High TAZ Expression Research Articles

Transcriptomics analysis revealed that TAZ regulates the proliferation of KIRC cells through mitophagy.

Transcriptional Co-Activator with PDZ-Binding Motif (TAZ, also known as WWTR1) is a downstream effector of the Hippo pathway, involved in the regulation of organ regeneration and cell differentiation in processes such as development and regeneration. TAZ has been shown to play a tumor-promoting role in various cancers. Currently, many studies focus on the role of TAZ in the process of mitophagy. However, the molecular mechanism and biological function of TAZ in renal clear cell carcinoma (KIRC) are still unclear. Therefore, we systematically analyzed the mRNA expression profile and clinical data of KIRC in The Cancer Genome Atlas (TCGA) dataset. We found that TAZ expression was significantly upregulated in KIRC compared with normal kidney tissue and was closely associated with poor prognosis of patients. Combined with the joint analysis of 36 mitophagy genes, it was found that TAZ was significantly negatively correlated with the positive regulators of mitophagy. Finally, our results confirmed that high expression of TAZ in KIRC inhibits mitophagy and promotes KIRC cell proliferation. In conclusion, our findings reveal the important role of TAZ in KIRC and have the potential to be a new target for KIRC therapy.

An indispensable role of TAZ in anoikis resistance promoted by OTUB1 deubiquitinating enzyme in basal-like triple-negative breast cancer cells

Aggressive cancers, such as triple-negative breast cancer (TNBC), are mostly fatal because of their potential to metastasize to distant organs. Cancer cells acquire various abilities to metastasize, including resistance to anoikis, an apoptotic cell death induced by loss of anchorage to the extracellular matrix. Transcriptional coactivator with PDZ binding motif (TAZ) and Yes-associated protein (YAP), the downstream effectors of the Hippo pathway, regulate cell- and tissue-level architectures by responding to mechanical microenvironments of cells, including the cell–extracellular matrix interaction. The Hippo pathway is frequently disrupted in cancer cells, and TAZ and YAP are irrelevantly activated, potentially resulting in anchorage-independent survival/proliferation of cancer cells and metastatic progression. The study aims to investigate the roles of TAZ and YAP in anoikis resistance in basal-like (BL) TNBC cells, which comprise a major subtype (>70%) of TNBC. We found that TAZ and YAP had nonredundant roles in anchorage-independent cancer cell survival or anoikis resistance. Particularly, TAZ was indispensable for anoikis resistance in BL-TNBC cells but not for survival of non-transformed mammary epithelial cells (MECs). In contrast, YAP, a paralog of TAZ, was indispensable for survival of both non-transformed MECs and cancer cells. Therefore, TAZ might be a preferable therapeutic target against dissemination of aggressive cancer cells without killing normal cells. Interestingly, TAZ was abnormally stabilized in BL-TNBC cells under non-adherent conditions, which promoted anoikis resistance. Furthermore, OTUB1, a deubiquitinating enzyme, was responsible for the stabilization of TAZ in detached BL-TNBC cells. Importantly, simultaneous high expression of TAZ and OTUB1 was associated with poor prognosis in BC. Thus, OTUB1 has emerged as a potentially druggable target. Successful inhibition of OTUB1 enzymatic activity is expected to downregulate TAZ and eventually prevents metastasis of aggressive cancers, such as BL-TNBC.

The Hippo Signaling Core Components YAP and TAZ as New Prognostic Factors in Lung Cancer

BackgroundThe Hippo pathway is an essential signaling cascade that regulates cell and organ growth. However, there is no consensus about (i) the expression levels of the Hippo signaling core components yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) in lung cancer, especially in small cell lung cancer (SCLC), or (ii) their association with the prognosis of patients with SCLC.MethodsWe screened relevant articles and identified eligible studies in the PubMed, EMBASE, COCHRANE, and WanFang databases. A combined analysis was performed to investigate (i) the expression levels of the major effectors, YAP and TAZ, in lung cancer and its subsets and (ii) their prognostic role in lung cancer, especially in SCLC.ResultsIn total, 6 studies related to TAZ and 13 studies concerning YAP were enrolled in this meta-analysis. We found that high TAZ expression was significantly associated with poor overall survival (OS) of patients with non-small cell lung cancer (NSCLC) in the overall population [Ph < 0.001, crude hazard ratio (HR) = 1.629, 95% CI = 1.199–2.214 for TAZ expression; Ph = 0.029, adjusted HR = 2.127, 95% CI = 1.307–3.460 for TAZ], the Caucasian population (Ph = 0.043, crude HR = 1.233, 95% CI = 1.030–1.477 for TAZ expression), and the Asian population (Ph = 0.551, adjusted HR = 2.676, 95% CI = 1.798–3.982 for TAZ). Moreover, there was a significant negative association between YAP expression and an unsatisfactory survival of patients with lung cancer (Ph = 0.327, crude HR = 1.652, 95% CI = 1.211–2.253 for YAP expression) and patients with NSCLC [disease-free survival (DFS): Ph = 0.693, crude HR = 2.562, 95% CI = 1.876–3.499 for YAP expression; Ph = 0.920, crude HR = 2.617, 95% CI = 1.690–4.052 for YAP-mRNA; OS: Ph = 0.878, crude HR = 1.777, 95% CI = 1.233–2.562 for YAP expression], especially in the Asian population (DFS: Ph = 0.414, crude HR = 2.515, 95% CI = 1.755–3.063; OS: Ph = 0.712, crude HR = 1.772, 95% CI = 1.214–2.587). However, no association was observed in the multivariate combined analysis. High YAP expression was significantly associated with short OS of patients with SCLC in our combined multivariate analysis in the Asian population (Ph = 0.289, crude HR = 4.482, 95% CI = 2.182–9.209), but not with crude data (Ph = 0.033, crude HR = 1.654, 95% CI = 0.434–6.300).ConclusionThe Hippo pathway is involved in carcinogenesis and progression of NSCLC and SCLC, and high expression levels of YAP and TAZ are independent and novel prognostic factors for lung cancer.

Increased expression of TAZ and associated upregulation of PD-L1 in cervical cancer

BackgroundAs an important component of the Hippo pathway, WW domain-containing transcription regulator 1 (TAZ), is a transcriptional coactivator that is responsible for the progression of various types of cancers. Programmed cell death protein 1 (PD-1) receptors in activated T cells and their ligand programming death force 1 (PD-L1) are the main checkpoint signals that control T cell activity. Studies have shown high levels of PD-L1 in various cancers and that PD-L1/PD-1 signals to evade T-cell immunity. Recent data have demonstrated that TAZ can regulate the characteristics of cancer cells via PD-L1. Cervical cancer is a common gynecological disease worldwide. In this study, we attempted to evaluate the effects of TAZ and PD-L1 on cervical cancer.MethodsHela cervical cancer cells were transfected with TAZ plasmid or TAZ siRNA or PD-L1 siRNA by using Lipofectamine 2000. The relationship between TAZ and PD-L1 in cervical cancer cells was determined by qRT-PCR and western blotting. The functional roles of TAZ were confirmed via CCK-8, Transwell and flow cytometry assays. Western blotting was utilized to observe the expression of BCL-2 and Caspase-3. The clinicopathological correlation of TAZ and PD-L1 was evaluated via relevant databases.ResultTAZ is upregulated in cervical cancer and induces the growth and metastasis of cervical cancer cells by targeting PD-L1and inhibiting the ratio of apoptotic of cancer cells. High TAZ and PD-L1 expression was observed in different stage, grade, histological patterns, and ages of cervical cancer groups compared with normal cervix groups. Furthermore, high TAZ expression was positively correlated with the infiltration levels of immune cells and the expression of PD-L1.

Abstract B04: Hepatic cholesterol upregulates TAZ in nonalcoholic steatohepatitis

Abstract Nonalcoholic steatohepatitis (NASH) has emerged as the leading cause of chronic liver disease worldwide and is rapidly increasing in prevalence owing to the obesity epidemic. Incomplete understanding of the mechanisms of NASH progression, particularly fibrosis, has limited the design of therapeutic strategies. My previous published study indicated that a transcription factor in hepatocytes called TAZ (WWTR1) contributes to steatosis-to-NASH progression. However, the mechanism that induces high TAZ expression in NASH liver remains unknown. The objective of this study is to understand the mechanism of hepatocyte TAZ upregulation in NASH, which may suggest novel therapeutic strategies to prevent NASH and its comorbidities. We hypothesize that hepatic cholesterol upregulates TAZ through PKA-Ca2+-RhoA mediated Hippo pathway inactivation. In vitro, we use liposome to deplete and replete cholesterol in hepatocyte cells and check downstream signaling pathway that includes cholesterol translocation, Ca2+ signaling, RhoA activity, Hippo pathway, and E3 ligase activity. In vivo, we used different concentration cholesterol diet to build the correlation between increased TAZ/liver fibrosis and cholesterol, and AAV8-H1 mediated hepatic-gene silencing to prove the functions of the molecules in the pathway, including AsterB/C, RhoA, and Trcp. My data suggest that hepatic cholesterol accumulation is associated with liver fibrosis and increased TAZ. In addition, cholesterol loading of hepatocytes increases TAZ, and cholesterol depletion decreases TAZ in a proteasome/Trcp-dependent manner. Mechanistically, Hippo pathway kinase-Lats2 inhibits TAZ expression on the post-transcriptional level through TAZ phosphorylation. Moreover, intracellular cholesterol increases cytosolic Ca2+ and activates RhoA signaling, then represses Lats2 activity, so TAZ degradation is inhibited and total protein level increases. Finally, blocking cholesterol translocation from cell membrane to intracellular suppresses the pathway and inhibits TAZ level. We conclude that hepatic cholesterol induces high-level TAZ in NASH through PKA-Ca2+-RhoA mediated Hippo pathway inactivation, and cholesterol transportation plays an important role during this process. These data provide a plausible mechanism underlying liver cholesterol as a risk factor for NASH fibrosis and suggest new therapeutic interventions to block NASH fibrosis and to prevent NASH-associated HCC. Citation Format: Xiaobo Wang, Arun Radhakrishnan, Douglas Covey, Jay Horton, Robert Schwabe, Peter Tontonoz, Kun-Liang Guan, Ira Tabas. Hepatic cholesterol upregulates TAZ in nonalcoholic steatohepatitis [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B04.

TAZ functions as a tumor suppressor in multiple myeloma by downregulating MYC

AbstractMultiple myeloma (MM) is an incurable blood cancer that is often characterized by amplification and overexpression of the MYC oncogene. Despite efforts, direct targeting of MYC is not yet possible; therefore, alternative strategies to inhibit MYC activity are necessary. TAZ is a transcriptional coactivator downstream of the Hippo-signaling pathway that functions as an oncogene in many solid tumors. However, its role in hematological malignancies is largely unexplored. Here, we show that, in contrast to solid tumors, expression of TAZ is lower in hematological malignancies, and that high expression of TAZ correlates with better patient outcomes. We further show that TAZ is hypermethylated in MM patient samples and in a panel of MM cell lines. Genetic overexpression of TAZ or pharmacological upregulation of TAZ by treatment with the demethylating agent decitabine induces apoptosis. Importantly, TAZ-induced apoptosis is independent of canonical Hippo components LATS1 or the TEA-domain family of transcription factors. Instead, RNA-sequencing analysis revealed that overexpression of TAZ represses a MYC transcriptional program and we show that increased TAZ expression correlates with decreased MYC expression in both cell-line models and patient samples. Furthermore, promoter derepression of TAZ expression sensitizes MM cell lines through a reciprocal reduction in MYC expression using additional therapeutics such as bortezomib, trichostatin A, and panobinostat. Our findings uncover an unexpected role for TAZ in MM tumorigenesis and provide a compelling rationale for exploring the therapeutic potential of upregulating TAZ expression to restore sensitivity to specific therapeutics in MM.

High expression of TAZ serves as a novel prognostic biomarker and drives cancer progression in renal cancer

Renal cell carcinomas are a group of most common renal malignancies whose clinical intervention is complicated by the lack of early diagnosis and reliable prognosis biomarkers, insensitive radiotherapy and chemotherapy and expensive molecular-targeted drugs. Transcriptional coactivator TAZ has been implicated in the formation and development of various malignancies. However, the biological characteristics and function of TAZ in renal cell carcinoma are still unclear. We attempted to evaluate the potential of TAZ as a promising diagnostic and prognostic molecular marker for renal cell carcinoma. In our study, we confirmed that TAZ was frequently elevated in renal cancer tissues and cells, consistent with the results of the publicly available cancer database. Moreover, elevated TAZ expression was positively correlated with poor overall survival time, high Fuhrman grade and distant metastasis. Our receiver operating characteristic curves analysis showed that high TAZ expression could distinguish renal cancer patients from normal persons (p < 0.0001). Kaplan-Meier curves demonstrated that high TAZ expression predicted poor overall survival (p < 0.0001). Multivariate regression analysis indicated that TAZ expression could be an independent prognostic factor (p = 0.002) in patients with renal cancer. Finally, the functional roles of TAZ knockdown were examined in renal cancer cell lines and nude mice subcutaneous tumor models. In conclusion, our results suggest that TAZ may serve as a promising diagnostic and prognostic molecular marker for patients with renal cancer. Moreover, TAZ may represent a novel clinical therapeutic target.

TAZ inhibition restores sensitivity of cisplatin via AKT/mTOR signaling in lung adenocarcinoma.

The cisplatin-based doublet remains the foundation of treatment for the majority of patients with advanced non-small cell lung cancer (NSCLC), however, many patients exhibit acquired drug resistance. Transcriptional co-activator with PDZ binding motif (TAZ) is an oncogene in lung cancer, important for lung tumorigenesis and metastasis. Recently, it was revealed that TAZ upregulation confers resistance against a diverse range of cytotoxic agents. The present study aimed to investigate whether TAZ is involved in cisplatin sensitivity in lung adenocarcinoma. In the present study, we investigated TAZ expression in lung adenocarcinoma tissues and cell lines with western blot and RT-PCR analyses. By knocking down TAZ using short hairpin RNAs in cisplatin-resistant A549 and H460 cells, cell proliferation and apoptosis were assessed by BrdUrd labeling and flow cytometric analysis, respectively. The IC50 value of cisplatin was also assessed with CCK-8 assays. The western blotting for AKT, p-AKT, S6K and p-S6K were performed in cells with TAZ knockdown or overexpression. When the AKT/mTOR pathway was blocked in A549 and H460 with TAZ overexpression, cisplatin sensitivity was assessed by IC50 value. High expression of TAZ was found in lung adenocarcinoma tissues and cell lines, which were associated with cisplatin resistance. Knockdown of TAZ using shRNAs confered decreasing proliferation, increasing apoptosis and enhanced cisplatin sensitivity in cisplatin‑resistant cells. Additionally, TAZ knockdown decreased the AKT/mTOR pathway expression. Overexpression of TAZ increased p-AKT and p-S6K, which was inhibited by siAKT. Furthermore, we found that the inhibition of the AKT/mTOR pathway rescued the cells from cisplatin resistance caused by TAZ overexpression. Our data revealed that TAZ inhibition restores sensitivity of cisplatin in lung adenocarcinoma, which was, at least in part, AKT/mTOR signaling pathway-dependent. TAZ may be a potent therapeutic target for NSCLC in combination with conventional chemotherapy.

Prognostic significance of a component of the Hippo pathway, TAZ, in human uterine endometrioid adenocarcinoma.

Transcriptional coactivator with PDZ-binding motif (TAZ) is a crucial component of the Hippo tumor suppressor pathway, interacting with transcriptional factors to regulate cell proliferation, apoptosis and tumorigenesis. TAZ and its paralog, Yes-associated protein (YAP), are activated at high frequencies during the progression towards malignancy in various tumors. Recently, YAP has been identified to modulate oncogenic features in endometrial adenocarcinoma, and it has also been reported that the nuclear expression of YAP is correlated with the poorly-differentiated form of endometrioid adenocarcinoma. In contrast to YAP, no studies have investigated TAZ expression in endometrioid adenocarcinoma. In the present study, TAZ expression was immunohistochemically examined in 55 clinical samples of endometrioid adenocarcinoma, and the clinical implications were evaluated. The results demonstrated that TAZ was located primarily in the cell nuclei, and that high TAZ expression was significantly correlated with high tumor-factor (P=0.024), stage (P=0.041) and histological grade (P=0.001), lymph node metastasis (P=0.046), recurrence (P=0.002) and a poor prognosis (P=0.007). Furthermore, univariate analysis identified that high TAZ expression was a poor prognostic factor for overall and disease-free survival. To the best of our knowledge, the present case is the first to report the clinical implications of TAZ in endometrioid adenocarcinoma of the uterus. TAZ may become a marker of a poor prognosis in endometrioid adenocarcinoma.

High expression of TAZ indicates a poor prognosis in retinoblastoma.

BackgroundThe 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.MethodsTAZ 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.ResultsTAZ 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.ConclusionsOur findings suggest that the high expression of TAZ plays a significant role in retinoblastoma’s aggressiveness, and predicts poor prognosis for patients with retinoblastoma.

Abstract 3125: miR-9-3p plays a tumor-suppressor role by targeting TAZ (WWTR1) in hepatocellular carcinoma cells

Abstract Background: Hepatocellular carcinoma is the sixth most prevalent cancer and the third most frequent cause of cancer-related death. Despite recent advance in cancer treatment including the development of molecular target drugs, the prognosis in patients with hepatocellular carcinoma (HCC) still remains poor. The inactivation of the Hippo-pathway lead to TAZ/YAP overexpression, and is associated with worse prognostic outcomes in various cancers including hepatocellular carcinoma (HCC). While there are several reports of miR targeting for YAP, miR targeting for TAZ remains unclear. The aim of this study is to identify the miR targeting TAZ expression in HCC. Methods: miR expression was analyzed using the Human miFinder 384HC miScript miR PCR Array and was compared between low and high TAZ expression cell lines. Then, we extracted miR-9-3p as a tumor-suppressor miR targeting TAZ using miRBase. We examined the functional role of miR-9-3p targeting TAZ using miR-9-3p mimic and inhibitor in HCC cell lines (HLF and HuH1 with high and low TAZ expressions, respectively). Results: In HCC cell lines and HCC clinical samples, there was the inverse correlation between miR-9-3p and TAZ expressions by real-time PCR. By western blotting, TAZ expression was induced by treatment of miR-9-3p inhibitor and was downregulated by treatment of miR-9-3p mimic. TAZ nuclear localization was indeed inhibited with a treatment with miR-9-3p mimics in HLF cells, and was inversely accelerated with a treatment of miR-9-3p inhibitors in HuH1 cells. Treatment of miR-9-3p mimic inhibited cell proliferative ability by downregulating the phosphorylation of Erk1/2 and Akt signals in HLF. Inversely, treatment of miR-9-3p inhibitor accelerated cell growth compared to control in HuH1. On the other hand, cell invasiveness was not affected by miR-9-3p. Conclusions: miR-9-3p was identified as the tumor-suppressor miR targeting TAZ expression in HCC cells. miR-9-3p played a crucial role in cell proliferation, but not in invasion, via Akt and Erk1/2 signals in HCC cells. Citation Format: Takaaki Higashi, Hiromitsu Hayashi, Hideaki Takeyama, Takayoshi Kaida, Kota Arima, Katsunobu Taki, Hirohisa Okabe, Hidetoshi Nitta, Daisuke Hashimoto, Akira Chikamoto, Toru Beppu, Hideo Baba. miR-9-3p plays a tumor-suppressor role by targeting TAZ (WWTR1) in hepatocellular carcinoma cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3125. doi:10.1158/1538-7445.AM2015-3125

MiR-9-3p plays a tumour-suppressor role by targeting TAZ (WWTR1) in hepatocellular carcinoma cells.

Background:The inactivation of the Hippo pathway lead to TAZ (PDZ-binding motif)/YAP (yes-associated protein) overexpression, and is associated with worse prognostic outcomes in various cancers including hepatocellular carcinoma (HCC). Although there are several reports of microRNA (miR) targeting for YAP, miR targeting for TAZ remains unclear. The aim of this study is to identify the miR targeting TAZ expression in HCC.Methods:MicroRNA expression was analysed using the Human miFinder 384HC miScript miR PCR array, and was compared between low and high TAZ expression cell lines. Then, we extracted miR-9-3p as a tumour-suppressor miR targeting TAZ. We examined the functional role of miR-9-3p using miR-9-3p mimic and inhibitor in HCC cell lines).Results:In HCC cell lines and HCC clinical samples, there was the inverse correlation between miR-9-3p and TAZ expressions. TAZ expression was induced by treatment of miR-9-3p inhibitor and was downregulated by treatment of miR-9-3p mimic. Treatment of miR-9-3p mimic inhibited cell proliferative ability with downregulated phosphorylations of Erk1/2, AKT, and β-catenin in HLF. Inversely, treatment of miR-9-3p inhibitor accelerated cell growth compared with control in HuH1.Conclusions:MicroRNA-9-3p was identified as the tumour-suppressor miR targetting TAZ expression in HCC cells.

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.

Up-regulation of the Hippo pathway effector TAZ renders lung adenocarcinoma cells harboring EGFR-T790M mutation resistant to gefitinib.

BackgroundThe T790M mutation of epithelial growth factor receptor (EGFR) is a major cause of the acquired resistance to EGFR tyrosine kinase inhibitor (EGFR-TKIs) treatment for lung cancer patients. The Hippo pathway effector, TAZ, has emerged as a key player in organ growth and tumorigenesis, including lung cancer.ResultsIn this study, we have discovered high TAZ expression in non-small cell lung cancer (NSCLC) cells harboring dual mutation and TAZ depletion sensitized their response to EGFR-TKIs. Mechanistically, knockdown of TAZ in T790M-induced resistant cells leaded to reduced anchorage-independent growth in vitro, tumor formation and resistance to gefitinib in vivo, correlated with epithelial-mesenchymal transition (EMT) and suppressed migration and invasion. Furthermore, we confirmed CTGF and AXL, novel EMT markers and potential therapeutic targets for overcoming EGFR inhibitor resistance, as directly transcriptional targets of TAZ.ConclusionsTaken together, this study suggests that expression of TAZ is an intrinsic mechanism of T790M-induced resistance in response to EGFR-TKIs. Combinational targeting on both EGFR and TAZ may enhance the efficacy of EGFR-TKIs in acquired resistance of NSCLC.Electronic supplementary materialThe online version of this article (doi:10.1186/2045-3701-5-7) contains supplementary material, which is available to authorized users.

Highlights of This Issue

Manipulation of the apoptosis pathway is an appealing strategy for cancer treatment using BH3 mimetics such as ABT-263, although predictive biomarkers are required to identify patients who may benefit from their use. To investigate this problem, Suryani and colleagues studied the in vivo efficacy of ABT-263 against 31 pediatric acute lymphoblastic leukemia xenografts. High MCL1 expression and function correlated with in vivo ABT-263 resistance, and in vitro assays predicted in vivo ABT-263 responses. These approaches could be included in the design of prospective clinical trials to determine if they can identify patients who may respond to treatment with this class of therapeutic agents.Gastric carcinoma (GC) is the second leading cause of cancer deaths in the world, with many deaths occurring in East Asia. To identify DNA methylation biomarkers for prediction of GC metastasis, scientists, and oncologists from China, the United States, Japan, and Korea have profiled differential methylation patterns in GCs and perform an in-depth characterization of methylation changes in 73 candidate genes. The authors have established a methylation biomarker-set composed of three genes GFRA1, SRF, and ZNF382 that could be used to synergistically predict GC metastasis and patients' overall survival from multiple patient cohorts in China, Japan, and Korea.TAZ, the core component of Hippo signaling pathway, attracts increasing attention as a critical player in tumorigenesis. Using an integrated translational approach, the authors explored the role of TAZ in non-small cell lung cancer (NSCLC). Noguchi and colleagues showed that higher TAZ expression was associated with shorter patient survival, and TAZ promoted lung cancer cell proliferation in vitro and tumor development in vivo. Moreover, TAZ regulated the expression of ErbB ligands and the EGFR signaling pathway was activated in NSCLC tissues with high TAZ expression. This study offers potential therapeutic strategies, either directly against TAZ or indirectly via EGFR pathway.Activation of Wnt-signaling is a common event in colorectal carcinoma (CRC), but its role in CRC metastasis is still under extensive study. In the present study, Zhang and colleagues revealed subcellular redistribution of NAT10 (N-acetyltransferase 10) in CRCs, which correlated well with nuclear translocation of β-catenin and reflected invasive potential of CRC. They demonstrated that inhibition of GSK-3β induced NAT10 redistribution through increasing its stability and nuclear export, which consequently enhanced cytoskeletal remodeling and promoted migration, invasion, and metastasis of cancer cells. These findings suggest NAT10 could be a useful prognostic marker and potential therapeutic target in CRC.

Abstract B27: TAZ as a regulator of mesenchymal transformation and clinical aggressiveness in gliomas

Abstract Background: Glioblastoma (GBM) is a highly malignant and infiltrative brain tumor. Our laboratory has performed extensive microarray studies on GBM and has shown that a subset of these tumors have a gene expression signature characterized by those associated with the mesenchyme. Tumors which overexpress these genes (mesenchymal tumors) are associated with poor outcome and resistance to treatment. In an effort to identify the molecular mechanisms by which this mesenchymal shift occurs, we have identified TAZ (transcriptional coactivator with PDZ-binding motif) as a transcription co-activator whose expression level is tightly associated with the mesenchymal change (elevated TAZ is positively associated with higher expression of key mesenchymal genes). High expression of TAZ also correlated with higher grade glioma as well as poorer patient outcome. These data lead to our main hypothesis, that TAZ activation is critically important in the mesenchymal transition and aggressive clinical behavior in GBM. Results: To further discern TAZ's role in GBM, we stably silenced or overexpressed this gene in glioma stem cell lines depending on their basal levels of TAZ. Loss of TAZ did not affect proliferation, but did decrease invasion and dramatically decreased tumor formation when injected intracranially into severe combined immunodeficiency (SCID) mice. Five of 5 mice injected with control stem cell cultures developed tumors, while only 2 of 10 TAZ-knockdown cultures resulted in tumor formation. Furthermore, the 2 tumors that formed were of lower histologic grade compared to controls. Cells expressing a constitutively active form of TAZ were injected into SCID mice and 5 of the 5 mice injected with the overexpression clone died less than 60 days post-injection, while the mice injected with the vector control (low TAZ levels) survived an average of 120 days post-injection. Overexpression of TAZ increased invasion, and induced osteogenesis as evidenced by alizarin red staining, but did not alter proliferation. Further TAZ activation regulates the expression of signature mesenchymal genes, as shown by Affymetrix profiling of TAZ-transfected and TAZ-knockdown constructs. These data support the hypothesis that TAZ is a central regulator of mesenchymal gene expression in glioma. To further characterize TAZ function in human glioma, we examined the expression of its binding partners (TEAD1-4), as well as a downstream target (FN1) in human tumor specimens. Western analyses showed that TEAD4 was specifically upregulated in grade IV/GBM compared to lower grade gliomas, and TAZ/TEAD4 expression tightly paralleled FN1 expression, a marker of mesenchymal phenotype. Inspection of the TAZ promoter region revealed a CpG island in the promoter region that was methylated in most lower grade tumors (grade II/III gliomas), but not in grade IV GBMs implying that methylation may be one means by which TAZ is regulated and appears to be epigenetically silenced in tumors with a more favorable outcome. To confirm this, we found that treatment of TAZ-methylated glioma stem cell lines with a demethylation agent resulted in an increase in TAZ expression in both the mRNA and protein levels. Discussion: We have identified TAZ as a critical regulator in the mesenchymal transition in gliomas. Since mesenchymal differentiation is associated with gliomagenesis and tumor aggressiveness, strategies to target TAZ and its downstream targets may be warranted in alternative treatment options for patients. This study may also provide a rationale for developing inhibitors which directly target TAZ. Citation Information: Clin Cancer Res 2010;16(14 Suppl):B27.