The consideration of oligosaccharides and glycoconjugates as biopharmaceuticals is an emerging topic in drug design. Chemoenzymatic synthesis of N-glycans was performed to examine the influence of N-glycan core fucosylation on lectin-binding properties and biodistribution. As a first step in a systematic comparison of N-glycans, the core fucose moiety was chemically introduced into a complex-type biantennary heptasaccharide azide. After deprotection and attachment of a spacer, the terminal sections of the N-glycan were elongated enzymatically. Conversion of the amino group in the spacer to an isothiocyanate gave derivatives allowing convenient ligand attachment to bovine serum albumin (BSA). The resulting neoglycoproteins contained an average of 2.9-4.6 chains per carrier molecule. Relative to unsubstituted biantennary complex-type N-glycans, the core fucosylation appears to favor the extended orientation of the alpha 1,6-arm. This was deduced from an up to 5-fold alteration of affinity for lectins in solid-phase assays. Marked differences were also found for cell surface binding of cultured tumor cells, for staining of tumor cells in lung sections, and in organ distribution. In vivo, the alpha 2,6-sialylated neoglycoproteins showed a reduced serum half-life in mice relative to the alpha 2,3-sialylated isomer and the non-fucosylated congeners. These results support the notion that changing the shape of a glycan provides a promising strategy to optimize the affinity of protein-carbohydrate interactions. Overall, our study underscores the importance of chemoenzymatic synthesis to define the effect of chain orientation on the ligand properties of N-glycans.

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Cryotherapy is used as a treatment for nonresectable liver tumors and adenocarcinoma of the prostate. Morbidity and mortality following cryotherapy are generally considered to be infrequent, but a syndrome of multiorgan failure, severe coagulopathy, and disseminated intravascular coagulation following hepatic cryotherapy has been described and referred to as the cryoshock phenomenon. In this study we aimed to assess and describe the incidence and clinical features of the cryoshock phenomenon following cryosurgery from the surveyed experience of a large number of clinical centers and to relate the data to the overall mortality and morbidity of this treatment. A questionnaire was sent to all cryotherapy users (n = 299) of whom we were aware. We requested information on the number of patients treated, the occurrence, and the clinical features of cryoshock and mortality and morbidity following cryotherapy of the prostate or liver. Altogether 134 completed questionnaires were returned (44.8%). Seventy-two centers had experience with hepatic cryotherapy and 62 with prostate cryotherapy. Following hepatic cryotherapy, the phenomenon of cryoshock was observed in 21 of 2173 patients (1%) and was responsible for 6 of 33 perioperative deaths (18.2%). Cryoshock was rare following prostate cryotherapy (2 of 5432 patients, 0.04%) and did not contribute to the overall mortality of 0.06%. Hepatic and prostate cryotherapy are safe. Cryoshock is rare after prostate cryotherapy but occurs in 1% of patients following hepatic cryotherapy. Cryoshock is associated with a high risk of death, being responsible for 18.2% of deaths in this survey. Research regarding the mechanism and possible avoidance of cryoshock is required.

We have investigated the consequences of introducing a bisecting GlcNAc moiety into biantennary N‐glycans. Computational analysis of glycan conformation with prolonged simulation periods in vacuo and in a solvent box revealed two main effects: backfolding of the α1–6 arm and stacking of the bisecting GlcNAc and the neighboring Man/GlcNAc residues of both antennae. Chemoenzymatic synthesis produced the bisecting biantennary decasaccharide N‐glycan and its α2–3(6)‐sialylated variants. They were conjugated to BSA to probe the ligand properties of N‐glycans with bisecting GlcNAc. To assess affinity alterations in glycan binding to receptors, testing was performed with purified lectins, cultured cells, tissue sections and animals. The panel of lectins, including an adhesion/growth‐regulatory galectin, revealed up to a sixfold difference in affinity constants for these neoglycoproteins relative to data on the unsubstituted glycans reported previously [André, S., Unverzagt, C., Kojima, S., Dong, X., Fink, C., Kayser, K. & Gabius, H.‐J. (1997) Bioconjugate Chem. 8, 845–855]. The enhanced affinity for galectin‐1 is in accord with the increased percentage of cell positivity in cytofluorimetric and histochemical analysis of carbohydrate‐dependent binding of labeled neoglycoproteins to cultured tumor cells and routinely processed lung cancer sections. Intravenous injection of iodinated neoglycoproteins carrying galactose‐terminated N‐glycans into mice revealed the highest uptake in liver and spleen for the bisecting compound compared with the unsubstituted or core‐fucosylated N‐glycans. Thus, this substitution modulates ligand properties in interactions with lectins, a key finding of this report. Synthetic glycan tailoring provides a versatile approach to the preparation of newly substituted glycans with favorable ligand properties for medical applications.

Certain chemokines have been proposed to distinctly contribute to tumor growth, dissemination and local immune escape. Expression of the chemokine receptor CXCR4 has been linked to tumor progression in diverse tumor entities. The aim of this study was to evaluate if the expression of CXCR4 influences progression of human pancreatic cancer. CXCR4 expression of pancreatic cancer was retrospectively assessed by immunohistochemistry in 103 patients with pancreatic cancer. Intensity of CXCR4 expression was correlated with both tumor and patient characteristics. Human pancreatic cancer revealed variable intensities of CXCR4 expression. Strong CXCR4 expression was significantly associated with advanced UICC stages (P=0.03) and revealed a trend for hematogenous metastasis (P=0.09) and progressed local tumor stages (P=0.15). In summary, strong expression of CXCR4 was significantly associated with advanced pancreatic cancer.

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Dedicated to Professor Joachim Thiem on the occasion of his 65th birthdayRecombinant therapeutic glycoproteins contain mainly asparagine-linked oligosaccharides (N-glycans), which are often essential for the proper function of the glycoprotein. The heterogeneity of the glycans in natural glycoproteins is a large obstacle for the entire research in the field of glycobiology, [1] and despite recent advances in chemical synthesis of N-glycans, [2][3][4][5][6][7][8][9][10] the majority of N-glycans for biological studies are still isolated from natural sources.[11] We have developed modular building blocks for the most abundant complex N-glycans, [12] which after fortuitous results from the test of this modular system allowed the synthesis of complex N-glycans with the maximum number of branches and core substitutions (glycan F; Scheme 1).Previously we have developed modular building blocks for the synthesis of complex N-glycans with up to four antennae, [12] which contained a bisecting GlcNAc moiety [4,13,14] or a core fucose moiety. [15] As a result of the steric hindrance, bisected N-glycans with three or four antennae are especially difficult to obtain. [4] Encouraged by recent improvements [14] we investigated the complex N-glycan F (Scheme 1). A particularly high substitution pattern is found at the Mana1,6Manb unit of F where each mannose contains a total of four glycosidic partners. Pentaantennary N-glycans are found in ovomucoid, [16] fish hyosophorin, [17] CHO cells, [18] and HepG2 cells. [19] First, unsubstituted pentaantennary N-glycans were assembled to reduce the synthetic complexity of F. The synthesis of tetrasaccharide donor D began with the 3-Oallylation of benzylmannoside (2) via a stannylene acetal to give 3 (Scheme 2). [20,21] Threefold glycosylation of triol 3 with donor 1 (6 equiv) gave the tetrasaccharide 4 (77 %). After deallylation of 4, the acetylation of alcohol 5 required catalytic amounts of DMAP. After catalytic hydrogenation of 6 to remove the benzyl group, the hemiacetal was converted into imidate D and coupled with the hexasaccharide 12 to give the decasaccharide 13 in 65 % yield after optimization (Scheme 3).The high reactivity of donor D prompted us to incorporate a bisecting GlcNAc moiety and a core fucose residue. Thus, the branched trisaccharide B [12] was coupled to the core trisaccharide A (Scheme 4).[15] The resulting hexasaccharide (80 %) was acetylated and the benzylidene acetal was cleaved (75 % over 2 steps). After the selective chloroacetylation of 14, the hexasaccharide 15 was coupled with thioglycoside C [4] to give the bisected heptasaccharide 16. Dechloroacetylation yielded the acceptor 17, which was coupled with the disaccharide 18 (77 %). The nonasaccharide 19 was deprotected and fucosylated to give the triantennary decasaccharide 21 in 93 % yield.Next we investigated the coupling of the heptasaccharide 17 with the donor tetrasaccharide D (5 equiv; Scheme 5). After purification by flash chromatography and HPLC, only 9 % of the bisected pentaantennary compound 22 wa...

The rapid rise of multi-drug-resistant bacteria is a global healthcare crisis, and new antibiotics are urgently required, especially those with modes of action that have low-resistance potential. One promising lead is the liposaccharide antibiotic moenomycin that inhibits bacterial glycosyltransferases, which are essential for peptidoglycan polymerization, while displaying a low rate of resistance. Unfortunately, the lipophilicity of moenomycin leads to unfavourable pharmacokinetic properties that render it unsuitable for systemic administration. In this study, we show that using moenomycin and other glycosyltransferase inhibitors as templates, we were able to synthesize compound libraries based on novel pyranose scaffold chemistry, with moenomycin-like activity, but with improved drug-like properties. The novel compounds exhibit in vitro inhibition comparable to moenomycin, with low toxicity and good efficacy in several in vivo models of infection. This approach based on non-planar carbohydrate scaffolds provides a new opportunity to develop new antibiotics with low propensity for resistance induction.