Glucosamine Analogs Research Articles

Warburg Effect Targeting Co(III) Cytotoxin Chaperone Complexes

A glucose-based vector for targeting cancer cells conjugated to a tris(methylpyridyl)amine (tpa) ligand to generate targeted chaperone and caging complexes for active anticancer agents is described. The ligand, tpa(CONHPEGglucose)1, inhibits hexokinase, suggesting that it will be phosphorylated in the cell. A Co(III) complex incorporating this ligand and coumarin-343 hydroximate (C343ha), [Co(C343ha){tpa(CONHPEGglucose)1}]Cl, is shown to exhibit glucose-dependent cellular accumulation in DLD-1 colon cancer cells. Cellular accumulation of [Co(C343ha){tpa(CONHPEGglucose)1}]+ is slower than for the glucose null and glucosamine analogues, and the glucose complex also exhibits a lower ability to inhibit antiproliferative activity. Distributions of cobalt (X-ray fluorescence) and C343ha (visible light fluorescence) in DLD-1 cancer cell spheroids are consistent with uptake of [Co(C343ha){tpa(CONHPEGglucose)1}]+ by rapidly dividing cells, followed by release and efflux of C343ha and trapping of the Co{tpa(CONHPEGglucose)1} moiety. The Co{tpa(CONHPEGglucose)1} moiety is shown to have potential for the caged and targeted delivery of highly toxic anticancer agents.

Synthesis of N-acetyl Glucosamine Analogs as Inhibitors for Hyaluronan Biosynthesis

Elevated hyaluronan expression is a hallmark of many types of cancer. Therefore, inhibition of hyaluronan biosynthesis can potentially slow the growth of tumor cells. Herein, we explore a chain termination strategy to reduce hyaluronan synthesis by tumor cells. Several analogs of glucosamine were prepared, which contained modifications at the C-3 positions. These analogs can possibly cap the nonreducing end of a growing hyaluronan chain, thus lowering the amount of hyaluronan synthesized. Upon incubation with pancreatic cancer cells, a fluorine-containing glucosamine analog was found to exhibit significant inhibitory activities of hyaluronan synthesis. Furthermore, it drastically reduced the proliferation of cancer cells. Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Carbohydrate Chemistry to view the supplemental file.

Synthesis of oligonucleotides with glucosamine at the 3′-position and evaluation of their biological activity

Short interfering RNA (siRNA) has been proven to be an utilizable tool for post-transcriptional gene silencing research. In this study, we designed and synthesized two glucosamine analogues and tried to modify the siRNA using these two glucosamine analogues at the 3′-overhang region of siRNAs to improve the nuclease resistance and to overcome some other weak points. The siRNAs modified with glucosamine analogues had almost no effect of the thermal stability and showed strong resistance to nuclease degradation. Some of them kept the same gene silencing activity level as unmodified siRNA.

Glucosamine and Glucosamine-6-phosphate Derivatives: Catalytic Cofactor Analogues for the glmS Ribozyme

Two analogues of glucosamine-6-phosphate (GlcN6P, 1) and five of glucosamine (GlcN, 2) were prepared for evaluation as catalytic cofactors of the glmS ribozyme, a bacterial gene-regulatory RNA that controls cell wall biosynthesis. Glucosamine and allosamine with 3-azido substitutions were prepared by SN2 reactions of the respective 1,2,4,6-protected sugars; final acidic hydrolysis afforded the fully deprotected compounds as their TFA salts. A 6-phospho-2-aminoglucolactam (31) was prepared from glucosamine in a 13-step synthesis, which included a late-stage POCl3-phosphorylation. A simple and widely applicable 2-step procedure with the triethylsilyl (TES) protecting group was developed to selectively expose the 6-OH group in N-protected glucosamine analogues, which provided another route to chemical phosphorylation. Mitsunobu chemistry afforded 6-cyano (35) and 6-azido (36) analogues of GlcN-(Cbz), and the selectivity for the 6-position was confirmed by NMR (COSY, HMBC, HMQC) experiments. Compound 36 was converted to the fully deprotected 6-azido-GlcN (37) and 2,6-diaminoglucose (38) analogues. A 2-hydroxylamino glucose (42) analogue was prepared via an oxaziridine (41). Enzymatic phosphorylation of 42 and chemical phosphorylation of its 6-OH precursor (43) were possible, but 42 and the 6-phospho product (44) were unstable under neutral or basic conditions. Chemical phosphorylation of the previously described 2-guanidinyl-glucose (46) afforded its 6-phospho analogue (49) after final deprotection.

Molecular Imaging Kits for Hexosamine Biosynthetic Pathway in Oncology

Noninvasive imaging assessment of tumor cell proliferation could be helpful in the evaluation of tumor growth potential, the degree of malignancy, and could provide an early assessment of treatment response prior to changes in tumor size determined by computed tomography (CT), magnetic resonance imaging (MRI), Positron emission tomography (PET), Single-Photon emission computed tomography (SPECT) or ultrasonography, respectfully. Understanding of tumor proliferative activity, in turn, could aid in the selection of optimal therapy by estimating patient prognosis and selecting the proper management. PET/CT imaging of (18)F-fluoro-2-deoxy-glucose (FDG) is recognized as a technology for diagnosing the presence and extent of several cancer types. Recently, radiolabeled glucosamine analogues were introduced as a promising SPECT agent to complement FDG imaging to increase specificity and improve the accuracy of lesion size in oncology applications. Radiolabeled glucosamine analogues were developed to localize in the nuclear components of cells primarily via the hexosamine biosynthetic pathway whereas glucose localizes in the cytoplasm of cells through the glycolytic/TCA pathway. This paper reviews novel kit-based radiolabeled glucosamine analogues for metabolic imaging of tumor lesions. The novel radiolabeled glucosamine analogues may increase the specificity in oncology applications and can influence patient diagnosis, planning and monitoring of cancer treatment.

Getting to know the nitrogen next door: HNMBC measurements of amino sugars

Long-range 1H– 15N correlations detected by the heteronuclear multiple-bond correlation (HMBC) experiment are explored for the characterization of amino sugars. The gradient-enhanced HMBC, IMPACT-HMBC, and a modified pulse sequence with the 1 J-filters removed, IMPACT-HNMBC, are compared for sensitivity and resolution. 15N chemical shifts and long-range proton correlations are reported using the IMPACT-HNMBC experiment for N-acetyl-glucosamine, N-acetyl-galactosamine, and for a series of glucosamine analogs with an N-sulfo substitution, unmodified amino group, and 6- O-sulfonation. As is common with sugars, for all the compounds examined both anomeric forms are present in solution. For each compound studied, the 15N chemical shifts of the α anomer are downfield of the β form. For the N-acetylated sugars, the β anomer has a unique long-range 15N correlation to the anomeric proton not observed for the α anomer. Though N-sulfonation results in a significant change in the 15N chemical shift of the glucosamine analogs, 6- O sulfo substitution has no significant effect on the local environment of the amino nitrogen. For N-acetylated sugars in D 2O solution, peaks in the 15N projection of the HMBC spectrum appear as triplets as a result of J-modulation due to 2H– 15N coupling.

Glucosamine Regulates Differentiation of a Chondrogenic Cell Line, ATDC5

Osteoarthritis (OA) is a slowly progressing chronic joint disease. Glucosamine (GlcN) is a saccharide that is widely used to relieve symptoms associated with OA. However, the mechanism of the effects of GlcN on articular cartilage remains unclear. We studied the effects of GlcN and its analogues, including chitin derivatives included in health supplements containing GlcN, on a chondrogenic cell line, ATDC5. We examined the effects of these saccharides on the proliferation and differentiation of ATDC5 cells. Glucosamine analogues, such as N-acetyl glucosamine and chitobiose, did not affect the proliferation or differentiation of ATDC5 cells. While GlcN did not affect the proliferation of ATDC5 cells, it inhibited their differentiation. Next, we examined whether GlcN affects mineralization and glycosaminoglycan (GAG) production by ATDC5 cells. Mineralization was markedly inhibited by addition of GlcN to the cell culture medium. Moreover, GlcN induced the formation of sulfated GAG in ATDC5. We also analyzed the mRNA levels in ATDC5 cells. GlcN reduced the mRNA levels of Smad2, Smad4 and MGP. GlcN might inhibit expression of MGP mRNA and induce the production of chondroitin sulfate in ATDC5 cells. The mechanism by which GlcN inhibits mineralization may be by regulating the expression of mRNA for the Smad2 and Smad4 chondrogenic master genes.

N-butyryl glucosamine increases matrix gene expression by chondrocytes.

Proteoglycan synthesis is dependent on N-acetyl glucosamine (GlcNAc) produced by the hexosamine biosynthetic pathway or obtained exogenously. Although used therapeutically to relieve symptoms of osteoarthritis, the actions of glucosamine and its analogs on cartilage are poorly understood. The purpose of this study was to determine the effects on chondrocytes of N-acylated-glucosamine analogs bearing alkyl chains of different lengths. Chondrocytes isolated from neonatal rat femoral condyles were cultured in the presence of glucosamine analogs. GlcNAc, N-proprionyl glucosamine (GlcNPro), or N-butyryl glucosamine (GlcNBu) did not alter cell number, lactate dehydrogenase release, or metabolic acid production, consistent with lack of cytotoxicity. Treatment of chondrocyte cultures with GlcNBu for 6 days significantly increased levels of type II collagen and aggrecan mRNA as determined by Northern blot analysis. In contrast, GlcNAc and GlcNPro had no significant effect. A significant increase in type II collagen mRNA was induced by GlcNBu within 3 days. GlcNBu did not alter stability of type II collagen mRNA, suggesting it acts on gene transcription. We have previously shown that tumor necrosis factor-alpha (TNFalpha) decreases levels of type II collagen mRNA. However, chondrocytes pretreated with GlcNBu maintained type II collagen mRNA at control levels in the presence of TNFalpha. These results establish that the N-butyrylated analog of glucosamine but not GlcNAc promotes matrix gene expression by chondrocytes. Thus, GlcNBu has the potential for use as a chondro-protective agent in osteoarthritis.

Inhibition of lectin-mediated ovarian tumor cell adhesion by sugar analogs.

Adhesion of A-121 human ovarian carcinoma cells to extracellular matrix is partly mediated via interaction between galaptin, an endogenous beta-galactoside-binding lectin present in extracellular matrix, and specific cell surface carbohydrate receptors identified as lysosomal associated membrane proteins, lamp-1 and lamp-2. In this study, we report that adhesion of human ovarian carcinoma cells to polystyrene plates coated with polymerized human splenic galaptin can be inhibited by polyclonal antibodies raised against lamp-1 and lamp-2 molecules and by pretreatment of A-121 human ovarian carcinoma cells with glucosamine analogs: 2-acetamido-1,4,6-tri-O-acetyl-3- deoxy-3-fluoro-alpha-D-glucopyranose (3-F-GlcNAc) and 2-acetamido-1,3,6-tri-O-acetyl-4-deoxy-4-fluoro-alpha-D-glucopyranose (4-F-GlcNAc). A 48-h exposure of A-121 cells to individual sugar analogs, or to a combination of the two, resulted in a concentration-dependent inhibition of cellular attachment to polymerized galaptin. Both drugs inhibited glycoprotein biosynthesis as measured by cellular incorporation of labeled [3H]glucosamine and [3H]fucose with negligible effects on [3H]thymidine and [3H]leucine incorporation and cell growth. As a result of drug action on glycoprotein biosynthesis, an alteration in the structure of the galaptin receptor was noted by indirect immunofluorescence and Western blot analysis. Moreover, probing gels of cell extracts with anti-lamp antibodies or Datura stramonium lectin demonstrated significant changes in the reactivity and pattern of glycoprotein staining, suggesting an effect of sugar analogs on the glycosylation of various cellular receptor molecules. The greatest change was observed when tumor cells were exposed to a combination of the two sugar analogs. These studies suggest that specific endogenous lectins and their surface receptors play a role in tumor cell adhesion and perhaps metastasis and may serve as suitable targets for therapeutic exploitation.