The role of cordycepin in cancer treatment via induction or inhibition of apoptosis: Implication of polyadenylation in a cell type specific manner

Purpose: Most anticancer drugs show their antiproliferative and cytotoxic activity via induction of apoptosis. In the present study we assessed the implication and role of cordycepin, a polyadenylation-specific inhibitor and a well-known chemotherapeutic drug, in apoptosis, induced by the anticancer drug etoposide. Methods: For this purpose, a variety of leukemia and lymphoma cell lines (U937, K562, HL-60, Daudi, Molt-4) were treated with the anticancer drugs etoposide and/or cordycepin and assessed for poly(A) polymerase (PAP) activity and isoforms by the highly sensitive PAP activity assay and western blotting, respectively. Induction of apoptosis was determined by endonucleosomal DNA cleavage, DAPI staining, caspase-6 activity assay and ΔΨm reduction, whereas cytotoxicity and cell cycle status were assessed by Trypan blue staining, MTT assay and flow cytometry. Results and conclusions: The results showed that PAP changes in all cell lines, in response to apoptosis induced by etoposide, in many cases even prior to hallmarks of apoptosis (endonucleosomal cleavage of DNA, ΔΨm reduction). A further elucidation to this apoptosis-polyadenylation correlation was added, by cell treatment with cordycepin, resulting in either suppression (U937, K562) or induction (HL-60) of the apoptotic process, according to the cell type. However, inhibition of polyadenylation did not influence the cell lines Daudi and Molt-4 used, where alternative apoptotic pathways are induced through cleavage of DNA into high molecular weight fragments. © 2007 Springer-Verlag

Effect of end group on the micelle properties of diblock copolymers of ethylene oxide and 1,2-butylene oxide

Copolymers of ethylene oxide and 1,2-butylene oxide (E18B10, E43B9, E40B10, E90B10, E96B18E184B18, E = oxyethylene unit, B = oxybutylene unit, subscripts denote number-average chain lengths) with B blocks terminated by hydroxy groups (denoted EmBnH)were methylated to provide copolymers having the same chain length and composition but with B blocks terminated by methoxy groups (denoted EmBnM). Micelle properties of the M copolymers were determined by dynamic and static light scattering (hydrodynamic radius, association number, thermodynamic radius) and the values obtained compared with those for the H copolymers, most of which had been published previously. The results for copolymer E18B10M in solution at 40°C were consistent with the formation of worm-like micelles, the micelles of the other copolymers being spherical, including E18B10H in solution at 40°C and E18B10M in solution at 30°C. For micelles of the B18 copolymers, methylation reduced the values of all properties by ca. 10%. For micelles of the B9-B10 copolymers, the effect of methylation was to reduce the hydrodynamic radius by ca. 10%, but to increase the association number by ca. 25% and thermodynamic radius by ca. 10%. The explanation of these effects takes into account the increased hydrophobicity of the methylated B blocks, the highly stretched state of the B18 blocks in their micelles, and the probability that water will concentrate at the centre of the cores of micelles of copolymers with hydroxy-ended B blocks. For copolymers forming spherical micelles, the effect of methylation on association number is equivalent to raising the temperature of the solution by ca. 10°C. For micelles of copolymer E18B10, the effect of methylation is to lower the temperature of the sphere-to-worm transition from 40-50° (E18B10H) to 30-40°C (E18B10M)

Aqueous solutions and gels of diblock copolymers of 1,2-butylene oxide and ethylene oxide studied by light scattering and rheology

Copolymers B20E430, B20E510, and B20E610 (B = oxybutylene repeat unit, E = oxyethylene repeat unit, subscripts indicate chain length in repeat units) were synthesized and characterized by gel permeation chromatography (for distribution width) and 13C NMR spectroscopy (for absolute molar mass and composition). Dynamic and static light scattering were used to determine micellar properties in dilute aqueous solution: e.g., micelle association numbers and radii. A tube-inversion method was used to define the mobile-immobile (hard gel) phase boundary. For copolymer B20E610, immobile gels form at concentrations as low as 2.9 wt %. Rheological measurements of dynamic modulus and yield stress served to characterize the gel properties and to confirm the phase boundaries. The results are combined with those from previous work on related block copolymers to obtain scaling relationships for the dependence of micellar and gel properties on E-block length, thus enabling prediction of the requirements for and properties of very dilute aqueous gels. The validity of treating the micelles as hard spheres is discussed

Association properties of a diblock copolymer of ethylene oxide and styrene oxide in aqueous solution studied by light scattering and rheometry

Copolymer S13E60 (E = oxyethylene unit, S = oxyphenylethylene unit) was synthesised and characterised by gel permeation chromatography (for distribution width) and 13C NMR spectroscopy (for absolute molar mass and composition). Dynamic and static light scattering were used to determine micellar properties in dilute aqueous solution at three temperatures (20, 30 and 40 °C): i.e. association number, hydrodynamic and thermodynamic radii. Comparison with reported results for related copolymers allowed exploration of the dependence of these properties on hydrophobe block length. The phase behaviour of the copolymer in aqueous solution was defined using tube inversion and rheometry (for yield stress and dynamic modulus). The hard-gel boundary was detected by both methods in satisfactory agreement. Discussion is focused on effects of micelle stability on the shape and extent of the hard-gel region of the phase diagram. A region of soft gel was detected at low concentrations by rheometry, and assigned to a percolation mechanism

Rheology and structures of aqueous gels of diblock(oxyethylene/oxybutylene) copolymer E22B7

The phase behavior of an oxyethylene/oxybutylene diblock copolymer (E22B7) in aqueous solution was defined using three properties: yield stress (by rheometry and tube inversion), dynamic modulus (by rheometry), and structure (by small-angle X-ray scattering). The boundary of immobile, structured gel (hard gel) was detected by all three methods, giving satisfactory agreement. A structural transition within the hard gel, from bcc to hex, was detected by rheometry and SAXS. Two types of soft gel were detected and assigned to disordered phases containing either spherical or cylindrical micelles. Comparison with results for other diblock EmBn copolymers showed a regularity of behavior influenced largely by oxyethylene-block length, with oxybutylene-block length having a minor but significant role. © 2000 American Chemical Society

Chain folding in semicrystalline oxybutylene/oxyethylene/oxybutylene triblock copolymers studied by Raman spectroscopy

The chain-folding behavior of short oxybutylene/oxyethylene/oxybutylene triblock copolymers with one crystallizable E block and two noncrystallizable B blocks has been studied by low-frequency Raman spectroscopy in combination with small-angle X-ray scattering and differential scanning calorimetry. The advantage of using Raman spectroscopy in this application is demonstrated. The results point to folded-chain conformations in which the oxyethylene blocks are orientated normal to the lamellar end plane. It is probable that the oxybutylene blocks are similarly orientated. Comparison is made with related results for short oxypropylene/oxyethylene/oxypropylene triblock copolymers

Rheology and structure of aqueous gels of diblock (oxyethylene/oxybutylene) copolymers with lengthy oxyethylene blocks

Aqueous solutions of diblock copolymers E96B18, E184B18, E315B17 and E398B19 (E=oxyethylene unit, B=oxybutylene unit) were investigated by rheometry and small-angle X-ray scattering (SAXS). Storage (G′) and loss (G″) modulus and yield strength (σy) were used to define hard- and soft-gel phases in experiments which covered the concentration range 2–14 wt.% copolymer. Values of G′ correlated with those of yield strength, the ratio G′/σy being ca. 0.03. SAXS was used to explore hard-gel structures, and to confirm hard-gel/soft-gel boundaries. The sol/soft-gel boundary was identified as a percolation threshold. The effect of an increase in E-block length was to move the gel phases to lower concentrations without changing the pattern of their behaviour. In this respect, the critical conditions for hard-gel formation (c*, T*) served as parameters for a ‘universal ’ phase diagram