High mesothelin correlates with chemoresistance and poor survival in epithelial ovarian carcinoma. Br J Cancer. 2009;100:1144-1153. [PMID: 19293794 PMCID: PMC2669998 DOI: 10.1038/sj.bjc.6604964]

Diagnosis of Pleural Mesothelioma: Is Everything Solved at the Present Time?

Ranked high in worldwide growing health issues, pleural diseases affect approximately one million people globally per year and are often correlated with a poor prognosis. Among these pleural diseases, malignant pleural mesothelioma (PM), a neoplastic disease mainly due to asbestos exposure, still remains a diagnostic challenge. Timely diagnosis is imperative to define the most suitable therapeutic approach for the patient, but the choice of diagnostic modalities depends on operator experience and local facilities while bearing in mind the yield of each diagnostic procedure. Since the analysis of pleural fluid cytology is not sufficient in differentiating historical features in PM, histopathological and morphological features obtained via tissue biopsies are fundamental. The quality of biopsy samples is crucial and often requires highly qualified expertise. Since adequate tissue biopsy is essential, medical or video-assisted thoracoscopy (MT or VATS) is proposed as the most suitable approach, with the former being a physician-led procedure. Indeed, MT is the diagnostic gold standard for malignant pleural pathologies. Moreover, this medical or surgical approach can allow diagnostic and therapeutic procedures: it provides the possibility of video-assisted biopsies, the drainage of high volumes of pleural fluid and the administration of sterile calibrated talcum powder under visual control in order to achieve pleurodesis, placement of indwelling pleural catheters if required and in a near future potential intrapleural therapy. In this context, dedicated diagnostic pathways remain a crucial need, especially to quickly and properly diagnose PM. Lastly, the interdisciplinary approach and multidisciplinary collaboration should always be implemented in order to direct the patient to the best customised diagnostic and therapeutic pathway. At the present time, the diagnosis of PM remains an unsolved problem despite MDT (multidisciplinary team) meetings, mainly because of the lack of standardised diagnostic work-up. This review aims to provide an overview of diagnostic procedures in order to propose a clear strategy.

Role of TIM-3 in ovarian cancer: the forsaken cop or a new noble

T cell immunoglobulin and mucin domain-3 (TIM-3), a crucial immune checkpoint following PD1 and CTLA4, is widely found in several immune cells. Nonetheless, its performance in recent clinical trials appears disappointing. Ovarian cancer (OC), a malignant tumor with a high mortality rate in gynecology, faces significant hurdles in immunotherapy. The broad presence of TIM-3 offers a new opportunity for immunotherapy in OC. This study reviews the role of TIM-3 in OC and assesses its potential as a target for immunotherapy. The regulatory effects of TIM-3 on the immune microenvironment in OC are discussed, with a focus on preclinical studies that demonstrate TIM-3's modulation of various immune cells in OC. Additionally, the potential therapeutic advantages and challenges of targeting TIM-3 in OC are examined.

Targeted Therapy in Mesotheliomas: Uphill All the Way

Mesothelioma (MM) is an aggressive and lethal disease with few therapeutic opportunities. Platinum-pemetrexed chemotherapy is the backbone of first-line treatment for MM. The introduction of immunotherapy (IO) has been the only novelty of the last decades, allowing an increase in survival compared to standard chemotherapy (CT). However, IO is not approved for epithelioid histology in many countries. Therefore, therapy for relapsed MM remains an unmet clinical need, and the prognosis of MM remains poor, with an average survival of only 18 months. Increasing evidence reveals MM complexity and heterogeneity, of which histological classification fails to explain. Thus, scientific focus on possibly new molecular markers or cellular targets is increasing, together with the search for target therapies directed towards them. The molecular landscape of MM is characterized by inactivating tumor suppressor alterations, the most common of which is found in CDKN2A, BAP1, MTAP, and NF2. In addition, cellular targets such as mesothelin or metabolic enzymes such as ASS1 could be potentially amenable to specific therapies. This review examines the major targets and relative attempts of therapeutic approaches to provide an overview of the potential prospects for treating this rare neoplasm.

Mesothelin promotes brain metastasis of non-small cell lung cancer by activating MET

BACKGROUND

Brain metastasis (BM) is common among cases of advanced non-small cell lung cancer (NSCLC) and is the leading cause of death for these patients. Mesothelin (MSLN), a tumor-associated antigen expressed in many solid tumors, has been reported to be involved in the progression of multiple tumors. However, its potential involvement in BM of NSCLC and the underlying mechanism remain unknown.

METHODS

The expression of MSLN was validated in clinical tissue and serum samples using immunohistochemistry and enzyme-linked immunosorbent assay. The ability of NSCLC cells to penetrate the blood-brain barrier (BBB) was examined using an in vitro Transwell model and an ex vivo multi-organ microfluidic bionic chip. Immunofluorescence staining and western blotting were used to detect the disruption of tight junctions. In vivo BBB leakiness assay was performed to assess the barrier integrity. MET expression and activation was detected by western blotting. The therapeutic efficacy of drugs targeting MSLN (anetumab) and MET (crizotinib/capmatinib) on BM was evaluated in animal studies.

RESULTS

MSLN expression was significantly elevated in both serum and tumor tissue samples from NSCLC patients with BM and correlated with a poor clinical prognosis. MSLN significantly enhanced the brain metastatic abilities of NSCLC cells, especially BBB extravasation. Mechanistically, MSLN facilitated the expression and activation of MET through the c-Jun N-terminal kinase (JNK) signaling pathway, which allowed tumor cells to disrupt tight junctions and the integrity of the BBB and thereby penetrate the barrier. Drugs targeting MSLN (anetumab) and MET (crizotinib/capmatinib) effectively blocked the development of BM and prolonged the survival of mice.

CONCLUSIONS

Our results demonstrate that MSLN plays a critical role in BM of NSCLC by modulating the JNK/MET signaling network and thus, provides a potential novel therapeutic target for preventing BM in NSCLC patients.

Mesothelin expression in gynecologic carcinosarcoma: clinicopathological significance and correlation with HER2 expression

OBJECTIVE

This study aimed to evaluate mesothelin (MSLN) expression and determine its clinical significance and correlation with human epidermal growth factor receptor 2 (HER2) expression in gynecological carcinosarcoma.

METHODS

We retrospectively evaluated patients with uterine carcinosarcoma (UCS) and ovarian carcinosarcoma (OCS) who underwent surgery between 1997 and 2019. Immunohistochemical staining of formalin-fixed, paraffin-embedded specimens for MSLN (clone SP74) and HER2 (clone 4A5) was also performed. MSLN was scored using the H-score and 4-tired scoring system (0-3+). MSLN positivity was defined as any positive cell at any intensity, while high MSLN expression was defined as an intensity of ≥2+ in ≥30% of tumor cells. HER2 expression was scored according to modified 2018 American Society of Clinical Oncology/College of American Pathologists criteria.

RESULTS

A total of 128 patients were recruited, including 119 with UCS and 9 with OCS. All cases in UCS exhibited MSLN positivity, and 33.9% showed high-MSLN expression. Clinicopathological characteristics were not significantly associated with high or low-MSLN expression. However, the high-MSLN group showed more prolonged overall survival (OS) than the low-MSLN group (not assessed vs. 36.8 months; hazard ratio=0.48, 95% confidence interval=0.26-0.89, p=0.016). HER2-high patients had higher MSLN expression than HER2-negative patients. In high-MSLN and low-MSLN expression groups, HER2 status did not affect OS. OCS showed 100% MSLN positivity, with 66.6% high-MSLN.

CONCLUSION

MSLN expression is widely observed in gynecological carcinosarcomas. Moreover, high-MSLN expression is a favorable prognostic factor for UCS. MSLN could be a promising therapeutic target for UCS, even in the era of anti-HER2 therapy.

Mesothelin Secretion by Pancreatic Cancer Cells Co-opts Macrophages and Promotes Metastasis

Pancreatic ductal adenocarcinoma (PDAC) is a highly metastatic disease, yet effective treatments to inhibit PDAC metastasis are lacking. The rich PDAC tumor microenvironment plays a major role in disease progression. Macrophages are the most abundant immune cell population in PDAC tumors and can acquire a range of functions that either hinder or promote tumor growth and metastasis. Here, we identified that mesothelin secretion by pancreatic cancer cells co-opts macrophages to support tumor growth and metastasis of cancer cells to the lungs, liver, and lymph nodes. Mechanistically, secretion of high levels of mesothelin by metastatic cancer cells induced the expression of VEGF alpha (VEGFA) and S100A9 in macrophages. Macrophage-derived VEGFA fed back to cancer cells to support tumor growth, and S100A9 increased neutrophil lung infiltration and formation of neutrophil extracellular traps. These results reveal a role for mesothelin in regulating macrophage functions and interaction with neutrophils to support PDAC metastasis.

SIGNIFICANCE

Mesothelin secretion by cancer cells supports pancreatic cancer metastasis by inducing macrophage secretion of VEGFA and S100A9 to support cancer cell proliferation and survival, recruit neutrophils, and stimulate neutrophil extracellular trap formation. See related commentary by Alewine, p. 513.

Biology of Mesothelin and Clinical Implications: A Review of Existing Literature

Since its discovery in 1992, mesothelin (MSLN) has generated significant interest as a therapeutic target. A number of characteristics make it ideal for this purpose. First, it is not expressed on the parenchyma of any vital organs. Second, it is differentially expressed on a number of cancer types that have relatively poor prognosis and lack effective systemic options. Third, it is expressed on the cell membrane making it accessible to large molecule targeted therapies. However, unlike other drug targets that have been exploited for therapeutic benefit, the precise function of MSLN, why it is expressed in certain cancers, and its biological role have not been clearly elucidated. Here the existing literature on the cellular function and expression patterns of MSLN across tumor types is reviewed in order to gain further understanding of this intriguing molecule. In doing so, we conclude that there remains significant ambiguity surrounding its function and role in cellular and tumor biology. Furthermore, the expression of MSLN and its relation of prognosis seems to depend on the type of tumor. Finally, the unified mechanism by which MSLN acts as a protein that conveys tumor aggressiveness remains elusive. What is clear is that there is much yet to be discovered in this realm and doing so may have large implications for treatment of otherwise lethal malignancies.

High Mesothelin expression in pancreatic adenocarcinoma is associated with aggressive tumor features but not prognosis

Mesothelin is a cell surface marker expressed on most pancreatic cancers and has been associated with aggressive biology. Despite its popularity as a drug target, clinical relevance of Mesothelin expression in pancreatic cancer is unclear. We set out to define transcriptomic signatures associated with high Mesothelin expression and identify its role in tumor biology and its clinical relevance. We analyzed pancreatic adenocarcinomas in the cancer genome atlas (TCGA), (n = 145) and the results were validated using GSE62452 cohort (n = 69). We divided the cohorts into high and low Mesothelin expression by the median. High Mesothelin was not associated with progression-free, disease-free, disease specific, nor overall survival in TCGA cohort. Despite this, high Mesothelin expression was associated with high Ki67 expression and enriched all five cell proliferation-related Hallmark gene sets, but not with previously investigated pathways: TNF-alpha, PI3K, nor angiogenesis. Mesothelin expression did not correlate with MUC16 expression. The high Mesothelin pancreatic cancers demonstrated higher homologous recombination deficiency, fraction altered, and silent and non-silent mutation rates (all P < 0.001) that indicate aggressive cancer biology. However, lymphocyte infiltration score, TIL regional fraction, TCR richness, infiltration of CD8 T-cells, and cytolytic activity were all significantly lower in Mesothelin high tumors (all P < 0.015). Finally, we found that Mesothelin expression significantly correlated with sensitivity to cytotoxic chemotherapy in pancreatic cancer cell lines. In conclusion, high Mesothelin expression is associated with enhanced proliferation, depressed immune response, and sensitivity to cytotoxic chemotherapy, which may explain there was no difference in survival in pancreatic cancer patients.

Blood Plasma Small Non-Coding RNAs as Diagnostic Molecules for the Progesterone-Receptor-Negative Phenotype of Serous Ovarian Tumors

The expression level of the progesterone receptor (PGR) plays a crucial role in determining the biological characteristics of serous ovarian carcinoma. Low PGR expression is associated with chemoresistance and a poorer outcome. In this study, our objective was to explore the relationship between tumor progesterone receptor levels and RNA profiles (miRNAs, piwiRNAs, and mRNAs) to understand their biological characteristics and behavior. To achieve this, we employed next-generation sequencing of small non-coding RNAs, quantitative RT-PCR, and immunohistochemistry to analyze both FFPE and frozen tumor samples, as well as blood plasma from patients with benign cystadenoma (BSC), serous borderline tumor (SBT), low-grade serous ovarian carcinoma (LGSOC), and high-grade serous ovarian carcinoma (HGSOC). Our findings revealed significant upregulation of MMP7 and MUC16, along with downregulation of PGR, in LGSOC and HGSOC compared to BSC. We observed significant correlations of PGR expression levels in tumor tissue with the contents of miR-199a-5p, miR-214-3p, miR-424-3p, miR-424-5p, and miR-125b-5p, which potentially target MUC16, MMP7, and MMP9, as well as with the tissue content of miR-16-5p, miR-17-5p, miR-20a-5p, and miR-93-5p, which are associated with the epithelial-mesenchymal transition (EMT) of cells. The levels of EMT-associated miRNAs were significantly correlated with the content of hsa_piR_022437, hsa_piR_009295, hsa_piR_020813, hsa_piR_004307, and hsa_piR_019914 in tumor tissues. We developed two optimal logistic regression models using the quantitation of hsa_piR_020813, miR-16-5p, and hsa_piR_022437 or hsa_piR_004307, hsa_piR_019914, and miR-93-5p in the tumor tissue, which exhibited a significant ability to diagnose the PGR-negative tumor phenotype with 93% sensitivity. Of particular interest, the blood plasma levels of miR-16-5p and hsa_piR_022437 could be used to diagnose the PGR-negative tumor phenotype with 86% sensitivity even before surgery and chemotherapy. This knowledge can help in choosing the most effective treatment strategy for this aggressive type of ovarian cancer, such as neoadjuvant chemotherapy followed by cytoreduction in combination with hyperthermic intraperitoneal chemotherapy and targeted therapy, thus enhancing the treatment's effectiveness and the patient's longevity.

The inhibitory receptors PD1, Tim3, and A2aR are highly expressed during mesoCAR T cell manufacturing in advanced human epithelial ovarian cancer

BACKGROUND

Chemotherapy and surgery have been the mainstays of epithelial ovarian cancer (EOC) treatment so far. Cellular immunotherapies such as CAR T cell therapy have recently given hope of a cure for solid tumors like EOC. However, extrinsic factors associated with the CAR T cell manufacturing process and/or intrinsic dysregulation of patient-derived T cells, which could be associated with cancer itself, cancer stage, and treatment regimen, may hamper the efficacy of CAR T cell therapy and promote their exhaustion or dysfunction.

METHODS

To investigate the association of these factors with CAR T cell exhaustion, the frequency of T and CAR T cells expressing three immune inhibitory receptors (i.e., TIM3, PD1, A2aR) generated from T cells of EOC patients and healthy controls was measured during each stage of CAR T cell production.

RESULTS

Our findings revealed that primary T cells from EOC patients show significantly elevated expression of immune inhibitory receptors, and this increase was more prominent in patients undergoing chemotherapy and those with advanced cancer. In addition, the CAR T cell manufacturing process itself was found to upregulate the expression of these inhibitory receptors and more importantly increase the population of exhausted mesoCAR T cells.

CONCLUSIONS

Our observations suggest that intrinsic characteristics of patient-derived T cells and extrinsic factors in CAR T cell production protocols should be considered and properly counteracted during CAR T cell manufacturing process. In addition, mitigating the signaling of immune inhibitory receptors through pharmacological/genetic perturbation during CAR T cell manufacturing might profoundly improve CAR T cells function and their antitumor activity in EOC and other solid tumors.

Challenges of Anti-Mesothelin CAR-T-Cell Therapy

Chimeric antigen receptor (CAR)-T-cell therapy is a kind of adoptive T-cell therapy (ACT) that has developed rapidly in recent years. Mesothelin (MSLN) is a tumor-associated antigen (TAA) that is highly expressed in various solid tumors and is an important target antigen for the development of new immunotherapies for solid tumors. This article reviews the clinical research status, obstacles, advancements and challenges of anti-MSLN CAR-T-cell therapy. Clinical trials on anti-MSLN CAR-T cells show that they have a high safety profile but limited efficacy. At present, local administration and introduction of new modifications are being used to enhance proliferation and persistence and to improve the efficacy and safety of anti-MSLN CAR-T cells. A number of clinical and basic studies have shown that the curative effect of combining this therapy with standard therapy is significantly better than that of monotherapy.

Targeting Mesothelin in Solid Tumours: Anti-mesothelin Antibody and Drug Conjugates

PURPOSE OF REVIEW

This review aims to summarise the pathobiological role of mesothelin and the current data on therapeutic antibodies targeting mesothelin in solid tumours.

RECENT FINDINGS

High mesothelin expression is restricted to the pericardium, pleura, peritoneum and tunica vaginalis. Mesothelin does not seem to have any normal biological function in adult normal tissues. Mesothelin is highly expressed in mesothelioma, serous ovarian cancer, pancreatic cancer and some gastric cancer and adenocarcinoma of the lung and is responsible for tumour proliferation, metastasis, resistance to chemotherapy or radiation and evasion of immune system. To date, antibody, antibody drug conjugates and bispecific antibodies with immune checkpoints have been investigated in mesothelin expressing malignancies. After a couple of decades of clinical investigation in antibody targeting mesothelin, the therapeutic benefit is relatively modest. Novel delivery of mesothelin targeting agents, more potent payload in antibody drug conjugates and immune checkpoint inhibitor, may improve therapeutic benefit.

High mesothelin expression is correlated with non-squamous cell histology and poor survival in cervical cancer: a retrospective study

BACKGROUND

Mesothelin (MSLN) is a cell-surface glycoprotein found in various solid tumours. Cancer therapies targeting MSLN have been developed in recent years; however, the available information on MSLN expression in cervical cancer is limited. This study aimed to evaluate MSLN expression in various histological types of cervical cancer and examine its relationship with prognosis.

METHODS

This retrospective study included patients with cervical cancer who underwent primary surgery between January 2000 and December 2020 at our institution. MSLN expression was evaluated by immunohistochemistry using clone SP74 and defined as positive if MSLN was expressed at any intensity. High MSLN expression was defined as an intensity of ≥ 2 + in ≥ 30% of tumour cells. The association between MSLN expression and clinicopathological factors was evaluated.

RESULTS

Overall, 123 patients were identified, and 140 tumour samples, including 17 paired primary and metastatic samples, were evaluated. Concerning histological type, 67 patients had squamous cell carcinoma (SCC), whereas 56 had non-SCC. MSLN expression was observed in 98.4% (121/123) of primary tumours. High MSLN expression was observed in 63.4% of samples (78/123), but it differed between the histological types (49.2% for SCC vs. 80.4% for non-SCC, p < 0.001). There was a significant correlation between MSLN expression in primary and metastatic lesions (Rs = 0.557, p = 0.015). In patients with common histological types, overall survival (OS) was shorter in the high MSLN expression group than in the low MSLN expression group (hazard ratio, 3.53; 95% confidence interval, 1.16-15.3, p = 0.03).

CONCLUSIONS

MSLN was highly expressed in patients with cervical cancer, especially in those with non-SCC. High MSLN expression in the primary lesion was significantly associated with poor OS, and its expression was maintained in metastatic lesions. Our findings indicate that MSLN may be an attractive therapeutic target for cervical cancer.

TRIAL REGISTRATION

Retrospectively registered. 2014-393. 1 June 2015.

MSLN Correlates With Immune Infiltration and Chemoresistance as a Prognostic Biomarker in Ovarian Cancer

Mesothelin (MSLN) is a glycoprotein with various expression degrees in different tumors including mesothelioma, ovarian cancer, pancreatic cancer, etc. MSLN is considered to play an important role in cell survival, proliferation, and tumor progression. Although the expression of MSLN in tumors makes it a potential therapeutic target, its mechanism of action is still unclear, especially its correlation with immune cells infiltration in the tumor microenvironment has not been investigated. In this study, we detected the overexpression of MSLN in ovarian cancer using database analysis and tissue-array staining. We further evaluated the diagnostic value of MSLN and found it was associated with poor overall survival in ovarian cancer. In addition, the high expression of MSLN was significantly related to the immune-related genes and chemoresistant genes. We confirmed the overexpression of MSLN in the chemoresistant ovarian cancer cell lines. Our research suggests that MSLN participates in a variety of pathways related to the suppression of immune activation and promotion of chemoresistance, leading to a poor prognosis in ovarian cancer.

The Role of Mesothelin Expression in Serous Ovarian Carcinoma: Impacts on Diagnosis, Prognosis, and Therapeutic Targets

Mesothelin (MSLN) is a protein expressed in the mesothelial cell lining of the pleura, peritoneum, and pericardium; its biological functions in normal cells are still unknown. Experimental studies using knockout mice have suggested that this molecule does not play an important role in development and reproduction. In contrast, it has been observed that this molecule is produced in abnormal amounts in several malignant neoplasms, such as mesotheliomas and pancreatic adenocarcinomas. Many molecular studies have also demonstrated that mesothelin is overexpressed in HSOCs. Here, we discuss the current knowledge of mesothelin and focus on its role in clinical and pathological diagnoses, as well as its impact on the prognosis of HSOC. Moreover, regarding the binding of MSLN to the ovarian cancer antigen CA125, which has been demonstrated in many studies, we also report on signal transduction pathways that may play an important role in the spread and neoplastic progression of this lethal neoplasm. Given that mesothelin is overexpressed in many solid tumours and has antigenic properties, this molecule could be considered an antigenic target for the treatment of many malignancies. Consequently, we also review the literature to report on mesothelin-targeting therapies for HSOC that have been recently investigated in many clinical studies.

HLA-DR Presentation of the Tumor Antigen MSLN Associates with Clinical Outcome of Ovarian Cancer Patients

Simple Summary

The immunopeptidome represents the entirety of peptides that are presented on the surface of cells on human leukocyte antigen (HLA) molecules and are recognized by the T-cell receptors of CD4⁺ and CD8⁺ T-cells. Malignant cells present tumor-associated antigens essential for tumor immune surveillance, which can be targeted by T-cell-based immunotherapy approaches. For ovarian carcinomas, various tumor-associated antigens, such as Mucin-16 and Mesothelin, have been described. The aim of our study is to analyze immunopeptidome-defined tumor antigen presentation in ovarian carcinoma patients in relation to clinical characteristics and disease outcomes to define potential biomarkers. Our work demonstrates the central role of HLA-DR-restricted peptide presentation of the tumor antigen Mesothelin and of CD4⁺ T-cell responses for tumor immune surveillance, and underlines Mesothelin as a prime target antigen for novel immunotherapeutic approaches for ovarian carcinoma patients.

Abstract

T-cell recognition of HLA-presented antigens is central for the immunological surveillance of malignant disease and key for the development of novel T-cell-based immunotherapy approaches. In recent years, large-scale immunopeptidome studies identified naturally presented tumor-associated antigens for several malignancies. Regarding ovarian carcinoma (OvCa), Mucin-16 (MUC16) and Mesothelin (MSLN) were recently described as the top HLA class I- and HLA class II-presented tumor antigens, respectively. Here, we investigate the role and impact of immunopeptidome-presented tumor antigens on the clinical outcomes of 39 OvCa patients with a follow-up time of up to 50 months after surgery. Patients with a HLA-restricted presentation of high numbers of different MSLN-derived peptides on their tumors exhibited significantly prolonged progression-free (PFS) and overall survival (OS), whereas the presentation of MUC16-derived HLA class I-restricted peptides had no impact. Furthermore, a high HLA-DRB gene expression was associated with increased PFS and OS. In line, in silico prediction revealed that MSLN-derived HLA class II-presented peptides are predominantly presented on HLA-DR allotypes. In conclusion, the correlation of MSLN tumor antigen presentation and HLA-DRB gene expression with prolonged survival indicates a central role of CD4⁺ T-cell responses for tumor immune surveillance in OvCa, and highlights the importance of immunopeptidome-guided tumor antigen discovery.

Effects of hsa-mir-145-5p on the Regulation of msln Expression in Colorectal Adenocarcinoma

Colorectal cancer (CRC) is one of the most common gastrointestinal cancers in the world, and its incidence is increasing all over the world including China. In recent years, research data show that some miRNAs are differentially expressed in cancer tissues, and their expression is closely contributed with the prognosis of CRC. Microarray technology was used, and 179 miRNAs were screened out with significantly altered expression in CRC tissues compared with adjacent tissues. The expression of mir-145-5p in tumor tissues was 3.48 times lower than that in normal tissues. Using bioinformatics technology and network resource prediction, we found that mir-145-5p had a potential target gene relationship with msln gene. Then, qRT-PCR was used to validate the expression level of mir-145-5p and msln mRNA in CRC and paracancerous tissues. The results showed that msln mRNA was higher than in normal tissues, while mir-145-5p was lower, with statistically significant difference (P < 0.01, n = 3). Furthermore, the expression of msln protein in CRC and normal colorectal tissues was detected by protein mass spectrometry (MRM) (n = 3) and immunohistochemistry in a total case of 30 colorectal cancer tissues and normal tissues. Result showed that the positive expression of msln in CRC was higher than that in normal colorectal tissues, 1.38e-6 and 1.89e-6, respectively (P < 0.01, n = 3). Furthermore, in 48 h RTCA real-time monitoring experiment, mir-145-5p showed inhibitory effect on the proliferation of colo320 cells stimulated by msln. This study demonstrated that msln is a target gene of mir-145-5p in CRC. Besides, mir-145-5p negatively regulates the proliferation of CRC colo320 cells through downregulating msln gene expression in CRC colo320 cells.

Mesothelin Expression Is Not Associated with the Presence of Cancer Stem Cell Markers SOX2 and ALDH1 in Ovarian Cancer

Mesothelin (MSLN) overexpression (OE) is a frequent finding in ovarian carcinomas and increases cell survival and tumor aggressiveness. Since cancer stem cells (CSCs) contribute to pathogenesis, chemoresistance and malignant behavior in ovarian cancer (OC), we hypothesized that MSLN expression could be creating a favorable environment that nurtures CSCs. In this study, we analyzed the expression of MSLN and CSC markers SOX2 and ALDH1 by immunohistochemistry (IHC) in different model systems: primary high-grade serous carcinomas (HGSCs) and OC cell lines, including cell lines that were genetically engineered for MSLN expression by either CRISPR-Cas9-mediated knockout (Δ) or lentivirus-mediated OE. Cell lines, wild type and genetically engineered, were evaluated in 2D and 3D culture conditions and xenografted in nude mice. We observed that MSLN was widely expressed in HGSC, and restricted expression was observed in OC cell lines. In contrast, SOX2 and ALDH1 expression was limited in all tissue and cell models. Most importantly, the expression of CSC markers was independent of MSLN expression, and manipulation of MSLN expression did not affect CSC markers. In conclusion, MSLN expression is not involved in driving the CSC phenotype.

Role of Circulating Biomarkers in Platinum-Resistant Ovarian Cancer

Ovarian cancer (OC) is the second most common cause of death in women with gynecological cancer. Considering the poor prognosis, particularly in the case of platinum-resistant (PtR) disease, a huge effort was made to define new biomarkers able to help physicians in approaching and treating these challenging patients. Currently, most data can be obtained from tumor biopsy samples, but this is not always available and implies a surgical procedure. On the other hand, circulating biomarkers are detected with non-invasive methods, although this might require expensive techniques. Given the fervent hope in their value, here we focused on the most studied circulating biomarkers that could play a role in PtR OC.

Exploiting mesothelin in thymic carcinoma as a drug delivery target for anetumab ravtansine

BACKGROUND

Thymic epithelial tumours (TETs) are rare tumours comprised of thymomas and thymic carcinoma. Novel therapies are needed, especially in thymic carcinoma where the 5-year survival rate hovers at 30%. Mesothelin (MSLN), a surface glycoprotein that is cleaved to produce mature MSLN (mMSLN) and megakaryocyte potentiating factor (MPF), is expressed in limited tissues. However, its expression is present in various cancers, including thymic carcinoma, where it is expressed in 79% of cases.

METHODS

We utilised flow cytometry, in vitro cytotoxicity assays, and an in vivo xenograft model in order to demonstrate the ability of the MSLN targeting antibody-drug conjugate (ADC) anetumab ravtansine (ARav) in inhibiting the growth of thymic carcinoma.

RESULTS

Thymoma and thymic carcinoma cell lines express MSLN, and anetumab, the antibody moiety of ARav, was capable of binding MSLN expressing thymic carcinoma cells and internalising. ARav was effective at inhibiting the growth of thymic carcinoma cells stably transfected with mMSLN in vitro. In vivo, 15 mg/kg ARav inhibited T1889 xenograft tumour growth, while combining 7.5 mg/kg ARav with 4 mg/kg cisplatin yielded an additive effect on inhibiting tumour growth.

CONCLUSIONS

These data demonstrate that anetumab ravtansine inhibits the growth of MSLN positive thymic carcinoma cells in vitro and in vivo.

Disruption of adenosine 2A receptor improves the anti-tumor function of anti-mesothelin CAR T cells both in vitro and in vivo

Chimeric antigen receptor (CAR) T cells have been successfully used for the treatment of hematological malignancies including acute and chronic lymphoblastic leukemia. However, results of CAR T cell projects in solid tumors have been less impressive to date, partly because of immunosuppressive tumor microenvironment (TME). It is widely known that high adenosine production is an important factor causing tumor-induced immunosuppression in TME, and adenosine mediates the suppression of anti-tumor T cell responses via binding and signaling through adenosine 2a receptor (A2aR). Previous studies have shown that adenosine generated by cancer cells significantly inhibits T cell anti-tumor activity through binding and then activating adenosine 2A receptors (A2aRs) of T cells. Based on the previous work, in our study, we evaluated whether A2aR disruption by shRNA could enhance the anti-tumor function of anti-mesothelin (MSLN) CAR T cells both in vitro and in vivo. For this goal above, we used MSLN-positive human ovarian serous carcinoma cells (SKOV3) and human colon cancer cells (HCT116) as target cancer cells while MSLN-negative human ovarian cancer cells (ES2) as non-target cancer cells. We observed that targeting cell-intrinsic A2aR through shRNA overexpression caused significant A2aR disruption in CAR T cells and profoundly increased CAR T cell efficacy in both CAR T cell cytokine production and cytotoxicity towards MSLN-positive cancer cells in vitro. More importantly, in SKOV3 xenograft mouse models, anti-MSLN CAR-T cells significantly reduced the tumor burden compared with non-transduced T cells, and the anti-tumor activity of A2aR-disrupted anti-MSLN CAR-T cells was stronger than that of wild-type anti-MSLN CAR-T cells. Altogether, our study showed enhanced anti-tumor efficacy caused by shRNA-mediated A2aR disruption in anti-MSLN CAR T cells both in vitro and in vivo, which proved that shRNA-mediated modification of gene expression might be an excellent strategy for improving CAR T cell function in immunosuppressive tumor microenvironment (TME) and could potentially improve the outcome of treatment in clinical trials.

Host Mesothelin Expression Increases Ovarian Cancer Metastasis in the Peritoneal Microenvironment

Mesothelin (MSLN), a glycoprotein normally expressed by mesothelial cells, is overexpressed in ovarian cancer (OvCa) suggesting a role in tumor progression, although the biological function is not fully understood. OvCa has a high mortality rate due to diagnosis at advanced stage disease with intraperitoneal metastasis. Tumor cells detach from the primary tumor as single cells or multicellular aggregates (MCAs) and attach to the mesothelium of organs within the peritoneal cavity producing widely disseminated secondary lesions. To investigate the role of host MSLN in the peritoneal cavity we used a mouse model with a null mutation in the MSLN gene (MSLN^KO). The deletion of host MSLN expression modified the peritoneal ultrastructure resulting in abnormal mesothelial cell surface architecture and altered omental collagen fibril organization. Co-culture of murine OvCa cells with primary mesothelial cells regardless of MSLN expression formed compact MCAs. However, co-culture with MSLN^KO mesothelial cells resulted in smaller MCAs. An allograft tumor study, using wild-type mice (MSLN^WT) or MSLN^KO mice injected intraperitoneally with murine OvCa cells demonstrated a significant decrease in peritoneal metastatic tumor burden in MSLN^KO mice compared to MSLN^WT mice. Together, these data support a role for host MSLN in the progression of OvCa metastasis.

Generation of Two Paclitaxel-Resistant High-Grade Serous Carcinoma Cell Lines With Increased Expression of P-Glycoprotein

Debulking surgery followed by chemotherapy are the standard of care for high-grade serous carcinoma. After an initial good response to treatment, the majority of patients relapse with a chemoresistant profile, leading to a poor overall survival. Chemotherapy regimens used in high-grade serous carcinomas are based in a combination of classical chemotherapeutic drugs, namely, Carboplatin and Paclitaxel. The mechanisms underlying drug resistance and new drug discovery are crucial to improve patients’ survival. To uncover the molecular mechanisms of chemoresistance and test drugs capable of overcoming this resistant profile, it is fundamental to use good cellular models capable of mimicking the chemoresistant disease. Herein, we established two high-grade serous carcinoma cell lines with intrinsic resistance to Carboplatin and induced Paclitaxel resistance (OVCAR8 PTX R C and OVCAR8 PTX R P) derived from the OVCAR8 cell line. These two chemoresistant cell line variants acquired an enhanced resistance to Paclitaxel-induced cell death by increasing the drug efflux capacity, and this resistance was stable in long-term culture and following freeze/thaw cycles. The mechanism underlying Paclitaxel resistance resides in a significant increase in P-glycoprotein expression and, when this drug efflux pump was blocked with Verapamil, cells re-acquired Paclitaxel sensitivity. We generated two high-grade serous carcinoma cell lines, with a double-chemoresistant (Carboplatin and Paclitaxel) phenotype that mimics the majority of tumor recurrences in ovarian cancer context. This robust tool is suitable for preliminary drug testing towards the development of therapeutic strategies to overcome chemoresistance.

Chimeric antigen receptor T-cells (CARs) in cancer treatment

BACKGROUND

Cancer is one of the leading causes of death worldwide. Chemotherapy, radiation therapy, and stem cell transplantation were the main cancer treatment approaches for several years but due to their limited effectiveness, there was a constant search for new therapeutic approaches. Cancer immunotherapy that utilizes and enhances the normal capacity of the patient's immune system was used to fight against cancer. Genetically engineered T-cells that express chimeric antigen receptors (CARs) showed remarkable anti-tumor activity against hematologic malignancies and is now being investigated in a variety of solid tumors. The use of this therapy in the last few years has been successful, achieving a great success in improving the quality of life and prolonging the survival time of patients with a reduction in remission rates. However, many challenges still need to be resolved in order for this technology to gain widespread adoption. <P> Objective: This review summarizes various experimental approaches towards the use of CAR T-cells in hematologic malignancies and solid tumors. <P> Conclusion: Finally, we address the challenges posed by CAR T-cells and discuss strategies for improving the performance of these T cells in fighting cancers.

Hitting the Bull's-Eye: Mesothelin's Role as a Biomarker and Therapeutic Target for Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive cancer with limited treatment options and poor prognosis. MPM originates from the mesothelial lining of the pleura. Mesothelin (MSLN) is a glycoprotein expressed at low levels in normal tissues and at high levels in MPM. Many other solid cancers overexpress MSLN, and this is associated with worse survival rates. However, this association has not been found in MPM, and the exact biological role of MSLN in MPM requires further exploration. Here, we discuss the current research on the diagnostic and prognostic value of MSLN in MPM patients. Furthermore, MSLN has become an attractive immunotherapy target in MPM, where better treatment strategies are urgently needed. Several MSLN-targeted monoclonal antibodies, antibody-drug conjugates, immunotoxins, cancer vaccines, and cellular therapies have been tested in the clinical setting. The biological rationale underpinning MSLN-targeted immunotherapies and their potential to improve MPM patient outcomes are reviewed.

Eradicating mesothelin-positive human gastric and pancreatic tumors in xenograft models with optimized anti-mesothelin antibody-drug conjugates from synthetic antibody libraries

Mesothelin (MSLN) is an attractive candidate of targeted therapy for several cancers, and hence there are increasing needs to develop MSLN-targeting strategies for cancer therapeutics. Antibody–drug conjugates (ADCs) targeting MSLN have been demonstrated to be a viable strategy in treating MSLN-positive cancers. However, developing antibodies as targeting modules in ADCs for toxic payload delivery to the tumor site but not to normal tissues is not a straightforward task with many potential hurdles. In this work, we established a high throughput engineering platform to develop and optimize anti-MSLN ADCs by characterizing more than 300 scFv CDR-variants and more than 50 IgG CDR-variants of a parent anti-MSLN antibody as candidates for ADCs. The results indicate that only a small portion of the complementarity determining region (CDR) residues are indispensable in the MSLN-specific targeting. Also, the enhancement of the hydrophilicity of the rest of the CDR residues could drastically increase the overall solubility of the optimized anti-MSLN antibodies, and thus substantially improve the efficacies of the ADCs in treating human gastric and pancreatic tumor xenograft models in mice. We demonstrated that the in vivo treatments with the optimized ADCs resulted in almost complete eradication of the xenograft tumors at the treatment endpoints, without detectable off-target toxicity because of the ADCs’ high specificity targeting the cell surface tumor-associated MSLN. The technological platform can be applied to optimize the antibody sequences for more effective targeting modules of ADCs, even when the candidate antibodies are not necessarily feasible for the ADC development due to the antibodies’ inferior solubility or affinity/specificity to the target antigen.

Early administration of amatuximab, a chimeric high-affinity anti-mesothelin monoclonal antibody, suppresses liver metastasis of mesothelin-expressing pancreatic cancer cells and enhances gemcitabine sensitivity in a xenograft mouse model

Amatuximab is a promising therapeutic antibody targeting mesothelin, a 40-kDa glycoprotein that is highly expressed in pancreatic cancer. We investigated the effectiveness of early amatuximab treatment, imitating an adjuvant chemotherapy setting, and combination therapy with amatuximab and gemcitabine in liver metastasis of pancreatic cancer. Liver metastasis mouse models were established in 8-week-old male BALB/c nu/nu mice using the hemisplenic injection method. Tridaily amatuximab monotherapy or combination with gemcitabine was administered to the liver metastasis mouse model before metastatic lesions had formed huge masses. Gaussia luciferase-transfected AsPC-1 was used as a mesothelin-overexpressing pancreatic cancer cell line. The amount of liver metastases and the serum luciferase activity were significantly lower in the treatment groups than those in the control IgG group. Notably, the anti-tumor activity of gemcitabine was synergically enhanced by combination therapy with amatuximab. Furthermore, western blotting revealed that the high expression of phosphorylated c-Met and AKT in liver metastatic lesions treated with gemcitabine monotherapy was canceled by its combination with amatuximab. This result indicated that the observed synergic therapeutic effect may have occurred as a result of the inhibitory effect of amatuximab on the phosphorylation of c-Met and AKT, which were promoted by exposure to GEM. In conclusion, our study revealed that early administration of amatuximab alone or in combination with GEM significantly suppressed the liver metastases of mesothelin-expressing pancreatic cancer cells. A phase II clinical trial of amatuximab as part of an adjuvant chemotherapy regimen for resected pancreatic cancer is expected.

A Novel 89Zr-labeled DDS Device Utilizing Human IgG Variant (scFv): "Lactosome" Nanoparticle-Based Theranostics for PET Imaging and Targeted Therapy

“Theranostics,” a new concept of medical advances featuring a fusion of therapeutic and diagnostic systems, provides promising prospects in personalized medicine, especially cancer. The theranostics system comprises a novel ⁸⁹Zr-labeled drug delivery system (DDS), derived from the novel biodegradable polymeric micelle, “Lactosome” nanoparticles conjugated with specific shortened IgG variant, and aims to successfully deliver therapeutically effective molecules, such as the apoptosis-inducing small interfering RNA (siRNA) intracellularly while offering simultaneous tumor visualization via PET imaging. A 27 kDa-human single chain variable fragment (scFv) of IgG to establish clinically applicable PET imaging and theranostics in cancer medicine was fabricated to target mesothelin (MSLN), a 40 kDa-differentiation-related cell surface glycoprotein antigen, which is frequently and highly expressed by malignant tumors. This system coupled with the cell penetrating peptide (CPP)-modified and photosensitizer (e.g., 5, 10, 15, 20-tetrakis (4-aminophenyl) porphyrin (TPP))-loaded Lactosome particles for photochemical internalized (PCI) driven intracellular siRNA delivery and the combination of 5-aminolevulinic acid (ALA) photodynamic therapy (PDT) offers a promising nano-theranostic-based cancer therapy via its targeted apoptosis-inducing feature. This review focuses on the combined advances in nanotechnology and material sciences utilizing the “⁸⁹Zr-labeled CPP and TPP-loaded Lactosome particles” and future directions based on important milestones and recent developments in this platform.

αPD-1-mesoCAR-T cells partially inhibit the growth of advanced/refractory ovarian cancer in a patient along with daily apatinib

Epithelial ovarian cancer (EOC) is the leading cause of death among gynecological malignancies in China. In particular, advanced/refractory ovarian cancer lacks effective targeted therapies due to the immunosuppressive and proangiogenic tumor microenvironment. Mesothelin (MSLN) has been found to be highly expressive in most EOC. Targeting MSLN by antibodies or chimeric antigen receptor-modified T (CAR-T) cells and immune checkpoint blockades as well as apatinib, an anti-angiogenic drug, have been used in patients with refractory ovarian cancer. Apatinib was reported to promote the infiltration of CD8⁺ T cells in lung cancer. However, the combination therapy of CAR-T secreting anti-PD-1 antibody with apatinib in EOC has not been reported.

CASE PRESENTATION

Here we report a case of refractory EOC in a patient who had relapsed after multiline chemotherapy. The patient received autologous T cells that contained sequences encoding single-chain variable fragments specific for MSLN and full-length antibody for PD-1 (αPD-1). The modified T cells were called αPD-1-mesoCAR-T cells. After infusion, the copy number and PD-1 antibody secretion of the CAR-T cells were increased in the blood. By application of multimodality tumor tracking, MRI of the liver showed shrinkage of metastatic nodules from average diameter of 71.3-39.1 mm at month 2. The patient achieved partial response and survived more than 17 months. IL-6 levels in the patient fluctuated from the baseline to 2-4-folds after treatment, but side effects were mild with only grade 1 hypertension and fatigue.

CONCLUSION

αPD-1-mesoCAR-T cell therapy combined with apatinib demonstrates a potential therapeutic effect on advanced refractory ovarian cancer.

TRIAL REGISTRATION NUMBER

NCT03615313.

Novel mesothelin antibody-drug conjugates: current evidence and future role in the treatment of ovarian cancer

Introduction: Ovarian cancer is the deadliest gynecologic malignancy in the United States, and effective therapies for recurrent, advanced, and progressive disease are limited. Mesothelin is known to be expressed in ovarian cancers, and antibody-drug conjugates targeting mesothelin are a promising novel therapeutic agent.Areas Covered: This article reviews the currently available literature of anti-mesothelin antibody-drug conjugates as a novel treatment for ovarian cancer. Preclinical in vitro and in vivo data as well as clinical results are reviewed for each available agent. Additionally, adverse effects are covered.Expert Opinion: Anti-mesothelin antibody-drug conjugates and their combination with chemotherapeutic agents have undergone phase II trials with encouraging results and demonstrated favorable adverse effect profiles. Phase III data will be necessary to establish its role in ovarian cancer, particularly in recurrent, advanced, or progressive disease.

Ovarian cancer risk score predicts chemo-response and outcome in epithelial ovarian carcinoma patients

OBJECTIVE

Cytoreductive surgery followed by adjuvant chemotherapy is a standard frontline treatment for epithelial ovarian cancer (EOC). We aimed to develop an ovarian cancer risk score (OVRS) based on the expression of 10 ovarian-cancer-related genes to predict the chemoresistance, and outcomes of EOC patients.

METHODS

We designed a case-control study with total 149 EOC women including 75 chemosensitives and 74 chemoresistants. Gene expression was measured using the quantitative real-time polymerase chain reaction. We tested for correlation between the OVRS and chemosensitivity or chemoresistance, disease-free survival (DFS), and overall survival (OS), and validated the OVRS by analyzing patients from the TCGA database.

RESULTS

The chemosensitive group had lower OVRS than the chemoresistant group (5 vs. 15, p≤0.001, Mann-Whitney U test). Patients with disease relapse (13 vs. 5, p<0.001, Mann-Whitney U test) or disease-related death (13.5 vs. 6, p<0.001) had higher OVRS than those without. OVRS ≥10 (hazard ratio=3.29; 95% confidence interval=1.94-5.58; p<0.001) was the only predictor for chemoresistance in multivariate analysis. The median DFS (5 months vs. 24 months) and OS (39 months vs. >60 months) of patients with OVRS ≥10 were significantly shorter than those of patients with OVRS <10). The high OVRS group also had significantly shorter median OS than the low OVRS group in 255 patients in the TCGA database (39 vs. 49 months, p=0.046).

CONCLUSIONS

Specific genes panel can be clinically applied in predicting the chemoresistance and outcome, and decision-making of epithelial ovarian cancer.

Mesothelin Expression in Patients with High-Grade Serous Ovarian Cancer Does Not Predict Clinical Outcome But Correlates with CD11c+ Expression in Tumor

INTRODUCTION

Mesothelin (MSLN) is overexpressed in several tumors including ovarian cancer and is the target of current trials. There is limited and conflicting data on MSLN prognostic impact in ovarian cancer.

METHODS

We performed a retrospective study on patients with high-grade serous ovarian cancer, analyzing MSLN expression by immunohistochemistry and examining the correlation of its expression to overall and progression-free survival. Correlations of expression of MSLN, CD8, and macrophage markers in different tumor compartments were also investigated.

RESULTS

Positive MSLN expression was detected in 55.1% of primary tumors and 51.5% of the metastases. MSLN expression was not correlated with survival. We observed a significant positive correlation (r = 0.34, p = 0.01) between MSLN expression in the metastatic site and CD11c expression in total tumor area and perivascular area in the primary tumor.

CONCLUSION

Our results show that MSLN expression does not correlate with clinical outcome. The impact of the correlation between MSLN and CD11c⁺ cells on immunotherapy outcome should be further explored.

Mesothelin-targeted CAR-T cell therapy for solid tumors

Introduction: Mesothelin (MSLN) is a tumor differentiation antigen normally restricted to the body's mesothelial surfaces, but significantly overexpressed in a broad range of solid tumors. For this reason, MSLN has emerged as an important target for the development of novel immunotherapies. This review focuses on anti-MSLN chimeric antigen receptor (CAR) T cell immunotherapy approaches.Areas covered: A brief overview of MSLN as a therapeutic target and existing anti-MSLN antibody-based drugs and vaccines is provided. A detailed account of anti-MSLN CAR-T cell approaches utilized in preclinical models is presented. Finally, a comprehensive summary of currently ongoing and completed anti-MSLN CAR-T cell clinical trials is discussed.Expert opinion: Initial trials using anti-MSLN CAR-T cells have been safe, but efficacy has been limited. Employing regional routes of delivery, introducing novel modifications leading to enhanced tumor infiltration and persistence, and improved safety profiles and combining anti-MSLN CAR-T cells with standard therapies, could render them more efficacious in the treatment of solid malignancies.

Significance of mesothelin expression in preoperative endoscopic biopsy specimens for colorectal cancer prognosis

Mesothelin (MSLN) is a cell surface glycoprotein that is normally expressed in the mesothelial cells but highly expressed in several malignant tumors, where the high expression is generally associated with poor prognosis. In this work, 512 patients with stage III colorectal cancer (CRC) were examined to ascertain the prognostic value of MSLN expression in preoperative endoscopic biopsy specimens. MSLN expression was evaluated by immunohistochemical staining. The tumor cells were MSLN-positive in 61 of the 512 patients (11.9%). MSLN expression was associated with a shorter disease-specific survival (DSS) period (5-year DSS = 68.7%, P = 0.0008). Besides, by multivariate analysis, MSLN expression was identified to be a marker of poor prognosis by multivariate analysis (P = 0.0033, hazard ratio (HR) = 2.31) as well as macroscopic type (P = 0.047, HR = 1.82) among the factors that can be evaluated preoperatively. MSLN-positive patients had a significantly poorer prognosis regardless of adjuvant chemotherapy administration (P = 0.0081 and P = 0.0018 for surgery alone and chemotherapy, respectively). MSLN-positive patients in the adjuvant chemotherapy group exhibited a significantly lower risk of recurrence when compared with those in the surgery alone group (P = 0.0090). In conclusion, high MSLN expression observed in preoperative endoscopic biopsy specimens of stage III CRC was an independent poor prognostic factor. Preoperative evaluation of MSLN by immunohistochemical staining might be applied to select individuals for intensive preoperative chemotherapy among the stage III CRC patients.

Recycling the Purpose of Old Drugs to Treat Ovarian Cancer

The main challenge in ovarian cancer treatment is the management of recurrences. Facing this scenario, therapy selection is based on multiple factors to define the best treatment sequence. Target therapies, such as bevacizumab and polymerase (PARP) inhibitors, improved patient survival. However, despite their achievements, ovarian cancer survival remains poor; these therapeutic options are highly costly and can be associated with potential side effects. Recently, it has been shown that the combination of repurposed, conventional, chemotherapeutic drugs could be an alternative, presenting good patient outcomes with few side effects and low costs for healthcare institutions. The main aim of this review is to strengthen the importance of repurposed drugs as therapeutic alternatives, and to propose an in vitro model to assess the therapeutic value. Herein, we compiled the current knowledge on the most promising non-oncological drugs for ovarian cancer treatment, focusing on statins, metformin, bisphosphonates, ivermectin, itraconazole, and ritonavir. We discuss the primary drug use, anticancer mechanisms, and applicability in ovarian cancer. Finally, we propose the use of these therapies to perform drug efficacy tests in ovarian cancer ex vivo cultures. This personalized testing approach could be crucial to validate the existing evidences supporting the use of repurposed drugs for ovarian cancer treatment.

SJI 2020 special issue: A catalogue of Ovarian Cancer targets for CAR therapy

Ovarian Cancer (OC) is currently difficult to cure, mainly due to its late detection and the advanced state of the disease at the time of diagnosis. Therefore, conventional treatments such as debulking surgery and combination chemotherapy are rarely able to control progression of the tumour, and relapses are frequent. Alternative therapies are currently being evaluated, including immunotherapy and advanced T cell-based therapy. In the present review, we will focus on a description of those Chimeric Antigen Receptors (CARs) that have been validated in the laboratory or are being tested in the clinic. Numerous target antigens have been defined due to the identification of OC biomarkers, and many are being used as CAR targets. We provide an exhaustive list of these constructs and their current status. Despite being innovative and efficient, the OC-specific CARs face a barrier to their clinical efficacy: the tumour microenvironment (TME). Indeed, effector cells expressing CARs have been shown to be severely inhibited, rendering the CAR T cells useless once at the tumour site. Herein, we give a thorough description of the highly immunosuppressive OC TME and present recent studies and innovations that have enabled CAR T cells to counteract this negative environment and to destroy tumours.

New anti-mesothelin single-domain antibodies and cell models for developing targeted breast cancer therapy

Most triple negative breast cancers (TNBC) are characterized by elevated expression of mesothelin (MSLN), a cell surface antigen and one of the preferred targets for the therapy of solid tumors. Most continuous TNBC cell lines are MSLN-negative, which obstructs the development of MSLN-targeted therapy for TNBC. The aim of this study was to identify TNBC cell lines with MSLN hyperexpression and to obtain single-domain antibodies (nanobodies) capable of recognizing MSLN in TNBC cells. Mesothelin expression levels were measured in the panel of TNBC cell lines by real-time reverse-transcription PCR. PCR results were verified by measuring concentrations of the megakaryocyte potentiating factor (the secreted fragment of the mesothelin precursor) using sandwich ELISA. Immune phage-display VHH fragment libraries were prepared from mononuclear cells of Vicugna pacos using a modified library enrichment protocol. Two nanobody variants with high specificity for the target and Kd of about 140 and 95 nmol, respectively were obtained. Two MSLN+ and three MSLN– cell lines were identified in the TNBC cell lines panel. The nanobodies demonstrated the ability to recognize the target antigen in MSLN+ cells and had the low ability to bind to MSLN– cells. Thus, we found a convenient MSLN+ TNBC cell model for MSLN-targeted therapy testing. The new single-domain antibodies can be used as targeting components of chimeric antigen receptors.

Association of genetic variants in the 3'-untranslated region of the mesothelin (MSLN) gene with ovarian carcinoma

Limited information has been offered regarding the association of mesothelin (MSLN) gene variants at the 3'-untranslated region with the risk of ovarian carcinoma. The primary objective of this work is to assess the impact of the MSLN (rs1057147 and rs57272256) variants on the progression of ovarian carcinoma among Egyptian women. The study was conceived based on 127 women diagnosed with ovarian carcinoma and 106 unrelated cancer-free controls. Genomic DNA of these MSLN variants was genotyped utilizing the PCR technique. The frequencies of the MSLN (rs1057147) variant revealed a significant association with increased risk of ovarian carcinoma under allelic and dominant models (P < .05). Nonetheless, ovarian cancer patients with the MSLN (rs57272256) variant did not attain considerable significance under all genetic models (P > .05). Together, our findings suggested that the MSLN (rs1057147) variant was associated with an increased risk of ovarian carcinoma, but not the MSLN (rs57272256) variant.

Insights Into the Role of Mesothelin as a Diagnostic and Therapeutic Target in Ovarian Carcinoma

Ovarian malignancies remain the leading cause of death in female gynecological tumors. More than 70% of patients are diagnosed with advanced stage with extensive metastatic lesions in abdominal cavity due to lack of symptoms in early stage and sensitive diagnostic approaches. Mesothelin (MSLN), a glycosylphosphatidylinositol-anchored membrane glycoprotein, participates in cell adhesion, tumor progression, metastasis, and drug resistance. Despite this, the mechanism is still poorly understood. The differential expression pattern of MSLN in normal and cancer tissues makes it a promising target for diagnosis and therapeutic applications. Several clinical trials are underway to evaluate the safety and efficacy of MSLN-targeted drugs, including CAR T cells, immunotoxin, antibody-drug conjugates, and vaccine. This review is aimed to briefly discuss the characteristics of MSLN and the latest progress in MSLN targeting therapies.

Role of biomarkers for early detection of ovarian cancer recurrence

Ovarian cancer is frequently diagnosed at an advanced stage and a fraction of these patients fail to respond to primary therapy and relapses in 70% of cases. On account of the high recurrence probability and the poor outcomes after recurrence, there is an urgent need to predict progression as early as possible and thus found the strategies to detect and prevent a recurrence. Considering that biomarkers have contributed to the management of ovarian cancer by distinguishing benign and malignant pelvic masses and monitoring response to treatment, in this review, we aim to discuss the latest evidence reported in the literature about the use of biomarkers to detect OC recurrence. In detail, we summarized all the evidence of the most quoted biomarkers like HE4, osteopontin, mesothelin (MSLN), Folate receptor α (FOLR1), paraneoplastic antigens, miRNA, cancer stem cells (CSCs) and a combination of them to evaluate their role as prognostic biomarkers for ovarian cancer recurrence.

New insight and future perspective of mesothelin-targeted agents in nuclear medicine

Purpose

The aim of this review is to summarize the main applications of mesothelin-targeting agents in the diagnosis of different types of cancers with a brief mention of nuclear magnetic resonance.

Methods

The articles taken into account were selected from PubMed, Scopus, and Web of Sciences, including research articles and abstracts that deal with radioimmunotherapy and new tracers for nuclear medicine and radiodiagnosis. Articles that are not in English have been excluded.

Results

Mesothelin-targeting agents were the subject of the selected articles in which tracers as 64Cu-DOTA-11-25mAb anti MSLN, 111In-MORAb-009-CHX-A″, 89Zr-MMOT0530A, 111In-amatuximab, 99mTc-A1, 89Zr-AMA, 89Zr-amatuximab, 64Cu-amatuximab, 89Zr-labeled MMOT0530A and 89Zr-B3 found application in detection of malignancies that overexpressed mesothelin. Only one article approached magnetic resonance imaging (MRI) diagnosis using superparamagnetic iron oxide nanoparticles linked to anti-mesothelin antibodies. The tracers proved to be highly sensitive in detecting mesothelin positive cells. 89Zr-labeled MMOT0530A could also be used to predict the suitability of patients to radioimmunotherapy.

Conclusions

Radiolabeled anti-mesothelin antibodies could be crucial as a treatment tool and for predicting the eligibility and the response of the patient to radioimmunotherapy through the study of the expression grade of mesothelin. They can be a relevant tool for pancreatic adenocarcinoma, lung cancer, human epidermoid carcinoma, ovarian cancer, malignant mesothelioma in which mesothelin is widely expressed.

Regulation of invasion and peritoneal dissemination of ovarian cancer by mesothelin manipulation

Peritoneal dissemination is a particular form of metastasis typically observed in ovarian cancer and the major cause for poor patient’s outcome. Identification of the molecular players involved in ovarian cancer dissemination can offer an approach to develop treatment strategies to improve clinical prognosis. Here, we identified mesothelin (MSLN) as a crucial protein in the multistep process of peritoneal dissemination of ovarian cancer. We demonstrated that MSLN is overexpressed in primary and matched peritoneal metastasis of high-grade serous carcinomas (HGSC). Using several genetically engineered ovarian cancer cell lines, resulting in loss or gain of function, we found that MSLN increased cell survival in suspension and invasion of tumor cells through the mesothelial cell layer in vitro. Intraperitoneal xenografts established with MSLN^high ovarian cancer cell lines showed enhanced tumor burden and spread within the peritoneal cavity. These findings provide strong evidences that MSLN is a key player in ovarian cancer progression by triggering peritoneal dissemination and provide support for further clinical investigation of MSLN as a therapeutic target in HGSC.

Mesothelin-Targeted Recombinant Immunotoxins for Solid Tumors

Mesothelin (MSLN) is a cell surface glycoprotein normally expressed only on serosal surfaces, and not found in the parenchyma of vital organs. Many solid tumors also express MSLN, including mesothelioma and pancreatic adenocarcinoma. Due to this favorable expression profile, MSLN represents a viable target for directed anti-neoplastic therapies, such as recombinant immunotoxins (iToxs). Pre-clinical testing of MSLN-targeted iTox’s has yielded a strong body of evidence for activity against a number of solid tumors. This has led to multiple clinical trials, testing the safety and efficacy of the clinical leads SS1P and LMB-100. While promising clinical results have been observed, neutralizing anti-drug antibody (ADA) formation presents a major challenge to overcome in the therapeutic development process. Additionally, on-target, off-tumor toxicity from serositis and non-specific capillary leak syndrome (CLS) also limits the dose, and therefore, impact anti-tumor activity. This review summarizes existing pre-clinical and clinical data on MSLN-targeted iTox’s. In addition, we address the potential future directions of research to enhance the activity of these anti-tumor agents.

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.

Mesothelin expression in esophageal adenocarcinoma and squamous cell carcinoma and its possible impact on future treatment strategies

Background

Mesothelin is expressed at very low levels by normal mesothelial cells but is overexpressed in several human cancers. This makes mesothelin a promising target for immunotherapy. Limited data exist about mesothelin expression in esophageal carcinoma. In a current clinical trial, the highly potent anti-mesothelin antibody anetumab ravtansine is used in patients with mesothelin-positive tumors. Response rates are correlated with mesothelin expression (using the Ventana antibody) in tumor cells. No data are available on expression levels using the Ventana antibody. Most data have been generated using the Novocastra antibody. As patients are selected for clinical trials based on antibody staining of tumor samples, a comparison of these two available antibodies is crucial.

Methods

We analyzed 481 esophageal carcinomas [373 esophageal adenocarcinomas (EACs), 108 esophageal squamous cell carcinomas (ESCCs)] using two different monoclonal antibodies (Novocastra and Ventana) for mesothelin expression (low-mid and high-level expression, as used in one clinical trial). We also checked for the correlation of these results with clinical and molecular data.

Results

We revealed different staining results for both antibodies in EACs: Ventana: 53.6% (low expression: 25.3%; high expression: 28.3%) and Novocastra: 35.7% (low expression: 21.2%; high expression 14.5%). In ESCC we found comparable staining results: Ventana: 13.3% (low expression: 9.5%; high expression: 3.8%) and Novocastra: 13% (low expression: 11.1%; high expression: 1.9%). ARID1a-deficient EAC patients demonstrated significantly higher rates of mesothelin-positive tumors than ARID1a intact EAC patients. No correlations were found with other molecular alterations (TP53 mutation, ERBB2 amplification) or survival rates.

Conclusion

To the best of our knowledge, this is the largest study analyzing the importance of mesothelin expression in esophageal carcinoma. This study revealed a significant number of mesothelin-positive esophageal carcinomas, especially adenocarcinomas. New therapeutic targets are urgently required to improve the outcome of patients with locally advanced or metastasized esophageal carcinoma. The inhibition of mesothelin can be a new attractive target.

First-in-Human, Multicenter, Phase I Dose-Escalation and Expansion Study of Anti-Mesothelin Antibody-Drug Conjugate Anetumab Ravtansine in Advanced or Metastatic Solid Tumors

PURPOSE

This phase I study, which to our knowledge is the first-in-human study of this kind, investigates the safety, tolerability, pharmacokinetics, and clinical activity of anetumab ravtansine, an antibody–drug conjugate of anti-mesothelin antibody linked to maytansinoid DM4, in patients with advanced, metastatic, or recurrent solid tumors known to express the tumor-differentiation antigen mesothelin.

PATIENTS AND METHODS

This phase I, open-label, multicenter, dose-escalation and dose-expansion study of anetumab ravtansine enrolled 148 adult patients with multiple solid tumor types. Ten dose-escalation cohorts of patients with advanced or metastatic solid tumors (0.15-7.5 mg/kg) received anetumab ravtansine once every 3 weeks, and 6 expansion cohorts of patients with advanced, recurrent ovarian cancer or malignant mesothelioma received anetumab ravtansine at the maximum tolerated dose once every 3 weeks, 1.8 mg/kg once per week, and 2.2 mg/kg once per week.

RESULTS

Forty-five patients were enrolled across the 10 dose-escalation cohorts. The maximum tolerated dose of anetumab ravtansine was 6.5 mg/kg once every 3 weeks or 2.2 mg/kg once per week. Thirty-two patients were enrolled in the 6.5 mg/kg once-every-3-weeks, 35 in the 1.8 mg/kg once-per-week, and 36 in the 2.2 mg/kg once-per-week expansion cohorts. The most common drug-related adverse events were fatigue, nausea, diarrhea, anorexia, vomiting, peripheral sensory neuropathy, and keratitis/keratopathy. There were no drug-related deaths. Anetumab ravtansine pharmacokinetics were dose proportional; the average half-life was 5.5 days. Among 148 patients with mesothelioma or ovarian, pancreatic, non–small-cell lung, and breast cancers, 1 had a complete response, 11 had partial responses, and 66 had stable disease. High levels of tumor mesothelin expression were detected in patients with clinical activity.

CONCLUSION

Anetumab ravtansine exhibited a manageable safety and favorable pharmacokinetic profile with encouraging preliminary antitumor activity in heavily pretreated patients with mesothelin-expressing solid tumors. The results allowed for the determination of recommended doses, schedules, and patient populations for anetumab ravtansine in phase II studies.

Prognostic significance of mesothelin expression in colorectal cancer disclosed by area-specific four-point tissue microarrays

Mesothelin (MSLN) is a cell surface glycoprotein present in many cancer types. Its expression is generally associated with an unfavorable prognosis. This study examined the prognostic significance of MSLN expression in different areas of individual colorectal cancers (CRCs) using tissue microarrays (TMAs) by enrolling 314 patients with stage II (T3-T4, N0, M0) CRCs. Using formalin-fixed paraffin-embedded tissue blocks from patients, TMA blocks were constructed. Tissue core specimens were obtained from submucosal invasive front (Fr-sm), subserosal invasive front (Fr-ss), central area (Ce), and rolled edge (Ro) of each tumor. Using these four-point TMA sets, MSLN expression was immunohistochemically surveyed. The area-specific prognostic significance of MSLN expression was evaluated. A deep learning convolutional neural network algorithm was used for imaging analysis and evaluating our judgment's objectivity. MSLN staining ratio was positively correlated between the manual and machine-learning analyses (r = 0.71). The correlation coefficient between Ro and Ce, Ro and Fr-sm, and Ro and Fr-ss was r = 0.63, r = 0.54, and r = 0.61, respectively. Disease-specific survival curves for the MSLN-positive and MSLN-negative groups in Fr-sm, Fr-ss, and Ro were significantly different (five-year survival rates 88.1% and 95.5% (P = 0.024), 85.0 and 96.2% (P = 0.0087), 87.8 and 95.5% (P = 0.051), and 77.9 and 95.8% (P = 0.046) for Fr-sm, Fr-ss, Ce, and Ro, respectively). The analysis performed using area-specific four-point TMAs clearly demonstrated that MSLN expression in stage II CRC was relatively homogeneous within tumors. Additionally, high MSLN expression showed or tended to show unfavorable prognostic significance regardless of the tumor area.

Engineered Fn3 protein has targeted therapeutic effect on mesothelin-expressing cancer cells and increases tumor cell sensitivity to chemotherapy

Mesothelin is a protein expressed at high levels on the cell surface in a variety of cancers, with limited expression in healthy tissues. The presence of mesothelin on tumor tissue correlates with increased invasion and metastasis, and resistance to traditional chemotherapies, through mechanisms that remain poorly understood. Molecules that specifically recognize mesothelin and interrupt its contribution to tumor progression have significant potential for targeted therapy and targeted drug delivery applications. A number of mesothelin-targeting therapies are in preclinical and clinical development, although none are currently approved for routine clinical use. In this work, we report the development of a mesothelin-targeting protein based on the fibronectin type-III non-antibody protein scaffold, which offers opportunities for applications where antibodies have limitations. We engineered protein variants that bind mesothelin with high affinity and selectively initiate apoptosis in tumor cells expressing mesothelin. Interestingly, apoptosis does not occur through a caspase-mediated pathway and does not require downregulation of cell-surface mesothelin, suggesting a currently unknown pathway through which mesothelin contributes to cancer progression. Importantly, simultaneous treatment with mesothelin-binding protein and chemotherapeutic mitomycin C had a greater cytotoxic effect on mesothelin-positive cells compared to either molecule alone, underscoring the potential for combination therapy including biologics targeting mesothelin.

CD4 T cells target colorectal cancer antigens upregulated by oxaliplatin

Immune checkpoint blockade has proven its efficacy in hypermutated subtypes of metastatic colorectal cancers (mCRC). Immunogenic potential can also be observed with conventional chemotherapies, but this property has never been explored thoroughly in CRC patients. The CRC therapeutic arsenal includes oxaliplatin, a well-characterized platinum drug already described as immunogenic. Here, we investigated the impact of the oxaliplatin-based treatment on mCRC immunopeptidome. We demonstrated that oxaliplatin-resistant CRC cell lines overexpressed telomerase reverse transcriptase (TERT), colorectal-associated-tumor antigen-1 (COA-1) and mesothelin tumor-associated antigens. We identified new HLA class-II-restricted and promiscuous peptides derived from COA-1 and mesothelin. The two naturally processed peptides COA-1_331-345 and Meso_366-380 appear to be the most immunogenic in mCRC patients. A prospective cohort of 162 mCRC patients enabled us to explore the impact of oxaliplatin exposure on the antitumor-specific immune response. Interestingly, chemotherapy-naive mCRC patients present high immune CD4 T-cell responses directed against TERT, COA-1 and mesothelin-derived peptides. These antitumor T-cell responses were maintained after 3 months of oxaliplatin-based treatment. Altogether, these findings highlight the interest of immunostimulatory agents to improve the management of chemoresistant mCRC patients. Finally, the high frequency of immune responses targeting the new immunogenic peptides derived from COA-1 and mesothelin support their use in immunomonitoring strategies.