Early Mechanistic Events Induced by Low Molecular Weight Polycyclic Aromatic Hydrocarbons in Mouse Lung Epithelial Cells: A Role for Eicosanoid Signaling

Low molecular weight polycyclic aromatic hydrocarbons (LMW PAHs; < 206.3 g/mol) are under regulated environmental contaminants (eg, secondhand smoke) that lead to gap junction dysregulation, p38 MAPK activation, and increased mRNA production of inflammatory mediators, such as cytokines and cyclooxygenase (COX2), in lung epithelial cells. However, the early mechanisms involving lipid signaling through the arachidonic acid pathway and subsequent eicosanoid production leading to these downstream events are not known. Common human exposures are to mixtures of LMW PAHs, thus C10 cells (a mouse lung epithelial cell line) were exposed to a representative binary PAH mixture, 1-methylanthracene (1-MeA) and fluoranthene (Flthn), for 30 min-24 h with and without p38 and cytosolic phospholipase A2 (cPLA2) inhibitors. Cytosolic phospholipase A2 inhibition reversed PAH-induced phospho-p38 MAPK activation and gap junction dysregulation at 30 min. A significant biphasic increase in cPLA2 protein was observed at 30 min, 2, and 4 h, as well as COX2 protein at 2 and 8 h. Untargeted metabolomics demonstrated a similar trend with significantly changing metabolites at 30 min and 4 h of exposure relative to 1 h; a "cPLA2-like" subset of metabolites within the biphasic response were predominately phospholipids. Targeted metabolomics showed several eicosanoids (eg, prostaglandin D2 (PGD2), PGE2α) were significantly increased at 4, 8, and 12 h following exposure to the binary PAH mixture and this effect was p38-dependent. Finally, PAH metabolism was not observed until after 8 h. These results indicate an early lipid signaling mechanism of LMW PAH toxicity in lung epithelial cells due to parent PAH compounds.

Abstract P4-07-10: Epithelial-mesenchymal transition sensitizes breast cancer cells to paraptosis-mediated cell death via the fungus-derived sesterpenoid, Ophiobolin A

The epithelial-mesenchymal transition (EMT) enables the dissociation of cancer cells from the primary tumor by facilitating tolerance to lack of cell-adhesion, decreasing cellular division and increasing motility of individual cells, which leads to an invasive phenotype that links EMT to metastasis. Furthermore, EMT results in the acquisition of stem-cell markers and an increased ability to initiate tumor growth, supporting the concept that EMT may contribute to the development of a small, persistent sub-population of the tumor called cancer stem cells (CSCs). Cells that have undergone EMT have characteristically suppressed cell cycles, making them resistant to commonly used chemotherapies that target DNA replication or microtubule dynamics, processes essential to replicating cells. Nonspecific treatments can also rely on inducing apoptotic cell death; however, recent debates challenge the efficacy of apoptosis in solid tumors, citing high rates of acquired resistance. Utilizing a compound that induces alternative cell death, namely paraptosis, becomes attractive when these other treatments fail. Relying on an activated gene expression program, paraptosis results in the swelling of the mitochondria and endoplasmic reticulum and Apaf-1-independent alternative caspase-9 activity. Treating with paraptosis-inducing compounds such as Ophiobolin A (OpA) specifically targets otherwise-insensitive CSC and EMT cells to re-sensitize bulk tumor populations to chemotherapies. We describe EMT as a key driver of enhanced sensitivity to paraptosis-induced cell death following short-term treatment with OpA or other paraptosis-inducing compounds. Further, paraptosis selectively eliminates the CSC sub-population by reducing stem cell activity and highlights the potential of this pathway in breast cancer treatment.

Citation Format: Reisenauer K, Tao Y, Ingros A, Philip T, Evidente A, Kornienko A, Romo D, Taube J. Epithelial-mesenchymal transition sensitizes breast cancer cells to paraptosis-mediated cell death via the fungus-derived sesterpenoid, Ophiobolin A [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-07-10.

Quantitative chemoproteomic profiling reveals multiple target interactions of spongiolactone derivatives in leukemia cells

Identifying the covalent targets of a natural product-derivative in cancer cells.

Editorial: Strategies for cellular target identification of natural products

Daniel Romo and Jun Liu introduce the Natural Product Reports themed issue on ‘Strategies for cellular target identification of natural products’.

Blind colour separation of H&E stained histological images by linearly transforming the colour space

Blind source separation methods aim to split information into the original sources. In histology, each dye component attempts to specifically characterize different microscopic structures. In the case of the hematoxylin-eosin stain, universally used for routine examination, quantitative analysis may often require the inspection of different morphological signatures related mainly to nuclei patterns, but also to stroma distribution. Stain separation is usually a preprocessing operation that is transversal to different applications. This paper presents a novel colour separation method that finds the hematoxylin and eosin clusters by projecting the whole (r,g,b) space to a folded surface connecting the distributions of a series of [(r-b),g] planes that divide the cloud of H&E tones. The proposed method produces density maps closer to those obtained with the colour mixing matrices set by an expert, when comparing with the density maps obtained using nonnegative matrix factorization (NMF), independent component analysis (ICA) and a state-of-the-art method. The method has outperformed three baseline methods, NMF, Macenko and ICA, in about 8%, 12% and 52% for the eosin component, whereas this was about 4%, 8% and 26% for the hematoxylin component.

Improved COBAS TaqMan hepatitis C virus test (Version 2.0) for use with the High Pure system: enhanced genotype inclusivity and performance characteristics in a multisite study

We have evaluated the COBAS TaqMan hepatitis C virus (HCV) test (version 2.0) for use with the High Pure system (HCVHPS V2), a new, revised real-time reverse transcription-PCR assay developed to improve the genotype quantitation of version 1.0 (HCVHPS V1). Revisions were made in the wash buffer and in the reverse transcription temperature. The genotype inclusivity of HCVHPS V2 was evaluated at three different sites, using HCVHPS V2, HCVHPS V1, and the COBAS AMPLICOR HCV MONITOR test (version 2.0) (CAHCM). The fully automated COBAS Ampliprep/COBAS TaqMan HCV test was also used in one of the participating laboratories. The mean differences in HCV RNA values between HCVHPS V2 and CAHCM and between HCVHPS V2 and HCVHPS V1 ranged from -0.21 to 0.13 log and from 0.24 to 1.27 log, respectively, with >0.5-log differences for genotypes 2, 3, 4, and 5. With a NIBSC panel of HCV genotypes 1 through 6, the measured HCVHPS V2 values were within 0.25 log of the nominal values for all 6 genotypes. When serial dilutions of genotype-specific clinical HCV specimens were tested, the assay showed a limit of detection between 10 and 20 IU/ml and a linear range of 25 IU/ml to 3.91 x 10(8) IU/ml. Clinical and analytical specificities of 100% were demonstrated with 100 HCV-seronegative specimens as well as with 12 non-HCV members of Flaviviridae and 22 additional microorganisms. These data indicate that HCVHPS V2 is a robust and accurate test for the quantitation of all six HCV genotypes and useful in monitoring viral load in all clinical HCV specimens.

Enantioselective strategy to the spirocyclic core of Palau'amine and related bisguanidine marine alkaloids

[structure: see text] An enantioselective strategy to the spirocyclic core found in the oroidin-derived family of bisguanidine marine alkaloids has been devised, premised on a biosynthetic proposal. Herein, we describe the successful implementation of this strategy, which entails a Diels-Alder reaction and a chlorination/ring contraction sequence that delivers the fully functionalized spirocyclic core. In this initial report, an intermolecular chlorination delivers a cyclopentane that is epimeric at C17 relative to the palau'amines and epimeric at C11 relative to the axinellamines.

Studies toward gymnodimine: development of a single-pot Hua reaction for the synthesis of highly hindered cyclic imines

[structure: see text]. In studies directed toward gymnodimine and related marine toxins, a single-pot variation of the Hua cyclic imine synthesis has been developed. The reaction involves generation of N-trimethylsilyl lactams in situ followed by alkyllithium addition leading directly to cyclic imines. Importantly, this reaction proceeds efficiently with highly hindered alpha,alpha-dialkyl lactams, provided 1,2-dimethoxyethane (DME) is used as solvent, leading to stable cyclic imines. Overall, this transformation allows a one-pot coupling of an alkyliodide and a lactam to give a cyclic imine.

Studies toward (-)-gymnodimine: concise routes to the spirocyclic and tetrahydrofuran moieties

[formula: see text] (-)-Gymnodimine is a member of a unique class of potent marine toxins possessing imines within a spirocylic array. Herein we report the synthesis of the tetrahydrofuran fragment and a strategy toward the spirocyclic imine fragment of this family of toxins. Key reactions include an asymmetric anti-aldol reaction to set the stereochemistry of the tetrahydrofuran and a formal, intermolecular Diels-Alder reaction involving an alpha-methylene-delta-lactam and a dienyne.

Synthesis and inhibitory action on HMG-CoA synthase of racemic and optically active oxetan-2-ones (beta-lactones)

A homologous series of both C3-unsubstituted and C3-methyl substituted oxetan-2-ones (beta-lactones) was investigated as potential inhibitors of yeast 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) synthase. Several reported methods for racemic beta-lactone synthesis were studied for preparation of the target series. In addition, a novel aluminum-based Lewis acid obtained by combination of Et2AlCl with (1R,2R)-2-[(diphenyl)hydroxymethyl] cyclohexan-1-ol was studied for the asymmetric [2 + 2] cycloaddition of aldehydes and trimethylsilylketene. This Lewis acid exhibited good reactivity but variable enantioselectivity (22-85% ee). In in vitro assays using both native and recombinant HMG-CoA synthase from Saccharomyces cerevisiae, oxetan-2-ones mono-substituted at C4 with linear alkyl chains gave IC50s that decreased monotonically with chain length up to 10 carbons and then rose rapidly for longer chains. The trans isomers of 3-methyl-4-alkyl-oxetan-2-ones showed a similar trend but had 1.3- to 5.6-fold lower IC50s. The results imply a substantial hydrophobic pocket in this enzyme that interacts with both C-3 and C-4 substituents of oxetan-2-one inhibitors.

Effects of Analogs of the Fungal Sexual Pheromone Sirenin on Male Gamete Motility in Allomyces macrogynus

The ability of various structural analogs of the sexual pheromone sirenin to attract male gametes of the aquatic fungus Allomyces macrogynus was determined. Previous studies had shown that several structural analogs and stereoisomers of natural l-sirenin were devoid of activity at physiological concentrations. We now report the discovery of a structural analog that exhibits biological activity indistinguishable from the natural pheromone. The bioassay system used to determine chemotaxis was calibrated using synthetic, racemic sirenin, which exhibited a threshold concentration for gamete attraction at an applied concentration of 10 picomolar. The new synthetic monohydroxy analog of sirenin also had a threshold concentration of 10 picomolar. In the process of developing a new total synthesis of sirenin, a variety of other analogs were prepared and tested. All of these analogs exhibited threshold concentrations at 1 micromolar or higher, although attraction at these higher concentrations still varied according to their structural resemblance to sirenin. Thus, the results of these studies demonstrate that the hydroxymethyl group attached to the six-membered ring of sirenin is not essential for biological activity at physiological concentrations. The studies with other analogs demonstrate that biological activity at any concentration involves a balance between hydrophilic hydroxyl groups and hydrophobic hydrocarbon groups in the structure.