The anti-MRSA compound 3-O-alpha-L-(2″,3″-di-p-coumaroyl)rhamnoside (KCR) inhibits protein synthesis in Staphylococcus aureus.

Methicillin-resistant S aureus (MRSA) contributes to patient mortality and extended hospital stays. 3-O-alpha-L-(2″,3″-di-p-coumaroyl)rhamnoside (KCR) is a natural product antibiotic that is effective against MRSA but has no known mechanism of action (MOA). We used proteomics to identify the MOA for KCR. Methicillin sensitive S aureus and a mixture of four KCR stereoisomers were tested. A time-kill assay was used to choose a 4 h treatment using KCR at 5× its MIC for proteomic analysis. S aureus was treated in triplicate with KCR, oxacillin or vehicle and quantitative proteomic analysis was carried out using isobaric tags and mass spectrometry. 1190 proteins were identified and 552 were affected by KCR (q < 0.01). Ontology analysis identified 6 distinct translation-related categories that were affected by KCR (PIANO, 10% false-discovery rate) including structural constituent of ribosome, translation, rRNA binding, tRNA binding, tRNA processing and aminoacyl-tRNA ligase activity. Median fold changes (KCR vs Control) for small and large ribosomal components were 1.46 and 1.43 respectively. KCR inhibited the production of luciferase protein in an in vitro assay (IC50 39.6 µg/ml). Upregulation of translation-related proteins in response to KCR indicates that KCR acts to disrupt S aureus protein synthesis. This was confirmed with an in vitro transcription/translation assay. SIGNIFICANCE: Methicillin-resistant S aureus (MRSA) contributes to patient mortality and extended hospital stays. 3-O-alpha-L-(2″,3″-di-p-coumaroyl)rhamnoside (KCR) is a natural product antibiotic that is effective against MRSA but has no known mechanism of action (MOA). Using proteomic analysis we determined that KCR acts by inhibiting protein synthesis. KCR is an exciting novel antibiotic and this work represents an important step in its development towards clinical use.

The entirely carbohydrate immunogen Tn-PS A1 induces a cancer cell selective immune response and cytokine IL-17.

The tumor-associated carbohydrate antigen/hapten Thomsen-nouveau (Tn; a-D-GalpNAc-ONH2) was conjugated to a zwitterionic capsular polysaccharide, PS A1, from commensal anaerobe Bacteroides fragilis ATCC 25285/NCTC 9343 for the development of an entirely carbohydrate cancer vaccine construct and probed for immunogenicity. This communication discloses that murine anti-Tn IgG3 antibodies both bind to and recognize human tumor cells that display the Tn hapten. Furthermore, the sera from immunization of mice with Tn-PS A1 contain cytokine interleukin 17 (IL-17A), which is known to possess anti-tumor function and represents a striking difference to an IL-2, and IL-6 profile obtained with anti-PS A1 sera.

Synthesis and Biological Evaluation of Novel N-phenyl-5-carboxamidyl Isoxazoles as Potential Chemotherapeutic Agents for Colon Cancer.

A new series of isoxazole derivatives, N-phenyl-5-carboxamidyl isoxazoles, was investigated for their anticancer activity with solid tumor selectivity. Six N-phenyl-5-carboxamidylisoxazoles were chemically synthesized and evaluated by the in vitro disk-diffusion assay and IC50 cytotoxicity determination. The results showed that one of the derivatives, compound 3,N-(4-chlorophenyl)-5-carboxamidyl isoxazole, was the most active against colon 38 and CT-26 mouse colon tumor cells with an IC50 of 2.5 µg/mL for both cell lines. Western blot analysis showed that compound 3 significantly down-regulated the expression of phosphorylated STAT3 in both human and mouse colon cancer cells indicating that the mechanism of action for compound 3 may involve the inhibition of JAK3/STAT3 signaling pathways. Flow cytometric analysis with Annexin V staining showed that the death induced by compound 3 is mediated through cell necrosis and not apoptotic pathway. In summary, our results show that compound 3 is a new N-phenyl-5-carboxamidyl isoxazole with potential anticancer activity. Compound 3 inhibits the phosphorylation of STAT3, a novel target for chemotherapeutic drugs, and is worthy of further investigation as a potential chemotherapeutic agent for treating colon cancer.

SPARC affects glioma cell growth differently when grown on brain ECM proteins in vitro under standard versus reduced-serum stress conditions.

Secreted protein acidic and rich in cysteine (SPARC) has a suppressive effect on U87 glioma cell proliferation when assessed in vitro and in vivo using parental U87T2 and U87T2-derived SPARC-transfected clones. Since SPARCinteracts with extracellular matrix (ECM) proteins, we examined the effect of SPARC secretion on proliferation, morphology, and cell density of glioma cells grown in vitro, in the absence and presence of ECM proteins under standard (10% fetal bovine serum [FBSI) and reduced (0.1% FBS) serum stress conditions. Under standard conditions, MTT (3-(4,5-cimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide) growth curves, morphology, and Western blot analyses demonstrated that SPARC had a suppressive and biphasic effect on growth that was not grossly modulated by the ECMs. The SPARC-induced changes in morphology observed at 24 h were not altered by the presence of ECMs. Under reduced-serum stress conditions, Western blot, morphological, and flow cytometric analyses indicated that the SPARC-induced suppressive growth effects were eliminated when the cells were grown on plastic. However, ECM-specific changes in growth were observed, some of which correlated with secreted SPARC levels. These results indicate that the differential effects of SPARC and ECMs on proliferation are dependent on culture conditions. Since the results obtained under standard conditions agree with our in vivo observations, we conclude that the ability of SPARC to suppress proliferation is regulated to a greater degree by the level of SPARC and that this suppressive effect is not influenced by the presence of any of the ECMs examined.

Structures and cytotoxic properties of sponge-derived bisannulated acridines.

A reinvestigation of sponge natural products from additional Indo-Pacific collections of Xestospongiacf. carbonaria and X. cf. exigua has provided further insights on the structures, biological activities, and biosynthetic origin of bisannulated acridines. These alkaloids include one known pyridoacridine, neoamphimedine (2), and three new analogues, 5-methoxyneoamphimedine (4), neoamphimedine Y (5), and neoamphimedine Z (6). A completely new acridine, alpkinidine (7), was also isolated. A disk diffusion soft agar assay, using a panel of five cancer cell lines (solid tumors and leukemias) and two normal cells, was used to evaluate the differential cytotoxicity (solid tumor selectivity) of the sponge semipure extracts and selected compounds including amphimedine (1), 2, 4, and 7. While all four compounds were solid tumor selective, 1 and 2 were the most potent and 4 was the most selective. The rationale used to characterize the new structures is outlined along with the related biosynthetic pathways envisioned to generate 2 and 7.