Background Prostate cancer (PCa) is one of the most frequent tumors and leading cause of cancer deaths among males worldwide. investigate the underlying mechanism for the function of Par3 on PCa metastasis. Results 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. Conclusions Our findings indicate that elevated expression of Par3 promotes Mouse monoclonal to ATM 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. Electronic supplementary material The online version of this article (10.1186/s13046-017-0609-y) contains supplementary material, which is available buy Methyl Hesperidin to authorized users. can act as either an activator or inhibitor of the Hippo-YAP pathway, whether there are other possible upstream regulators for this pathway in the mammalian cells, especially in human cancer cells are not determined. In this study, we aimed to determine possible roles of Par3 in prostate cancer metastasis. We found that enhanced expression of Par3 in the tissues from PCa patients as well as PCa cell lines is positively associated with tumor metastasis. We also obtained evidence suggesting that Par3 acts as a potential upstream regulator of the Hippo-YAP pathway via sequestration of KIBRA, a reported activator of Hippo pathway , from canonical KIBRA/Merlin/FRMD6 complex  and formation of a Par3/aPKC/KIBRA complex to suppress phosphorylation of the Hippo pathway and YAP. Finally, by increasing nuclear translocation of buy Methyl Hesperidin non-phosphorylated YAP and activation of TEAD transcription factors, the transcription of pro-metastasis genes is enhanced, which promotes the PCa metastasis. Thus, repression of Par3 may offer a potential treatment approach to inhibit PCa metastasis by activating the Hippo pathway. Methods Cell lines and cell culture buy Methyl Hesperidin Prostate cancer cell lines PC3, DU145 and normal prostate epithelial cell line PNT1B were purchased from the American Type Culture Collection (ATCC, Rockville, MD, USA). Cells were cultured in Dulbeccos modified Eagles medium (DMEM, Gibco, Thermo Fisher Scientific, Waltham, MA, USA) with 10% fetal bovine serum (FBS, Gibco) and maintained at 5% CO2 buy Methyl Hesperidin at 37?C. Cell transfection and lentiviral vector infection The Par3 knock down and control plasmids were obtained from Origene (Rockville, MD, USA). Plasmids were transfected with Lipofectamine3000 (Thermo Fisher Scientific). Puromycin (0.5?g/ml) was used for selecting stable Par3 knockdown and relevant control subclones, which were named as PC3-shPar3, PC3-con, DU145-shPar3 and DU145-con respectively. The lentiviral vector expressing one of the Par3 isoforms (“type”:”entrez-nucleotide”,”attrs”:”text”:”NM_019619.3″,”term_id”:”296278254″,”term_text”:”NM_019619.3″NM_019619.3, 150?kDa) or a non-phosphorylatable YAP mutant, YAP(S127A); and control lentiviral vector were constructed and packaged by Genomeditech Comp (Shanghai, China). 2??106 cells were seeded in 6-well plates and infected using relevant lentiviral vector (MOI?=?10 for each) concomitant with 5?g/ml polybrene. Western blot was employed to detect Par3 expression levels. IF was employed to detect YAP subcellular location. MOI: multiplicity of infection. In vitro migration and invasion assay In vitro migration and invasion assays were performed using 24-well Cell Migration and Invasion Assay kit (Cell BioLabs, San Diego, CA, USA), according to the manufacturers instructions. Briefly, after serum starvation for 24?h, 1??105 cells were suspended in 100?l.