Mesothelin overexpression promotes mesothelioma cell invasion and MMP-9 secretion in an orthotopic mouse model and in epithelioid pleural mesothelioma patients

CAR T-cell therapy for pancreatic cancer

Chimeric antigen receptor (CAR) T-cell therapy utilizes genetic engineering to redirect a patient's own T cells to target cancer cells. The remarkable results in hematological malignancies prompted investigating this approach in solid tumors such as pancreatic cancer. The complex tumor microenvironment, stromal hindrance in limiting immune response, and expression of checkpoint blockade on T cells pose hurdles. Herein, we summarize the opportunities, challenges, and state of knowledge in targeting pancreatic cancer with CAR T-cell therapy.

Mesothelin promotes epithelial-to-mesenchymal transition and tumorigenicity of human lung cancer and mesothelioma cells

Background

Lung cancer and pleural mesothelioma are two of the most deadly forms of cancer. The prognosis of lung cancer and mesothelioma is extremely poor due to limited treatment modalities and lack of understanding of the disease mechanisms. We have identified mesothelin as a potentially unique therapeutic target that as a specific advantage appears nonessential in most cell types. Mesothelin (MSLN), a plasma membrane differentiation antigen, is expressed at a high level in many human solid tumors, including 70% of lung cancer and nearly all mesotheliomas. However, the role of MSLN in the disease process and underlying mechanisms is largely unknown.

Methods

ShRNA knockdown and overexpression of MSLN were performed in human cancer cell lines and corresponding normal cells, respectively. Tumorigenic and metastatic effects of MSLN were examined by tumor sphere formation, migration, and invasion assays in vitro, as well as xenograft tumor assay in vivo. EMT and CSCs were detected by qPCR array, immunoblotting and flow cytometry.

Results

MSLN plays a key role in controlling epithelial-to-mesenchymal transition (EMT) and stem properties of human lung cancer and mesothelioma cells that control their tumorigenicity and metastatic potential. Firstly, MSLN was found to be highly upregulated in non-small cell lung cancer (NSCLC) patient tissues and in lung carcinoma and mesothelioma cell lines. Secondly, genetic knockdown of MSLN significantly reduced anchorage-independent cell growth, tumor sphere formation, cell adhesion, migration and invasion in vitro, as well as tumor formation and metastasis in vivo. Thirdly, ectopic overexpression of MSLN induced the malignant phenotype of non-cancerous cells, supporting its role as an oncogene. Finally, mechanistic studies revealed that knockdown of MSLN reversed EMT and attenuated stem cell properties, in addition to inhibiting tumor growth and metastasis.

Conclusions

These results indicate an essential role of MSLN in controlling EMT and stem cell properties of human lung cancer and mesothelioma cells. Since EMT is an important process in tumor progression and metastasis, and MSLN is nonessential in most normal tissue, our findings on MSLN may provide new insights into the disease mechanisms and may aid in the development of novel targeted therapy for lung cancer and mesothelioma.

Mesothelin Expression in Gastric Adenocarcinoma and Its Relation to Clinical Outcomes

Background

Although surgical resection with chemotherapy is considered effective for patients with advanced gastric cancer, it remains the third leading cause of cancer-related death in South Korea. Several studies have reported that mesothelial markers including mesothelin, calretinin, and Wilms tumor protein 1 (WT1) were positive in variable carcinomas, associated with prognosis, and were evaluated as potential markers for targeted therapy. The aim of this study was to assess the immunohistochemical expression of mesothelial markers (mesothelin, calretinin, and WT1) in gastric adenocarcinoma and their relations to clinocopathological features and prognosis.

Methods

We evaluated calretinin, WT1, and mesothelin expression by immunohistochemical staining in 117 gastric adenocarcinomas.

Results

Mesothelin was positively stained in 30 cases (25.6%). Mesothelin expression was related to increased depth of invasion (p = .002), lymph node metastasis (p = .013), and presence of lymphovascular (p = .015) and perineural invasion (p = .004). Patients with mesothelin expression had significantly worse disease-free survival rate compared with that of nonmesothelin expression group (p = .024). Univariate analysis showed that mesothelin expression is related to short-term survival. None of the 117 gastric adenocarcinomas stained for calretinin or WT1.

Conclusions

Mesothelin expression was associated with poor prognosis. Our results suggest that mesothelin-targeted therapy should be considered as an important therapeutic alternative for gastric adenocarcinoma patients with mesothelin expression.

Do mesothelin/MUC16 interactions facilitate adenocarcinoma metastases to intracranial meningiomas?

Background:

Meningiomas have been shown to express mesothelin, a high affinity binding site for MUC16, a transmembrane protein on adenocarcinoma cells. The mechanisms underlying adenocarcinoma metastases to meningiomas may provide insight into tumor-to-tumor metastases and adenocarcinoma metastases to leptomeningeal cells.

Methods:

Two meningiomas containing metastases from adenocarcinomas were identified and evaluated immunohistochemically for the expression and localization of mesothelin and MUC16.

Results:

Both meningiomas show extensive mesothelin immunoreactivity, and the adenocarcinomas metastatic to the meningiomas show mesothelin and MUC16 immunoreactivity at the interface with meningioma.

Conclusions:

Interactions between MUC16 and/or mesothelin on the cell membrane of adenocarcinoma cells with mesothelin on meningioma cells may facilitate adenocarcinoma metastases to meningiomas and possibly the leptomeninges.

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.

Biomarkers and prognostic factors for malignant pleural mesothelioma

The increasing incidence and the dismal prognosis of malignant pleural mesothelioma calls for the identification of biomarkers that will allow a timely diagnosis; display prognostic value; and, predict the response to pharmacological agents employed for the treatment of the disease. Biomarkers associated with early diagnosis currently include mesothelin in combination with miRNA miR-103a-3p. As for prognostic biomarkers, the Cancer and Leukemia Group B (CALGB) and the European Organization for Research and Treatment of Cancer (EORTC) scores take into account different hematological and clinical parameters that distinguish patients with good prognosis from those with inferior outcomes. Fluorodeoxyglucose-PET, microarray expression data, neutrophil-to-lymphocyte ratios, c-MET expression, Ki-67 ratios and fibulin-3 levels have also been associated with disease outcome. Finally, thymidylate synthase protein cutoffs may predict mesothelioma response to the association of pemetrexed with a platinum derivative.

Secreted primary human malignant mesothelioma exosome signature reflects oncogenic cargo

Malignant mesothelioma (MM) is a highly-aggressive heterogeneous malignancy, typically diagnosed at advanced stage. An important area of mesothelioma biology and progression is understanding intercellular communication and the contribution of the secretome. Exosomes are secreted extracellular vesicles shown to shuttle cellular cargo and direct intercellular communication in the tumour microenvironment, facilitate immunoregulation and metastasis. In this study, quantitative proteomics was used to investigate MM-derived exosomes from distinct human models and identify select cargo protein networks associated with angiogenesis, metastasis, and immunoregulation. Utilising bioinformatics pathway/network analyses, and correlation with previous studies on tumour exosomes, we defined a select mesothelioma exosomal signature (mEXOS, 570 proteins) enriched in tumour antigens and various cancer-specific signalling (HPGD/ENO1/OSMR) and secreted modulators (FN1/ITLN1/MAMDC2/PDGFD/GBP1). Notably, such circulating cargo offers unique insights into mesothelioma progression and tumour microenvironment reprogramming. Functionally, we demonstrate that oncogenic exosomes facilitate the migratory capacity of fibroblast/endothelial cells, supporting the systematic model of MM progression associated with vascular remodelling and angiogenesis. We provide biophysical and proteomic characterisation of exosomes, define a unique oncogenic signature (mEXOS), and demonstrate the regulatory capacity of exosomes in cell migration/tube formation assays. These findings contribute to understanding tumour-stromal crosstalk in the context of MM, and potential new diagnostic and therapeutic extracellular targets.

The resistance related to targeted therapy in malignant pleural mesothelioma: Why has not the target been hit yet?

Malignant pleural mesothelioma (MPM) is an aggressive tumor of the pleura with a poor prognosis. The most active first-line regimens are platinum compounds and pemetrexed. There is no standard second-line treatment in MPM. Advances in the understanding of tumor molecular biology have led to the development of several targeted treatments, which have been evaluated in clinical trials. Unfortunately none of the explored targeted treatments can currently be recommended as routine treatment in MPM. We reviewed the biological pathways involved in MPM, the clinical trials about targeted therapy, and possible related mechanisms of resistance. We suggest that specific genetic markers are needed as targets of selective therapy. By this way the selection of patients based on the molecular profile may facilitate a therapeutic strategy that allows the use of the most appropriate drug for each patient.

Human CAR T cells with cell-intrinsic PD-1 checkpoint blockade resist tumor-mediated inhibition

Following immune attack, solid tumors upregulate coinhibitory ligands that bind to inhibitory receptors on T cells. This adaptive resistance compromises the efficacy of chimeric antigen receptor (CAR) T cell therapies, which redirect T cells to solid tumors. Here, we investigated whether programmed death-1-mediated (PD-1-mediated) T cell exhaustion affects mesothelin-targeted CAR T cells and explored cell-intrinsic strategies to overcome inhibition of CAR T cells. Using an orthotopic mouse model of pleural mesothelioma, we determined that relatively high doses of both CD28- and 4-1BB-based second-generation CAR T cells achieved tumor eradication. CAR-mediated CD28 and 4-1BB costimulation resulted in similar levels of T cell persistence in animals treated with low T cell doses; however, PD-1 upregulation within the tumor microenvironment inhibited T cell function. At lower doses, 4-1BB CAR T cells retained their cytotoxic and cytokine secretion functions longer than CD28 CAR T cells. The prolonged function of 4-1BB CAR T cells correlated with improved survival. PD-1/PD-1 ligand [PD-L1] pathway interference, through PD-1 antibody checkpoint blockade, cell-intrinsic PD-1 shRNA blockade, or a PD-1 dominant negative receptor, restored the effector function of CD28 CAR T cells. These findings provide mechanistic insights into human CAR T cell exhaustion in solid tumors and suggest that PD-1/PD-L1 blockade may be an effective strategy for improving the potency of CAR T cell therapies.

Surgical immune interventions for solid malignancies

BACKGROUND

The purpose of this study was to systematically review clinically translatable immunotherapeutic agents that are delivered regionally for solid malignancies.

DATA SOURCES

PubMed and ClinicalTrials.gov were searched for published and registered clinical trials, respectively. The search yielded 334 relevant publications, of which 116 articles were included for review after exclusion criteria were applied.

CONCLUSIONS

There has been an increase in the regional administration of cell-based and viral vector-based clinical trials over the last 5 years. Surgical interventions have been developed for intrapleural, intracranial, intraperitoneal, and intratumoral routes of access to enhance the local delivery of these therapies. Multimodality therapies that combine regional immunotherapy with other local and systemic therapies are demonstrating continued growth as the field of immunotherapy continues to expand.

New therapeutic strategies for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and aggressive malignant disease affecting the mesothelium, commonly associated to asbestos exposure. Therapeutic actions are limited due to the late stage at which most patients are diagnosed and the intrinsic chemo-resistance of the tumor. The recommended systemic therapy for MPM is cisplatin/pemetrexed regimen with a mean overall survival of about 12months and a median progression free survival of less than 6months. Considering that the incidence of this tumor is expected to increase in the next decade and that its prognosis is poor, novel therapeutic approaches are urgently needed. For some tumors, such as lung cancer and breast cancer, druggable oncogenic alterations have been identified and targeted therapy is an important option for these patients. For MPM, clinical guidelines do not recommend biological targeted therapy, mainly because of poor target definition or inappropriate trial design. Further studies are required for a full comprehension of the molecular pathogenesis of MPM and for the development of new target agents. This review updates pre-clinical and clinical data on the efficacy of targeted therapy and immune checkpoint inhibition in the treatment of mesothelioma. Finally, future perspectives in this deadly disease are also discussed.

Clinical impacts of mesothelin expression in gastrointestinal carcinomas

Mesothelin, C-ERC/mesothelin is a 40-kDa cell surface glycoprotein that is normally present on normal mesothelial cells lining the pleura, peritoneum, and pericardium. Moreover, mesothelin has been shown to be overexpressed in several human cancers, including virtually all mesothelioma and pancreatic cancer, approximately 70% of ovarian cancer and extra bile duct cancer, and 50% of lung adenocarcinomas and gastric cancer. The full-length human mesothelin gene encodes the primary product, a 71-kDa precursor protein. The 71-kDa mesothelin precursor is cleaved into two products, 40-kDa C-terminal fragment that remains membrane-bound via glycosylphosphatidylinositol anchor, and a 31-kDa N-terminal fragment, megakaryocyte potentiating factor, which is secreted into the blood. The biological functions of mesothelin remain largely unknown. However, results of recent studies have suggested that the mesothelin may play a role of cell proliferation and migration. In pancreatic cancer, mesothelin expression was immunohistochemically observed in all cases, but absent in normal pancreas and in chronic pancreatitis. Furthermore, the expression of mesothelin was correlated with an poorer patient outcome in several human cancers. The limited mesothelin expression in normal tissues and high expression in many cancers makes it an attractive candidate for cancer therapy. The present review discusses the expression and function of mesothelin in cancer cells and the utility of mesothelin as a target of cancer therapy.

Immunotherapy for non-small cell lung cancer: current concepts and clinical trials

Recent successes in immunotherapeutic strategies are being investigated to combat cancers that have less than ideal responses to standard of care treatment, such as non-small-cell lung cancer. In this paper, we summarize concepts and the current status of immunotherapy for non-small cell lung cancer, including salient features of the major categories of immunotherapy-monoclonal antibody therapy, immune checkpoint blockade, immunotoxins, anticancer vaccines, and adoptive cell therapy.

New Strategies for the Treatment of Solid Tumors with CAR-T Cells

Recent years, we have witnessed significant progresses in both basic and clinical studies regarding novel therapeutic strategies with genetically engineered T cells. Modification with chimeric antigen receptors (CARs) endows T cells with tumor specific cytotoxicity and thus induce anti-tumor immunity against malignancies. However, targeting solid tumors is more challenging than targeting B-cell malignancies with CAR-T cells because of the histopathological structure features, specific antigens shortage and strong immunosuppressive environment of solid tumors. Meanwhile, the on-target/off-tumor toxicity caused by relative expression of target on normal tissues is another issue that should be reckoned. Optimization of the design of CAR vectors, exploration of new targets, addition of safe switches and combination with other treatments bring new vitality to the CAR-T cell based immunotherapy against solid tumors. In this review, we focus on the major obstacles limiting the application of CAR-T cell therapy toward solid tumors and summarize the measures to refine this new cancer therapeutic modality.

Murine mesothelin: characterization, expression, and inhibition of tumor growth in a murine model of pancreatic cancer

Background

Mesothelin has attracted much interest as a tumor specific antigen; it has been reported to promote tumor development and to be a good target for cancer treatment. Most studies to date have used human mesothelin in immunocompromised mice. Since these models do not allow for study of the natural immune response to mesothelin expressing tumors, we have undertaken the characterization of mouse mesothelin so the effects of this protein can be assessed in immunocompetent mouse strains.

Methods

We analyzed mouse mesothelin expression, tissue distribution, shedding and biochemistry. In addition we constructed stable mesothelin overexpressing lines of the pancreatic cancer line Panc02 by two methods and tested them for growth and tumorigencity in vitro and in vivo.

Results

We show here that mouse mesothelin is similar to human mesothelin in biochemical characteristics, tumor expression and tissue distribution, suggesting the mouse may be a suitable model for study of mesothelin. Stable overexpression of mesothelin in a pancreatic cancer cell line did not increase cell proliferation or anchorage-independent growth in vitro, suggesting that mesothelin is not necessarily a tumor progression factor. Surprisingly overexpression of mesothelin inhibited tumor formation in vivo in immunocompetent mice.

Conclusion

The mouse may be a good model for studying mesothelin in the context of an intact immune response. Mesothelin is not necessarily a tumor progression factor, and indeed mesothelin overexpression inhibited tumor growth in immunocompetent mice.

Malignant pleural mesothelioma: an update on diagnosis and treatment options

Malignant pleural mesothelioma (MPM) represents a significant diagnostic and therapeutic challenge and is almost always a fatal disease. Imaging abnormalities are common, but have a limited role in distinguishing mesothelioma from metastatic pleural disease. Similarly, minimally invasive biomarkers have shown promise but also have limitations in the diagnosis of mesothelioma. In experienced centers, cytology and immunohistochemistry are now sufficient to diagnose the epithelioid subtype of mesothelioma, which can reduce the need for more invasive diagnostic investigations. Prognosis of MPM is modestly impacted by oncological treatments. Chemotherapy with cisplatin and pemetrexed is considered the standard of care, though the addition of bevacizumab to the platinum doublet may be the new standard of care. New targeted therapies have demonstrated some promise and are being addressed in clinical trials. This review focuses on the current data on the diagnostic and therapeutic issues of MPM.

Mesothelin-Targeted CARs: Driving T Cells to Solid Tumors

Chimeric antigen receptors (CAR) are synthetic receptors that target T cells to cell-surface antigens and augment T-cell function and persistence. Mesothelin is a cell-surface antigen implicated in tumor invasion, which is highly expressed in mesothelioma and lung, pancreas, breast, ovarian, and other cancers. Its low-level expression in mesothelia, however, commands thoughtful therapeutic interventions. Encouragingly, recent clinical trials evaluating active immunization or immunoconjugates in patients with pancreatic adenocarcinoma or mesothelioma have shown responses without toxicity. Altogether, these findings and preclinical CAR therapy models using either systemic or regional T-cell delivery argue favorably for mesothelin CAR therapy in multiple solid tumors.

SIGNIFICANCE

Recent success obtained with adoptive transfer of CAR T cells targeting CD19 in patients with refractory hematologic malignancies has generated much enthusiasm for T-cell engineering and raises the prospect of implementing similar strategies for solid tumors. Mesothelin is expressed in a wide range and a high percentage of solid tumors, which we review here in detail. Mesothelin CAR therapy has the potential to treat multiple solid malignancies.

Regional delivery of mesothelin-targeted CAR T cell therapy generates potent and long-lasting CD4-dependent tumor immunity

Translating the recent success of chimeric antigen receptor (CAR) T cell therapy for hematological malignancies to solid tumors will necessitate overcoming several obstacles, including inefficient T cell tumor infiltration and insufficient functional persistence. Taking advantage of an orthotopic model that faithfully mimics human pleural malignancy, we evaluated two routes of administration of mesothelin-targeted T cells using the M28z CAR. We found that intrapleurally administered CAR T cells vastly outperformed systemically infused T cells, requiring 30-fold fewer M28z T cells to induce long-term complete remissions. After intrapleural T cell administration, prompt in vivo antigen-induced T cell activation allowed robust CAR T cell expansion and effector differentiation, resulting in enhanced antitumor efficacy and functional T cell persistence for 200 days. Regional T cell administration also promoted efficient elimination of extrathoracic tumor sites. This therapeutic efficacy was dependent on early CD4(+) T cell activation associated with a higher intratumoral CD4/CD8 cell ratios and CD28-dependent CD4(+) T cell-mediated cytotoxicity. In contrast, intravenously delivered CAR T cells, even when accumulated at equivalent numbers in the pleural tumor, did not achieve comparable activation, tumor eradication, or persistence. The ability of intrapleurally administered T cells to circulate and persist supports the concept of delivering optimal CAR T cell therapy through "regional distribution centers." On the basis of these results, we are opening a phase 1 clinical trial to evaluate the safety of intrapleural administration of mesothelin-targeted CAR T cells in patients with primary or secondary pleural malignancies.

Latest developments in our understanding of the pathogenesis of mesothelioma and the design of targeted therapies

Malignant mesothelioma is an aggressive cancer whose pathogenesis is causally linked to occupational exposure to asbestos. Familial clusters of mesotheliomas have been observed in settings of genetic predisposition. Mesothelioma incidence is anticipated to increase worldwide in the next two decades. Novel treatments are needed, as current treatment modalities may improve the quality of life, but have shown modest effects in improving overall survival. Increasing knowledge on the molecular characteristics of mesothelioma has led to the development of novel potential therapeutic strategies, including: molecular targeted approaches, that is the inhibition of vascular endothelial growth factor with bevacizumab; immunotherapy with chimeric monoclonal antibody, immunotoxin, antibody drug conjugate, vaccine and viruses; inhibition of asbestos-induced inflammation, that is aspirin inhibition of HMGB1 activity may decrease or delay mesothelioma onset and/or growth. We elaborate on the rationale behind new therapeutic strategies, and summarize available preclinical and clinical results, as well as efforts still ongoing.

The tumoral and stromal immune microenvironment in malignant pleural mesothelioma: A comprehensive analysis reveals prognostic immune markers

Antitumor immune responses against solid malignancies correlate with improved patient survival. We conducted a comprehensive investigation of immune responses in tumor and tumor-associated stroma in epithelioid malignant pleural mesothelioma with the goal of characterizing the tumor immune microenvironment and identifying prognostic immune markers. We investigated 8 types of tumor-infiltrating immune cells within the tumor nest and tumor-associated stroma, as well as tumor expression of 5 cytokine/chemokine receptors in 230 patients. According to univariate analyses, high densities of tumoral CD4- and CD20-expressing lymphocytes were associated with better outcomes. High expression of tumor interleukin-7 (IL-7) receptor was associated with worse outcomes. According to multivariate analyses, stage and tumoral CD20 detection were independently associated with survival. Analysis of single immune cell infiltration for CD163+ tumor-associated macrophages did not correlate with survival. However, analysis of immunologically relevant cell combinations identified that: (1) high CD163+ tumor-associated macrophages and low CD8+ lymphocyte infiltration had worse prognosis than other groups and (2) low CD163+ tumor associated macrophages and high CD20+ lymphocyte infiltration had better prognosis than other groups. Multivariate analyses demonstrated that CD163/CD8 and CD163/CD20 were independent prognostic factors of survival. With a recent increase in immunotherapy investigations and clinical trials for malignant pleural mesothelioma patients, our observations that CD20+ B lymphocytes and tumor-associated macrophages are prognostic markers provide important information about the tumor microenvironment of malignant pleural mesothelioma.

A novel PET imaging using ⁶⁴Cu-labeled monoclonal antibody against mesothelin commonly expressed on cancer cells

Mesothelin (MSLN) is a 40-kDa cell differentiation-associated glycoprotein appearing with carcinogenesis and is highly expressed in many human cancers, including the majority of pancreatic adenocarcinomas, ovarian cancers, and mesotheliomas, while its expression in normal tissue is limited to mesothelial cells lining the pleura, pericardium, and peritoneum. Clone 11-25 is a murine hybridoma secreting monoclonal antibody (mAb) against human MSLN. In this study, we applied the 11-25 mAb to in vivo imaging to detect MSLN-expressing tumors. In in vitro and ex vivo immunochemical studies, we demonstrated specificity of 11-25 mAb to membranous MSLN expressed on several pancreatic cancer cells. We showed the accumulation of Alexa Fluor 750-labeled 11-25 mAb in MSLN-expressing tumor xenografts in athymic nude mice. Then, 11-25 mAb was labeled with ⁶⁴Cu via a chelating agent DOTA and was used in both in vitro cell binding assay and in vivo positron emission tomography (PET) imaging in the tumor-bearing mice. We confirmed that ⁶⁴Cu-labeled 11-25 mAb highly accumulated in MSLN-expressing tumors as compared to MSLN-negative ones. The ⁶⁴Cu-labeled 11-25 mAb is potentially useful as a PET probe capable of being used for wide range of tumors, rather than ¹⁸F-FDG that occasionally provides nonspecific accumulation into the inflammatory lesions.

New and emerging therapeutic options for malignant pleural mesothelioma: review of early clinical trials

Malignant pleural mesothelioma (MPM) is a rare tumor that is challenging to control. Despite some benefit from using the multimodality-approach (surgery, combination chemotherapy and radiation), survival remains poor. However, current research produced a list of potential therapies. Here, we summarize significant new preclinical and early clinical developments in treatment of MPM, which include mesothelin specific antibody and toxin therapies, interleukin-4 (IL-4) receptor toxins, dendritic cell vaccines, immune checkpoint inhibitors, and gene-based therapies. In addition, several local modalities such as photodynamic therapy, postoperative lavage using betadine, and cryotherapy for local recurrence, have also shown to be effective for local control of disease.

Mesothelin expression in triple negative breast carcinomas correlates significantly with basal-like phenotype, distant metastases and decreased survival

Mesothelin is a cell surface associated antigen expressed on mesothelial cells and in some malignant neoplasms. Mesothelin-targeted therapies are in phase I/II clinical trials. The clinicopathologic and prognostic significance of mesothelin expression in triple negative breast carcinomas (TNBC) has not been fully assessed. We evaluated the expression of mesothelin and of basal markers in tissue microarrays of 226 TNBC and 88 non-TNBC and assessed the clinicopathologic features of mesothelin-expressing breast carcinomas. Furthermore, we investigated the impact of mesothelin expression on the disease-free and overall survival of patients with TNBC. We found that mesothelin expression is significantly more frequent in TNBC than in non-TNBC (36% vs 16%, respectively; p = 0.0006), and is significantly correlated with immunoreactivity for basal keratins, but not for EGFR. Mesothelin-positive and mesothelin-negative TNBC were not significantly different by patients’ race, tumor size, histologic grade, tumor subtype, lymphovascular invasion and lymph node metastases. Patients with mesothelin-positive TNBC were older than patients with mesothelin-negative TNBC, developed more distant metastases with a shorter interval, and had significantly lower overall and disease-free survival. Based on our results, patients with mesothelin-positive TNBC could benefit from mesothelin-targeted therapies.

Malignant pleural mesothelioma: new hope in the horizon with novel therapeutic strategies

Malignant pleural mesothelioma (MPM) is a rare but aggressive malignancy of the pleura, with a strong causal link to asbestos exposure. MPM incidence has been increasing in recent years and it is not expected to fall off in the next two decades. Prognosis of MPM patients is modest since the vast majority of patients are diagnosed at advanced stage and because platinum-based chemotherapy remains the cornerstone of treatment, with no standard second line treatment. Most current efforts to improve outcomes are based on a better understanding of the stromal compartment and deregulated pathways leading ultimately to the design of clinical trials based on novel therapeutic approaches such as immunotherapy or molecular-directed compounds. This review seeks to update the last clinical trials investigating novel agents in unresectable MPM.

Intercellular communication in malignant pleural mesothelioma: properties of tunneling nanotubes

Malignant pleural mesothelioma is a particularly aggressive and locally invasive malignancy with a poor prognosis despite advances in understanding of cancer cell biology and development of new therapies. At the cellular level, cultured mesothelioma cells present a mesenchymal appearance and a strong capacity for local cellular invasion. One important but underexplored area of mesothelioma cell biology is intercellular communication. Our group has previously characterized in multiple histological subtypes of mesothelioma a unique cellular protrusion known as tunneling nanotubes (TnTs). TnTs are long, actin filament-based, narrow cytoplasmic extensions that are non-adherent when cultured in vitro and are capable of shuttling cellular cargo between connected cells. Our prior work confirmed the presence of nanotube structures in tumors resected from patients with human mesothelioma. In our current study, we quantified the number of TnTs/cell among various mesothelioma subtypes and normal mesothelial cells using confocal microscopic techniques. We also examined changes in TnT length over time in comparison to cell proliferation. We further examined potential approaches to the in vivo study of TnTs in animal models of cancer. We have developed novel approaches to study TnTs in aggressive solid tumor malignancies and define fundamental characteristics of TnTs in malignant mesothelioma. There is mounting evidence that TnTs play an important role in intercellular communication in mesothelioma and thus merit further investigation of their role in vivo.

Current issues in malignant pleural mesothelioma evaluation and management

Malignant pleural mesothelioma (MPM) is an uncommon disease most often associated with occupational asbestos exposure and is steadily increasing in worldwide incidence. Patients typically present at an older age, with advanced clinical stage and other medical comorbidities, making management quite challenging. Despite great efforts, the prognosis of MPM remains poor, especially at progression after initial treatment. Macroscopic complete resection of MPM can be achieved through extrapleural pneumonectomy (EPP) or extended (ie, radical) pleurectomy (e-P/D) in selected patients and can result in prolonged survival when incorporated into a multimodality approach. Given the morbidity associated with surgical resection of MPM, optimizing identification of appropriate patients is essential. Unfortunately, most patients are not candidates for EPP or e-P/D due to advanced stage, age, and/or medical comorbidity. Pemetrexed and platinum combination chemotherapy has become the cornerstone of therapy for patients with unresectable disease because the combination is associated with improved survival and quality of life in treated patients. However, MPM eventually becomes resistant to initial therapy, and benefit to further lines of therapy has not been substantiated in randomized clinical trials. Translational research has provided exciting insights into tumorigenesis, biomarkers, and immune response in MPM, leading to the development of multiple novel therapeutic agents that are currently in clinical trials. These advances hold the promise of a new era in the treatment of MPM and suggest that this disease will not be left behind in the war on cancer.

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.

Differential expression of extracellular matrix constituents and cell adhesion molecules between malignant pleural mesothelioma and mesothelial hyperplasia

INTRODUCTION

Malignant pleural mesothelioma (MPM) is a highly aggressive neoplasm associated with asbestos exposure. Currently, the molecular mechanisms that induce MPM development are still unknown. The purpose of this study was to identify new molecular biomarkers for mesothelial carcinogenesis.

METHODS

We analyzed a panel of 84 genes involved in extracellular matrix remodeling and cell adhesion by polymerase chain reaction (PCR) array in 15 samples of epithelioid mesothelioma and 10 samples of reactive mesothelial hyperplasia (MH; 3 of 25 samples were inadequate for mRNA analysis). To validate the differentially expressed genes identified by PCR array, we analyzed 27 more samples by immunohistochemistry, in addition to the 25 samples already studied.

RESULTS

Twenty-five genes were differentially expressed in MPM and MH by PCR array. Of these we studied matrix metalloproteinase 7 (MMP7), MMP14, CD44, and integrin, alpha3 expression by immunohistochemistry in 26 epithelioid MPM and 26 MH samples from the entire series of 52 cases. We observed higher MMP14 and integrin, alpha3 expression in MPM samples compared with MH samples (p = 0.000002 and p = 0.000002, respectively). Conversely, CD44 expression was low in most (57.7%) mesothelioma samples but only in 11.5% of the MH samples (p = 0.0013). As regards MMP7, we did not observe differential expression between MH and MPM samples.

CONCLUSIONS

We have extensively studied genes involved in cell adhesion and extracellular matrix remodeling in MPM and MH samples, gaining new insight into the pathophysiology of mesothelioma. Moreover, our data suggest that these factors could be potential biomarkers for MPM.

Expression of matrix metalloproteinase-2 and 9 in cervical intraepithelial neoplasia and cervical carcinoma among different age groups of premenopausal and postmenopausal women

PURPOSE

The objective was to study the gelatinolytic activity of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in preinvasive and invasive carcinoma of the uterine cervix. The expressions were analysed against different age groups, as to demonstrate whether the expression of MMP-2 and MMP-9 is an early or a late event during the progression of cervical cancer. Additionally, the diagnostic accuracy of MMP-2 and MMP-9 was evaluated with ROC curve.

METHODS

A total number of 180 samples of cervical tissue were studied for MMP-2 and MMP-9 gelatinolytic activity. The cases were selected as to include 63 normal cases, 94 CIN cases and 23 cervical carcinoma cases. Among 94 CIN cases, 40 were CIN1, 26 were CIN2 and 28 were CIN3, as reported by histopathology. The gelatinolytic activities of MMP-2 and MMP-9 were evaluated by gelatin zymography in premenopausal and postmenopausal groups.

RESULTS

MMP-2 expressions (latent and active) were very low in control samples, followed by increase in CIN1, decrease in CIN2 and further increase in advance stages. MMP-9 had also shown the same expression pattern that of MMP-2. While comparing the expression of MMP-2 and MMP-9 in different age groups, we found initial CIN stages were prevalent in early age that expressed considerable amount of MMP-2 and MMP-9, and advance stages of carcinoma cervix were prevalent at an elderly age.

CONCLUSION

Both MMP-2 and MMP-9 have role in cancer progression and remodelling of the ectocervix. Although expression level varies intricately, a distinctive ROC curve demonstrated MMP-2 active form and MMP-9 form could be used in diagnostic purpose in detection of cervical lesion and cancer.

Anetumab ravtansine: a novel mesothelin-targeting antibody-drug conjugate cures tumors with heterogeneous target expression favored by bystander effect

Mesothelin is a tumor differentiation antigen frequently overexpressed in tumors such as mesothelioma, ovarian, pancreatic, and lung adenocarcinomas while showing limited expression in nonmalignant tissues. Mesothelin is therefore an attractive target for cancer therapy using antibody-drug conjugates (ADC). This study describes the detailed characterization of anetumab ravtansine, here referred to as BAY 94-9343, a novel ADC consisting of a human anti-mesothelin antibody conjugated to the maytansinoid tubulin inhibitor DM4 via a disulfide-containing linker. Binding properties of the anti-mesothelin antibody were analyzed using surface plasmon resonance, immunohistochemistry, flow cytometry, and fluorescence microscopy. Effects of BAY 94-9343 on cell proliferation were first studied in vitro and subsequently in vivo using subcutaneous, orthotopic, and patient-derived xenograft tumor models. The antibody binds to human mesothelin with high affinity and selectivity, thereby inducing efficient antigen internalization. In vitro, BAY 94-9343 demonstrated potent and selective cytotoxicity of mesothelin-expressing cells with an IC(50) of 0.72 nmol/L, without affecting mesothelin-negative or nonproliferating cells. In vivo, BAY 94-9343 localized specifically to mesothelin-positive tumors and inhibited tumor growth in both subcutaneous and orthotopic xenograft models. In addition, BAY 94-9343 was able to induce a bystander effect on neighboring mesothelin-negative tumor cells. Antitumor efficacy of BAY 94-9343 correlated with the amount of mesothelin expressed and was generally superior to that of standard-of-care regimen resulting in complete tumor eradication in most of the models. BAY 94-9343 is a selective and highly potent ADC, and our data support its development for the treatment of patients with mesothelin-expressing tumors.

Promotion of lung adenocarcinoma following inhalation exposure to multi-walled carbon nanotubes

BACKGROUND

Engineered carbon nanotubes are currently used in many consumer and industrial products such as paints, sunscreens, cosmetics, toiletries, electronic processes and industrial lubricants. Carbon nanotubes are among the more widely used nanoparticles and come in two major commercial forms, single-walled carbon nanotubes (SWCNT) and the more rigid, multi-walled carbon nanotubes (MWCNT). The low density and small size of these particles makes respiratory exposures likely. Many of the potential health hazards have not been investigated, including their potential for carcinogenicity. We, therefore, utilized a two stage initiation/promotion protocol to determine whether inhaled MWCNT act as a complete carcinogen and/or promote the growth of cells with existing DNA damage. Six week old, male, B6C3F1 mice received a single intraperitoneal (ip) injection of either the initiator methylcholanthrene(MCA, 10 μg/g BW, i.p.), or vehicle (corn oil). One week after i.p. injections, mice were exposed by inhalation to MWCNT (5 mg/m³, 5 hours/day, 5 days/week) or filtered air (controls) for a total of 15 days. At 17 months post-exposure, mice were euthanized and examined for lung tumor formation.

RESULTS

Twenty-three percent of the filtered air controls, 26.5% of the MWCNT-exposed, and 51.9% of the MCA-exposed mice, had lung bronchiolo-alveolar adenomas and lung adenocarcinomas. The average number of tumors per mouse was 0.25, 0.81 and 0.38 respectively. By contrast, 90.5% of the mice which received MCA followed by MWCNT had bronchiolo-alveolar adenomas and adenocarcinomas with an average of 2.9 tumors per mouse 17 months after exposure. Indeed, 62% of the mice exposed to MCA followed by MWCNT had bronchiolo-alveolar adenocarcinomas compared to 13% of the mice that received filtered air, 22% of the MCA-exposed, or 14% of the MWCNT-exposed. Mice with early morbidity resulting in euthanasia had the highest rate of metastatic disease. Three mice exposed to both MCA and MWCNT that were euthanized early had lung adenocarcinoma with evidence of metastasis (5.5%). Five mice (9%) exposed to MCA and MWCNT and 1 (1.6%) exposed to MCA developed serosal tumors morphologically consistent with sarcomatous mesotheliomas, whereas mice administered MWCNT or air alone did not develop similar neoplasms.

CONCLUSIONS

These data demonstrate that some MWCNT exposures promote the growth and neoplastic progression of initiated lung cells in B6C3F1 mice. In this study, the mouse MWCNT lung burden of 31.2 μg/mouse approximates feasible human occupational exposures. Therefore, the results of this study indicate that caution should be used to limit human exposures to MWCNT.

Re-adapting T cells for cancer therapy: from mouse models to clinical trials

Adoptive T-cell therapy involves the isolation, expansion, and reinfusion of T lymphocytes with a defined specificity and function as a means to eradicate cancer. Our research has focused on specifying the requirements for tumor eradication with antigen-specific T cells and T cells transduced to express a defined T-cell receptor (TCR) in mouse models and then translating these strategies to clinical trials. Our design of T-cell-based therapy for cancer has reflected efforts to identify the obstacles that limit sustained effector T-cell activity in mice and humans, design approaches to enhance T-cell persistence, develop methods to increase TCR affinity/T-cell functional avidity, and pursue strategies to overcome tolerance and immunosuppression. With the advent of genetic engineering, a highly functional population of T cells can now be rapidly generated and tailored for the targeted malignancy. Preclinical studies in faithful and informative mouse models, in concert with knowledge gained from analyses of successes and limitations in clinical trials, are shaping how we continue to develop, refine, and broaden the applicability of this approach for cancer therapy.

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.

Mesothelin overexpression is a marker of tumor aggressiveness and is associated with reduced recurrence-free and overall survival in early-stage lung adenocarcinoma

PURPOSE

In an effort to identify molecular markers of tumor aggressiveness and therapeutic targets in lung adenocarcinoma (ADC), we investigated the expression of mesothelin (MSLN) in lung ADC, as well as its biologic and clinical relevance.

EXPERIMENTAL DESIGN

In a training and validation set of patients with early-stage (I-III) lung ADC (n = 1,209), a tissue microarray consisting of tumors and normal lung tissue was used to examine the association between MSLN expression and recurrence-free survival (RFS) and overall survival (OS). The influence of MSLN overexpression on lung ADC was investigated in vitro and in vivo by use of clinically relevant orthotopic and metastatic xenogeneic and syngeneic mouse models.

RESULTS

MSLN was expressed in 69% of lung ADC tumors, with one in five patients strongly expressing MSLN and no expression in normal lung tissue. Increased MSLN expression was associated with reduced OS [HR = 1.78; 95% confidence interval (CI), 1.26-2.50; P < 0.01] and RFS (HR = 1.67; 95% CI, 1.21-2.27; P < 0.01) in multivariate analyses, even after adjustment for currently known markers of tumor aggressiveness in lung ADC: male sex, smoking history, increasing stage, morphologic pattern, visceral pleural invasion, lymphatic or vascular invasion, and mutation status. In vitro, lung ADC cells overexpressing MSLN demonstrated increased cell proliferation, migration, and invasion; in vivo, mice with MSLN(+) tumors demonstrated decreased survival (P = 0.001).

CONCLUSIONS

MSLN expression in patients with early-stage lung ADC is associated with increased risk of recurrence and reduced OS, indicating that MSLN expression is a molecular marker of tumor aggressiveness and a potential target for therapy.

AHNAK is highly expressed and plays a key role in cell migration and invasion in mesothelioma

The worldwide incidence of the highly aggressive tumor mesothelioma is expected to increase. Mesothelioma is classified into three main histological subtypes: epithelioid, sarcomatoid and biphasic. Although the pathological diagnostic markers for epithelioid are established, to date no adequate marker for sarcomatoid mesothelioma has been found. Thus, a reliable diagnostic marker of sarcomatoid mesothelioma is necessary. In this study, to identify an unknown protein with 120 kDa expressed only in the mesothelioma cell line 211H, we conducted proteomic analysis and found five candidate proteins. One such protein, AHNAK, was highly expressed in all seven mesothelioma cell lines (211H, H28, H226, H2052, H2452, MESO1 and MESO4), but not in the mesothelial cell line MeT-5A by RT-PCR and immunofluorescence staining. Furthermore, we confirmed high AHNAK expression not only in xenografts but also in human mesothelioma specimens including sarcomatoid, epithelioid and biphasic mesothelioma using immunohistochemical staining. These findings suggest that AHNAK has the potential to be a new marker for detecting mesothelioma. Since AHNAK is involved in cell migration and invasion in other metastatic tumor cells, we conducted migration and invasion assays in mesothelioma cell lines. The number of migrating cells in six of seven mesothelioma cell lines and the number of invading cells in all seven cell lines were significantly increased compared with those in MeT-5A. Knockdown of AHNAK significantly reduced the cell migration and invasion ability in all seven mesothelioma cell lines. These results support further clinical evaluation of the association of AHNAK and metastasis in mesothelioma.

Mesothelin binding to CA125/MUC16 promotes pancreatic cancer cell motility and invasion via MMP-7 activation

Mesothelin (MSLN) and cancer antigen125/mucin 16 (CA125/MUC16) are potential biomarkers for pancreatic cancer (PC) that are co-overexpressed at the invading edges of PC tissues, and their expression correlates with poor survival rates. However, the role of MSLN-MUC16 molecular interaction in PC cell motility and invasion has yet to be elucidated. Using sophisticated bioengineering and molecular biology tools, we report that the binding of MSLN to MUC16 markedly enhances PC cell motility and invasion via the selective induction of matrix metalloproteinase (MMP)-7. MSLN-mediated MMP-7 upregulation in MUC16-expressing PC cells occurs via a p38 MAPK-dependent pathway. Depletion of MMP-7 or inhibition of p38 activity abolishes MSLN-mediated PC motility and invasion. These findings provide a novel perspective on the enhanced invasive potential associated with MSLN and MUC16 co-overexpression, and the mechanism underlying MMP-7 activation in PC invasion and metastasis.

Mesothelin promotes invasion and metastasis in breast cancer cells

OBJECTIVE

The presence of mesothelin (encoded by the mesothelin [MSLN] gene) in breast cancer is associated with tumour infiltration of the lymph node. This study evaluated whether MSLN overexpression promotes breast cancer cell invasiveness and metastasis.

METHODS

This study evaluated the effects of overexpression of MSLN on extracellular signal-regulated kinase (ERK1/2) and matrix metalloproteinase (MMP)-9 levels, and the invasiveness and angiogenesis of the breast cancer cell line MCF-7 in vitro, and on MCF-7-derived tumour development in vivo.

RESULTS

MSLN overexpression significantly increased ERK1/2 and MMP9 protein levels and activity, and the invasive and angiogenic capability of MCF-7 cells, in vitro. Inhibition of ERK1/2 suppressed MMP-9 and the invasive and angiogenic capability of MSLN overexpressing MCF-7 cells. MSLN overexpression also increased MCF-7-derived tumour metastasis in vivo.

CONCLUSION

MSLN overexpression promoted the invasive potential of MCF-7 cells through ERK1/2-dependent upregulation of MMP-9; this association may have contributed to metastasis of MCF-7 cells in vivo. Mesothelin may be a useful biomarker for cancer progression and a novel therapeutic or chemopreventive target in human breast cancer.