Elevated levels of glycosylphosphatidylinositol (GPI) anchored proteins in plasma from human cancers detected by C. septicum alpha toxin

Abstract

The glycosylphosphatidylinositol (GPI) anchor is a glycan and lipid posttranslational modification added to proteins in the endoplasmic reticulum. Certain enzymes within the GPI biosynthetic pathway, particularly the subunits of the GPI transamidase, are elevated in various human cancers. Specific GPI anchored proteins, such as carcinoembryonic antigen and mesothelin, have been described as potential biomarkers for certain cancers; however, the overall levels of GPI anchored proteins present in plasma from cases of human cancers have not been evaluated. We have developed the use of a bacterial toxin known as alpha toxin from Clostridium septicum to detect GPI anchored proteins in vitro. In this study, we use alpha toxin to detect GPI anchored proteins present in plasma from cases of several types of human cancers. Our data indicate that human cancers with previously documented elevations of GPI transamidase subunits show increased alpha toxin binding to plasma from patients with these cancers, indicating increased levels of GPI anchored proteins. Furthermore, our results reveal very low levels of alpha toxin binding to plasma from patients with no malignant disease indicating few GPI anchored proteins are present. These data suggest that GPI anchored proteins present in plasma from these cancers represent biomarkers with potential use for cancer detection.

Comprehensive analysis of lncRNA expression profiles reveals a novel lncRNA signature to discriminate nonequivalent outcomes in patients with ovarian cancer

“…MAPK pathways can control fundamental cellular processes by linking extracellular signals to the machinery, and distinct groups of MAPK pathways have been widely studied, revealing important roles of MAPK pathways in cancers, including OvCa [72, 73]. Glycosylphosphatidylinositol (GPI) anchor is an unique type of glycoconjugate, and abnormal expression levels of certain components in the GPI-anchor biosynthetic pathway have been reported to be associated with various cancers [74]. A recent experimental study provided evidence for the role of calcium-related genes in mediating cisplatin resistance in ovarian cancer cells [75].…”

Protein Glycosylation in Cancer

“…The GPI anchor is a glycan and lipid posttranslational modification added to proteins in the ER (Figure 1). GPI-anchored glycoproteins were recently found to be elevated in the plasma of patients with many types of cancers, including breast, ovarian, kidney, liver, lung, colon, and brain (128, 129). Its potential diagnostic and screening value is under evaluation.…”

Unprocessed serum glycosylphosphatidylinositol-anchored proteins are correlated to metabolic states

“…However, the presence and abundance of adipocyte-derived GLEC in serum remain to be investigated. Albeit the expression of GLEC in vivo has not been reported so far, alterations in the specific as well as total expression pattern of GPI-AP and phospholipids in plasma, as measured by ELISA (for CD59), proteomics and lipidomics, have been described for aging 18 , breast cancer 19 and Alzheimer's disease 20 , respectively. However, changes in the GPI-AP-to-cholesterol-to-phospholipid ratio of (serum and plasma membrane-derived) GLEC with the corresponding insults on spec.…”

“…Epididymal fat pads from male Wistar rats (weight see below, fed ad libitum) were washed several times in Krebs-Ringer-Henseleit buffer (KRH; 25 mM HEPES free acid, 25 mM HEPES sodium salt, 1.2 mM KH 2 PO 4 , 140 mM NaCl, 4.7 mM KCl, 1.2 mM MgSO 4 , 2.5 mM CaCl 2 ) supplemented with 0.75% (w/v) BSA and adjusted to pH 7.=KRHLB) and then cut into two to three pieces. Two pieces each were incubated with 1.5 ml of digestion buffer (10 mg collagenase and 9 mg glucose in 10 ml of KRH containing 5% BSA [=KRHHB], 1 mM sodium pyruvate, 5.5 mM glucose, 0.5 U/ml ADA, 200 nM PIA, 100 µg/ml gentamycin, 50 units/ml penicillin and 50 µg/ml streptomycin sulfate) for[15][16][17][18][19][20] min at 37°C in a shaking water bath (240 cycles/min) at constant bubbling with 95% O 2 /5% CO 2 . Released adipocytes were passed through a nylon web (mesh size 750 μM) with no pressure other than gentle teasing with a plastic spatula for passing of the cells through and then centrifuged (500xg, 1 min, swing-out rotor).…”