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Background: We evaluated the diagnostic value of serum-CD166 in patients with hepatocellular carcinoma (HCC)., Methods: Tissue-CD166 was measured using immunohistochemistry. Cell proliferation and migration were evaluated using MTT and Transwell assays, respectively. Serum-CD166 was examined using ELISA and western blotting., Results: CD166 was up-regulated in HCC compared to those in normal liver tissues. Cell proliferation was positively correlated and cell migration was negatively correlated with endogenous CD166 expression in HCC cells. CD166 inhibition using specific shRNA decreased cell proliferation but increased cell migration. Serum CD166 concentrations were much higher in HCC than in colon cancer, hepatitis B, hepatitis C, cirrhosis, gastric cancer, breast cancer, lung cancer and healthy individuals. Serum CD166 also decreased dramatically after curative surgery. A positive correlation was found between serum CD166 and AFP (R=0.7141, p=0.000). Serum CD166 was also positively correlated with γ-GT, bile acid, ALT, AST, and ALP but was negatively correlated with Alb and pre-Alb. The area under the receiver operating characteristic curve for serum-CD166 was 0.9860, which was better than AFP (AUC-ROC, 0.9354) for the differentiation of HCC patients from healthy individuals, with a cut-off of 261 ng/ml (sensitivity: 100.00%, specificity: 89.41%)., Conclusion: Serum CD166 is a novel diagnostic tumor marker for HCC., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Recent studies are indicative for strong carcinogenetic roles of Runt related transcription factor 2 (Runx2) and Yes associated protein (YAP) in several cancer types. However, whether and how the interaction between Runx2 and YAP plays a role in liver tumorigenesis still remain illusive. Here, we identified a close relationship between Runx2 and YAP in liver cancer cells. Runx2 had a positive role on YAP expression and vice versa. We also found that Rux2 and YAP were capable of inhibiting long non-coding RNA (lncRNA), Metallothionein 1D, Pseudogene (MT1DP) expression through direct promoter binding. Overexpression of MT1DP resulted in reduced cell proliferation and colony formation in soft agar, but increased apoptosis in liver cancer cells, whereas knockdown of this lncRNA had the opposite effect, indicating that MT1DP acts as a tumor suppressor. Furthermore, MT1DP was revealed as a negative regulator of Alfa-fetoprotein (AFP), a classic liver cancer tumor marker, through inhibiting protein synthesis of Forkhead box A1 (FoxA1), an important transcription factor in liver development and cancer progression. Furthermore, we found that FoxA1 plays a positive role on YAP and Runx2 expression. Specially, opening the compacted chromatin by FoxA1 around CREB binding site within the YAP promoter facilitates CREB-mediated YAP transcription. Finally, MT1DP-inhibited in vivo liver cancer cell growth could be rescued by a combination of overexpression of FoxA1, Runx2 and YAP. Taken together, the close relationship between Rnux2 and YAP plays a pro-carcinogenetic role in liver cancer cells through inhibiting tumor suppressor lncRNA, MT1DP in a FoxA1 dependent manner., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Tribbles homolog 2 (TRIB2) is specifically regulated by Wnt signaling in liver cancer cells but not in colon cancer cells. However, whether and how TRIB2 regulates Wnt signaling in liver cancer cells remains unclear. Here, we report that TRIB2 negatively regulates Wnt activity through a reduction in protein stability of TCF4 and β-Catenin. Mechanistically, TRIB2 associated-ubiquitin E3 ligases beta-transducin repeat-containing E3 ubiquitin protein ligase (β-TrCP), COP1 and Smad ubiquitination regulatory factor 1 (Smurf1) reduced TCF4/β-Catenin expression, and these effects could be enhanced by TRIB2. Moreover, deletion of the binding regions of these E3-ligases within the TRIB2 protein decreased ubiquitination of TCF4/β-Catenin and reduced nuclear accumulation of β-TrCP, COP1 and Smurf1, which suggested that TRIB2 regulated-Wnt activity is closely correlated with its associated E3 ligases., (Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Mitogen-activated protein kinase kinase 1 (MAP2K1/MEK1) as well as Yes-associated protein (YAP), the downstream effector of Hippo signaling pathway, is linked to hepatocarcinogenesis. However, little is known about whether and how MEK1 interacts with YAP. In this study, we find that MEK1-YAP interaction is critical for liver cancer cell proliferation and maintenance of transformed phenotypes both in vitro and in vivo. Moreover, MEK1 and YAP proteins are closely correlated in human liver cancer samples. Mechanistically, inhibition of MEK1 by both PD98059 and U0126 as well as RNAi reduces beta-transducin repeat containing E3 ubiquitin protein ligase (BTRC), which acts as a potential endogenous YAP protector., (© 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Tribbles homolog 2 (TRIB2) is critical for both solid and non-solid malignancies. Recently, TRIB2 was identified as a liver cancer-specific Wnt/β-catenin signaling downstream target and is functionally important for liver cancer cell survival and transformation. TRIB2 functions as a protein that interacts with E3 ubiquitin ligases and thereby modulates protein stability of downstream effectors. However, the regulation underlying TRIB2 protein stability per se has not yet been reported. In this study, we found that TRIB2 was up-regulated and exhibited high stability in liver cancer cells compared with other cells. We performed a structure-function analysis of TRIB2 and identified a domain (amino acids 1-5) at the N terminus that interacted with the E3 ubiquitin ligase Smurf1 and was critical for protein stability. Deletion of this domain extended TRIB2 half-life time accompanied with a more significant malignant property compared with wild type TRIB2. Furthermore, Smurf1-mediated ubiquitination required phosphorylation of TRIB2 by p70 S6 kinase (p70S6K) via another domain (amino acids 69-85) that is also essential for correct TRIB2 subcellular localization. Mutation of Ser-83 diminished p70S6K-induced phosphorylation of TRIB2. Moreover, the high stability of TRIB2 may be due to the fact that both p70S6K and Smurf1 were down-regulated and negatively correlated with TRIB2 expression in both liver cancer tissues and established liver cancer cell lines. Taken together, impaired phosphorylation and ubiquitination by p70S6K and Smurf1 increase the protein stability of TRIB2 in liver cancer and thus may be helpful in the development of diagnosis and treatment strategies against this malignant disease.

Yes-associated protein (YAP), the downstream effector of Hippo signaling pathway as well as c-Myc has been linked to hepatocarcinogenesis. However, little is known about whether and how YAP and c-Myc interacts with each other. In this study, we find YAP-c-Myc interaction is critical for liver cancer cell both in vitro and in vivo. Moreover, both c-Myc and YAP proteins are closely correlated in human liver cancer samples. Mechanistically, YAP promotes c-Myc transcriptional output through c-Abl. By contrast, c-Myc enhances protein expression independent of transcription. Taken together, our study uncovers a novel positive auto-regulatory feedback loop underlying the interaction between YAP and c-Myc in liver cancer, suggesting YAP and c-Myc links Hippo/YAP and c-Myc pathways, and thus may be helpful in the development of effective diagnosis and treatment strategies against liver cancer., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Unlabelled: Yes-associated protein (YAP), the downstream effecter of the Hippo-signaling pathway as well as cyclic adenosine monophosphate response element-binding protein (CREB), has been linked to hepatocarcinogenesis. However, little is known about whether and how YAP and CREB interact with each other. In this study, we found that YAP-CREB interaction is critical for liver cancer cell survival and maintenance of transformative phenotypes, both in vitro and in vivo. Moreover, both CREB and YAP proteins are highly expressed in a subset of human liver cancer samples and are closely correlated. Mechanistically, CREB promotes YAP transcriptional output through binding to -608/-439, a novel region from the YAP promoter. By contrast, YAP promotes protein stabilization of CREB through interaction with mitogen-activated protein kinase 14 (MAPK14/p38) and beta-transducin repeat containing E3 ubiquitin protein ligase (BTRC). Gain-of-function and loss-of-function studies demonstrated that phosphorylation of CREB by MAPK14/p38 at ser133 ultimately leads to its degradation. Such effects can be enhanced by BTRC through phosphorylation of MAPK14/p38 at Thr180/Tyr182. However, YAP negatively controls phosphorylation of MAPK14/p38 through inhibition of BTRC expression., Conclusion: There is a novel positive autoregulatory feedback loop underlying the interaction between YAP and CREB in liver cancer, suggesting that YAP and CREB form a nexus to integrate the protein kinase A, Hippo/YAP, and MAPK14/p38 pathways in cancer cells and thus may be helpful in the development of effective diagnosis and treatment strategies against liver cancer., (© 2013 by the American Association for the Study of Liver Diseases.)