Survivin counteracts the therapeutic effect of microtubule de-stabilizers by stabilizing tubulin polymers

<p>Abstract</p> <p>Background</p> <p>Survivin is a dual function protein. It inhibits the apoptosis of cells by inhibiting caspases, and also promotes cell growth by stabilizing microtubules during mitosis. Over-expression of survivin has been demonstrated to induce drug-resistance to various chemo-therapeutic agents such as cisplatin (DNA damaging agent) and paclitaxel (microtubule stabilizer) in cancers. However, survivin-induced resistance to microtubule de-stabilizers such as <it>Vinca </it>alkaloids and Combretastatin A-4 (CA-4)-related compounds were seldom demonstrated in the past. Furthermore, the question remains as to whether survivin plays a dominant role in processing cytokinesis or inhibiting caspases activity in cells treated with anti-mitotic compounds. The purpose of this study is to evaluate the effect of survivin on the resistance and susceptibility of human cancer cells to microtubule de-stabilizer-induced cell death.</p> <p>Results</p> <p>BPR0L075 is a CA-4 analog that induces microtubule de-polymerization and subsequent caspase-dependent apoptosis. To study the relationship between the expression of survivin and the resistance to microtubule de-stabilizers, a KB-derived BPR0L075-resistant cancer cell line, KB-<it>L30</it>, was generated for this study. Here, we found that survivin was over-expressed in the KB-<it>L30 </it>cells. Down-regulation of survivin by siRNA induced hyper-sensitivity to BPR0L075 in KB cells and partially re-stored sensitivity to BPR0L075 in KB-<it>L30 </it>cells. Western blot analysis revealed that down-regulation of survivin induced microtubule de-stabilization in both KB and KB-<it>L30 </it>cells. However, the same treatment did not enhance the down-stream caspase-3/-7 activities in BPR0L075-treated KB cells. Translocation of a caspase-independent apoptosis-related molecule, apoptosis-inducing factor (AIF), from cytoplasm to the nucleus was observed in survivin-targeted KB cells under BPR0L075 treatment.</p> <p>Conclusion</p> <p>In this study, survivin plays an important role in the stability of microtubules, but not with caspases inhibition. Over-expression of survivin counteracts the therapeutic effect of microtubule de-stabilizer BPR0L075 probably by stabilizing tubulin polymers, instead of the inhibition of caspase activity in cancer cells. Besides microtubule-related caspase-dependent cell death, caspase-independent mitotic cell death could be initiated in survivin/BPR0L075 combination treatments. We suggest that combining microtubule de-stabilizers with a survivin inhibitor may attribute to a better clinical outcome than the use of anti-mitotic monotherapy in clinical situations.</p

BPR1K653, a Novel Aurora Kinase Inhibitor, Exhibits Potent Anti-Proliferative Activity in MDR1 (P-gp170)-Mediated Multidrug-Resistant Cancer Cells

Over-expression of Aurora kinases promotes the tumorigenesis of cells. The aim of this study was to determine the preclinical profile of a novel pan-Aurora kinase inhibitor, BPR1K653, as a candidate for anti-cancer therapy. Since expression of the drug efflux pump, MDR1, reduces the effectiveness of various chemotherapeutic compounds in human cancers, this study also aimed to determine whether the potency of BPR1K653 could be affected by the expression of MDR1 in cancer cells.BPR1K653 specifically inhibited the activity of Aurora-A and Aurora-B kinase at low nano-molar concentrations in vitro. Anti-proliferative activity of BPR1K653 was evaluated in various human cancer cell lines. Results of the clonogenic assay showed that BPR1K653 was potent in targeting a variety of cancer cell lines regardless of the tissue origin, p53 status, or expression of MDR1. At the cellular level, BPR1K653 induced endo-replication and subsequent apoptosis in both MDR1-negative and MDR1-positive cancer cells. Importantly, it showed potent activity against the growth of xenograft tumors of the human cervical carcinoma KB and KB-derived MDR1-positive KB-VIN10 cells in nude mice. Finally, BPR1K653 also exhibited favorable pharmacokinetic properties in rats.BPR1K653 is a novel potent anti-cancer compound, and its potency is not affected by the expression of the multiple drug resistant protein, MDR1, in cancer cells. Therefore, BPR1K653 is a promising anti-cancer compound that has potential for the management of various malignancies, particularly for patients with MDR1-related drug resistance after prolonged chemotherapeutic treatments

Synthesis of 4-(1-oxo-isoindoline)-, 4-(5, 6-dimethoxy-1-oxo-isoindoline) and 4-acetamido-substituted phenoxy-3-amino-propane derivatives and their β₁-,β₂-adrenergic receptor binding studies

2808-2813In continuation to our previous study of 4-(1-oxo-isoindoline)-and 4-(5,6-dimethoxy-1-oxo-isoindoline)-substituted phenoxypropanolamine as potential cardioselective β-adrenergic blocking agents, the synthesis of 4-(1-oxo-isoindoline) and 4-(5,6-dimethoxy-1-oxo-isoindo line)-substituted phenoxy-3-amino-propane derivatives and their beta adrenoceptor binding affinity and selectivity in turkey erythrocyte membrane (β1) and lung homogenate of rats (β2) is reported. Also 4-acetamido substituted derivatives are synthesized and tested. All the tested compounds exhibit better cardioselectivity, with the 4-acetamido substituted derivatives being the most cardioselective. N-{4-[3-(3,4 Dimethoxyphenylethylamino)propoxy]phenyl}-1-oxo-isoindoline 7 hydrochloride shows β1-adrenergic receptor binding affinity lower than propranolol, but comparable to that of atenolol with better cardioselectivity. Compound 7 has been selected for further pharmacological investigations

Synthesis, -adrenergic receptor binding and antihypertensive potential of vanillin-derived phenoxypropanolamines

903-909Synthesis of vanillin-derived phenoxypropanolamines is carried out by condensing 4-hydroxy-3-methoxybenzaldehyde (vanillin) 1 with epichlorohydrin, followed by treatment with iso-propylamine or tert-butylamine to open the epoxy ring. Percentage inhibition of [³H]dihydroalprenolol binding to both β₁⁻ and β₂⁻adrenergic receptors by the newly synthesized compounds is assessed in vitro using turkey erythrocyte membrane (β₁) and lung homogenate of rats (β₂). Formyl derivatives 8 and 9 showed maximum inhibitory effect in binding assay and are non-selective similar to propranolol. On the other-hand, aldoxime compounds 10 and 11 have preference for 1-adrenergic receptors similar to atenolol. Also four of the compounds 8-11 are evaluated for their anti-hypertensive potential, in left renal artery ligation and fructose induced hypertension models. 4-(3-tert-Butylamino-2-hydroxy-propoxy)-3-methoxy-benzaldehyde oxime 11 shows antihypertensive effect better than propranolol

Impact of Genetic Variations in HIV-1 Tat on LTR-Mediated Transcription via TAR RNA Interaction

HIV-1 evades host defense through mutations and recombination events, generating numerous variants in an infected patient. These variants with an undiminished virulence can multiply rapidly in order to progress to AIDS. One of the targets to intervene in HIV-1 replication is the trans-activator of transcription (Tat), a major regulatory protein that transactivates the long terminal repeat promoter through its interaction with trans-activation response (TAR) RNA. In this study, HIV-1 infected patients (n = 120) from North India revealed Ser46Phe (20%) and Ser61Arg (2%) mutations in the Tat variants with a strong interaction toward TAR leading to enhanced transactivation activities. Molecular dynamics simulation data verified that the variants with this mutation had a higher binding affinity for TAR than both the wild-type Tat and other variants that lacked Ser46Phe and Ser61Arg. Other mutations in Tat conferred varying affinities for TAR interaction leading to differential transactivation abilities. This is the first report from North India with a clinical validation of CD4 counts to demonstrate the influence of Tat genetic variations affecting the stability of Tat and its interaction with TAR. This study highlights the co-evolution pattern of Tat and predominant nucleotides for Tat activity, facilitating the identification of genetic determinants for the attenuation of viral gene expression