A Novel Function of YWHAZ/B-Catenin Axis in Promoting Epithelial–Mesenchymal Transition and Lung Cancer Metastasis

Published OnlineFirst August 21, 2012; DOI: 10.1158/1541-7786.MCR-12-0189

Molecular Cancer Angiogenesis, Metastasis, and the Cellular Microenvironment Research

A Novel Function of YWHAZ/b-Catenin Axis in Promoting Epithelial–Mesenchymal Transition and Lung Cancer Metastasis

Ching-Hsien Chen1,4, Show-Mei Chuang1, Meng-Fang Yang1, Jiunn-Wang Liao2, Sung-Liang Yu4, and Jeremy J.W. Chen1,3

Abstract YWHAZ, also known as 14-3-3zeta, has been reportedly elevated in many human tumors, including non–small cell lung carcinoma (NSCLC) but little is known about its specific contribution to lung cancer malignancy. Through a combined array-based comparative genomic hybridization and expression microarray analysis, we identified YWHAZ as a potential metastasis enhancer in lung cancer. Ectopic expression of YWHAZ on low invasive cancer cells showed enhanced cell invasion, migration in vitro, and both the tumorigenic and metastatic potentials in vivo. Gene array analysis has indicated these changes associated with an elevation of pathways relevant to epithelial–mesenchymal transition (EMT), with an increase of cell protrusions and branchings. Conversely, knockdown of YWHAZ levels with siRNA or short hairpin RNA (shRNA) in invasive cancer cells led to a reversal of EMT. We observed that high levels of YWHAZ protein are capable of activating b-catenin–mediated transcription by facilitating the accumulation of b-catenin in cytosol and nucleus. Coimmunoprecipitation assays showed a decrease of ubiquitinated b-catenin in presence of the interaction between YWHAZ and b-catenin. This interaction resulted in disassociating b-catenin from the binding of b-TrCP leading to increase b-catenin stability. Using enforced expression of dominant-negative and -positive b-catenin mutants, we confirmed that S552 phosphorylation of b-catenin increases the b-catenin/YWHAZ complex formation, which is important in promoting cell invasiveness and the suppression of ubiquitnated b-catenin. This is the first demonstration showing YWHAZ through its complex with b-catenin in mediating lung cancer malignancy and b-catenin protein stability. Mol Cancer Res; 10(10); 1319–31. 2012 AACR.

Introduction by undergoing phenotypic conversion referred to as epithe- – Lung cancer is a malignant tumor with a high incidence lial mesenchymal transition (EMT), which enables them and mortality rate (1). Non–small cell lung cancer (NSCLC) to become motile and to invade adjacent tissues. This process represents 80% of all lung cancers and has an overall 5-year is triggered by various signaling pathways and controlled by a group of transcriptional factors, such as zinc finger survival rate of 10% to 15% (2). Metastasis is the main cause – – of treatment failure and cancer-related deaths. In carcino- proteins and basic helix loop helix factors (4, 5). In lung mas, metastasis is a multiple step process, the first of which cancer, Slug is known to be an important EMT inducer and is invasion (3). Cancer cells acquire their invasive capacity is able to suppress the expression levels of cell adhesion molecules (6–8). b-Catenin binds to the cytoplasmic domain of E-cadherin Authors' Affiliations: Institutes of 1Biomedical Sciences, and 2Veterinary and is essential for the structural organization and function of Pathology and 3Agricultural Biotechnology Center, National Chung Hsing cadherins. b-Catenin also plays a central role as a cotran- University, Taichung; and 4Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, scription factor in both canonical and noncanonical Wnt Taipei, Taiwan, Republic of China signaling (9). In the absence of Wnt signaling, the soluble b Note: Supplementary data for this article are available at Molecular Cancer form of -catenin, which is not associated with cadherins, is Research Online (http://mcr.aacrjournals.org/). phosphorylated by glycogen synthase kinase-3b (10) and is subsequently recognized by the b-transducin repeat-con- S.-L. Yu and J.J.W. Chen codirected the project and contributed equally to b this work. taining protein ( -TrCP), leading to the ubiquitination and degradation of b-catenin by proteasomes (11). Activation of Corresponding Author: Jeremy J.W. Chen, Institute of Biomedical b Sciences, National Chung Hsing University, Taichung 40227, Taiwan, the Wnt pathway inhibits the degradation of -catenin and ROC. Phone: 886-4-22840896, ext. 125; Fax: 886-4-22853469; E-mail: results in its accumulation in the cytosol and subsequent [email protected] nuclear translocation (12). Following nuclear translocation, doi: 10.1158/1541-7786.MCR-12-0189 b-catenin interacts with the transcription factor T-cell fac- 2012 American Association for Cancer Research. tor/lymphoid enhancer factor (TCF/LEF) to induce the

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transactivation of certain vital genes, including cyclin D1, shYWHAZ-1 and pLKO.1-shYWHAZ-2; TRCN- c-Myc, and Slug (13–15). Although excess b-catenin pro- 0000029404 and TRCN0000029405) were obtained from teins are observed in certain cancers and associated with the National RNAi Core Facility (Academia Sinica, Taipei, dysregulation of ubiquitination, the molecules involved in Taiwan) and prepared in accordance with the standard b-catenin accumulation are largely unknown. protocols. Cells were infected with lentivirus (multiplicity In this study, we identify YWHAZ, also known as 14-3- of infection 5 or 10) in medium containing polybrene 3zeta, as a potential regulator for the function of b-catenin (8 mg/mL). At 24 hours after infection, cells were treated and its turnover. YWHAZ was initially identified as one with 0.75 mg/mL puromycin to select for puromycin-resis- of the metastasis enhancer genes through an integrated tant pooled clones. approach that combined comparative genome hybridization (CGH) with an expression microarray on lung cancer cell Microarray analysis lines with different metastatic potentials (16). YWHAZ Human genomic DNAs from CL1-5 and CL1-0 cells has attracted interest because of its elevated expression asso- were analyzed using array CGH containing 385,000 probes ciated with a variety of cancers (17–24). Recently, it is with a median distance of approximately 6,000 bp (Nim- understood that YWHAZ has critical antiapoptotic func- bleGen) to determine copy number variations in dye-swap tions and is able to suppress anoikis in lung cancer replicate experiments. For expression analysis, cDNA prep- (17, 18, 25). In this communication, we report for the first aration and array hybridization were conducted according to time that YWHAZ amplification is associated with lung the Affymetrix GeneChip expression analysis technical man- cancer malignancy and the importance of YWHAZ/b-cate- ual (see Supplementary Methods). nin axis in preventing b-catenin ubiquitination and degradation and subsequently in promoting EMT phenotype Quantitative real-time PCR and invasiveness of cancer cells. The DNA copy number of YWHAZ was detected by real- time PCR on the Prism 7900 Sequence Detection System (Applied Biosystems), according to the manufacturer's in- Materials and Methods structions. The mRNA expression level of YWHAZ and Materials and plasmid constructs CTNNB1 (b-catenin) was also detected by real-time reverse All reagents, antibodies, and plasmid constructs used in transcription polymerase chain reaction (RT-PCR) on this study are described in the Supplementary Information the same system. The primers and probes of YWHAZ in Supplementary Methods. (Hs00237047_m1) and TATA-box binding protein (TBP, Hs00427620_m1) were purchased from Applied Biosystems. Cell culture and transfection The CTNNB1 primers were as follows: forward primer 50-GGCTACTGTTGGATTGATTCGAA-30 and reverse The low invasive and highly invasive human lung adeno- 0 0 carcinoma cell lines, CL1-0 and CL1-5, were established and primer 5 -GCTGGGTATCCTGATGTGCAC-3 .Weused characterized as previously described (16). We tested their the housekeeping gene ACTB as the reference gene in genomic invasiveness for authentication by Matrigel invasion assays real-time PCR assay. The DNA copy number of YWHAZ in our laboratory every month. The cell lines, HEK293, for tumor or normal tissue was presented as relative level to A549, H1299, MCF-7, HeLa, and BEAS2B cells were reference gene. For mRNA analysis, we used TBP as the purchased from the American Type Culture Collection internal control. The relative expression level of YWHAZ (ATCC) that conducts cell line characterizations and pas- and CTNNB1 compared with that of TBP was defined as D ¼½ saged in our laboratory for fewer than 6 months after CT CTtarget CTTBP . The target/TBP mRNA ratio D receipt. The method of characterization used by ATCC can was calculated as 2 CT K,inwhichK is a constant. be found in its website. Cells were cultured in Dulbecco's modified Eagle's medium with 10% FBS and 1% penicillin– Migration and invasion assays streptomycin at 37 C in a humidified atmosphere of 5% In vitro cell migration and invasion assays were conducted CO2. For enforced expression of V5-tagged YWHAZ in the as previously described (26) using transwell chambers (8 mm minimally invasive lung cancer cell line, CL1-0 cells were pore size; Costar). In migration assays, 5 103 cells were transfected with pEF6/V5-HisTOPO-YWHAZ (pEF6/V5- seeded on top of the polycarbonate filters and incubated for YWHAZ) or pEF6/V5-HisTOPO vector using lipofect- 12 hours. Filters were swabbed with a cotton swab, fixed amine reagent, according to the manufacturer's protocol. with methanol, and then stained with Giemza solution After culturing in medium containing 10 mg/mL of blasti- (Sigma). For the invasion assays, filters were coated with cidine for 2 to 3 weeks, individual clones were isolated. Matrigel (Becton Dickinson), and 2 104 cells were seeded Clones that expressed the YWHAZ cDNA coding region onto the Matrigel and incubated for 20 hours. The cells were maintained in medium containing 5 mg/mL of blasti- attached to the lower surface of the filter were counted under cidine and used for further investigation. a light microscope ( 100 magnification).

Lentiviral shRNA–mediated knockdown In vivo tumorigenesis and metastasis Luciferase (pLKO.1-shLuc; TRCN00000072244) and Six-week-old nonobese diabetic (NOD) severe com- 2 YWHAZ-shRNA–containing lentiviral vectors (pLKO.1 bined immunodeﬁciency (SCID) mice (supplied by the

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YWHAZ/b-Catenin Axis in Lung Cancer Metastasis

animal center of the College of Medicine, National Results Taiwan University, Taipei, Taiwan) were housed 4 mice ad libitum YWHAZ expression enhances lung cancer cell invasion per cage and fed autoclaved food .Detailed and migration in vitro information on subcutaneous implantation, intravenous To identify metastasis-promoting genes caused by geno- tail injection, and orthotopic implantation of tumors are mic amplification, array CGH and an expression microarray included in the Supplemental Methods. Mouse experi- were used to study a lung cancer invasion model. Genes with ments were approved by the Institutional Animal Care fi > an ampli ed copy number (log2 0.3) and upregulated and Use Committee of National Chung Hsing University expression (>5-fold) in the highly invasive cell line, CL1-5, (Taichung, Taiwan). were selected for further analysis and compared with the corresponding genes in a less invasive cell line, CL1-0. Of the Immunoprecipitation and immunoblotting genes identified, YWHAZ is known to have oncogenic effects The preparation of whole-cell lysates, cytoplasmic and in various types of cancers (28). The gene copy number, nuclear extracts, and Western blot analysis was described transcript expression, and protein expression of YWHAZ previously (27). Cells were lysed in lysis buffer (50 mmol/L in both the CL1-0 and CL1-5 cell lines were consistent with Tris/HCl (pH 7.4), 1% Triton-X 100, 10% glycerol, the results obtained from array CGH and microarray 150 mmol/L NaCl, 1 mmol/L EDTA, 20 mg/mL leupeptin, m m approaches (Fig. 1A). We further examined the expression 1 mmol/L PMSF, 20 g/mL aprotinin, and 20 g/mL of YWHAZ in various cell lines, and Western blot analysis pepstatin) and cleaned by preincubation with protein fi showed that YWHAZ was widely expressed in different A-Sepharose beads to remove nonspeci cally bound pro- tumor types, such as lung, breast, and cervical cancer cells teins. After precipitation with appropriate antibodies and (Supplementary Fig. S1A); however, its expression was protein A-Sepharose beads, the immunoprecipitated com- relatively low in the nonmalignant human epithelial cell plexes were washed and separated by SDS-PAGE. Immu- lines, BEAS2B and HEK293. Ectopic expression of V5- noblotting was done with appropriate antibodies using the tagged YWHAZ in the low invasive cell line, CL1-0 (Sup- Amersham Biosciences Enhanced Chemiluminescence Sys- plementary Fig. S1B), showed higher cell proliferation and tem for detection. enhanced anchorage-dependent and -independent growth as compared with the mock control cells (Supplementary Immunofluorescent staining in vitro fi Fig. S1C and S1D). Furthermore, cell invasiveness Cells cultured on 12 mm glass cover-slips were xed (Fig. 1B) and migration (Fig. 1C) were all increased by 2.4- for 15 minutes in PBS containing 4% paraformaldehyde and 2.5-fold in these cells stably transfected with V5-tagged and 2% sucrose and then permeabilized in PBS contain- YWHAZ construct. These results suggest oncogenic nature ing 0.3% Triton X-100 for 2 minutes. Cover-slips were b of YWHAZ in mediating lung cancer cell metastatic poten- reacted with primary antibody against -catenin and tial in vitro. fluorescein isothiocynate (FITC)-labeled antimouse sec- ondary antibody. F-actin was stained with tetramethyl rhodamine isothiocyanate (TRITC)-conjugated phalloi- YWHAZ expression promotes lung cancer malignancy din, and nuclei were demarcated with 40,6-diamidino-2- in vivo phenylindole (DAPI) staining. The cells were mounted To determine whether YWHAZ possesses oncogenic onto slides and visualized using fluorescence microscopy activities in vivo, 3 approaches were carried out. Cells from (model Axiovert 100; Carl Zeiss) or a Zeiss LSM510 laser- 2 YWHAZ stably expressing clones (YWHAZ #1 and scanning confocal microscope image system. YWHAZ #3) and 1 mock control were: (i) subcutaneously implanted into the dorsal regions of NOD SCID mice, (ii) Luciferase reporter assay directly injected to the circulation of mice to eschew the TOPFLASH or FOPFLASH (Millipore) plasmid was initial steps of local invasion and intravasation, and (iii) transfected into CL1-0 cells or CL1-5 cells together with orthotopically injected into 1 lobe of mouse lung. As shown the indicated plasmids. Renilla luciferase plasmid (pRL-TK) in Fig. 2A, hematoxylin and eosin (H&E) staining and was cotransfected as an internal control. Cell lysates were immunohistochemistry revealed that the lungs of mice collected 48 hours after transfection, and the dual-luciferase implanted by YWHAZ transfectants contained many more assay was conducted according to the manufacturer's micrometastatic lesions than the mock controls. The average protocol. human-vimentin stain burden was 23 to 29 per lung in mice inoculated with the YWHAZ transfectants (Fig. 2B). This Statistical analysis result implied that YWHAZ is able to promote cell metas- Data are presented as the mean SD for at least 3 tasis in vivo. For circulation injection, mice with YWHAZ independent experiments. The quantitative in vitro and transfectants developed more pulmonary metastasis nodules in vivo data were analyzed using the Student t test. All than with the mock control (Fig. 2C). The nodule numbers analyses were conducted using SPSS software (v10.0; SPSS, of YWHAZ #1 and YWHAZ #3 groups were 12 1.72 Inc.) and SAS v 9.1 software (SAS Institute, Inc.). All and 11.3 1.91, respectively, but none in mock controls statistical tests were 2-sided, and P values <0.05 were (Fig. 2D). Macrometastatic lesions in various lung sections considered statistically significant. are shown in Supplementary Table S1. For the orthotopical

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A B 6 500

400 4 Figure 1. YWHAZ is associated 300 with invasion and migration of lung cancer cells. A, YWHAZ copy 200 number, mRNA, and protein 2 expression. Top, YWHAZ copy number was detected by real-time

No. of invaded cells of invaded No. 100 n ¼ P < YWHAZ copy number YWHAZ copy genomic PCR ( 6; , 0.001 0 vs. mock). Middle, mRNA was 0 measured by qRT-PCR (n ¼ 3; CL1-0 CL1-5 , P < 0.001 vs. mock). TATA-box CL1-0 CL1-5 Mock binding protein (TBP) served as the 6 internal control. Bottom, YWHAZ YWHAZ YWHAZ#1 YWHAZ#2 #3 YWHAZ #mix expression was measured by b CL1-0 Western blot analysis. -Tubulin 4 C served as the internal control. B, invasion capability of V5-tagged YWHAZ-transfectants as analyzed 600 by Matrigel invasion assays (n ¼ 3; 2 , P < 0.004 vs. mock). Mock: vector only transfectant; YWHAZ 400 #1, YWHAZ #2, and YWHAZ #3:

Relative mRNA expression Relative 0 single clone; YWHAZ #mix: mixed clone. C, migration ability of cells 200 CL1-0 CL1-5 with constitutive V5-tagged YWHAZ expression as determined No. of migrated cells of migrated No. by in vitro transwell migration 0 assays (n ¼ 3; , P < 0.002 vs. CL1-0 CL1-5 mock). YWHAZ CL1-0 CL1-5 Mock YWHAZ YWHAZ#1 YWHAZ#2 #3 β-Tubulin YWHAZ #mix 1.0 6.0 Ratio CL1-0

lung injection with YWHAZ stably expressing clone cells, tagged YWHAZ. Morphologically, there was also a change we have observed a significant increase in tumorigenesis at from the cobble-like appearance of low invasive CL1-0 the site of injection, and an increase in local metastasis to the and/or mock control cells to a neuron-like morphology of adjunct lobe of the lung, and distant metastasis to the liver, cells in these V5-tagged YWHAZ-expressing clones (Fig. compared with the mock control cell injections (Fig. 2E and 3A, top). Colonies formed by V5-tagged YWHAZ-expres- Supplementary Table S2). These in vivo studies, which are sing cells exhibited a well-spread morphology. Cell surface consistent with previous in vitro findings strongly support protrusions and branches were evident after phalloidin and the oncogenic nature of YWHAZ in promoting cancer DAPI staining (Fig. 3A, bottom). Quantitative data had metastasis. shown a 70% increase in the ratio of cell branching by YWHAZ expression as compared with mock control cells YWHAZ induces a neuron-like morphologic change and (Supplementary Fig. S2). Western blot analysis showed that EMT the levels of N-cadherin, vimentin, and Slug increased in To identify the downstream genes regulated by YWHAZ, all of the YWHAZ transfectants compared with the mock differentially gene expression profilings were carried out in control (Fig. 3B). Conversely, knockdown of endogenous microarray gene chips (GEO series accession no. YWHAZ expression in 2 highly YWHAZ-expressing cell GSE20318), followed by the analysis with our in-house lines, CL1-5 and A549, by siRNA increased E-cadherin pathway analysis tool (29) as well as a commercial software, expression and reduced Slug expression (Fig. 3C). To rule GeneGo (http://www.genego.com/metacore). These path- out the effects of off-target, we silenced YWHAZ gene in way analyses had identified 4 EMT-related pathways in the the highly invasive CL1-5 cells by using 2 independent top 10 pathways that were significantly affected by YWHAZ-specific short hairpin RNAs (shRNA) and found YWHAZ. The differentially expressed genes involved in that knockdown of YWHAZ resulted in a reciprocal alter- these pathways were validated using quantitative real-time ation in EMT markers (Fig. 3D). These ectopic expression PCR (qRT-PCR; Table 1). Among them, the Wnt signaling and knockdown approaches have showed the oncogenic pathway was highly activated in cells stably expressing V5- nature of YWHAZ in mediating EMT phenotype.

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A Mock YWHAZ #1 YWHAZ #3

Figure 2. YWHAZ is a metastasis- promoting gene in lung cancer. A, micrometastatic analysis of V5- tagged YWHAZ transfectants. Top, representative H&E–stained sections of lungs from SCID mice (n ¼ 6) with subcutaneous tumors. The black arrow indicates the micrometastasis of CL1-0 cells expressing V5-YWHAZ. Bottom, immunohistochemical stain showing micrometastatic lesions by using antihuman vimentin antibody. B, quantification of the average BC numbers of human-vimentin stains Mock YWHAZ #1 YWHAZ #3 in the lungs of these mice with subcutaneous tumors ( , P < 0.01 vs. 40 mock). C, macrometastatic analysis of V5-tagged YWHAZ transfectants. 30 Appearance and representative H&E–stained sections of the lungs 20 from SCID mice injected intravenously with V5-tagged 10 YWHAZ-expressing cells. The 0 arrows indicate the metastasis Human-vimentin stained no. ranges for each group (n ¼ 6); Mock magnification, 20. D, quantification of the average YWHAZ #1YWHAZ #3 pulmonary metastasis nodules from DE these mice with intravenously Lung Liver injected cancer cells (, P < 0.002 vs. Mock YWHAZ #mix Mock YWHAZ #mix mock). E, gross and H&E staining of 16 sections of lungs and livers from mice after orthotopic lung 12 implantation (n ¼ 6). The black arrow indicates tumor mass. 8

0 Metastatic nodules/mouse

Mock

YWHAZ #1YWHAZ #3

YWHAZ facilitates activation of b-catenin and cotransfected with the TOPFLASH reporter with or without b-catenin–mediated invasiveness V5-YWHAZ expression plasmids. Coexpression of CL1-0 Wnt/b-catenin signaling pathway is well-established in cells with V5-YWHAZ promoted a 2.6-fold increase in EMT and cell invasiveness. On the basis of the findings of endogenous b-catenin–dependent transcription (Fig. 4C, gene array analysis, we focused on the effects of YWHAZ on left). Moreover, knockdown of YWHAZ expression signi- regulating b-catenin signaling activity. Immunofluorescent ficantly attenuated TOPFLASH activity in CL1-5 cells staining has shown an increase of b-catenin presence in the (Fig. 4C, right). To further explore whether the metastatic nucleus of YWHAZ-transfectant cells (Fig. 4A). Western activity of YWHAZ is associated with b-catenin activation, blot analysis further showed an increase of b-catenin proteins we examined the invasion capability of V5-YWHAZ trans- in both the cytosolic and nuclear fractions of cells that fectants with b-catenin silencing by using specific b-catenin ectopically expressed more with YWHAZ (Fig. 4B). To siRNAs. For V5-YWHAZ–expressing cells, approximately clarify whether YWHAZ expression modulates nuclear 50% decrease of invasion ability was found in these cells with activity of b-catenin in lung cancer cells, CL1-0 cells were low b-catenin expression (Fig. 4D), thus suggesting that

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Table 1. EMT-related pathways involved in CL1-0 cells following YWHAZ gene introduction

YWHAZ # mix/mock (fold change)

Gene Real-time Accession code symbol Gene name Function Affymetrix RT–PCR Wnt signaling pathway NM_003507 FZD7 Frizzled homolog 7 (Drosophila) Wnt receptor 2.976 1.507 NM_006183 NTS Neurotensin Neurotransmitter 5.439 6.274 NM_003199 TCF4 Transcription factor 4 Transcription factor 2.679 2.606 NM_053056 CCND1 Cyclin D1 Regulators of CDK 4.698 3.581 kinases NM_012342 BAMBI BMP and activin membrane- Signal transduction 2.925 2.337 bound inhibitor homolog NM_001002880 CBY1 Chibby homolog 1 Inhibiting b-catenin– 0.831 0.731 (Drosophila) mediated transcriptional activation

TGF-b signaling pathway NM_000660 TGFB1 Transforming growth Inducing transformation 1.368 1.521 factor, b–1 NM_001015886 HMGA2 High mobility group AT-hook 2 Transcriptional regulating 1.935 1.301 factor NM_002317 LOX Lysyl oxidase Tumor suppressor gene 0.352 0.111 NM_006079 CITED2 Cbp/p300-interacting Angiogenesis and 3.58 2.861 transactivator, with Glu/Asp-rich development carboxy-terminal domain, 2

Focal adhesion NM_002210 ITGAV Integrin, aV Cell adhesion and 2.668 2.487 facilitate signal transduction NM_002086 GRB2 Growth factor receptor-bound Signal transduction 1.867 1.667 protein 2 NM_000090 COL3A1 Collagen, type III, a1 Extracellular matrix 4.193 2.536 NM_001753 CAV1 Caveolin 1 Negative regulator of the 0.154 0.311 Ras-p42/44 MAP kinase cascade NM_001233 CAV2 Caveolin 2 Negative regulator of the 0.101 0.111 Ras-p42/44 MAP kinase cascade NM_001945 HBEGF Heparin-binding EGF-like growth Angiogenesis and signal 4.176 3.044 factor transduction

Regulation of actin cytoskeleton NM_002356 MARCKS Myristoylated alanine-rich protein Cell motility 5.819 2.408 kinase C substrate NM_012250 RRAS2 Related RAS viral (r-ras) oncogene Inducing transformation 2.151 1.54 homolog 2 NM_004447 EPS8 EGF receptor pathway substrate 8 Signal transduction 1.708 1.427 NM_004342 CALD1 Caldesmon 1 Regulation of cell 1.995 1.386 contraction

NOTE: NM_003406 YWHAZ, Affymetrix (YWHAZ # mix/mock): 1.753-fold; real-time RT-PCR (YWHAZ # mix/mock): 2.773-fold.

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A Mock YWHAZ #1 YWHAZ #3 YWHAZ #mix

Figure 3. YWHAZ expression is crucial for inducing EMT. A, effect of YWHAZ overexpression on cell morphology and protrusions formation as well as branchings. The morphology of CL1-0 cells expressing either the control vector or V5-YWHAZ was examined by phase contrast microscopy after BC plating for 24 hours (top). Bottom, immunoﬂuorescent staining of the transfectants. F-actin was stained CL 1-5 A549 with phalloidin, indicating the cell Mock YWHAZYWHAZ #1 YWHAZ #2 YWHAZ #3 #mix YWHAZ siRNA morphology; and nucleus was E-cadherin E-cadherin counter-stained with DAPI. B, expression of EMT markers in mock N-cadherin N-cadherin and YWHAZ transfectants, as Vimentin Vimentin measured by immunoblotting. b-Tubulin served as a loading Slug Slug control. C, Western blot analysis of V5-YWHAZ YWHAZ epithelial and mesenchymal proteins in CL1-5 and A549 cells after β-Tubulin β-Tubulin transient transfection with YWHAZ- speciﬁc siRNA for 48 hours. D, the D effects of YWHAZ silencing on EMT proteins determined by 2 independent YWHAZ–shRNAs (sh-YWHAZ-1 and sh-YWHAZ-2) YWHAZYWHAZ transfectants in CL1-5 cells. sh-Luc sh- sh- -1 -2 E-cadherin N-cadherin Vimentin Slug YWHAZ β-Actin

YWHAZ enhances cell invasiveness in coordination with is caused by retardation of 26S proteasome-mediated deg- b-catenin. radation of ubiquitinated proteins, cells were treated with MG-132. The results showed that MG-132 treatment YWHAZ associates with b-catenin to retard degradation prevented the degradation of b-catenin in the mock con- of b-catenin via the ubiquitin–proteasome pathway trols to a level almost equal to that of the mixed clone of Because YWHAZ overexpression causes the accumula- V5-YWHAZ transfectants (Fig. 5B, left). Immunoprecip- tion of b-catenin in cytosol and nucleus (Fig. 4B), we next itation of b-catenin has shown a reduced level of the ask whether YWHAZ also regulates b-catenin expression. MG132-induced ladder forms of b-catenin in cells that Interestingly, we found that protein levels of b-catenin were were stably expressing V5-YWHAZ (Fig. 5B, right). To elevated in V5-YWHAZ transfectants, but mRNA expres- address whether the ladder forms of b-catenin came from sion was not proportionally increased in these cells (Fig. ubiqutin conjugation, we conducted coimmuno- 5A), suggesting a potential regulation at the posttransla- precipitation followed by Western blot analysis on tional level. To explore this possibility, cycloheximide cell extracts from both mock and V5-YWHAZ transfec- (CHX) was used to characterize the protein turnover in tants and found a reduction in ubiquitinated b-catenin cells. In V5-YWHAZ–transfected cells, the time course in presence of V5-YWHAZ–b-catenin interaction in V5- turnover of b-catenin levels was much slower than that YWHAZ–expressing cells but not in the mock (Fig. 5C). observed in mock control cells (Supplementary Fig. S3). To further conﬁrm that b-catenin degradation is related to Next, to investigate whether the accumulation of b-catenin ubiquitination, Myc-tagged ubiquitin was transfected into

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AB Mock YWHAZ #1 YWHAZ #3 Cytoplasm Nucleus Mock YWHAZ #1 YWHAZ #2 YWHAZ #3 YWHAZ #mix Mock YWHAZ #1 YWHAZ #2 YWHAZ #3 YWHAZ #mix β-Catenin V5-YWHAZ TBP α-Tubulin CD *P < 0.001 3 300 1 CTNNB1 siRNA pEF6/V5-YWHAZ 2 200 Slug β 0.5 -Catenin

(TOP/FOP) 1 (TOP/FOP) 100 V5-YWHAZ

No. of invaded cells of invaded No. β

Relative activation fold activation Relative fold activation Relative -Actin 0 0 0 pEF6/V5 YWHAZ CTNNB1 siRNA -YWHAZ -siRNA pEF6/V5-YWHAZ CL1-0 CL1-5

Figure 4. YWHAZ promotes activation of b-catenin relevant to cell invasiveness. A, the subcellular localization of b-catenin in the V5-tagged YWHAZ-expressing cells, measured by immunofluorescent staining. Green: b-catenin; red: F-actin; blue: nuclear DNA. B, Western blot analysis of b-catenin in the cytosolic and nuclear portions of V5-tagged YWHAZ transfectants. C, YWHAZ expression regulates transcriptional activity of b-catenin/TCF4 in lung cancer cells. CL1-0 (left) or CL1-5 (right) cells in 24-well plates were respectively transfected with 0.5 mg of V5-YWHAZ plasmids or 40 nmol/L YWHAZ-specific siRNAs as indicated. TOPFLASH (TOP) or FOPFLASH (FOP) plasmids (0.3 mg) were used for the reporter assay. pRL-TK was cotransfected as an internal control. The results are presented as the TOP/FOP ratio. , P < 0.05 compared with control. D, silencing of b-catenin diminishes invasion capability of V5-tagged YWHAZ-transfectants. CL1-0 cells were cotransfected with V5-YWHAZ plasmids and/or b-catenin–specific siRNAs as indicated. Following transfection, cells were subjected to invasion assays at 48 hours (left, n ¼ 5) and then cell lysates were immunoblotted with appropriate antibodies (right).

mock and YWHAZ-expressing cells, and immunopre- in interfering b-catenin ubiquitination and possibly, the cipitation assays conﬁrmed a marked increase of the ubi- stability of b-catenin in cancer cells. quitin conjugates on b-catenin in mock control cells. Constantly, overexpression of YWHAZ attenuated the Interaction of YWHAZ and b-catenin enhances cancer levels of ubiquitin conjugates on b-catenin (Supplementary invasion Fig. S4). Previous reports (30, 31) and sequences analysis of To characterize the interaction and the importance of the b-catenin protein (Supplementary Fig. S5A) have indicated YWHAZ/b-catenin complex in cancer cells, especially in the an interaction between YWHAZ and b-catenin. How- cell invasiveness, V5-tagged wild-type and mutants of ever, the function of this interaction has not been b-catenin expression constructs were generated and the addressed. As shown in Fig. 5D and Supplementary Fig. mutation changes at serine552 site, such as S552A and S5B, coimmunoprecipitation and in vitro GST pull-down S552D, were selected according to the information obtained assays showed a cytosolic association between YWHAZ and from the ScanSite software (http://www.motifscan.mit.edu; b-catenin in lung cancer cells. On the basis of the results, Supplementary Fig. S5A) and a previous report (32). These we suggested that the interaction between YWHAZ and constructs were transfected on Myc-tagged YWHAZ-trans- b-catenin contributes to a decrease in b-catenin ubiquiti- fectant cells. Immunoprecipitation with anti-Myc anti- nation. b-TrCP E3 ligase is responsible for the ubiquitina- body on cell extracts of these transfected cells showed a tion of b-catenin. Interestingly, the interaction of YWHAZ diminished interaction between the S552A mutant of with b-catenin suppressed b-TrCP binding to b-catenin in b-catenin and Myc-tagged YWHAZ (Fig. 6A). Reciprocal V5-YWHAZ–expressing cells, and thus consequently immunoprecipitation assays with anti-V5 antibody also increased b-catenin stability (Fig. 5E). These results showed that Myc-tagged YWHAZ binding to mutant pro- showed a competing nature of YWHAZ/b-catenin complex tein of V5-tagged S552A b-catenin was decreased by 56.3%

1326 Mol Cancer Res; 10(10) October 2012 Molecular Cancer Research

YWHAZ/b-Catenin Axis in Lung Cancer Metastasis

Figure 5. YWHAZ binding to b-catenin prevents b-catenin from ubiquitin-mediated degradation. A, an increase of the b-catenin proteins in V5-tagged YWHAZ transfectants. Top, the protein levels of b-catenin and YWHAZ in these transfectants, determined by Western blot analysis. Bottom, the mRNA levels of b-catenin and YWHAZ in the transfectants determined by qRT-PCR. B, YWHAZ overexpression induces the inhibition of b-catenin degradation. Left, the protein level of b-catenin after treatment with 10 mmol/L of proteasome inhibitor (MG-132). Right, the transfectants were treated with 10 mmol/L of MG-132 for 3 hours, followed by immunoprecipitation and immunoblotting. C, the effect of V5-tagged YWHAZ on b-catenin ubiquitination, determined by immunoprecipitation and immunoblotting conducted using the indicated antibodies. D, the cytosolic interaction between YWHAZ and b-catenin in invasive CL1-5 cells. Cytoplasmic lysates were immunoprecipitated using appropriate antibodies and then Western blot analysis was conducted. E, reduced binding activity of b-catenin with b-TrCP in presence of V5-tagged YWHAZ. The immunoprecipitated b-catenin proteins from CL1-0, mock, or V5-YWHAZ–expressing cells were immunoblotted with appropriate antibodies. Fifteen micrograms of cell lysates were used as the input controls.

8.8% as compared with its binding to wild-type protein of nin (Ser552) with YWHAZ (Supplementary Fig. S6). On V5-tagged b-catenin (Fig. 6B). Therein, we found that the the basis of the above observations, we evaluated whether ubiquitination level on mutant protein of V5-tagged S552A there could be a relationship between S552 phosphorylation b-catenin was higher than that of wild-type V5–b-catenin levels of b-catenin and b-TrCP binding activity. The results and the S552D mutant in these transfected Myc-tagged showed that S552 phosphorylation was enhanced by the YWHAZ-expressing transfectants. We also analyzed wheth- expression of YWHAZ accompanied with a reduced inter- er an increase in endogenous S552 phosphorylation of action of b-TrCP with b-catenin (Fig. 6C). Because an b-catenin promotes its interaction with YWHAZ. Immu- increased interaction between YWHAZ and b-catenin was noprecipitation of endogenous YWHAZ showed a signiﬁ- found to reduce b-catenin ubiquitination in these cells, we cant interaction between phospho-b-catenin (Ser552) and further examined if this change also affects cell invasiveness. YWHAZ in lung cancer cells grown in the medium supple- For highly invasive CL1-5 cells, the invasiveness was signif- mented with 10% serum. On the contrary, serum starvation icantly impaired in S552A b-catenin mutant–transfected downregulated the phosphorylation levels of b-catenin at cells, as compared with those cells transfected with wild- Ser552 and thereby reduced the binding of phospho-b-cate- type b-catenin (Fig. 6D, Top). In Myc-tagged YWHAZ-

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Chen et al.

Figure 6. Disruption of the interaction between YWHAZ and b-catenin reduces cancer invasion. A, conﬁrmation of the YWHAZ binding site on b-catenin protein. Each pcDNA3.1-CTNNB1 (V5-tagged b-catenin) construct or pcDNA3.1 (mock) was cotransfected with pCMV-Tag3B- YWHAZ (Myc-tagged YWHAZ) construct into HEK293 cells followed by immunoprecipitation and immunoblotting using the indicated antibodies. B, the level of V5-b-catenin ubiquitination in various transfected cells. Wild- type, S552A or S552D b-catenin was coexpressed with Myc-tagged YWHAZ in HEK293 cells. After coexpression of pCMV-Tag3B- YWHAZ and pcDNA3.1- CTNNB1 constructs, the level of ubiquitin binding to V5-tagged b-catenin was examined by immunoprecipitation using an anti-V5 antibody. Twenty micrograms of cell lysates served as the input controls. C, Coimmunoprecipitation analysis of the association between phospho– b-catenin (Ser552) and b-TrCP in V5-YWHAZ–overexpressing cell lines. D, the invasion ability of V5-b- catenin transfectants in lung cancer cells. Empty vector, wild- type, S552A, or S552D b-catenin was expressed in CL1-5 cells (top) or coexpressed with Myc-tagged YWHAZ in CL1-0 cells (bottom). After 24 hours of transfection, the invasion capacity of the transfectants was evaluated with Matrigel invasion assays. E, a hypothetical model for YWHAZ- mediated lung cancer metastasis. YWHAZ associates with the soluble form of b-catenin to protect b-catenin from degradation and subsequently results in an increase in the nuclear accumulation of b-catenin leading to the activation of EMT markers and cancer malignancy.

expressing CL1-0 cells, we found that the invasiveness of the the metastatic activity of YWHAZ is mediated through the S552A b-catenin mutant–transfected cells was signiﬁcantly prevention of b-catenin ubiquitination. We showed that decreased by 48% 12% as compared with wild-type YWHAZ associates with phospho-b-catenin at Ser552 b-catenin transfected cells (Fig. 6D, Bottom), suggesting to retard b-catenin degradation. Subsequently, b-catenin that expression of wild-type or S552D b-catenin promotes accumulation in cancer cells contributes to its nuclear cell invasiveness together with YWHAZ. Taken together, translocation and the activation of EMT-related genes these results indicate that the formation of the YWHAZ/ (Fig. 6E). Conversely, disruption of the YWHAZ–b-catenin b-catenin complex promotes invasion of lung cancer cells. interaction enhances b-catenin ubiquitination and reduces cell invasiveness. Discussion YWHAZ protein expression is well known to be associ- Our results identiﬁed a novel pathway of YWHAZ– ated with advanced disease grade and poor clinical outcome b-catenin axis in NSCLC cell malignancy. We showed that in Western NSCLC patients (18), but the molecular

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YWHAZ/b-Catenin Axis in Lung Cancer Metastasis

contribution of YWHAZ in lung cancer metastasis is still and colleagues (32). Next, we found that this interaction unknown. Particularly, it is unclear whether YWHAZ gene reduces the binding ability of b-TrCP to b-catenin in cells amplification is relevant to lung cancer progression. Here, we with enforced expression of YWHAZ. It is reasonable to conducted array CGH and microarray to identify YWHAZ postulate that higher expression of YWHAZ would compete as an invasion-enhancer candidate. Actually, YWHAZ gene with b-TrCP in the interaction of b-catenin. Through amplification was found in highly invasive cell line, CL1-5. YWHAZ–b-catenin interaction, we speculated that the We first verified that the amplified DNA copy number of binding site of b-TrCP in b-catenin may be masked by YWHAZ correlates with lung cancer invasiveness. Both YWHAZ, leading to decrease interaction of b-TrCP with in vitro and in vivo studies revealed that YWHAZ promotes b-catenin and increase b-catenin stability. On the other cancer invasion/metastasis through stabilizing b-catenin, hand, it is possible that YWHAZ binding to b-catenin causes leading to the induction of EMT (Figs. 1–4). Specifically, a conformational change of b-catenin and contributes to our study presents the molecular mechanism by which increased disassociation of b-TrCP and b-catenin. Accord- YWHAZ regulates lung cancer progression. First, YWHAZ ingly, we concluded that YWHAZ may protect the serine- associates with the soluble form of b-catenin to protect phosphorylated b-catenin from ubiquitination by forming a b-catenin from ubiquitin-mediated degradation (Fig. 5), complex with b-catenin, which may explain why YWHAZ which suggests a novel mechanism by which b-catenin expression promotes the accumulation of b-catenin and accumulates in the cytoplasm and is protected from degra- activates b-catenin–dependent transcription. dation in cancer cells. Second, we present new evidence b-Catenin signaling has emerged as a critical pathway in of b-catenin accumulation via YWHAZ binding to phos- human lung carcinogenesis (37) and malignancies (38–40). pho-b-catenin at Ser552 (Fig. 6). Taken together, our results In this work, we have shown that YWHAZ promotes show the importance of YWHAZ/b-catenin axis in the activation of b-catenin that is relevant to cell invasiveness development of NSCLC metastatic potential and EMT in lung cancer. It is consistent with these previous results (31, phenotype. 32) that YWHAZ directly binds to b-catenin and promotes During metastasis, cancer cells acquire the ability to transcriptional activity of b-catenin. The activation of target become motile and invade adjacent tissue by inducing EMT genes by b-catenin–TCF/LEF complexes, including cyclin (33). YWHAZ has been reported to be one of the TGF- D1 (14), c-Myc (15), and Slug (12, 41), is believed to b–induced proteins involved in cancer cell transformation provide a growth or migration advantage to cells. The results (34). So far, the action of YWHAZ on inducing EMT in of microarray and real-time RT-PCR showed an increase in lung cancer cells is still unclear. Recently, the relationship cyclin D1 expression, which may explain how YWHAZ between YWHAZ and EMT has been verified in breast promotes cell proliferation and tumorigenesis. Another cancer and head/neck squamous cell carcinoma (20, 23). In target gene of b-catenin, Slug, is an important transcription breast cancer, it has been verified that YWHAZ cooperates factor that promotes tumor growth, invasion, and drug with ErbB2 to induce EMT, but not cell migration, through resistance (8, 42, 43). On the basis of our current data, we the TGF-b signaling pathway. In lung cancer, we found that also found enhanced expression of Slug in presence of YWHAZ promotes EMT, cell invasion, and migration by YWHAZ expression. Unlike the findings in breast cancer activating the YWHAZ/b-catenin axis. Our observation in (23), Slug is an effector in YWHAZ-mediated EMT path- lung cancer is different from those in breast cancer, which way in lung cancer through activation of b-catenin. Acti- reveals a lung cancer–specific pathway mediated by vation of b-catenin is reported to be related to b-catenin YWHAZ. To our knowledge, our study is the first to show phosphorylation. It is well documented that AKT-mediated the role of YWHAZ in inducing EMT to elucidate the phosphorylation of b-catenin (Ser552) by EGFR signaling metastatic characteristics of YWHAZ in lung cancer. causes b-catenin disengaging from cell contacts and activates YWHAZ, a member of the 14-3-3zeta protein family, transcriptional activity of b-catenin (32). Our studies modulates cellular events by interacting with phosphoserine extended the above observations of b-catenin phosphoryla- proteins, including b-catenin (30). Although b-catenin is tion (Ser552) in lung cancer. Furthermore, we showed a verified to be a binding partner of YWHAZ, we were decrease of ubiquitination in phosphorylated b-catenin at surprised to discover that YWHAZ exerts its oncogenic Ser552, such as WT or S552D b-catenin upon enforced function through its binding with b-catenin in lung cancer expression of YWHAZ, implying the importance of cells. b-Catenin is a central effector of Wnt signaling in YWHAZ expression in enhancing transcriptional activity tumorigenesis and metastasis (35). Indeed, our microarray of phosphorylated b-catenin at Ser552. Fang and colleagues analysis showed that Wnt signaling is the most likely indicated that AKT-mediated phosphorylation of b-catenin pathway to be affected by YWHAZ and to cause EMT. A at S552 does not alter b-catenin protein stability in 293T recent article has shown that abnormal b-catenin expression cells with low YWHAZ expression. We believe that the was associated with positive YWHAZ expression in stage-I conclusion might be from the low expression of YWHAZ in NSCLC (36). In fact, we confirmed these observations 293T and normal cells. and further elucidated a mechanistic role of YWHAZ In summary, we not only provide evidence that YWHAZ in the accumulation of b-catenin. Our coimmunoprecipita- participates in lung cancer progression but also illustrate tion assays revealed that YWHAZ is associated with phos- the critical role of the YWHAZ/b-catenin complex in pho–b-catenin at S552, consistent with the finding by Fang cancer metastasis. Collectively, we show the importance of

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Chen et al.

YWHAZ in lung cancer malignancy and propose that Acknowledgments the YWHAZ–b-catenin axis may serve as potential anti- The authors thank Drs. G.-C. Tseng (Department of Pathology, China Medical University Hospital, Taiwan) and R. Wu (School of Veterinary Medicine, cancer target. University of California, Davis, CA) for useful advice and discussion. The shRNA constructs were obtained from the National RNAi Core Facility located at the Disclosure of Potential Conﬂicts of Interest Institute of Molecular Biology/Genomic Research, Academia Sinica (Taipei, No potential conﬂicts of interest were disclosed. Taiwan).

Authors' Contributions Grant Support Conception and design: C.-H. Chen, S.-L. Yu, J.J.W. Chen This work was supported by grants from the National Science Council, Taiwan, Acquisition of data (provided animals, acquired and managed patients, provided ROC (NSC 97-2314-B-005-002-MY3), as well as in part by the Ministry of facilities, etc.): C.-H. Chen, M.-F. Yang Education, Taiwan, ROC under the ATU plan. Analysis and interpretation of data (e.g., statistical analysis, biostatistics, compu- The costs of publication of this article were defrayed in part by the pay- tational analysis): C.-H. Chen, M.-F. Yang ment of page charges. This article must therefore be hereby marked adver- Writing, review, and/or revision of the manuscript: C.-H. Chen, S.-M. Chuang, tisement in accordance with 18 U.S.C. Section 1734 solely to indicate this S.-L. Yu, J.J.W. Chen fact. Administrative, technical, or material support (i.e., reporting or organizing data, constructing databases): C.-H. Chen, S.-M. Chuang, M.-F. Yang, J.-W. Liao, J.J.W. Chen Received March 29, 2012; revised August 2, 2012; accepted August 3, 2012; Study supervision: S.-M. Chuang, S.-L. Yu, J.J.W. Chen published OnlineFirst August 21, 2012.

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A Novel Function of YWHAZ/β-Catenin Axis in Promoting Epithelial −Mesenchymal Transition and Lung Cancer Metastasis

Ching-Hsien Chen, Show-Mei Chuang, Meng-Fang Yang, et al.

Mol Cancer Res 2012;10:1319-1331. Published OnlineFirst August 21, 2012.

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