The Hippo transducer TAZ promotes epithelial to mesenchymal transition and cancer stem cell maintenance in oral cancer

Pharmacological activation of TAZ enhances osteogenic differentiation and bone formation of adipose-derived stem cells

Background

Adipose-derived stem cells (ADSCs) are an attractive cell source for bone tissue engineering and have great potential for bone regeneration and defect repair. The transcriptional coactivator with PDZ-binding motif (TAZ) has been demonstrated to modulate osteogenic and adipogenic differentiation of mesenchymal stem cells. However, its roles during ADSC differentiation and therapeutic potentials for bone regeneration have as yet not been well established.

Methods

TAZ expression was measured during osteogenic differentiation of ADSCs in vitro. Both loss-of-function and gain-of-function approaches by TAZ knockdown or enforced overexpression were utilized to determine its functions during osteogenic differentiation of ADSCs. TM-25659, a chemical activator of TAZ, was used to determine whether pharmacological activation of TAZ in ADSCs enhanced osteogenic differentiation in vitro and bone formation in animal models. The molecular mechanisms underlying TAZ in promoting osteogenesis of ADSCs were also explored.

Results

Increased TAZ expression was observed during osteogenic differentiation of human ADSCs. TAZ knockdown resulted in compromised osteogenic differentiation and enhanced adipogenic differentiation of ADSCs. In contrast, enforced TAZ overexpression yielded increased osteogenic differentiation and bone regeneration in vivo, and impaired adipogenic differentiation of ADSCs. Pharmacological activation of TAZ by its chemical activator TM-25659 facilitated osteogenic differentiation of ADSCs. Noticeably, transient treatment of ADSCs with TM-25659 or intraperitoneal injection of TM-25659 significantly enhanced bone regeneration of ADSCs loaded with porous β-TCP in vivo. Mechanistically, TM-25659 exposure significantly promoted TAZ phosphorylation and nuclear translocation, and potentiated the assembly of the TAZ-Runx2 complex. Subsequently, the TAZ-Runx2 complex was further recruited to the promoter of osteocalcin and in turn enhanced its transcription.

Conclusions

Our findings indicate that TAZ is a key mediator that promotes ADSC commitment to the osteoblast lineage. Pharmacological activation of TAZ in ADSCs might become a feasible and promising approach to enhance bone regeneration and repair.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0799-z) contains supplementary material, which is available to authorized users.

Overexpression of PIK3CA in head and neck squamous cell carcinoma is associated with poor outcome and activation of the YAP pathway

OBJECTIVES

Phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) is commonly altered in many human tumors, leading to the activation of p110α enzymatic activity that stimulates growth factor-independent cell growth. PIK3CA alterations such as mutation, gene amplification and overexpression are common in head and neck squamous cell carcinoma (HNSCC) and. We aim to explore how these alterations and clinical outcome are associated, as well as the molecular mechanisms involved.

MATERIAL AND METHODS

Mutation and copy-number variation in PIK3CA, and whole-genome expression profiles, were analyzed in primary HNSCC tumors from The Cancer Genome Atlas (TCGA) cohort (n = 243). The results were validated in an independent cohort form the University Hospital of A Coruña (UHAC, n = 62). Expression of the PIK3CA gene protein product (PI3K p110α) and nuclear YAP were assessed in tissue microarrays in a cohort from the University Hospital 12 de Octubre (UH12O, n = 91).

RESULTS

Only high expression of the PIK3CA gene was associated with poor clinical outcome. The study of gene expression, transcription factor and protein signatures suggested that the activation of the Hippo-YAP pathway, involved in organ size, stem cell maintenance and tumorigenesis, could underlie tumor progression in PI3KCA overexpressing tumors. Tissue arrays showed that PI3K p110α levels correlated with YAP nuclear localization in HNSCC tumors.

CONCLUSIONS

High expression of PIK3CA in HNSCC primary tumors identifies patients at high risk for recurrence. In these tumors, progression could rely on the Hippo-YAP pathway instead of the canonical Akt/mTOR pathway. This observation could have important implications in the therapeutic options for patients.

The morphological and molecular mechanisms of epithelial/endothelial-to-mesenchymal transition and its involvement in atherosclerosis

Cell transdifferentiation occurs during cardiovascular development or remodeling either as a pathologic feature in the progression of disease or as a response to injury. Endothelial-to-Mesenchymal Transition (EndMT) is a process that is classified as a specialized form of Epithelial-to-Mesenchymal Transition (EMT), in which epithelial cells lose their epithelial characteristics and gain a mesenchymal phenotype. During transdifferentiation, cells lose both cell-cell contacts and their attachment to the basement membrane. Subsequently, the shape of the cells changes from a cuboidal to an elongated shape. A rearrangement of actin filaments facilitates the cells to become motile and prime their migration into the underlying tissue. EMT is a key process during embryonic development, wound healing and tissue regeneration, but has also been implicated in pathophysiological processes, such organ fibrosis and tumor metastases. EndMT has been associated with additional pathophysiological processes in cardiovascular related diseases, including atherosclerosis. Recent studies prove a significant role for EndMT in the progression and destabilization of atherosclerotic plaques, as a consequence of EndMT-derived fibroblast infiltration and the increased secretion of matrix metalloproteinase respectively. In this review we will discuss the essential molecular and morphological mechanisms of EMT and EndMT, along with their common denominators and key differences. Finally, we will discuss the role of EMT/EndMT in developmental and pathophysiological processes, focusing on the potential role of EndMT in atherosclerosis in more depth.

Soft-shelled turtle peptide modulates microRNA profile in human gastric cancer AGS cells

Cancer prevention using natural micronutrition on epigenetic mechanisms primarily revolves around plant extracts. However, the role of macronutrition, including animal peptides, on epigenetic modification in cancer has been elusive. In traditional Chinese medicine, the soft-shelled turtle has a long-history of being a functional food that strengthens immunity through unknown mechanisms. The present study aimed to investigate the impact of soft-shelled turtle peptide on microRNA (miRNA) expression in gastric cancer (GC) cells and to analyze the potential anticancer mechanisms for GC. Affymetrix GeneChip miRNA 3.0 Array and quantitative polymerase chain reaction were used to detect the miRNA expression profile in human GC AGS cells treated with the soft-shelled turtle peptide. The results demonstrated that 101 miRNAs (49 upregulated miRNAs and 52 downregulated miRNAs) were significantly differentially expressed in the AGS cells following soft-shelled turtle peptide treatment. Several tumor suppressor miRNAs were upregulated markedly, including miRNA-375, let-7d, miRNA-429, miRNA-148a/148b and miRNA-34a. Pathway analysis indicated that soft-shelled turtle peptide may function with anticancer properties through the Hippo signaling pathway and the forkhead box O signaling pathway. Therefore, these results demonstrated that soft-shelled turtle peptide has the capacity to influence cancer-related pathways through the regulation of miRNA expression in GC cells.

Downregulation of MicroRNA-455-3p Links to Proliferation and Drug Resistance of Pancreatic Cancer Cells via Targeting TAZ

Drug resistance is a major cause of treatment failure in pancreatic cancer. The limited evidence indicates the involvement of miR-455-3p in chemotherapy resistance of cancer. Here we observed by qPCR that miR-455-3p was significantly decreased in pancreatic cancer tissues and cell lines. We then confirmed that the inhibition of miR-455-3p increased cell proliferation and gemcitabine resistance of pancreatic cancer, whereas forced overexpression of miR-455-3p had the opposite effect. Furthermore, we demonstrated that TAZ, which is associated with drug resistance of pancreatic cancer, is a new direct downstream target of miR-455-3p. Our present study suggests that miR-455-3p contributes to cell proliferation and drug resistance in pancreatic cancer cells via targeting TAZ.

Mechanobiology of YAP and TAZ in physiology and disease

A growing body of evidence suggests that mechanical signals emanating from the cell's microenvironment are fundamental regulators of cell behaviour. Moreover, at the macroscopic scale, the influence of forces, such as the forces generated by blood flow, muscle contraction, gravity and overall tissue rigidity (for example, inside of a tumour lump), is central to our understanding of physiology and disease pathogenesis. Still, how mechanical cues are sensed and transduced at the molecular level to regulate gene expression has long remained enigmatic. The identification of the transcription factors YAP and TAZ as mechanotransducers started to fill this gap. YAP and TAZ read a broad range of mechanical cues, from shear stress to cell shape and extracellular matrix rigidity, and translate them into cell-specific transcriptional programmes. YAP and TAZ mechanotransduction is critical for driving stem cell behaviour and regeneration, and it sheds new light on the mechanisms by which aberrant cell mechanics is instrumental for the onset of multiple diseases, such as atherosclerosis, fibrosis, pulmonary hypertension, inflammation, muscular dystrophy and cancer.

AJUBA increases the cisplatin resistance through hippo pathway in cervical cancer

Though LIM-domain protein AJUBA was identified as a putative oncogene, the function and underlying mechanisms of AJUBA in cervical cancer remain largely unknown. Firstly, AJUBA expression was detected via real-time quantitative PCR in patients' samples. Furthermore, Hela and Siha cells were transfected with AJUBA-overexpressing plasmids, and then exposed to cisplatin, the apoptosis was measured by cytometry assay. In addition, the expression of YAP and TAZ was disclosed through western blot assay. Our results revealed that AJUBA expression was significantly higher in the cervical cancer patients resistant to cisplatin treatment compared with cervical cancer patients sensitive to cisplatin treatment. In addition, overall survival time was significantly shorter in the cervical cancer patients with high AJUBA expression compare with those with low AJUBA expression using kaplan-meier analysis. Hela and Siha cells transfected with AJUBA-expressing plasmids exposed to cisplatin treatment had higher survival rate compared with the cells transfected with empty vector control. Mechanistic studies revealed the AJUBA upregulated the downstream targets YAP and TAZ. These results suggest that high AJUBA level enhances cervical cancer cells drug resistance to cisplatin, also associates with decreased patient survival times.

Podocalyxin-Like Protein 1 Regulates TAZ Signaling and Stemness Properties in Colon Cancer

Colon cancer is the third most common cancer in the world and the second most common cause of cancer-related mortality. Molecular biomarkers for colon cancer have undergone vigorous discovery and validation. Recent studies reported that overexpression of podocalyxin-like protein 1 (PODXL) is associated with distant metastasis and poor prognosis across several types of malignancies. Its role and underlying molecular mechanism, however, are not yet fully understood. In the present study, we revealed that the Hippo transducer, the transcriptional coactivator with PDZ-binding motif (TAZ), acts as a downstream mediator of PODXL in colon cancer. Inhibition of PODXL resulted in the suppression of TAZ signaling and the downregulation of Hippo downstream genes. Moreover, PODXL plays a critical role in cancer stemness, invasiveness, and sensitivity to chemotherapies in colon cancer HCT15 cells. Notably, expression of PODXL showed a positive correlation with stem-like and epithelial-mesenchymal transition (EMT) core signatures, and was associated with poor survival outcomes in patients with colon cancer. These findings provide novel insights into the molecular mechanism of PODXL-mediated tumorigenesis in colon cancer.

Verteporfin inhibits growth of human glioma in vitro without light activation

Verteporfin (VP), a light-activated drug used in photodynamic therapy for the treatment of choroidal neovascular membranes, has also been shown to be an effective inhibitor of malignant cells. Recently, studies have demonstrated that, even without photo-activation, VP may still inhibit certain tumor cell lines, including ovarian cancer, hepatocarcinoma and retinoblastoma, through the inhibition of the YAP-TEAD complex. In this study, we examined the effects of VP without light activation on human glioma cell lines (LN229 and SNB19). Through western blot analysis, we identified that human glioma cells that were exposed to VP without light activation demonstrated a downregulation of YAP-TEAD-associated downstream signaling molecules, including c-myc, axl, CTGF, cyr61 and survivin and upregulation of the tumor growth inhibitor molecule p38 MAPK. In addition, we observed that expression of VEGFA and the pluripotent marker Oct-4 were also decreased. Verteporfin did not alter the Akt survival pathway or the mTor pathway but there was a modest increase in LC3-IIB, a marker of autophagosome biogenesis. This study suggests that verteporfin should be further explored as an adjuvant therapy for the treatment of glioblastoma.

Emerging role of Hippo signalling pathway in bladder cancer

Bladder cancer (BC) is one of the most common cancers worldwide with a high progression rate and poor prognosis. The Hippo signalling pathway is a conserved pathway that plays a crucial role in cellular proliferation, differentiation and apoptosis. Furthermore, dysregulation and/or malfunction of the Hippo pathway is common in various human tumours, including BC. In this review, an overview of the Hippo pathway in BC and other cancers is presented. We focus on recent data regarding the Hippo pathway, its network and the regulation of the downstream co-effectors YAP1/TAZ. The core components of the Hippo pathway, which induce BC stemness acquisition, metastasis and chemoresistance, will be emphasized. Additional research on the Hippo pathway will advance our understanding of the mechanism of BC as well as the development and progression of other cancers and may be exploited therapeutically.

Hippo pathway contributes to cisplatin resistant-induced EMT in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a kind of head-neck malignant tumor derived from the nasopharyngeal epithelium and is mainly prevalent in Southern China and Southeast Asia countries. Cisplatin (DDP) provides the first-line therapeutic administration in NPC patients. However, chemoresistance has been a main barrier and caused bad treatment outcome in NPC therapy. To understand the molecular mechanism of acquired resistance to DDP, multiple methods were performed to examine the morphocytology and molecular changes in DDP-resistant NPC cells. We found that drug resistance cells displayed epithelial-mesenchymal transition (EMT) characteristics. DDP-resistant NPC cells exhibited enhanced migration and invasion potential. Moreover, overexpression of TAZ, one key gene in Hippo pathway, is closely associated with the DDP resistance of NPC cells and its EMT properties. Depletion of TAZ in DDP-resistant cells reversed EMT phenotypes to MET characteristics and restored chemosensitivity of DDP-resistant cells to DDP treatment. These results suggest that inactivation of TAZ could be a promising approach for the treatment of NPC patients.

RNA-binding protein Dnd1 inhibits epithelial-mesenchymal transition and cancer stem cell-related traits on hepatocellular carcinoma cells

OBJECTIVES

To investigate the roles of Dead end 1 (Dnd1) in modulating cancer stem cell-related traits of hepatocellular carcinoma (HCC).

RESULTS

Dead end (Dnd1) inhibited spheroid formation, suppressed the expression of stemness-related genes, and increased sensitivity to sorafenib in HCC cells. Mechanistically, Dnd1 could bind to 3'-UTR of LATS2, the key kinase of Hippo pathway, thus elevating LATS2 mRNA stability and its expression, subsequently leading to phosphorylation of YAP and its cytoplasmic retention. As a result, epithelial-mesenchymal transition (EMT) was weakened and therefore the generation of HCC stem cell properties was suppressed.

CONCLUSIONS

Dnd1 functions as a tumor suppressor by prohibiting CSC-like characteristics via activating Hippo pathway in HCC cells. Dnd1 could thus be a novel therapeutic target for HCC patients.

Expression of YAP/TAZ in Keratocystic Odontogenic Tumors and Its Possible Association with Proliferative Behavior

The aim of this study is to clarify whether YAP/TAZ is involved in the pathogenesis and proliferative growth of keratocystic odontogenic tumor (KCOT). The expression levels of YAP/TAZ and downstream proteins and genes in normal oral mucosa (OM) and KCOT were determined and compared by immunohistochemistry and real-time quantitative PCR. The results showed that the expression of YAP/TAZ and downstream proteins (Cyr61, CTGF) was significantly upregulated in KCOT with upregulation of Ki-67 compared to OM. Importantly, the mRNA levels of transcription factors (TEAD1, TEAD4, and RUNX2) and cell cycle related genes (CDK2, PCNA), which interact with the transcriptional coactivators YAP/TAZ, are also upregulated in the KCOT. In addition, the results from Spearman rank correlation test revealed the close relationship between YAP/TAZ and Ki-67, which was further evidenced by double-labelling immunofluorescence that revealed a synchronous distribution for YAP/TAZ with Ki-67 in KCOT samples. All the data suggested YAP/TAZ might be involved in the proliferative behavior of KCOT.

TAZ overexpression is associated with epithelial-mesenchymal transition in cisplatin-resistant gastric cancer cells

Gastric cancer is one of the common malignant diseases. The poor treatment outcome is mainly due to chemotherapeutic resistance. Therefore, it is important to determine the molecular mechanism of drug resistance in gastric cancer. To explore the mechanisms of cisplatin resistance in gastric cancer cells, several approaches were performed including MTT assay, real-time RT-PCR, western blot analysis, migration and invasion assays, wound healing assay, and transfection. We found that cisplatin-resistant (CR) gastric cancer cells acquired epithelial-mesenchymal transition (EMT) phenotype. The CR cells with EMT features obtained higher migratory and invasive activities. Moreover, we observed that TAZ was highly expressed in CR cells. Consistently, depletion of TAZ caused partial reversal of EMT to MET in CR cells. Our results suggest that TAZ plays a pivotal role in CR-induced EMT. Targeting TAZ could be a potential therapeutic strategy for gastric cancer.

The level and clinical significance of 5-hydroxymethylcytosine in oral squamous cell carcinoma: An immunohistochemical study in 95 patients

Accumulating evidence has revealed that aberrant abundance of 5-hydroxymethylcytosine (5hmC) is critically involved in tumorigenesis. The aim of the present study was to investigate the level of 5hmC in primary oral squamous cell carcinoma (OSCC) and determine its clinical significance as well as prognostic value in predicting patients' outcomes. The expression levels of 5hmC in 95 human OSCC samples and 24 normal oral mucosa were evaluated by immunohistochemical staining. Moreover, the associations between the expression status of 5hmC and several clinicopathological parameters as well as patients' survival were further statistically assessed. Our immunohistochemical results revealed that 5hmC was significantly downregulated in a significant fraction of OSCC as compared their normal counterparts. However, elevated 5hmC level was found to be significantly associated with pathological grade and cervical node metastasis with P-values of 0.0239 and 0.0041, respectively. Results from Kaplan-Meier cumulative survival analyses indicated that high expression of 5hmC in OSCC was significantly associated with decreased overall survival, disease-free and disease-specific survival as compared to those with low 5hmC (Log-rank, P=0.0210, 0.0313, 0.0415, respectively). Furthermore, the univariate and multivariate survival analyses further identified the expression status of 5hmC as an independent prognostic factor affecting patients' survival. Taken together, our results reveal a significant decrease of 5hmC level in a large subset of OSCC. However, high level of 5hmC associates with tumor aggressive features and unfavorable prognosis in a fraction of OSCC patients.

Targeting mutant p53 in cancer: a long road to precision therapy

The TP53 tumor suppressor is the most frequently mutated gene in human cancers. In recent years, a blooming of research efforts based on both cell lines and mouse models have highlighted how deeply mutant p53 proteins affect fundamental cellular pathways with cancer-promoting outcomes. Neomorphic mutant p53 activities spread over multiple levels, impinging on chromatin structure, transcriptional regulation and microRNA maturation, shaping the proteome and the cell's metabolic pathways, and also exerting cytoplasmic functions and displaying cell-extrinsic effects. These tumorigenic activities are inextricably linked with the blend of highly corrupted processes that characterize the tumor context. Recent studies indicate that successful strategies to extract core aspects of mutant p53 oncogenic potential and to identify unique tumor dependencies entail the superimposition of large-scale analyses performed in multiple experimental systems, together with a mindful use of animal models. This will hopefully soon lead to the long-awaited inclusion of mutant p53 as an actionable target of clinical antitumor therapies.

Hippo transducer TAZ promotes epithelial mesenchymal transition and supports pancreatic cancer progression

Transcriptional co-activator with PDZ binding motif (TAZ) is a transducer of the Hippo pathway and promotes cancer development and progression. In the present study, we sought to determine the roles and underlying mechanisms of elevated expression and activation of TAZ in pancreatic cancer development and progression. The mechanistic role of TAZ and Hippo signaling in promotion of pancreatic cancer development and progression was examined using cell culture, molecular biology, and mouse models. The relevance of our experimental and mechanistic findings was validated using human pancreatic tumor specimens. We found that TAZ expression was markedly higher in pancreatic tumors than in normal pancreatic tissue. Further analysis of the correlation of TAZ expression with tissue microarray clinicopathologic parameters revealed that this expression was positively associated with tumor differentiation. Also, TAZ expression was higher in pancreatic cancer cell lines than in pancreatic ductal epithelial cells. TAZ activation in pancreatic cancer cells promoted their proliferation, migration, invasion, and epithelial-mesenchymal transition. Further mechanistic studies demonstrated that aberrant expression and activation of TAZ in pancreatic cancer cells resulted from suppression of the expression of Merlin, a positive regulator upstream of the Hippo pathway, and that the oncogenic function of TAZ in pancreatic cancer cells was mediated by TEA/ATTS domain transcription factors. Therefore, TAZ functioned as an oncogene and promoted pancreatic cancer epithelial-mesenchymal transition and progression. TAZ thus may be a target for effective therapeutic strategies for pancreatic cancer.

The 2016 John J. Abel Award Lecture: Targeting the Mechanical Microenvironment in Cancer

Past decades of cancer research have mainly focused on the role of various extracellular and intracellular biochemical signals on cancer progression and metastasis. Recent studies suggest an important role of mechanical forces in regulating cellular behaviors. This review first provides an overview of the mechanobiology research field. Then we specially focus on mechanotransduction pathways in cancer progression and describe in detail the key signaling components of such mechanotransduction pathways and extracellular matrix components that are altered in cancer. Although our understanding of mechanoregulation in cancer is still in its infancy, some agents against key mechanoregulators have been developed and will be discussed to explore the potential of pharmacologically targeting mechanotransduction in cancer.

Prognostic significance of TAZ expression in various cancers: a meta-analysis

Background

The overexpression of transcriptional coactivator with PDZ-binding motif (TAZ), a Hippo pathway effector, was detected in a variety of cancers. However, controversies remain in published studies on the prognostic value of TAZ expression in cancer. We performed a meta-analysis to demonstrate the prognostic significance of TAZ in overall survival (OS) and its association with clinicopathologic characteristics.

Methods

A systematic literature search was performed by using PubMed, EMBASE, and Web of Science databases for eligible studies investigating the association between TAZ and survival. After extracting data, we used hazard ratio (HR), odds ratio (OR) and 95% confidence intervals (95% CIs) for association evaluation, I² for heterogeneity across studies, and Egger’s test and Begg’s funnel plot for publication bias assessment.

Results

A total of 15 studies including 2,881 patients were analyzed. Pooled results showed that a high TAZ was significantly associated with poor OS (HR =1.82, 95% CI =1.58–2.11; I²=33%; P=0.11). Subgroup analysis indicated significant correlation between TAZ overexpression and OS in patients stratified by ethnicity, sample size, sample source, and staining location. Furthermore, TAZ overexpression was associated with worse OS in hepatocellular carcinoma (HR =2.26, 95% CI =1.43–3.57; P=0.49) and gastrointestinal cancers (HR =2.00, 95% CI =1.54–2.58; P=0.97), but not in non-small-cell lung cancer (HR =1.71, 95% CI =0.93–3.14; P=0.08). TAZ overexpression was also found to be significantly associated with some clinicopathologic characteristics, including TNM stage (OR =2.56, 95% CI =1.60–4.11; P=0.52), tumor differentiation (OR =3.08, 95% CI =1.25–7.63; P=0.01), and lymph node metastasis (OR =2.53, 95% CI =1.81–3.53; P=0.58).

Conclusion

TAZ overexpression is not only a predictive factor of poor prognosis but also associated with advanced TNM stage, poor tumor differentiation, and lymph node metastasis.

CDK1 phosphorylation of TAZ in mitosis inhibits its oncogenic activity

The transcriptional co-activator with PDZ-binding motif (TAZ) is a downstream effector of the Hippo tumor suppressor pathway, which plays important roles in cancer and stem cell biology. Hippo signaling inactivates TAZ through phosphorylation (mainly at S89). In the current study, we define a new layer of regulation of TAZ activity that is critical for its oncogenic function. We found that TAZ is phosphorylated in vitro and in vivo by the mitotic kinase CDK1 at S90, S105, T326, and T346 during the G2/M phase of the cell cycle. Interestingly, mitotic phosphorylation inactivates TAZ oncogenic activity, as the non-phosphorylatable mutant (TAZ-S89A/S90A/S105A/T326A/T346A, TAZ-5A) possesses higher activity in epithelial-mesenchymal transition, anchorage-independent growth, cell migration, and invasion when compared to the TAZ-S89A mutant. Accordingly, TAZ-5A has higher transcriptional activity compared to the TAZ-S89A mutant. Finally, we show that TAZ-S89A or TAZ-5A (to a greater extent) was sufficient to induce spindle and centrosome defects, and chromosome misalignment/missegregation in immortalized epithelial cells. Together, our results reveal a previously unrecognized connection between TAZ oncogenicity and mitotic phospho-regulation.

Regulation of TAZ in cancer

TAZ, a transcriptional coactivator with PDZ-binding motif, is encoded by WWTR1 gene (WW domain containing transcription regulator 1). TAZ is tightly regulated in the hippo pathway-dependent and -independent manner in response to a wide range of extracellular and intrinsic signals, including cell density, cell polarity, F-actin related mechanical stress, ligands of G protein-coupled receptors (GPCRs), cellular energy status, hypoxia and osmotic stress. Besides its role in normal tissue development, TAZ plays critical roles in cell proliferation, differentiation, apoptosis, migration, invasion, epithelial-mesenchymal transition (EMT), and stemness in multiple human cancers. We discuss here the regulators and regulation of TAZ. We also highlight the tumorigenic roles of TAZ and its potential therapeutic impact in human cancers.

YAP/TAZ at the Roots of Cancer

YAP and TAZ are highly related transcriptional regulators pervasively activated in human malignancies. Recent work indicates that, remarkably, YAP/TAZ are essential for cancer initiation or growth of most solid tumors. Their activation induces cancer stem cell attributes, proliferation, chemoresistance, and metastasis. YAP/TAZ are sensors of the structural and mechanical features of the cell microenvironment. A number of cancer-associated extrinsic and intrinsic cues conspire to overrule the YAP-inhibiting microenvironment of normal tissues, including changes in mechanotransduction, inflammation, oncogenic signaling, and regulation of the Hippo pathway. Addiction to YAP/TAZ thus potentially represents a central cancer vulnerability that may be exploited therapeutically.

YAP/TAZ as therapeutic targets in cancer

The biology and regulation of YAP and TAZ, two closely related transcriptional regulators, are receiving increasing attention owing to their fundamental roles in organ growth, tissue repair and cancer. In particular, the widespread activation of YAP/TAZ in carcinomas, and the crucial role of YAP/TAZ activation for many 'hallmarks' of cancer are indicating YAP/TAZ as prime targets for designing anti-cancer drugs. Here, we start from the known modalities to regulate YAP/TAZ to highlight possible routes of therapeutic intervention.

Phosphodiesterase 5/protein kinase G signal governs stemness of prostate cancer stem cells through Hippo pathway

Cancer stem cells (CSC) are critical for initiation, metastasis, and relapse of cancers, however, the underlying mechanism governing stemness of CSC remains unknown. Herein, we have investigated the roles of phosphodiesterase 5 (PDE5) in stemness of prostate cancer cells. Both PDE5 and WW domain-containing transcription regulator protein-1 (TAZ), a core effector of Hippo pathway, are highly expressed in the PC3-derived cancer stem cells (PCSC). Either TAZ knockdown or inhibition of PDE5 activity attenuated colony formation, altered expression patterns of stem cell markers, and enhanced cisplatin cytotoxicity, resulting in attenuation of stemness in PCSC. In addition, inhibition of PDE5 activity by its specific inhibitors activates cGMP-dependent protein kinase G (PKG), which in turn induces MST/LATS kinases, resulting in cytosolic degradation of TAZ and activation of Hippo pathway. Accordingly, knockdown of TAZ almost completely abolished PDE5 inhibitor-induced attenuation in stemness in cultured PCSC, whereas knockdown of TAZ not only abolished PDE5 inhibitor-induced attenuation in stemness but also facilitated PDE5 inhibitor-induced trans-differentiation in PCSC xenografts. Together, the present study has uncovered that PDE/cGMP/PKG signal targets to Hippo/TAZ pathway in maintaining stemness of PCSC, and suggested that PDE5 inhibitors in combination with chemotherapeutic agents could effectively prevent initiation, metastasis, and relapse of prostate cancer.

The histone demethylase LSD1 is a novel oncogene and therapeutic target in oral cancer

The histone demethylase LSD1 functions as a key pro-oncogene and attractive therapeutic target in human cancer. Here we sought to interrogate the oncogenic roles of LSD1 in OSCC tumorigenesis and therapeutic intervention by integrating chemical-induced OSCC model, genetic and pharmacological loss-of-function approaches. Our data revealed that aberrant LSD1 overexpression in OSCC was significantly associated with tumor aggressiveness and shorter overall survival. Increased abundance of LSD1 was detected along with disease progression in DMBA- or 4NQO-induced OSCC animal models. LSD1 depletion via siRNA-mediated knockdown in OSCC cells resulted in impaired cell proliferation, migration/invasion, tumorsphere formation and reduced xenograft growth while inducing cell apoptosis and enhancing chemosensitivity to 5-FU. Moreover, treatments of LSD1 chemical inhibitors (pargyline and tranylcypromine) induced its protein reduction probably via enhanced protein degradation and produced similar phenotypic changes resembling LSD1 silencing in OSCC cells. Pharmacological inhibition of LSD1 by intraperitoneal delivery of these inhibitors resulted in impaired xenograft overgrowth. Taken together, our data reveal the tumorigenic roles of LSD1 and identified LSD1 as a novel biomarker with diagnostic and prognostic significance, and also establish that targeting LSD1 by chemical inhibitors is a viable therapeutic strategy against OSCC.

The pluripotency factor LIN28B is involved in oral carcinogenesis and associates with tumor aggressiveness and unfavorable prognosis

Objective

LIN28B is a conserved RNA-binding protein critically involved in development, cellular metabolism and tumorigenesis. It is frequently overexpressed in human cancers and correlates with tumor aggressiveness as well as unfavorable prognosis. However, the expression pattern and oncogenic roles of LIN28B during oral squamous cell carcinoma (OSCC) development and progression has not been well established yet. Here, we sought to determine the expression of LIN28B and its clinical significance using chemical-induced OSCC animal model, cell lines and primary specimens.

Method

The OSCC animal model was induced using 7,12-dimethyl-1,2-bezan-tracene (DMBA) painting in the hamster buccal pouch. Buccal lesions from animals were obtained from different time points and subjected to routine histological analyses and immunohistochemical staining of LIN28B. The mRNA, protein abundance and subcellular localization of LIN28B was determined in a panel of OSCC cell lines by real-time RT-PCR, western blot and immunofluorescence. The expression levels of LIN28B in human primary OSCC samples were further evaluated by immunohistochemical staining. Moreover, the relationship between LIN28B and several clinicopathological parameters as well as patients’ prognosis were also assessed.

Results

Our results revealed that negative or low LIN28B expression was commonly observed in normal epithelial, whereas more LIN28B abundance was identified in epithelial dysplasia and invasive SCC in the DMBA-induced OSCC animal model. Overexpression of LIN28B was identified in a major fraction of OSCC samples(39/58) and significantly associated with tumor size (P = 0.049) and advanced clinical stages (P = 0.0286). Patients with increased LIN28B had markedly reduced overall survival as compared to those with low LIN28B. Multivariate survival analyses further indicated that LIN28B abundance served as an independent prognostic factor for patients’ overall survival.

Conclusions

Our findings reveal that LIN28B is critically involved in OSCC initiation and progression and aberrantly overexpressed in human OSCC. It might represent a novel diagnostic and prognostic biomarker for oral cancer.

High expression of TAZ indicates a poor prognosis in retinoblastoma

BACKGROUND

The transcriptional co-activator, TAZ, is an important effector of the Hippo pathway and is critical for the development of human cancers. However, the expression and prognostic significance of TAZ in retinoblastoma is currently unclear.

METHODS

TAZ expression was examined in 43 retinoblastoma samples by immunohistochemistry. The relationship between TAZ expression and the clinicopathological features of retinoblastoma was also analyzed. Cox regression and Kaplan-Meier survival analyses were used to identify the prognostic factors for retinoblastoma patients. Finally, the effects of TAZ on cell proliferation were explored through lentivirus-mediated downregulation of TAZ in retinoblastoma cells.

RESULTS

TAZ was highly expressed in retinoblastoma tissues and was associated with regional lymph node classification (P = 0.013), largest tumor base (P = 0.045), and differentiation (P = 0.019). Moreover, patients with high TAZ expression had shorter overall survival (OS), progression-free survival (PFS), loco-regional relapse-free survival (LRRFS), and distant metastasis-free survival (DMFS) time than patients with low TAZ expression (P < 0.05). Multivariate analysis showed that high TAZ expression was an important prognostic factor for retinoblastoma patients. In addition, downregulation of TAZ expression significantly suppressed tumor cell proliferation by blocking the transition of the cell cycle from G1 to S phase.

CONCLUSIONS

Our findings suggest that the high expression of TAZ plays a significant role in retinoblastoma's aggressiveness, and predicts poor prognosis for patients with retinoblastoma.

Molecular Pathways: Hippo Signaling, a Critical Tumor Suppressor

The Salvador-Warts-Hippo pathway controls cell fate and tissue growth. The main function of the Hippo pathway is to prevent YAP and TAZ translocation to the nucleus where they induce the transcription of genes involved in cell proliferation, survival, and stem cell maintenance. Hippo signaling is, thus, a complex tumor suppressor, and its deregulation is a key feature in many cancers. Recent mounting evidence suggests that the overexpression of Hippo components can be useful prognostic biomarkers. Moreover, Hippo signaling appears to be intimately linked to some of the most important signaling pathways involved in cancer development and progression. A better understanding of the Hippo pathway is thus essential to untangle tumor biology and to develop novel anticancer therapies. Here, we comment on the progress made in understanding Hippo signaling and its connections, and also on how new drugs modulating this pathway, such as Verteporfin and C19, are highly promising cancer therapeutics.

TAZ promotes temozolomide resistance by upregulating MCL-1 in human glioma cells

Temozolomide is a novel cytotoxic agent currently used as first-line chemotherapy for glioblastoma multiforme (GBM). However, intrinsic or acquired chemoresistance to temozolomide remains the greatest obstacle to the successful treatment of human GBM. The principal mechanism responsible for this resistance is largely unknown. In the present study, we showed that expression of transcriptional co-activator with PDZ-binding motif (TAZ) in glioma cells correlated with temozolomide chemoresistance in human glioma cells. Overexpression of TAZ promoted temozolomide resistance in U-87MG cells, whereas knockdown of TAZ expression sensitized temozolomide-resistant U-251MG cells to temozolomide. Further, TAZ inhibits temozolomide induced apoptosis via upregulation of MCL-1 (myeloid cell leukemia 1) and high expression of TAZ predicts a poor prognosis for GBM patients. In conclusion, our results suggest that TAZ had a critical role in the resistance to temozolomide in glioma cells, and it may provide a promising target for improving the therapeutic outcome of temozolomide-resistant gliomas.

The Hippo transducer TAZ promotes epithelial to mesenchymal transition and cancer stem cell maintenance in oral cancer

The Hippo pathway has emerged as a fundamental regulator in tissue growth, organ size and stem cell functions, and tumorigenesis when deregulated. However, its roles and associated molecular mechanisms underlying oral squamous cell carcinoma (OSCC) initiation and progression remain largely unknown. Here, we identified TAZ, the downstream effector of Hippo signaling, as a novel bona fide oncogene by promoting cell proliferation, migration/invasion and chemoresistance in OSCC. TAZ promoted epithelial-to-mesenchymal transition (EMT) and also was involved in TGF-β1-induced EMT in oral cancer cells. Furthermore, enriched TAZ sustained self-renewal, maintenance, tumor-seeding potential of oral cancer stem cells (CSCs). Remarkably, enforced TAZ overexpression conferred CSCs-like properties on differentiated non-CSCs and fueled phenotypic transition from non-CSCs to CSCs-like cells. Mechanistically, TAZ-TEADs binding and subsequent transcriptional activation of EMT mediators and pluripotency factors are presumably responsible for TAZ-mediated EMT and non-CSCs-to-CSCs conversion. Importantly, aberrant TAZ overexpression was found to be associated with tumor size, pathological grade and cervical lymph node metastasis, as well as unfavorable prognosis. Pharmacological repression of TAZ by simvastatin resulted in potent anti-cancer effects against OSCC. Taken together, our findings have revealed critical links between TAZ, EMT and CSCs in OSCC initiation and progression, and also established TAZ as a novel cancer biomarker and viable druggable target for OSCC therapeutics.