nystatin-a1 and Carcinoma

The (8'R) epimeric carbohydrate core 2 of amipurimycin was synthesized from D-glucose derived allylic alcohol 3 in 11 steps and 13% overall yield. The key steps involve an acid-catalyzed acetonide ring opening of 9 with concomitant formation of an unprecedented pyranose ring skeleton to give 2,7-dioxabicyclo[3.2.1]octane 10. The α-orientation of the furan ring in 10 readily allows the stereoselective β-glycosylation and opening of the furanose ring that on removal of protecting groups affords the pyranosyl adenine nucleoside 2. The antifungal and anticancer activities of 2 were studied.

Topics: Acids; Adenine; Antifungal Agents; Antineoplastic Agents; Carcinoma; Catalysis; Cell Proliferation; Female; Fungi; Glucose; Glycosylation; HeLa Cells; Humans; Nystatin; Octanes; Purines; Stereoisomerism; Structure-Activity Relationship; Uterine Cervical Neoplasms

The natural phytoalexin resveratrol (3, 5, 4'-trihydroxystilbene) exhibits both chemopreventive and antitumor activities through a variety of mechanisms. We have shown previously that resveratrol-induced apoptosis of a human colon cancer cell line involved the redistribution of CD95 (Fas/Apo-1) into lipid rafts. Here, we show that, in colon cancer cells that resist to resveratrol-induced apoptosis, the polyphenol also induces a redistribution of death receptors into lipid rafts. This effect sensitizes these tumor cells to death receptor-mediated apoptosis. In resveratrol-treated cells, tumor necrosis factor (TNF), anti-CD95 antibodies and TNF-related apoptosis-inducing ligand (TRAIL) activate a caspase-dependent death pathway that escapes Bcl-2-mediated inhibition. Resveratrol does not enhance the number of death receptors at the surface of tumor cells but induces their redistribution into lipid rafts and facilitates the caspase cascade activation in response to death receptor stimulation. The cholesterol sequestering agent nystatin prevents resveratrol-induced death receptor redistribution and cell sensitization to death receptor stimulation. Thus, whatever its ability to induce apoptosis in a tumor cell, resveratrol induces redistribution of death receptors into lipid rafts. This redistribution sensitizes the cells to death receptor stimulation. Such a sensitizing effect may be of therapeutic interest if TRAIL agonists are introduced in clinics.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Apoptosis Regulatory Proteins; Blotting, Western; Carcinoma; Caspases; Cell Line, Tumor; Colonic Neoplasms; fas Receptor; Flow Cytometry; Humans; Ligands; Lipid Metabolism; Lipids; Membrane Glycoproteins; Membrane Microdomains; Mitochondria; Nystatin; Proto-Oncogene Proteins c-bcl-2; Receptors, TNF-Related Apoptosis-Inducing Ligand; Receptors, Tumor Necrosis Factor; Resveratrol; Signal Transduction; Stilbenes; Time Factors; TNF-Related Apoptosis-Inducing Ligand; Transfection; Tumor Necrosis Factor-alpha

The present study was performed to examine the conductance properties in the colon carcinoma cell line HT29 and the activation of Cl- channels by cAMP. A modified cell-attached nystatin patch-clamp technique was used, allowing for the simultaneous recording of the cell membrane potential (PD) and the conductance properties of the cell-attached membrane. In resting cells, PD was -56 +/- 0.4 mV (n = 294). Changing the respective ion concentrations in the bath indicate that these cells possess a dominating K+ conductance and a smaller Cl- conductance. A significant non-selective cation conductance, which could not be inhibited by amiloride, was only observed in cells examined early after plating. The K+ conductance was reversibly inhibited by 1 - 5 mmol/l Ba2+. Stimulation of the cells by the secretagogues isoproterenol and vasointestinal polypeptide (VIP) depolarized PD and induced a Cl- conductance. Similar results were obtained with compounds increasing cytosolic cAMP: forskolin, 3-isobutyl-1-methylxanthine, cholera toxin and 8-bromoadenosine cyclic 3',5'-monophosphate (8-Br-cAMP). VIP (1 nmol/l, n = 10) and isoproterenol (1 mumol/l, n = 12) depolarized the cells dose-dependently and reversibly by 12 +/- 2 mV and 13 +/- 2 mV. The maximal depolarization was reached after some 20 s. The depolarization was due to increases in the fractional Cl- conductance. Simultaneously the conductance of the cell-attached membrane increased from 155 +/- 31 pS to 253 +/- 40 pS (VIP, n = 4) and from 170 +/- 43 pS to 268 +/- 56 pS (isoproterenol, n = 11), reflecting the gating of Cl- channels in the cell-attached membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adrenergic beta-Agonists; Carcinoma; Cell Membrane; Chlorides; Colonic Neoplasms; Cyclic AMP; Ion Channels; Nitrobenzoates; Nystatin; Tumor Cells, Cultured