Quinofuracins A-E, produced by the fungus Staphylotrichum boninense PF1444, show p53-dependent growth suppression.

Quinofuracins A-E, novel anthraquinone derivatives containing ß-D-galactofuranose that were isolated from the fungus Staphylotrichum boninense PF1444, induced p53-dependent cell death in human tumor cells. The structures of quinofuracins A-E, including absolute configurations, were elucidated by extensive spectroscopic analysis and chemical transformation studies. Quinofuracins were classified into three groups according to the aglycone moieties. 5'-Oxoaverantin was present in quinofuracins A-C, whereas averantin and versicolorin B were identified in quinofuracins D and E, respectively. These quinofuracins induced p53-dependent growth suppression in human glioblastoma LNZTA3 cells.

Androprostamines A and B, the new anti-prostate cancer agents produced by Streptomyces sp. MK932-CF8.

Androgen receptor (AR) is a validated target in all clinical states of prostate cancer. Androprostamines A and B, the new inhibitors of androgen receptor, were isolated from Streptomyces sp. MK932-CF8. Their structures were determined by the spectroscopic analysis, degradation studies and synthesis. Androprostamines showed potent inhibitory effect against androgen-dependent growth of human prostate cancer cells without cytotoxicity and repressed the androgen-induced expression of AR-regulated genes.

Structure and biological properties of lentztrehalose: a novel trehalose analog.

A new trehalose analog, lentztrehalose [4-O-(2,3-dihydroxy-3-methylbutyl)trehalose], was isolated from an actinomycete Lentzea sp. Lentztrehalose is only weakly hydrolyzed by the trehalose-hydrolyzing enzyme, trehalase, so can be regarded as an enzyme-stable analog of trehalose. Although lentztrehalose does not show apparent toxicity to mammalian cells and microbes, it has antitumor activity in mice bearing S-180 sarcoma and Ehrlich carcinoma cells. In ovariectomized mice, lentztrehalose displayed a bone reinforcement effect in the femur that was superior to trehalose and induced non-morbid suppression of weight gain comparable with trehalose. These results indicate that enzyme-stable analogs of trehalose, such as lentztrehalose, may be more beneficial for human health and thus have potential as substitutes for trehalose as a sweetener.

NBRI16716A, a new antitumor compound against human prostate cancer cells, produced by Perisporiopsis melioloides Mer-f16716.

Prostate stroma can regulate the growth and metastasis of prostate cancer through the tumor-stromal cell interactions. Thus, small molecules that modulate the tumor-stromal cell interactions will have a chance to become new antitumor drugs. In the course of our screening of the modulators, we isolated three new natural compounds, NBRI16716A (1), NBRI16716B (2) and NBRI16716C (3), from the fermentation broth of Perisporiopsis melioloides Mer-f16716, although compound 2 was already reported as a chemical degradation product of isotriornicin. Compounds 1 and 2 inhibited the growth of human prostate cancer DU-145 cells in the coculture with human prostate stromal cells (PrSCs) more strongly than that of DU-145 cells alone. Furthermore, both compounds showed antitumor effect against xenograft models of DU-145 cells and PrSCs in vivo.

NBRI17671, a new antitumor compound, produced by Acremonium sp. CR17671.

The interaction between the receptor for advanced glycation end-product (RAGE) and amphoterin has an important role in tumor growth and metastasis. Because the abrogation of the interaction results in the inhibition of the tumor growth and metastasis, we designed a screening system for an inhibitor of the interaction between RAGE and amphoterin. In the course of our screening of the inhibitor, we isolated a novel natural compound NBRI17671 (1) from the fermentation broth of Acremonium sp. CR17671. We also modified 1 into a more active NBRI17671al (2). Although 1 at 50 g ml(-1) weakly inhibited binding of various cells to amphoterin, 2 at 50 g ml(-1) inhibited it by >50% of control. Compound 2 effectively inhibited the tumor growth of glioma and lung tumor xenografts in mice at 25 mg kg(-1). Furthermore, 2 was found to downregulate mitogen-activated protein kinase (MAPK) activity in the tumor cells.

Rubratoxin A specifically and potently inhibits protein phosphatase 2A and suppresses cancer metastasis.

Although cytostatin analog protein phosphatase 2A (PP2A)-specific inhibitors are promising candidates of a new type of anticancer drug, their development has been hindered because of their liability. To find new classes of PP2A-specific inhibitors, we conducted a screening with microbial metabolites and found that rubratoxin A, a classical mycotoxin, is a highly specific and potent inhibitor of the enzyme. While rubratoxin A inhibits PP2A at Ki = 28.7 nm, it hardly inhibited any other phosphatases examined. Rubratoxin B, a close analog, also specifically but weakly inhibits PP2A at Ki = 3.1 microM. The inhibition of intracellular PP2A in cultured cells is obviously observed with 20 microM rubratoxin A treatment for 3 h, inducing the overphosphorylation in PP2A substrate proteins. Although rubratoxins and cytostatin differ in the apparent structures, these compounds share similarities in the structures in detail and PP2A-binding manners. Rubratoxin A showed higher suppression of tumor metastasis and reduction of the primary tumor volume than cytostatin in mouse experiments. As a successor of cytostatin analogs, rubratoxin A should be a good compound leading to the development of antitumor drugs targeting PP2A.

New atpenins, NBRI23477 A and B, inhibit the growth of human prostate cancer cells.

The growth and metastasis of prostate cancer are regulated by prostate stroma through the tumor-stromal cell interactions. Small molecules that modulate the tumor-stromal cell interactions will be new anticancer drugs. In the course of our screening of the modulators, we isolated two new atpenins, NBRI23477 A (4) and B (5), from the fermentation broth of Penicillium atramentosum PF1420. Compounds 4 and 5 as well as atpenin A4 (1), A5 (2) and B (3) inhibited the growth of human prostate cancer DU-145 cells in the coculture with human prostate stromal cells more strongly than that of DU-145 cells alone.

Ceramidastin, a novel bacterial ceramidase inhibitor, produced by Penicillium sp. Mer-f17067.

Decrease of ceramide in the skin is one of the aggravating factors of atopic dermatitis. The skin is often infected by ceramidase-producing bacteria, such as Pseudomonas aeruginosa. The bacterial ceramidase then degrades ceramide in the skin. To develop anti-atopic dermatitis drugs, we searched for ceramidase inhibitors, which led to the discovery of ceramidastin, a novel inhibitor of bacterial ceramidase, from the culture broth of Penicillium sp. Mer-f17067. Ceramidastin inhibited the bacterial ceramidase with an IC(50) value of 6.25 microg ml(-1). Here we describe the isolation, physicochemical properties, structure determination and biological activity of ceramidastin.

A new terrein glucoside, a novel inhibitor of angiogenin secretion in tumor angiogenesis.

Angiogenesis is a critical step for the tumor therapy. Many angiogenic factors are involved in the tumor angiogenesis. In the course of our screening for inhibitors of angiogenin secretion, one of angiogenic factors, we have isolated a new terrein glucoside (1) and terrein (2) from the fermentation broth of fungal strain Aspergillus sp. PF1381. The structure and absolute stereochemistry of 1 was determined to be (4S,5R)-5-[(alpha-D-glucopyranosyl)oxy]-4-hydroxy-3-(E-1-propenyl)-2-cyclopenten-1-one on the basis of spectral and enzymatic analyses. Compounds 1 and 2 equally inhibited angiogenin secretion from androgen-dependent prostate cancer cells, LNCaP-CR, with IC50 values of 13 microM. However, both compounds did not affect VEGF secretion, another angiogenic factor. Furthermore, both compounds inhibited tube formation of human umbilical vein endothelial cells (HUVEC). These results suggested that 1 and 2 act as angiogenesis inhibitors through the inhibition of angiogenin secretion.

Inhibitory activity of the hypoxia-inducible factor-1 pathway by tartrolone C.

Hypoxia-inducible factor-1 (HIF-1) is a central mediator of cellular responses to low oxygen and has recently become an important therapeutic target for solid tumor therapy. To identify small molecule inhibitors of the HIF-1 transcriptional activation, we have established a high through-put assay system using a stable transformant of mammalian cells that express a luciferase reporter gene construct containing a HIF-1 binding site. Using this system, we screened 5000 cultured broths of microorganisms, and we found that fermentation broth produced by Streptomyces strain 1759-27 showed significant inhibition of the reporter activity induced by hypoxic conditions. The active substance NBRI759-27 was purified and determined to be tartrolone C by several methods including X-ray crystallography. In the reporter gene assay, tartrolone C inhibited the HIF-1 transcriptional activity under hypoxic conditions with an IC50 value of 0.17 microg/ml.

New naphthoquinones, f13102A and B, from a fungus strain F-13102.

Deficiency of Fas-mediated apoptosis is one of the mechanisms involved in the immune evasion by tumors. Thus, it might be a practical approach for cancer treatment that Fas-mediated apoptosis in tumor cells is modified by drugs. In the course of screening, we have isolated two new naphthoquinones, f13102A and B, from the culture broth of fungus strain F-13102. Coumpound f13102A sensitizes Fas-resistant human lung adenocarcinoma A549 cells to apoptosis.

Absolute configuration of kigamicins A, C and D.

The stereochemistry of kigamicins A (1), C (2) and D (3) were elucidated by a combination of X-ray crystallographic analysis and degradation studies. The absolute structures of kigamicins thus determined were depicted as shown in Fig. 2.

A microplate assay for selective measurement of growth of epithelial tumor cells in direct coculture with stromal cells.

Stromal cells play an important role in regulating epithelial malignancies through diffusible factors and adhesion. Modulation of the tumor-stromal cell interaction is an attractive target for new antitumor strategies. To screen for a modulator of the interaction, we have now developed a quantitative colorimetric assay for measurement of tumor cell growth in coculture with stromal cells using rhodanile blue dye. Rhodanile blue specifically stained cytokeratin-positive tumor cells in the coculture. When human prostate carcinoma cells LNCaP, PC-3 and DU-145 were cocultured with normal prostate stromal cells (PrSC) in a microplate, growth of the prostate cancer cells in the coculture was selectively measured by the rhodanile blue staining method. Using this system, we searched for a modulator of the tumor-stromal cell interaction among clinically used drugs and natural products. As a result, we found that 5-fluorouracil, bleomycin and phthoxazolin A inhibit prostate cancer cell growth more strongly in coculture with PrSC than that in monoculture. Without need to pre-label cells and transfect a marker gene, our new method is simple, rapid and thus useful for screening for modulators of the tumor-stromal cell interaction. Furthermore, our results suggest that low molecular weight compounds modulate the tumor-stromal cell interaction.

ICM0301s, new angiogenesis inhibitors from Aspergillus sp. F-1491. I. Taxonomy, fermentation, isolation and biological activities.

In the course of screening program for inhibitors of angiogenesis, novel substances designated as ICM0301A approximately H (1 approximately 8) were isolated from the culture broth of Aspergillus sp. F-1491. ICM0301s inhibited the growth of human umbilical vein endothelial cells (HUVECs) induced by basic fibroblast growth factor (bFGF) with IC50 values of 2.2 approximately 9.3 microg/ml. ICM0301A (1) showed significant anti-angiogenic activity at lower than 10 microg/ml in the angiogenesis model using rat aorta cultured in fibrin gel. ICM0301s showed very low cytotoxicity against various tumor cells. Furthermore, 1CM0301A did not show any toxic symptom in mice by intraperitoneal injection at 100 mg/kg.

ICM0301s, new angiogenesis inhibitors from Aspergillus sp. F-1491. II. Physico-chemical properties and structure elucidation.

ICM0301A (1), B (2) and their congeners (3 approximately 8) were isolated from a culture broth of Aspergillus sp. F-1491 as new angiogenesis inhibitors. Their structures were elucidated by spectroscopic analyses. ICM0301A and B have a substituted decalin skeleton containing two oxirane rings.

Androgen-independent prostate cancer DU145 cells suppress androgen-dependent growth of prostate stromal cells through production of inhibitory factors for androgen responsiveness.

Imbalances in the epithelial-stromal interactions are important in the pathogenesis of prostate cancer. However, we know little about androgenic regulation in the stroma of prostate cancer. We examined the cancer-stromal interaction paying attention to androgen responsiveness of stromal side. In co-culture, PC3 and LNCaP cells did not affect dihydrotestosterone (DHT)-dependent growth of prostate stromal cells (PrSCs), but DU145 cells significantly reduced it. Conditioned medium from DU145 cells (DU145-CM) also inhibited DHT-dependent PrSCs growth, androgen receptor (AR) expression, and prostate specific antigen transcription. Although the inhibitory effect of DU145-CM was not affected by neutralizing antibody against EGF, FGF-2, or TNF-alpha, pretreatment with testosterone-Sepharose partially reduced the inhibitory ability of DU145-CM. These results suggest that DU145 cells produce inhibitory factors for androgen responsiveness, including steroid-binding protein(s), and these may participate in crosstalk between DU145 cells and PrSCs as modulators of androgen.

ICM0201, a new inhibitor of osteoclastogenesis from Cunninghamella sp. F-1490. I. Taxonomy, fermentation, isolation and biological activities.

In the course of screening for inhibitors of osteoclastogenesis, a new substance designated as ICM0201 was isolated from a fermentation broth of Cunninghamella sp. F-1490. ICM0201 inhibited the formation of osteoclasts in mouse bone marrow cells with an IC50 value of 0.78 microg/ml and showed weak cytotoxicity against bone marrow cells.

ICM0201, a new inhibitor of osteoclastogenesis from Cunninghamella sp. F-1490. II. Structure determination and synthesis.

ICM0201 (1), a new inhibitor of murine osteoclastogenesis in culture was isolated from a fermentation broth of Cunninghamella sp. F-1490. The structure of ICM0201 was determined to be (3S,10aR)-3,4a-dihydroxy-2,3,4,4a-tetrahydro-2H-pyrano[3,2-b]benzo[e]morpholine-9-carboxylic acid by spectroscopic analyses and chemical studies. The structure of 1 is unique in that the tricycle ring system is composed of aminal and hemiacetal bonds.