Gong Grace Q, Kendall Jackie D, Dickson James M J, Rewcastle Gordon W, Buchanan Christina M, Denny William A, Shepherd Peter R, Flanagan Jack U
Department of Molecular Medicine, The University of Auckland, Auckland, New Zealand.
Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand.
Biochem J. 2017 Jun 26;474(13):2261-2276. doi: 10.1042/BCJ20161098.
Phosphoinositide 3-kinases (PI3Ks) are major regulators of many cellular functions, and hyperactivation of PI3K cell signalling pathways is a major target for anticancer drug discovery. PI3Kα is the isoform most implicated in cancer, and our aim is to selectively inhibit this isoform, which may be more beneficial than concurrent inhibition of all Class I PI3Ks. We have used structure-guided design to merge high-selectivity and high-affinity characteristics found in existing compounds. Molecular docking, including the prediction of water-mediated interactions, was used to model interactions between the ligands and the PI3Kα affinity pocket. Inhibition was tested using lipid kinase assays, and active compounds were tested for effects on PI3K cell signalling. The first-generation compounds synthesized had IC (half maximal inhibitory concentration) values >4 μM for PI3Kα yet were selective for PI3Kα over the other Class I isoforms (β, δ and γ). The second-generation compounds explored were predicted to better engage the affinity pocket through direct and water-mediated interactions with the enzyme, and the IC values decreased by ∼30-fold. Cell signalling analysis showed that some of the new PI3Kα inhibitors were more active in the H1047R mutant bearing cell lines SK-OV-3 and T47D, compared with the E545K mutant harbouring MCF-7 cell line. In conclusion, we have used a structure-based design approach to combine features from two different compound classes to create new PI3Kα-selective inhibitors. This provides new insights into the contribution of different chemical units and interactions with different parts of the active site to the selectivity and potency of PI3Kα inhibitors.
磷酸肌醇3-激酶（PI3Ks）是许多细胞功能的主要调节因子，PI3K细胞信号通路的过度激活是抗癌药物研发的主要靶点。PI3Kα是与癌症关系最为密切的亚型，我们的目标是选择性抑制该亚型，这可能比同时抑制所有I类PI3Ks更具优势。我们采用结构导向设计，融合现有化合物中发现的高选择性和高亲和力特性。利用分子对接，包括对水介导相互作用的预测，来模拟配体与PI3Kα亲和力口袋之间的相互作用。通过脂质激酶测定来测试抑制作用，并测试活性化合物对PI3K细胞信号传导的影响。合成的第一代化合物对PI3Kα的IC（半数最大抑制浓度）值>4 μM，但对PI3Kα的选择性高于其他I类亚型（β、δ和γ）。预测所探索的第二代化合物通过与酶的直接和水介导相互作用能更好地结合亲和力口袋，IC值下降了约30倍。细胞信号分析表明，与携带E545K突变的MCF-7细胞系相比，一些新的PI3Kα抑制剂在携带H1047R突变的细胞系SK-OV-3和T47D中活性更高。总之，我们采用基于结构的设计方法，结合两种不同化合物类别的特征，创建了新的PI3Kα选择性抑制剂。这为不同化学单元以及与活性位点不同部分的相互作用对PI3Kα抑制剂的选择性和效力的贡献提供了新的见解。
