Rades D, Bartscht T, Hunold P, Schmidberger H, König L, et al.
Strahlentherapie und Onkologie : Organ der Deutschen Rontgengesellschaft ... [et al] •
To investigate the efficacy and toxicity of cetuximab when added to radiochemotherapy for unresectable esophageal cancer. This randomized phase 2 trial (clinicaltrials.gov, identifier NCT01787006) compared radiochemotherapy plus cetuximab (arm A) to radiochemotherapy (arm B) for unresectable esophageal cancer. Primary objective was 2‑year overall survival (OS). Arm A was considered insufficiently active if 2‑year OS was ≤40% (null hypothesis = H), and promising if the lower limit of the 95% confidence interval was >45%. If that lower limit was >40%, H was rejected. Secondary objectives included progression-free survival (PFS), locoregional control (LC), metastases-free survival (MFS), response, and toxicity. The study was terminated early after 74 patients; 68 patients were evaluable. Two-year OS was 71% in arm A (95% CI: 55-87%) vs. 53% in arm B (95% CI: 36-71%); H was rejected. Median OS was 49.1 vs. 24.1 months (p = 0.147). Hazard ratio (HR) for death was 0.60 (95% CI: 0.30-1.21). At 2 years, PFS was 56% vs. 44%, LC 84% vs. 72%, and MFS 74% vs. 54%. HRs were 0.51 (0.25-1.04) for progression, 0.43 (0.13-1.40) for locoregional failure, and 0.43 (0.17-1.05) for distant metastasis. Overall response was 81% vs. 69% (p = 0.262). Twenty-six and 27 patients, respectively, experienced at least one toxicity grade ≥3 (p = 0.573). A significant difference was found for grade ≥3 allergic reactions (12.5% vs. 0%, p = 0.044). Given the limitations of this trial, radiochemotherapy plus cetuximab was feasible. There was a trend towards improved PFS and MFS. Larger studies are required to better define the role of cetuximab for unresectable esophageal cancer.
Claes D, Memmel E, Holzapfel M, Seibel J, Maison W
Chembiochem : a European journal of chemical biology •
Carbohydrates are involved in a wide range of biological processes of pharmaceutical relevance. The selective recognition of carbohydrates is therefore of great interest in biology and medicine. In this study we present the synthesis of fluorescent multimeric benzoboroxoles and the analysis of multivalent binding processes to immobilized carbohydrate arrays by fluorescence spectroscopy. We observed high binding affinities of trimeric benzoboroxoles by determination of KDsurf values for their interaction with α-Gal on glass chips. The observed KDsurf values were in the mid-nM range (49 and 104 nM) and are comparable to the KDsurf values for binding of natural lectins, such as that of ConA to immobilized α-Man (79 nM). The array technology was found to be an excellent tool for studying the binding processes of multivalent lectin mimetics with respect to profiling and quantitation.
Thomsen-Friedenreich antigen (Galbeta1-3GalNAc), generally known as T-antigen, is expressed in more than 85% of human carcinomas. Therefore, proteins which specifically bind T-antigen have potential diagnostic value. Jacalin, a lectin from jack fruit (Artocarpus integrifolia) seeds, is a tetramer of molecular mass 66kDa. It is one of the very few proteins which are known to bind T-antigen. The crystal structure of the jacalin-T-antigen complex has been determined at 1.62A resolution. The interactions of the disaccharide at the binding site are predominantly through the GalNAc moiety, with Gal interacting only through water molecules. They include a hydrogen bond between the anomeric oxygen of GalNAc and the pi electrons of an aromatic side-chain. Several intermolecular interactions involving the bound carbohydrate contribute to the stability of the crystal structure. The present structure, along with that of the Me-alpha-Gal complex, provides a reasonable qualitative explanation for the known affinities of jacalin to different carbohydrate ligands and a plausible model of the binding of the lectin to T-antigen O-linked to seryl or threonyl residues. Including the present one, the structures of five lectin-T-antigen complexes are available. GalNAc occupies the primary binding site in three of them, while Gal occupies the site in two. The choice appears to be related to the ability of the lectin to bind sialylated sugars. In either case, most of the lectin-disaccharide interactions are at the primary binding site. The conformation of T-antigen in the five complexes is nearly the same.
Cobra venom factor (CVF) is the nontoxic C-activating glycoprotein in cobra venom. It is a structural and functional analogue of complement component C3. Previous work has established that the major oligosaccharide chain of CVF is a symmetric fucosylated biantennary complex-type N-linked chain containing an alpha-galactosylated Le(x) antigenic epitope, Gal alpha 1-3Gal beta 1-4 (Fuc alpha 1-3) GlcNAc beta 1, a novel carbohydrate structure. We show that naturally occurring anti-alpha-Gal Ab present in normal human serum binds to CVF. In view of a possible human application of CVF, we studied the effect of this anti-alpha-Gal Ab on CVF function as well as the effect of oligosaccharide modification or removal on CVF activity and immunoreactivity with the anti-alpha-Gal Ab. The immunoreactivity of CVF with the anti-alpha-Gal Ab is abolished upon de-alpha-galactosylation or complete deglycosylation. De-alpha-galactosylated CVF and deglycosylated CVF were found to be equally active in forming a stable C3/C5 convertase with human factor B and in decomplementing human serum indicating that the oligosaccharide chains of CVF are not required for its C-activating function. Consistent with the unaltered functional activity, deglycosylation of the molecule caused only minor changes in secondary structure as judged by far UV circular dichroism analysis. However, the oligosaccharide chains appear to contribute to the thermal stability of CVF, because deglycosylation caused the molecule to be more sensitive to temperature. Inasmuch as rCVF produced in mammalian cells can be expected to contain sialylated oligosaccharide chains, we also prepared sialylated CVF by enzymatic sialylation of de-alpha-galactosylated and de-alpha-fucosylated CVF with 2,6-sialyltransferase. It was found that the secondary structure and the activity of sialylated CVF were unchanged compared to native CVF.
