Proteomic analysis of Tn-bearing glycoproteins from different stages of melanoma cells reveals new biomarkers

Cutaneous melanoma, the most aggressive form of skin cancer, responds poorly to conventional therapy. The appearance of Tn antigen-modified proteins in cancer is correlated with metastasis and poor prognoses. The Tn determinant has been recognized as a powerful diagnostic and therapeutic target, and as an object for the development of anti-tumor vaccine strategies. This study was designed to identify Tn-carrying proteins and reveal their influence on cutaneous melanoma progression. We used a lectin-based strategy to purify Tn antigen-enriched cellular glycoproteome, the LC-MS/MS method to identify isolated glycoproteins, and the DAVID bioinformatics tool to classify the identified proteins. We identified 146 different Tn-bearing glycoproteins, 88% of which are new. The Tn-glycoproteome was generally enriched in proteins involved in the control of ribosome biogenesis, CDR-mediated mRNA stabilization, cell-cell adhesion and extracellular vesicle formation. The differential expression patterns of Tn-modified proteins for cutaneous primary and metastatic melanoma cells supported nonmetastatic and metastatic cell phenotypes, respectively. To our knowledge, this study is the first large-scale proteomic analysis of Tn-bearing proteins in human melanoma cells. The identified Tn-modified proteins are related to the biological and molecular nature of cutaneous melanoma and may be valuable biomarkers and therapeutic targets.

Lectin microarray technology identifies specific lectins related to lymph node metastasis of advanced gastric cancer

BACKGROUND

Although various molecular profiling technologies have the potential to predict specific tumor phenotypes, the comprehensive profiling of lectin-bound glycans in human cancer tissues has not yet been achieved.

METHODS

We examined 242 advanced gastric cancer (AGC) patients without or with lymph node metastasis-N0 (n = 62) or N+ (n = 180)-by lectin microarray, and identified the specific lectins highly associated with AGC phenotypes.

RESULTS

In seven gastric cancer cell lines, in contrast to expressed-in-cancer lectins, not-expressed-in-cancer (NEC) lectins were tentatively designated by lectin microarray. Binding signals of the specific lectins were robustly reduced in AGC patients with N+ status as compared with those with N0 status. The receiver operating characteristic curve determined the optimal cutoff value to differentiate N0 status from N+ status, and subsequent profiling of NEC lectins identified Vicia villosa agglutinin (VVA) association with the significant other lectins involved in lymph node metastasis. VVA reaction was clearly found on cancer cells, suggesting that it may result from carcinoma-stroma interaction in primary AGC, because VVA is an NEC lectin. Most intriguingly, VVA reaction was remarkably attenuated in the tumor cells of the metastatic lymph nodes, even if it was recognized in primary AGC. In AGC, histological type was strongly associated with soybean agglutinin and Bauhinia purpurea lectin, whereas p53 mutation was the best correlated with Griffonia simplicifolia lectin II.

CONCLUSIONS

Lectin microarrays can be used to very accurately quantify the reaction of glycans with tumor tissues, and such profiles may represent the specific phenotypes, including N+ status, histological type, or p53 mutation of AGC.

The expanding roles of the Sd(a)/Cad carbohydrate antigen and its cognate glycosyltransferase B4GALNT2

BACKGROUND

The histo-blood group antigens are carbohydrate structures present in tissues and body fluids, which contribute to the definition of the individual immunophenotype. One of these, the Sd(a) antigen, is expressed on the surface of erythrocytes and in secretions of the vast majority of the Caucasians and other ethnic groups.

SCOPE OF REVIEW

We describe the multiple and unsuspected aspects of the biology of the Sd(a) antigen and its biosynthetic enzyme β1,4-N-acetylgalactosaminyltransferase 2 (B4GALNT2) in various physiological and pathological settings.

MAJOR CONCLUSIONS

The immunodominant sugar of the Sd(a) antigen is a β1,4-linked N-acetylgalactosamine (GalNAc). Its cognate glycosyltransferase B4GALNT2 displays a restricted pattern of tissue expression, is regulated by unknown mechanisms - including promoter methylation, and encodes at least two different proteins, one of which with an unconventionally long cytoplasmic portion. In different settings, the Sd(a) antigen plays multiple and unsuspected roles. 1) In colon cancer, its dramatic down-regulation plays a potential role in the overexpression of sialyl Lewis antigens, increasing metastasis formation. 2) It is involved in the lytic function of murine cytotoxic T lymphocytes. 3) It prevents the development of muscular dystrophy in various dystrophic murine models, when overexpressed in muscular fibers. 4) It regulates the circulating half-life of the von Willebrand factor (vWf), determining the onset of a bleeding disorder in a murine model.

GENERAL SIGNIFICANCE

The expression of the Sd(a) antigen has a wide impact on the physiology and the pathology of different biological systems.

Spatio-temporal differences in perineuronal net expression in the mouse hippocampus, with reference to parvalbumin

Perineuronal net (PNN) is a specialized aggregate of the extracellular matrix, which is considered to be involved in regulation of structural plasticity of neuronal circuits. Here we examined the spatial and temporal differences in Wisteria floribunda agglutinin-labeled PNN intensity in single cells in the mouse hippocampus, where the neuronal circuits engaged in cognition and emotion are embedded in the dorsal and ventral parts, respectively. In young mice, the intensity of PNN was very low, and there were no significant dorsoventral differences in all hippocampal regions. Developmental increase in PNN intensity was larger in the dorsal part than in the ventral part. As a result, PNN intensity was higher in the dorsal part than in the ventral part in adult mice. Aging dissimilarly affects different regions of the dorsal hippocampus. Namely, PNN intensity in the dorsal part of old mice declined in the CA1 region, remained unchanged in the CA3 region, increased in the dentate gyrus. By contrast, there were no significant aging-related changes in PNN intensity in the ventral hippocampus. We also examined the intensity of parvalbumin (PV), an EF-hand calcium-binding protein, because it has been shown that PNNs are closely related to PV-containing GABAergic inhibitory neurons. Contrary to expectations, developmental and aging-related changes in PV intensity were not comparable to those seen in PNN intensity. The correlation coefficients between PNN and PV intensities in single cells showed gradual decline during development and aging in the CA1 and CA3 regions, while there were little correlations in the dentate gyrus regardless of age. In summary, PNNs are differentially expressed in the dorsal and ventral hippocampal circuits during development and aging, indicating their possible role for cognition and emotion control.