ST3Gal.I sialyltransferase relevance in bladder cancer tissues and cell lines

<p>Abstract</p> <p>Background</p> <p>The T antigen is a tumor-associated structure whose sialylated form (the sialyl-T antigen) involves the altered expression of sialyltransferases and has been related with worse prognosis. Since little or no information is available on this subject, we investigated the regulation of the sialyltransferases, able to sialylate the T antigen, in bladder cancer progression.</p> <p>Methods</p> <p>Matched samples of urothelium and tumor tissue, and four bladder cancer cell lines were screened for: <it>ST3Gal.I</it>, <it>ST3Gal.II </it>and <it>ST3Gal.IV </it>mRNA level by real-time PCR. Sialyl-T antigen was detected by dot blot and flow cytometry using peanut lectin. Sialyltransferase activity was measured against the T antigen in the cell lines.</p> <p>Results</p> <p>In nonmuscle-invasive bladder cancers, <it>ST3Gal.I </it>mRNA levels were significantly higher than corresponding urothelium (p < 0.001) and this increase was twice more pronounced in cancers with tendency for recurrence. In muscle-invasive cancers and matching urothelium, <it>ST3Gal.I </it>mRNA levels were as elevated as nonmuscle-invasive cancers. Both non-malignant bladder tumors and corresponding urothelium showed <it>ST3Gal.I </it>mRNA levels lower than all the other specimen groups. A good correlation was observed in bladder cancer cell lines between the <it>ST3Gal.I </it>mRNA level, the ST activity (r = 0.99; p = 0.001) and sialyl-T antigen expression, demonstrating that sialylation of T antigen is attributable to ST3Gal.I. The expression of sialyl-T antigens was found in patients' bladder tumors and urothelium, although without a marked relationship with mRNA level. The two <it>ST3Gal.I </it>transcript variants were also equally expressed, independently of cell phenotype or malignancy.</p> <p>Conclusion</p> <p>ST3Gal.I plays the major role in the sialylation of the T antigen in bladder cancer. The overexpression of <it>ST3Gal.I </it>seems to be part of the initial oncogenic transformation of bladder and can be considered when predicting cancer progression and recurrence.</p

Multivalent glycoconjugates as vaccines and potential drug candidates

Pathogens adhere to the host cells during the first steps of infection through multivalent interactions which involve protein–glycan recognition. Multivalent interactions are also involved at different stages of immune response. Insights into these multivalent interactions generate a way to use suitable carbohydrate ligands that are attached to a basic scaffold consisting of e.g., dendrimer, polymer, nanoparticle, etc., with a suitable linker. Thus a multivalent architecture can be obtained with controllable spatial and topology parameters which can interfere with pathogen adhesion. Multivalent glycoconjugates bearing natural or unnatural carbohydrate antigen epitopes have also been used as carbohydrate based vaccines to stimulate an innate and adaptive immune response. Designing and synthesizing an efficient multivalent architecture with optimal ligand density and a suitable linker is a challenging task. This review presents a concise report on the endeavors to potentially use multi- and polyvalent glycoconjugates as vaccines as well as anti-infectious and anti-inflammatory drug candidates

Hepatic Heme-Regulated Inhibitor (HRI) Eukaryotic Initiation Factor 2α Kinase: A Protagonist of Heme-Mediated Translational Control of CYP2B Enzymes and a Modulator of Basal Endoplasmic Reticulum Stress Tone

We have reported previously that the hepatic heme-regulated inhibitor (HRI)-eukaryotic initiation factor 2α (eIF2α) kinase is activated in acute heme-deficient states, resulting in translational shut-off of global hepatic protein synthesis, including phenobarbital (PB)-mediated induction of CYP2B enzymes in rats. These findings revealed that heme regulates hepatic CYP2B synthesis at the translational level via HRI. As a proof of concept, we have now employed a genetic HRI-knockout (KO) mouse hepatocyte model. In HRI-KO hepatocytes, PB-mediated CYP2B protein induction is no longer regulated by hepatic heme availability and proceeds undeterred even after acute hepatic heme depletion. It is noteworthy that genetic ablation of HRI led to a small albeit significant elevation of basal hepatic endoplasmic reticulum (ER) stress as revealed by the activation of ER stress-inducible RNA-dependent protein kinase-like ER-integral (PERK) eIF2α-kinase, and induction of hepatic protein ubiquitination and ER chaperones Grp78 and Grp94. Such ER stress was further augmented after PB-mediated hepatic protein induction. These findings suggest that HRI normally modulates the basal hepatic ER stress tone. Furthermore, because HRI exists in both human and rat liver in its heme-sensitive form and is inducible by cytochrome P450 inducers such as PB, these findings are clinically relevant to acute heme-deficient states, such as the acute hepatic porphyrias. Activation of this exquisitely sensitive heme sensor would normally protect cells by safeguarding cellular energy and nutrients during acute heme deficiency. However, similar HRI activation in genetically predisposed persons could lead to global translational arrest of physiologically relevant enzymes and proteins, resulting in the severe and often fatal clinical symptoms of the acute hepatic porphyrias