Conformationally Defined Rexinoids and Their Efficacy in the Prevention of Mammary Cancers
作者:Venkatram R. Atigadda、Gang Xia、Anil Deshpande、Lizhi Wu、Natalia Kedishvili、Craig D. Smith、Helen Krontiras、Kirby I. Bland、Clinton J. Grubbs、Wayne J. Brouillette、Donald D. Muccio
DOI:10.1021/acs.jmedchem.5b00829
日期:2015.10.8
(2E,4E,6Z,8Z)-8-(3',4'-Dihydro-1'(2H)-naphthalen-1'-ylidene)-3,7-dimethyl-2,3,6-octatrienoinic acid (UAB30) is currently undergoing clinical evaluation as a novel cancer prevention agent. In efforts to develop even more highly potent rexinoids that prevent breast cancer without toxicity, we further explore here the structure-activity relationship of two separate classes of rexinoids. UAB30 belongs to the class II rexinoids and possesses a 9Z-tetraenoic acid chain bonded to a tetralone ring, whereas the class I rexinoids contain the same 9Z-tetraenoic acid chain bonded to a disubstituted cyclohexenyl ring. Among the 12 class I and class II rexinoids evaluated, the class I readnoid 11 is most effective in preventing breast cancers in an in vivo rat model alone or in combination with tamoxifen. Rexinoid 11 also reduces the size of established tumors and exhibits a therapeutic effect. However, 11 induces hypertriglyceridemia at its effective dose. On the other hand readnoid 10 does not increase triglyceride levels while being effective in the in vivo chemoprevention assay. X-ray studies of four rexinoids bound to the ligand binding domain of the retinoid X receptor reveal key structural aspects that enhance potency as well as those that enhance the synthesis of lipids.
具有((2E,4E,6Z,8Z)-8-(3',4'-dihydro-1'(2H)-naphthalen-1'-ylidene)-3,7-dimethyl-2,3,6-octatrienoinic acid)结构的UAB30是一种正在临床评价中的新型癌症预防剂。为了研发出能够在不引起毒性反应的前提下预防乳腺癌的更高活性的新型类视黄醇(rexinoids),我们进一步探讨了两个不同类别类视黄醇的构效关系。UAB30属于第二类类视黄醇,具有与四氢萘环相连的9Z-四烯酸链,而第一类类视黄醇则具有与二取代环己烯环相连的相同9Z-四烯酸链。
在评估的12种第一类和第二类类视黄醇中,第一类类视黄醇11在预防乳腺癌方面最为有效,无论是单独使用还是与他莫昔芬联用,在体内小鼠模型中均显示出最佳效果。类视黄醇11还能缩小已形成的肿瘤体积,展现出治疗效果。然而,类视黄醇11在其有效剂量下会引起高甘油三酯血症(hypertriglyceridemia)。
另一方面,类视黄醇10在有效浓度下不会升高甘油三酯水平,同时在体内化学预防实验中也表现出有效性。通过对四种类视黄醇与视黄酸X受体(Retinoid X Receptor, RXR)的配体结合域结合的X射线研究显示,这些化合物的某些关键结构特征能够增强效力,同时也揭示了促进脂质合成的结构特点。这一发现为研发更具潜力的新型类视黄醇提供了重要的结构线索和理论依据。