Chromatin is a dynamic macromolecular structure epigenetically modified to regulate specific gene expression. Altered chromatin function can lead to aberrant expression of growth regulators and may, ultimately, cause cancer. That many human diseases have epigenetic etiology has stimulated the development of 'epigenetic' therapies. Inhibitors of histone deacetylases (HDACIs) induce proliferation arrest, maturation and apoptosis of cancer cells, but not normal cells, in vitro and in vivo, and are currently being tested in clinical trials. We investigated the mechanism(s) underlying this tumor selectivity. We report that HDACIs induce, in addition to p21, expression of TRAIL (Apo2L, TNFSF10) by directly activating the TNFSF10 promoter, thereby triggering tumor-selective death signaling in acute myeloid leukemia (AML) cells and the blasts of individuals with AML. RNA interference revealed that the induction of p21, TRAIL and differentiation are separable activities of HDACIs. HDACIs induced proliferation arrest, TRAIL-mediated apoptosis and suppression of AML blast clonogenicity irrespective of French-American-British (FAB) classification status, karyotype and immunophenotype. No apoptosis was seen in normal CD34(+) progenitor cells. Our results identify TRAIL as a mediator of the anticancer action of HDACIs.

AKR1B10 is a human aldo-keto reductase (AKR) found to be elevated in several cancer types and in precancerous lesions. In vitro, AKR1B10 exhibits a much higher retinaldehyde reductase activity than any other human AKR, including AKR1B1 (aldose reductase). We here demonstrate that AKR1B10 also acts as a retinaldehyde reductase in vivo. This activity may be relevant in controlling the first step of retinoic acid synthesis. Up-regulation of AKR1B10, resulting in retinoic acid depletion, may lead to cellular proliferation. Both in vitro and in vivo activities of AKR1B10 were inhibited by tolrestat, an AKR1B1 inhibitor developed for diabetes treatment. The crystal structure of the ternary complex AKR1B10 -NADP ؉ -tolrestat was determined at 1.25-Å resolution. Molecular dynamics models of AKR1B10 and AKR1B1 with retinaldehyde isomers and site-directed mutagenesis show that subtle differences at the entrance of the retinoid-binding site, especially at position 125, are determinant for the all-transretinaldehyde specificity of AKR1B10. Substitutions in the retinaldehyde cyclohexene ring also influence the specificity. These structural features should facilitate the design of specific inhibitors, with potential use in cancer and diabetes treatments.aldo-keto reductases ͉ aldose reductase ͉ protein structure ͉ retinoic acid ͉ tolrestat

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A DFT study of R-R reductive elimination (R = Me, Ph, vinyl) in plausible intermediates of Pd-catalyzed processes is reported. These include the square-planar tetracoordinated systems cis-[PdR(2)(PMe(3))(2)] themselves, possible intermediates cis-[PdR(2)(PMe(3))L] formed in solution or upon addition of coupling promoters (L = acetonitrile, ethylene, maleic anhydride (ma)), and tricoordinated intermediates cis-[PdR(2)(PMe(3))] (represented as L = empty). The activation energy ranges from 0.6 to 28.6 kcal/mol in the gas phase, increasing in the order vinyl-vinyl < Ph-Ph < Me-Me, depending on R, and ma < "empty" < ethylene < PMe(3) approximately MeCN, depending on L. The effect of added olefins was studied for a series of olefins, providing the following order of activation energy: p-benzoquinone < ma < trans-1,2-dicyanoethylene < 3,5-dimethylcyclopent-1-ene < 2,5-dihydrofuran < ethylene < trans-2-butene. Comparison of the calculated energies with experimental data for the coupling of cis-[PdMe(2)(PPh(3))(2)] in the presence of additives (PPh(3), p-benzoquinone, ma, trans-1,2-dicyanoethylene, 2,5-dihydrofuran, and 1-hexene) reveals that: (1) There is no universal coupling mechanism. (2) The coupling mechanism calculated for cis-[PdMe(2)(PMe(3))(2)] is direct, but PPh(3) retards the coupling for cis-[PdMe(2)(PPh(3))(2)], and DFT calculations support a switch of the coupling mechanism to dissociative for PPh(3). (3) Additives that would provide intermediates with coupling activation energies higher than a dissociative mechanism (e.g., common olefins) produce no effect on coupling. (4) Olefins with electron-withdrawing substituents facilitate the coupling through cis-[PdMe(2)(PR(3))(olefin)] intermediates with much lower activation energies than the starting complex or a tricoordinated intermediate. Practical consequences are discussed.

In the retinal rod and cone photoreceptors, light photoactivates rhodopsin or cone visual pigments by converting 11-cis-retinal to all-trans-retinal, the process that ultimately results in phototransduction and visual sensation. The production of 11-cis-retinal in adjacent retinal pigment epithelial (RPE) cells is a fundamental process that allows regeneration of the vertebrate visual system. Here, we present evidence that all-trans-retinol is unstable in the presence of H(+) and rearranges to anhydroretinol through a carbocation intermediate, which can be trapped by alcohols to form retro-retinyl ethers. This ability of all-trans-retinol to form a carbocation could be relevant for isomerization. The calculated activation energy of isomerization of all-trans-retinyl carbocation to the 11-cis-isomer was only approximately 18 kcal/mol, as compared to approximately 36 kcal/mol for all-trans-retinol. This activation energy is similar to approximately 17 kcal/mol obtained experimentally for the isomerization reaction in RPE microsomes. Mass spectrometric (MS) analysis of isotopically labeled retinoids showed that isomerization proceeds via alkyl cleavage mechanism, but the product of isomerization depended on the specificity of the retinoid-binding protein(s) as evidenced by the production of 13-cis-retinol in the presence of cellular retinoid-binding protein (CRBP). To test the influence of an electron-withdrawing group on the polyene chain, which would inhibit carbocation formation, 11-fluoro-all-trans-retinol was used in the isomerization assay and was shown to be inactive. Together, these results strengthen the idea that the isomerization reaction is driven by mass action and may occur via carbocation intermediate.

The mechanism of the stereospecific gold(I)-catalyzed Rautenstrauch rearrangement of (E)-1-ethynyl-2-methyl-but-2-en-yl acetate to 3,4-dimethyl-cyclopent-2-enone has been computationally addressed using DFT (B3LYP/6-31G, SDD for Au). Our results indicate that the bond formation event follows the Au(I)-induced acetyl transfer to the vicinal alkyne and that it is the helicity of the pentadienyl cation intermediate which keeps memory of the chiral information. The fidelity of the center-to-helix-to-center chirality transfer requires that the rates of helix interconversion and pivaloyl rotation are slower than the cyclization, as calculations predict.

On the basis of the observations that chalcone 7 (MX781) and some related adamantyl arotinoids (AdArs) inhibit IkappaB alpha kinase beta (IKKbeta) activity, inhibit cell growth, and induce apoptosis in cancer cells, a new series of AdArs structurally related to 7 have been designed and synthesized. Modifications were intended to reduce or eliminate RAR activity, and we evaluated the effect of the novel analogues of 7 on IKKbeta activity and proliferation of a variety of cancer cell lines (leukemia, Jurkat; prostate, PC-3; breast carcinomas, T47D, MDA-MB-468). Consistent with the design principles, the biological activities of these AdArs do not appear to be RAR-mediated, since most analogues are unable to activate RAR-mediated transactivation and exhibit significantly diminished antagonist activity. All compounds are capable of inducing apoptosis in Jurkat cells, as demonstrated by elevated DEVDase activity and externalization of phosphatidylserine. Several of the analogues elicit stronger growth inhibitory activity against prostate (PC-3) and breast (MDA-MB-468) carcinoma cells, which contain elevated basal IKK activity; this antiproliferative activity correlates with increased inhibition of recombinant IKKbeta in vitro, suggesting that the anticancer activities of these AdArs might be related to the inhibition of IKK/NFkappaB signaling.

Modern‐day wonders of the world: Nanostructured films of plasmonic pyramid arrays (see picture) were prepared by the simple stamping of preformed homogeneous nanocolloids. These materials show very high efficiency as optical enhancers and can be exploited for the design of quantitative, cheap, portable, and ultrasensitive optical sensors with excellent reversibility.