LeRoy Patrick J, Hunter John J, Hoar Kara M, Burke Krissy E, Shinde Vaishali, Ruan Jason, Bowman Douglas, Galvin Katherine, Ecsedy Jeffrey A
Department of Molecular, Millennium Pharmaceuticals, Cambridge, Massachusetts 02139, USA.
Cancer Res. 2007 Jun 1;67(11):5362-70. doi: 10.1158/0008-5472.CAN-07-0122.
Aurora A is a serine/threonine protein kinase essential for normal mitotic progression. Aberrant increased expression of Aurora A, which occurs frequently in human cancers, results in abnormal mitoses leading to chromosome instability and possibly tumorigenesis. Consequently, Aurora A has received considerable attention as a potential target for anticancer therapeutic intervention. Aurora A coordinates several essential mitotic activities through phosphorylation of a variety of proteins, including TACC3, which modulates microtubule stabilization of the mitotic spindle. Recent studies identified a conserved serine in Xenopus (Ser(626)) and Drosophila (Ser(863)) TACC3 orthologues that is phosphorylated by Aurora A. We show that this conserved serine on human TACC3 (Ser(558)) is also phosphorylated by Aurora A. Moreover, phosphorylation of TACC3 by Aurora A in human cells is essential for its proper localization to centrosomes and proximal mitotic spindles. Inhibition of Aurora A with the selective small molecule inhibitor MLN8054 in cultured human tumor cells resulted in mislocalization of TACC3 away from mitotic spindles in a concentration-dependent manner. Furthermore, oral administration of MLN8054 to nude mice bearing HCT-116 human tumor xenografts caused a dose-dependent mislocalization of TACC3 away from spindle poles that correlated with tumor growth inhibition. As TACC3 localization to mitotic spindles depends on Aurora A-mediated phosphorylation, quantifying TACC3 mislocalization represents a novel pharmacodynamic approach for measuring Aurora A activity in cancer patients treated with inhibitors of Aurora A kinase.
极光激酶A是一种丝氨酸/苏氨酸蛋白激酶，对正常的有丝分裂进程至关重要。极光激酶A在人类癌症中经常异常高表达，导致有丝分裂异常，进而引起染色体不稳定并可能引发肿瘤发生。因此，极光激酶A作为抗癌治疗干预的潜在靶点受到了广泛关注。极光激酶A通过磷酸化多种蛋白质来协调多种重要的有丝分裂活动，其中包括TACC3，它可调节有丝分裂纺锤体的微管稳定性。最近的研究在非洲爪蟾（Ser(626)）和果蝇（Ser(863)）的TACC3同源物中鉴定出一个保守的丝氨酸，该丝氨酸可被极光激酶A磷酸化。我们发现人类TACC3上的这个保守丝氨酸（Ser(558)）也能被极光激酶A磷酸化。此外，在人类细胞中，极光激酶A对TACC3的磷酸化对于其正确定位于中心体和近端有丝分裂纺锤体至关重要。在培养的人类肿瘤细胞中，用选择性小分子抑制剂MLN8054抑制极光激酶A会导致TACC3以浓度依赖的方式从有丝分裂纺锤体上错误定位。此外，给携带HCT - 116人肿瘤异种移植瘤的裸鼠口服MLN8054会导致TACC3从纺锤极错误定位，且呈剂量依赖性，这与肿瘤生长抑制相关。由于TACC3定位于有丝分裂纺锤体依赖于极光激酶A介导的磷酸化，因此量化TACC3的错误定位代表了一种新的药效学方法，用于测量接受极光激酶A抑制剂治疗的癌症患者体内极光激酶A的活性。
