Biophysics Program, Stanford University, Stanford, CA 94305.
Department of Biology, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2018 May 15;115(20):E4613-E4622. doi: 10.1073/pnas.1801242115. Epub 2018 Apr 27.
Eg5, a mitotic kinesin, has been a target for anticancer drug development. Clinical trials of small-molecule inhibitors of Eg5 have been stymied by the development of resistance, attributable to mitotic rescue by a different endogenous kinesin, KIF15. Compared with Eg5, relatively little is known about the properties of the KIF15 motor. Here, we employed single-molecule optical-trapping techniques to define the KIF15 mechanochemical cycle. We also studied the inhibitory effects of KIF15-IN-1, an uncharacterized, commercially available, small-molecule inhibitor, on KIF15 motility. To explore the complementary behaviors of KIF15 and Eg5, we also scored the effects of small-molecule inhibitors on admixtures of both motors, using both a microtubule (MT)-gliding assay and an assay for cancer cell viability. We found that () KIF15 motility differs significantly from Eg5; () KIF15-IN-1 is a potent inhibitor of KIF15 motility; () MT gliding powered by KIF15 and Eg5 only ceases when both motors are inhibited; and () pairing KIF15-IN-1 with Eg5 inhibitors synergistically reduces cancer cell growth. Taken together, our results lend support to the notion that a combination drug therapy employing both inhibitors may be a viable strategy for overcoming chemotherapeutic resistance.
Eg5 是一种有丝分裂驱动蛋白，一直是抗癌药物开发的目标。由于不同的内源性驱动蛋白 KIF15 介导的有丝分裂拯救，Eg5 的小分子抑制剂的临床试验受到阻碍。与 Eg5 相比，人们对 KIF15 马达的特性了解相对较少。在这里，我们采用单分子光学捕获技术来定义 KIF15 的机械化学循环。我们还研究了 KIF15-IN-1（一种未表征的商业上可用的小分子抑制剂）对 KIF15 运动的抑制作用。为了探索 KIF15 和 Eg5 的互补行为，我们还使用微管（MT）滑行测定法和癌细胞活力测定法来评估小分子抑制剂对两种马达混合物的影响。我们发现：（1）KIF15 的运动行为与 Eg5 有显著差异；（2）KIF15-IN-1 是 KIF15 运动的有效抑制剂；（3）由 KIF15 和 Eg5 驱动的 MT 滑行只有在两个马达都被抑制时才会停止；（4）将 KIF15-IN-1 与 Eg5 抑制剂联合使用可协同降低癌细胞生长。综上所述，我们的研究结果支持了这样一种观点，即联合使用这两种抑制剂的组合药物治疗可能是克服化疗耐药性的可行策略。
