Mutations within the catalytic domain of the histone methyltransferase EZH2 have been identified in subsets of patients with non-Hodgkin lymphoma (NHL). These genetic alterations are hypothesized to confer an oncogenic dependency on EZH2 enzymatic activity in these cancers. We have previously reported the discovery of EPZ005678 and EPZ-6438, potent and selective S-adenosyl-methionine-competitive small molecule inhibitors of EZH2. Although both compounds are similar with respect to their mechanism of action and selectivity, EPZ-6438 possesses superior potency and drug-like properties, including good oral bioavailability in animals. Here, we characterize the activity of EPZ-6438 in preclinical models of NHL. EPZ-6438 selectively inhibits intracellular lysine 27 of histone H3 (H3K27) methylation in a concentration-and time-dependent manner in both EZH2 wild-type and mutant lymphoma cells. Inhibition of H3K27 trimethylation (H3K27Me3) leads to selective cell killing of human lymphoma cell lines bearing EZH2 catalytic domain point mutations. Treatment of EZH2-mutant NHL xenograft-bearing mice with EPZ-6438 causes dose-dependent tumor growth inhibition, including complete and sustained tumor regressions with correlative diminution of H3K27Me3 levels in tumors and selected normal tissues. Mice dosed orally with EPZ-6438 for 28 days remained tumor free for up to 63 days after stopping compound treatment in two EZH2-mutant xenograft models. These data confirm the dependency of EZH2-mutant NHL on EZH2 activity and portend the utility of EPZ-6438 as a potential treatment for these genetically defined cancers. Mol Cancer Ther; 13(4); 842-54. Ó2014 AACR.

Daylight-driven antimicrobial nanomaterials serve as a novel barrier for transmission of emerging infectious diseases.

We develop a random walk model to simulate the Brownian motion and the electrochemical response of a single molecule confined to an electrode surface via a flexible molecular tether. We use our simple model, which requires no prior knowledge of the physics of the molecular tether, to predict and better understand the voltammetric response of surface-confined redox molecules when motion of the redox molecule becomes important. The single molecule is confined to a hemispherical volume with a maximum radius determined by the flexible molecular tether (5-20 nm) and is allowed to undergo true three-dimensional diffusion. Distance- and potential-dependent electron transfer probabilities are evaluated throughout the simulations to generate cyclic voltammograms of the model system. We find that at sufficiently slow cyclic voltammetric scan rates the electrochemical reaction behaves like an adsorbed redox molecule with no mass transfer limitation; thus, the peak current is proportional to the scan rate. Conversely, at faster scan rates the diffusional motion of the molecule limits the simulated peak current, which exhibits a linear dependence on the square root of the scan rate. The switch between these two limiting regimes occurs when the diffusion layer thickness, (2Dt)(1/2), is ~10 times the tether length. Finally, we find that our model predicts the voltammetric behavior of a redox-active methylene blue tethered to an electrode surface via short flexible single-stranded, polythymine DNAs, allowing the estimation of diffusion coefficients for the end-tethered molecule.

XK469 (NSC 697887) is a synthetic quinoxaline phenoxypropionic acid derivative that possesses unusual solid tumor selectivity and activity against multidrug-resistant cancer cells. We report here that XK469 and its S(؊) and R(؉)-isomers induce reversible protein-DNA crosslinks in mammalian cells. Under protein denaturing conditions, the protein-DNA crosslinks are rendered irreversible and stable to DNA banding by CsCl gradient ultracentrifugation. Several lines of evidence indicate that the primary target of XK469 is topoisomerase II␤. Preferential targeting of topoisomerase II␤ may explain the solid tumor selectivity of XK469 and its analogs because solid tumors, unlike leukemias, often have large populations of cells in the G1͞G0 phases of the cell cycle in which topoisomerase II␤ is high whereas topoisomerase II␣, the primary target of many leukemia selective drugs, is low. X K469 (NSC 697887, Fig. 1) is an analog of the herbicide Assure (DuPont) that was discovered in a screen for solid tumor-selective agents (1-3). The screen is based on an agar diffusion assay in which an agent's relative toxicity for leukemias and solid tumors is determined by comparison of zones of colony inhibition (3, 4). A zone difference of 250 units represents approximately an 8-fold difference in sensitivity, and XK469 gave a leukemia͞solid tumor zone difference of 510 (1). XK469 has broad activity against murine solid tumors such as colon 38, pancreatic 03, and mammary 16͞C (1). The R(ϩ)-and S(Ϫ)-isomers of XK469 (respectively, NSC 698215 and NSC 698216) were found to be equally toxic in studies with animal tumor models (1). XK469 also was found to be highly active against multidrug-resistant tumors (1, 2). The dose-limiting toxicities for XK469 and its analogs were marrow toxicity and epithelial damage in the gastrointestinal tract. XK469 has low toxicity in comparison to other anticancer agents, such as camptothecin. For instance, the average in vitro GI 50 (50% growth inhibitory concentration) for the NCI 60 tumor cell line panel is 7 ϫ 10 Ϫ5 M for XK469 and 4.5 ϫ 10 Ϫ8 for camptothecin, a 1,500ϫ difference (National Cancer Institute Developmental Therapeutics Compare web site, http:͞͞dtp.nci.gov). The R-and S-isomers of XK469 were well tolerated by tumor-bearing mice at an effective therapeutic dose of 74.4 mg͞kg, followed by several lower doses of 47 mg͞kg͞injection (1). Thus, relatively high levels of XK469 have been tolerated in animal model studies. Extensive pharmacokinetic studies of the S-isomer of XK469 in CD1F2 mice were performed at 100 mg͞kg (Ϸ1͞6 maximum tolerated total dose) as a single i.v. bolus dose. In these studies, up to 0.48 mg͞ml (Ϸ1.4 mM) maximum serum concentrations of XK469 were produced (K.K.C., unpublished data). Thus, millimolar in vivo concentrations can be produced at nontoxic doses in rodents. The most active analogs, such as XK469, have a halogen at the 7 position (1). The carboxylic acid forms are water soluble and can be injected. Exposure of human colon carcinoma cells to XK469 for 24 hr resul...