Target Identification of the Marine Natural Products Dictyoceratin-A and -C as Selective Growth Inhibitors in Cancer Cells Adapted to Hypoxic Environments.

Hypoxia-adapted cancer cells in tumors contribute to the pathological progression of cancer. The marine spongean sesquiterpene phenols dictyoceratin-A (1) and -C (2) have been shown to induce hypoxia-selective growth inhibition in cultured cancer cells and exhibit in vivo antitumor effects. These compounds inhibit the accumulation of hypoxia-inducible factor-1α (HIF-1α), which is a drug target in hypoxia-adapted cancer cells, under hypoxic conditions. However, the target molecules of compounds 1 and 2, which are responsible for decreasing HIF-1α expression under hypoxic conditions, remain unclear. In this study, we synthesized probe molecules for compounds 1 and 2 to identify their target molecules and found that both compounds bind to RNA polymerase II-associated protein 3 (RPAP3), which is a component of the R2TP/Prefoldin-like (PEDL) complex. In addition, RPAP3-knockdown cells showed a phenotype similar to that of compound-treated cells.

Structure-Activity Relationship and in Vivo Anti-Tumor Evaluations of Dictyoceratin-A and -C, Hypoxia-Selective Growth Inhibitors from Marine Sponge.

Oral dictyoceratin-C (1) and A (2), hypoxia-selective growth inhibitors, showed potent in vivo antitumor effects in mice subcutaneously inoculated with sarcoma S180 cells. Structurally modified analogs were synthesized to assess the structure-activity relationship of the natural compounds 1 and 2 isolated from a marine sponge. Biological evaluation of these analogs showed that the exo-olefin and hydroxyl and methyl ester moieties were important for the hypoxia-selective growth inhibitory activities of 1 and 2. Thus far, only substitution of the methyl ester with propargyl amide in 1 was found to be effective for the synthesis of probe molecules for target identification.

Enantioselective synthesis of dictyoceratin-A (smenospondiol) and -C, hypoxia-selective growth inhibitors from marine sponge.

Total syntheses of (+)-dictyoceratin-C (1) and (+)-dictyoceratin-A (smenospondiol) (2), hypoxia-selective growth inhibitors isolated from marine sponge, were executed. The absolute stereochemistry of the each compound was determined through the enantioselective total syntheses of them. It revealed that the unnatural enantiomers of them also exhibited the hypoxia-selective growth inhibitory activity against human prostate cancer DU-145 cells.

Xylarianaphthol-1, a novel dinaphthofuran derivative, activates p21 promoter in a p53-independent manner.

Xylarianaphthol-1, a novel dinaphthofuran derivative, was isolated from a marine sponge-derived fungus of order Xylariales on the guidance of a bioassay using the transfected human osteosarcoma MG63 cells (MG63(luc+)). The chemical structure of xylarianaphthol-1 was determined from the (1)H and (13)C NMR analysis and was further confirmed by the total synthesis. Xylarianaphthol-1 activated p21 promoter stably transfected in MG63 cells dose-dependently. Expression of p21 protein in the wild-type MG63 cells was also increased by xylarianaphthol-1 treatment.

A multielement masking method using magnesium hydroxide coprecipitation for the selective determination of lead in water samples by differential pulse anodic stripping voltammetry.

We present a new multielement masking method using magnesium hydroxide coprecipitation for the selective determination of Pb by differential pulse anodic stripping voltammetry (DPASV). The recovery of Pb in the masking method was over 95%, while interfering ions (Cd(2+), Co(2+), Cu(2+), Fe(3+), Mn(2+), and Ni(2+)) could be removed at 100% from the analytical sample. A linear regression was obtained in the Pb concentration from 10 to 1000 microg kg(-1) in the existence of 100 microg kg(-1) of the interfering ions. When this method was applied to the determination of Pb in a natural water-standard reference material (NIST 1640), the determined value for Pb in this work (25.4 +/- 4.1 microg kg(-1)) almost agreed with the certified value (27.89 +/- 0.14 microg kg(-1)).