Extensive epidemiological studies have revealed that nearly 25% of the premature mortality from lung cancer is attributed to regional haze caused by a high level of fine particulate matter (PM

Cell adhesion molecule-1 (CADM1) is a member of the immunoglobulin superfamily that functions as a tumor suppressor of lung tumors. We herein demonstrated that CADM1 interacts with Hippo pathway core kinases and enhances the phosphorylation of YAP1, and also that the membranous co-expression of CADM1 and LATS2 predicts a favorable prognosis in lung adenocarcinoma. CADM1 significantly repressed the saturation density elevated by YAP1 overexpression in NIH3T3 cells. CADM1 significantly promoted YAP1 phosphorylation on Ser 127 and downregulated YAP1 target gene expression at confluency in lung adenocarcinoma cell lines. Moreover, CADM1 was co-precipitated with multiple Hippo pathway components, including the core kinases MST1/2 and LATS1/2, suggesting the involvement of CADM1 in the regulation of the Hippo pathway through cell-cell contact. An immunohistochemical analysis of primary lung adenocarcinomas (n = 145) revealed that the histologically low-grade subtype frequently showed the membranous co-expression of CADM1 (20/22, 91% of low-grade; 61/91, 67% of intermediate grade; and 13/32, 41% of high-grade subtypes; P < 0.0001) and LATS2 (22/22, 100% of low-grade; 44/91, 48% of intermediate-grade; and 1/32, 3% of high-grade subtypes; P < 0.0001). A subset analysis of disease-free survival revealed that the membranous co-expression of CADM1 and LATS2 was a favorable prognosis factor (5-year disease-free survival rate: 83.8%), even with nuclear YAP1-positive expression (5-year disease-free survival rate: 83.7%), whereas nuclear YAP1-positive cases with the negative expression of CADM1 and LATS2 had a poorer prognosis (5-year disease-free survival rate: 33.3%). These results indicate that the relationship between CADM1 and Hippo pathway core kinases at the cell membrane is important for suppressing the oncogenic role of YAP1.

OBJECTIVES: Thyroid carcinoma (TC) represents a malignant neoplasm affecting the thyroid. Current treatment strategies include the removal of part of the thyroid; however, this approach is associated with a significant risk of developing hypothyroidism. In order to adequately understand the expression profiles of TNRC6C-AS1 and STK4 and their potential functions in TC, an investigation into their involvement with Hippo signalling pathway and the mechanism by which they influence TC apoptosis and autophagy were conducted.
METHODS: A microarray analysis was performed to screen differentially expressed lncRNAs associated with TC. TC cells were employed to evaluate the role of TNRC6C-AS1 by over-expression or silencing means. The interaction of TNRC6C-AS1 with methylation of STK4 promoter was evaluated to elucidate its ability to elicit autophagy, proliferation and apoptosis.
RESULTS: TNRC6C-AS1 was up-regulated while STK4 was down-regulated, where methylation level was elevated. STK4 was verified as a target gene of TNRC6C-AS1, which was enriched by methyltransferase. Methyltransferase's binding to STK4 increased expression of its promoter. Over-expressed TNRC6C-AS1 inhibited STK4 by promoting STK4 methylation and reducing the total protein levels of MST1 and LATS1/2. The phosphorylation of YAP1 phosphorylation was decreased, which resulted in the promotion of SW579 cell proliferation and tumorigenicity.
CONCLUSION: Based on our observations, we subsequently confirmed the anti-proliferative, pro-apoptotic and pro-autophagy capabilities of TNRC6C-AS1 through STK4 methylation via the Hippo signalling pathway in TC.

The Hippo pathway is a tumour-suppressive pathway and its inactivation is known to be associated with progression and metastasis of various cancers. LATS1/2 (large tumour suppressor homolog 1 and 2), YAP1 (Yes-associated protein 1), and TEAD4 (TEA domain-containing sequence-specific transcription factors 4) are core components of the Hippo pathway, and their prognostic roles have not yet been studied in advanced gastric cancers (AGCs). A total of 318 surgically resected AGCs were retrieved. Immunolabelling for LATS1/2, YAP1 and TEAD4 was compared with clinicopathological factors including patients' survival. High expression of YAP1 and TEAD4 was identified in 108 (34.0%) and 131 (41.2%) cases, respectively, and 223 (70.1%) cases were negative for LATS1/2 expression. High YAP1 expression was significantly correlated with the presence of perineural invasion (p=0.032). High YAP1 and high TEAD4 expressions were significantly associated with poor overall survival (p<0.001 and p=0.003, respectively), and negative LATS1/2 expression was also associated with poor overall survival (p=0.002). Combined expression of YAP1

BACKGROUND Colorectal carcinoma (CRC) is one of the most frequently diagnosed malignancies. Cucurbitacin B (CuB) is a natural compound isolated from herbs and shows anticancer activity in several cancers. MATERIAL AND METHODS Here, we analyzed the effects of different CuB concentrations on the proliferative and invasive behaviors of CRC cells using MTT, clonogenic assay, Transwell invasion, and wound healing assays. Flow cytometry was performed to measure the apoptotic effects of CuB on CRC cells. Western blot and real-time PCR were used to investigate the expression of apoptosis and Hippo-YAP signaling pathway proteins. RESULTS CuB inhibited the proliferation and invasion of CRC cells while promoting apoptosis. In addition, the Western blot and real-time PCR results indicated that CuB suppressed YAP expression and its downstream target genes Cyr 61 and c-Myc in CRC cells. To assess the underlying mechanism, we investigated the upstream regulating factor LATS1, and the results revealed that CuB upregulated LATS1 expression in CRC cells. CONCLUSIONS In conclusion, our findings uncovered a novel therapeutic mechanism of CuB and suggest that there is therapeutic potential and feasibility in developing novel YAP inhibitors for cancer treatment.

Multiple cancer signalling networks take part in regulatory crosstalks with the Hippo tumour suppressor pathway through the transcriptional cofactor Yes-associated protein (YAP). Nevertheless, how YAP is controlled by pathway crosstalks in tumourigenesis remains poorly understood. Here, we performed a targeted kinase inhibitor screen in human cancer cells to identify novel Hippo pathway regulators. Notably, we identified the nerve growth factor (NGF) receptor tyrosine kinase (NTRK1), a molecule not previously associated with Hippo signalling. NTRK1 inhibition decreased YAP-driven transcription, cancer cell proliferation and migration. Furthermore, using a complementary functional genomics approach and mouse xenograft models, we show that NTRK1 regulates YAP oncogenic activity in vivo. Mechanistically, NTRK1 inhibition was found to induce large suppressor kinase 1 (LATS1) phosphorylation and to control YAP subcellular localization. Taken together, these results provide compelling evidence of crosstalks between the NGF-NTRK1 and Hippo cancer pathways.

Although cell polarity plays an important role in epithelial tumorigenesis, the consequence of polarity protein loss in prostatic tumorigenesis and the underlying mechanisms remain unclear. Using conditional knockout mouse models, we found in the current study that loss of polarity protein Par3 increases prostatic epithelial cell growth, elevates symmetrical cell divisions in basal cells, and randomizes spindle orientation in luminal cells, causing the development of high-grade prostatic intraepithelial neoplasia (PIN). Mechanistically, loss of Par3 dissociates the Par3/merlin/Lats1 complex, consequently inhibiting phosphorylation of Lats1 to attenuate the Hippo pathway. Furthermore, attenuated Hippo pathway enhances nuclear translocation of Yes-associated protein (YAP), which promotes cell proliferation and symmetrical cell divisions through transcriptional activation of Ki-67 and Sox2. In addition, Lats1 dephosphorylation impairs its interaction with G protein signaling modulator 2 (GPSM2, which is also known as LGN) that causes randomization of spindle orientation in luminal cells. Interestingly, co-deletion of Par3 and Lats1 for complete blockade of the Hippo pathway in mice results in prostate tumor initiation, whereas co-deletion of Par3 and YAP for disrupting YAP nuclear translocation reverses the phenotypes to a relatively normal state. Therefore, our findings highlight combination of Par3 loss and blockade of the Hippo pathway as a novel mechanism for prostatic tumorigenesis.

Targeted therapy has a pivotal role for the treatment of liver cancer. The aim of this current study was to examine the effects of decursin on the growth of HepG2 cells and the underlying mechanisms. Our present study showed that treatment of HepG2 cells with decursin significantly inhibited the growth of HepG2 cells by suppressing cell proliferation, cell cycle arresting, and promoting apoptosis in a dose- and time-dependent manner. Most significantly, administration of decursin dramatically impeded in vivo tumor growth in nude mice. Mechanically, it is noteworthy that decursin treatment provoked degradation of YAP by upregulating the expression of phosphorylated LATS1 and βTRCP. Moreover, apoptosis caused by decursin could be reversed by a selective MST1/2 inhibitor, XMU-MP-1, suggesting that decursin may function through Hippo/YAP signaling. This study has identified that decursin is a potential agent for HCC therapy, and further research should be undertaken to facilitate its therapeutic application.

BACKGROUND: In this research, we aimed to investigate the biological functions of LIM domain only 3 (LMO3) in hepatocellular carcinoma (HCC) and uncover the underlying molecular mechanism in it.
METHODS: HCC tissue microarray (n = 180) was used to analyze the correlation between LMO3 expression and clinicopathological findings. In vitro transwell matrigel invasion assay and annexin V anoikis assay in HCC cells were conducted to investigate LMO3 related biological functions. In vivo intrahepatic and lung metastasis models were used to determine the role of LMO3 in HCC metastasis. Quantitative real-time PCR, western blotting and immunohistochemical staining were performed to investigate the expression and mechanism of LMO3 in HCC.
RESULTS: We found that the expression of LMO3 was significantly upregulated in HCC tissues, and it was closely related to clinicopathological findings and patient prognoses. Knockdown of LMO3 suppressed the invasion and anoikis inhibition of HCC cells in vitro. Meanwhile, the metastasis of SMMC-7721 cells was also suppressed by LMO3 knockdown in vivo. Furthermore, we found that LMO3 knockdown increased the phosphorylation of YAP and LATS1, and decrease Rho GTPases activities. LMO3 directly interacted with LATS1, and thus suppressed Hippo signaling. Recombinant LMO3 (rLMO3) protein administration decreased the phosphorylation of YAP and LATS1, and increased Rho GTPases activities. The inhibitors of the Hippo pathway abrogated rLMO3 protein-induced HCC cell invasion and anoikis inhibition.
CONCLUSIONS: These results suggest that LMO3 promotes HCC cell invasion and anoikis inhibition by interacting with LATS1 and suppressing Hippo signaling. LMO3 may serve as a potential therapeutic target for HCC in future.

In most solid tumors, the Hippo pathway is inactivated through poorly understood mechanisms that result in the activation of the transcriptional regulators, YAP and TAZ. Here, we identify NUAK2 as a YAP/TAZ activator that directly inhibits LATS-mediated phosphorylation of YAP/TAZ and show that NUAK2 induction by YAP/TAZ and AP-1 is required for robust YAP/TAZ signaling. Pharmacological inhibition or loss of NUAK2 reduces the growth of cultured cancer cells and mammary tumors in mice. Moreover, in human patient samples, we show that NUAK2 expression is elevated in aggressive, high-grade bladder cancer and strongly correlates with a YAP/TAZ gene signature. These findings identify a positive feed forward loop in the Hippo pathway that establishes a key role for NUAK2 in enforcing the tumor-promoting activities of YAP/TAZ. Our results thus introduce a new opportunity for cancer therapeutics by delineating NUAK2 as a potential target for re-engaging the Hippo pathway.

BACKGROUND: Phosphatase and tensin homolog (PTEN) is an important tumor suppressor gene, and its encoded protein has activities of both a protein phosphatase and a lipid phosphatase. However, the substitution effect of protein phosphatase activity remains unclear. PI3K/Akt is the most common pathway negatively regulated by PTEN. The Hippo and PI3K/Akt pathways have a joint effect in regulating cell proliferation and apoptosis. Therefore, how PTEN lipid phosphatase inactivation contributes to the occurrence and development of gastric cancer and the potential role of the Hippo and PI3K/Akt pathways in PTEN lipid phosphatase inactivation mediated gastric tumorigenesis remain to be explored.
METHODS: Immunohistochemical staining was performed to detect the expression of p-PTEN and YAP in a gastric cancer tissue microarray. Stable cell lines expressing a wild-type or dominant-negative mutant PTEN were established. The proliferation and migration of stable cells were detected by MTT, BrdU, and colony-formation, transwell assay and high content analysis in vitro, and tumor growth differences were observed in xenograft nude mice. Changes in the expression of key molecules in the Hippo and Akt signaling pathways were detected by western blot. Nuclear-cytoplasm separation, immunofluorescence and coimmunoprecipitation analyses were conducted to explore the dysregulation of Hippo in the stable cell lines.
RESULTS: PTEN lipid phosphatase inactivation strongly promoted the proliferation and migration of gastric cancer cells in vitro and tumor growth in vivo. A immunohistochemical analysis of gastric cancer tissues revealed a significant correlation between phosphorylated PTEN and nuclear YAP expression, and both were determined to be independent prognostic factors for gastric cancer. Mechanistically, PTEN lipid phosphatase inactivation abolished the MOB1-LATS1/2 interaction, decreased YAP phosphorylation and finally promoted YAP nuclear translocation, which enhanced the synergistic effect of YAP-TEAD, thus inducing cell proliferation and migration. Moreover, PTEN lipid phosphatase inactivation promoted the PI3K/Akt pathway, and disruption of YAP-TEAD-driven transcription decreased the activation of Akt in a dose-dependent manner.
CONCLUSIONS: Taken together, our findings indicate that PTEN lipid phosphatase inactivation links the Hippo and PI3K/Akt pathways to promote gastric tumorigenesis and cancer development.

The purpose of the present study was to investigate the mechanism by which epigallocatechin‑3‑gallate (EGCG) inhibits the biological behaviors of the tongue squamous cell carcinoma (TSCC) through the Hippo‑tafazzin (TAZ) signaling pathway and to provide insights into molecular targeted therapy in TSCC. CAL27 and SCC15 cells were treated with different concentrations of EGCG for 24 h. Cell proliferation was determined using Cell‑Counting Kit‑8 and EdU assays. Cell apoptosis was evaluated by flow cytometry. Cell migration and invasion were measured using scratch and Transwell assays, respectively. Furthermore, protein levels of associated target genes were detected using a western blot assay. It was demonstrated that EGCG affected biological behaviors of CAL27 and SCC15 cells in concentration‑ and time‑dependent manners. In addition, EGCG decreased the protein levels of TAZ, LATS1, MOB1 and JNK. Overexpression of TAZ alleviated the effect of EGCG on CAL27 cells. Furthermore, the combination of EGCG and simvastatin inhibited the proliferation, migration and invasion, and promoted apoptosis significantly compared with single treatment in CAL27 cells. The results of the present study suggested that EGCG affects proliferation, apoptosis, migration and invasion of TSCC through the Hippo‑TAZ signaling pathway.

Glioblastomas (GBM) are the most aggressive brain cancers without effective therapeutics. The Hippo pathway transcriptional coactivators YAP/TAZ were implicated as drivers in GBM progression and could be therapeutic targets. Here we found in an unbiased screen of 1650 compounds that amlodipine is able to inhibit survival of GBM cells by suppressing YAP/TAZ activities. Instead of its known function as an L-type calcium channel blocker, we found that amlodipine is able to activate Ca

Down-regulation of the meningioma-associated protein (MAC30) gene has been found in many solid cancers. This study was carried out to determine the roles and the mechanisms of MAC30 in breast cancer. We used our own data and a public database to analyze the MAC30 mRNA and protein levels in breast cancer tissues. In addition, we established MAC30 knockdown breast cancer cells using MAC30 siRNA. The roles of MAC30 were detected by using the Soft agar assay, Annexin-V-FITC/PI double staining and the Transwell assay. Western blotting was used to analyze the potential mechanism(s) of MAC30 in these cells. We found that MAC30 mRNA and protein were higher in the cancer tissues compared to the matched normal tissues. MAC30 expression was associated with tumor size, tumor differentiation and estrogen receptor (ER) status. Overall survival rate of the patients with low MAC30 expression was obviously higher than the ones with high expression. The apoptotic ratio was lower in MDA-MB-231 and MDA-MB-157 cells with MAC30 expression. By Western blot analysis, we found that increased levels of phosphorylated YAP1, MST1 and LATS1 after MAC30 siRNA transfection in these two cells. In summary, we demonstrate that MAC30 knockdown is involved in the activation of the Hippo signaling pathway.

BACKGROUND: Fascin is a F-actin bundling protein and its overexpression is correlated with poor prognosis and increases metastatic potential in a number of cancers. But underlying function and mechanism of fascin on tumorigenesis in melanoma remain elusive.
METHODS: The melanoma cell lines WM793 and WM39 were employed for the soft agar and sphere formation assay. Quantitative RT-PCR and Western blot were performed for identifying the gene expression at mRNA and protein levels, respectively. Co-IP and in vitro GST pulldown experiments were used to test the interaction between fascin and MST2.
RESULTS: Fascin regulates tumorigenesis and cancer cell stemness in melanoma through inhibition of the Hippo pathway kinase MST2 and the activation of transcription factor TAZ. Our data showed that fascin interacts with the kinase domain of MST2 to inhibit its homodimer formation and kinase activity. Depletion of fascin led to increase of p-LATS level and decrease of TAZ, but not YAP. We also demonstrated that fascin regulates melanoma tumorigenesis independent of its actin-bundling activity.
CONCLUSIONS: Fascin is a new regulator of the MST2-LATS-TAZ pathway and plays a critical role in melanoma tumorigenesis. Inhibition of fascin reduces melanoma tumorigenesis and stemness, and thus fascin could be a potential therapeutic target for this malignancy.

The Hippo pathway effector, Yes-associated protein (YAP), is a transcriptional coactivator implicated in cholangiocarcinoma (CCA) pathogenesis. YAP is known to be regulated by a serine/threonine kinase relay module (MST1/2-LATS1/2) culminating in phosphorylation of YAP at Serine 127 and cytoplasmic sequestration. However, YAP also undergoes tyrosine phosphorylation, and the role of tyrosine phosphorylation in YAP regulation remains unclear. Herein, YAP regulation by tyrosine phosphorylation was examined in human and mouse CCA cells, as well as patient-derived xenograft (PDX) models. YAP was phosphorylated on tyrosine 357 (Y357) in CCA cell lines and PDX models. SRC family kinase (SFK) inhibition with dasatinib resulted in loss of YAPY357 phosphorylation, promoted its translocation from the nucleus to the cytoplasm, and reduced YAP target gene expression, including cell lines expressing a LATS1/2-resistant YAP mutant in which all serine residues were mutated to alanine. Consistent with these observations, precluding YAPY357 phosphorylation by site-directed mutagenesis (YAPY357F) excluded YAP from the nucleus. Targeted siRNA experiments identified LCK as the SFK that most potently mediated YAPY357 phosphorylation. Likewise, inducible CRISPR/Cas9-targeted LCK deletion decreased YAPY357 phosphorylation and its nuclear localization. The importance of LCK in CCA biology was demonstrated by clinical observations suggesting LCK expression levels were associated with early tumor recurrence following resection of CCA. Finally, dasatinib displayed therapeutic efficacy in PDX models.

Despite advances in surgery and chemotherapy, the prognosis of patients with hepatocellular carcinoma (HCC) remains poor. In the present study, the role of S100A1 in the progression of HCC was investigated. Immunohistochemical staining was used to measure the expression of S100A1 in HCC tissues. S100A1 was knocked down by siRNA. A battery of experiments was used to evaluate the biology functions of S100A1. It was found that S100A1 was upregulated in HCC tissues, and its upregulation was associated with a large tumor size, low differentiation and shorter survival time. The biological experiments demonstrated that S100A1 functions as an oncogene in HCC. It was also found that S100A1 knockdown enhanced the inhibitory effects of cisplatin on HCC cells. The results showed that the downregulation of S100A1 induced the phosphorylation of yes‑associated protein (YAP), and treatment with CHX demonstrated that the downregulation of S100A1 accelerated YAP protein degradation. The downregulation of S100A1 did not alter the expression of mammalian sterile 20‑like kinase (MST)1/2 or phosphorylated MST1/2, but upregulated the phosphorylation of large tumor suppressor kinase 1 (LATS1). It was further confirmed that S100A1 interacted with LATS1. LATS1 depletion significantly reduced the effects of S100A1 on cell growth rate and apoptosis, and there was a positive correlation between phosphorylated LATS1 and S100A1 in clinical samples, indicating that LATS1 was responsible for the S100A1-induced changes in cancer cell growth and Hippo signaling. In conclusion, the results of the present study indicated that S100A1 functions as an oncogene and may be a biomarker for the prognosis of patients with HCC. S100A1 exerted its oncogenic function by interacting with LATS1 and activating YAP. S100A1 may serve as a target for novel therapies in HCC.

Breast cancer is one of the major challenges for women's health. However, the role and mechanisms of interleukins (ILs) on the progression of breast cancer are not well illustrated. Our present study revealed that the expressions of IL-6 and IL-8 were significantly increased in oestrogen receptor-negative (ER-) breast cancer cells. Increased expression of IL-6 was observed in 83.9% (26/31) ER- breast cancer tissues as compared with their matched adjacent normal tissues. In vitro studies indicated that IL-6 can significantly promote the migration and invasion of ER- breast cancer cells via increasing the dephosphorylation, nuclear translocation and transcriptional activities of YAP in breast cancer cells. Knockdown of YAP can attenuate IL-6-induced migration and invasion of cancer cells, suggesting that YAP plays an essential role in IL-6-induced malignancy of breast cancer cells. Furthermore, IL-6 treatment also decreased the phosphorylation of LATS1/2. The knockdown of LATS1/2 synergistically suppressed si-IL-6-induced deactivation of YAP. Targeted inhibition of IL-6/YAP can significantly suppress the invasion of ER- breast cancer cells. Collectively, our study revealed that IL-6 can trigger the malignancy of breast cancer cells via activation of YAP signals. Targeted inhibition of IL-6/YAP might be a novel therapeutic approach for the treatment of ER- breast cancer.

Nowadays, risk factors of triple-negative breast cancer (TNBC) metastasis are not well identified. Our present study reveals that an industrial chemical, bisphenol S (BPS), can promote the migration, but not the proliferation, of TNBC cells in vitro. BPS activates YAP, a key effector of Hippo pathway, by inhibiting its phosphorylation, which promotes YAP nuclear accumulation and up-regulates its downstream genes such as CTGF and ANKRD1. Inhibition of YAP blocks the BPS-triggered cell migration and up-regulation of fibronectin (FN) and vimentin (Vim). BPS rapidly decreases the phosphorylation levels of LATS1 (Ser909) in TNBC cells, which regulates the activation and functions of YAP. Silencing LATS1/2 by siRNA increases BPS-induced dephosphorylation of YAP and extended the half-life of YAP protein. Inhibition of G protein-coupled estrogen receptor 1 (GPER) and its downstream PLCβ/PKC signals attenuate the effects of BPS-induced YAP dephosphorylation and CTGF up-regulation. Targeted inhibition of GPER/YAP inhibits BPS-induced migration of TNBC cells. Collectively, we reveal that GPER/Hippo-YAP signal is involved in BPS-induced migration of TNBC cells.

The Hippo pathway, initially identified through screenings for mutant tumor suppressors in Drosophila, is an evolutionarily conserved signaling pathway that controls organ size by regulating cell proliferation and apoptosis. Abnormal regulation of the Hippo pathway may lead to cancer in mammals. As the major downstream effectors of the Hippo pathway, unphosphorylated Yes-associated protein (YAP) and its homolog transcriptional co-activator TAZ (also called WWTR1) (hereafter called YAP/TAZ) are translocated into the nucleus. In the nucleus, in order to induce target gene expression, YAP/TAZ bind to the TEA domain (TEAD) proteins, and this binding subsequently promotes cell proliferation and inhibits apoptosis. In contrast, as key regulators of tumorigenesis and development, YAP/TAZ are phosphorylated and regulated by multiple molecules and pathways including Lats1/2 of Hippo, Wnt and G-protein-coupled receptor (GPCR) signaling, with a regulatory role in cell physiology, tumor cell development and pathological abnormalities simultaneously. In particular, the crucial role of YAP/TAZ in tumors ensures their potential as targets in designing anticancer drugs. To date, mounting research has elucidated the suppression of YAP/TAZ via effective inhibitors, which significantly highlights their application in cancer treatment. In the present review, we focus on the functions of YAP/TAZ in cancer, discuss their potential as new therapeutic target for tumor treatment, and provide valuable suggestions for further study in this field.

Hippo (Hpo) signaling pathway controls tissue growth by regulating the subcellular localization of Yorkie (Yki)/Yap via a cytoplasmic kinase cassette containing an upstream kinase Hpo/MST1/2 and a downstream kinase Warts (Wts)/Lats1/2. Here we show that PRP4K, a kinase involved in mRNA splicing, phosphorylates Yki/Yap in the nucleus to prevent its nuclear accumulation and restrict Hpo pathway target gene expression. PRP4K inactivation accelerates whereas excessive PRP4K inhibits Yki-driven tissue overgrowth. PRP4K phosphorylates a subset of Wts/Lats1/2 sites on Yki/Yap to inhibit the binding of Yki/Yap to the Scalloped (Sd)/TEAD transcription factor and exclude Yki/Yap nuclear localization depending on nuclear export. Furthermore, PRP4K inhibits proliferation and invasiveness of cultured breast cancer cells and its high expression correlates with good prognosis in breast cancer patients. Our study unravels an unanticipated layer of Hpo pathway regulation and suggests that PRP4K-mediated Yki/Yap phosphorylation in the nucleus provides a fail-safe mechanism to restrict aberrant pathway activation.

YAP and TAZ play oncogenic roles in various organs, but the role of YAP/TAZ in gastric cancer remains unclear. Here, we show that YAP/TAZ activation initiates gastric tumorigenesis

Cardiovascular disease remains the leading cause of death around the globe. Cardiac deterioration is associated with irreversible cardiomyocyte loss. Understanding how the cardiovascular system develops and the pathological processes of cardiac disease will contribute to finding novel and preventive therapeutic methods. The canonical Hippo tumor suppressor pathway in mammalian cells is primarily composed of the MST1/2-SAV1-LATS1/2-MOB1-YAP/TAZ cascade. Continuing research on this pathway has identified other factors like RASSF1A, Nf2, MAP4Ks, and NDR1/2, further enriching our knowledge of the Hippo-YAP pathway. YAP, the core effecter of the Hippo pathway, may accumulate in the nucleus and initiate transcriptional activity if the pathway is inhibited. The role of Hippo signaling has been widely investigated in organ development and cancers. A heart of normal size and function which is critical for survival could not be generated without the proper regulation of the Hippo tumor suppressor pathway. Recent research has demonstrated a novel role of Hippo signaling in cardiovascular disease in the context of development, hypertrophy, angiogenesis, regeneration, apoptosis, and autophagy. In this review, we summarize the current knowledge of how Hippo signaling modulates pathological processes in cardiovascular disease and discuss potential molecular therapeutic targets.

Hepatoblastoma (HB), as a common pediatric liver malignancy, is composed of a variety of subgroups with different clinical outcomes. Long-noncoding RNA (lncRNA) has crucial roles in cancer biology. However, the association between lncRNA and HB has not been fully investigated. In this study, we screened lncRNA expression profiles that were annotated from the GSE75271 dataset. A total of 225 differentially expressed lncRNAs (DELs) were identified based on comparison between three prognostic subgroups, and seven of them (XR_241302, XR_923061, NR_038322, XR_951687, XR_934593, NR_120317 and XR_93406) that exhibited highly predictive accuracies were selected for functional analysis. Weighted gene correlation network analysis (WGCNA) was employed to predict the biological functions of the seven DELs. The Hippo-YAP signaling pathway was predicted to be the most statistically significant predicted pathway associated with the seven DELs. Furthermore, we performed in vitro experiments to validate the biological function of one DEL, NR_120317 (LINC01314). Our results showed decreased proliferation and migration activities of HB cells overexpressing LINC01314. Moreover, mechanistic investigations revealed that LINC01314 overexpression inhibited nuclear translocation of YAP, by inducing MST1 expression and promoting phosphorylation of LATS1 and YAP, consequently downregulating the expression of cell cycle regulatory proteins (MCM7 and cyclin D1). Taken together, our findings provide evidence for LINC01314 as a potential biomarker and anti-cancer therapeutic target in patients with HB.

The Hippo pathway plays a critical role in organ size control, tissue homeostasis and tumor genesis through its key transcription regulator Yes-associated protein1 (YAP1), but the mechanism underlying its role in lung cancer is unclear. We hypothesized that YAP1 influences FGFR1 signaling to maintain cancer stem-like cell (CSC) properties in FGFR1-amplified lung cancer. In support of this, our data confirms that expression levels of YAP1 are positively associated with those of FGFR1 in clinical lung carcinoma samples as measured by real-time PCR, western blot, and immunohistochemistry (IHC) staining. Mechanistically, YAP1 up-regulates FGFR1 expression at the level of promoter through the TEAD binding site while bFGF/FGFR1 induces YAP1 expression via large tumor suppressors 1(LATS1). In addition, the absence of YAP1 abolishes self-renewal ability in lung cancer. Furthermore, an orthotropic mouse model highlights the function of YAP1 in the initiation and metastasis of lung cancer. Verteporfin, a YAP1 inhibitor, effectively inhibits both YAP1 and FGFR1 expression in lung cancer. Thus, we conclude that YAP1 is a potential therapeutic target for lung cancer. Combined targeting of YAP1 and FGFR1 may provide benefits to patients with FGFR1-amplified lung cancer.

One of the most common head and neck cancers is laryngeal squamous cell carcinoma (LSCC). LSCC exhibits high mortality rates and has a poor prognosis. The molecular mechanisms leading to the development and progression of LSCC are not entirely clear despite genetic and therapeutic advances and increased survival rates. In this study, a total of 116 differentially expressed genes (DEGs), including 11 upregulated genes and 105 downregulated genes, were screened from LSCC samples and compared with adjacent noncancerous. Statistically significant differences (log 2-fold difference > 0.5 and adjusted P-value < .05) were found in this study in the expression between tumor and nontumor larynx tissue samples. Nine cancer hub genes were found to have a high predictive power to distinguish between tumor and nontumor larynx tissue samples. Interestingly, they also appear to contribute to the progression of LSCC and malignancy via the Jak-STAT signaling pathway and focal adhesion. The model could separate patients into high-risk and low-risk groups successfully when only using the expression level of mRNA signatures. A total of 4 modules (blue, gray, turquoise, and yellow) were screened for the DEGs in the weighted co-expression network. The blue model includes cancer-specific pathways such as pancreatic cancer, bladder cancer, nonsmall cell lung cancer, colorectal cancer, glioma, Hippo signaling pathway, melanoma, chronic myeloid leukemia, prostate cancer, and proteoglycans in cancer. Endocrine resistance (CCND1, RAF1, RB1, and SMAD2) and Hippo signaling pathway (CCND1, LATS1, SMAD2, and TP53BP2) could be of importance in LSCC, because they had high connectivity degrees in the blue module. Results from this study provide a powerful biomarker discovery platform to increase understanding of the progression of LSCC and to reveal potential therapeutic targets in the treatment of LSCC. Improved monitoring of LSCC and resulting improvement of treatment of LSCC might result from this information.

Tumor-associated macrophages (TAM) represent key regulators of the complex interplay between cancer and the immune microenvironment. Matricellular protein SPON2 is essential for recruiting lymphocytes and initiating immune responses. Recent studies have shown that SPON2 has complicated roles in cell migration and tumor progression. Here we report that, in the tumor microenvironment of hepatocellular carcinoma (HCC), SPON2 not only promotes infiltration of M1-like macrophages but also inhibits tumor metastasis. SPON2-α4β1 integrin signaling activated RhoA and Rac1, increased F-actin reorganization, and promoted M1-like macrophage recruitment. F-Actin accumulation also activated the Hippo pathway by suppressing LATS1 phosphorylation, promoting YAP nuclear translocation, and initiating downstream gene expression. However, SPON2-α5β1 integrin signaling inactivated RhoA and prevented F-actin assembly, thereby inhibiting HCC cell migration; the Hippo pathway was not noticeably involved in SPON2-mediated HCC cell migration. In HCC patients, SPON2 levels correlated positively with prognosis. Overall, our findings provide evidence that SPON2 is a critical factor in mediating the immune response against tumor cell growth and migration in HCC.

Claudins, the integral tight junction (TJ) proteins that regulate paracellular permeability and cell polarity, are frequently dysregulated in cancer; however, their role in neoplastic progression is unclear. Here, we demonstrated that knockout of Cldn18, a claudin family member highly expressed in lung alveolar epithelium, leads to lung enlargement, parenchymal expansion, increased abundance and proliferation of known distal lung progenitors, the alveolar epithelial type II (AT2) cells, activation of Yes-associated protein (YAP), increased organ size, and tumorigenesis in mice. Inhibition of YAP decreased proliferation and colony-forming efficiency (CFE) of Cldn18-/- AT2 cells and prevented increased lung size, while CLDN18 overexpression decreased YAP nuclear localization, cell proliferation, CFE, and YAP transcriptional activity. CLDN18 and YAP interacted and colocalized at cell-cell contacts, while loss of CLDN18 decreased YAP interaction with Hippo kinases p-LATS1/2. Additionally, Cldn18-/- mice had increased propensity to develop lung adenocarcinomas (LuAd) with age, and human LuAd showed stage-dependent reduction of CLDN18.1. These results establish CLDN18 as a regulator of YAP activity that serves to restrict organ size, progenitor cell proliferation, and tumorigenesis, and suggest a mechanism whereby TJ disruption may promote progenitor proliferation to enhance repair following injury.

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm resulting from clonal expansion of hematopoietic stem cells positive for the Philadelphia chromosome. The CML pathogenesis is associated with expression of the BCR-ABL1 oncogene, which encodes the Bcr-Abl protein with tyrosine kinase activity, promoting the leukemic cell exacerbated myeloproliferation and resistance to apoptosis. CML patients are usually treated with tyrosine kinase inhibitors (TKI), but some of them acquire resistance or are refractory to TKI. Thus, it is still relevant to elucidate the CML pathogenesis and seek new therapeutic targets, such as the Hippo signaling pathway and cell cycle regulatory genes from the Aurora kinase family. The present study quantified the expression level of genes encoding components of the Hippo signaling pathway (LATS1, LATS2, YAP, and TAZ), AURKA and AURKB in CML patients at different stages of the disease, who were resistant or sensitive to imatinib mesylate therapy, and in healthy individuals. The expression levels of the target genes were correlated with the CML Sokal's prognostic score. The most striking results were the LATS2 and AURKA overexpression in CML patients, the overexpression of TAZ and AURKB in CML patients at advanced phases and TAZ in CML IM-resistant. The development of drugs and/or identification of tumor markers for the Hippo signaling pathway and the Aurora kinase family, either alone or in combination, can optimize CML treatment by enhancing the susceptibility of leukemic cells to apoptosis and leading to a better disease prognosis.