Materials
Antibodies recognizing YAP1, phospho-YAP1 (Ser-127 p-YAP1)(Cell Signaling Technology, Beverly, MA, USA), matrix metalloproteinase2 (MMP2), slug, twist, vimentin, AR, NK3 Homeobox 1 (NKX3.1), Myc, connective tissue growth factor (CTGF, Santa Cruz Biotechnology, Santa Cruz, CA, USA), E-cadherin, N-cadherin (BD Biosciences, San Jose, CA, USA), phospho-AR (ser-81 p-AR)(Milipore, Billerica, MA, USA), and ß-actin (Sigma-Aldrich, St. Louis, MO, USA) were used for immunoblottings. Horseradish peroxidase (HRP)-conjugated donkey anti-rabbit and anti-mouse IgGs were obtained from Cell Signaling Technology. GV1001 peptide was supplied by GemVax & KAEL (Seongnam, Kyeonggi-do, South Korea). Leuprolide acetate (LA) and cetrorelix acetate (CA) were synthesized by AnyGen (Gwangju, South Korea). KT5720 (Cat# K3761), forskolin (Cat# F6886), dihydrotestosterone (Cat# A8380), flutamide (Cat# F9397), pertussis toxin (Cat# P2980) and SQ22536 (Cat# S153) were purchased from Sigma-Aldrich (St. Louis, MO, USA). KH7 (Cat# 13243, Cayman Chemical, Ann Arbor, MI, USA) and 1,2-Bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid tetrakis(acetoxymethyl ester, BAPTA/AM)(Biovision, Mountain View, CA, USA) were used as signaling inhibitors for Gα-proteins.
Cell culture and establishment of stably GnRHR-overexpressing HEK293 cells
LNCaP (androgen receptor positive human PCa cell line) cells were cultured in RPMI-1640 medium with 10% fetal bovine serum (Hyclone, Logan, UT, USA) and 1% penicillin/streptomycin (100 U/ml, Hyclone). YAP1 knockout LNCaP cells were established by CRISPR/Cas9 gene editing system. U6-YAP1/Cas9-2A-RFP plasmid or CRISPR Universal Negative Control plasmid were transfected with LNCaP cells and the red fluorescence protein (RFP)-positive cells were further sorted by FACS Aria II flow cytometer (BD Biosciences, San Jose, CA, USA). HEK293 cells were cultured in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum and 1% penicillin/streptomycin. All cultures were maintained in a humidified 5% CO2 environment at 37°C. To obtain GnRHR-overexpressing HEK293 (HEK293-GnRHR) cells, transfection of pcDNA3.1(+)-GnRHR vector was performed by using Lipofectamine 2000 as specified by the manufacturer's instruction (Invitrogen, Carlsbad, CA, USA). Geneticin-resistant colonies were selected by G418 (800 µg/ml, Thermo Fisher Scientific, Waltham, MA, USA) treatment. HEK293-pcDNA3.1(+) vector was also used as mock-transfection group.
Establishment of AR and YAP1 knockout cells
AR or YAP1 knockout LNCaP cells were established by using U6-AR/Cas9-2A-RFP plasmid, U6-YAP1/Cas9-2A-RFP plasmid or CRISPR Universal Negative Control plasmid (Sigma-Aldrich). For the selection of RFP-positive-knockout cells, the transfected LNCaP cells were sorted using BD FACS Aria II flow cytometer (BD Biosciences, San Jose, CA, USA).
Western blot analysis
After washing with PBS, cells were lysed with lysis buffer containing 20 mM Tris-Cl (pH 7.5), 1% Triton X-100, 137 mM sodium chloride, 10% glycerol, 2 mM EDTA, 1 mM sodium orthovanadate, 25 mM ß-glycerophosphate, 2 mM sodium pyrophosphate, 1 mM phenylmethylsulfonylfluoride and 1 µg/ml leupeptin. The cell lysates were centrifuged at 13,000×g for 15 min to remove insoluble material, the supernatants were fractionated using 10, 12 or 15% separating polyacrylamide gel, and electrophoretically transferred to nitrocellulose membranes, which were incubated overnight at 4°C with one of the primary antibodies. HRP-conjugated anti-IgG antibodies were used as the secondary antibodies. The nitrocellulose papers were developed using an ECL chemiluminescence system (Milipore, Billerica, MA, USA). For ECL chemiluminescence detection, LAS-3000 mini system (Fujifilm, Tokyo, Japan) was used.
Reporter gene assay
LNCaP, HEK293-pcDNA3.1(+) and HEK293-GnRHR cells (1×105 cells/well) were cultured in 48-well plates, then transfected with luciferase reporter plasmid containing cAMP response element (CRE). LNCaP cells cultured in 48-well plate were transfected with androgen response element (ARE). In order to evaluate the transcriptional activity of YAP1, YAP1 knockout- and wildtype-LNCaP cells were cultured in 48-well plates and transfected with YAP/TAZ-responsive luciferase reporter plasmid (TEAD reporter). The transfected cells were exposed to compounds for 24 h, and the promoter activity was measured using a dual-luciferase reporter assay system (Promega, Madison, WI, USA). The firefly and hRenilla luciferase activities in the cell lysates were measured using a luminometer (LB960, Berthold Technologies, Bad Wildbad, Germany). The relative luciferase activities were calculated by normalizing the promoter-driven firefly luciferase activity to phRL-SV (hRenilla) luciferase.
Transwell migration assay
LNCaP cells were seeded in the upper chamber of the transwell plate (Essen BioScience, Ann Arbor, MI, USA) and the lower chamber was filled with 200 µl serum-containing media. The cells were incubated at 37ºC for 24 h and the migrated cell numbers were counted using IncuCyte ZOOM live-cell analysis system (Essen BioScience, Ann Arbor, MI, USA).
Immunocytochemistry
LNCaP cells were cultured overnight on coverslips. After treatment with 10 µM GV1001 or vehicle, the cells were fixed with 4% paraformaldehyde and blocked with 1% bovine serum albumin at room temperature for 1 h. The cells were incubated with rabbit monoclonal YAP/TAZ or phospho-YAP antibody (1:200 dilution) in 0.1% Tween20-containing PBS at 4ºC overnight. After twice washing with PBS, the coverslips were incubated with goat anti-rabbit Alexa Fluor-488 or -568 IgG (1:2000 dilution, Thermo Fisher Scientific, Waltham, MA, USA) at room temperature with ProLong Gold Antifade reagent with 4’,6-diamidino-2-phenylindole (DAPI, Invitrogen, Carlsbad, CA, USA). Images were obtained using SP8-STED Confocal Microscope System (Leica Microsystems, Heidelberg, Germany).
Quantitative reverse transcription-polymerase chain reaction (qRT-PCR)
Total RNA was isolated from LNCaP cells using Trizol® reagent (Invitrogen, Carlsbad, CA, USA), and cDNA was synthesized by reverse transcriptase using an oligo(dT) primer. PCR was performed using the selective primers for human MMP2 (sense: 5’-CTTCCAAGTCTGGAGCGATGTG-3’, antisense: 5’-ATGAGCCAGGAGTCCGTCCTTA-3’), human AR (sense: 5’-AGGATGCTCTACTTCGCCCC-3’, antisense: 5’-ACTGGCTGTACATCCGGGAC-3’), human prostate specific antigen (PSA, sense: 5’-ACCAGAGGAGTTCTTGACCCCAAA-3’, antisense: 5’-CCCCAGAATCACCCGAGCAG-3’), human CTGF (sense: 5’-CAAGGGCCTCTTCTGTGACT-3’, antisense: 5’-ACGTGCACTGGTACTTGCAG-3’), human NKX3.1 (sense: 5’-GCCGCACGAGCAGCCAGAGACA-3’, antisense: 5’-TTCAGGGCCGGCAAAGAGGAGTG-3’), human GAPDH (sense: 5’-AAGGCTGAGAACGGGAAG-3’, antisense: 5’-GCCCCACTTGATTTTGGA-3’). The SYBR Green real-time PCR amplifications were conducted with MiniOpticon real time PCR detection system (Bio-Rad laboratories Inc., Hercules, CA, USA).
Chromatin immunoprecipitation (ChIP) assay
ChIP assays were performed according to the EZ-ChIP kit (Milipore, Bedford, MA, USA). An anti-AR antibody (Cat# sc-819, Santa Cruz Biotechnology, Santa Cruz, CA, USA) was used to precipitate DNA-protein complexes. ChIP-derived DNA was quantified using qRT-PCR with SYBR Green real-time PCR Mastermix (Bio-Rad laboratories Inc., Hercules, CA, USA). The primers specific for the promoters were as follows: human PSA (sense: 5’-GCTAGCACTTGCTGTTCTGC-3’, antisense: 5’-GGGATCAGGGAGTCTCACAA-3’), human CTGF (sense: 5’-TGTGCCAGCTTTTTCAGACG-3’, antisense: 5’-TGAGCTGAATGGAGTCCTACACA-3’) and human NKX3.1 (sense: 5’-CCGAGCCAGAAAGGCACTTG-3’, antisense: 5’-CTTAGGGGTTTGGGGAAGCC-3’).
Spleen-liver metastasis
5-week-old male BALB/c-nu mice (Jung Ang Lab Animal Inc., Seoul, South Korea) were anaesthetized and an abdominal incision was made in the left flank and the spleen was isolated. 1×105 LNCaP cells in 100 µl PBS were injected into the spleen with a 26-gauge needle, and the incision was closed with stitches. After 3 days, mice were divided into three groups: vehicle, GV1001 (10 mg/kg, daily, sc) and LA (0.1 mg/kg, daily, sc) treatment groups. After 4 weeks, the mice were sacrificed and the liver and spleen samples were analyzed by hematoxylin & eosin (H&E) staining. For pathological assessment, specimens were cut into 2 mm thick sections after formalin fixation. All abnormal regions (nodules or suspicious regions) were observed under a microscope, and the absolute metastatic tumor area was analyzed. Basically all abnormal regions were analyzed (3–4 slides per liver tissue) when nodules are found.
Protein-protein interaction (PPI) network
The STRING database (http://string-db.org/)(26) was used to analyze the protein-protein interactions. The STRING database was applied to predict the PPIs by DEGs, and the parameter of combined score > 0.4 was set as the threshold value for choosing significant interactions. The nodes in the PPI network were ranked by their connectivity degrees, which correspond to the number of interactions by other proteins.
Statistics
Statistical analysis was performed using one-way ANOVA and Tukey’s post hoc multiple comparisons to determine the differences. The statistical significance was accepted at *P < 0.05 and **P < 0.01.