The Clinicopathological Significance of YAP/TAZ Expression in Hepatocellular Carcinoma with Relation to Hypoxia and Stemness.

Background/Aims: Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) activation has been implicated in hepatocarcinogenesis and hepatic progenitor cell differentiation, and hypoxia has been shown to induce nuclear translocation of YAP in cancer cells. Here, we aimed to investigate the relationship between hypoxia, YAP and TAZ expression and stemness-related marker expression in human hepatocellular carcinomas (HCCs) and its clinical implications. Methods: Immunohistochemical stains were performed on tissue microarrays from 305 surgically resected HCCs, and the expression status of YAP and TAZ were correlated with CAIX, stemness markers (K19, EpCAM) and epithelial-mesenchymal transition (EMT)-related markers (uPAR, ezrin). The clinicopathological significance of YAP/TAZ expression was analyzed with relation to CAIX expression status. Results: YAP and TAZ expression were seen in 13.4 and 4.3% of HCCs, respectively. YAP/TAZ-positive HCCs frequently demonstrated higher serum AFP levels, microvascular invasion, advanced tumor stage, increased proliferative activity and expression of stemness- and EMT-related markers, CAIX, p53 and Smad2/3 (p < 0.05, all). Interestingly, YAP/TAZ-positivity was associated with microvascular invasion, higher serum AFP levels, stemness and EMT-related marker expression only in tumors expressing CAIX (p < 0.05, all), while these associations were not seen in CAIX-negative HCCs. Conclusions: YAP/TAZ expression is associated with vascular invasion, stemness and EMT in HCCs with hypoxia marker expression. The effect of Hippo signaling pathway deregulation in HCC may depend on the presence or absence of a hypoxic microenvironment, and hypoxia marker expression status should be taken into account when considering the use of YAP/TAZ as markers of aggressive biologic behavior in HCC.

Park H ，Lee Y ，Lee K ，Lee H ，Yoo JE ，Ahn S ，Park YN ，Kim H ... -  《-》

Human hepatocellular carcinomas with "Stemness"-related marker expression: keratin 19 expression and a poor prognosis.

There is a recently proposed subtype of hepatocellular carcinoma (HCC) that is histologically similar to usual HCC, but characterized by the expression of "stemness"-related markers. A large-scale study on two different cohorts of HCCs was performed to investigate the clinicopathologic features and epithelial-mesenchymal transition (EMT)-related protein expression status of this subtype of HCCs. The expression status of stemness-related (e.g., keratin 19 [K19], cluster of differentiation [CD]133, epithelial cell adhesion molecule [EpCAM], and c-kit) and EMT-related markers (e.g., snail, S100A4, urokinase plasminogen activator receptor [uPAR], ezrin, vimentin, E-cadherin, and matrix metalloproteinase [MMP]2) were examined using tissue microarrays from cohort 1 HCCs (n = 137). K19 protein expression in cohort 2 HCCs (n = 237) was correlated with the clinicopathologic parameters and messenger RNA (mRNA) levels of K19, uPAR, VIL2, Snail, Slug, and Twist. K19, EpCAM, c-kit, and CD133 positivity were observed in 18.2%, 35.0%, 34.3%, and 24.8%, respectively. K19 was most frequently expressed in combination with at least one other stemness-related marker (92.0%). K19-positive HCCs demonstrated more frequent major vessel invasion and increased tumor size, compared to K19-negative HCCs (P < 0.05). K19 was most significantly associated with EMT-related protein expression (e.g., vimentin, S100A4, uPAR, and ezrin) (P < 0.05) and a poor prognosis (overall survival: P = 0.018; disease-free survival: P = 0.007) in cohort 1. In cohort 2, HCCs with high K19 mRNA levels demonstrated higher mRNA levels of Snail, uPAR, and MMP2 (P < 0.05). K19-positive HCCs demonstrated more frequent microvascular invasion, fibrous stroma, and less tumor-capsule formation, compared to K19-negative HCCs (P < 0.05). K19 expression was a significant independent predictive factor of poor disease-free survival (P = 0.032). K19 was well correlated with clinicopathologic features of tumor aggressiveness, compared to other stemness-related proteins. K19-positive HCCs showed significantly increased EMT-related protein and mRNA expression, suggesting that they may acquire more invasive characteristics, compared to K19-negative HCCs through the up-regulation of EMT-associated genes.

Kim H ，Choi GH ，Na DC ，Ahn EY ，Kim GI ，Lee JE ，Cho JY ，Yoo JE ，Choi JS ，Park YN ... -  《-》

Transforming acidic coiled-coil-containing protein 3 (TACC3) overexpression in hepatocellular carcinomas is associated with "stemness" and epithelial-mesenchymal transition-related marker expression and a poor prognosis.

Nahm JH ，Kim H ，Lee H ，Cho JY ，Choi YR ，Yoon YS ，Han HS ，Park YN ... -  《-》

Poor outcome of hepatocellular carcinoma with stemness marker under hypoxia: resistance to transarterial chemoembolization.

Rhee H ，Nahm JH ，Kim H ，Choi GH ，Yoo JE ，Lee HS ，Koh MJ ，Park YN ... -  《-》

Distinct and Overlapping Roles of Hippo Effectors YAP and TAZ During Human and Mouse Hepatocarcinogenesis.

Yes-associated protein (YAP) and its paralog transcriptional co-activator with post synaptic density protein, drosophila disc large tumor suppressor and zonula occludens-1-binding motif (TAZ) are 2 co-activators downstream of Hippo tumor-suppressor cascade. Both have been implicated in the development of hepatocellular carcinoma (HCC). However, whether YAP and TAZ have distinct or overlapping functions during hepatocarcinogenesis remains unknown. Expression patterns of YAP and TAZ were analyzed in human HCC samples. The requirement of Yap and/or Taz in protein kinase B (Akt)/ neuroblastoma RAS viral oncogene homolog (NRas) -driven liver tumorigenesis was analyzed using conditional Yap, Taz, and Yap;Taz knockout mice. Transcriptional programs regulated by YAP and/or TAZ were identified via RNA sequencing. We found that in human HCC samples, an almost ubiquitous activation of YAP or TAZ occurs, underlying their role in this tumor type. Intriguingly, 70% of HCC samples showed only nuclear YAP or TAZ immunoreactivity. In the Akt/NRas liver tumor model, where nuclear Yap and Taz can be detected readily, deletion of Yap or Taz alone only mildly delayed liver tumor development, whereas their concomitant ablation strongly inhibited tumor cell proliferation and significantly suppressed Akt/NRas-driven hepatocarcinogenesis. In HCC cell lines, silencing of either YAP or TAZ led to decreased expression of both overlapping and distinct sets of genes, with the most prominent gene signatures related to cell-cycle progression and DNA replication. YAP and TAZ have overlapping and distinct roles in hepatocarcinogenesis. HCCs may display unique activation of YAP or TAZ, thus relying on either YAP or TAZ for their growth.

Wang H ，Wang J ，Zhang S ，Jia J ，Liu X ，Zhang J ，Wang P ，Song X ，Che L ，Liu K ，Ribback S ，Cigliano A ，Evert M ，Wu H ，Calvisi DF ，Zeng Y ，Chen X ... -  《Cellular and Molecular Gastroenterology and Hepatology》