PLK1是保守的丝氨酸/苏氨酸激酶(PLKs)家族成员，在中心体成熟、纺锤体形成、胞浆分离及G2/M 期检测点中起着重要作用。PLK1在肿瘤细胞中呈过表达状态，具有非癌基因成瘾性。我们研究发现：PLK1在肝癌中过表达与血管侵犯及术后生存率相关。我们进一步研究证实:沉默PLK1可抑制肝癌细胞生长、促进凋亡、导致G2/M期捕获，下调Survivin在胞浆及胞核的表达。由此，我们假设PLK1可能通过影响Survivin核浆的表达分布、影响着丝点及纺锤体组装 检测点，导致G2/M期捕获，从而调控肝癌细胞增殖及凋亡。本课题拟采用基因转染、共聚焦显微镜、免疫荧光、免疫共沉淀等研究方法证实这个假设，这将为PLK1小分子抑制剂成为肝癌治疗的新药物提供理论及实验依据。

Polo-like kinase 1 (PLK1) belongs to a family of conserved serine/threonine kinases,involved in multiple mitotic processes, including functional maturation of centrosomes, establishment of the bipolar spindle, the execution of cytokinesis and regulation of the G2/M DNA checkpoint. PLK1 is overexpressed in many cancer cell lines and is also added to a growing list of non-oncogenes addiction for these cancer cell lines. Our previous studies have demonstrated that overexpression of PLK1 is correlated with venous invasion and predicts poor postoperative survival rate in HCC.Our further findings imply that PLK1 depletion led to G2/M arrest,inhibition of cell proliferation and promotion of apoptosis via downregulation of both nuclear and cytoplasmic staining of Survivin. Therefore,we put forward our scientific hypothesis that PLK1 may alter expression distribution of nuclear and cytoplasmic Survivin, affect kinetochore and spindle assembly checkpoint(SAC),and led to G2/M arrest,thereby regulate proliferation and apoptosis of hepatoma cells. In this project, our hypothesis will be verified by advanced molecular biology techniques,such as gene transfection,lsaer scanning confocal microscope,immunofluorescence and co-Immunoprecipitation etc.Our hypothesis will provide theoretical and experimental evidences for PLK1 small molecule inhibitors as new drugs in HCC.

Plk1 是一种在细胞周期调控中起关键作用的蛋白激酶，我们前期研究发现：PLK1在肝癌中过表达，且与肝癌的预后相关。干预PLK1可通过下调survivin抑制肿瘤生长。本项目研究发现:1） miRNA-let7b-3p与PLK1 3-utr存在结合位点，过表达miRNA-let7b-3p能影响PLK1及survivin活性，抑制细胞增殖并导致凋亡，过表达PLK1则可对抗miRNA-let7b-3p作用。此外，miRNA-let7b-3p和PLK1过表达在部分肝癌组织中存在负相关。这些研究结果揭示了miRNA-let7b-3p/PLK1/survivin信号通路在肝癌中发挥重要作用。2）PLK1激酶可能通过转录因子SP1调控survivin 表达。plk1与survivin在部分肝癌组织中存在正相关性；沉默/过表达PLK1可以影响survivin 表达。SP1参与了PLK1介导的survivin 转录激活，且PLK1可以磷酸化SP1。这些研究结果揭示了/PLK1/SP1/survivin信号通路在肝癌发病机制中发挥重要作用。这些为探索Plk1在肝癌的药物治疗靶点提供思路。