Glycosaminoglycans and glycolipids as potential biomarkers in lung cancer.

In this report, we used liquid chromatography-mass spectrometry and Western blotting to analyze the content and structure of glycosaminoglycans, glycolipids and selected proteins to compare differences between patient-matched normal and cancerous lung tissues obtained from lung cancer patients. The cancer tissue samples contained over twice as much chondroitin sulfate (CS)/dermatan sulfate (DS) as did the normal tissue samples, while the amount of heparan sulfate (HS) and hyaluronan (HA) in normal and cancer tissues were not significantly different. In HS, several minor disaccharide components, including NS6S, NS2S and 2S were significantly lower in cancer tissues, while the levels of major disaccharides, TriS, NS and 0S disaccharides were not significantly different in normal and cancer tissues. In regards to CS/DS, the level of 4S disaccharide (the major component of CS-type A and DS) decreased and the level of 6S disaccharide (the major component of CS- type C) increased in cancer tissues. We also compared the content and structure of GAGs in lung tissues from smoking and non-smoking patients. Analysis of the glycolipids showed all lipids present in these lung tissues, with the exception of sphingomyelin were higher in cancer tissues than in normal tissues. Western analysis showed that syndecan 1 and 2 proteoglycans displayed much higher expression in cancer tissue/biopsy samples. This investigation begins to provide an understanding of patho-physiological roles on glycosaminoglycans and glycolipids and might be useful in identifying potential biomarkers in lung cancer.

[Construction of eukaryotic plasmid of human GPC3 and expression and purification of recombinant GPC3 protein].

AIM: To obtain enough human glypican-3 (GPC3) protein for structural and functional research. METHODS: The full-length cDNA coding for GPC3 was cloned by RT-PCR from human fetal hepatocytes. The open reading frame (ORF) of the cDNA consists of 1 700 bases, encoding a mature protein of 556 amino acids. The cDNA was inserted into the pPICZ A vector to construct a expression plasmid, named pPICZ A-GPC3. Then the plasmid was transformed into a Pichia pastoris strain, GS115 and the positive strains were screened on the YPD plates with Zeocin. The positive strains were further screened on cellulose acetate and nitrocellulose membrane with HRP labeled His-tag antibody. The selected strains were induced by methanol and the supernatants were analyzed by SDS-PAGE and Western blotting. RESULTS: SDS-PAGE analysis showed an anticipated band on the gel that could bind with goatanti-GPC3 antibody. Furthermore, the strain was fermented and the expression level was about 5 mg/L, and the recombinant GPC3 protein was purified by cation-exchange chromatography from the fermentation supernatant. CONCLUSION: Human GPC3 was expressed successfully in Pichia pastoris and purified to obtain the recombinant protein from fermentation supernatant, which made it possible for further structural and functional studies on GPC3.

Inhibitors of slit protein interactions with the heparan sulphate proteoglycan glypican-1: potential agents for the treatment of spinal cord injury.

1. The heparan sulphate proteoglycan glypican-1 is a major high-affinity ligand of the Slit proteins. 2. Messenger RNA for both Slit-2 and glypican-1 is strongly upregulated and coexpressed in the reactive astrocytes of injured adult brain, suggesting a possible function of Slit proteins and glypican-1 in the adult central nervous system as significant components of the inhibitory environment that prevents axonal regeneration after injury. 3. Based on the hypothesis that adverse effects on axonal regeneration may be due to a glypican-Slit complex or the retention of glypican-binding C-terminal proteolytic processing fragments of Slit at the injury site, we used ELISA to examine a number of small molecules and low molecular weight heparin analogues for their ability to inhibit glypican-Slit interactions. 4. Our studies have led to the identification of several potent inhibitors with a favourable therapeutic profile that can now be tested in a spinal cord injury model. Among the most promising of these are a low molecular weight heparin produced by periodate oxidation and having no significant anticoagulant activity, the chemically sulphonated yeast-derived phosphomannan PI-88 and a number of randomly derivatized water-soluble sulphated dextrans.

S-Nitrosylation of secreted recombinant human glypican-1.

Glypican-1 is a glycosylphosphatidylinositol anchored cell surface S-nitrosylated heparan sulfate proteoglycan that is processed by nitric oxide dependent degradation of its side chains. Cell surface-bound glypican-1 becomes internalized and recycles via endosomes, where the heparan sulphate chains undergo nitric oxide and copper dependent autocleavage at N-unsubstituted glucosamines, back to the Golgi. It is not known if the S-nitrosylation occurs during biosynthesis or recycling of the protein. Here we have generated a recombinant human glypican-1 lacking the glycosylphosphatidylinositol-anchor. We find that this protein is directly secreted into the culture medium both as core protein and proteoglycan form and is not subjected to internalization and further modifications during recycling. By using SDS-PAGE, Western blotting and radiolabeling experiments we show that the glypican-1 can be S-nitrosylated. We have measured the level of S-nitrosylation in the glypican-1 core protein by biotin switch assay and find that the core protein can be S-nitrosylated in the presence of copper II ions and NO donor. Furthermore the glypican-1 proteoglycan produced in the presence of polyamine synthesis inhibitor, alpha-difluoromethylornithine, was endogenously S-nitrosylated and release of nitric oxide induced deaminative autocleavage of the HS side chains of glypican-1. We also show that the N-unsubstituted glucosamine residues are formed during biosynthesis of glypican-1 and that the content increased upon inhibition of polyamine synthesis. It cannot be excluded that endogenous glypican-1 can become further S-nitrosylated during recycling.

Application of retrovirus-mediated expression cloning for receptor screening of a parasite.

Retrovirus-mediated expression cloning has been applied in both virology and cell biology. Although there is some difficulty in applying this technique to screening for a receptor recognized by an intracellular parasite, we modified the conventional method to identify a putative receptor for the Plasmodium falciparum BAEBL protein. We show that this method is effective in screening for a parasite receptor.

Candidate molecular markers for histological diagnosis of early hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors. HCC occurs mainly in chronically diseased livers, e.g. following hepatitis B and C infection. These high-risk patients are closely followed up, and increasing numbers of small equivocal lesions are detected by imaging diagnosis. They are now widely recognized as precursor or early-stage HCCs and are classified as dysplastic nodule or early HCC. These lesions lack typical imaging and histology of ordinary HCC and do not show elevated serum markers of alpha-fetoprotein and PIVKA-II, for example. Molecular analysis of these lesions would help to develop molecular markers for objective histological diagnosis of early HCC and possibly new serum markers for early detection of HCC. It has been reported that HSP70, CAP2, glypican 3 and glutamine synthetase could serve as molecular markers for early HCC. Further analysis is expected to evaluate their usefulness in routine pathological diagnosis including biopsy diagnosis and also as serum markers for early detection of HCC.

Identification of Glypican3 as a novel GLUT4-binding protein.

Insulin stimulates glucose uptake in fat and muscle primarily by stimulating the translocation of vesicles containing facilitative glucose transporters, GLUT4, from intracellular compartments to the plasma membrane. Although cell surface externalization of GLUT4 is critical for glucose transport, the mechanism regulating cell surface GLUT4 remains unknown. Using a yeast two-hybrid screening system, we have screened GLUT4-binding proteins, and identified a novel glycosyl phosphatidyl inositol (GPI)-linked proteoglycan, Glypican3 (GPC3). We confirmed their interaction using immunoprecipitation and a GST pull-down assay. We also revealed that GPC3 and GLUT4 to co-localized at the plasma membrane, using immunofluorescent microscopy. Furthermore, we observed that glucose uptake in GPC3-overexpressing adipocytes was increased by 30% as compared to control cells. These findings suggest that GPC3 may play roles in glucose transport through GLUT4.