Sakiko Maruyama

Total synthesis of 12-methoxydihydrochelerythrine and anti-tumour activity of its quaternary base: toward an efficient synthetic route for 12-alkoxybenzo[c]phenanthridine bases via naphthoquinone monooxime from 2-benzofuranyl-1-tetralone derivative.

A concise total synthesis of 12-methoxydihydrochelerythrine (6), isolated from Bocconia integrifolia, is described. The synthesis features an efficient route to a 12-alkoxybenzo[c]phenanthridine skeleton via naphthoquinone monooxime 11 as a key compound. Starting from 7-methoxy-2-methylbenzo[b]furan (9), 3-aryl-1-tetralone 10 was synthesised, followed by aromatisation to 3-aryl-1-naphthol 17. After oxidative cleavage of the furan ring, basic nitrosation of naphthol 22 gave the naphthoquinone 11. The benzo[c]phenanthridine skeleton was formed by reductive cyclisation of 11. Deoxygenation of the lactam moiety in 23 afforded nor-base 32 and methylation of 32 under reductive conditions gave the target dihydro base 6 (23 steps from benzofuran 9 in 10% overall yield). The corresponding quaternary base 7 showed moderate anti-tumour activity against cancer cell lines; on NCI-H460: IC50 4.5 microM and on MDA-MB-231: IC50 1.2 microM. Introduction of a methoxy group into the 12-position of the benzo[c]phenanthridine skeleton could cause enhanced activity against MDA-MB-231 by comparison of 7 with chelerythrine (35) (IC50 5.3 microM).

A Novel Compound, NK150460, Exhibits Selective Antitumor Activity against Breast Cancer Cell Lines through Activation of Aryl Hydrocarbon Receptor

Antiestrogen agents are commonly used to treat patients with estrogen receptor (ER)–positive breast cancer. Tamoxifen has been the mainstay of endocrine treatment for patients with early and advanced breast cancer for many years. Following tamoxifen treatment failure, however, there are still limited options for subsequent hormonal therapy. We discovered a novel compound, NK150460, that inhibits 17β-estradiol (E2)–dependent transcription without affecting binding of E2 to ER. Against our expectations, NK150460 inhibited growth of not only most ER-positive, but also some ER-negative breast cancer cell lines, while never inhibiting growth of non–breast cancer cell lines. Cell-based screening using a random shRNA library, identified aryl hydrocarbon receptor nuclear translocator (ARNT) as a key gene involved in NK150460′s antitumor mechanism. siRNAs against not only ARNT but also its counterpart aryl hydrocarbon receptor (AhR) and their target protein, CYP1A1, dramatically abrogated NK150460′s growth-inhibitory activity. This suggests that the molecular cascade of AhR/ARNT plays an essential role in NK150460′s antitumor mechanism. Expression of ERα was decreased by NK150460 treatment, and this was inhibited by an AhR antagonist. Unlike two other AhR agonists now undergoing clinical developmental stage, NK150460 did not induce histone H2AX phosphorylation or p53 expression, suggesting that it did not induce a DNA damage response in treated cells. Cell lines expressing epithelial markers were more sensitive to NK150460 than mesenchymal marker-expressing cells. These data indicate that NK150460 is a novel AhR agonist with selective antitumor activity against breast cancer cell lines, and its features differ from those of the other two AhR agonists. Mol Cancer Ther; 14(2); 343–54. ©2014 AACR.

Comparative metabolic study between two selective estrogen receptor modulators, toremifene and tamoxifen, in human liver microsomes☆

Toremifene (TOR) and Tamoxifen (TAM) are widely used as endocrine therapy for estrogen receptor positive breast cancer. Poor metabolizers of TAM are likely to have worse clinical outcomes than patients who exhibit normal TAM metabolism due to lower plasma level of its active metabolite, 4-hydroxy-N-desmethyl (4OH-NDM) tamoxifen (endoxifen). In this study, we examined the role of individual cytochrome P450 (CYP) isoforms in the metabolism of TOR to N-desmethyl (NDM), 4-hydroxy (4OH) and 4OH-NDM metabolites in comparison with TAM using human liver microsomes (HLMs) with selective chemical inhibitors for each CYP isoform and recombinant CYP proteins. Similar levels of NDM metabolites were formed for both TOR and TAM, and N-demethylation of both compounds was primarily carried out by CYP3A4. We found that the formation of 4OH-NDM-TOR was catalyzed both by CYP2C9 and CYP2D6, whereas the formation of 4OH-TAM and endoxifen was specifically catalyzed by CYP2D6 in HLMs. Our results suggest that the potential contribution of CYP2D6 in the bioactivation pathway of TOR may be lower compared to TAM, and may have a different impact on clinical outcome than CYP2D6 polymorphisms.