文章长,可以给发过去,帮我翻译这一部分也好。图片接下文,先谢了。周三要交。
Polo-like kinase 1 (Plk1) is an important target for antineoplastic therapy because of its required functions in cell division, as well as the enhanced sensitivity of cancer cells to its inactivation. Several Plk1-targeted drugs have emerged, including BI-2536 and ZK-thiazolidinone (TAL). These inhibitors of Plk1 arrest cells in mitosis and evoke phenotypes consistent with downregulating Plk1 by other means.BI-2536 and a pharmacologically optimized analogue (BI-6727) have shown promising signs of activity in preliminary clinical trials. A chemical genetic system for inhibiting Plk1 has also been developed. In this system, both copies of the PLK1 locus were deleted from immortalized human retinal pigment epithelial cells through targeting and Cre-lox-mediated recombination. After Cre-mediated excision, PLK1–/– clones are inviable unless they are complemented by expression of Plk1 in trans, either wildtype (Plk1wt) or a compound mutant (L130G C67V; hereafter Plk1as). By enlarging the kinase’s active site, the latter mutations allow Plk1 to accept bulky purine analogues as ATP-competitive inhibitors. We report here that these mutations also have the unexpected effect of desensitizing Plk1 to clinically useful inhibitors such as BI-2536 and TAL. (Structures for all chemicals used are shown in Supplementary Figure 1.)
In the course of examining the anti-proliferative activity of BI-2536, we discovered that this compound strongly retarded the growth of Plk1wt cells but had little or no effect on Plk1as cells (Figure 1A,B). To determine if this change in inhibitor potency was unique to BI-2536, we performed similar growth-challenge experiments with TAL, a structurally distinct Plk1 inhibitor. Again, we observed a marked difference between Plk1as cells and their isogenic Plk1wt counterparts (Figure 1C,D). To understand the depth and breadth of inhibitor resistance, we queried multiple in vivo readouts of Plk1 activity. Plk1 is required throughout mitosis, with well-characterized roles in centrosome maturation, bipolar spindle assembly, stabilization of kinetochore-microtubule attachments, and initiation of cytokinesis. Each of these programs proved to be qualitatively and quantitatively resistant to both Plk1-targeted inhibitors. For instance, Plk1as cells continued to recruit γ-tubulin to centrosomes (a cardinal manifestation of centrosome maturation) and form bipolar spindles in the presence of BI-2536 (Figure 2A) and TAL (Figure 2B). Likewise, BubR1 hyper-phosphorylation by Plk1 (a crucial determinant of stable kinetochore-microtubule attachment) was undiminished, as reflected in the BubR1 polypeptide’s persistent mobility shift on SDS-PAGE (Figure 2C). Consistent with this broad array of defects, both compounds caused Plk1wt (but not Plk1as cells) to arrest in mitosis, as judged from their rounded appearance by phase-contrast microscopy (shown below in Figure 4).