Apoptosis is the major form of cell death associated with the action of chemotherapeutic agents on tumor cells, and therefore the expression of genes that interfere with apoptosis can have important consequences for the efficacy of therapeutic approaches. Here we show that K562, a chronic myelogenous leukemia (CML) cell line expressing the BCR-ABL fusion protein, are resistant to the induction of apoptosis by a number of agents and conditions. Antisense oligodeoxynucleotides corresponding to the translation start of bcr downregulate bcr-abl protein in these cells and render them susceptible to induction of apoptosis by chemotherapeutic agents or serum deprivation. Expression of a temperature sensitive v-Abl protein reverses the effects of the antisense oligonucleotides, such that the cells remain resistant to apoptosis at the permissive temperature. These data indicate that bcr- abl acts as an anti-apoptosis gene in CML cells and suggests that the effect is dependent on the abl kinase activity in this chimeric protein. Inhibition of bcr-abl to render CML cells susceptible to apoptosis can be combined with therapeutic drugs and/or treatment capable of inducing apoptosis to provide an effective strategy for elimination of these cells.

Histone demethylases LSD1 JMJC Lysine demethylase A B S T R A C TReversible histone methylation has emerged in the last few years as an important mechanism of epigenetic regulation. Histone methyltransferases and demethylases have been identified as contributing factors in the development of several diseases, especially cancer. Therefore, they have been postulated to be new drug targets with high therapeutic potential. Here, we review histone demethylases with a special focus on their potential role in oncology drug discovery. We present an overview over the different classes of enzymes, their biochemistry, selected data on their role in physiology and already available inhibitors.ª 2012 Federation of European Biochemical Societies.Published by Elsevier B.V. All rights reserved. IntroductionHistone methylation had long been thought to be an irreversible process but since (Metzger et al., 2005Shi et al., 2004) it is known that histones, but also other proteins (Huang et al., 2007a;Nicholson and Chen, 2009), are also subject to active enzymatic demethylation (Agger et al., 2008). Reversible histone methylation has been shown to be involved in gene regulation and hence is interesting as a target for therapeutic intervention (Shi, 2007;Yoshimi and Kurokawa, 2011). Very rapidly inhibitors of these enzymes were identified and already show promise for drug development (Lohse et al., 2011a;Spannhoff et al., 2009a). Here, we present an overview over the different classes of histone demethylases, their biochemistry, selected evidence for their role in oncogenesis and inhibitor studies. Reversible histone methylationMethylation of histones occurs posttranslationally both on lysines as well as arginines (Trievel, 2004). Methyltransferases use the cofactor S-adenosyl methionine (SAM) to transfer a methyl group onto the basic side chains of these amino acids within proteins.

The mechanism of titanocene-mediated epoxide opening was studied by a combination of voltammetric, kinetic, computational, and synthetic methods. With the aid of electrochemical investigations the nature of a number of Ti(III) complexes in solution was established. In particular, the distribution of monomeric and dimeric Ti(III) species was found to be strongly affected by the exact steric conditions. The overall rate constants of the reductive epoxide opening were determined for the first time. These data were employed as the basis for computational studies of the structure and energies of the epoxide-titanocene complexes, the transition states of epoxide opening, and the beta-titanoxy radicals formed. The results obtained provide a structural basis for the understanding of the factors determining the regioselectivity of ring opening and match the experimentally determined values. By employing substituted titanocenes even more selective epoxide openings could be realized. Moreover, by properly adjusting the steric demands of the catalysts and the substrates the first examples of reversible epoxide openings were designed.

NAD(+)-dependent histone deacetylases (sirtuins) play important roles in epigenetic regulation but also through nonhistone substrates for other key cellular events and have been linked to the pathogenesis of cancer, neurodegeneration, and metabolic diseases. The subtype Sirt5 has been shown recently to act as a desuccinylating and demalonylating enzyme. We have established an assay for biochemical testing of Sirt5 using a small labeled succinylated lysine derivative. We present a comparative study on the profiling of several established sirtuin inhibitors on Sirt1-3 as well as Sirt5 and also present initial results on a screening for new compounds that block Sirt5. Thiobarbiturates were identified as new Sirt5 inhibitors in the low micromolar range, which are selective over Sirt3 that can be found in the same cell compartment as Sirt5.

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