LATS2 tumour specific mutations and down-regulation of the gene in non-small cell carcinoma

Hippo pathway in non-small cell lung cancer: mechanisms, potential targets, and biomarkers

Lung cancer is the primary contributor to cancer-related deaths globally, and non-small cell lung cancer (NSCLC) constitutes around 85% of all lung cancer cases. Recently, the emergence of targeted therapy and immunotherapy revolutionized the treatment of NSCLC and greatly improved patients' survival. However, drug resistance is inevitable, and extensive research has demonstrated that the Hippo pathway plays a crucial role in the development of drug resistance in NSCLC. The Hippo pathway is a highly conserved signaling pathway that is essential for various biological processes, including organ development, maintenance of epithelial balance, tissue regeneration, wound healing, and immune regulation. This pathway exerts its effects through two key transcription factors, namely Yes-associated protein (YAP) and transcriptional co-activator PDZ-binding motif (TAZ). They regulate gene expression by interacting with the transcriptional-enhanced associate domain (TEAD) family. In recent years, this pathway has been extensively studied in NSCLC. The review summarizes a comprehensive overview of the involvement of this pathway in NSCLC, and discusses the mechanisms of drug resistance, potential targets, and biomarkers associated with this pathway in NSCLC.

A review of nuclear Dbf2-related kinase 1 (NDR1) protein interaction as promising new target for cancer therapy

Nuclear Dbf2-related kinase 1 (NDR1) is a nuclear Dbf2-related (NDR) protein kinase family member, which regulates cell functions and participates in cell proliferation and differentiation through kinase activity. NDR1 regulates physiological functions by interacting with different proteins. Protein-protein interactions (PPIs) are crucial for regulating biological processes and controlling cell fate, and as a result, it is beneficial to study the actions of PPIs to elucidate the pathological mechanism of diseases. The previous studies also show that the expression of NDR1 is deregulated in numerous human cancer samples and it needs the context-specific targeting strategies for NDR1. Thus, a comprehensive understanding of the direct interaction between NDR1 and varieties of proteins may provide new insights into cancer therapies. In this review, we summarize recent studies of NDR1 in solid tumors, such as prostate cancer and breast cancer, and explore the mechanism of action of PPIs of NDR1 in tumors.

N6-Methyladenosine Reader YTHDF2 Enhances Non-Small-Cell Lung Cancer Cell Proliferation and Metastasis through Mediating circ_SFMBT2 Degradation

Objective. circ_SFMBT2 was reported to facilitate malignant progression in various cancers, but its function in non-small-cell lung cancer (NSCLC) has not been fully uncovered. This study aimed to investigate the effects of N6-methyladenosine (m6A) methylation of circ_SFMBT2 (circ_0017628) on non-small-cell lung cancer (NSCLC) and its underlying mechanisms. Methods. Paired tumor and noncancerous tissues from NSCLC patients were surgically collected from January 2020 to March 2021 in our hospital. The levels of circ_SFMBT2 and LATS2 in NSCLC and human bronchial epithelial cells were assayed with qRT-PCR. Overexpression or silencing of circ_SFMBT2, LATS2, or YTHDF2 was performed in the NSCLC cells. CCK-8, colony-forming, and transwell assays were performed to analyze cell proliferation, viability, and migration, respectively. Meanwhile, the expression of MMP-9, E-cadherin, vimentin, and the Hippo/YAP pathway components was examined by western blotting. The m6A enrichment in circ_SFMBT2 was verified using methylated RNA immunoprecipitation, and interaction between circ_SFMBT2 and YTHDF2 was assessed by RNA pull-down and immunoprecipitation assays. Results. Both circ_SFMBT2 and LATS2 were lowly expressed in NSCLC cells and tissues. A positive correlation of circ_SFMBT2 with LATS2 was identified, and circ_SFMBT2 was localized predominantly in the cytoplasm. circ_SFMBT2 overexpression negatively regulated cell proliferation, viability, migration, and epithelial-mesenchymal transition while promoting the Hippo/YAP pathway activation. Notably, knockdown of LATS2 effectively abrogated the inhibitory effects of circ_SFMBT2 overexpression on NSCLC cell malignancies. Besides, m6A was specifically enriched in circ_SFMBT2, and circ_SFMBT2 could bind to YTHDF2. Silencing of YTHDF2 led to an increase in circ_SFMBT2 expression while inhibiting the malignancy of cancer cells. Conclusion. Our results showed that YTHDF2 could facilitate NSCLC cell proliferation and metastasis via the Hippo/YAP pathway activation by mediating circ_SFMBT2 degradation.

LncRNA MYLK-AS1 acts as an oncogene by epigenetically silencing large tumor suppressor 2 (LATS2) in gastric cancer

Extensive studies showed the vital function of long noncoding RNAs (lncRNAs) in the pathological and physiological progression of tumors. Previous evidence has indicated that lncRNA MYLK Antisense RNA 1 (MYLK-AS1) acts as an oncogene to facilitate the progression of several tumors. Nevertheless, little is known about its biological role in gastric cancer (GC). Our report intended to probe the underlying mechanism and function of MYLK-AS1 in GC. Results revealed that MYLK-AS1 showed an upregulated level in GC. It was worth mentioning that upregulated MYLK-AS1 caused the unfavorable clinical outcome in GC patients. Functional assays indicated that MYLK-AS1 silencing retarded the proliferation, cell cycle, migration, and invasion in GC. Besides, in vivo assay validated that MYLK-AS1 deficiency also restrained tumor growth. Through in-depth mechanism exploration, MYLK-AS1 was uncovered to bind with wnhancer of zeste homolog 2 (EZH2), an epigenetic inhibitor, to inhibit the level of Large Tumor Suppressor 2 (LATS2), thereby exerting carcinogenicity. Conclusively, our research highlighted the importance of MYLK-AS1 in GC, indicating that MYLK-AS1 might be an effective biomarker for GC.

LncRNA CRNDE facilitates epigenetic suppression of CELF2 and LATS2 to promote proliferation, migration and chemoresistance in hepatocellular carcinoma

Our study aimed to investigate the expression, functional significance, and related mechanism of long noncoding RNA CRNDE (colorectal neoplasia differentially expressed) in hepatocellular carcinoma (HCC) pathogenesis. The resulted revealed that CRNDE was significantly overexpressed in HCC tissues and cell lines, and was statistically correlated with poor clinical outcome. CRNDE knockdown markedly decreased HCC cell proliferation, migration, and chemoresistance. In addition, in vivo experiments confirmed the suppressive effect of CRNDE knockdown on HCC progression. Mechanically, CRNDE directly bound to EZH2 (enhancer of zeste homolog), SUZ12 (suppressor of zeste 12), SUV39H1, and mediated their inhibition of tumor suppressor genes, including CUGBP Elav-like family member 2 (CELF2) and large tumor suppressor 2 (LATS2). CELF2 exerted tumor suppressive effect in HCC and was involved in CRNDE-mediated oncogenic effect. In addition, the oncogenic effects of CRNDE on HCC proliferation, migration and tumorigenesis, as well as its inhibition of Hippo pathway were abolished by LATS2 overexpression. Together, our work demonstrated the importance of CRNDE in HCC progression and elucidated the underlying molecular mechanisms. These findings provided new insights into HCC pathogenesis and chemoresistance mediated by CRNDE.

O-GlcNAcylation on LATS2 disrupts the Hippo pathway by inhibiting its activity

The Hippo pathway plays a crucial role in maintaining tissue homeostasis. Generally, activated Hippo pathway effectors, YAP/TAZ, induce the transcription of their negative regulators, NF2 and LATS2, and this negative feedback loop maintains homeostasis of the Hippo pathway. However, YAP and TAZ are consistently hyperactivated in various cancer cells, enhancing tumor growth. Our study found that LATS2, a direct-inhibiting kinase of YAP/TAZ and a core component of the negative feedback loop in the Hippo pathway, is modified with O-GlcNAc. LATS2 O-GlcNAcylation inhibited its activity by interrupting the interaction with the MOB1 adaptor protein, thereby activating YAP and TAZ to promote cell proliferation. Thus, our study suggests that LATS2 O-GlcNAcylation is deeply involved in Hippo pathway dysregulation in cancer cells.

The Hippo pathway controls organ size and tissue homeostasis by regulating cell proliferation and apoptosis. The LATS-mediated negative feedback loop prevents excessive activation of the effectors YAP/TAZ, maintaining homeostasis of the Hippo pathway. YAP and TAZ are hyperactivated in various cancer cells which lead to tumor growth. Aberrantly increased O-GlcNAcylation has recently emerged as a cause of hyperactivation of YAP in cancer cells. However, the mechanism, which induces hyperactivation of TAZ and blocks LATS-mediated negative feedback, remains to be elucidated in cancer cells. This study found that in breast cancer cells, abnormally increased O-GlcNAcylation hyperactivates YAP/TAZ and inhibits LATS2, a direct negative regulator of YAP/TAZ. LATS2 is one of the newly identified O-GlcNAcylated components in the MST-LATS kinase cascade. Here, we found that O-GlcNAcylation at LATS2 Thr436 interrupted its interaction with the MOB1 adaptor protein, which connects MST to LATS2, leading to activation of YAP/TAZ by suppressing LATS2 kinase activity. LATS2 is a core component in the LATS-mediated negative feedback loop. Thus, this study suggests that LATS2 O-GlcNAcylation is deeply involved in tumor growth by playing a critical role in dysregulation of the Hippo pathway in cancer cells.

Large tumor suppressor 2, LATS2, activates JNK in a kinase-independent mechanism through ASK1

Apoptosis signal-regulating kinase 1 (ASK1) is an important mediator of the cell stress response pathways. Because of its central role in regulating cell death, the activity of ASK1 is tightly regulated by protein-protein interactions and post-translational modifications. Deregulation of ASK1 activity has been linked to human diseases, such as neurological disorders and cancer. Here we describe the identification and characterization of large tumor suppressor 2 (LATS2) as a novel binding partner for ASK1. LATS2 is a core kinase in the Hippo signaling pathway and is commonly downregulated in cancer. We found that LATS2 interacts with ASK1 and increases ASK1-mediated signaling to promote apoptosis and activate the JNK mitogen-activated protein kinase (MAPK). This change in MAPK signaling is dependent on the catalytic activity of ASK1 but does not require LATS2 kinase activity. This work identifies a novel role for LATS2 as a positive regulator of the ASK1-MKK-JNK signaling pathway and establishes a kinase-independent function of LATS2 that may be part of the intricate regulatory system for cellular response to diverse stress signals.

Long noncoding RNA DDX11-AS1 epigenetically represses LATS2 by interacting with EZH2 and DNMT1 in hepatocellular carcinoma

Long noncoding RNAs (lncRNAs), a group of transcripts without protein coding potential, have been reported to play critical roles in progression of hepatocellular carcinoma (HCC). However, the biological role of DDX11-AS1 in HCC is not clear. In this study, we found that DDX11-AS1 expression was dramatically higher in HCC tissues and cell lines. Higher DDX11-AS1 expression predicted poor overall survival of patients. Functionally, the proliferation, cell cycle progression, migration, and invasion of HCC cells were inhibited by DDX11-AS1 silencing, while promoted by ectopic expression of DDX11-AS1. RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP) assays validated that DDX11-AS1 suppressed LATS2 expression by interacting with EZH2 and DNMT1 in HCC cells. Knockdown of DDX11-AS1 increased the mRNA and protein levels of LATS2. Overexpression of LATS2 abolished the promotive effect of DDX11-AS1 on cell growth and invasion. Besides, DDX11-AS1 promoted tumor formation in vivo. The mRNA levels of LATS2 were markedly decreased in tumor tissues and negatively correlated with DDX11-AS1 expression. Taken together, our data indicated that DDX11-AS1 may be a novel oncogene in hepatocarcinogenesis by repressing LATS2, providing a potential therapeutic target for HCC treatment.

The Hippo Pathway in Prostate Cancer

Despite recent efforts, prostate cancer (PCa) remains one of the most common cancers in men. Currently, there is no effective treatment for castration-resistant prostate cancer (CRPC). There is, therefore, an urgent need to identify new therapeutic targets. The Hippo pathway and its downstream effectors-the transcriptional co-activators, Yes-associated protein (YAP) and its paralog, transcriptional co-activator with PDZ-binding motif (TAZ)-are foremost regulators of stem cells and cancer biology. Defective Hippo pathway signaling and YAP/TAZ hyperactivation are common across various cancers. Here, we draw on insights learned from other types of cancers and review the latest advances linking the Hippo pathway and YAP/TAZ to PCa onset and progression. We examine the regulatory interaction between Hippo-YAP/TAZ and the androgen receptor (AR), as main regulators of PCa development, and how uncontrolled expression of YAP/TAZ drives castration resistance by inducing cellular stemness. Finally, we survey the potential therapeutic targeting of the Hippo pathway and YAP/TAZ to overcome PCa.

YAP and TAZ in Lung Cancer: Oncogenic Role and Clinical Targeting

Lung cancer is the leading cause of cancer death in the world and there is no current treatment able to efficiently treat the disease as the tumor is often diagnosed at an advanced stage. Moreover, cancer cells are often resistant or acquire resistance to the treatment. Further knowledge of the mechanisms driving lung tumorigenesis, aggressiveness, metastasization, and resistance to treatments could provide new tools for detecting the disease at an earlier stage and for a better response to therapy. In this scenario, Yes Associated Protein (YAP) and Trascriptional Coactivator with PDZ-binding motif (TAZ), the final effectors of the Hippo signaling transduction pathway, are emerging as promising therapeutic targets. Here, we will discuss the most recent advances made in YAP and TAZ biology in lung cancer and, more importantly, on the newly discovered mechanisms of YAP and TAZ inhibition in lung cancer as well as their clinical implications.

The pseudogene DUXAP10 promotes an aggressive phenotype through binding with LSD1 and repressing LATS2 and RRAD in non small cell lung cancer

Pseudogenes have been considered as non-functional transcriptional relics of human genomic for long time. However, recent studies revealed that they play a plethora of roles in diverse physiological and pathological processes, especially in cancer, and many pseudogenes are transcribed into long noncoding RNAs and emerging as a novel class of lncRNAs. However, the biological roles and underlying mechanism of pseudogenes in the pathogenesis of non small cell lung cancer are still incompletely elucidated. This study identifies a putative oncogenic pseudogene DUXAP10 in NSCLC, which is located in 14q11.2 and 2398 nt in length. Firstly, we found that DUXAP10 was significantly up-regulated in 93 human NSCLC tissues and cell lines, and increased DUXAP10 was associated with patients poorer prognosis and short survival time. Furthermore, the loss and gain of functional studies including growth curves, migration, invasion assays and in vivo studies verify the oncogenic roles of DUXAP10 in NSCLC. Finally, the mechanistic experiments indicate that DUXAP10 could interact with Histone demethylase Lysine specific demethylase1 (LSD1) and repress tumor suppressors Large tumor suppressor 2 (LATS2) and Ras-related associated with diabetes (RRAD) transcription in NSCLC cells. Taken together, these findings demonstrate DUXAP10 exerts the oncogenic roles through binding with LSD1 and epigenetic silencing LATS2 and RRAD expression. Our investigation reveals the novel roles of pseudogene in NSCLC, which may serve as new target for NSCLC diagnosis and therapy.

The LATS1 and LATS2 tumor suppressors: beyond the Hippo pathway

Proper cellular functionality and homeostasis are maintained by the convergent integration of various signaling cascades, which enable cells to respond to internal and external changes. The Dbf2-related kinases LATS1 and LATS2 (LATS) have emerged as central regulators of cell fate, by modulating the functions of numerous oncogenic or tumor suppressive effectors, including the canonical Hippo effectors YAP/TAZ, the Aurora mitotic kinase family, estrogen signaling and the tumor suppressive transcription factor p53. While the basic functions of the LATS kinase module are strongly conserved over evolution, the genomic duplication event leading to the emergence of two closely related kinases in higher organisms has increased the complexity of this signaling network. Here, we review the LATS1 and LATS2 intrinsic features as well as their reported cellular activities, emphasizing unique characteristics of each kinase. While differential activities between the two paralogous kinases have been reported, many converge to similar pathways and outcomes. Interestingly, the regulatory networks controlling the mRNA expression pattern of LATS1 and LATS2 differ strongly, and may contribute to the differences in protein binding partners of each kinase and in the subcellular locations in which each kinase exerts its functions.

The clinical significance and biological function of large tumour suppressor 2 in hepatocellular carcinoma

OBJECTIVES

Present evidence has suggested that large tumour suppressor 2 (LATS2) is abnormally expressed in most human cancer. However, the clinical and prognostic value in hepatocellular carcinoma (HCC) is still unknown.

MATERIALS AND METHODS

Large tumour suppressor 2 mRNA and protein expression levels in HCC tissues and cell lines were detected by qRT-PCR, immunohistochemistry or Western blot. The correlation between LATS2 expression and clinicopathological factors was analysed through immunohistochemistry. The function of LATS2 on HCC cell growth and mobility was explored through MTT, colony formation, Transwell migration and invasion assays. The molecular mechanism of LATS2 was screened and confirmed by qRT-PCR and Western blot.

RESULTS AND CONCLUSION

In this study, LATS2 mRNA and protein expressions were decreased in HCC tissues and cell lines compared with normal hepatic tissues and hepatic cell line. Low LATS2 expression was oppositely corrected with tumour stage, vascular invasion and metastasis. The univariate and multivariate analyses suggested that low LATS2 expression was an independent poor prognostic factor for HCC patients. The in vitro experiments showed that LATS2 regulated HCC cells migration and invasion, but had no effect on HCC cells proliferation. Meanwhile, LATS2 modulated metastasis-associated genes expression including E-cadherin, vimentin, snail, slug, MMP2 and MMP9. In conclusion, LATS2 is a prognostic biomarker and a tumour metastasis suppressor in HCC.

MCM7 and its hosted miR-25, 93 and 106b cluster elicit YAP/TAZ oncogenic activity in lung cancer

Lung cancer is the first cause of cancer death worldwide and the Hippo pathway transcriptional coactivators YAP/TAZ have a pro-oncogenic role in this context. In order to understand the mechanisms through which YAP/TAZ elicit their oncogenic role in different systems, many studies are focused on YAP/TAZ target genes involved in the regulation of cell proliferation/survival and migration. However, there is scarce evidence on the role of YAP/TAZ in microRNA regulation while there is increasing evidence supporting the role of microRNAs in the main oncogenic processes. Here, we showed that YAP/TAZ were able to regulate several microRNAs in non-small cell lung cancer (NSCLC) cell lines. In detail, we focused on a cluster of three oncogenic microRNAs (miR-25, 93 and 106b) hosted in the MCM7 gene that were overexpressed in lung tumors compared to normal tissues. In addition, similar behavior was observed in breast cancer and head and neck tumor casuistries, where they showed a prognostic role. In NSCLC cells, YAP/TAZ induced the transcription of the MCM7 gene and its hosted miRs, thereby promoting cell proliferation through the post-transcriptional inhibition of the p21 cell cycle regulator. Accordingly, p21 was maintained at low levels in lung tumors compared to normal tissues. Conversely, its expression was restored in NSCLC cells upon YAP/TAZ interference or upon treatment with the statin cerivastatin. In summary, we provide evidence for a novel mechanism of modulation supporting the protumorigenic functions of the YAP/TAZ factors through the modulation of a bioncogenic locus consisting of one gene and three hosted microRNAs.

Repression of MicroRNA-372 by Arsenic Sulphide Inhibits Prostate Cancer Cell Proliferation and Migration through Regulation of large tumour suppressor kinase 2

As the main component of realgar, arsenic sulphide (As₄ S₄ ) contains antitumour activity by repressing cancer cell proliferation and migration in many tumours. However, the detailed mechanism of these processes is not clear yet. MicroRNAs (miRNAs) can function as tumour suppressor or oncogene based on their target mRNAs in different tumour tissues. Here, we found that As₄ S₄ could repress the overexpression of microRNA-372 (miR-372) in two prostate cancer cell lines and its overexpression promoted cell proliferation and migration. Large tumour suppressor kinase 2 (LATS2) was confirmed as a direct target of miR-372 using luciferase assays in these two prostate cancer cell lines. Down-regulation of LATS2 could promote prostate cancer cell proliferation and migration just as overexpression of miR-372 did and overexpression of LATS2 could reverse this effect of miR-372. The antitumour activity of As₄ S₄ and the oncogenic function of miR-372 were further confirmed using a mouse xenograft model. Altogether, our data showed evidence that repressing the overexpression of miR-372 by As₄ S₄ could inhibit prostate cancer cell proliferation and migration by targeting LATS2. Therefore, miR-372 may be a possible biomarker for the prediction of prostate cancer and As₄ S₄ may have potential therapeutic function for prostate cancer.

MicroRNA-103 promotes tumor growth and metastasis in colorectal cancer by directly targeting LATS2

Colorectal cancer (CRC) has become the third most common cancer worldwide and leads to a high mortality rate. Although colorectal cancer has been studied widely, the underlying molecular mechanism remains unclear. Increasing evidence shows that the abnormal expression of microRNAs (miRNAs) is involved in tumorigenesis. Previous studies have reported that miRNA-103 (miR-103) is dysregulated in CRC; however, the expression, function and mechanism of miR-103 in CRC are not well known. The present study showed that miR-103 was overexpressed in the primary tumor tissues of patients with CRC and was significantly associated with a more aggressive phenotype of CRC in patients. Survival rate analysis demonstrated that CRC patients with high miR-103 expression had a poorer overall survival compared with CRC patients with low miR-103 expression. In CRC cell lines, miR-103 inhibition significantly decreased the proliferation, invasion and migration of the cells in vitro. Furthermore, miR-103 repressed large tumor suppressor kinase 2 (LATS2) expression by directly binding to the LATS2-3'-untranslated region, and an inverse correlation was identified between the expression of miR-103 and LATS2 messenger RNA in primary CRC tissues. In addition, the restoration of LATS2 led to suppressed proliferation, invasion and migration of CRC cells. In vivo, miR-103 promotes tumor growth in nude mice. In summary, miR-103 performs a critical role in the promotion of the invasive and metastatic capacities of CRC, possibly by directly targeting LATS2. This miRNA may be involved in the development and progression of CRC.

LATS2 as a poor prognostic marker regulates non-small cell lung cancer invasion by modulating MMPs expression

Large tumor suppressor 2 (LATS2) plays significant roles in tumorigenesis and cancer progression. This study was aimed to analyze the correlation between LATS2 expression and clinicopathologic features and its prognostic significance in non-small cell lung cancer (NSCLC). LATS2 expression was examined in 73 NSCLC clinical specimens and 22 normal lung tissues using immunohistochemistry. Low levels of LATS2 protein were inversely associated with the T classification (P=0.001), N classification (P=0.005) and clinical stage (P=0.001) in NSCLC patients. Patients with lower LATS2 expression had a significantly shorter overall survival than patients with high LATS2 expression. Multivariate analysis suggested that low expression of LATS2 was an independent prognostic indicator (P=0.002) for the survival of patients with NSCLC. Furthermore, overexpression of LATS2 resulted in mobility inhibition in NSCLC cell lines A549 and H1299, and reduced protein level of matrix metalloproteinase-2 (MMP-2) and MMP-9. On the contrary, LATS2 siRNA treatment enhanced cell mobility and increased MMP-2 and MMP-9 protein expression level. In conclusion, low expression of LATS2 is a potential unfavorable prognostic factor and promoted cell invasion and migration in NSCLC.

In utero exposure to second-hand smoke activates pro-asthmatic and oncogenic miRNAs in adult asthmatic mice

Exposures to environmental pollutants contribute to dysregulated microRNA (miRNA) expression profiles, which have been implicated in various diseases. Previously, we reported aggravated asthmatic responses in ovalbumin (OVA)-challenged adult mice that had been exposed in utero to second-hand smoke (SHS). Whether in utero SHS exposure dysregulates miRNA expression patterns in the adult asthma model has not been investigated. Pregnant BALB/c mice were exposed (days 6-19 of pregnancy) to SHS (10 mg/m(3)) or HEPA-filtered air. All offspring were sensitized and challenged with OVA (19-23 weeks) before sacrifice. RNA samples extracted from lung homogenates, were subjected to RNA sequencing (RNA-seq). RNA-seq identified nine miRNAs that were most significantly up-regulated by in utero SHS exposure. Among these nine, miR-155-5p, miR-21-3p, and miR-18a-5p were also highly correlated with pro-asthmatic Th2 cytokine levels in bronchoalveolar lavage fluid. Further analysis indicated that these up-regulated miRNAs shared common chromosome locations, particularly Chr 11C, with pro-asthmatic genes. These three miRNAs have also been characterized as oncogenic miRNAs (oncomirs). We cross-referenced miRNA-mRNA expression profiles and identified 16 tumor suppressor genes that were down-regulated in the in utero-exposed offspring and that are predicted targets of the up-regulated oncomirs. In conclusion, in utero SHS exposure activates pro-asthmatic genes and miRNAs, which colocalize at specific chromosome locations, in OVA-challenged adult mice. The oncogenic characteristics of the miRNAs and putative miRNA-mRNA regulatory networks suggest that the synergistic effect of in utero SHS exposure and certain adult irritants may promote an oncogenic milieu in mouse lungs via inhibition of miRNA-regulated tumor suppressor genes.

Long Noncoding RNA PVT1 Promotes Non-Small Cell Lung Cancer Cell Proliferation through Epigenetically Regulating LATS2 Expression

Long noncoding RNAs (lncRNA) are a novel class of transcripts with no protein coding capacity, but with diverse functions in cancer cell proliferation, apoptosis, and metastasis. The lncRNA PVT1 is 1,716 nt in length and located in the chr8q24.21 region, which also contains the myelocytomatosis (MYC) oncogene. Previous studies demonstrated that MYC promotes PVT1 expression in primary human cancers. However, the expression pattern and potential biologic function of PVT1 in non-small cell lung cancer (NSCLC) is still unclear. Here, we found that PVT1 was upregulated in 105 human NSCLC tissues compared with normal samples. High expression of PVT1 was associated with a higher tumor-node-metastasis stage and tumor size, as well as poorer overall survival. Functional analysis revealed that knockdown of PVT1 inhibited NSCLC cell proliferation and induced apoptosis both in vitro and in vivo RNA immunoprecipitation and chromatin immunoprecipitation assays demonstrated that PVT1 recruits EZH2 to the large tumor suppressor kinase 2 (LATS2) promoter and represses LATS2 transcription. Furthermore, ectopic expression of LATS2 increased apoptosis and repressed lung adenocarcinoma cell proliferation by regulating the Mdm2-p53 pathway. Taken together, our findings indicated that PVT1/EZH2/LATS2 interactions might serve as new target for lung adenocarcinoma diagnosis and therapy. Mol Cancer Ther; 15(5); 1082-94. ©2016 AACR.

Roles of the Hippo pathway in lung development and tumorigenesis

Lung cancer is the most commonly diagnosed cancer and accounts for one fifth of all cancer deaths worldwide. Although significant progress has been made toward our understanding of the causes of lung cancer, the 5-year survival is still lower than 15%. Therefore, there is an urgent need for novel lung cancer biomarkers and drug targets. The Hippo signaling pathway is an emerging signaling pathway that regulates various biological processes. Recently, increasing evidence suggests that the Hippo pathway may play important roles in not only lung development but also lung tumorigenesis. In this review article, we will summarize the most recent advances and predict future directions on this new cancer research field.

Identification of module biomarkers from the dysregulated ceRNA–ceRNA interaction network in lung adenocarcinoma

The dysregulated ceRNA–ceRNA interaction network in lung adenocarcinoma.

A de novo 2.9 Mb interstitial deletion at 13q12.11 in a child with developmental delay accompanied by mild dysmorphic characteristics

Background

Proximal deletions in the 13q12.11 region are very rare. Much larger deletions including this region have been described and are associated with complex phenotypes of mental retardation, developmental delay and various others anomalies.

Results

We report on a 3-year-old girl with a rare 2.9 Mb interstitial deletion at 13q12.11 due to a de novo unbalanced t(13;14) translocation. She had mild mental retardation and relatively mild dysmorphic features such as microcephaly, flat nasal bridge, moderate micrognathia and clinodactyly of 5^th finger. Molecular karyotyping revealed a deletion on the long arm of chromosome 13 as involving sub-bands 13q12.11, a deletion of about 2.9 Mb.

Discussion

The clinical application of array-CGH has made it possible to detect submicroscopical genomic rearrangements that are associated with varying phenotypes.The description of more patients with deletions of the 13q12.11 region will allow a more precise genotype-phenotype correlation.

Aberrant large tumor suppressor 2 (LATS2) gene expression correlates with EGFR mutation and survival in lung adenocarcinomas

BACKGROUND

Large tumor suppressor 2 (LATS2) gene is a putative tumor suppressor gene with potential roles in regulation of cell proliferation and apoptosis in lung cancer. The aim of this study is to explore the association of aberrant LATS2 expression with EGFR mutation and survival in lung adenocarcinoma (AD), and the effects of LATS2 silencing in both lung AD cell lines.

METHODS

LATS2 mRNA and protein expression in resected lung AD were correlated with demographic characteristics, EGFR mutation and survival. LATS2-specific siRNA was transfected into four EGFR wild-type (WT) and three EGFR mutant AD cell lines and the changes in LATS2 expression and relevant signaling molecules before and after LATS2 knockdown were assayed.

RESULTS

Fifty resected lung AD were included (M:F=23:27, smokers:non-smokers=19:31, EGFR mutant:wild-type=21:29) with LATS2 mRNA levels showed no significant difference between gender, age, smoking and pathological stages while LATS2 immunohistochemical staining on an independent set of 79 lung AD showed similar trend. LATS2 mRNA level was found to be a significant independent predictor for survival status (disease-free survival RR=0.217; p=0.003; Overall survival RR=0.238; p=0.036). siRNA-mediated suppression of LATS2 expression resulted in augmentation of ERK phosphorylation in EGFR wild-type AD cell lines with high basal LATS2 expression, discriminatory modulation of Akt signaling between EGFR wild-type and mutant cells, and induction of p53 accumulation in AD cell lines with low baseline p53 levels.

CONCLUSIONS

LATS2 expression level is predictive of survival in patients with resected lung AD. LATS2 may modulate and contribute to tumor growth via different signaling pathways in EGFR mutant and wild-type tumors.

The expression analysis of LATS2 gene in de novo AML patients

Acute myeloid leukemia is a heterogeneous disease with respect to presentation and clinical outcome. Acquired genetic alterations along with epigenetic changes in hematopoietic progenitor cells are associated with the disease development. LATS2, as a tumor suppressor, has been indicated to have expression variations in different cancers. The aim of the present study was to analyze the expression level of the LATS2 gene in acute myeloid leukemia (AML) patients. Using quantitative real-time PCR, the expression level of the LATS2 gene was detected in peripheral blood samples from 32 patients with de novo AML and 10 normal controls. LATS2 gene was significantly over-expressed in AML patients compared to normal subjects. Significant LATS2 over-expression was observed in all FAB types except for the M3 (p = 0.661). The present work provides the first evidence of the over-expression of LATS2 in AML patients and suggests that the gene might play a role in the disease development and hence may be a potential therapeutic target for AML treatment.

Expression of LATS1 contributes to good prognosis and can negatively regulate YAP oncoprotein in non-small-cell lung cancer

Large tumor suppressor (LATS) is a Ser/Thr kinase originally isolated from Drosophila. Recent studies demonstrate that LATS is an important member of the Hippo pathway which can regulate organ size and cell proliferation. However, little is known about the expression and clinical significance of LATS in lung cancer. In this study, we aimed to assess the clinical significance and biological functions of LATS1 in non-small-cell lung cancer (NSCLC). We investigated the expression of LATS1 in 136 cases of NSCLC tissue and 30 cases of normal lung tissue by immunohistochemical staining. The results confirmed that LATS1 expression was higher in normal lung tissues, but significantly lower in NSCLC tissues. Moreover, the expression of LATS1 in NSCLC was significantly correlated with p-TNM stage (p = 0.038) and lymph node metastasis (p = 0.014). Importantly, the loss of LATS1 expression was associated with short overall survival. Further study in NSCLC cell lines in which LATS1 was either overexpressed or depleted confirmed that LATS1 markedly inhibited cell proliferation and invasion and could regulate the nuclear location of yes-associated protein (YAP). These results indicate that LATS1 may play an important role in NSCLC, and may serve as a novel therapeutic target of NSCLC.

The Hippo pathway regulates stem cell proliferation, self-renewal, and differentiation

Stem cells and progenitor cells are the cells of origin for multi-cellular organisms and organs. They play key roles during development and their dysregulation gives rise to human diseases such as cancer. The recent development of induced pluripotent stem cell (iPSC) technology which converts somatic cells to stem-like cells holds great promise for regenerative medicine. Nevertheless, the understanding of proliferation, differentiation, and self-renewal of stem cells and organ-specific progenitor cells is far from clear. Recently, the Hippo pathway was demonstrated to play important roles in these processes. The Hippo pathway is a newly established signaling pathway with critical functions in limiting organ size and suppressing tumorigenesis. This pathway was first found to inhibit cell proliferation and promote apoptosis, therefore regulating cell number and organ size in both Drosophila and mammals. However, in several organs, disturbance of the pathway leads to specific expansion of the progenitor cell compartment and manipulation of the pathway in embryonic stem cells strongly affects their self-renewal and differentiation. In this review, we summarize current observations on roles of the Hippo pathway in different types of stem cells and discuss how these findings changed our view on the Hippo pathway in organ development and tumorigenesis.

A kinase shRNA screen links LATS2 and the pRB tumor suppressor

pRB-mediated inhibition of cell proliferation is a complex process that depends on the action of many proteins. However, little is known about the specific pathways that cooperate with the Retinoblastoma protein (pRB) and the variables that influence pRB's ability to arrest tumor cells. Here we describe two shRNA screens that identify kinases that are important for pRB to suppress cell proliferation and pRB-mediated induction of senescence markers. The results reveal an unexpected effect of LATS2, a component of the Hippo pathway, on pRB-induced phenotypes. Partial knockdown of LATS2 strongly suppresses some pRB-induced senescence markers. Further analysis shows that LATS2 cooperates with pRB to promote the silencing of E2F target genes, and that reduced levels of LATS2 lead to defects in the assembly of DREAM (DP, RB [retinoblastoma], E2F, and MuvB) repressor complexes at E2F-regulated promoters. Kinase assays show that LATS2 can phosphorylate DYRK1A, and that it enhances the ability of DYRK1A to phosphorylate the DREAM subunit LIN52. Intriguingly, the LATS2 locus is physically linked with RB1 on 13q, and this region frequently displays loss of heterozygosity in human cancers. Our results reveal a functional connection between the pRB and Hippo tumor suppressor pathways, and suggest that low levels of LATS2 may undermine the ability of pRB to induce a permanent cell cycle arrest in tumor cells.

The Lats2 tumor suppressor augments p53-mediated apoptosis by promoting the nuclear proapoptotic function of ASPP1

Apoptosis is an important mechanism to eliminate potentially tumorigenic cells. The tumor suppressor p53 plays a pivotal role in this process. Many tumors harbor mutant p53, but others evade its tumor-suppressive effects by altering the expression of proteins that regulate the p53 pathway. ASPP1 (apoptosis-stimulating protein of p53-1) is a key mediator of the nuclear p53 apoptotic response. Under basal conditions, ASPP1 is cytoplasmic. We report that, in response to oncogenic stress, the tumor suppressor Lats2 (large tumor suppressor 2) phosphorylates ASPP1 and drives its translocation into the nucleus. Together, Lats2 and ASPP1 shunt p53 to proapoptotic promoters and promote the death of polyploid cells. These effects are overridden by the Yap1 (Yes-associated protein 1) oncoprotein, which disrupts Lats2-ASPP1 binding and antagonizes the tumor-suppressing function of the Lats2/ASPP1/p53 axis.

TAZ is a novel oncogene in non-small cell lung cancer

Transcriptional coactivator with PDZ-binding motif (TAZ) is a transcriptional coactivator involved in the differentiation of stem cell as well as the development of multiple organs. Recently, TAZ has also been identified as a major component of the novel Hippo-LATS tumor suppressor pathway and to function as an oncogene in breast cancer. We show for the first time that TAZ is an oncogene in non-small cell lung cancer (NSCLC). Our results show that TAZ is overexpressed in NSCLC cells and that lentivirus-mediated overexpression of TAZ in HBE135 immortalized human bronchial epithelial cells causes increased cell proliferation and transformation, which can be restored back to its original levels by knockdown of TAZ. In addition, short-hairpin RNA (shRNA)-mediated knockdown of TAZ expression in NSCLC cells suppresses their proliferation and anchorage-independent growth in vitro, and tumor growth in mice in vivo, which can be reversed by re-introduction of shRNA-resistant TAZ into TAZ-knockdown NSCLC cells. These results indicate that TAZ is an oncogene and has an important role in tumorigenicity of NSCLC cells. Therefore, TAZ may present a novel target for the future diagnosis, prognosis and therapy of lung cancer.

LATS2 is a tumor suppressor gene of malignant mesothelioma

Malignant mesothelioma (MM) is an aggressive neoplasm associated with asbestos exposure. We carried out genome-wide array-based comparative genomic hybridization analysis with 14 MM cell lines. Three cell lines showed overlapping homozygous deletion at chromosome 13q12, which harbored the LATS2 (large tumor suppressor homolog 2) gene. With 6 other MM cell lines and 25 MM tumors, we found 10 inactivating homozygous deletions or mutations of LATS2 among 45 MMs. LATS2 encodes a serine/threonine kinase, a component of the Hippo tumor-suppressive signaling pathway, and we transduced LATS2 in MM cells with its mutation. Transduction of LATS2 inactivated oncoprotein YAP, a transcriptional coactivator, via phosphorylation, and inhibited MM cell growth. We also analyzed LATS2 immunohistochemically and found that 13 of 45 MM tumors had low expression of LATS2. Because NF2 is genetically mutated in 40% to 50% of MM, our data indicate that Hippo pathway dysregulation is frequent in MM cells with inactivation of LATS2 or an upstream regulator of this pathway, Merlin, which is encoded by NF2. Thus, our results suggest that the inactivation of LATS2 is one of the key mechanisms for constitutive activation of YAP, which induces deregulation of MM cell proliferation.

hNaa10p contributes to tumorigenesis by facilitating DNMT1-mediated tumor suppressor gene silencing

Hypermethylation-mediated tumor suppressor gene silencing plays a crucial role in tumorigenesis. Understanding its underlying mechanism is essential for cancer treatment. Previous studies on human N-alpha-acetyltransferase 10, NatA catalytic subunit (hNaa10p; also known as human arrest-defective 1 [hARD1]), have generated conflicting results with regard to its role in tumorigenesis. Here we provide multiple lines of evidence indicating that it is oncogenic. We have shown that hNaa10p overexpression correlated with poor survival of human lung cancer patients. In vitro, enforced expression of hNaa10p was sufficient to cause cellular transformation, and siRNA-mediated depletion of hNaa10p impaired cancer cell proliferation in colony assays and xenograft studies. The oncogenic potential of hNaa10p depended on its interaction with DNA methyltransferase 1 (DNMT1). Mechanistically, hNaa10p positively regulated DNMT1 enzymatic activity by facilitating its binding to DNA in vitro and its recruitment to promoters of tumor suppressor genes, such as E-cadherin, in vivo. Consistent with this, interaction between hNaa10p and DNMT1 was required for E-cadherin silencing through promoter CpG methylation, and E-cadherin repression contributed to the oncogenic effects of hNaa10p. Together, our data not only establish hNaa10p as an oncoprotein, but also reveal that it contributes to oncogenesis through modulation of DNMT1 function.

Molecular characterization of human homologs of yeast MOB1

MOB (Mps one binder) was originally identified in yeast as a regulator of mitotic exit and cytokinesis, and was later identified as a tumor suppressor and a component of an emerging Hippo-LATS tumor suppressor pathway in Drosophila (D). So far, 7 human homologs of yeast MOB (hMOB1A, 1B, 2A, 2B, 2C, 3, 4) have been identified. Although hMOB1A/B has been extensively studied, the biological features of other hMOBs are largely unknown. In addition, while hMOB1 has been reported to interact with and activate LATS (Large tumor suppressor)/Warts tumor suppressor, the functional significance of this is unknown. In this study, we have characterized, for the first time, the cellular and biochemical function of all human MOBs. By examining hMOB mRNAs expression in various human tissues, we found that hMOBs demonstrated different expression patterns. Further biochemical characterization of hMOBs showed that only hMOB1A and hMOB1B interact with both LATS1 and LATS2 in vitro and in vivo. Significantly, we have discovered that overexpression of hMOB1 in human cancer cells activated LATS activity and inhibited cell proliferation or caused apoptosis while hMOB1, targeting the plasma membrane, led to a more significant phenotype. Reciprocally, short-hairpin (sh) RNA-mediated suppression of hMOB1 causes increased cell proliferation. Our findings provided evidence that hMOB1A and hMOB1B are 2 LATS-binding proteins that may function as tumor suppressors in human cancer cells.

Hypermethylation of the large tumor suppressor genes in Japanese lung cancer

Large tumor suppressor (LATS) 1 and 2 are tumor suppressor genes implicated in the regulation of the cell cycle. The methylation statuses of the promoter regions of these genes were studied in Japanese lung cancers. The methylation statuses of the promoter regions of LATS1 and LATS2 were investigated by methylation-specific PCR. The findings were compared to clinicopathological features of lung cancer. Methylation-specific PCR showed that the LATS1 promoter region was hypermethylated in 95 out of 119 (79.8%) lung cancers. The methylation status of LATS1 was significantly associated with squamous histology (p=0.0267) and smoking status (never smoker vs. smoker; p=0.0399). LATS1-ummethylated patients harbored more EGFR mutations (p=0.0143). The LATS2 promoter region was hypermethylated in 160 out of 203 (78.8%) lung cancers. However, the methylation status had no association with the clinicopathological characteristics of the lung cancers cases. Both the LATS1 and LATS2 methylation statuses did not correlate with survival of lung cancer patients. Thus, the EGFR methylation status of the LATS genes has limited value in Japanese lung cancers.

Genomic abnormalities and signal transduction dysregulation in malignant mesothelioma cells

Malignant mesothelioma (MM) is a tumor with poor prognosis associated with asbestos exposure. While it remains to be clarified how asbestos fibers confer genetic/epigenetic alterations and induce cellular transformation in normal mesothelial cells, the understanding of key molecular mechanisms of MM cell development, proliferation, and invasion has progressed. MM shows frequent genetic inactivation of tumor suppressor genes of p16(INK4a)/p14(ARF) and neurofibromatosis type 2 (NF2) which encodes Merlin, and epigenetic inactivation of RASSF1A. However, no frequent mutations of well-known oncogenes such as K-RAS and PIK3CA have been identified. Activation of multiple receptor tyrosine kinases including the epidermal growth factor receptor (EGFR) family and MET, and subsequent deregulations of mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K)-AKT signaling cascades are frequently observed in most MM cells. The tumor suppressive function of Merlin in MM cells is also being investigated by dissecting its possible downstream signaling cascade called the Hippo pathway. Further comprehensive delineation of dysregulated signaling cascades in MM cells will lead to identification of key addiction pathways for cell survival and proliferation of MM cells, which strongly promote establishment of a new molecular target therapy for MM.

Silencing of the Lats2 tumor suppressor overrides a p53-dependent oncogenic stress checkpoint and enables mutant H-Ras-driven cell transformation

The Lats2 tumor suppressor protein has previously been implicated in promoting p53 activation in response to mitotic apparatus stress, by preventing Mdm2-driven p53 degradation. We now report that Lats2 also plays a role in an ATR-Chk1-mediated stress checkpoint in response to oncogenic H-Ras. Activated mutant H-Ras triggers the translocation of Lats2 from centrosomes into the nucleus, coupled with an increase in Lats2 protein levels. This leads to induction of p53 activity, upregulation of proapoptotic genes, downregulation of antiapoptotic genes and eventually apoptotic cell death. Many of the cells that survive apoptosis undergo senescence. However, a fraction of the cells escape this checkpoint mechanism, despite maintaining high mutant H-Ras expression. These escapers display increased genome instability, as evidenced by a substantial fraction of cells with micronuclei and cells with polyploid genomes. Interestingly, such cells exhibit markedly reduced levels of Lats2, in conjunction with enhanced hypermethylation of the Lats2 gene promoter. Our findings suggest that Lats2 might play an important role in quenching H-Ras-induced transformation, while silencing of Lats2 expression might serve as a mechanism to enable tumor progression.

Identification of LATS transcriptional targets in HeLa cells using whole human genome oligonucleotide microarray

Human LATS1 and LATS2) (LATS1/2) are tumor suppressors that have been shown to be mutated or downregulated in several human cancers including leukemia, lung, prostate and breast cancers. However, the precise mechanisms and the proteins modulated by LATS1/2 that are responsible for these events remain largely unknown. To elucidate potential signaling pathways, the current study investigated the expression profile in HeLa cells with reduced expression of LATS1/2. Using RNA-mediated interference, both LATS1 and LATS2 were substantially knocked-down, and accordingly, this lead to an increase in multiple phenotypes associated with tumor progression, including enhanced cell proliferation, resistance to drug-induced cell death, and increased cell migration. Using whole human genome Oligo (60-mer) arrays (Agilent), genes modulated by loss of LATS1/2 were identified and functionally grouped into categories including cell proliferation, cell death, cell adhesion and motility, as well as cell communication. Selected genes, including known tumor suppressor genes and oncogenes such as CDKN1A, WISP2, SLIT2, TP53INP1, BIRC4BP, SPRY2, SPRY4, SPRED1, FAT4, and CYR61 were confirmed by qRT-PCR to be significantly differentially expressed. Importantly, the collection of genes identified suggests that LATS1/2 function through diverse mechanisms and multiple signaling pathways including the Hippo signaling pathway, as well as the p53, Ras-ERK, or WNT networks, to inhibit tumor progression.