In Vitro and in Vivo antitumor activity and the mechanism of siphonodictyal B in human colon cancer cells.

Liphagal, isolated from the marine sponge Aka coralliphaga, exhibits phosphatidylinositol 3-kinase alpha (PI3Kα) inhibitory activity and cytotoxic effects in human cancer cells. Siphonodictyal B, the biogenetic precursor of liphagal, also has PI3K inhibitory activity. However, its cytotoxic or antitumor activities have not been evaluated. In this study, we demonstrated that siphonodictyal B inhibits several kinases such as CDK4/6, CDK7, and PIM2 in addition to PI3K in vitro and that siphonodictyal B exhibits more potent cytotoxic effects than liphagal against human colon cancer cell lines. Furthermore, treatment with siphonodictyal B resulted in increased PARP cleavage, a larger sub-G1 fraction, and a larger annexin V-positive cell population, all of which are indicative of apoptosis induction. As a mechanism of apoptosis induction, we found that siphonodictyal B activates the p38 MAPK pathway, leading the upregulation of proapoptotic factors. Moreover, siphonodictyal B increased ROS levels, thus promoting p38 MAPK pathway activation. NAC, an ROS scavenger, almost completely reversed both the cytotoxic and p38 MAPK pathway-activating effects of siphonodictyal B. These results indicate that the p38 MAPK pathway might be involved downstream of ROS signaling as part of the mechanism of siphonodictyal B-induced apoptosis. Finally, siphonodictyal B displayed antitumor effects in a human colon cancer xenograft mouse model and increased p38 phosphorylation in tumor tissue. These results suggest that siphonodictyal B could serve as the basis of a novel anticancer drug.

A novel approach to oxazole-containing diterpenoid synthesis from plant roots: salviamines E and F.

In this study, salviamines E and F, which are structurally unique abietane-type diterpene alkaloids containing an oxazole ring, were efficiently synthesized from a known molecule, 5,7,8-trimethoxy-1-naphthol. The synthetic sequence involves the following crucial steps: (i) the assembly of a carbon skeleton by coupling a six-carbon homoprenyl unit with a naphthalene moiety (Kumada-Tamao-Corriu coupling); (ii) the construction of a tricyclic phenanthrene ring by acid-induced cyclization of a naphthalene derivative with a homoprenyl side chain; (iii) the formation of an oxazole ring by nucleophilic ring closure of a 2-aminophenylene-1,4-diyl-diformate or -diacetate moiety and (iv) Friedel-Crafts acetylation at the C13 position of the tetracyclic intermediates to obtain the two target molecules, salviamines E and F. To the best of our knowledge, salviamine synthesis is reported here for the first time.

A novel approach to sesquiterpenoid benzoxazole synthesis from marine sponges: nakijinols A, B and E-G.

Nakijinols A, B and analogues E through G, which are structurally unique and biologically significant sesquiterpenoid benzoxazoles, can be efficiently obtained in a highly unified manner from the sesquiterpenoid quinone, smenospongine. The starting material is accessible from the (+)-5-methyl Wieland-Miescher ketone. The synthetic method features strategic construction of the requisite dihydroxylated benzoxazole substructure via the ring closure of the N-(2-hydroxyphenyl)-formamide or -acetamide moiety. The synthesis of nakijinols is reported here for the first time. The absolute configurations of nakijinols A and E were also established.

Antitumor activity and pharmacologic characterization of the depsipeptide analog as a novel histone deacetylase/ phosphatidylinositol 3-kinase dual inhibitor.

Histone deacetylase (HDAC)/phosphatidylinositol 3-kinase (PI3K) dual inhibition is a promising strategy for the treatment of intractable cancers because of the advantages of overcoming potential resistance and showing synergistic effects. Therefore, development of an HDAC/PI3K dual inhibitor is reasonably attractive. Romidepsin (FK228, depsipeptide) is a potent HDAC inhibitor. We previously reported that depsipeptide and its analogs have an additional activity as PI3K inhibitors and are defined as HDAC/PI3K dual inhibitors. Subsequently, we identified FK-A11 as the most potent analog and reported its biochemical, biological, and structural properties as an HDAC/PI3K dual inhibitor. In this study, we reveal the in vitro and in vivo efficacy of FK-A11 in HT1080 fibrosarcoma and PC3 prostate cancer cell xenograft mouse models. FK-A11 showed in vivo antitumor activity by both i.v. and i.p. administration in a dose-dependent manner. In both xenograft models, FK-A11 showed superior antitumor effects compared to other depsipeptide analogs in accordance with in vitro anti-cell proliferation effects and the potency of HDAC/PI3K dual inhibition. In addition, we showed evidence of HDAC/PI3K dual inhibition accompanying antitumor efficacy in xenograft tumor tissues by immunohistochemistry. We also detailed pharmacokinetic characterization of FK-A11 in mice. These findings will be essential for guiding further preclinical and clinical studies.

Total Synthesis of Thailandepsin B, a Potent HDAC Inhibitor Isolated from a Microorganism.

Thailandepsin B, a bicyclic depsipeptide histone deacetylase inhibitor, was efficiently synthesized in 51% overall yield in eight steps, starting from commercially available D-norleucine methyl ester and known (S,E)-3-(4-methoxybenzyloxy)-7-(tritylthio)hept-4-enoic acid. The method features a convergent approach in which the corresponding seco-acid, a key precursor in macrolactonization, is directly assembled through the condensation of a D-allo-isoleucine-D-cysteine-containing segment with a D-norleucine-containing segment.

Synthesis and biological evaluation of novel FK228 analogues as potential isoform selective HDAC inhibitors.

Novel C4- and C7-modified FK228 analogues were efficiently synthesized in a highly convergent and unified manner. This synthesis features the amide condensation of glycine-d-cysteine-containing segments with d-valine-containing segments for the direct assembly of the corresponding seco-acids, which are key precursors of macrolactones. The HDAC inhibition assay and cell-growth inhibition analysis of the synthesized analogues revealed novel aspects of their structure-activity relationship. This study demonstrated that simple modification at the C4 and C7 side chains in FK228 is effective for improving both HDAC inhibitory activity and isoform selectivity; moreover, potent and highly isoform-selective class I HDAC1 inhibitors were identified.

Low-dose spiruchostatin-B, a potent histone deacetylase inhibitor enhances radiation-induced apoptosis in human lymphoma U937 cells via modulation of redox signaling.

Spiruchostatin B (SP-B), is a potent histone deacetylase (HDAC) inhibitor, in addition to HDAC inhibition, the pharmacological effects of SP-B are also attributed to its ability to produce intracellular reactive oxygen species (ROS), particularly H2O2. In this study, we investigated the effects of low dose (non-toxic) SP-B on radiation-induced apoptosis in human lymphoma U937 cells in vitro. The treatment of cells with low-dose SP-B induced the acetylation of histones, however, does not induce apoptosis. Whereas, the combined treatment with SP-B and radiation significantly enhanced the radiation-induced apoptosis, suggesting the potential role of this combined treatment for future radiation therapy. Interestingly, the enhancement of apoptosis was accompanied by significant increased in the ROS generation. Pre-treatment with an antioxidant, N-acetyl-l-cysteine (NAC) significantly inhibited the enhancement of apoptosis induced by combined treatment, indicating that ROS play an essential role. It was also found that SP-B combined with radiation caused the activation of death receptor and intrinsic apoptotic pathways, via modulation of ROS-mediated signaling. Moreover, SP-B also significantly enhanced the radiation-induced apoptosis in other lymphoma cell lines such as Molt-4 and HL-60. Taken together, our findings suggest that the low-dose SP-B enhances radiation-induced apoptosis via modulation of redox signaling because of its ability to serve as an intracellular ROS generating agent, mainly (H2O2 or [Formula: see text]). This study provides further insights into the mechanism of action of SP-B with radiation and demonstrates that SP-B can be used as a future novel sensitizer for radiation therapy.

Clinical effect of biapenem on nursing and healthcare-associated pneumonia (NHCAP).

The clinical effect of Biapenem (BIPM) on Nursing and Healthcare-associated pneumonia (NHCAP) was evaluated. One hundred and three NHCAP patients (Group B: 52 patients, Group C: 51 patients) to whom BIPM was administered were included in this study. Clinical effect, bacteriological effect, and adverse events were examined. Results revealed efficacy in 45 of 52 patients (efficacy rate: 86.5%) of NHCAP Group B, and 43 of 51 patients (efficacy rate: 84.3%) of NHCAP Group C, 88 of 103 patients (efficacy rate: 85.4%) as a whole. As for bacteriological effect, 10 (76.9%) of 13 Pseudomonas aeruginosa strains, 9 (90.0%) of 10 Klebsiella pneumoniae strains, 7 (87.5%) of 8 methicillin-sensitive Staphlococcus aureus strains, and 7 (100%) of 7 Streptococcus pneumonia strains were eradicated. As a whole, 38 (80.9%) of 47 strains were eradicated. Adverse events included drug fever and drug eruption in one patient each, and abnormal laboratory findings, including mild hepatic dysfunction in 18 patients and mild renal dysfunction in 5 patients. Based on the above, it was concluded that BIPM shows excellent clinical effect on NHCAP with fewer adverse events.

Biochemical, biological and structural properties of romidepsin (FK228) and its analogs as novel HDAC/PI3K dual inhibitors.

Romidepsin (FK228, depsipeptide) is a potent histone deacetylase (HDAC) inhibitor that has FDA approval for the treatment of cutaneous and peripheral T-cell lymphomas. We have previously reported that FK228 and its analogs have an additional activity as phosphatidylinositol 3-kinase (PI3K) inhibitors, and are defined as HDAC/PI3K dual inhibitors. Because a combination of an HDAC inhibitor and a PI3K inhibitor induces apoptosis in human cancer cells in a synergistic manner, development of an HDAC/PI3K dual inhibitor will provide an attractive novel drug for cancer therapy. Using structure-based optimization of the analogs, FK-A11 was identified as the most potent analog. FK-A11 inhibited phosphorylation of AKT and accelerated histone acetylation at lower concentrations, resulting in stronger cytotoxic effects than FK228 and the other analogs in human cancer cells. In this study, we have characterized the biochemical, biological and structural properties of FK228 analogs as PI3K inhibitors. First, FK-A11 is an ATP competitive PI3K inhibitor. Second, FK-A11 is a pan-p110 isoform inhibitor. Third, FK-A11 selectively inhibits PI3K among 22 common cellular kinases. Fourth, conformational changes of FK228 analogs by reduction of an internal disulfide bond have no effect on PI3K inhibitory activity, unlike HDAC inhibitory activity. Finally, molecular modeling of PI3K-FK228 analogs and analyses of the binding affinities identified the structure that defines potency for PI3K inhibitory activity. These results prove our concept that a series of FK228 analogs are HDAC/PI3K dual inhibitors. These findings should help in the development of FK228 analogs as novel HDAC/PI3K dual inhibitors.

Predicting the structures of complexes between phosphoinositide 3-kinase (PI3K) and romidepsin-related compounds for the drug design of PI3K/histone deacetylase dual inhibitors using computational docking and the ligand-based drug design approach.

Predictions of the three-dimensional (3D) structures of the complexes between phosphoinositide 3-kinase (PI3K) and two inhibitors were conducted using computational docking and the ligand-based drug design approach. The obtained structures were refined by structural optimizations and molecular dynamics (MD) simulations. The ligands were located deep inside the ligand binding pocket of the p110α subunit of PI3K, and the hydrogen bond formations and hydrophobic effects of the surrounding amino acids were predicted. Although rough structures were obtained for the PI3K-inhibitor complexes before the MD simulations, the refinement of the structures by these simulations clarified the hydrogen bonding patterns of the complexes.

Spiruchostatin A and B, novel histone deacetylase inhibitors, induce apoptosis through reactive oxygen species-mitochondria pathway in human lymphoma U937 cells.

Spiruchostatin A (SP-A) and spiruchostatin B (SP-B) are the potent histone deacetylase inhibitors (HDACi), that has the potential for chemotherapy of leukemia but the exact mechanism of these compounds remains unclear. In the present study, the role of reactive oxygen species (ROS) production and the mechanism involved in the apoptosis was investigated in human lymphoma U937 cell. When the U937 cells were treated with SP-A and SP-B for 24h at different concentrations, evidence of apoptotic features, including increase in DNA fragmentation and changes in nuclear morphology, were obtained. SP-B showed maximum potency to induce apoptosis, while SP-A was less potent. Apoptosis was also determined by increase in the fraction of sub-G1 cells and Annexin V-FITC staining cells. SP-A and SP-B induced apoptosis was accompanied by significant increase in the formation of intracellular reactive oxygen species (ROS). Pre-treatment with N-acetyl-l-cysteine (NAC), significantly inhibited the SP-A and SP-B mediated apoptosis, suggesting a vital role of ROS involved in the lethality of both agents. Moreover, SP-A and SP-B treatment resulted in the loss of mitochondrial membrane potential (MMP), and Fas, caspase-8 and caspase-3 activation. In addition Bid activation and the release of cytochrome-c to the cytosol was also observed. In this study, we suggest that a marked induction of intracellular ROS mediated mitochondrial pathway and the Fas plays a role in the SP-A and SP-B induced apoptosis. Taken together, our data provides further insights of the mechanism of action of SP-A and SP-B and their potential application as novel chemotherapeutic agents.

Total synthesis of burkholdacs A and B and 5,6,20-tri-epi-burkholdac A: HDAC inhibition and antiproliferative activity.

The bicyclic depsipeptide histone deacetylase (HDAC) inhibitors burkholdacs A and B were efficiently synthesized in a highly convergent and unified manner. The synthesis features the amide coupling of a D-valine-D-cysteine- or D-allo-isoleucine-D-cysteine-containing segment with a D-methionine-containing segment to directly assemble the corresponding seco-acids, key precursors for macrolactonization. Using the same methodology, 5,6,20-tri-epi-burkholdac A was also synthesized. HDAC inhibitory assays and cell-growth inhibition analyses of the synthesized depsipeptides demonstrated the potency order of this class of bicyclic depsipeptides as compared to the clinically approved depsipeptide FK228 (romidepsin). Novel structure-activity relationships within this class of compounds were also revealed.

Enantioselective total synthesis of dysidavarone A, a novel sesquiterpenoid quinone from the marine sponge Dysidea avara.

Dysidavarone A, a structurally unprecedented sesquiterpenoid quinone, was synthesized in 30 % overall yield in a longest liner sequence of 13 steps from commercially available o-vanillin. A highly strained and bridged eight-membered carbocyclic core was established by the C7-C21 carbon bond formation through a copper enolate mediated Michael addition to the internal quinone ring.

Enantioselective total synthesis of otteliones A and B, novel and powerful antitumor agents from the freshwater plant Ottelia alismoides.

Otteliones A and B, isolated from the freshwater plant Ottelia alismoides, have attracted significant attention because of their potential as novel anticancer agents. In this review, four independent enantioselective total syntheses and one formal synthesis of these natural products are presented with particular focus on their methodology and strategy.

Total synthesis of bicyclic depsipeptides spiruchostatins C and D and investigation of their histone deacetylase inhibitory and antiproliferative activities.

The bicyclic depsipeptide histone deacetylase (HDAC) inhibitors spiruchostatins C and D were synthesized for the first time in a highly convergent and unified manner. The method features the amide coupling of a D-leucine-D-cysteine- or D-valine-D-cysteine-containing segment with a D-alanine- or D-valine-containing segment to directly assemble the corresponding seco-acids, key precursors of macrolactonization. The HDAC inhibitory assay and cell-growth inhibition analysis of the synthesized depsipeptides determined the order of potency of spiruchostatins A-D in comparison with the clinically approved depsipeptide FK228 (romidepsin). Novel aspects of structure-activity relationships (SAR) were revealed.

Romidepsin (FK228) and its analogs directly inhibit phosphatidylinositol 3-kinase activity and potently induce apoptosis as histone deacetylase/phosphatidylinositol 3-kinase dual inhibitors.

Activation of phosphatidylinositol 3-kinase (PI3K) signaling is involved in carcinogenesis and cancer progression. The PI3K inhibitors are considered candidate drugs for cancer treatment. Here, we describe a drug screening system for novel PI3K inhibitors using Saccharomyces cerevisiae strains with deleterious mutations in the ATP-binding cassette transporter genes, because wild-type S. cerevisiae uses drug efflux pumps for reducing intracellular drug concentrations. By screening the chemical library of the Screening Committee of Anticancer Drugs, we identified the histone deacetylase (HDAC) inhibitor romidepsin (FK228) and its novel analogs. In vitro PI3K activity assays confirmed that these compounds directly inhibit PI3K activity at µM-range concentrations. FK-A5 analog was the most potent inhibitor. Western blotting revealed that these compounds inhibit phosphorylation of protein kinase B and downstream signaling components. Molecular modeling of the PI3K-FK228 complex indicated that FK228 binds to the ATP-binding pocket of PI3K. At µM-range concentrations, FK228 and FK-A5 show potent cytotoxicity, inducing apoptosis even in HDAC inhibitor-resistant cells. Furthermore, HDAC/PI3K dual inhibition by FK228 and FK-A5 at µM-range concentrations potentiates the apoptosis induction, mimicking the effect of combining specific HDAC and PI3K inhibitors. In this study, we showed that FK228 and its analogs directly inhibit PI3K activity and induce apoptosis at µM-range concentrations, similar to HDAC/PI3K dual inhibition. In future, optimizing the potency of FK228 and its analogs against PI3K may contribute to the development of novel HDAC/PI3K dual inhibitors for cancer treatment.

Characterization of cells resistant to the potent histone deacetylase inhibitor spiruchostatin B (SP-B) and effect of overexpressed p21waf1/cip1 on the SP-B resistance or susceptibility of human leukemia cells.

We previously showed that the B cell leukemia cell line NALM-6 had the highest susceptibility among a number of leukemia cell lines to spiruchostatin B (SP-B), a potent histone deacetylase (HDAC) inhibitor. We also showed that SP-B-induced cytotoxicity depended on induction of apoptosis that was mediated by p21waf1/cip1 expression. In the present study, we generated and characterized a stable, SP-B-resistant NALM-6 cell line (NALM-6/SP-B) by continuous exposure to SP-B, starting with a low SP-B concentration. NALM-6/SP-B cells were also more resistant to FK228, which has a similar chemical structure to SP-B, and were slightly more resistant to the P-gp substrates doxorubicin and vincristine than parental cells, but displayed similar susceptibility to other HDAC inhibitors and to paclitaxel as the parental cells. There was little change in the basal mRNA expression of HDAC1, p53, Bax, Bcl-2, Fas, caspase-3, c-Myc and MDR1 in NALM-6/SP-B compared to parental cells, but the mRNA expression of p21waf1/cip1 was decreased. The introduction of an exogenous p21waf1/cip1 expression vector restored SP-B induction of NALM-6/SP-B cell apoptosis. Moreover, overexpressed p21waf1/cip1 enhanced SP-B induction of the apoptosis of the human erythroleukemia leukemia cell line K562 which is less susceptible to SP-B than NALM-6 cells. These results suggest that downregulation of p21waf1/cip1, which is a characteristic feature of NALM-6/SP-B cells, was important for their resistance to SP-B, and that this SP-B resistance could be overcome by the introduction of exogenous p21waf1/cip1. Furthermore, introduction of p21waf1/cip1 to other leukemia cells such as K562 may enhance their susceptibility to SP-B. This is the first report of the characterization of SP-B-resistant cells and of the effect of overexpressed p21waf1/cip1 on the resistance or susceptibility of human leukemia cells to SP-B.

Involvement of p21waf1/cip1 expression in the cytotoxicity of the potent histone deacetylase inhibitor spiruchostatin B towards susceptible NALM-6 human B cell leukemia cells.

Spiruchostatin B (SP-B) is a potent histone deacetylase (HDAC) inhibitor that has potential for the chemotherapy of leukemia. The aim of this study was to study the susceptibility of human leukemia cell lines to SP-B. We found that NALM-6 human B cell leukemia cells are the most susceptible to SP-B. There was a low correlation between the expression of HDAC1 mRNA and HDI susceptibility of leukemia cells. NALM-6 has higher endogenous p21waf1/cip1 mRNA expression than other leukemia cells. SP-B-induced cytotoxicity was mediated by induction of histone acetylation via inhibition of HDACs, and this effect of SP-B was associated with apoptosis, which was mediated by caspase activation in NALM-6 cells. SP-B time-dependently increased the size of the sub-G1 (apoptotic) peak, and this effect correlated with SP-B induction of cellular apoptotic features such as changes in nuclear morphology. SP-B significantly increased p21waf1/cip1 expression prior to induction of apoptosis. In conclusion, NALM-6 cells, which have a higher expression of p21waf1/cip1 mRNA than other leukemia cell lines, were susceptible to SP-B-induced cytotoxicity that resulted in induction of apoptosis. Our findings may be useful when establishing a therapeutic strategy based on SP-B.

Total synthesis of (+)-stachyflin: a potential anti-influenza A virus agent.

The first enantioselective total synthesis of (+)-stachyflin, a potential anti-influenza A virus agent, was achieved; the method features a BF(3).Et(2)O-induced domino epoxide-opening/rearrangement/cyclization reaction to stereoselectively form the requisite pentacyclic ring system in one step.

Trends in antimicrobial susceptibility of Streptococcus pneumoniae in the Tohoku district of Japan: a longitudinal analysis from 1998 to 2007.

Streptococcus pneumoniae is a common cause of respiratory tract infections (RTIs). The prevalence of Streptococcus pneumoniae strains with reduced susceptibility to antimicrobial agents has dramatically increased worldwide. Susceptibility to nine antimicrobial agents and serotypes were determined among 1,644 Streptococcus pneumoniae strains isolated from patients with RTIs in the Tohoku district of Japan from October to December every year from 1998 to 2007. The prevalence of penicillin G-nonsusceptible Streptococcus pneumoniae (PNSP) strains increased gradually from 48.5% in 1998, reached a statistical peak in 2004 (65.1%) and then decreased to 51.5% in 2007. Streptococcus pneumoniae strains with each serotype 3, 6, 19 and 23 were constantly detected, and the distribution of these serotypes in PNSP strains did not significantly change during the study period. A trend of Streptococcus pneumoniae strains nonsusceptible to other beta-lactams tested was similar to that of PNSP strains, except for cefditoren, to which the resistance rate was < 20% throughout the analysis period. The prevalence of strains nonsusceptible to erythromycin and minocycline were consistently > 60%. Almost all penicillin G-resistant Streptococcus pneumoniae (PRSP) strains were resistant to both erythromycin and minocycline throughout the analysis period. The prevalence of strains resistant to fluoroquinolones tested were < 3% over the study period. Our longitudinal surveillance demonstrated for the first time that decreased prevalence of both beta-lactam- and multidrug-resistant strains has been occurring since 2004 in a region of Japan. Careful monitoring of antimicrobial susceptibility of Streptococcus pneumoniae should be continued.