25937

WWTR1

WW domain containing transcription regulator 1;WWTR1;WW domain containing transcription regulator 1

WW domain-containing transcription regulator protein 1|transcriptional co-activator with PDZ-binding motif|transcriptional coactivator with PDZ-binding motif

3q23-q24

protein-coding

The Hippo signaling pathway regulates cellular proliferation and survival, thus exerting profound effects on normal cell fate and tumorigenesis. We previously showed that the pivotal effector of this pathway, YAP, is amplified in tumors and promotes epithelial-to-mesenchymal transition (EMT) and malignant transformation. Here, we report that overexpression of TAZ, a paralog of YAP, in human mammary epithelial cells promotes EMT and, in particular, some invasive structures in 3D cultures. TAZ also leads to cell migration and anchorage-independent growth in soft agar. Furthermore, we identified amphiregulin (AREG), an epidermal growth factor receptor (EGFR) ligand, as a target of TAZ. We show that AREG functions in a non-cell-autonomous manner to mediate EGF-independent growth and malignant behavior of mammary epithelial cells. In addition, ablation of TEAD binding completely abolishes the TAZ-induced phenotype. Last, analysis of breast cancer patient samples reveals a positive correlation between TAZ and AREG in vivo. In summary, TAZ-dependent secretion of AREG indicates that activation of the EGFR signaling is an important non-cell-autonomous effector of the Hippo pathway, and TAZ as well as its targets may play significant roles in breast tumorigenesis and metastasis.

The hypoxic microenvironment of bone marrow favours the bone metastasis process. Hypoxia inducible factor (HIF)-1alpha is hallmark for hypoxia, correlating with poor prognosis and radio/chemotherapy resistance of primary-breast carcinoma. For bone metastasis, the molecular mechanisms involved in HIF-1alpha expression and HIF-1 (alpha/beta heterodimer)-transcription factor activity are scarcely known. We studied the role played by HIF-1 in the cross-talk between neoplastic and supportive-microenvironmental cells. Also, WWdomain-containing oxidoreductase (Wwox) and transcriptional co-activator with PDZ-binding motif (TAZ) were taken into consideration evaluating whether these Hippo-pathway effectors affect bone-metastatic phenotype through HIF-1 activity. Considering bone-metastasis specimens, nuclear HIF-1alpha-TAZ co-localisation occurred in neoplastic and supportive cells, such as fibroblasts and endotheliocytes. Based on these data, the functional importance was verified using 1833-bone metastatic clone under hypoxia: nuclear HIF-1alpha and TAZ expression increased and co-immunoprecipitated, activating HIF-1-DNA binding and transactivation. In contrast, Wwox localised at perinuclear level in neoplastic cells of bone metastasis, being almost absent in supportive cells, and Wwox-protein expression diminished in hypoxic-1833 cells. Thus, TAZ regulation of HIF-1 activity might be important for bone-secondary growth, participating in metastasis-stroma cross-talk. Further, TAZ and HIF-1alpha-protein levels seemed correlated. In fact, blocking cyclooxygenase-2 with NS398 in hypoxic-1833 cells, not only HIF-1alpha decreased but also molecular-mechanism(s) upstream of the Hippo pathway were triggered: LATS-dependent TAZ phosphorylation seemed responsible for TAZ nucleus/cytoplasm translocation and degradation. In the 1833-xenograft model, NS398 largely prevented the outgrowth of bone-metastatic cells, probably related to remarkable-extracellular matrix assembly. We gained clinical insight into HIF-1alpha and TAZ as candidate biomarkers for bone avidity, relevant for early-therapeutic intervention against bone metastasis.

BACKGROUND AND OBJECTIVE: Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) are nuclear effectors of the Hippo pathway. Although they are abundantly expressed in the cytoplasm and nuclei of human colorectal cancer (CRC), and related to tumor proliferation status, there have been few studies on the predictive role of YAP and TAZ expression on the overall survival of patients with CRC. This study investigated YAP and TAZ expression in both CRC patients and colon cancer cell lines, and assessed their prognostic value. METHODS: Paraffin-embedded specimens from 168 eligible patients were used to investigate YAP and TAZ expression by immunohistochemistry, and compared with experimental results in colon cancer HCT116 cell line to explore their clinical significance in CRC. RESULTS: Statistically significant positive correlations were found between protein expression of YAP and TAZ in CRC tissues. Patients with higher YAP or TAZ expression showed a trend of shorter survival times; more importantly, our cohort study indicated that patients with both YAP and TAZ overexpression presented the worst outcomes. This was supported by multivariate analysis. In HCT116 colon cancer cells, the capacity for proliferation, metastasis, and invasion was dramatically reduced by knockdown of YAP and TAZ expressions by siRNA. CONCLUSIONS: Co-overexpression of YAP and TAZ is an independent predictor of prognosis for patients with CRC, and may account for the higher proliferation, metastasis, and poor survival outcome of these patients.

YAP and its paralog protein TAZ are downstream effectors of the Hippo pathway. Both are amplified in many human cancers and promote cell proliferation and epithelial-mesenchymal transition. Little is known about the status of the Hippo pathway in cutaneous melanoma. We profiled Hippo pathway component expression in a panel of human melanoma cell lines and melanocytic lesions, and characterized the capacity of YAP and TAZ to control melanoma cell behavior. YAP and TAZ immuno-staining in human samples revealed mixed cytoplasmic and nuclear staining for both proteins in benign nevi and superficial spreading melanoma. TAZ was expressed at higher levels than YAP1/2 in all cell lines and in those with high invasive potential. Stable YAP or TAZ knockdown dramatically reduced the expression of the classical Hippo target CCN2/connective-tissue growth factor (CTGF), as well as anchorage-independent growth, capacity to invade Matrigel, and ability form lung metastases in mice following tail-vein injection. YAP knockdown also reduced invasion in a model of skin reconstruct. Inversely, YAP overexpression increased melanoma cell invasiveness, associated with increased TEA domain-dependent transcription and CCN2/CTGF expression. Together, these results demonstrate that both YAP and TAZ contribute to the invasive and metastatic capacity of melanoma cells and may represent worthy targets for therapeutic intervention.