Tadafumi Terada

A novel cinnamic acid derivative that inhibits Cdc25 dual-specificity phosphatase activity

The Cdc25 dual‐specificity phosphatases are key regulators of cell cycle progression through activation of cyclin‐dependent kinases (Cdk). Three homologs exist in humans: Cdc25A, Cdc25B, and Cdc25C. Cdc25A and Cdc25B have oncogenic properties and are overexpressed in some types of tumors. Compounds that inhibit Cdc25 dual‐specificity phosphatase activity might thus be potent anticancer agents. We screened several hundred compounds in a library using an in vitro phosphatase assay, with colorimetric measurement of the conversion of p‐nitrophenyl phosphate (pNPP) to p‐nitrophenol by the catalytic domain of recombinant human Cdc25, and discovered TPY‐835, which inhibits Cdc25A and Cdc25B activity (IC50 = 5.1 and 5.7 µM, respectively). TPY‐835 had mixed inhibition kinetics for Cdc25A and Cdc25B. TPY‐835 caused cell cycle arrest in the G1 phase in human lung cancer cells (A549 and SBC‐5) but not cell cycle arrest in the G2/M phase. After treatment with TPY‐835, the activation of Cdk2 was suppressed and phosphorylation of the retinoblastoma (Rb) protein was decreased in SBC‐5 cells. In addition, TPY‐835 induced an increase of the sub‐G1 phase cell population after 48–72 h treatment. The growth inhibitory effects of TPY‐835 against cisplatin (CDDP)‐, camptothecin‐ and 5‐FU‐resistant cell lines are comparable to the growth inhibitory effect on their parental lines, thus indicating that TPY‐835 did not show cross‐resistance to these cell lines. These results suggest that TPY‐835 is a promising candidate for constructing a novel class of antitumor agents that can control the cell cycle progression of cancer cells. (Cancer Sci 2005; 96: 614–619)

Alteration of dihydropyrimidine dehydrogenase expression by IFN-α affects the antiproliferative effects of 5-fluorouracil in human hepatocellular carcinoma cells

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme in the catabolism of 5-fluorouracil (5-FU) and its activity is closely associated with cellular sensitivity to 5-FU. This study examines the role of DPD in the antiproliferative effects of 5-FU combined with IFN-α on hepatocellular carcinoma (HCC) cells in culture and asks whether IFN-α could affect DPD expression. The combined action of IFN-α and 5-FU on three HCC lines was quantified by a combination index method. Coadministration of IFN-α and 5-FU showed synergistic effects against HAK-1A and KYN-2 but antagonistic effects against KYN-3. The cellular expression levels of DPD mRNA and protein were markedly up-regulated in KYN-3 cells by IFN-α but were down-regulated in HAK-1A and KYN-2. The expression of thymidylate synthase mRNA and protein was down-regulated by IFN-α in all three cell lines. Coadministration of a selective DPD inhibitor, 5-chloro-2,4-dihydroxypyridine (CDHP), enhanced the antiproliferative effect of 5-FU and IFN-α on KYN-3 ∼4-fold. However, the synergistic effects of 5-FU and IFN-α on HAK-1A and KYN-2 were not affected by CDHP. The antiproliferative effect of 5-FU could thus be modulated by IFN-α, possibly through DPD expression, in HCC cells. Inhibition of DPD activity by CDHP may enhance the efficacy of IFN-α and 5-FU combination therapy in patients with HCC showing resistance to this therapy. [Mol Cancer Ther 2007;6(8):2310–8]

Synthesis of novel 5- and 6-substituted 3-arylidene-1,4-oxathiin-2(3H)-ones

The reactions of α-acetylthio-β-arylacrylic acids (2a–c) with α-halogeno ketones (3a–f), α-halogeno-β-keto esters (7a–b), and α-halogenopyruvate (9) afforded the corresponding novel 3-arylidene-1,4-oxathiin-2(3H)-ones [(4a–d), (8a–f), and (10a), respectively] having 5- and/or 6-substituents. The β-aryl-α-thioacrylic acids (1a–d) were treated with α-halogeno ketones (3a–f), (7a–b), and (9) to give the corresponding β-aryl-α-alkylthioacrylic acids (5a–d), (11a–f), and (12a–c), which were converted into the respective 3-arylidene-1,4-oxathiin-2(3H)-ones (4a–g), (8a–f), and (10a–c) by intramolecular cyclization when treated with thionyl chloride–dimethylformamide. The sulphur atom of the 1,4-oxathiin-2(3H)-ones (4d), (4g), and (8a) was smoothly oxidized with m-chloroperbenzoic acid to give the corresponding S-oxides (13a–c) in good yields.