Rammelkamp Center for Research and Department of Medicine, MetroHealth Campus, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
PLoS One. 2012;7(8):e42120. doi: 10.1371/journal.pone.0042120. Epub 2012 Aug 15.
During tumor progression, EphA2 receptor can gain ligand-independent pro-oncogenic functions due to Akt activation and reduced ephrin-A ligand engagement. The effects can be reversed by ligand stimulation, which triggers the intrinsic tumor suppressive signaling pathways of EphA2 including inhibition of PI3/Akt and Ras/ERK pathways. These observations argue for development of small molecule agonists for EphA2 as potential tumor intervention agents. Through virtual screening and cell-based assays, we report here the identification and characterization of doxazosin as a novel small molecule agonist for EphA2 and EphA4, but not for other Eph receptors tested. NMR studies revealed extensive contacts of doxazosin with EphA2/A4, recapitulating both hydrophobic and electrostatic interactions recently found in the EphA2/ephrin-A1 complex. Clinically used as an α1-adrenoreceptor antagonist (Cardura®) for treating hypertension and benign prostate hyperplasia, doxazosin activated EphA2 independent of α1-adrenoreceptor. Similar to ephrin-A1, doxazosin inhibited Akt and ERK kinase activities in an EphA2-dependent manner. Treatment with doxazosin triggered EphA2 receptor internalization, and suppressed haptotactic and chemotactic migration of prostate cancer, breast cancer, and glioma cells. Moreover, in an orthotopic xenograft model, doxazosin reduced distal metastasis of human prostate cancer cells and prolonged survival in recipient mice. To our knowledge, doxazosin is the first small molecule agonist of a receptor tyrosine kinase that is capable of inhibiting malignant behaviors in vitro and in vivo.
在肿瘤进展过程中，由于 Akt 的激活和 Ephrin-A 配体结合减少，EphA2 受体可获得配体非依赖性的致癌功能。这些作用可以通过配体刺激来逆转，配体刺激会触发 EphA2 的内在肿瘤抑制信号通路，包括抑制 PI3/Akt 和 Ras/ERK 通路。这些观察结果表明，开发 EphA2 的小分子激动剂作为潜在的肿瘤干预剂是可行的。通过虚拟筛选和基于细胞的测定，我们在这里报告了多沙唑嗪被鉴定为 EphA2 和 EphA4 的新型小分子激动剂，而不是为其他测试的 Eph 受体。NMR 研究显示多沙唑嗪与 EphA2/A4 有广泛的接触，再现了最近在 EphA2/ephrin-A1 复合物中发现的疏水性和静电相互作用。多沙唑嗪临床上用作治疗高血压和良性前列腺增生的α1-肾上腺素能受体拮抗剂（Cardura®），可独立于α1-肾上腺素能受体激活 EphA2。与 Ephrin-A1 相似，多沙唑嗪以 EphA2 依赖性方式抑制 Akt 和 ERK 激酶活性。用多沙唑嗪处理会触发 EphA2 受体内化，并抑制前列腺癌、乳腺癌和神经胶质瘤细胞的趋化运动和趋化运动。此外，在原位异种移植模型中，多沙唑嗪减少了人前列腺癌细胞的远端转移，并延长了受体小鼠的存活时间。据我们所知，多沙唑嗪是第一个能够在体外和体内抑制恶性行为的受体酪氨酸激酶的小分子激动剂。
