Irosustat potently inhibits rat liver, with inhibition of >90% when at a 1 mg/kg concentration. Irosustat (2 mg/kg, p.o. for 5 d) blocks the uterine growth stimulated by oestrone sulfate (E1S) in ovariectomized rats. In addition, Irosustat (2, 10 mg/kg, p.o.) plus E1S dose-dependently decreases the growth of NMU-induced mammary tumors in ovariectomized rats[1]. Irosustat (667 COUMATE; 10 mg/kg, p.o.) shows 97.9 ± 0.06% inhibition on steroid sulphatase (STS) activity in rat liver[2].
In Vitro
Irosustat (667 COUMATE) is a potent steroid sulfatase inhibitor, with an IC50 of 8 nM[1]. Irosustat (667 COUMATE) inhibits steroid sulphatase (STS) activity in MCF-7 cells with an IC50 of 0.2 nM, but has no effect on the morphology or proliferation of MCF-7 cells at 10 μM[2].
Kinase Assay
Cell Assay
MCF-7 cells are cultured in growth medium (minimum essential medium (MEM) containing, phenol red, 10% foetal calf serum (FCS) and essential nutrients). When the cells reach 60% confluency, they are treated with Irosustat (0.001-10 μM) in growth medium. After 72 h of incubation, photographs are taken under normal conditions of light and the number of attached cells in each flask is determined using a Coulter cell counter[2].
Animal Administration
Rats[1] Ludwig rats bearing mammary tumors are used in the assay. Tumor development is monitored, and animals are ovariectomized when tumors reach 0.8-1.5 cm in diameter. Tumors are allowed to regress over a 12- to 13-day period to confirm their hormone-dependent status. Regrowth of tumors is stimulated with oestrone sulfate (E1S; 50 μg/day, s.c.). When tumors have regrown, animals continue to receive either E1S alone or E1S plus Irosustat at 10 mg/kg/day or 2 mg/kg/day, p.o., until tumor regression has occurred. Tumor volumes are calculated from two measured diameters[1].
References
[1]. Purohit A, et al. In vivo inhibition of estrone sulfatase activity and growth of nitrosomethylurea-induced mammary tumors by 667 COUMATE. Cancer Res. 2000 Jul 1;60(13):3394-6.
[2]. Raobaikady B, et al. Inhibition of MCF-7 breast cancer cell proliferation and in vivo steroid sulphatase activity by 2-methoxyoestradiol-bis-sulphamate. J Steroid Biochem Mol Biol. 2003 Feb;84(2-3):351-8.
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