Published papers

In the course of screening for an inhibitor of farnesyl transferase (FTase), we identified two compounds, N-benzyl-aclacinomycin A (ACM) and N-allyl-ACM, which are new derivatives of ACM. N-benzyl-ACM and N-allyl-ACM inhibited FTase activity with IC 50 values of 0.86 and 2.93 μM, respectively. Not only ACM but also C-10 epimers of each ACM derivative failed to inhibit FTase. The inhibition of FTase by N-benzyl-ACM and N-allyl-ACM seems to be specific, because these two compounds did not inhibit geranylgeranyltransferase or geranylgeranyl pyrophosphate (GGPP) synthase up to 100 μM. In cultured A431 cells, N-benzyl-ACM and N-allyl-ACM also blocked both the membrane localization of H-Ras and activation of the H-Ras-dependent PI3K/Akt pathway. In addition, they inhibited epidermal growth factor (EGF)-induced migration of A431 cells. Thus, N-benzyl-ACM and N-allyl-ACM inhibited EGF-induced migration of A431 cells by inhibiting the farnesylation of H-Ras and subsequent H-Ras-dependent activation of the PI3K/Akt pathway. © 2013 Japan Antibiotics Research Association All rights reserved.

Isoflavone glucosides (2′-hydroxy,5-methoxy genistein-7-O-glucoside (1), 2′-hydroxy genistein-7-O-gentibioside (2), 5-methoxy genistein-7-O-glucoside (3), 3′,5-dimethoxy genistein-7-O-glucoside (4), 2′-hydroxy genistein-7-O-glucoside (5), genistein-7-O-gentibioside (6), 2′-hydroxy,5-methoxy genistein-4′,7-O-diglucoside (7), and 2′-hydroxy genistein-4′,7-O-diglucoside (8)) were isolated from the groundnut of Apios americana Medik. Their structures were elucidated on the basis of HR-ESI-MS and 1D- and 2D-NMR analyses. Compounds 1, 2, 4, and 7 are new compounds presented here for the first time. Compounds 2 and 5 were proven to be androgen receptor antagonists due to their binding activities for androgen receptors (IC50 280 and 160 μM, respectively) and the inhibitory activity of androgen-induced expression of prostate-specific antigen (PSA) mRNA in LNCaP (prostate adenocarcinoma) cells (IC50 20 and 18 μM, respectively). © 2013 American Chemical Society.

We searched for compounds that affect the cyclin D1/retinoblastoma protein pathway from the in-house natural product library using a recombinant adenovirus with the Cre/loxP-regulated cyclin D1 overexpression system, and we found that oligomycin inhibited cell growth more effectively in cyclin D1-overexpressing SW480 cells than in control SW480 cells. We also found that oligomycin reduced the expression levels of cyclin D1 protein and that this reduction is, at least in part, mediated by Thr-286 phosphorylation-dependent proteasomal degradation. © 2009 Japan Antibiotics Research Association.

Cyclin D1 is frequently overexpressed in human esophageal cancer. We examined the possible role of cyclin D1 overexpression on specific malignant properties of tumor cells using a series of eight human esophageal cancer cell lines that express different levels of cyclin D1. We did not find a simple correlation between levels of cyclin D1 expression and anchorage-independent growth, production of angiogenic factors, or tumorigenicity in nude mice, suggesting that other factors can influence these parameters. We did, however, obtain evidence that tumorigenicity appeared to require both the capacity for anchorage-independent growth and the production of angiogenic factors. To better assess the specific role of cyclin D1, we stably expressed an antisense cyclin D1 cDNA construct in the tumorigenic cell line TTn. This significantly decreased anchorage-independent growth and VEGF production and led to a loss of tumorigenicity in nude mice. Furthermore, these cells diplayed a marked increase in sensitivity to antitumor agents and to Fas antibody-induced apoptosis. Taken together, these findings suggest that the overexpression of cyclin D1 can confer esophageal cancer cells with enhanced malignancy through increases in anchorage-independent growth and VEGF production, and down-regulation of Fas expression, thus suggesting novel functions of the cyclin D1 protein in tumor progression.

Isolated tea chloroplasts utilized linoleic acid, linolenic acid and their 13-hydroperoxides as substrates for volatile C6-aldehyde formation. Optimal pH values for oxygen uptake, hydroperoxide lyase and the overall reaction from C18-fatty acids to C6-aldehydes were 6.3, 7.0 and 6.3, respectively. Methyl linoleate, linoleyl alcohol and γ-linolenic acid were poor substrates for the overall reaction, but linoleic and linolenic acids were good substrates. The 13-hydroperoxides of the above fatty acids and alcohol also showed substrate specificity similar to that of fatty acids. Oxygen uptakes (relative Vmax) with methyl linoleate, linoleyl alcohol, linolenic acid, γ-linolenic acid and arachidonic acid were comparable to or higher than that with linoleic acid. In winter leaves, the activity for C6-aldehyde formation from C18-fatty acids was raduced to almost zero. This was due to the reduction in oxygenation. The findings presented here provide evidence for the involvement of lipoxygenase and hydroperoxide lyase in C6-aldehyde formation in isolated chloroplasts. Copyright © 1982. The Japanese Society of Plant Physiologists.

Quinotrierixin was isolated from microbes as an inhibitor of ER stress-induced XBPl mRNA splicing, but its mode of action was unclear. We found that quinotrierixin is an inhibitor of protein synthesis, and that the required dose range of quinotrierixin to inhibit ER stress-induced XBPl mRNA splicing was similar to that to inhibit protein synthesis. Furthermore, we also found that quinotrierixin inhibited the ER stress-induced increases of unfolded protein response-related genes such as GRP78, CHOP, EDEM, ERdj4, and p58IPK. Thus, we showed that quinotrierixin inhibited the ER stress-induced unfolded protein response, possibly due to its inhibitory activity of protein synthesis.

Fibroblast growth factors (FGF) and their receptors play an important role in cell proliferation, angiogenesis and embryonal development. In this study, we show that expression of the FGF receptor-2 (FGFR-2) protein is induced in the mid-to-late G1 phase of the cell cycle in serum-starved mouse NIH3T3 cells released from starvation. Transcription of mouse FGFR-2 was activated by E2F-1. Analysis of various mouse FGFR-2 promoter mutant constructs showed that a sequence located +57/+64 downstream of the transcriptional initiation site, related to the consensus E2F-responsive sequence, is necessary for the activation. The promoter activity of the mouse FGFR-2 gene is also positively regulated by E2F-2 and E2F-3, but not by E2F-4 and E2F-5. Moreover, the E2F-1-induced activation of mouse FGFR-2 gene transcription is suppressed by pRB. Taken together, the results demonstrate that FGFR-2 is a new class of targets for E2F, and expression of mouse FGFR-2 in mid-to-late G1 phase would be mediated, at least in part, by the activation of a pRB/E2F pathway. © 2003 Nature Publishing Group.

In the course of screening for an inhibitor of ER stress-induced XBP1 activation, we isolated a new member of the triene-ansamycin group compound, quinotrierixin, from a culture broth of Streptomyces sp. PAE37. Quinotrierixin inhibited thapsigargin-induced XBP1 activation in HeLa cells with an IC 50 of 0.067 μM. We found that other triene-ansamycin group compounds such as demethyltrienomycin A and mycotrienin I also inhibited ER stress-induced XBP1 activation. Moreover, we performed SAR study of twelve triene-ansamycin group compounds. The study showed that OH group at C-13 was crucial, and CH3 group at C-14 would be important for the XBP1 inhibitory activity. © Japan Antibiotics Research Association.

Four novel triene-ansamycin group compounds, quinotrierixin, demethyltrienomycin A, demethyltrienomycin B and demethyltrienomycinol, were isolated from the culture broth of Streptomyces sp. PAE37 as inhibitors of ER stress-induced XBP1 activation. The structures of quinotrierixin, demethyltrienomycin A, demethyltrienomycin B and demethyltrienomycinol were determined on the basis of their spectroscopical and chemical properties. All of four possessed 21-membered macrocyclic lactams including triene moieties. © Japan Antibiotics Research Association.

ホスファチジルイノシトール代謝回転阻害剤イノスタマイシンが、小細胞肺癌細胞に対して、サイクリンD1の発現を抑制しG1期停止を引き起こし、更にアポトーシスを誘導することを報告した。(8ページ)

正常細胞において、血清で誘導されるS期移行にホスファチジルイノシトール合成が重要な役割を演じている可能性を報告した。(6ページ)

チロシンキナーゼ阻害剤アーブスタチンが、T細胞の活性化を抑制することを報告した。(2ページ)

熱帯植物モリンダシトリフォリアからras癌遺伝子で形質転換した細胞の形態正常化を誘導する物質ダムナカンタールを単離し、報告した。(6ページ)

チロシンキナーゼ阻害剤アーブスタチンが、NIH3T3細胞のPDGFやボンベシンにより誘導されるホスホリパーゼＣの活性化を抑制したことを報告した。(５ページ)

ホスファチジルイノシトール代謝回転阻害剤であるイノスタマイシンの阻害作用点を解析し、イノスタマイシンがCDP-DG:イノシトールトランスフェラーゼであることを報告した。（4ページ）

チロシンキナーゼ阻害剤アーブスタチンの安定誘導体がラウス肉腫ウイルスで形質転換した細胞のチロシンキナーゼを阻害しサーク癌遺伝子の機能を阻害することを報告した。(3ページ)

ホスファチジルイノシトール代謝回転阻害剤であるプシテクトリゲニンが、EGFにより誘導されるホスホリパーゼＣの活性化を抑制したことを報告した。(3ページ)