State Key Laboratory of Oncogenes and Related Genes, Renji-MedX Clinical Stem Cell Research Center, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 160 Pujian Road, Shanghai, 200127, China.
Department of Urology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, China.
J Exp Clin Cancer Res. 2017 Oct 10;36(1):139. doi: 10.1186/s13046-017-0609-y.
Prostate cancer (PCa) is one of the most frequent tumors and leading cause of cancer deaths among males worldwide. The majority of deaths are due to recurrence and subsequent development of the metastatic cancer. Although loss or dislocalization of polarity proteins has been implicated in embryogenesis deficiency and tumorigenesis, association of polarity protein expression levels with tumor metastasis remains unclear.
Bioinformatics, qRT-PCR, western blot and immunohistochemical (IHC) analyses were used to examine expression of Par3, a key component of polarity-associated partitioning defective (PAR) complex, in primary and metastatic clinical PCa samples. Loss-of-function and gain-of-function studies in vitro and in vivo were performed to determine the functions of Par3 during metastasis of PCa. Co-immunoprecipitation (co-IP), western blot, immunofluorescence (IF), chromatin immunoprecipitation (ChIP) and qRT-PCR analyses were conducted to investigate the underlying mechanism for the function of Par3 on PCa metastasis.
In this study, we found that elevated expression of Par3 is positively associated with PCa metastasis. Knockdown of Par3 inhibits PCa cell migration and invasion in vitro and tumor metastasis in vivo, whereas overexpression of Par3 yields the opposite results. Mechanistically, Par3 suppresses phosphorylation of LATS to inactivate the Hippo pathway and enhances nuclear translocation of YAP by sequestrating KIBRA from the KIBRA/Merlin/FRMD6 complex and forming a Par3/aPKC/KIBRA complex. Stable knockdown of Par3 leads to restoration of the KIBRA/Merlin/FRMD6 complex and activation of the Hippo pathway, and then results in an inhibition on YAP nuclear translocation. In addition, in conjunction with the TEA domain (TEAD) transcription factor family, intranuclear YAP promotes the transcription of several pro-metastatic genes such as the matrix metalloproteinase (MMP) family, Zeb1, Snail1 and Twist1. Moreover, knockdown of Par3 downregulates expression of these pro-metastatic genes.
Our findings indicate that elevated expression of Par3 promotes PCa metastasis via KIBRA sequestration-mediated inactivation of the Hippo pathway to upregulate expression of pro-metastatic genes. Downregulation of Par3 expression may serve as a potential treatment approach for PCa metastasis by activating the Hippo pathway.
前列腺癌（PCa）是全球男性中最常见的肿瘤之一，也是癌症死亡的主要原因。大多数死亡是由于复发和随后发生转移性癌症。尽管极性蛋白的缺失或定位异常与胚胎发生缺陷和肿瘤发生有关，但极性蛋白表达水平与肿瘤转移的关系尚不清楚。
采用生物信息学、qRT-PCR、western blot 和免疫组化（IHC）分析方法，检测极性相关分区缺陷（PAR）复合物关键组成部分 Par3 在原发性和转移性临床 PCa 样本中的表达。在体外和体内进行 Par3 的功能丧失和功能获得研究，以确定其在 PCa 转移过程中的功能。通过共免疫沉淀（co-IP）、western blot、免疫荧光（IF）、染色质免疫沉淀（ChIP）和 qRT-PCR 分析，研究 Par3 对 PCa 转移功能的潜在机制。
在这项研究中，我们发现 Par3 的高表达与 PCa 转移呈正相关。Par3 的敲低抑制了 PCa 细胞的迁移和侵袭体外和体内肿瘤转移，而 Par3 的过表达则产生相反的结果。机制上，Par3 抑制 LATS 的磷酸化，从而使 Hippo 通路失活，并通过将 KIBRA 从 KIBRA/Merlin/FRMD6 复合物中隔离出来，与 aPKC/KIBRA 复合物形成复合物，增强 YAP 的核转位。稳定敲低 Par3 导致 KIBRA/Merlin/FRMD6 复合物的恢复和 Hippo 通路的激活，然后导致 YAP 核转位的抑制。此外，与 TEA 结构域（TEAD）转录因子家族一起，核内 YAP 促进了基质金属蛋白酶（MMP）家族、Zeb1、Snail1 和 Twist1 等几个促转移基因的转录。此外，Par3 的敲低下调了这些促转移基因的表达。
我们的研究结果表明，Par3 的高表达通过 KIBRA 隔离介导的 Hippo 通路失活促进 PCa 转移，从而上调促转移基因的表达。下调 Par3 的表达可能通过激活 Hippo 通路成为治疗 PCa 转移的潜在方法。
