Clinicopathological and prognostic significance of Yes-associated protein expression in hepatocellular carcinoma and hepatic cholangiocarcinoma

Tubuloside B, a major constituent of Cistanche deserticola, inhibits migration of hepatocellular carcinoma by inhibiting Hippo-YAP pathway

BACKGROUND

Studies have shown that phenylethanoid glycosides (PhGs) have multiple pharmacological effects such as anti-inflammatory, hepatoprotective or neuroprotective functions, whereas their anti-tumor effects are rarely studied. Tubuloside B (Tub B) is a PhG isolated from Cistanche deserticola, a traditional Chinese medicine. To date, there is a lack of comprehensive research regarding the biological activity of Tub B.

PURPOSE

The subject of the current study was to investigate the anti-hepatocellular carcinoma (HCC) cell activity and the underlying mechanism of Tub B.

METHODS

We evaluated the in vitro anti-migratory effect of Tub B by scratch and transwell assays. RNA-seq was employed to identify the differential genes by Tub B. Besides, the functional mechanism of Tub B was investigated by distinct molecular biology techniques including immunofluorescent staining, quantitative PCR, as well as western blot analysis. Subsequently, we utilized Hep3B cells for in vivo metastasis assays through spleen injection and evaluated the anti-migratory effect of Tub B in hepatocellular carcinoma (HCC).

RESULTS

Tub B exhibited in vitro and in vivo inhibition of HCC cell migration. Tub B decreased the expression of transcriptional target genes downstream of the Hippo pathway, including CTGF, CYR61, and N-cadherin as determined by RNA-seq. Furthermore, mechanistic studies confirmed that Tub B increased phosphorylation of YAP at S127, which contributes to YAP cytoplasmic localization. Additionally, overexpression of YAP abrogated Tub B-induced inhibition of HCC migration and the mRNA levels of CTGF, CYR61, and N-cadherin.

CONCLUSIONS

Taken together, these results illustrated that Tub B demonstrated great potential in inhibiting migration of HCC, and a portion of its impact can be attributed to the modulation of the Hippo-YAP pathway.

Prognostic analysis of Yes-associated protein 1 in patients with colorectal cancer. A systematic review and meta-analysis

BACKGROUND

colorectal cancer (CRC) is the most common carcinoma worldwide, but a lack of effective prognostic markers limits clinical diagnosis and treatment. Yes-associated protein 1 (YAP1) is an effector of the HIPPO-pathway, which plays a critical role in cancer development and prognosis, including CRC. However, previous reports have suggested that it plays a dual role in CRC.

METHODS

a meta-analysis using RevMan 5.4 and Stata 14.0 was performed to evaluate the relationship between YAP1 and clinical outcomes of CRC, after searching for eligible studies in the PubMed, Web of Science and Embase databases. Online datasets GEPIA and LOGpc were also used to calculate survival results and for comparison with the meta-analysis results. Besides, "DESeq" packages were used for the expression analysis of YAP1 from the TCGA dataset.

RESULTS

YAP1 was overexpressed in the cancer tissues when compared to normal tissues in patients with CRC from the TCGA database (p = 0.000164) and GEPIA database. A total of 10 studies involving 2305 patients from the literature were selected. Pooled HR indicated that overexpression of YAP1 was associated with poor clinical outcomes (HR = 1.70, 95 % CI: 1.28-2.26, p = 0.0003). Subgroup analysis showed a clear correlation between overexpression of YAP1 and worse survival rate in Chinese patients (HR = 1.94, 95 % CI: 1.40-2.69, p = 0.0001), nuclear YAP1 overexpression (HR = 2.07, 95 % CI: 1.29-3.31, p = 0.003), 60 months of follow-up (HR = 1.89, 95 % CI: 1.30-2.73, p = 0.0008), IHC test (HR = 1.65, 95 % CI: 1.17-2.33, p = 0.005), IHC combined with other tests (HR = 1.77, 95 % CI: 1.13-2.77, p = 0.01) and multivariate analysis (HR = 1.70, 95 % CI: 1.24-2.31, p = 0.0009). Nevertheless, disease-free survival (DFS) showed no significant results in the patients with CRC in our meta-analysis (HR = 1.38, 95 % CI: 0.51-3.75, p = 0.52) as well as in the GEPIA and LOGpc databases. Meanwhile, YAP1 overexpression was also significantly associated with worse overall survival (OS) in GSE17536, GSE40967, GSE29623 and GSE71187.

CONCLUSION

YAP1 overexpression is common in CRC tissues. Overexpression of YAP1 in CRC patients, particularly in the nucleus, might be related to shorter OS, maybe in the early stages. YAP1 could serve as a potential predictor of poor prognosis in CRC.

Changes in m6A in Steatotic Liver Disease

Fatty liver disease is one of the major causes of morbidity and mortality worldwide. Fatty liver includes non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), now replaced by a consensus group as metabolic dysfunction-associated steatotic liver disease (MASLD). While excess nutrition and obesity are major contributors to fatty liver, the underlying mechanisms remain largely unknown and therapeutic interventions are limited. Reversible chemical modifications in RNA are newly recognized critical regulators controlling post-transcriptional gene expression. Among these modifications, N6-methyladenosine (m6A) is the most abundant and regulates transcript abundance in fatty liver disease. Modulation of m6A by readers, writers, and erasers (RWE) impacts mRNA processing, translation, nuclear export, localization, and degradation. While many studies focus on m6A RWE expression in human liver pathologies, limitations of technology and bioinformatic methods to detect m6A present challenges in understanding the epitranscriptomic mechanisms driving fatty liver disease progression. In this review, we summarize the RWE of m6A and current methods of detecting m6A in specific genes associated with fatty liver disease.

The molecular mechanisms and targeting strategies of transcription factors in cholangiocarcinoma

INTRODUCTION

Cholangiocarcinoma consists of a cluster of malignant biliary tumors that tend to have a poor prognosis, ranking as the second most prevalent type of liver cancer, and their incidence rate has increased globally recently. The high-frequency driving mutations of cholangiocarcinoma, such as KRAS/IDH1/ARID1A/P53, imply the epigenetic instability of cholangiocarcinoma, leading to the dysregulation of various related transcription factors, thus affecting the occurrence and development of cholangiocarcinoma. Increasingly evidence indicates that the high heterogeneity and malignancy of cholangiocarcinoma are closely related to the dysregulation of transcription factors which promote cell proliferation, invasion, migration, angiogenesis, and drug resistance through reprogrammed transcriptional networks. It is of great significance to further explore and summarize the role of transcription factors in cholangiocarcinoma.

AREAS COVERED

This review summarizes the oncogenic or tumor suppressive roles of key transcription factors in regulating cholangiocarcinoma progression and the potential targeting strategies of transcription factors in cholangiocarcinoma.

EXPERT OPINION

Cholangiocarcinoma is a type of cancer highly influenced by transcriptional regulation, specifically transcription factors and epigenetic regulatory factors. Targeting transcription factors could be a potential and important strategy that is likely to impact future cholangiocarcinoma treatment.

Advances in prognostic and therapeutic targets for hepatocellular carcinoma and intrahepatic cholangiocarcinoma: The hippo signaling pathway

Primary liver cancer is the sixth most frequently diagnosed cancer worldwide and the third leading cause of cancer-related death. The majority of the primary liver cancer cases are hepatocellular carcinoma and intrahepatic cholangiocarcinoma. Worldwide, there is an increasing incidence of primary liver cancer cases due to multiple risk factors ranging from parasites and viruses to metabolic diseases and lifestyles. Often, patients are diagnosed at advanced stages, depriving them of surgical curability benefits. Moreover, the efficacy of the available chemotherapeutics is limited in advanced stages. Furthermore, tumor metastases and recurrence make primary liver cancer management exceptionally challenging. Thus, exploring the molecular mechanisms for the development and progression of primary liver cancer is critical in improving diagnostic, treatment, prognostication, and surveillance modalities. These mechanisms facilitate the discovery of specific targets that are critical for novel and more efficient treatments. Consequently, the Hippo signaling pathway executing a pivotal role in organogenesis, hemostasis, and regeneration of tissues, regulates liver cells proliferation, and apoptosis. Cell polarity or adhesion molecules and cellular metabolic status are some of the biological activators of the pathway. Thus, understanding the mechanisms exhibited by the Hippo pathway is critical to the development of novel targeted therapies. This study reviews the advances in identifying therapeutic targets and prognostic markers of the Hippo pathway for primary liver cancer in the past six years.

NOTCH-YAP1/TEAD-DNMT1 Axis Drives Hepatocyte Reprogramming Into Intrahepatic Cholangiocarcinoma

BACKGROUND & AIMS

Intrahepatic cholangiocarcinoma (ICC) is a devastating liver cancer with extremely high intra- and inter-tumoral molecular heterogeneity, partly due to its diverse cellular origins. We investigated clinical relevance and the molecular mechanisms underlying hepatocyte (HC)-driven ICC development.

METHODS

Expression of ICC driver genes in human diseased livers at risk for ICC development were examined. The sleeping beauty and hydrodynamic tail vein injection based Akt-NICD/YAP1 ICC model was used to investigate pathogenetic roles of SRY-box transcription factor 9 (SOX9) and yes-associated protein 1 (YAP1) in HC-driven ICC. We identified DNA methyltransferase 1 (DNMT1) as a YAP1 target, which was validated by loss- and gain-of-function studies, and its mechanism addressed by chromatin immunoprecipitation sequencing.

RESULTS

Co-expression of AKT and Notch intracellular domain (NICD)/YAP1 in HC yielded ICC that represents 13% to 29% of clinical ICC. NICD independently regulates SOX9 and YAP1 and deletion of either, significantly delays ICC development. Yap1 or TEAD inhibition, but not Sox9 deletion, impairs HC-to-biliary epithelial cell (BEC) reprogramming. DNMT1 was discovered as a novel downstream effector of YAP1-TEAD complex that directs HC-to-BEC/ICC fate switch through the repression of HC-specific genes regulated by master regulators for HC differentiation, including hepatocyte nuclear factor 4 alpha, hepatocyte nuclear factor 1 alpha, and CCAAT/enhancer-binding protein alpha/beta. DNMT1 loss prevented NOTCH/YAP1-dependent HC-driven cholangiocarcinogenesis, and DNMT1 re-expression restored ICC development following TEAD repression. Co-expression of DNMT1 with AKT was sufficient to induce tumor development including ICC. DNMT1 was detected in a subset of HCs and dysplastic BECs in cholestatic human livers prone to ICC development.

CONCLUSION

We identified a novel NOTCH-YAP1/TEAD-DNMT1 axis essential for HC-to-BEC/ICC conversion, which may be relevant in cholestasis-to-ICC pathogenesis in the clinic.

A derivant of ginsenoside CK and its inhibitory effect on hepatocellular carcinoma

Epidemiological studies have shown that hepatocellular carcinoma (HCC) is a main cause of tumor death worldwide. Accumulating data indicate that ginsenoside CK is an effective compound for preventing HCC growth and development. However, improvement of pharmaceutical effect of the ginsenoside CK is still needed. In our study, we performed acetylation of ginsenoside CK (CK-3) and investigated the antitumor effects of the derivative in vitro and in vivo. The cytotoxicity analysis revealed that compared with CK, CK-3 could inhibit the proliferation of multiple tumor cell lines at a lower concentration. Treating with CK-3 on HCC cells arrested cell cycle in G2/M phase and induced cell apoptosis through AO/EB staining, TUNEL analysis and flow cytometry. Meanwhile, CK-3 significantly inhibited tumor growth in an HCC xenograft model and showed no side effect on the function of the main organs. Mechanistically, whole transcriptome analysis revealed that the antitumor effect of CK-3 was involved in the Hippo signaling pathway. The immunoblotting and immunofluorescence results illustrated that CK-3 directly facilitated the phosphorylation of YAP1 and decreased the expression of the main transcription factor TEAD2 in HCC cell lines and tumor tissue sections. Collectively, our results demostrate the formation of a new derivative of ginsenoside CK and its regulatory mechanism in HCC, which could activate the Hippo-YAP1-TEAD2 signaling pathway to regulate HCC progression. This research could provide a new direction for traditional Chinese medicine in the therapy of tumors.

Hippo signalling in the liver: role in development, regeneration and disease

The Hippo signalling pathway has emerged as a major player in many aspects of liver biology, such as development, cell fate determination, homeostatic function and regeneration from injury. The regulation of Hippo signalling is complex, with activation of the pathway by diverse upstream inputs including signals from cellular adhesion, mechanotransduction and crosstalk with other signalling pathways. Pathological activation of the downstream transcriptional co-activators yes-associated protein 1 (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ, encoded by WWTR1), which are negatively regulated by Hippo signalling, has been implicated in multiple aspects of chronic liver disease, such as the development of liver fibrosis and tumorigenesis. Thus, development of pharmacological inhibitors of YAP-TAZ signalling has been an area of great interest. In this Review, we summarize the diverse roles of Hippo signalling in liver biology and highlight areas where outstanding questions remain to be investigated. Greater understanding of the mechanisms of Hippo signalling in liver function should help facilitate the development of novel therapies for the treatment of liver disease.

YAP1 activation and Hippo pathway signaling in the pathogenesis and treatment of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA), the second most common primary liver cancer, is a highly lethal epithelial cell malignancy exhibiting features of cholangiocyte differentiation. iCCAs can potentially develop from multiple cell types of origin within liver, including immature or mature cholangiocytes, hepatic stem cells/progenitor cells, and from transdifferentiation of hepatocytes. Understanding the molecular mechanisms and genetic drivers that diversely drive specific cell lineage pathways leading to iCCA has important biological and clinical implications. In this context, activation of the YAP1-TEAD dependent transcription, driven by Hippo-dependent or -independent diverse mechanisms that lead to the stabilization of YAP1 is crucially important to biliary fate commitment in hepatobiliary cancer. In preclinical models, YAP1 activation in hepatocytes or cholangiocytes is sufficient to drive their malignant transformation into iCCA. Moreover, nuclear YAP1/TAZ is highly prevalent in human iCCA irrespective of the varied etiology, and significantly correlates with poor prognosis in iCCA patients. Based on the ubiquitous expression and diverse physiologic roles for YAP1/TAZ in the liver, recent studies have further revealed distinct functions of active YAP1/TAZ in regulating tumor metabolism, as well as the tumor immune microenvironment. In the current review, we discuss our current understanding of the various roles of the Hippo-YAP1 signaling in iCCA pathogenesis, with a specific focus on the roles played by the Hippo-YAP1 pathway in modulating biliary commitment and oncogenicity, iCCA metabolism, and immune microenvironment. We also discuss the therapeutic potential of targeting the YAP1/TAZ-TEAD transcriptional machinery in iCCA, its current limitations, and what future studies are needed to facilitate clinical translation.

R-2HG downregulates ERα to inhibit cholangiocarcinoma via the FTO/m6A-methylated ERα/miR16-5p/YAP1 signal pathway

Isocitrate dehydrogenase (IDH) mutations increase (R)-2-hydroxyglutarate (R-2HG) production; however, functional mechanisms of R-2HG in regulating cholangiocarcinoma (CCA) development remain to be further investigated. We first applied the CRISPR-Cas9 gene-editing system to create IDH1R132H-mutated CCA cells. Interestingly, our data showed that R-2HG could function through downregulating estrogen receptor alpha (ERα) and Yes-associated protein 1 (YAP1) pathways to decrease CCA growth. Detailed mechanistic studies revealed that R-2HG could target and degrade the fat mass and obesity-associated protein (FTO), the first identified mRNA demethylase. This reduced FTO can increase the N⁶-methyladenosine (m6A) to methylate the mRNA of ERα, and consequently decrease protein translation of the ERα. Further mechanistic studies revealed that ERα could transcriptionally suppress miR-16-5p expression, which could then increase YAP1 expression due to the reduced miR-16-5p binding to the 3′ UTR of YAP1. Furthermore, data from the pre-clinical animal model with implantation of IDH1R132H QBC939 cells demonstrated that R-2HG generated by the IDH1 mutation could downregulate ERα and YAP1 to suppress CCA tumor growth. Taken together, our new findings suggested that IDH1 mutation-induced R-2HG could suppress CCA growth via regulating the FTO/m6A-methylated ERα/miR16-5p/YAP1 signaling pathway. Upregulating R-2HG or downregulating the ERα signal by short hairpin RNA ERα (shERα) or antiestrogen could be effective strategies to inhibit CCA.

Sugar defeats the Hippo: Glycogen regulation of the Hippo pathway in liver

Liver glycogen is famous for glucose storage, but new work by Liu et al. (2021) now reveals that it's been hiding a few secrets and can directly promote liver enlargement and tumorigenesis by sequestering the tumor-suppressive Hippo signaling pathway.

Deubiquitinase JOSD2 stabilizes YAP/TAZ to promote cholangiocarcinoma progression

Cholangiocarcinoma (CCA) has emerged as an intractable cancer with scanty therapeutic regimens. The aberrant activation of Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) are reported to be common in CCA patients. However, the underpinning mechanism remains poorly understood. Deubiquitinase (DUB) is regarded as a main orchestrator in maintaining protein homeostasis. Here, we identified Josephin domain-containing protein 2 (JOSD2) as an essential DUB of YAP/TAZ that sustained the protein level through cleavage of polyubiquitin chains in a deubiquitinase activity-dependent manner. The depletion of JOSD2 promoted YAP/TAZ proteasomal degradation and significantly impeded CCA proliferation in vitro and in vivo. Further analysis has highlighted the positive correlation between JOSD2 and YAP abundance in CCA patient samples. Collectively, this study uncovers the regulatory effects of JOSD2 on YAP/TAZ protein stabilities and profiles its contribution in CCA malignant progression, which may provide a potential intervention target for YAP/TAZ-related CCA patients.

High YAP and TEAD4 immunolabelings are associated with poor prognosis in patients with gallbladder cancer

Yes-associated protein (YAP) and TEA domain-containing sequence-specific transcription factors 4 (TEAD4) are essential components of the Hippo pathway. Abnormal regulation of the Hippo pathway contributes to the progression and metastasis of many cancer types. However, their clinicopathologic and prognostic significances have not been studied in gallbladder cancers. Here, we systematically evaluated the YAP and TEAD4 immunolabelings and their association with clinicopathologic characteristics and survival outcomes using 212 specimens of surgically resected gallbladder cancers. High YAP and TEAD4 immunolabelings were identified in 70 (33%) cases and were associated with infiltrative growth pattern, poor differentiation, perineural invasion, and advanced pT classification and AJCC stage. High YAP immunolabeling was significantly associated with high TEAD4 immunolabeling (p < 0.001). High immunolabeling levels of YAP or TEAD4 alone and the combined YAP^high TEAD4^high group were significantly associated with poor survival in both univariate (p < 0.001) and multivariate analyses (HR = 2.358; 95% CI, 1.369-4.061; p = 0.002). Therefore, the YAP and TEAD4 immunolabelings are associated with aggressive behavior of gallbladder cancers and may be useful as a prognostic indicator in patients with surgically resected gallbladder cancer.

Co-expression of YAP and TAZ associates with chromosomal instability in human cholangiocarcinoma

Background

Activation of the oncogene yes-associated protein (YAP) is frequently detected in intrahepatic cholangiocarcinoma (iCCA); however, the expression pattern and the functional impact of its paralogue WW domain-containing transcription regulator 1 (WWTR1; synonym: TAZ) are not well described in different CCA subtypes.

Methods

Immunohistochemical analysis of YAP and TAZ in iCCA and extrahepatic CCA (eCCA) cohorts was performed. YAP/TAZ shuttling and their functional impact on CCA cell lines were investigated. Target genes expression after combined YAP/TAZ inhibition was analyzed.

Results

Immunohistochemical analysis of iCCA and eCCA revealed YAP or TAZ positivity in up to 49.2%; however, oncogene co-expression was less frequent (up to 23%). In contrast, both proteins were jointly detectable in most CCA cell lines and showed nuclear/cytoplasmic shuttling in a cell density-dependent manner. Next to the pro-proliferative function of YAP/TAZ, both transcriptional co-activators cooperated in the regulation of a gene signature that indicated the presence of chromosomal instability (CIN). A correlation between YAP and the CIN marker phospho-H2A histone family member X (pH2AX) was particularly observed in tissues from iCCA and distal CCA (dCCA). The presence of the CIN genes in about 25% of iCCA was statistically associated with worse prognosis.

Conclusions

YAP and TAZ activation is not uncoupled from cell density in CCA cells and both factors cooperatively contribute to proliferation and expression of CIN-associated genes. The corresponding group of CCA patients is characterized by CIN and may benefit from YAP/TAZ-directed therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08794-5.

The hippo pathway: A master regulator of liver metabolism, regeneration, and disease

The liver is the only visceral organ in the body with a tremendous capacity to regenerate in response to insults that induce inflammation, cell death, and injury. Liver regeneration is a complicated process involving a well-orchestrated activation of non-parenchymal cells in the injured area and proliferation of undamaged hepatocytes. Furthermore, the liver has a Hepatostat, defined as adjustment of its volume to that required for homeostasis. Understanding the mechanisms that control different steps of liver regeneration is critical to informing therapies for liver repair, to help patients with liver disease. The Hippo signaling pathway is well known for playing an essential role in the control and regulation of liver size, regeneration, stem cell self-renewal, and liver cancer. Thus, the Hippo pathway regulates dynamic cell fates in liver, and in absence of its downstream effectors YAP and TAZ, liver regeneration is severely impaired, and the proliferative expansion of liver cells blocked. We will mainly review upstream mechanisms activating the Hippo signaling pathway following partial hepatectomy in mouse model and patients, its roles during different steps of liver regeneration, metabolism, and cancer. We will also discuss how targeting the Hippo signaling cascade might improve liver regeneration and suppress liver tumorigenesis.

Liver Inflammation and Hepatobiliary Cancers

Immune regulation has an important role in cancer development, particularly in organs with continuous exposure to environmental pathogens, such as the liver and gastrointestinal tract. Chronic liver inflammation can lead to the development of hepatobiliary cancers, namely hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (iCCA), or combined HCC (cHCC)-CCA. In this review, we discuss the link between oxidative stress and the hepatic immune compartments, as well as how these factors trigger hepatocyte damage, proliferation, and eventually cancer initiation and its sustainment. We further give an overview of new anticancer therapies based on immunomodulation.

The YAP-Interacting Phosphatase SHP2 Can Regulate Transcriptional Coactivity and Modulate Sensitivity to Chemotherapy in Cholangiocarcinoma

The Hippo pathway effector Yes-associated protein (YAP) is localized to the nucleus and transcriptionally active in a number of tumor types, including a majority of human cholangiocarcinomas. YAP activity has been linked to chemotherapy resistance and has been shown to rescue KRAS and BRAF inhibition in RAS/RAF-driven cancers; however, the underlying mechanisms of YAP-mediated chemoresistance have yet to be elucidated. Herein, we report that the tyrosine phosphatase SHP2 directly regulates the activity of YAP by dephosphorylating pYAPY357 even in the setting of RAS/RAF mutations, and that diminished SHP2 phosphatase activity is associated with chemoresistance in cholangiocarcinomas. A screen for YAP-interacting tyrosine phosphatases identified SHP2, and characterization of cholangiocarcinomas cell lines demonstrated an inverse relationship between SHP2 levels and pYAPY357. Human sequencing data demonstrated lower SHP2 levels in cholangiocarcinomas tumors as compared with normal liver. Cell lines with low SHP2 expression and higher levels of pYAPY357 were resistant to gemcitabine and cisplatin. In cholangiocarcinomas cells with high levels of SHP2, pharmacologic inhibition or genetic deletion of SHP2 increased YAPY357 phosphorylation and expression of YAP target genes, including the antiapoptotic regulator MCL1, imparting resistance to gemcitabine and cisplatin. In vivo evaluation of chemotherapy sensitivity demonstrated significant resistance in xenografts with genetic deletion of SHP2, which could be overcome by utilizing an MCL1 inhibitor. IMPLICATIONS: These findings demonstrate a role for SHP2 in regulating YAP activity and chemosensitivity, and suggest that decreased phosphatase activity may be a mechanism of chemoresistance in cholangiocarcinoma via a MCL1-mediated mechanism.

The Hippo Pathway and YAP Signaling: Emerging Concepts in Regulation, Signaling, and Experimental Targeting Strategies With Implications for Hepatobiliary Malignancies

The Hippo pathway and its effector protein YAP (a transcriptional coactivator) have been identified as important in the biology of both hepatocellular carcinoma and cholangiocarcinoma. First identified as a tumor suppressor pathway in Drosophila, the understanding of the mammalian YAP signaling and its regulation continues to expand. In its "on" function, the canonical regulatory Hippo pathway, a well-described serine/threonine kinase module, regulates YAP function by restricting its subcellular localization to the cytoplasm. In contrast, when the Hippo pathway is "off," YAP translocates to the nucleus and drives cotranscriptional activity. Given the role of Hippo/YAP signaling in hepatic malignancies, investigators have sought to target these molecules; however, standard approaches have not been successful based on the pathways' negative regulatory role. More recently, additional regulatory mechanisms, such as tyrosine phosphorylation, of YAP have been described. These represent positive regulatory events that may be targetable. Additionally, several groups have identified potentiating feed-forward signaling for YAP in multiple contexts, suggesting other experimental therapeutic approaches to interrupt these signaling loops. Herein we explore the current data supporting alternative YAP regulatory pathways, review the described feed-forward signaling cascades that are YAP dependent, and explore targeting strategies that have been employed in preclinical models of hepatic malignancies.

YAP Levels Combined with Plasma CEA Levels Are Prognostic Biomarkers for Early-Clinical-Stage Patients of Colorectal Cancer

Background

Colorectal cancer (CRC) is one of the most common cancers worldwide. Surgical operation is routinely applied to patients with CRC. An important part of postoperative care for patients is to assess the prognosis of patients, especially those with early-stage cancers. However, effective biomarkers for CRC prognosis remain inadequate. The purpose of this study was to assess the prognostic potential of Yes-associated protein (YAP) and carcinoembryonic antigen (CEA) in early-stage CRC.

Methods

A total of 116 matched pairs of CRC tissues and adjacent normal mucosae as well as 73 cases of metastatic lymph nodes were analyzed.

Results

The results show that CRC tissues exhibited higher YAP expression compared with the adjacent normal mucosae. Immunohistochemical analysis shows that YAP expression in the CRC or lymphatic metastatic tissues was clearly higher than that in normal mucosae (P < 0.01), whereas that in CRC tissues with lymphatic metastasis was higher than that in tissues without lymphatic metastasis (P < 0.05). YAP expression is associated with serosal invasion, lymphatic metastasis, lymph node ratio, remote metastasis, Dukes stage, and CEA levels (P < 0.05). YAP and CEA are independent predictors of the survival of CRC patients (P < 0.05 and P < 0.01). YAP predicted CRC prognosis primarily for patients with late-clinical-stage CRC (P=0.002), but not for patients with early-clinical-stage CRC (P=0.083). However, patients with high YAP and high CEA levels exhibited lower overall survival rates than those with low YAP expression in early-clinical-stage CRC (P < 0.001).

Conclusion

High YAP levels in the cancer tissues combined with high plasma CEA levels are potential biomarkers for predicting CRC prognosis in the early clinical stage.

Progress in research on association between cell signal transduction pathways and hepatocellular carcinoma

Cell signal transduction refers to the process by which a signal molecule induces signal transduction in a cell by stimulating the cell membrane or intracellular receptor, thereby affecting the biological function of the cell. In recent years, studies have found that the activation or inhibition of certain cell signal transduction pathways plays an important role in the development and progression of hepatocellular carcinoma. This article will review the recent research progress in the understanding of the role of some common signal transduction pathways in hepatocellular carcinoma.

The prognostic value of YAP1 on clinical outcomes in human cancers

Background: As an important downstream factor in the Hippo pathway, yes-associated protein 1(YAP1) has been detected to be elevated in various cancers and demonstrated to play a role in tumor development. Therefore, we evaluated by a meta-analysis the prognostic value of YAP1 in cancer patients.

Results: Sixty-eight studies with 8631 patients were identified. The results indicated that YAP1 overexpression predicted unfavorable patient prognosis in studies with overall survival (OS) (HR=1.76, 95%CI: 1.50-2.06, p<0.001) and disease-free survival (DFS) (HR=1.39, 95%CI: 1.22-1.59, p<0.001), as well as in studies with recurrence-free survival (RFS) (HR=2.38, 95%CI: 1.73-3.27, p<0.001), and disease-specific survival (DSS) (HR=2.04, 95%CI: 1.55-2.70, p<0.001). Meanwhile, YAP1 overexpression was also observed to be significantly associated with worse OS in GEPIA (HR=1.2, p<0.001).

Conclusions: Overexpression of YAP1 showed great association with poorer prognosis in patients with various cancers, particularly liver cancer. Therefore, YAP1 might be an important prognostic marker and a novel target of cancer therapy.

Methods: We searched for potential publications in several online databases and retrieved relevant data. Overall and subgroup analyses were performed. Begg’s and Egger’s tests were used to assess publication bias. Online dataset GEPIA was used to generate the survival curves and verify the prognostic role of YAP1 in patients with tumors.

Decreased expression of HDAC8 indicates poor prognosis in patients with intrahepatic cholangiocarcinoma

BACKGROUND

Intrahepatic cholangiocarcinoma (ICC) is a highly malignant primary tumor in the liver, and the rates of incidence and mortality are rapidly increasing globally. Histone deacetylase 8 (HDAC8) is a transcriptional regulator and is associated with tumorigenesis of several tumor types. This study aimed to evaluate the correlation between HDAC8 expression and clinicopathological parameters in ICC patients.

METHODS

ICC tissues and corresponding nonmalignant bile duct tissues were obtained from 60 patients. HDAC8 and Ki-67 expression were evaluated by immunohistochemistry staining. HDAC8 expression and the clinicopathological features and prognosis of the patients were analyzed. The mRNA level of HDAC8 in ICC was further analyzed using data from The Cancer Genome Atlas (TCGA).

RESULTS

The expression of HDAC8 were lower in ICC tissues (39/60, 65%) than in the corresponding nonmalignant bile duct tissues (54/60, 90%) (P = 0.001). Low HDAC8 expression in ICC was significantly associated with lymph node metastases (47.6% vs. 17.9%, P = 0.015). In addition, the positive cells rate of HDAC8 was statistically and negatively correlated with the Ki-67 index in ICC lesions (r = -0.7660, P < 0.001). Importantly, the overall survival rate and recurrence-free survival rate in ICC patients with low HDAC8 expression were lower than those with high HDAC8 expression (P = 0.008 and P = 0.011, respectively).

CONCLUSIONS

Decreased HDAC8 expression in ICC is related to poor prognosis, and HDAC8 may be an independent prognostic indicator of ICC patients after curative resection.

YAP and the Hippo pathway in cholangiocarcinoma

Cholangiocarcinoma (CCA) has an increasing incidence and remains a difficult to treat malignancy. In a search for more effective treatment options, progress has been made in identifying molecular drivers of oncogenic signaling including IDH mutations and FGFR2 fusions. In addition, multiple investigators have identified increased activity of YAP, the effector protein of the Hippo pathway, in CCA. The Hippo pathway regulates organ size, cellular proliferation, and apoptosis via YAP, a transcriptional co-activator. Targeting of the pathway has been difficult due the lack of a dedicated cell-surface receptor. However, more recently, additional cross-regulatory pathways have been identified that are potentially targetable. In this review, we address the current treatment landscape for CCA, the Hippo pathway broadly, animal models of CCA with attention to Hippo-related models, and the current strategies for targeting YAP.

Hippo Signaling in the Liver - A Long and Ever-Expanding Story

The first description of Hippo signaling in mammals a little more than 10 years ago showed a striking phenotype in the liver, linking the role of this signaling pathway to organ size control and carcinogenesis. Even though Hippo signaling has been extensively studied in the liver and other organs over the recent years, many open questions remain in our understanding of its role in hepatic physiology and disease. The functions of Hippo signaling extend well beyond cancer and organ size determination: components of upstream Hippo signaling and the downstream effectors YAP and TAZ are involved in a multitude of cell and non-cell autonomous functions including cell proliferation, survival, development, differentiation, metabolism, and cross-talk with the immune system. Moreover, regulation and biological functions of Hippo signaling are often organ or even cell type specific – making its role even more complex. Here, we give a concise overview of the role of Hippo signaling in the liver with a focus on cell-type specific functions. We outline open questions and future research directions that will help to improve our understanding of this important pathway in liver disease.

Blockade of YAP alleviates hepatic fibrosis through accelerating apoptosis and reversion of activated hepatic stellate cells

Yes-associated protein (YAP) is a significant downstream protein in the Hippo signaling pathway with important functions in cell proliferation, apoptosis, invasion and migration. YAP also plays a role in the progression and development of various liver diseases. In hepatic fibrosis development and reversion, the proliferation and apoptosis of activated hepatic stellate cells (HSCs) play a critical role. However, the contribution of YAP to hepatic fibrosis progression and reversion and the underlying mechanism have not been investigated. Here we investigated the expression and function of YAP in the proliferation and apoptosis of activated HSCs. We found that YAP expression was increased in liver fibrosis tissues from CCl₄-induced model mice and restored to normal level after stopping CCl₄ injection and 6 weeks of spontaneously recovery. YAP expression was elevated in HSC-T6 cells treated with TGF-β1 and recovered after MDI treatment. Silencing of YAP inhibited the activation and proliferation of HSC-T6 cells stimulated by TGF-β1. In addition, the apoptosis of activated HSC-T6 cells silenced for YAP was slightly enhanced. Furthermore, over-expression of YAP repressed the reversion of activated HSC-T6 cells mediated by MDI reversal. We found that HSC-T6 cells activated by TGF-β1 showed higher levels of nuclear YAP compared with MDI-treated cells, indicating that YAP was activated in HSC-T6 cells treated by TGF-β1. We also found that loss of YAP attenuated Wnt/β-catenin pathway activity in activated HSC-T6 cells. Treatment of VP, an inhibitor of the YAP-TEAD complex, reduced both activation and proliferation of HSC-T6 cells and increased apoptosis. Together these results indicated that reduced expression of YAP contributes to acquisition of the quiescent phenotype in HSCs. Our results suggest that YAP may be a useful target in HSCs activation and reversion.

Molecular Targets in Hepatocarcinogenesis and Implications for Therapy

Hepatocarcinogenesis comprises of multiple, complex steps that occur after liver injury and usually involve several pathways, including telomere dysfunction, cell cycle, WNT/β-catenin signaling, oxidative stress and mitochondria dysfunction, autophagy, apoptosis, and AKT/mTOR signaling. Following liver injury, gene mutations, accumulation of oxidative stress, and local inflammation lead to cell proliferation, differentiation, apoptosis, and necrosis. The persistence of this vicious cycle in turn leads to further gene mutation and dysregulation of pro- and anti-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, IL-10, IL-12, IL-13, IL-18, and transforming growth factor (TGF)-β, resulting in immune escape by means of the NF-κB and inflammasome signaling pathways. In this review, we summarize studies focusing on the roles of hepatocarcinogenesis and the immune system in liver cancer. In addition, we furnish an overview of recent basic and clinical studies to provide a strong foundation to develop novel anti-carcinogenesis targets for further treatment interventions.

Hippo pathway affects survival of cancer patients: extensive analysis of TCGA data and review of literature

The disruption of the Hippo pathway occurs in many cancer types and is associated with cancer progression. Herein, we investigated the impact of 32 Hippo genes on overall survival (OS) of cancer patients, by both analysing data from The Cancer Genome Atlas (TCGA) and reviewing the related literature. mRNA and protein expression data of all solid tumors except pure sarcomas were downloaded from TCGA database. Thirty-two Hippo genes were considered; for each gene, patients were dichotomized based on median expression value. Survival analyses were performed to identify independent predictors, taking into account the main clinical-pathological features affecting OS. Finally, independent predictors were correlated with YAP1 oncoprotein expression. At least one of the Hippo genes is an independent prognostic factor in 12 out of 13 considered tumor datasets. mRNA levels of the independent predictors coherently correlate with YAP1 in glioma, kidney renal clear cell, head and neck, and bladder cancer. Moreover, literature data revealed the association between YAP1 levels and OS in gastric, colorectal, hepatocellular, pancreatic, and lung cancer. Herein, we identified cancers in which Hippo pathway affects OS; these cancers should be candidates for YAP1 inhibitors development and testing.

Standard CD44 modulates YAP1 through a positive feedback loop in hepatocellular carcinoma

High expression levels of CD44 and YAP have been identified as poor prognostic factors in hepatocellular carcinoma (HCC). However, the mechanistic relationship between CD44 and YAP during HCC tumorigenesis remains largely unknown. To investigate the mutual regulation between standard CD44 (CD44S) and YAP1 in HCC cell lines and tissue samples, CD44S and YAP1 expression in 40 pairs of tumor samples and matched distal normal tissues from HCC patients was examined by immunohistochemical staining. High expression of either CD44S or YAP1 was associated with a younger age and worse pathology grade. In addition, high levels of CD44S and YAP1 were associated with increased vascular invasion and more severe liver cirrhosis, respectively. CD44S expression was positively correlated with YAP1 expression in these HCC tissues. In vitro experiments suggested that CD44S could positively regulate the expression of YAP1 and its target genes via the PI3K/Akt pathway in HCC cells. Moreover, CD44S is regulated by the YAP1/TEAD axis. These results reveal a novel positive feedback loop involving CD44S and YAP1, in which CD44S functions as both an upstream regulator and a downstream effector of YAP1 in HCC. This feedback loop might constitute a broadly conserved module for regulating cell proliferation and invasion during HCC tumorigenesis. Blocking this positive feedback loop that involves CD44S and YAP1 might represent a new approach for HCC treatment.

C21 steroid-enriched fraction refined from Marsdenia tenacissima inhibits hepatocellular carcinoma through the coordination of Hippo-Yap and PTEN-PI3K/AKT signaling pathways

Marsdenia tenacissimae extraction (MTE), a traditional herbal medicine, has exhibited anti-tumor effects on a variety of cancers. However, its effectiveness and the mechanism of action in Hepatocellular carcinoma (HCC) has not been fully understood. In the present study, we demonstrate that C21 steroid-enriched fraction from MTE, which contains five main C21 steroids (FR5) exhibits obvious pharmacological activities on HCC cells in vitro and in vivo. FR5 induces apoptosis and inhibits proliferation and migration of HepG2 and Bel7402 cells in a dose and time dependent manner. Furthermore, in HCC cells, we found that FR5 inhibits Hippo pathway, leading to inactivation of YAP and increase of PTEN. Enhanced PTEN results in the inhibition of PI3K/AKT signaling pathway, inhibiting cell proliferation by FR5 and FR5-induced apoptosis. Moreover, it was proved that FR5 treatment could inhibit tumor growth in a HCC xenograft mouse model, and immunohistochemistry results showed FR5 treatment resulted in down-regulation of Bcl-2 and YAP, and up-regulation of PTEN and PI3K. Taken together, we found that FR5 effectively inhibits proliferation and induces apoptosis of HCC cells through coordinated inhibition of YAP in the Hippo pathway and AKT in the PI3K-PTEN-mTOR pathway, and suggest FR5 as a potential therapy for HCC.

Overexpression of Yes-associated protein and its association with clinicopathological features of hepatocellular carcinoma: A meta-analysis

BACKGROUND

Yes-associated protein (YAP) overexpression is reported to be associated with risk of hepatocellular carcinoma (HCC) but current studies have not explored the relationship between YAP expression with HCC clinicopathological features.

METHODS

To assess these associations, a meta-analysis was performed which included four eligible studies including 391 HCC cases and 334 controls. There were eight eligible studies to investigate the association between YAP expression in HCC and clinicopathological features of liver cancer patients. Literature was obtained from PubMed, Embase, Wangfang and China National Knowledge Infrastructure.

RESULTS

Analysis indicated that YAP expression in HCC was greater than in adjacent non-tumour tissue (odds ratio [OR], 15.80, 95% confidence interval [CI], 10.53-23.70, P<.00001; heterogeneity=.30). YAP overexpression in HCC was significantly associated with vascular invasion (OR, 2.21, 95% CI, 11.64-2.97, P<.00001, heterogeneity=.10), less cellular differentiation (OR, 2.38, 95% CI, 1.61-3.51, P<.00001, heterogeneity=.333), tumours larger than 5 cm (OR, 2.52, 95% CI, 1.75-3.62, P<.00001; heterogeneity=.17) and TNM tumour stage I + II (OR, 0.44, 95% CI, 0.28-0.75, P=.00003, heterogeneity=.12).

CONCLUSIONS

Overexpression of YAP contributes to HCC formation, and its overexpression is associated with vascular invasion, low cellular differentiation tumours larger than 5 cm and TNM tumour stage III + IV.

Dual roles of yes-associated protein (YAP) in colorectal cancer

Yes-associated protein (YAP) is a downstream effector molecule of a newly emerging tumour suppressor pathway called the Hippo pathway. YAP is a transcriptional co-activator and mis-expressed in various cancers, including colorectal cancer (CRC). Accumulating studies show that the high expression of nuclear YAP is linked with tumour progression and decreased survival. Nuclear YAP can interact with other transcription factors to promote cancer cell proliferation, apoptosis, metastasis and maintenance of stemness. Therefore, YAP has the potential to be a tumour biomarker or therapeutic target for CRC. However, recently, a number of studies have supported a contradictory role for YAP as a tumour suppressor, demonstrating inhibition of the tumorigenesis of CRC, involvement in promoting cell apoptosis, and inhibiting the maintenance of intestinal stem cells and inflammatory activity. In these studies, high expression of YAP was highly correlated with worse survival in CRC. In this review, we will comprehensively summarize and analyse these paradoxical reports, and discuss both the oncogenic and tumour suppressor functions of YAP in the differential status of CRC progression. Further investigation into the mechanisms responsible for the dual function of YAP will be of great value in the prevention, early diagnosis, and therapy of CRC.