Potentiation of epidermal growth factor-mediated oncogenic transformation by sialidase NEU3 leading to Src activation

Sialidase NEU3 Contributes to the Invasiveness of Bladder Cancer

Bladder cancer is the 10th most commonly diagnosed cancer worldwide. The current standard treatment for advanced bladder cancer is neoadjuvant cisplatin (NAC)-based chemotherapy followed by cystectomy. However, the response rate to chemotherapy is only 50%, owing to cisplatin resistance, and there is a need for novel therapies. Because the invasiveness of bladder cancer greatly influences patient prognosis, a mechanistic analysis of the invasive function can lead to therapeutic targets. Sialidases, which remove sialic acid residues from the nonreducing ends of sugar chains and catalyze the initial reaction in the degradation of sugar chains, are predicted to be involved in cell invasion and motility. However, the involvement of sialidases in bladder cancer, especially their relationship with the invasive ability, remains unclear. Here, using patient tissues and multiple bladder cancer cell lines, we show that the sialidase NEU3 is highly expressed in bladder cancer. Analysis of NEU3's function using its siRNA-mediated knockdown revealed that NEU3 contributes to bladder cancer invasiveness. Mechanistic analysis showed that NEU3 activates ERK and PI3K signaling. Our results show that NEU3 is involved in the malignancy of bladder cancer, and its suppression may lead to novel treatments for bladder cancer.

Different Transcriptome Features of Peripheral Blood Mononuclear Cells in Non-Emphysematous Chronic Obstructive Pulmonary Disease

Non-emphysematous chronic obstructive pulmonary disease (COPD), which is defined based on chest computed tomography findings, presented different transcriptome features of peripheral blood mononuclear cells (PBMCs) compared with emphysematous COPD. Enrichment analysis of transcriptomic data in COPD demonstrated that the "Hematopoietic cell lineage" pathway in Kyoto Encyclopedia of Genes and Genomes pathway analysis was highly upregulated, suggesting that cellular dynamic dysregulation in COPD lungs is affected by pathologically modified PBMCs. The differentially expressed genes (DEGs) upregulated in PBMCs reflected the disease state of non-emphysematous COPD. Upregulated DEGs such as XCL1, PRKCZ, TMEM102, CD200R1, and AQP1 activate T lymphocytes and eosinophils. Upregulating keratan sulfate biosynthesis and metabolic processes is associated with protection against the destruction of the distal airways. ITGA3 upregulation augments interactions with extracellular matrix proteins, and COL6A1 augments the profibrotic mast cell phenotype during alveolar collagen VI deposition. Upregulating HSPG2, PDGFRB, and PAK4 contributes to the thickening of the airway wall, and upregulating SERPINF1 expression explains the better-preserved vascular bed. Therefore, gene expression and pathway analysis in PBMCs in patients with non-emphysematous COPD represented type 2 immune responses and airway remodeling features. Therefore, these patients have asthmatic potential despite no clinical signs of asthma, in contrast to those with emphysematous COPD.

alpha2,3 sialic acid processing enzymes expression in gastric cancer tissues reveals that ST3Gal3 but not Neu3 are associated with Lauren's classification, angiolymphatic invasion and histological grade

Gastric cancer (GC) is one of the leading causes of cancer-related deaths worldwide. Despite progress in the last decades, there are still no reliable biomarkers for the diagnosis of and prognosis for GC. Aberrant sialylation is a widespread critical event in the development of GC. Neuraminidases (Neu) and sialyltransferases (STs) regulate the ablation and addition of sialic acid during glycoconjugates biosynthesis, and they are a considerable source of biomarkers in various cancers. This study retrospectively characterized Neu3 and ST3Gal3 expression by immunohistochemistry in 71 paraffin-embedded GC tissue specimens and analyzed the relationship between their expression and the clinicopathological parameters. Neu3 expression was markedly increased in GC tissues compared with non-tumoral tissues (p<0.0001). Intratumoral ST3Gal3 staining was significantly associated with intestinal subtype (p=0.0042) and was negatively associated with angiolymphatic invasion (p=0.0002) and higher histological grade G3 (p=0.0066). Multivariate analysis revealed that ST3Gal3 positivity is able to predict Lauren's classification. No associations were found between Neu3 staining and clinical parameters. The in silico analysis of mRNA expression in GC validation cohorts corroborates the significant ST3Gal3 association with higher histological grade observed in our study. These findings suggest that ST3Gal3 expression may be an indicator for aggressiveness of primary GC.

Review sialidase NEU3 and its pathological significance

Sialidases (EC 3.2.1.18, also called neuraminidases) catalyze the removal of α-glycosidically linked sialic acid residues from glycoproteins and glycolipids; this is the initial step in the degradation of these glycoconjugates. Sialidases of mammalian origin have been implicated in not only lysosomal catabolism but also the modulation of functional molecules involved in many biological processes. To date, four types of mammalian sialidases have been cloned and designated as Neu1, Neu2, Neu3 and Neu4. These sialidases differ in their subcellular localization and enzymatic properties, as well as their chromosomal localization, and they are expressed in a tissue-specific manner. Among the sialidases, the plasma membrane-associated sialidase Neu3 appears to play particular roles in controlling transmembrane signaling through the modulation of gangliosides, and its aberrant expression is closely related to various pathogeneses, including that of cancer. Interestingly, the human orthologue NEU3 acts in two ways, catalytic hydrolysis of gangliosides and protein interactions with other signaling molecules. Aberrant NEU3 expression can induce various pathological conditions. This review briefly summarizes recent studies, focusing on the involvement of NEU3 in various pathological phenomena.

Serum Sialylation Changes in Actinic Keratosis and Cutaneous Squamous Cell Carcinoma Patients

Cutaneous squamous cell carcinoma (cSCC), a malignant proliferation of the cutaneous epithelium, is the second most common skin cancer after basal cell carcinoma (BCC). Unlike BCC, cSCC exhibits a greater aggressiveness and the ability to metastasize to any organ in the body. Chronic inflammation and immunosuppression are important processes linked to the development of cSCC. The tumor can occur de novo or from the histological transformation of preexisting actinic keratoses (AK). Malignant cells exhibit a higher amount of sialic acid in their membranes than normal cells, and changes in the amount, type, or linkage of sialic acid in malignant cell glycoconjugates are related to tumor progression and metastasis. The aim of our study was to investigate the sialyation in patients with cSCC and patients with AK. We have determined the serum levels of total sialic acid (TSA), lipid-bound sialic acid (LSA), beta-galactoside 2,6-sialyltransferase I (ST6GalI), and neuraminidase 3 (NEU3) in 40 patients with cSCC, 28 patients with AK, and 40 healthy subjects. Data analysis indicated a significant increase in serum levels of TSA (p < 0.001), LSA (p < 0.001), ST6GalI (p < 0.001), and NEU3 (p < 0.001) in the cSCC group compared to the control group, whereas in patients with AK only the serum level of TSA was significantly higher compared to the control group (p < 0.001). When the cSCC and AK groups were compared, significant differences between the serum levels of TSA (p < 0.001), LSA (p < 0.001), ST6GalI (p < 0.001) and NEU3 (p < 0.001) were found. The rate of synthesis of sialoglycoconjugates and their rate of enzymatic degradation, expressed by the ST6GalI/NEU3 ratio, is 1.64 times lower in the cSCC group compared to the control group (p < 0.01) and 1.53 times lower compared to the AK group (p < 0.01). The tumor diameter, depth of invasion, and Ki67 were associated with higher levels of TSA and LSA. These results indicate an aberrant sialylation in cSCC that correlates with tumor aggressiveness.

The Novel Target of Liver Cancer: MicroRNA-4324 Regulates Cell Proliferation and Migration via Targeting Neuraminidase 3

Background: MicroRNA-4324 has been reported to regulate various biological malignant cancer. Nonetheless, the expression and molecular mechanism of miR-4324 in liver cancer remain rarely known. This study aimed to investigate the effect miR-4324 on the proliferation, invasion and migration of hepatoma cells. Methods: The mRNA level of miR-4324 was assessed in four hepatoma cell lines (HepG2, Huh7, MHCC97, HB611) and human embryonic liver cell, HHL5. MiR-4324 was over-expressed in hepatoma cells. Subsequently, the effects of miR-4324 on cell proliferation, migration and invasion and the underlying molecular mechanisms were detected. Results: Our data indicated that miR-4324 was down-regulation in hepatoma cell lines compared with HHL5. Overexpression of miR-4324 inhibits cellular proliferation, colony-formation, migration and invasion abilities of hepatoma cells. However, the biological effects of miR-4324 overexpression on hepatoma cells were reversed after overexpressing NEU3. Conclusions: Our findings concluded that miR-4324 inhibits biological functions of hepatoma cells by targeting NEU3 and it might be a potential target for the treatment of liver cancer.

Targeting K-Ras and apoptosis-driven cellular transformation in cancer

Cellular transformation is a major event that helps cells to evade apoptosis, genomic instability checkpoints, and immune surveillance to initiate tumorigenesis and to promote progression by cancer stem cell expansion. However, the key molecular players that govern cellular transformation and ways to target cellular transformation for therapy are poorly understood to date. Here we draw key evidences from the literature on K-Ras-driven cellular transformation in the context of apoptosis to shed light on the key players that are required for cellular transformation and explain how aiming p53 could be useful to target cellular transformation. The defects in key apoptosis regulators such as p53, Bax, and Bak lead to apoptosis evasion, cellular transformation, and genomic instability to further lead to stemness, tumorigenesis, and metastasis via c-Myc-dependent transcription. Therefore enabling key apoptotic checkpoints in combination with K-Ras inhibitors will be a promising therapeutic target in cancer therapy.

Gangliosides and Neuroblastomas

The focus of this review is the ganglio-series of glycosphingolipids found in neuroblastoma (NB) and the myriad of unanswered questions associated with their possible role(s) in this cancer. NB is one of the more common solid malignancies of children. Five-year survival for those diagnosed with low risk NB is 90-95%, while that for children with high-risk NB is around 40-50%. Much of the survival rate reflects age of diagnosis with children under a year having a much better prognosis than those over two. Identification of expression of GD2 on the surface of most NB cells led to studies of the effectiveness and subsequent approval of anti-GD2 antibodies as a treatment modality. Despite much success, a subset of patients, possibly those whose tumors fail to express concentrations of gangliosides such as GD1b and GT1b found in tumors from patients with a good prognosis, have tumors refractory to treatment. These observations support discussion of what is known about control of ganglioside synthesis, and their actual functions in NB, as well as their possible relationship to treatment response.

Regulation of Src Family Kinases during Colorectal Cancer Development and Its Clinical Implications

Src family kinases (SFKs) are non-receptor kinases that play a critical role in the pathogenesis of colorectal cancer (CRC). The expression and activity of SFKs are upregulated in patients with CRC. Activation of SFKs promotes CRC cell proliferation, metastases to other organs and chemoresistance, as well as the formation of cancer stem cells (CSCs). The enhanced expression level of Src is associated with decreased survival in patients with CRC. Src-mediated regulation of CRC progression involves various membrane receptors, modulators, and suppressors, which regulate Src activation and its downstream targets through various mechanisms. This review provides an overview of the current understanding of the correlations between Src and CRC progression, with a special focus on cancer cell proliferation, invasion, metastasis and chemoresistance, and formation of CSCs. Additionally, this review discusses preclinical and clinical strategies to improve the therapeutic efficacy of drugs targeting Src for treating patients with CRC.

Human Sialidase Neu3 is S-Acylated and Behaves Like an Integral Membrane Protein

Membrane-bound sialidase Neu3 is involved in the catabolism of glycoconjugates, and plays crucial roles in numerous biological processes. Since the mechanism of its association with membranes is still not completely understood, the aim of this work was to provide further information regarding this aspect. Human Neu3 was found to be associated with the plasma membrane and endomembranes, and it was not released from the lipid bilayer under conditions that typically release peripheral membrane proteins. By different experimental approaches, we demonstrated that its C-terminus is exposed to the cytosol while another portion of the protein is exposed to the extracellular space, suggesting that Neu3 possesses the features of a transmembrane protein. However, in silico analysis and homology modeling predicted that the sialidase does not contain any α-helical transmembrane segment and shares the same β-propeller fold typical of viral and bacterial sialidases. Additionally, we found that Neu3 is S-acylated. Since this post-translational modification is restricted to the cytosolic side of membranes, this finding strongly supports the idea that Neu3 may contain a cytosolic-exposed domain. Although it remains to be determined exactly how this sialidase crosses the lipid bilayer, this study provides new insights about membrane association and topology of Neu3.

Integrin-mediated cell migration is blocked by inhibitors of human neuraminidase

Integrins are critical receptors in cell migration and adhesion. A number of mechanisms are known to regulate the function of integrins, including phosphorylation, conformational change, and cytoskeletal anchoring. We investigated whether native neuraminidase (Neu, or sialidase) enzymes which modify glycolipids could play a role in regulating integrin-mediated cell migration. Using a scratch assay, we found that exogenously added Neu3 and Neu4 activity altered rates of cell migration. We observed that Neu4 increased the rate of migration in two cell lines (HeLa, A549); while Neu3 only increased migration in HeLa cells. A bacterial neuraminidase was able to increase the rate of migration in HeLa, but not in A549 cells. Treatment of cells with complex gangliosides (GM1, GD1a, GD1b, and GT1b) resulted in decreased cell migration rates, while LacCer was able to increase rates of migration in both lines. Importantly, our results show that treatment of cells with inhibitors of native Neu enzymes had a dramatic effect on the rates of cell migration. The most potent compound tested targeted the human Neu4 isoenzyme, and was able to substantially reduce the rate of cell migration. We found that the lateral mobility of integrins was reduced by treatment of cells with Neu3, suggesting that Neu3 enzyme activity resulted in changes to integrin-co-receptor or integrin-cytoskeleton interactions. Finally, our results support the hypothesis that inhibitors of human Neu can be used to investigate mechanisms of cell migration and for the development of anti-adhesive therapies.

NEU3 Sialidase Protein Interactors in the Plasma Membrane and in the Endosomes

NEU3 sialidase has been shown to be a key player in many physio- and pathological processes, including cell differentiation, cellular response to hypoxic stress, and carcinogenesis. The enzyme, peculiarly localized on the outer leaflet of the plasma membrane, has been shown to be able to remove sialic acid residues from the gangliosides present on adjacent cells, thus creating cell to cell interactions. Nonetheless, herein we report that the enzyme localization is dynamically regulated between the plasma membrane and the endosomes, where a substantial amount of NEU3 is stored with low enzymatic activity. However, under opportune stimuli, NEU3 is shifted from the endosomes to the plasma membrane, where it greatly increases the sialidase activity. Finally, we found that NEU3 possesses also the ability to interact with specific proteins, many of which are different in each cell compartment. They were identified by mass spectrometry, and some selected ones were also confirmed by cross-immunoprecipitation with the enzyme, supporting NEU3 involvement in the cell stress response, protein folding, and intracellular trafficking.

Upregulation of sialidase NEU3 in head and neck squamous cell carcinoma associated with lymph node metastasis

Regional lymph node metastasis in head and neck squamous cell carcinoma (HNSCC) is a crucial event for its progression, associated with a high rate of mortality. Sialidase, a key enzyme for the regulation of cellular sialic acids through catalyzing the initial step of degradation of glycoproteins and glycolipids, has been implicated in cancer progression. To facilitate the development of novel treatments for HNSCC, we have investigated whether sialidase is involved in the progression of this cancer. We found plasma membrane‐associated sialidase (NEU3) to be significantly upregulated in tumor compared to non‐tumor tissues; particularly, an increase in its mRNA levels was significantly associated with lymph node metastasis. To understand the mechanisms, we analyzed the NEU3‐mediated effects on the malignant phenotype using squamous carcinoma HSC‐2 and SAS cells. NEU3 promoted cell motility and invasion, accompanied by the increased expression of MMP‐9, whereas NEU3 silencing or the activity‐null mutant did not. NEU3 enhanced phosphorylation of epidermal growth factor receptor (EGFR), and an EGFR inhibitor, AG1478, abrogated the NEU3‐induced MMP9 augmentation. These findings identify NEU3 as a participant in HNSCC progression through the regulation of EGFR signaling and thus as a potential target for inhibiting EGFR‐mediated tumor progression.