Structural analysis of the cancer-specific promoter in mesothelin and in other genes overexpressed in cancers

Overexpression of UBE2E2 in Mouse Pancreatic β-Cells Leads to Glucose Intolerance via Reduction of β-Cell Mass

Genome-wide association studies have identified several gene polymorphisms, including UBE2E2, associated with type 2 diabetes. Although UBE2E2 is one of the ubiquitin-conjugating enzymes involved in the process of ubiquitin modifications, the pathophysiological roles of UBE2E2 in metabolic dysfunction are not yet understood. Here, we showed upregulated UBE2E2 expression in the islets of a mouse model of diet-induced obesity. The diabetes risk allele of UBE2E2 (rs13094957) in noncoding regions was associated with upregulation of UBE2E2 mRNA in the human pancreas. Although glucose-stimulated insulin secretion was intact in the isolated islets, pancreatic β-cell-specific UBE2E2-transgenic (TG) mice exhibited reduced insulin secretion and decreased β-cell mass. In TG mice, suppressed proliferation of β-cells before the weaning period and while receiving a high-fat diet was accompanied by elevated gene expression levels of p21, resulting in decreased postnatal β-cell mass expansion and compensatory β-cell hyperplasia, respectively. In TG islets, proteomic analysis identified enhanced formation of various types of polyubiquitin chains, accompanied by increased expression of Nedd4 E3 ubiquitin protein ligase. Ubiquitination assays showed that UBE2E2 mediated the elongation of ubiquitin chains by Nedd4. The data suggest that UBE2E2-mediated ubiquitin modifications in β-cells play an important role in regulating glucose homeostasis and β-cell mass.

Multi-Functional Regulation by YAP/TAZ Signaling Networks in Tumor Progression and Metastasis

The Hippo pathway transcriptional co-activators, YES-associated protein (YAP) and Transcriptional Co-Activator with PDZ Binding Motif (TAZ), have both been linked to tumor progression and metastasis. These two proteins possess overlapping and distinct functions, and their activities lead to the expression of genes involved in multiple cellular processes, including cell proliferation, survival, and migration. The dysregulation of YAP/TAZ-dependent cellular processes can result in altered tumor growth and metastasis. In addition to their well-documented roles in the regulation of cancer cell growth, survival, migration, and invasion, the YAP/TAZ-dependent signaling pathways have been more recently implicated in cellular processes that promote metastasis and therapy resistance in several solid tumor types. This review highlights the role of YAP/TAZ signaling networks in the regulation of tumor cell plasticity mediated by hybrid and reversible epithelial-mesenchymal transition (EMT) states, and the promotion of cancer stem cell/progenitor phenotypes. Mechanistically, YAP and TAZ regulate these cellular processes by targeting transcriptional networks. In this review, we detail recently uncovered mechanisms whereby YAP and TAZ mediate tumor growth, metastasis, and therapy resistance, and discuss new therapeutic strategies to target YAP/TAZ function in various solid tumor types. Understanding the distinct and overlapping roles of YAP and TAZ in multiple cellular processes that promote tumor progression to metastasis is expected to enable the identification of effective therapies to treat solid tumors through the hyper-activation of YAP and TAZ.

Exploring the Expression of the «Dark Matter» of the Genome in Mesothelioma for Potentially Predictive Biomarkers for Prognosis and Immunotherapy

Recent high-throughput RNA sequencing technologies have confirmed that a large part of the non-coding genome is transcribed. The priority for further investigations is nevertheless generally given in cancer to coding sequences, due to the obvious interest of finding therapeutic targets. In addition, several RNA-sequencing pipelines eliminate repetitive sequences, which are difficult to analyze. In this review, we shall focus on endogenous retroviruses. These sequences are remnants of ancestral germline infections by exogenous retroviruses. These sequences represent 8% of human genome, meaning four-fold the fraction of the genome encoding for proteins. These sequences are generally mostly repressed in normal adult tissues, but pathological conditions lead to their de-repression. Specific mesothelioma-associated endogenous retrovirus expression and their association to clinical outcome is discussed.

Therapeutic effiacy of T cells expressing chimeric antigen receptor derived from a mesothelin-specific scFv in orthotopic human pancreatic cancer animal models

Novel CAR T cells targeting mesothelin (MSLN) expressed on pancreatic cancer cells were developed to overcome the limit of the clinical efficacy of CAR T cell therapy for pancreatic cancer patients. Optimal single-chain variable fragments (scFv) binding to MSLN were selected based on the binding activity and the functional effectiveness of various scFv containing CAR-expressing T cells. Engineered MSLN CAR T cells showed successful anti-tumor activity specific to MSLN expression level. Furthermore, MSLN CAR T cells were evaluated for the anti-cancer efficacy in orthotopic mouse models bearing pancreatic cancer cells, MIA Paca-2, MSLN-overexpressed MIA Paca-2 or endogenously MSLN-expressing AsPC-1. Mice were randomized into control, mock treated, MS501 BBz treated, MS501 28z treated or MS501 28BBz treated group. Mice were monitored by weekly IVIS imaging and tumors were harvested and analyzed by immunohistochemical analyses. MSLN CAR T cells produced the therapeutic effect in orthotopic animal models with complete remission in significant number of mice. Histopathological analysis indicated that CD4+ and CD8+ MSLN CAR T cells infiltrated pancreatic tumor tissue and led to cancer cell eradication. Our results demonstrated the anti-tumor efficacy of MSLN CAR T cell therapy against pancreatic cancer, suggesting its therapeutic potential.

A review: hippo signaling pathway promotes tumor invasion and metastasis by regulating target gene expression

BACKGROUND

The Hippo pathway is widely considered to inhibit cell growth and play an important role in regulating the size of organs. However, recent studies have shown that abnormal regulation of the Hippo pathway can also affect tumor invasion and metastasis. Therefore, finding out how the Hippo pathway promotes tumor development by regulating the expression of target genes provides new ideas for future research on targeted drugs that inhibit tumor progression.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were systematically searched.

RESULTS

The search strategy identified 1892 hits and 196 publications were finally included in this review. As the core molecule of the Hippo pathway, YAP/TAZ are usually highly expressed in tumors that undergo invasion and migration and are accompanied by abnormally strong nuclear metastasis. Through its interaction with nuclear transcription factors TEADs, it directly or indirectly regulates and the expressions of target genes related to tumor metastasis and invasion. These target genes can induce the formation of invasive pseudopodia in tumor cells, reduce intercellular adhesion, degrade extracellular matrix (ECM), and cause epithelial-mesenchymal transition (EMT), or indirectly promote through other signaling pathways, such as mitogen-activated protein kinases (MAPK), TGF/Smad, etc, which facilitate the invasion and metastasis of tumors.

CONCLUSION

This article mainly introduces the research progress of YAP/TAZ which are the core molecules of the Hippo pathway regulating related target genes to promote tumor invasion and metastasis. Focus on the target genes that affect tumor invasion and metastasis, providing the possibility for the selection of clinical drug treatment targets, to provide some help for a more in-depth study of tumor invasion and migration mechanism and the development of clinical drugs.

Free CA125 promotes ovarian cancer cell migration and tumor metastasis by binding Mesothelin to reduce DKK1 expression and activate the SGK3/FOXO3 pathway

Objective: CA125/MUC16 is an O-glycosylated protein that is expressed on the surfaces of ovarian epithelial cells. This molecule is a widely used tumor-associated marker for diagnosis of ovarian cancer. Recently, CA125 was shown to be involved in ovarian cancer metastasis. The purpose of this study was to investigate the mechanism of CA125 during ovarian cancer metastasis.

Methods: We analyzed the Oncomine and CSIOVDB databases to determine the expression levels of DKK1 in ovarian cancer. DKK1 expression levels were upregulated or downregulated and applied with CA125 to Transwell and Western blot assays to ascertain the underlying mechanism by which CA125 stimulates cell migration via the SGK3/FOXO3 pathway. Anti-mesothelin antibodies (anti-MSLN) were used to block CA125 stimulation. Then the expression levels of DKK1were tested by enzyme-linked immunosorbent assay (ELISA) to eliminate the blocking effect of anti-MSLN to CA125 stimulation. Xenograft mouse models were used to detect the effects of CA125 and anti-MSLN on ovarian cancer metastasis in vivo.

Results: DKK1 levels were downregulated in ovarian tumor tissues according to the analyses of two databases and significantly correlated with FIGO stage, grade and disease-free survival in ovarian cancer patients. DKK1 levels were downregulated by CA125 stimulation in vitro. Overexpression of DKK1 reversed the ability of exogenous CA125 to mediate cell migration by activating the SGK3/FOXO3 signaling pathway. Anti-MSLN abrogated the DKK1 reduction and increased the apoptosis of ovarian cancer cells. The use of anti-MSLN in xenograft mouse models significantly reduced tumor growth and metastasis accelerated by CA125.

Conclusions: These experiments revealed that the SGK3/FOXO3 pathway was activated, wherein decreased expression of DKK1 was caused by CA125, which fuels ovarian cancer cell migration. Mesothelin is a potential therapeutic target for the treatment of ovarian cancer metastasis.

From Malignant Progression to Therapeutic Targeting: Current Insights of Mesothelin in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), accounting for 90% of all pancreatic tumors, is a highly devastating disease with poor prognosis and rising incidence. The lack of available specific diagnostics tests and the limited treatment opportunities contribute to this pejorative issue. Over the last 10 years, a growing interest pointing towards mesothelin (MSLN) as a promising PDAC-associated antigen has emerged. The limited expression of MSLN in normal tissues (peritoneum, pleura and pericardium) and its overexpression in 80 to 90% of PDAC make it an attractive candidate for therapeutic management of PDAC patients. Moreover, its role in malignant progression related to its involvement in tumor cell proliferation and resistance to chemotherapy has highlighted the relevance of its targeting. Hence, several clinical trials are investigating anti-MSLN efficacy in PDAC. In this review, we provide a general overview of the different roles sustained by MSLN during PDAC progression. Finally, we also summarize the different MSLN-targeted therapies that are currently tested in the clinic.

YAP1 is an independent prognostic marker in pancreatic cancer and associated with extracellular matrix remodeling

Background

Pancreatic cancer is a major cause of cancer-related mortality. The identification of effective biomarkers is essential in order to improve management of the disease. Yes-associated protein 1 (YAP1) is a downstream effector of the Hippo pathway, a signal transduction system implicated in tissue repair and regeneration, as well as tumorigenesis. Here we evaluate the biomarker potential of YAP1 in pancreatic cancer tissue.

Methods

YAP1 was selected as a possible biomarker for pancreatic cancer from global protein sequencing of fresh frozen pancreatic cancer tissue samples and normal pancreas controls. The prognostic utility of YAP1 was evaluated using mRNA expression data from 176 pancreatic cancer patients in The Cancer Genome Atlas (TCGA), as well as protein expression data from immunohistochemistry analysis of a local tissue microarray (TMA) cohort comprising 140 pancreatic cancer patients. Ingenuity Pathway Analysis was applied to outline the interaction network for YAP1 in connection to the pancreatic tumor microenvironment. The expression of YAP1 target gene products was evaluated after treatment of the pancreatic cancer cell line Panc-1 with three substances interrupting YAP–TEAD interaction, including Super-TDU, Verteporfin and CA3.

Results

Mass spectrometry based proteomics showed that YAP1 is the top upregulated protein in pancreatic cancer tissue when compared to normal controls (log2 fold change 6.4; p = 5E−06). Prognostic analysis of YAP1 demonstrated a significant correlation between mRNA expression level data and reduced overall survival (p = 0.001). In addition, TMA and immunohistochemistry analysis suggested that YAP1 protein expression is an independent predictor of poor overall survival [hazard ratio (HR) 1.870, 95% confidence interval (CI) 1.224–2.855, p = 0.004], as well as reduced disease-free survival (HR 1.950, 95% CI 1.299–2.927, p = 0.001). Bioinformatic analyses coupled with in vitro assays indicated that YAP1 is involved in the transcriptional control of target genes, associated with extracellular matrix remodeling, which could be modified by selected substances disrupting the YAP1-TEAD interaction.

Conclusions

Our findings indicate that YAP1 is an important prognostic biomarker for pancreatic cancer and may play a regulatory role in the remodeling of the extracellular matrix.

The Role of Mesothelin as a Diagnostic and Therapeutic Target in Pancreatic Ductal Adenocarcinoma: A Comprehensive Review

Mesothelin is a tumor differentiation antigen, which is highly expressed in several solid neoplasms, including pancreatic cancer. Its selective expression on malignant cells and on only a limited number of healthy tissues has made it an interesting candidate for investigation as a diagnostic and prognostic biomarker and as a therapeutic target. Based on a strong preclinical rationale, a number of therapeutic agents targeting mesothelin have entered clinical trials, including immunotoxins, monoclonal antibodies, antibody-drug conjugates, cancer vaccines, and adoptive T cell therapies with chimeric antigen receptors. In pancreatic cancer, mesothelin has been investigated mainly to address two unmet issues: the urgent need for new laboratory techniques for early tumor detection and the lack of successfully targetable oncogenic alterations for patients' treatment. In this review, we describe the clinicopathological significance of mesothelin expression in pancreatic cancer initiation and progression, we summarize available studies evaluating mesothelin as a potential diagnostic and prognostic biomarker in this disease, and we discuss current evidence and future perspectives of preclinical and clinical studies testing mesothelin as a molecular target for pancreatic cancer treatment.

The Impact of Mesothelin in the Ovarian Cancer Tumor Microenvironment

Ovarian cancer is the deadliest gynecological disease among U.S. women. Poor 5-year survival rates (<30%) are due to presentation of most women at diagnosis with advanced stage disease with widely disseminated intraperitoneal metastasis. However, when diagnosed before metastatic propagation the overall 5-year survival rate is >90%. Metastasizing tumor cells grow rapidly and aggressively attach to the mesothelium of all organs within the peritoneal cavity, including the parietal peritoneum and the omentum, producing secondary lesions. In this review, the involvement of mesothelin (MSLN) in the tumor microenvironment is discussed. MSLN, a 40kDa glycoprotein that is overexpressed in many cancers including ovarian and mesotheliomas is suggested to play a role in cell survival, proliferation, tumor progression, and adherence. However, the biological function of MSLN is not fully understood as MSLN knockout mice do not present with an abnormal phenotype. Conversely, MSLN has been shown to bind to the ovarian cancer antigen, CA-125, and thought to play a role in the peritoneal diffusion of ovarian tumor cells. Although the cancer-specific expression of MSLN makes it a potential therapeutic target, more studies are needed to validate the role of MSLN in tumor metastasis.

Yes-associated protein (YAP) in pancreatic cancer: at the epicenter of a targetable signaling network associated with patient survival

Pancreatic ductal adenocarcinoma (PDAC) is generally a fatal disease with no efficacious treatment modalities. Elucidation of signaling mechanisms that will lead to the identification of novel targets for therapy and chemoprevention is urgently needed. Here, we review the role of Yes-associated protein (YAP) and WW-domain-containing Transcriptional co-Activator with a PDZ-binding motif (TAZ) in the development of PDAC. These oncogenic proteins are at the center of a signaling network that involves multiple upstream signals and downstream YAP-regulated genes. We also discuss the clinical significance of the YAP signaling network in PDAC using a recently published interactive open-access database (www.proteinatlas.org/pathology) that allows genome-wide exploration of the impact of individual proteins on survival outcomes. Multiple YAP/TEAD-regulated genes, including AJUBA, ANLN, AREG, ARHGAP29, AURKA, BUB1, CCND1, CDK6, CXCL5, EDN2, DKK1, FOSL1,FOXM1, HBEGF, IGFBP2, JAG1, NOTCH2, RHAMM, RRM2, SERP1, and ZWILCH, are associated with unfavorable survival of PDAC patients. Similarly, components of AP-1 that synergize with YAP (FOSL1), growth factors (TGFα, EPEG, and HBEGF), a specific integrin (ITGA2), heptahelical receptors (P2Y₂R, GPR87) and an inhibitor of the Hippo pathway (MUC1), all of which stimulate YAP activity, are associated with unfavorable survival of PDAC patients. By contrast, YAP inhibitory pathways (STRAD/LKB-1/AMPK, PKA/LATS, and TSC/mTORC1) indicate a favorable prognosis. These associations emphasize that the YAP signaling network correlates with poor survival of pancreatic cancer patients. We conclude that the YAP pathway is a major determinant of clinical aggressiveness in PDAC patients and a target for therapeutic and preventive strategies in this disease.

Yes-associated protein (YAP) signaling contributes to pancreatic cancer progression and is associated with poor patient survival. Previous studies have shown that YAP activates genes involved in cell proliferation to incite tumor growth and metastasis. Enrique Rozengurt and colleagues at University of California Los Angeles review the latest knowledge on YAP signaling and used the open access database The Human Protein Atlas to analyze the gene expression profile and prognosis of 176 patients with pancreatic ductal adenocarcinoma. Activation of upstream or downstream elements of the YAP signaling pathway correlated with shorter survival in patients. Conversely, the activation of signaling pathways that oppose YAP signaling were associated with a more favorable prognosis. These findings highlight YAP signaling pathway components as both prognostic markers and potential targets for developing much needed therapeutic and preventative strategies.

How asbestos drives the tissue towards tumors: YAP activation, macrophage and mesothelial precursor recruitment, RNA editing, and somatic mutations

Chronic exposure to intraperitoneal asbestos triggered a marked response in the mesothelium well before tumor development. Macrophages, mesothelial precursor cells, cytokines, and growth factors accumulated in the peritoneal lavage. Transcriptome profiling revealed YAP/TAZ activation in inflamed mesothelium with further activation in tumors, paralleled by increased levels of cells with nuclear YAP/TAZ. Arg1 was one of the highest upregulated genes in inflamed tissue and tumor. Inflamed tissue showed increased levels of single-nucleotide variations, with an RNA-editing signature, which were even higher in the tumor samples. Subcutaneous injection of asbestos-treated, but tumor-free mice with syngeneic mesothelioma tumor cells resulted in a significantly higher incidence of tumor growth when compared to naïve mice supporting the role of the environment in tumor progression.

Molecular Imaging of Mesothelin-Expressing Ovarian Cancer with a Human and Mouse Cross-Reactive Nanobody

Mesothelin is an epithelial marker highly expressed at the cell surface of cancer cells from diverse origins, including ovarian and pancreatic adenocarcinomas and mesotheliomas. Previously, we identified and characterized an antimesothelin nanobody (NbG3a) for in vitro diagnostic applications. The main goal of this research was to establish the potential of NbG3a as a molecular imaging agent. Site-specific biotinylated NbG3a (bNbG3a) was bound to streptavidin-conjugated reagents for in vitro and in vivo assays. Initially, we performed microscale thermophoresis to determine the binding affinity between bNbG3a and human ( K_d = 46 ± 8 nM) or mouse ( K_d = 4.8 ± 0.4 nM) mesothelin protein. The human and mouse cross-reactivity was confirmed by in vivo optical imaging using bNbG3a bound to fluorescent streptavidin. We also localized the binding site of nNbG3a on human mesothelin using overlapping peptide scan. NbG3a recognized an epitope within residues 21-65 of the mature membrane bound form of human mesothelin, which is part of the N-terminal region of mesothelin that is important for interactions between mesothelin on peritoneal cells and CA125 on tumor cells. Next, the bNbG3a in vivo half-life after intravenous injection in healthy mice was estimated by ELISA assay to be 5.3 ± 1.3 min. In tumor-bearing animals, fluorescent bNbG3a accumulated in a subcutaneous ovarian xenograft (A1847) and in two syngeneic, orthotopic ovarian tumors (intraovary and intraperitoneal ID8) within an hour of intravenous injection that peaked by 4 h and persisted up to 48 h. MRI analysis of bNbG3a-targeted streptavidin-labeled iron oxides showed that the MRI signal intensity decreased 1 h after injection for a subcutaneous xenograft model of ovarian cancer for bNbG3a-labeled iron oxides compared to unlabeled iron oxides. The signal intensity differences continued up to the final time point at 24 h post injection. Finally, in vivo immunofluorescence 24 or 48 h after bNbG3a intravenous injection showed bNbG3a diffuse distribution of both xenograft and syngeneic ovarian tumors, with local areas of high concentration throughout A1847 human tumor. The data support the use of NbG3a for continued preclinical development and translation to human applications for cancers that overexpress mesothelin.

Mesothelin as a target for chimeric antigen receptor-modified T cells as anticancer therapy

Mesothelin is a promising target for immune-based therapy, specifically for mesothelioma and pancreatic and ovarian cancers that have high levels of mesothelin expression. Many preclinical and clinical studies that target tumors with high mesothelin expression with antibodies, immunotoxins, antibody-drug conjugates and vaccines have shown the potential of mesothelin as a target. Studies of T cells genetically modified with chimeric antigen receptors (CAR) report significant efficacy in hematologic malignancies, and antimesothelin CAR T cells are currently being investigated in clinical studies. Here we outline the rationale for using mesothelin as a target for immunotherapy, review the clinical and preclinical studies evaluating mesothelin-directed therapies and explore the promise of CAR T cells directed against mesothelin for immunotherapy in the future.

Mesothelin Immunotherapy for Cancer: Ready for Prime Time?

Mesothelin is a tumor antigen that is highly expressed in many human cancers, including malignant mesothelioma and pancreatic, ovarian, and lung adenocarcinomas. It is an attractive target for cancer immunotherapy because its normal expression is limited to mesothelial cells, which are dispensable. Several antibody-based therapeutic agents as well as vaccine and T-cell therapies directed at mesothelin are undergoing clinical evaluation. These include antimesothelin immunotoxins (SS1P, RG7787/LMB-100), chimeric antimesothelin antibody (amatuximab), mesothelin-directed antibody drug conjugates (anetumab ravtansine, DMOT4039A, BMS-986148), live attenuated Listeria monocytogenes-expressing mesothelin (CRS-207, JNJ-64041757), and chimeric antigen receptor T-cell therapies. Two antimesothelin agents are currently in multicenter clinical registration trials for malignant mesothelioma: amatuximab in the first-line setting and anetumab ravtansine as second-line therapy. Phase II randomized clinical trials of CRS-207 as a boosting agent and in combination with immune checkpoint inhibition for pancreatic cancer are nearing completion. These ongoing studies will define the utility of mesothelin immunotherapy for treating cancer.

Hippo/YAP pathway for targeted therapy

Malignant pleural mesothelioma (MPM) is molecularly characterized by loss of function or mutations in the neurofibromin 2 (NF2) and the cyclin-dependent kinase inhibitor 2 genes. NF2 activates a cascade of kinases, called Hippo pathway, which downregulates Yes associated protein (YAP) function as transcription co-activator for TEA domain transcription factors (TEAD). In the absence of functional NF2, the expression of genes essential for cell cycling such as survivin is increased. New therapeutic strategies aimed at interfering with YAP activity include inhibition of hedgehog pathway, which downregulates the YAP protein, verteporfin, which inhibits the assembly of a functional YAP-TEAD transcription factor, and interference with thrombin and lysophosphatidic acid (LPA) receptors downstream signalling, since upon agonist binding they activate YAP.

Serum IGFBP2 and MSLN as diagnostic and prognostic biomarkers for pancreatic cancer

BACKGROUND

Identification of diagnostic and prognostic biomarkers is a research priority for the improved management of pancreatic ductal adenocarcinoma (PDAC). Insulin-like growth factor binding protein 2 (IGFBP2) and mesothelin (MSLN) have shown potential as serum biomarkers in other cancers, but have not been adequately studied in PDAC.

METHODS

Serum IGFBP2 and MSLN levels were quantified by enzyme-linked immunosorbent assay (ELISA) in a cohort of 84 PDAC patients, 84 healthy control subjects and 40 chronic pancreatitis (ChPT) patients. Regression models related IGFBP2 and MSLN levels to diagnosis, gender, age, stage and survival.

RESULTS

IGFPB2 and MSLN serum levels were diagnostic for PDAC in age-adjusted models (P = 0.032 and P = 0.002, respectively) when compared with ChPT and healthy control samples. At a 95% specificity threshold, the sensitivity for IGFBP2 was 22% and the sensitivity for MSLN was 17%. Neither protein approached the diagnostic accuracy of CA 19-9. However, IGFBP2 or MSLN or both correctly identified 18 of the 28 samples misidentified by CA 19-9. In age-adjusted models, neither serum IGFBP2 (P = 0.36) nor MSLN (P = 0.29) were significant predictors of survival.

DISCUSSION

Serum IGFBP2 and MSLN are weak diagnostic classifiers individually, but may be useful in a diagnostic biomarker panel.

Discovery of mesothelin and exploiting it as a target for immunotherapy

We have recently reported that an immunotoxin targeting mesothelin produced durable major tumor regressions in patients with extensive treatment-refractory mesothelioma. These unprecedented tumor responses have prompted us to review how mesothelin was discovered and the advances that led to these tumor responses. This review is not comprehensive but focuses on major developments over the past 20 years since mesothelin was first identified in our laboratory. Mesothelin is a cell-surface glycoprotein whose expression in normal human tissues is restricted to mesothelial cells. Because it is highly expressed by many solid tumors, it is an attractive immunotherapy target. Antibody-based therapies currently in clinical trials include an immunotoxin, a chimeric monoclonal antibody, and an antibody drug conjugate. In addition, a mesothelin tumor vaccine and a mesothelin- chimeric antigen receptor are being evaluated in the clinic. SS1P, an anti-mesothelin immunotoxin, was the first mesothelin-directed therapy to enter the clinic, and its use showed that mesothelin-targeted therapy was safe in patients. More importantly, our recent work has shown that SS1P in combination with pentostatin and cyclophosphamide can result in durable tumor regression in patients with advanced mesothelioma and opens up the possibility that such an approach can benefit patients with many common cancers.

ANKHD1, a novel component of the Hippo signaling pathway, promotes YAP1 activation and cell cycle progression in prostate cancer cells

ANKHD1 is a multiple ankyrin repeat containing protein, recently identified as a novel member of the Hippo signaling pathway. The present study aimed to investigate the role of ANKHD1 in DU145 and LNCaP prostate cancer cells. ANKHD1 and YAP1 were found to be highly expressed in prostate cancer cells, and ANKHD1 silencing decreased cell growth, delayed cell cycle progression at the S phase, and reduced tumor xenograft growth. Moreover, ANKHD1 knockdown downregulated YAP1 expression and activation, and reduced the expression of CCNA2, a YAP1 target gene. These findings indicate that ANKHD1 is a positive regulator of YAP1 and promotes cell growth and cell cycle progression through Cyclin A upregulation.

C-ERC/mesothelin provokes lymphatic invasion of colorectal adenocarcinoma

BACKGROUND

Lymph node metastasis is a key event of colorectal cancer (CRC) progression. Mesothelin is expressed in various types of malignant tumor and associated with an unfavorable prognosis. The full-length mesothelin (Full-ERC) is cleaved by protease into membrane-bound C-ERC/mesothelin and N-ERC/mesothelin which is secreted into the blood. The aim of this study was to examine the biological role of mesothelin in CRC by clinicopathological analysis and in vitro lymphatic invasion assay.

METHODS

Ninety-one cases of CRC specimens were immunohistochemically examined and the localization of mesothelin in luminal membrane and/or cytoplasm was also evaluated. Lymphatic invasion assay was also performed using the human CRC cell line, WiDr, which was transfected with Full-, N- and C-ERC/mesothelin expression plasmids (Full-WiDr, N-WiDr and C-WiDr).

RESULTS

Immunohistochemically, "luminal membrane positive" of mesothelin was identified in 37.4 %, and correlated with lymphatic permeation and lymph node metastasis, but not with patients' prognosis. Interestingly, among the patients with lymph node metastasis (N = 38), "luminal membrane positive" of mesothelin significantly correlated with unfavorable patients' outcome. In addition, lymphatic invasion assay revealed that Full-WiDr and C-WiDr more significantly invaded human lymphatic endothelial cells than the Mock-WiDr (P < 0.01).

CONCLUSION

The luminal membrane expression of mesothelin was associated with unfavorable prognosis of CRC patients with lymph node metastasis. Moreover, this is the first report to prove the biological function of C-ERC/mesothelin associated with lymphatic invasion of cancer in vitro.

The role of mesothelin in tumor progression and targeted therapy

Mesothelin, a glycosylphosphatidylinositol (GPI) anchored cell surface protein, is a potential target for antibody-based cancer therapy due to its high expression in mesothelioma, ovarian cancer, pancreatic cancer, cholangiocarcinoma and other cancers. The SS1P immunotoxin and MORAb-009 (amatuximab), a chimeric monoclonal antibody, are currently being evaluated in clinical trials. In this review, we discuss the role of mesothelin in cancer progression and provide new insights into mesothelin-targeted cancer therapy. Recent studies highlight three mechanisms by which mesothelin plays a role in cancer progression. First, mesothelin may aid in the peritoneal implantation and metastasis of tumors through its interaction with mucin MUC16 (also known as CA125). Second, mesothelin may promote cancer cell survival and proliferation via the NF-κB signaling pathway. Finally, mesothelin expression promotes resistance to certain chemotherapy drugs such as TNF-α, paclitaxel, and a combination of platinum and cyclophosphamide. However, its cancerspecific expression makes mesothelin a potential target for monoclonal antibody therapy. New human monoclonal antibodies targeting mesothelin have been isolated by phage display technology and may provide opportunities for novel cancer therapy.

"Selective cell death mediated by small conditional RNAs" is not selective

Small conditional RNAs were used to kill cells selectively in a prior report. The method utilized the cellular innate immune response to dsRNA, causing PKR activation and cell death. We designed small conditional RNAs specific to a highly restricted transcript, that of the mesothelin gene expressed in various cancer lines and specific to a tpc/hpr fusion transcript expressed in a published "control" line. Hairpins of small conditional RNAs were functionally active in cell-free conditions. Hairpins were transfected into 6 types of cells. We observed non-specific killing of cells after transfection of the hairpins targeting the reported fusion transcript or of the mesothelin transcript. Thus when attempting to use this system for a special purpose, to target cancer mutations, the results were not satisfactory. Specifically when repeating the work described in the publication, we could not replicate the results using the methods described. Recently the publication was retracted but without comment on the validity of the reported method. Here we provide scientific basis to consider the method impaired or invalid.

A thymidylate synthase ternary complex-specific antibody, FTS, permits functional monitoring of fluoropyrimidines dosing

5-Fluorouracil (5FU) and similar fluoropyrimidines induce covalent modification of thymidylate synthase (TS) and inhibit its activity. They are often used to treat solid cancers, but drug resistance and toxicity are drawbacks. Therefore, there is an unmet need for a functional assay to quantify fluorouracil activity in tissues, so as to individually tailor dosing. It is cumbersome to separately quantify unmodified and 5FU-modified TS using currently available commercial anti-TS antibodies because they recognize both forms. We report here the first monoclonal antibody (FTS) specific to 5FU-modified TS. By immunoblot assay, the FTS antibody specifically recognizes modified TS in a dose-dependent manner in 5FU-treated cells, in cancer xenograft tissues of 5FU-treated mice, and in the murine tissues. In the same assay, the antibody is nonreactive with unmodified TS in untreated or treated cells and tissues. Speculatively, a high-throughput assay could be enabled by pairing anti-TS antibodies of two specificities, one recognizing only modified TS and another recognizing both forms, to structurally quantify the TS-inhibiting effect of fluorouracil at a cellular or tissue level without requiring prior protein separation. Such a development might aid preclinical analytic studies or make practical the individual tailoring of dosing.

Unbiased discovery of interactions at a control locus driving expression of the cancer-specific therapeutic and diagnostic target, mesothelin

Although significant effort is expended on identifying transcripts/proteins that are up-regulated in cancer, there are few reports on systematic elucidation of transcriptional mechanisms underlying such druggable cancer-specific targets. The mesothelin (MSLN) gene offers a promising subject, being expressed in a restricted pattern normally, yet highly overexpressed in almost one-third of human malignancies and a target of cancer immunotherapeutic trials. CanScript, a cis promoter element, appears to control MSLN cancer-specific expression; its related genomic sequences may up-regulate other cancer markers. CanScript is a 20-nt bipartite element consisting of an SP1-like motif and a consensus MCAT sequence. The latter recruits TEAD (TEA domain) family members, which are universally expressed. Exploration of the active CanScript element, especially the proteins binding to the SP1-like motif, thus could reveal cancer-specific features having diagnostic or therapeutic interest. The efficient identification of sequence-specific DNA-binding proteins at a given locus, however, has lagged in biomarker explorations. We used two orthogonal proteomics approaches--unbiased SILAC (stable isotope labeling by amino acids in cell culture)/DNA affinity-capture/mass spectrometry survey (SD-MS) and a large transcription factor protein microarray (TFM)--and functional validation to explore systematically the CanScript interactome. SD-MS produced nine candidates, and TFM, 18. The screens agreed in confirming binding by TEAD proteins and by newly identified NAB1 and NFATc. Among other identified candidates, we found functional roles for ZNF24, NAB1 and RFX1 in MSLN expression by cancer cells. Combined interactome screens yield an efficient, reproducible, sensitive, and unbiased approach to identify sequence-specific DNA-binding proteins and other participants in disease-specific DNA elements.