DNA cleavage and antitumour activity of platinum(II) and copper(II) compounds derived from 4-methyl-2-N-(2-pyridylmethyl)aminophenol: spectroscopic, electrochemical and biological investigation

The reaction of the redox-active ligand, Hpyramol (4-methyl-2-N-(2-pyridylmethyl)aminophenol) with K2PtCl4 yields monofunctional square-planar [Pt(pyrimol)Cl], PtL-Cl, which was structurally characterised by single-crystal X-ray diffraction and NMR spectroscopy. This compound unexpectedly cleaves supercoiled double-stranded DNA stoichiometrically and oxidatively, in a non-specific manner without any external reductant added, under physiological conditions. Spectro-electrochemical investigations of PtL-Cl were carried out in comparison with the analogue CuL-Cl as a reference compound. The results support a phenolate oxidation, generating a phenoxyl radical responsible for the ligand-based DNA cleavage property of the title compounds. Time-dependent in vitro cytotoxicity assays were performed with both PtL-Cl and CuL-Cl in various cancer cell lines. The compound CuL-Cl overcomes cisplatin-resistance in ovarian carcinoma and mouse leukaemia cell lines, with additional activity in some other cells. The platinum analogue, PtL-Cl also inhibits cell-proliferation selectively. Additionally, cellular-uptake studies performed for both compounds in ovarian carcinoma cell lines showed that significant amounts of Pt and Cu were accumulated in the A2780 and A2780R cancer cells. The conformational and structural changes induced by PtL-Cl and CuL-Cl on calf thymus DNA and phi X174 supercoiled phage DNA at ambient conditions were followed by electrophoretic mobility assay and circular dichroism spectroscopy. The compounds induce extensive DNA degradation and unwinding, along with formation of a monoadduct at the DNA minor groove. Thus, hybrid effects of metal-centre variation, multiple DNA-binding modes and ligand-based redox activity towards cancer cell-growth inhibition have been demonstrated. Finally, reactions of PtL-Cl with DNA model bases (9-Ethylguanine and 5'-GMP) followed by NMR and MS showed slow binding at Guanine-N7 and for the double stranded self complimentary oligonucleotide d(GTCGAC)(2) in the minor groove

Non-traditional platinum compounds for improved accumulation, oral bioavailability, and tumor targeting

The five platinum anticancer compounds currently in clinical use conform to structure–activity relationships formulated (M. J. Cleare and J. D. Hoeschele, Bioinorg. Chem., 1973, 2, 187–210) shortly after the discovery that cis-diamminedichloroplatinum(II), cisplatin, has antitumor activity in mice. These compounds are neutral platinum(II) species with two am(m)ine ligands or one bidentate chelating diamine and two additional ligands that can be replaced by water through aquation reactions. The resulting cations ultimately form bifunctional adducts on DNA. Information about the chemistry of these platinum compounds and correlations of their structures with anticancer activity have provided guidance for the design of novel anticancer drug candidates based on the proposed mechanisms of action. This article discusses advances in the synthesis and evaluation of such non-traditional platinum compounds, including cationic and tumor-targeting constructs.National Cancer Institute (U.S.) (Grant CA34992

Structural Determination of Three Different Series of Compounds as Hsp90 Inhibitors Using 3D-QSAR Modeling, Molecular Docking and Molecular Dynamics Methods

Hsp90 is involved in correcting, folding, maturation and activation of a diverse array of client proteins; it has also been implicated in the treatment of cancer in recent years. In this work, comparative molecular field analysis (CoMFA), comparative molecular similarity indices analysis (CoMSIA), molecular docking and molecular dynamics were performed on three different series of Hsp90 inhibitors to build 3D-QSAR models, which were based on the ligand-based or receptor-based methods. The optimum 3D-QSAR models exhibited reasonable statistical characteristics with averaging internal q2 > 0.60 and external r2pred > 0.66 for Benzamide tetrahydro-4H-carbazol-4-one analogs (BT), AT13387 derivatives (AT) and Dihydroxylphenyl amides (DA). The results revealed that steric effects contributed the most to the BT model, whereas H-bonding was more important to AT, and electrostatic, hydrophobic, H-bond donor almost contributed equally to the DA model. The docking analysis showed that Asp93, Tyr139 and Thr184 in Hsp90 are important for the three series of inhibitors. Molecular dynamics simulation (MD) further indicated that the conformation derived from docking is basically consistent with the average structure extracted from MD simulation. These results not only lead to a better understanding of interactions between these inhibitors and Hsp90 receptor but also provide useful information for the design of new inhibitors with a specific activity

Platinum-(IV)-derivative satraplatin induced G2/M cell cycle perturbation via p53-p21(waf1/cip1)-independent pathway in human colorectal cancer cells

Platinum-(IV)-derivative satraplatin represents a new generation of orally available anti-cancer drugs that are under development for the treatment of several cancers. Understanding the mechanisms of cell cycle modulation and apoptosis is necessary to define the mode of action of satraplatin. In this study, we investigate the ability of satraplatin to induce cell cycle perturbation, clonogenicity loss and apoptosis in colorectal cancer (CRC) cells.Platinum-(IV)-derivative satraplatin represents a new generation of orally available anti-cancer drugs that are under development for the treatment of several cancers. Understanding the mechanisms of cell cycle modulation and apoptosis is necessary to define the mode of action of satraplatin. In this study, we investigate the ability of satraplatin to induce cell cycle perturbation, clonogenicity loss and apoptosis in colorectal cancer (CRC) cells

A systematic review of platinum and taxane resistance from bench to clinic: an inverse relationship

We undertook a systematic review of the pre-clinical and clinical literature for studies investigating the relationship between platinum and taxane resistance. Medline was searched for (1) cell models of acquired drug resistance reporting platinum and taxane sensitivities and (2) clinical trials of platinum or taxane salvage therapy in ovarian cancer. One hundred and thirty-seven models of acquired drug resistance were identified. 68.1% of cisplatin-resistant cells were sensitive to paclitaxel and 66.7% of paclitaxel-resistant cells were sensitive to cisplatin. A similar inverse pattern was observed for cisplatin vs. docetaxel, carboplatin vs. paclitaxel and carboplatin vs. docetaxel. These associations were independent of cancer type, agents used to develop resistance and reported mechanisms of resistance. Sixty-five eligible clinical trials of paclitaxel-based salvage after platinum therapy were identified. Studies of single agent paclitaxel in platinum-resistant ovarian cancer where patients had previously recieved paclitaxel had a pooled response rate of 35.3%, n=232, compared to 22% in paclitaxel naïve patients n=1918 (p<0.01, Chi-squared). Suggesting that pre-treatment with paclitaxel may improve the response of salvage paclitaxel therapy. The response rate to paclitaxel/platinum combination regimens in platinum-sensitive ovarian cancer was 79.5%, n=88 compared to 49.4%, n=85 for paclitaxel combined with other agents (p<0.001, Chi-squared), suggesting a positive interaction between taxanes and platinum. Therefore, the inverse relationship between platinum and taxanes resistance seen in cell models is mirrored in the clinical response to these agents in ovarian cancer. An understanding of the cellular and molecular mechanisms responsible would be valuable in predicting response to salvage chemotherapy and may identify new therapeutic targets

Telomere uncapping by the G-quadruplex ligand RHPS4 inhibits clonogenic tumour cell growth in vitro and in vivo consistent with a cancer stem cell targeting mechanism

The pentacyclic acridinium methosulfate salt RHPS4 induces the 3′single-stranded guanine-rich telomeric overhang to fold into a G-quadruplex structure. Stabilisation of the latter is incompatible with an attachment of telomerase to the telomere and thus G-quadruplex ligands can effectively inhibit both the catalytic and capping functions of telomerase. In this study, we examined mechanisms underlying telomere uncapping by RHPS4 in uterus carcinoma cells (UXF1138L) with short telomeres and compared the susceptibility of bulk and clonogenic cancer cells to the G-quadruplex ligand. We show that treatment of UXF1138L cells with RHPS4 leads to the displacement of the telomerase catalytic subunit (hTERT) from the nucleus, induction of telomere-initiated DNA-damage signalling and chromosome fusions. We further report that RHPS4 is more potent against cancer cells that grow as colonies in soft agar than cells growing as monolayers. Human cord blood and HEK293T embryonic kidney cell colony forming units, however, were more resistant to RHPS4. RHPS4-treated UXF1138L xenografts had a decreased clonogenicity, showed loss of nuclear hTERT expression and an induction of mitotic abnormalities compared with controls. Although single-agent RHPS4 had limited in vivo efficacy, a combination of RHPS4 with the mitotic spindle poison Taxol caused tumour remissions and further enhancement of telomere dysfunction

Genomic copy number and expression patterns in testicular germ cell tumours

Testicular germ cell tumours of adults and adolescents (TGCT) include seminomas (SE) and nonseminomas (NS), with spermatocytic seminomas (SSE) representing a distinct entity in older men. SE and NS have gain of 12p material in all cases, whereas SSE are associated with overrepresentation of chromosome 9. Here, we compare at the chromosomal level, copy number imbalances with global expression changes, identified by comparative expressed sequence hybridisation analyses, in seven SE, one combined tumour, seven NS and seven cell lines. Positive correlations were found consistent with copy number as a main driver of expression change, despite reported differences in methylation status in SE and NS. Analysis of chromosomal copy number and expression data could not distinguish between SE and NS, in-keeping with a similar genetic pathogenesis. However, increased expression from 4q22, 5q23.2 and 9p21 distinguished SSE from SE and NS and decreased copy number and expression from 2q36–q37 and 6q24 was a specific feature of NS-derived cell lines. Our analysis also highlights 19 regions with both copy number and expression imbalances in greater than 40% of cases. Mining available expression array data identified genes from these regions as candidates for involvement in TGCT development. Supplementary data is available at http://www.crukdmf.icr.ac.uk/array/array.html

Expression of NES-hTERT in Cancer Cells Delays Cell Cycle Progression and Increases Sensitivity to Genotoxic Stress

Telomerase is a reverse transcriptase associated with cellular immortality through telomere maintenance. This enzyme is activated in 90% of human cancers, and inhibitors of telomerase are currently in clinical trials to counteract tumor growth. Many aspects of telomerase biology have been investigated for therapy, particularly inhibition of the enzyme, but little was done regarding its subcellular shuttling. We have recently shown that mutations in the nuclear export signal of hTERT, the catalytic component of telomerase, led to a mutant (NES-hTERT) that failed to immortalize cells despite nuclear localization and catalytic activity. Expression of NES-hTERT in primary fibroblast resulted in telomere-based premature senescence and mitochondrial dysfunction. Here we show that expression of NES-hTERT in LNCaP, SQ20B and HeLa cells rapidly and significantly decreases their proliferation rate and ability to form colonies in soft agar while not interfering with endogenous telomerase activity. The cancer cells showed increased DNA damage at telomeric and extra-telomeric sites, and became sensitive to ionizing radiation and hydrogen peroxide exposures. Our data show that expression of NES-hTERT efficiently counteracts cancer cell growth in vitro in at least two different ways, and suggest manipulation with the NES of hTERT or its subcellular shuttling as a new strategy for cancer treatment