Boivin R P, Luu-The V, Lachance R, Labrie F, Poirier D
Medicinal Chemistry Division and MRC Group in Molecular Endocrinology, Oncology and Molecular Endocrinology Research Center, Laval University Medical Center (CHUL), 2705 Laurier Boulevard, Sainte-Foy, Québec G1V 4G2, Canada.
J Med Chem. 2000 Nov 16;43(23):4465-78. doi: 10.1021/jm0001166.
The steroid sulfatase or steryl sulfatase is a microsomal enzyme widely distributed in human tissues that catalyzes the hydrolysis of sulfated 3-hydroxy steroids to the corresponding free active 3-hydroxy steroids. Since androgens and estrogens may be synthesized inside the cancerous cells starting from dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E(1)S) available in blood circulation, the use of therapeutic agents that inhibit steroid sulfatase activity may be a rewarding approach to the treatment of androgeno-sensitive and estrogeno-sensitive diseases. In the present study, we report the chemical synthesis and biological evaluation of a new family of steroid sulfatase inhibitors. The inhibitors were designed by adding an alkyl, a phenyl, a benzyl, or a benzyl substituted at position 17alpha of estradiol (E(2)), a C18-steroid, and enzymatic assays were performed using the steroid sulfatase of homogenized JEG-3 cells or transfected in HEK-293 cells. We observed that a hydrophobic substituent induces powerful inhibition of steroid sulfatase while a hydrophilic one was weak. Although a hydrophobic group at the 17alpha-position increased the inhibitory activity, the steric factors contribute to the opposite effect. As exemplified by 17alpha-decyl-E(2) and 17alpha-dodecyl-E(2), a long flexible side chain prevents adequate fitting into the enzyme catalytic site, thus decreasing capacity to inhibit the steroid sulfatase activity. In the alkyl series, the best compromise between hydrophobicity and steric hindrance was obtained with the octyl group (IC(50) = 440 nM), but judicious branching of side chain could improve this further. Benzyl substituted derivatives of estradiol were better inhibitors than alkyl analogues. Among the series of 17alpha-(benzyl substituted)-E(2) derivatives studied, the 3'-bromobenzyl, 4'-tert-butylbenzyl, 4'-butylbenzyl, and 4'-benzyloxybenzyl groups provided the most potent inhibition of steroid sulfatase transformation of E(1)S into E(1) (IC(50) = 24, 28, 25, and 22 nM, respectively). As an example, the tert-butylbenzyl group increases the ability of the E(2) nucleus to inhibit the steroid sulfatase by 3000-fold, and it also inhibits similarly the steroid sulfatase transformations of both natural substrates, E(1)S and DHEAS. Interestingly, the newly reported family of steroid sulfatase inhibitors acts by a reversible mechanism of action that is different from the irreversible mechanism of the known inhibitor estrone sulfamate (EMATE).
类固醇硫酸酯酶或甾体硫酸酯酶是一种广泛分布于人体组织中的微粒体酶，它催化硫酸化的3-羟基类固醇水解为相应的游离活性3-羟基类固醇。由于雄激素和雌激素可在癌细胞内从血液循环中可得的硫酸脱氢表雄酮（DHEAS）和硫酸雌酮（E(1)S）开始合成，因此使用抑制类固醇硫酸酯酶活性的治疗药物可能是治疗雄激素敏感性和雌激素敏感性疾病的一种有效方法。在本研究中，我们报道了一类新型类固醇硫酸酯酶抑制剂的化学合成及生物学评价。这些抑制剂是通过在雌二醇（E(2)，一种C18甾体）的17α位添加一个烷基、一个苯基、一个苄基或一个苄基取代基来设计的，并使用匀浆的JEG-3细胞的类固醇硫酸酯酶或转染到HEK-293细胞中的该酶进行酶活性测定。我们观察到，疏水取代基可强力抑制类固醇硫酸酯酶，而亲水取代基的抑制作用较弱。尽管17α位的疏水基团增加了抑制活性，但空间因素却起相反作用。以17α-癸基-E(2)和17α-十二烷基-E(2)为例，长的柔性侧链妨碍了其充分适配到酶催化位点，从而降低了抑制类固醇硫酸酯酶活性的能力。在烷基系列中，辛基在疏水性和空间位阻之间取得了最佳平衡（IC(50) = 440 nM），但侧链的合理分支可进一步改善这一情况。雌二醇的苄基取代衍生物比烷基类似物是更好的抑制剂。在所研究的17α-（苄基取代）-E(2)衍生物系列中，3'-溴苄基、4'-叔丁基苄基、4'-丁基苄基和4'-苄氧基苄基对硫酸雌酮（E(1)S）转化为雌酮（E(1)）的类固醇硫酸酯酶具有最强的抑制作用（IC(50)分别为24、28、25和22 nM）。例如，叔丁基苄基使E(2)核抑制类固醇硫酸酯酶的能力提高了3000倍，并且它对两种天然底物E(1)S和DHEAS的类固醇硫酸酯酶转化也有类似的抑制作用。有趣的是，新报道的这类类固醇硫酸酯酶抑制剂通过一种可逆的作用机制发挥作用，这与已知抑制剂硫酸雌酮氨基甲酸酯（EMATE）的不可逆作用机制不同。
