FSH)-positive expression is an important subtype of NFPAs. It is well-known that FSH exerted its functions through binding its receptor. However, the expression rate of FSH receptor was significantly higher in aggressive pituitary adenomas. This study aimed to investigate the molecular characteristics of FSH-positive NFPAs for effective stratification of patient, target treatment, prognostic assessment, and personalized treatment of FSH-positive NFPAs.

METHODS

Tandem mass tag (TMT)-based quantitative proteomics was used to investigate differentially expressed proteins (DEPs) between FSH-positive and negative NFPAs. Gene ontology and KEGG pathway enrichment analyses were used to analyze the DEPs. Differentially expressed genes (DEGs) between invasive and non-invasive NFPAs from GEO database were analyzed with pathway enrichment analysis. Protein-protein interaction (PPI) networks were constructed based on DEPs in excetral cellular matrix (ECM)-receptor interaction, focal adhesion, and PI3K-Akt pathways. Cytoscape was used to obtain most significant modules. Western blot was used to validate the expressions of upregulated proteins (ITGA1, ITGA6, and ITGB4), the expression and phosphorylated status of Akt in PI3K-Akt pathway, and the expression of FSH receptors in FSH-positive relative to negative NFPAs.

RESULTS

A total of 594 DEPs (374 upregulated and 220 downregulated) were identified between FSH-positive and negative NFPAs. Nineteen KEGG pathway networks were identified to involve DEPs, and reveal molecular differences between FSH-positive and negative NFPAs, including three important pathways that were significantly associated with tumor invasiveness and aggressiveness: ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathways. Further, focal adhesion pathway was also confirmed with invasiveness-related NFPA DEG data that were derived from GEO database. Moreover, the significantly upregulated DEPs (ITGA1, ITGA6, and ITGB4) that were associated with tumor invasiveness and aggressiveness were confirmed by immunoaffinity analysis in FSH-positive vs. negative NFPAs. Also, the phosphorylation level but not its expression level of AKT in PI3K-AKT signaling was significantly increased, and the expression level of FSH receptor was significantly increased in FSH-positive relative to negative NFPAs. Also, overlapping analysis of 594 DEPs and 898 DEGs revealed 45 invasiveness-related DEPs, including 11 upregulated DEPs (ITGA6, FARP1, PALLD, PPBP, LIMA1, SCD, UACA, BAG3, CLU, PLEC, and GATM) that were also upregulated genes in invasive NFPAs, and 8 downregulated DEPs (ALCAM, HP, FSTL4, IL13RA2, NPTX2, DPP6, CRABP2, and SLC27A2) that were also downregulated genes in invasive NFPAs.

CONCLUSIONS

FSH-positive expression was an important NFPA subtype. It was the first time for this study to reveal FSH-related proteomic variations and the corresponding molecular network alterations in FSH-positive relative to negative NFPAs. Also, three signaling pathways (ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathways) and involved upregulated proteins (ITGA1, ITGA6, ITGB4, pAKT, and FSHR) were significantly associated with tumor invasiveness and aggressiveness, and a set of invasiveness-related DEPs were identified with overlapping analysis of 594 DEPs in FSH-positive vs. negative NFPAs and 898 DEGs in invasive vs. non-invasive NFPAs. These findings offered the scientific evidence to in-depth understand molecular characteristics of FSH-positive NFPAs, and effectively stratify the post-surgery patients for personalized prognostic assessment and targeted treatment of FSH-positive NFPAs.

Glycosylation and its implications in breast cancer

Introduction: For decades, the role of glycans and glycoproteins in the progression of breast cancer and other cancers have been evaluated. Through extensive studies focused on elucidating the biological functions of glycosylation, researchers have been able to implicate alterations in these functions to tumor formation and metastasis. Areas covered: In this review, we summarize how changes in glycosylation are associated with tumorigenesis, with emphasis on breast cancers. An overview of the changes in N-linked and O-linked glycans associated with breast cancer tumors and biofluids are described. Recent advances in glycomics are emphasized in the context of continuing to decipher the glycosylation changes associated with breast cancer progression. Expert opinion: While changes in glycosylation have been studied in breast cancer for many years, the clinical relevance of these studies has been limited. This reflects the inherent biological and clinical heterogeneity of breast cancers. Glycomics analysis lags behind the advances in genomics and proteomics, but new approaches are emerging. A summary of known glycosylation changes associated with breast cancer is necessary to implement new findings in the context of clinical outcomes and therapeutic strategies. A better understanding of the dynamics of tumor and immune glycosylation is critical to improving emerging immunotherapeutic treatments.

Elevated EGFL6 modulates cell metastasis and growth via AKT pathway in nasopharyngeal carcinoma

Epidermal growth factor-like domain multiple 6 (EGFL6) is a secreted protein, regulates maintenance and metastasis of cancer cells. Nevertheless, how EGFL6 participates in the progression and tumorigenesis of nasopharyngeal carcinoma (NPC) remains unclear. In our study, EGFL6 was detected highly expressed in 20 NPC tissues compared with normal tissues by IHC assay. Then, the level of EGFL6 in NPC serum and NPC cells was explored through enzyme-linked immunosorbent assay and western blot, the results consistent with IHC. More interestingly, EGFL6 accelerated the migration and growth of NPC in vitro assays. Considering the mechanism of migration, NPC cells were cultured with AKT activator, revealing EGFL6 facilitated the progression of NPC via AKT. Moreover, the same effect of EGFL6 in promoting NPC growth was proved in nude mice. Furthermore, heat-shock zebrafish model was established with EGFL6 overexpression. Then, CNE2 cells were injected into the model and cells mass was observed, showing that EGFL6 enhanced the migration and metastasis of NPC. Currently, as the prognosis of NPC is severely affected by distant metastasis, it might be a new therapeutic target toward EGFL6. Taken together, our results suggested that EGFL6 acts as a potential positive regulator in the migration and proliferation of NPC.

Quantitative Analysis of Sex-Hormone-Binding Globulin Glycosylation in Liver Diseases by Liquid Chromatography-Mass Spectrometry Parallel Reaction Monitoring

Sex-hormone-binding globulin (SHBG) is a liver-secreted glycoprotein and a major regulator of steroid distribution. It has been reported that the serum concentration of SHBG changes in liver disease. To explore the involvement of SHBG in liver disease of different etiologies in greater detail, we developed a sensitive and selective liquid chromatography-mass spectrometry parallel reaction monitoring workflow to achieve quantitative analysis of SHBG glycosylation microheterogeneity. The method uses energy-optimized "soft" fragmentation to extract informative Y ions for maximal coverage of glycoforms and their quantitative comparisons. A total of 15 N-glycoforms of two N-glycosites and 3 O-glycoforms of 1 O-glycosite of this low-abundance serum protein were simultaneously analyzed in the complex samples. At the same time, we were able to partially resolve linkage isoforms of the fucosylated glycoforms and to identify and quantify SHBG N-glycoforms that were not previously reported. The results show that both core and outer-arm fucosylation of the N-glycoforms increases with liver cirrhosis but that a further increase of fucosylation is not observed with hepatocellular carcinoma (HCC). In contrast, the α-2-6 sialylated glycoform of the O-glycopeptide of SHBG increases in liver cirrhosis, and a significant 2-fold further increase is observed in HCC. In general, we do not find a significant contribution of different liver disease etiologies to the observed changes in glycosylation; however, elevation of the newly reported HexNAc(4)Hex(6) N-glycoform is associated with alcoholic liver disease.

LncRNA HCP5 promotes follicular thyroid carcinoma progression via miRNAs sponge

Long non-coding RNAs (lncRNAs), which are important functional regulators in cancer, have received increased attention in recent years. In this study, next-generation sequencing technology was used to identify aberrantly expressed lncRNAs in follicular thyroid carcinoma (FTC). The long non-coding RNA–HLA complex P5 (HCP5) was found to be overexpressed in FTC. The results of the qPCR analysis were consistent with the sequencing results. In addition, functional experiments showed that overexpression of HCP5 can promote the proliferation, migration, invasiveness and angiogenic ability of FTC cells. Furthermore, according to the sequencing results, HCP5 and alpha-2, 6-sialyltransferase 2 (ST6GAL2) were co-expressed in FTC. We hypothesised that ST6GAL2 may be regulated by HCP5, which would in turn mediate the activity of FTC cells. Through qPCR, immunostaining analyses and functional experiments, we determined that the expression of HCP5 was elevated and was correlated with the levels of ST6GAL2 in FTC tissues and cells. Mechanistic experiments showed that HCP5 functions as a competing endogenous RNA (ceRNA) and acts as a sponge for miR-22-3p, miR-186-5p and miR-216a-5p, which activates ST6GAL2. In summary, our study revealed that HCP5 is a tumour regulator in the development of FTC and that it may contribute to improvement of FTC diagnosis and therapy.

Engineered CAR T Cells Targeting the Cancer-Associated Tn-Glycoform of the Membrane Mucin MUC1 Control Adenocarcinoma

Genetically modified T cells expressing chimeric antigen receptors (CARs) demonstrate robust responses against lineage restricted, non-essential targets in hematologic cancers. However, in solid tumors, the full potential of CAR T cell therapy is limited by the availability of cell surface antigens with sufficient cancer-specific expression. The majority of CAR targets have been normal self-antigens on dispensable hematopoietic tissues or overexpressed shared antigens. Here, we established that abnormal self-antigens can serve as targets for tumor rejection. We developed a CAR that recognized cancer-associated Tn glycoform of MUC1, a neoantigen expressed in a variety of cancers. Anti-Tn-MUC1 CAR T cells demonstrated target-specific cytotoxicity and successfully controlled tumor growth in xenograft models of T cell leukemia and pancreatic cancer. These findings demonstrate the therapeutic efficacy of CAR T cells directed against Tn-MUC1 and present aberrantly glycosylated antigens as a novel class of targets for tumor therapy with engineered T cells.

Upregulation of microRNA-135b and microRNA-182 promotes chemoresistance of colorectal cancer by targeting ST6GALNAC2 via PI3K/AKT pathway

MicroRNAs (miRNAs) are increasingly involved in the development of drug resistance, including 5-fluorouracil (5-FU) resistance in colorectal cancer (CRC). Aberrant sialylation is correlated with human CRC. The study was to explore whether miR-135b and miR-182 modulated 5-FU chemoresistance of CRC by targeting ST6GALNAC2 via PI3K/AKT pathway. MiR-135b and miR-182 were found to be up-regulated in CRC tissues and 5-FU resistant CRC cell lines. Forced miR-135b and miR-182 expression also affected ST6GALNAC2 levels. Using reporter-gene assay, ST6GALNAC2 was identified as direct target of miR-135b and miR-182, while ST6GALNAC2 expression exhibited patterns opposite to that of miR-135b and miR-182 in CRC samples and cell lines. Interestingly, up-regulation of miR-135b or miR-182 increased drug resistance and proliferation, but decreased apoptosis in 5-FU resistant CRC cell lines. Suppression of these miRNAs implicated an inverse function, while altered expression of ST6GALNAC2 mediated CRC progression upon transfection with miR-135b/-182 mimic or inhibitor. Furthermore, miR-135b and miR-182 were clarified to regulate the activity of phosphoinositide-3 kinase (PI3K)/AKT pathway. Inhibition of the PI3K/AKT pathway enhanced the chemosensitivity to 5-FU in HCT-8/5-FU and LoVo/5-FU. Taken together, miR-135b and miR-182 may reverse the resistance to 5-FU in CRC cells by targeting ST6GALNAC2 via PI3K/AKT pathway, which render potential chemotherapy targets for the treatment of CRC.

MiR-106b and miR-93 regulate cell progression by suppression of PTEN via PI3K/Akt pathway in breast cancer

Accumulating evidences have revealed that dysregulated microRNAs (miRNAs) involve in the tumorigenesis, progression and even lead to poor prognosis of various carcinomas, including breast cancer. MiRNA-106b-5p (miR-106b) and miRNA-93-5p (miR-93) levels were confirmed to be significantly upregulated in breast cancer clinical samples (n=36) and metastatic cell line (MDA-MB-231) compared with those in the paired adjacent tissues and normal breast epithelial cell line (MCF-10A). Moreover, further research stated that the capability of migration, invasion and proliferation changed along with the altered expression of miR-106b and miR-93 in breast cancer. PTEN, the tumor-suppressor gene, was discovered to be reduced in breast cancer tissues or MDA-MB-231 cells with high levels of miR-106b and miR-93, which were inversely expressed in PTEN overexpression tissues or cells. Based on the investigation, miR-106b and miR-93 induced the migration, invasion and proliferation and simultaneously enhanced the activity of phosphatidylinositol-3 kinase (PI3K)/Akt pathway of MCF-7 cells, which could be blocked by upregulation of PTEN. Furthermore, suppression of PTEN reversed the function induced by anti-miR-106b and anti-miR-93 in MDA-MB-231 cells, indicating that PTEN was directly targeted by these miRNAs and acted as the potential therapeutic target for breast cancer therapy. In short, reductive PTEN mediated by miR-106b and miR-93 promoted cell progression through PI3K/Akt pathway in breast cancer.

Sialyltransferase ST3GAL6 mediates the effect of microRNA-26a on cell growth, migration, and invasion in hepatocellular carcinoma through the protein kinase B/mammalian target of rapamycin pathway

Aberrant sialylation profiles on the cell surface have been recognized for their potential diagnostic value in identifying the regulation of tumor properties in several cancers, including hepatocellular carcinoma (HCC). Recently, increasing evidence has suggested that the deregulation of microRNA (miRNA) is a common feature in human cancers. In this study, we found obvious upregulation of sialyltransferase ST3GAL6 both in HCC cell lines and in tissue samples. The altered expression of ST3GAL6 was found to correlate with cell proliferation, migration, and invasion ability in HCC. Further investigation showed that miR‐26a negatively regulated ST3GAL6, inducing the suppression of cell proliferation, migration, and invasion in vitro. Moreover, we identified the protein kinase B/mammalian target of rapamycin (Akt/mTOR) pathway as the target of ST3GAL6 based on Western blot analysis. Analysis of a xenograft mouse model showed that miR‐26a significantly reduced tumor growth by suppressing activation of the Akt/mTOR pathway by directly targeting ST3GAL6. In conclusion, these data indicate that ST3GAL6 promotes cell growth, migration, and invasion and mediates the effect of miR‐26a through the Akt/mTOR signaling pathway in HCC.

Functional roles of sialylation in breast cancer progression through miR-26a/26b targeting ST8SIA4

Sialylation is one of the altered glycosylation patterns associated with cancer progression. In this study, we investigated the N-glycan profiles of breast cancer patients and cell lines to reveal sialylation associated with breast cancer progression, and provided new evidences of miRNA-mediated sialylation. MALDI-TOF MS analysis revealed that N-glycans found in breast cancer tissues and breast cancer cell MDA-MB-231 featured increased levels of sialylation compared with adjacent tissues and normal breast epithelial cell MCF-10A. The expressional profiles of 20 sialyltransferase genes were then analyzed and found significantly different comparing breast cancer samples with adjacent tissues, and two breast cancer cell lines MDA-MB-231 and MCF-7 with different metastatic potential and MCF-10A cells. Tumor tissues and highly metastatic breast cancer cell line MDA-MB-231 exhibited higher levels of ST8SIA4. Knocking down ST8SIA4 in breast cancer cell lines significantly inhibited their malignant behaviors including cell proliferation and invasion in a sialyltransferase-dependent manner. By applying bioinformatic approaches for the prediction of miRNA targeting 3′-UTR of ST8SIA4, we identified ST8SIA4 as one of the miR-26a/26b-targeted genes. Further data analysis revealed the inversely related expression of ST8SIA4 and miR-26a/26b in breast cancer cells, tumor tissues and corresponding adjacent tissues. The ability of miR-26a/26b to interact specifically with and regulate the 3′-UTR of ST8SIA4 was demonstrated via a luciferase reporter assay. The forced expression of miR-26a/26b was able to induce a decrease of ST8SIA4 level and also to affect breast cancer cells progression, while altered expression of ST8SIA4 in breast cancer cells modulated progression upon transfection with miR-26a/26b mimics or inhibiter. Taken together, these results indicate that changes in the glycosylation patterns and sialylation levels may be useful markers of the progression of breast cancer, as well as miR-26a/26b may be widely involved in the regulation of sialylation machinery by targeting ST8SIA4.

Silencing of ST6GalNAc I suppresses the proliferation, migration and invasion of hepatocarcinoma cells through PI3K/AKT/NF-κB pathway

ST6GalNAc I is the major Sialyl-Tn antigen (STn) synthase that is highly correlated with tumor invasion and metastasis. However, the roles and molecular mechanisms by which ST6GalNAc I mediates the malignant phenotypes of hepatocarcinoma cells still remain poorly unknown. In this study, we investigated the expression of STn and ST6GalNAc I in mouse hepatocarcinoma cell lines Hca-F, Hca-P, and Hepa1-6, which have different metastatic potential, as compared with normal mouse liver cell line IAR-20. The results showed that the expression of ST6GalNAc I and STn in Hca-F and Hca-P cells was much higher than that in Hepa1-6 and IAR20 cells. Knockdown of ST6GalNAc I by shRNA in Hca-F cells significantly decreased the expression of STn and inhibited the growth of tumor cells in vitro and in vivo. This reduction of ST6GalNAc I expression also led to the decreased migration and invasion of Hca-F cells. Furthermore, we found that ST6GalNAc I knockdown inhibited the expression levels of PI3k, p-Akt473, p-Akt308, NF-κB, and their downstream molecules. Together, our results suggest a role of ST6GalNAc I in promoting the growth and invasion of hepatocarcinoma cells through regulating PI3K/AKT signaling, and ST6GalNAc I might be a promising marker for the prognosis and therapy of hepatocarcinoma.

ST6GalNAcII mediates tumor invasion through PI3K/Akt/NF-κB signaling pathway in follicular thyroid carcinoma

Altered sialylation, closely associated with tumor progression and metastasis, has been implicated in human thyroid carcinoma. The present study investigated the alteration in expression of ST6GalNAcII involved in invasion and to clarify the possible mechanism of ST6GalNAcII in the metastasis process in human follicular thyroid carcinoma cell lines. Using real-time PCR, western blot and IHC analysis, ST6GalNAcII differed in three follicular thyroid cancer cell lines (FTC133, primary and FTC238, lung metastasis). It also showed differential expression in follicular thyroid carcinoma and tissue specimens. In addition, we analyzed the PI3K/Akt signaling pathway. The altered expression of ST6GalNAcII corresponded to changed invasive phenotype of FTC-238 and FTC-133 cells in vitro and in vivo. Further studies showed that regulating ST6GalNAcII expression markedly modulated the activity of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Targeting the PI3K/Akt pathway by its specific inhibitor LY294002, or by Akt small interfering RNA (siRNA) resulted in reduced capacity in invasion of FTC-238. In conclusion, taken together, our results imply that ST6GalNAcII activated the invasion in follicular thyroid cancer cells through regulating the activity of PI3K/Akt pathway.

Phyllodes tumor of the breast: role of Axl and ST6GalNAcII in the development of mammary phyllodes tumors

Phyllodes tumor exhibits an aggressive growth. The expression of many biological markers has been explored to discriminate between different grades of phyllodes tumor and to predict their behavior. The purpose of this study was to evaluate the implications of Axl and ST6GalNAcII in phyllodes tumors. Real-time PCR, Western blot, and immunohistochemical were used to analyze differential expression of ST6GalNAcII and Axl in phyllodes tumor (PT) cell lines and tissue specimens. RNAi assay, ECM invasion assay, and tumorigenicity assay were used to analyze the altered expression of ST6GalNAcII gene effects on the expression of Axl and invasive ability of phyllodes tumor cells in vitro and in vivo. Compared to benign tumors, borderline and malignant ones showed a remarkable increase in mRNA levels of Axl and ST6GalNAcII gene, and it was higher in malignant tumor cells than in borderline tumor cells. When ST6GalNAcII was silenced, compared to the control, the expression level of Axl was significantly reduced in malignant tumor cell transfectants and knockdown of ST6GalNAcII gene significantly inhibited invasive activity in malignant tumor cells. The high expression of ST6GalNAcII and Axl was significantly correlated with tumor grade and distance metastasis by immunohistochemical analysis. Axl and ST6GalNAcII expression increases with increasing tumor grade in mammary phyllodes tumors. ST6GalNAc II might be participated in the glycosylation of Axl, and this Axl glycosylation may mediate the tumorigenicity, invasion, and distant metastasis of PT cells.