Cancer-Specific Synthetic Lethality between ATR and CHK1 Kinase Activities.

ATR and CHK1 maintain cancer cell survival under replication stress and inhibitors of both kinases are currently undergoing clinical trials. As ATR activity is increased after CHK1 inhibition, we hypothesized that this may indicate an increased reliance on ATR for survival. Indeed, we observe that replication stress induced by the CHK1 inhibitor AZD7762 results in replication catastrophe and apoptosis, when combined with the ATR inhibitor VE-821 specifically in cancer cells.

Structure of human Bloom's syndrome helicase in complex with ADP and duplex DNA.

Bloom's syndrome is an autosomal recessive genome-instability disorder associated with a predisposition to cancer, premature aging and developmental abnormalities. It is caused by mutations that inactivate the DNA helicase activity of the BLM protein or nullify protein expression. The BLM helicase has been implicated in the alternative lengthening of telomeres (ALT) pathway, which is essential for the limitless replication of some cancer cells.

Kinetic and mechanistic characterisation of Choline Kinase-α.

Choline Kinase is a key component of the Kennedy pathway that converts choline into a number of structural and signalling lipids that are essential for cell growth and survival. One member of the family, Choline Kinase-α (ChoKα) is frequently up-regulated in human cancers, and expression of ChoKα is sufficient to transform cells. Consequently ChoKα has been studied as a potential target for therapeutic agents in cancer research.

Crystal structure of the Pseudomonas aeruginosa MurG: UDP-GlcNAc substrate complex.

MurG is an essential bacterial glycosyltransferase enzyme in Pseudomonas aeruginosa performing one of the key membrane steps of peptidoglycan synthesis catalyzing the transfer of N-acetyl glucosamine (GlcNAc) from its donor substrate, UDP-GlcNAc, to the acceptor substrate Lipid I. We have solved the crystal structure of the complex between Pseudomonas aeruginosa MurG and UDP-GlcNAc and compared it with the previously solved complex from E. coli.

The novel ATR inhibitor VE-821 increases sensitivity of pancreatic cancer cells to radiation and chemotherapy.

DNA damaging agents such as radiotherapy and gemcitabine are frequently used for the treatment of pancreatic cancer. However, these treatments typically provide only modest benefit. Improving the low survival rate for pancreatic cancer patients therefore remains a major challenge in oncology.

Selective killing of ATM- or p53-deficient cancer cells through inhibition of ATR.

Here we report a comprehensive biological characterization of a potent and selective small-molecule inhibitor of the DNA damage response (DDR) kinase ATR. We show a profound synthetic lethal interaction between ATR and the ATM-p53 tumor suppressor pathway in cells treated with DNA-damaging agents and establish ATR inhibition as a way to transform the outcome for patients with cancer treated with ionizing radiation or genotoxic drugs.

Mode of action of the novel phenazine anticancer agents XR11576 and XR5944.

The substituted phenazines XR11576 and XR5944 were originally described as dual topoisomerase-I/II poisons. Subsequent reports, however, indicated that the association of their cytotoxicity with cellular topoisomerases was not clear. We set out to study this further using human tumour cell lines, PEO1 ovarian cancer, MDA-MB-231 breast cancer and variants with acquired resistance to VP-16 and XR11576: PEO1VPR, MB-231VPR, MB-231-11576R and camptothecin: PEO1CamR.

Phenazine-1-carboxamides: structure-cytotoxicity relationships for 9-substituents and changes in the H-bonding pattern of the cationic side chain.

A series of phenazine-1-carboxamides were prepared, including variations in both chromophore substituents and the nature of the cationic side chain. The novel side-chain analogues were prepared from the corresponding phenazine-1-carboxylic acids via Schmidt conversion to the 1-amines and from the corresponding 1-halides. Structure-cytotoxicity relationships for these compounds in a panel of tumor cell lines showed that there is very limited scope for variation of the structure of the 1-carboxamide side chain, consistent with the recent structural model of how tricyclic carboxamides bind to DNA.

Preclinical anti-tumor activity of XR5944 in combination with carboplatin or doxorubicin in non-small-cell lung carcinoma.

XR5944 (MLN944) is a novel bis-phenazine currently in phase I clinical trials that has demonstrated potent cytotoxic activity against a variety of tumor models. The combinations of XR5944 with carboplatin or doxorubicin were investigated in COR-L23/P human non-small-cell lung carcinoma (NSCLC) cells in vitro and the corresponding xenografts in vivo. In vitro cytotoxicity was evaluated by the sulforhodamine B assay and the drug interactions following simultaneous or sequential exposure were determined using median-effect analysis to calculate combination indices (CIs).

The ex vivo characterization of XR5944 (MLN944) against a panel of human clinical tumor samples.

XR5944 (MLN944) is a novel DNA targeting agent with potent antitumor activity, both in vitro and in vivo, against several murine and human tumor models. We have used an ATP-tumor chemosensitivity assay to assess the ex vivo sensitivity of a variety of solid tumors (n = 90) and a CCRF-CEM leukemia cell line selected with XR5944. Differences in gene expression between the parental CCRF-CEM and the resistant subline were investigated by quantitative reverse transcription-PCR.

Ex vivo reversal of chemoresistance by tariquidar (XR9576).

The expression of P-glycoprotein (P-gp) has been demonstrated to confer resistance to several anticancer drugs, including anthracyclines, taxanes and vinca alkaloids. Tariquidar is a novel inhibitor of P-gp that has been shown to reverse resistance to cytotoxic drugs in tumor cell lines and mouse xenografts. We have used an ATP-based chemosensitivity assay (ATP-TCA) to compare the activity of cytotoxic drugs in combination with tariquidar against a variety of solid tumors (n = 37).

Ex vivo characterization of XR11576 (MLN576) against ovarian cancer and other solid tumors.

XR11576 (MLN576) is a novel monophenazine with a mechanism of action that includes interaction with both topoisomerase (Topo) I and II. The aim of this study was to evaluate its cytotoxicity against fresh tumor cells taken from patients with a variety of solid tumors. Cells were obtained from 89 patients and exposed for 6 days to XR11576 alone, or in combination with doxorubicin, cisplatin, treosulfan, paclitaxel or vinorelbine.

XR5967, a novel modulator of plasminogen activator inhibitor-1 activity, suppresses tumor cell invasion and angiogenesis in vitro.

Recent reports suggest that elevated levels of plasminogen activator inhibitor (PAI)-1 may contribute to tumor progression. We have recently shown that antibodies to PAI-1 block the invasive and migratory potential of human fibrosarcoma cells and suppress angiogenesis in vitro. Here we report the in vitro evaluation of a low-molecular-weight modulator of PAI-1, XR5967, on invasion, migration and angiogenesis.

In vitro and in vivo characterization of XR11576, a novel, orally active, dual inhibitor of topoisomerase I and II.

XR11576, a novel phenazine, was developed as an inhibitor of both topoisomerase I and II. This study characterized the ability of XR11576 to inhibit both enzymes, and determined its in vitro and in vivo antitumor efficacy against a number of murine and human tumor models. XR11576 was a potent inhibitor of purified topoisomerase I and IIalpha, and exhibited similar potency for both enzymes.

Structure-activity relationships for pyrido-, imidazo-, pyrazolo-, pyrazino-, and pyrrolophenazinecarboxamides as topoisomerase-targeted anticancer agents.

Heterocyclic phenazinecarboxamides were prepared by condensation of aminoheterocycles and 2-halo-3-nitrobenzoic acids, followed by reductive ring closure and amidation. They showed similar inhibition of paired cell lines that underexpressed topo II or overexpressed P-glycoprotein, indicating a non topo II mechanism of cytotoxicity and indifference to P-glycoprotein mediated multidrug resistance. Compounds with a fused five-membered heterocyclic ring were generally less potent than the pyrido[4,3-a]phenazines.

Novel angular benzophenazines: dual topoisomerase I and topoisomerase II inhibitors as potential anticancer agents.

A series of substituted angular benzophenazines were prepared using a new synthetic route via a novel regiocontrolled condensation of 1,2-naphthoquinones and 2,3-diaminobenzoic acids. The synthesis and biological activity of this new series of substituted 8,9-benzo[a]phenazine carboxamide systems are described. The analogues were evaluated against the H69 parental human small cell lung carcinoma cell line and H69/LX4 resistant cell line which overexpresses P-glycoprotein.