Two novel aspirin analogues show selective cytotoxicity in primary chronic lymphocytic leukaemia cells that is associated with dual inhibition of Rel A and COX-2.

OBJECTIVES: Non-steroidal anti-inflammatory drugs have been shown to induce apoptosis in primary B-cell chronic lymphocytic leukaemia (CLL) cells, but the molecular mechanisms that underpin this observation have not been fully elucidated. Here, we have analysed the effect two novel aspirin analogues, 2-hydroxy benzoate zinc (2HBZ) and 4-hydroxy benzoate zinc (4HBZ), on primary CLL samples. MATERIALS AND METHODS: Cytotoxic effects of 2HBZ and 4HBZ were analysed in primary CLL cells derived from 52 patients, and normal B- and T-lymphocytes. Mechanisms of action of these agents were also elucidated. RESULTS: Both analogues induced apoptosis in a dose-dependent and time-dependent manner. Apoptosis was associated with activation of caspase-3 that could be partially abrogated by the caspase-9 inhibitor (Z-LEHD.fmk). Importantly, both agents demonstrated preferential cytotoxicity in CLL cells when compared to normal B- and T-lymphocytes. In terms of their molecular mechanisms of action, 4HBZ and 2HBZ inhibited COX-2 transcription and protein expression and this was associated with upstream inhibition of transcription factor Rel A. Co-culture of CLL cells with CD40 ligand-expressing mouse fibroblasts significantly increased COX-2 expression and inhibited spontaneous apoptosis. Importantly, the most potent analogue, 4HBZ, overcame pro-survival effects of the co-culture system and significantly repressed COX-2. Finally, elevated COX-2 expression was associated with poor prognostic subsets and increased sensitivity to 4HBZ. CONCLUSIONS: Our results demonstrate therapeutic potential of 4HBZ and are consistent with a mechanism involving suppression of Rel A nuclear translocation and inhibition of COX-2 transcription.

Sub-millimolar concentration of the novel phenol-based compound, 2-hydroxy benzoate zinc, induces apoptosis in human HT-1080 fibrosarcoma cells.

OBJECTIVES: To examine the effect of a novel phenolic-based compound, 2-hydroxy benzoate zinc (2HBZ), and acetylsalicylic acid (ASA) on human HT-1080 fibrosarcoma cells. MATERIALS AND METHODS: MTT assay was used to assess cell proliferation while different methods were used to detect apoptosis morphologically and immunohistochemically in Human HT-1080 fibrosarcoma cells. Apoptosis was determined by Annexine-V labelling, and caspase-3 activation. In addition, western blot was used to analyse p21, p53 and Bax and flow cytometry was to analyse the cell cycle. RESULTS: 2HBZ exhibited a more than 5-fold increase in cytotoxic potency when compared with ASA with mean LD50 values of 210 and 1100 lM respectively (P < 0.0001). The cytotoxic effects of 2HBZ were both time- and dosedependent with marked apoptosis being evident only after 24 h at concentrations as low as 200 mM. In contrast, ASA-induced apoptosis was observed only at concentrations in excess of 1000 mM at the same time point. Both 2HBZ and ASA induced caspase-3 activation in the cells, which confirmed that their cytotoxic effects were the result of apoptotic cell death. These findings were further confirmed by immunomorphological studies for the detection of apoptosis including haematoxylineosin, methyl green/pyronin Y staining and scanning electron microscopy. In addition, 2HBZ caused a marked increase in p21, p53 and Bax protein expressions and these effects were associated with an increase in G1 and G2 arrest of the cell cycle and a reduction in S-phase. CONCLUSIONS: These results demonstrate that the novel phenolic compound 2HBZ is a potent apoptosis-inducing agent in HT-1080 cells and warrants further investigation as a potential chemotherapeutic agent in primary cancer cell models.

Calcium salicylate-mediated apoptosis in human HT-1080 fibrosarcoma cells.

Salicylates are novel biologically active compounds that exhibit multiple therapeutic activities. The anti-cancer effectiveness of calcium salicylate has been investigated on human HT-1080 fibrosarcoma cell lines at relatively low concentrations (predominantly 0.4 mM) compared to those previously reported. Although low calcium salicylate concentrations did not retard tumour growth progression significantly, as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and time-lapse assays, its cytotoxic characteristics were proven to be prominent by various morphological and immunocytological techniques. The results here demonstrate evidence for approximately 25% apoptosis after treatment with calcium salicylate, which up-regulatd the expression of p53, p21 and Bax, and down-regulated Bcl-2 in HT-1080 cells.

The historical analysis of aspirin discovery, its relation to the willow tree and antiproliferative and anticancer potential.

For several millennia, the willow tree and salicin have been associated with salicylic acid, the key precursor molecule that has contributed to the discovery of acetylsalicylic acid, traded as aspirin. These molecules have been shown to possess phyto- and chemotherapeutic activities as analgesic drugs. In recent decades, aspirin has become the focus of extensive investigation into antiproliferative and anticancer activities. The historical steps that led to the discovery of aspirin, and its antiproliferative and anticancer potential are highlighted in this review.

Pharmacological importance of stereochemical resolution of enantiomeric drugs.

Drug enantiomers have identical properties in an achiral environment, but should be considered as different chemical compounds. This is because they often differ considerably in potency, pharmacological activity and pharmacokinetic profile, since the modules with which they interact in biological systems are also optically active. Within biological systems, the metabolism of one isomer may be via a different pathway or occur at a different rate from that of the other isomer. Preferential binding of one isomer to plasma proteins may cause differences in circulating free drug and hence alter concentrations at active sites. Interactions of both isomers may differ at the active sites through which pharmacological action is mediated. Actions and levels of activity of the stereoisomers in vivo may also differ. All the pharmacological activity may reside in a single enantiomer, whereas several possibilities exist for the other enantiomer-- it may be inactive, have a qualitatively different effect, an antagonistic effect or produce greater toxicity. Two isomers may have nearly identical qualitative pharmacological activity, qualitatively similar pharmacological activity but quantitatively different potency, or qualitatively different pharmacological activity. To avoid adverse effects and optimise the therapeutic value of enantiomeric drugs, it is necessary that methods for the resolution of racemates be evolved and devolved to determine isomeric purity, establish the effectiveness of isomers of the drug, and detect the presence of an enantiomer with lower therapeutic activity and undesirable adverse effects. Even if a drug is given as a pure enantiomer, methods to discriminate between enantiomers are required because racemisation can occur both in vitro and in vivo. Methods developed for resolution of drug enantiomers should facilitate routine testing of single isomers and their metabolites, studies of pharmacological, toxicological and clinical effectiveness, routine analysis of racemates, pure enantiomers or intermediates in manufacturing processes, and investigation of the potential for inversion of an enantiopure drug substance during the early stages of drug development and therapeutic drug monitoring.