Intracellular localization of mesothelin predicts patient prognosis of extrahepatic bile duct cancer

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.

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.

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.

Mesothelin is a novel cell surface disease marker and potential therapeutic target in acute myeloid leukemia

In an effort to identify acute myeloid leukemia (AML)-restricted targets for therapeutic development in AML, we analyzed the transcriptomes of 2051 children and young adults with AML and compared the expression profile with normal marrow specimens. This analysis identified a large cohort of AML-restricted genes with high expression in AML, but low to no expression in normal hematopoiesis. Mesothelin (MSLN), a known therapeutic target in solid tumors, was shown to be highly overexpressed in 36% of the AML cohort (range, 5-1077.6 transcripts per million [TPM]) and virtually absent in normal marrow (range, 0.1-10.7 TPM). We verified MSLN transcript expression by quantitative reverse transcription polymerase chain reaction, confirmed cell surface protein expression on leukemic blasts by multidimensional flow cytometry, and demonstrated that MSLN expression was associated with promoter hypomethylation. MSLN was highly expressed in patients with KMT2A rearrangements (P < .001), core-binding factor fusions [inv(16)/t(16;16), P < .001; t(8;21), P < .001], and extramedullary disease (P = .001). We also demonstrated the presence of soluble MSLN in diagnostic serum specimens using an MSLN-directed enzyme-linked immunosorbent assay. In vitro and in vivo preclinical efficacy of the MSLN-directed antibody-drug conjugates (ADCs) anetumab ravtansine and anti-MSLN-DGN462 were evaluated in MSLN+ leukemia cell lines in vitro and in vivo, as well as in patient-derived xenografts. Treatment with ADCs resulted in potent target-dependent cytotoxicity in MSLN+ AML. In this study, we demonstrate that MSLN is expressed in a significant proportion of patients with AML and holds significant promise as a diagnostic and therapeutic target in AML, and that MSLN-directed therapeutic strategies, including ADCs, warrant further clinical investigation.

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.

Mesothelin Expression in Human Tumors: A Tissue Microarray Study on 12,679 Tumors

Mesothelin (MSLN) represents an attractive molecule for targeted cancer therapies. To identify tumors that might benefit from such therapies, tissue microarrays including 15,050 tumors from 122 different tumor types and 76 healthy organs were analyzed for MSLN expression by immunohistochemistry. Sixty-six (54%) tumor types showed at least occasional weak staining, including 50 (41%) tumor types with at least one strongly positive sample. Highest prevalence of MSLN positivity had ovarian carcinomas (serous 97%, clear cell 83%, endometrioid 77%, mucinous 71%, carcinosarcoma 65%), pancreatic adenocarcinoma (ductal 75%, ampullary 81%), endometrial carcinomas (clear cell 71%, serous 57%, carcinosarcoma 50%, endometrioid 45%), malignant mesothelioma (69%), and adenocarcinoma of the lung (55%). MSLN was rare in cancers of the breast (7% of 1138), kidney (7% of 807), thyroid gland (1% of 638), soft tissues (0.3% of 931), and prostate (0 of 481). High expression was linked to advanced pathological tumor (pT) stage (p < 0.0001) and metastasis (p < 0.0001) in 1619 colorectal adenocarcinomas, but unrelated to parameters of malignancy in 1072 breast-, 386 ovarian-, 174 lung-, 757 kidney-, 171 endometrial-, 373 gastric-, and 925 bladder carcinomas. In summary, numerous important cancer types with high-level MSLN expression might benefit from future anti-MSLN therapies, but MSLN’s prognostic relevance appears to be limited.

Different role of MSLN and CA125 co-expression as a prognostic predictor between perihilar and distal bile duct carcinoma

Recent studies have suggested that the interaction of mesothelin (MSLN) and cancer antigen 125 (CA125) enhances tumor metastases. The aim of the present study was to clarify the impact of MSLN and CA125 co-expression on the prognosis of patients with extrahepatic bile duct carcinoma (BDC). Tissue samples from patients who underwent surgical resection between 2007 and 2015 for perihilar or distal BDC were immunohistochemically examined. The expression levels of MSLN and CA125 in tumor cells were analyzed. The expression in <50% and ≥50% of the total tumor cells were defined as low- and high-level expression, respectively. Tissue samples were obtained from 31 patients with perihilar BDC and 43 patients with distal BDC. Lymph node metastases were associated with MSLN and CA125 co-expression in patients with perihilar BDC (P=0.002), while there was no association between lymph node metastasis and co-expression in patients with distal BDC (P=0.362). MSLN and CA125 co-expression was associated with a worse overall survival rate in patients with perihilar BDC (5-year overall survival rate, co-expression positive vs. negative, 24 vs. 63%; P=0.038). To the best of our knowledge, the present study is the first to report an association between co-expression of MSLN and CA125 with a poor prognosis in patients with perihilar BDC. The current findings suggested that the significance of co-expression differed according to the BDC location.

Mesothelin blockage by Amatuximab suppresses cell invasiveness, enhances gemcitabine sensitivity and regulates cancer cell stemness in mesothelin-positive pancreatic cancer cells

BACKGROUND

Mesothelin is a 40-kDa glycoprotein that is highly overexpressed in various types of cancers, however molecular mechanism of mesothelin has not been well-known. Amatuximab is a chimeric monoclonal IgG1/k antibody targeting mesothelin. We recently demonstrated that the combine therapy of Amatuximab and gemcitabine was effective for peritonitis of pancreatic cancer in mouse model.

METHODS

We discover the role and potential mechanism of mesothelin blockage by Amatuximab in human pancreatic cells both expressing high or low level of mesothelin in vitro experiment and peritonitis mouse model of pancreatic cancer.

RESULTS

Mesothelin blockage by Amatuximab lead to suppression of invasiveness and migration capacity in AsPC-1 and Capan-2 (high mesothelin expression) and reduce levels of pMET expression. The combination of Amatuximab and gemcitabine suppressed proliferation of AsPC-1 and Capan-2 more strongly than gemcitabine alone. These phenomena were not observed in Panc-1 and MIA Paca-2 (Mesothelin low expression). We previously demonstrated that Amatuximab reduced the peritoneal mass in mouse AsPC-1 peritonitis model and induced sherbet-like cancer cell aggregates, which were vanished by gemcitabine. In this study, we showed that the cancer stem cell related molecule such as ALDH1, CD44, c-MET, as well as proliferation related molecules, were suppressed in sherbet-like aggregates, but once sherbet-like aggregates attached to peritoneum, they expressed these molecules strongly without the morphological changes.

CONCLUSIONS

Our work suggested that Amatuximab inhibits the adhesion of cancer cells to peritoneum and suppresses the stemness and viability of those, that lead to enhance the sensitivity for gemcitabine.

Targeted therapies for extrahepatic cholangiocarcinoma: preclinical and clinical development and prospects for the clinic

Introduction: Until recently, cholangiocarcinoma (CCA) was a largely overlooked disease, and among CCAs, extrahepatic CCA (eCCA) was even more neglected. Despite the growing impact of molecularly targeted therapies and immunotherapy, prognosis of eCCA is dismal. Therefore, unraveling the complex molecular landscape of eCCA has become an urgent need. Deep phenotyping studies have revealed that eCCA is a heterogeneous tumor, harboring specific alterations categorizable into four classes, 'Mesenchymal', 'Proliferation', 'Immune', 'Metabolic'. Molecular alterations convey the activation of several pro-oncogenic pathways, where either actionable drivers or outcome predictors can be identified.Areas covered: We offer insights on perturbed pathways, molecular profiling, and actionable targets in eCCA and present a perspective on the potential stepping-stones to future progress. A systematic literature search in PubMed/ClinicalTrials.gov websites was performed by authors from different disciplines according to their specific topic knowledge to identify the newest and most relevant advances in precision medicine of eCCA.Expert opinion: eCCA is a distinct entity with unique features in terms of molecular classes, oncogenic drivers, and tumor microenvironment. Since more prevalent mutations are currently undruggable, and immunotherapy can be offered only to a minority of patients, international collaborations are instrumental to improve the understanding of the molecular underpins of this disease.

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.

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.

Membrane mesothelin expression positivity is associated with poor clinical outcome of luminal-type breast cancer

Mesothelin is expressed in various types of malignant tumors. The present study immunohistochemically investigated mesothelin expression and its clinicopathological significance in each subtype of breast cancer, with special reference to its cellular localization, in particular, membrane mesothelin expression. Using tissue specimens from 482 patients with breast cancer, immunohistochemistry was used to study mesothelin expression and help classify its localization as membrane or cytoplasmic expression. Mesothelin expression was detected in 77 (16.0%) cases and was the highest in triple-negative breast cancer (31/75; 41.3%), followed by human epithelial growth factor receptor type 2 type (6/33, 18.2%) and luminal type (36/374; 9.6%). Among the 482 cases, membrane mesothelin expression was detected in 73 cases and was significantly associated with a negative hormone receptor status, higher Ki-67 labeling index, nuclear grade 3 and a lower relapse-free survival rate. Cytoplasmic mesothelin expression was not significantly associated with a lower relapse-free survival rate (P=0.058). In the 343 cases of luminal type, the membrane mesothelin expression-positive group had significantly worse prognosis than the membrane mesothelin-expression-negative group (P=0.042). There was no significant difference in the relapse-free survival rate according to the membrane mesothelin expression status in the triple-negative type and other types. It was suggested that membrane mesothelin expression in luminal type breast cancer is associated with a lower rate of relapse-free survival.

Prevalence of DLL3, CTLA-4 and MSTN Expression in Patients with Small Cell Lung Cancer

Introduction

Immune-based and antibody-drug conjugate therapies have shown promise in the treatment of patients with small cell lung cancer (SCLC). However, better predictive biomarkers are needed for selection of the appropriate SCLC patients for these advanced therapies and also for evaluation of the efficacy of these treatments.

Objective

The aim of this study was to examine the expression of delta-like protein 3 (DLL3), cytotoxic T lymphocyte-associated protein 4 (CTLA-4), and mesothelin (MSTN) in patients with SCLC and compare them with those patients’ clinical characteristics.

Methods

Immunohistochemical analyses of DLL3, CTLA-4 and MSTN expression were performed in 38 samples from patients with SCLC.

Results

We found that positive expression in patients of the biomarkers was as follows: for DLL3, 100% (38/38), for CTLA-4, 89.5% (36/38) and for MSTN 81.5% (31/38). The median survival time was 17.9 months in the DLL3 high expression group and 23 months in the DLL3 low expression group. Patients with a high expression of DLL3 showed a poorer prognosis than those with a low expression of DLL3 (HR=3.4; 95% CI, 1.34–8.6; p=0.01).

Conclusion

The expression of DLL3, CTLA-4 and MSTN was not correlated with patients’ age, sex, smoking status, stage, and tumor metastasis. The fact that there was a higher expression of DLL3, CTLA-4, and MSTN in SCLC suggested that these molecules could be used as predictive biomarkers for SCLC.

Mesothelin as a biomarker for targeted therapy

CAR-T cell therapy targeting CD19 has achieved remarkable success in the treatment of B cell malignancies, while various solid malignancies are still refractory for lack of suitable target. In recent years, a large number of studies have sought to find suitable targets with low “on target, off tumor” concern for the treatment of solid tumors. Mesothelin (MSLN), a tumor-associated antigen broadly overexpressed on various malignant tumor cells, while its expression is generally limited to normal mesothelial cells, is an attractive candidate for targeted therapy. Strategies targeting MSLN, including antibody-based drugs, vaccines and CAR-T therapies, have been assessed in a large number of preclinical investigations and clinical trials. In particular, the development of CAR-T therapy has shown great promise as a treatment for various types of cancers. The safety, efficacy, doses, and pharmacokinetics of relevant strategies have been evaluated in many clinical trials. This review is intended to provide a brief overview of the characteristics of mesothelin and the development of strategies targeting MSLN for solid tumors. Further, we discussed the challenges and proposed potential strategies to improve the efficacy of MSLN targeted immunotherapy.

Mesothelin expression and its prognostic role according to microsatellite instability status in colorectal adenocarcinoma

The cell-surface glycoprotein, mesothelin, is normally present on mesothelial cells. Overexpression of mesothelin has been reported in many tumors and is correlated with poor outcome. We investigated the clinicopathologic significance of mesothelin expression in colorectal adenocarcinoma with microsatellites instability (MSI) status.Mesothelin expression was evaluated immunohistochemically in tissue microarray blocks from 390 colorectal adenocarcinoma samples. Mesothelin expression was interpreted according to the intensity and extent. A score of 2 was considered high expression. We analyzed the correlation between mesothelin expression and clinicopathologic characteristics.High mesothelin expression was observed in 177 (45.4%) out of 390 colorectal adenocarcinoma samples and was significantly associated with high histologic grade (P = .037), lymphatic invasion (P = .028), lymph node metastasis (P = .028), and high AJCC stage (P = .026). Kaplan-Meier survival curves revealed no significant difference between patients with high mesothelin expression and patients with low mesothelin expression in both recurrence-free survival (RFS) and cancer-specific survival (P = .609 and P = .167, respectively). In subgroup survival analyses, high mesothelin expression was associated with poor RFS in the MSI-High group of colorectal adenocarcinoma (P = .004).High mesothelin expression was significantly associated with aggressive phenotypes and poor patient outcome in MSI-High colorectal adenocarcinoma.

Role of Ancillary Techniques in Biliary Cytopathology Specimens

Biliary brushing cytology has become the standard of practice for the investigation of strictures of the biliary and pancreatic duct systems. The methodology however has a limitation in that it has low diagnostic sensitivity when only cytologic evaluation is used. A number of testing methodologies have been applied to brushing specimens in an attempt to improve overall sensitivity without loss of specificity. These have included DNA ploidy analysis, immunocytochemistry, individual gene mutational analysis, fluorescence in-situ hybridization (FISH), and next generation sequencing (NGS). Currently, FISH coupled with routine cytology appears to be the method of choice for improving diagnostic sensitivity. NGS shows significant promise for improvement of diagnostic sensitivity.

Extending resectability of hilar cholangiocarcinomas: how can it be assessed and improved?

Until the 1980's, Klatskin tumors were considered 'desperate cases' and most of them were not resected; almost no oncologic concept was available. After many improvements, today, extended hepatectomy, including caudate lobe resection and lymphoadenectomy, have become a standard of care for oncologicaly radical resection of Klatskin tumors. Portal vein en bloc resection, if necessary, is a diffused standard assuring R0-resection without any improvement of survival in most series. Arterial resection remains episodical and controversial in its oncologic impact. Arterial resection-reconstruction was demonstrated to be feasible with many different technical possibilities. Neoadjuvant chemotherapy, refinement of associating liver partition and portal vein ligation for staged hepatectomy and liver transplantations are some possible future resources for treatment of those aggressive tumors that could be able to expand the pool of treatable patients.

Progress in molecular targeted therapy of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma is an uncommon malignant tumor with a poor prognosis due to an incomplete understanding of its molecular pathogenesis and a lack of effective treatment. Precision medical planning and cancer genomics can help to understand the molecular pathogenesis of cancer and identify potential therapeutic targets. With the deepening of basic and clinical research, accurate targeted therapy will be able to improve the prognosis and overall survival of patients with intrahepatic cholangiocarcinoma.

Chimeric antigen receptor T cell therapy in pancreatic cancer: from research to practice

Chimeric antigen receptor (CAR) T cell therapy is genetically engineered tumor antigen-specific anticancer immunotherapy, which after showing great success in hematological malignancies is currently being tried in advanced solid tumors like pancreatic cancer. Immunosuppressive tumor microenvironment and dense fibrous stroma are some of the limitation in the success of this novel therapy. However, genetic modifications and combination therapy is the topic of the research to improve its efficacy. In this article, we summarize the current state of knowledge, limitations, and future prospects for CAR T cell therapy in pancreatic cancer.

Cholangiocarcinoma - evolving concepts and therapeutic strategies

Cholangiocarcinoma is a disease entity comprising diverse epithelial tumours with features of cholangiocyte differentiation: cholangiocarcinomas are categorized according to anatomical location as intrahepatic (iCCA), perihilar (pCCA), or distal (dCCA). Each subtype has a distinct epidemiology, biology, prognosis, and strategy for clinical management. The incidence of cholangiocarcinoma, particularly iCCA, has increased globally over the past few decades. Surgical resection remains the mainstay of potentially curative treatment for all three disease subtypes, whereas liver transplantation after neoadjuvant chemoradiation is restricted to a subset of patients with early stage pCCA. For patients with advanced-stage or unresectable disease, locoregional and systemic chemotherapeutics are the primary treatment options. Improvements in external-beam radiation therapy have facilitated the treatment of cholangiocarcinoma. Moreover, advances in comprehensive whole-exome and transcriptome sequencing have defined the genetic landscape of each cholangiocarcinoma subtype. Accordingly, promising molecular targets for precision medicine have been identified, and are being evaluated in clinical trials, including those exploring immunotherapy. Biomarker-driven trials, in which patients are stratified according to anatomical cholangiocarcinoma subtype and genetic aberrations, will be essential in the development of targeted therapies. Targeting the rich tumour stroma of cholangiocarcinoma in conjunction with targeted therapies might also be useful. Herein, we review the evolving developments in the epidemiology, pathogenesis, and management of cholangiocarcinoma.

Overexpression of periostin and distinct mesothelin forms predict malignant progression in a rat cholangiocarcinoma model

Periostin and mesothelin have each been suggested to be predictors of poor survival for patients with intrahepatic cholangiocarcinoma, although the clinical prognostic value of both of these biomarkers remains uncertain. The aim of the current study was to investigate these biomarkers for their potential to act as tumor progression factors when assessed in orthotopic tumor and three-dimensional culture models of rat cholangiocarcinoma progression. Using our orthotopic model, we demonstrated a strong positive correlation between tumor and serum periostin and mesothelin and increasing liver tumor mass and associated peritoneal metastases that also reflected differences in cholangiocarcinoma cell aggressiveness and malignant grade. Periostin immunostaining was most prominent in the desmoplastic stroma of larger sized more aggressive liver tumors and peritoneal metastases. In comparison, mesothelin was more highly expressed in the cholangiocarcinoma cells; the slower growing more highly differentiated liver tumors exhibited a luminal cancer cell surface immunostaining for this biomarker, and the rapidly growing less differentiated liver and metastatic tumor masses largely showed cytoplasmic mesothelin immunoreactivity. Two molecular weight forms of mesothelin were identified, one at ∼40 kDa and the other, a more heavily glycosylated form, at ∼50 kDa. Increased expression of the 40-kDa mesothelin over that of the 50 kDa form predicted increased malignant progression in both the orthotopic liver tumors and in cholangiocarcinoma cells of different malignant potential in three-dimensional culture. Moreover, coculturing of cancer-associated myofibroblasts with cholangiocarcinoma cells promoted overexpression of the 40-kDa mesothelin, which correlated with enhanced malignant progression in vitro. Conclusion: Periostin and mesothelin are useful predictors of tumor progression in our rat desmoplastic cholangiocarcinoma models. This supports their relevance to human intrahepatic cholangiocarcinoma. (Hepatology Communications 2018;2:155-172).

Liver myofibroblasts of murine origins express mesothelin: Identification of novel rat mesothelin splice variants

Liver myofibroblasts are specialized effector cells that drive hepatic fibrosis, a hallmark process of chronic liver diseases, leading to progressive scar formation and organ failure. Liver myofibroblasts are increasingly recognized as heterogeneous with regards to their origin, phenotype, and functions. For instance, liver myofibroblasts express cell markers that are universally represented such as, ItgαV and Pdgfrβ, or restricted to a given subpopulation such as, Lrat exclusively expressed in hepatic stellate cells, and Gpm6a in mesothelial cells. To study liver myofibroblasts in vitro, we have previously generated and characterized a SV40-immortalized polyclonal rat activated portal fibroblast cell line called RGF-N2 expressing multiple mesothelin mRNA transcripts. Mesothelin, a cell-surface molecule expressed in normal mesothelial cells and overexpressed in several cancers such as, mesothelioma and cholangiocarcinoma, was recently identified as a key regulator of portal myofibroblast proliferation, and fibrosis progression in the setting of chronic cholestatic liver disease. Here, we identify novel mesothelin splice variants expressed in rat activated portal fibroblasts. RGF-N2 portal fibroblast cDNA was used as template for insertion of hemagglutinin tag consensus sequence into the complete open reading frame of rat mesothelin variant coding sequences by extension PCR. Purified amplicons were subsequently cloned into an expression vector for in vitro translation and transfection in monkey COS7 fibroblasts, before characterization of fusion proteins by immunoblot and immunofluorescence. We show that rat activated portal fibroblasts, hepatic stellate cells, and cholangiocarcinoma cells express wild-type mesothelin and additional splice variants, while mouse activated hepatic stellate cells appear to only express wild-type mesothelin. Notably, rat mesothelin splice variants differ from the wild-type isoform by their protein properties and cellular distribution in transfected COS7 fibroblasts. We conclude that mesothelin is a marker of activated murine liver myofibroblasts. Mesothelin gene expression and regulation may be critical in liver myofibroblasts functions and fibrosis progression.

Emerging molecular therapeutic targets for cholangiocarcinoma

Cholangiocarcinomas (CCAs) are diverse epithelial tumors arising from the liver or large bile ducts with features of cholangiocyte differentiation. CCAs are classified anatomically into intrahepatic (iCCA), perihilar (pCCA), and distal CCA (dCCA). Each subtype has distinct risk factors, molecular pathogenesis, therapeutic options, and prognosis. CCA is an aggressive malignancy with a poor overall prognosis and median survival of less than 2years in patients with advanced disease. Potentially curative surgical treatment options are limited to the subset of patients with early-stage disease. Presently, the available systemic medical therapies for advanced or metastatic CCA have limited therapeutic efficacy. Molecular alterations define the differences in biological behavior of each CCA subtype. Recent comprehensive genetic analysis has better characterized the genomic and transcriptomic landscape of each CCA subtype. Promising candidates for targeted, personalized therapy have emerged, including potential driver fibroblast growth factor receptor (FGFR) gene fusions and somatic mutations in isocitrate dehydrogenase (IDH)1/2 in iCCA, protein kinase cAMP-activated catalytic subunit alpha (PRKACA) or beta (PRKACB) gene fusions in pCCA, and ELF3 mutations in dCCA/ampullary carcinoma. A precision genomic medicine approach is dependent on an enhanced understanding of driver mutations in each subtype and stratification of patients according to their genetic drivers. We review the current genomic landscape of CCA, the potentially actionable molecular aberrations in each CCA subtype, and the role of immunotherapy in CCA.

Overcoming barriers of car T-cell therapy in patients with mesothelin-expressing cancers

One obstacle to the application of immunotherapy to solid malignancies is to overcome the existing tolerance to self-antigens. Vaccine strategies aimed at harnessing endogenous antitumor T cells are limited by the T-cell receptor repertoire, which can be detected within the thymus as central tolerance or rendered nonfunctional by post-thymic mechanisms of peripheral tolerance. Adoptive immunotherapy can overcome these obstacles, since therapeutically effective T cells can be engineered to recognize tumors. Continued advancements in novel treatments, including immunotherapy, in solid malignancies are imperative. While mesothelin is an attractive target for cancer immunotherapy given its normal expression is limited to mesothelial cells, the breakthrough for chimeric antigen receptor T-cell treatment against this antigen is still forthcoming.

Mesothelin-targeting chimeric antigen receptor-modified T cells by piggyBac transposon system suppress the growth of bile duct carcinoma

Chimeric antigen receptor modified T cell-based immunotherapy is revolutionizing the field of cancer treatment. However, its potential in treating bile duct carcinoma has not been fully explored. Herein, we developed the second-generation mesothelin-targeting chimeric antigen receptor-modified T cells with the 4-1BB co-stimulatory module by the piggyBac transposon system. Mesothelin-targeting chimeric antigen receptor was expressed by 66.0% of mesothelin-targeting chimeric antigen receptor-modified T cells post electrophoretic transfection and stimulation with K562-meso cells; the expressions of activation markers were tested by flow cytometry assay and showed greater activation of mesothelin-targeting chimeric antigen receptor-modified T cells than control T cells (CD107α: 71.9% vs 48.6%; CD27: 92.1% vs 61.8%; CD137: 55.5% vs 8.4%; CD28: 98.0% vs 82.1%; CD134: 37.5% vs 10.4%). Furthermore, mesothelin-targeting chimeric antigen receptor-modified T cells exerted cytotoxicity toward mesothelin-expressing EH-CA1b and EH-CA1a cells in an effector-to-target ratio-dependent manner, while leaving mesothelin-negative GSC-SD and EH-GB1 cells and normal liver L02 cells almost unharmed. Mesothelin-targeting chimeric antigen receptor-modified T cells secreted cytokines at higher levels when co-cultured with mesothelin-positive EH-CA1a and EH-CA1b cells than with mesothelin-negative GSC-SD and EH-GB1 cells. Enhanced cytotoxicity and cytokine secretion of mesothelin-targeting chimeric antigen receptor-modified T cells compared to control T cells were also observed when co-cultured with 293-meso cells (interferon γ: 85.1% ± 1.47% vs 8.3% ± 2.50%, p = 0.000; tumor necrosis factor α: 90.9% ± 4.67% vs 18.5% ± 3.62%, p = 0.0004; interleukin 2: 60.8% ± 2.00% vs 15.6% ± 2.06%, p = 0.002; interleukin 6: 6.4% ± 2.95% vs 1.7% ± 0.63%, p = 0.055). In addition, mesothelin-targeting chimeric antigen receptor-modified T cells showed greater inhibitory and proliferative capability than control T cells within EH-CA1a cell xenografts. This study shows the potential of mesothelin-targeting chimeric antigen receptor-modified T cells in treating bile duct carcinoma.

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.

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.

Functional genomic mRNA profiling of a large cancer data base demonstrates mesothelin overexpression in a broad range of tumor types

The membrane bound glycoprotein mesothelin (MSLN) is a highly specific tumor marker, which is currently exploited as target for drugs. There are only limited data available on MSLN expression by human tumors. Therefore we determined overexpression of MSLN across different tumor types with Functional Genomic mRNA (FGM) profiling of a large cancer database. Results were compared with data in articles reporting immunohistochemical (IHC) MSLN tumor expression. FGM profiling is a technique that allows prediction of biologically relevant overexpression of proteins from a robust data set of mRNA microarrays. This technique was used in a database comprising 19,746 tumors to identify for 41 tumor types the percentage of samples with an overexpression of MSLN compared to a normal background. A literature search was performed to compare the FGM profiling data with studies reporting IHC MSLN tumor expression. FGM profiling showed MSLN overexpression in gastrointestinal (12–36%) and gynecological tumors (20–66%), non-small cell lung cancer (21%) and synovial sarcomas (30%). The overexpression found in thyroid cancers (5%) and renal cell cancers (10%) was not yet reported with IHC analyses. We observed that MSLN amplification rate within esophageal cancer depends on the histotype (31% for adenocarcinomas versus 3% for squamous-cell carcinomas). Subset analysis in breast cancer showed MSLN amplification rates of 28% in triple-negative breast cancer (TNBC) and 33% in basal-like breast cancer. Further subtype analysis of TNBCs showed the highest amplification rate (42%) in the basal-like 1 subtype and the lowest amplification rate (9%) in the luminal androgen receptor subtype.

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.

Diagnostic value of IMP3 and mesothelin in differentiating pancreatic ductal adenocarcinoma from chronic pancreatitis

BACKGROUND

The discrimination between pancreatic ductal adenocarcinoma (PDA) and chronic pancreatitis may be confusing at both clinical and radiologic levels. So, the search for biomarkers able to distinguish both clinical conditions is of great interest.

AIM

This study was undertaken to assess the value of insulin-like growth factor II mRNA binding protein 3 (IMP3) and mesothelin to differentiate PDA from non-neoplastic/reactive pancreatic duct epithelium.

METHODS

Immunohistochemical staining for IMP3 and mesothelin was performed on 40 formalin-fixed, paraffin-embedded tissue sections of PDA, 20 biopsies of chronic pancreatitis and 10 normal pancreatic tissue obtained from tumor-free surgical margins. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy were calculated.

RESULTS

IMP3 immunoreactivity was observed in 34 of 40 (85%) cases of PDA. The staining reaction was moderate to strong in 30 (75%) cases and diffuse in 26 (65%) cases. Eighteen of 20 (90%) biopsies of chronic pancreatitis were negative for IMP3, while the other two cases (10%) showed weak and focal IMP3 immunoreactivity. On the other hand, mesothelin demonstrated positive immunoreactivity in 30 of 40 (75%) cases of PDA. The staining reaction was moderate to strong in 24 (60%) cases and diffuse in 22 (55%) cases. Sixteen of 20 (80%) biopsies of chronic pancreatitis were negative for mesothelin, while weak and focal mesothelin staining was detected in the other 4 cases. All normal pancreatic tissues were negative for IMP3 and mesothelin expression. IMP3 showed higher sensitivity (85%) and specificity (90%) than mesothelin (75% and 80%, respectively).

CONCLUSIONS

Our results showed that IMP3 immunostaining has a higher sensitivity and specificity than mesothelin for the diagnosis of PDA. IMP3 and mesothelin may be useful markers in distinguishing neoplastic from reactive lesions of the pancreas in instances where this is impossible by morphology alone in surgical pathology practice.

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.

Importance of luminal membrane mesothelin expression in intraductal papillary mucinous neoplasms

The present study demonstrated that luminal membrane mesothelin expression is a reliable prognostic factor in gastric cancer. Intraductal papillary mucinous neoplasms (IPMNs) often exhibit a spectrum of dysplasia, ranging between adenoma and carcinoma. Therefore, an immunohistochemical analysis of mesothelin expression in IPMN was performed in the present study, focusing on the localization of mesothelin. IPMNs were classified into two groups, IPMNs associated with invasive carcinoma and low-high (L-H) grade dysplasias. The tumors were classified as mesothelin-positive or -negative and in the mesothelin-positive cases, the localization of mesothelin was evaluated as luminal membrane- or cytoplasmic-positive. Among the 37 IPMNs, mesothelin expression was observed in 21 samples (56.8%), including 46.2% (12 out of 26) of the L-H dysplasia and 81.8% (9 out of 11) of the invasive carcinoma samples (P=0.071). Luminal membrane localization was observed in 10 samples (27%), including 15.4% (4/26) of the L-H dysplasia samples and 54.5% (6 out of 11) of the invasive carcinoma samples (P=0.022). Six patients experienced post-operative recurrence, with five of the recurrent tumors exhibiting mesothelin expression and all six exhibiting luminal membrane localization. It was concluded that immunohistochemical examinations for mesothelin expression and localization are clinically useful for prognostic assessments and decision making regarding further treatment subsequent to surgical procedures in patients with IPMN.

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.

Mesothelin expression is associated with poor outcomes in breast cancer

Mesothelin is a potential therapeutic target and prognostic marker in breast cancer. However, results on its prognostic value in breast cancer have been equivocal and warranted further evaluation. We analyzed clinical data from two breast cancer patient cohorts comprising of 141 patients treated at our institution (discovery cohort) and 844 patients from The Cancer Genome Atlas (TCGA) (validation cohort). Mesothelin expression was quantified by immunohistochemistry or by RNA transcript levels as measured by whole-transcriptome sequencing in the discovery and validation cohorts respectively. Univariate analyses of data from the discovery cohort demonstrated that tumor size [hazard ratio (HR) = 1.30, 95 % confidence interval (CI) 1.11-1.51], positive (+) axillary lymph nodes (HR = 3.34; 95 % CI 1.51-7.39), and mesothelin expression (HR = 2.03; 95 % CI 1.10-3.74) were associated with disease-specific survival. Multivariate analyses demonstrated that mesothelin expression was significantly associated with worse survival (HR = 3.06, 95 % CI 1.40-6.68) after adjusting for (+) axillary lymph nodes and tumor size. Using TCGA cohort as validation dataset, mesothelin-expressing tumors were indeed significantly associated with worse overall survival with HR = 1.46; 95 % CI 1.05-2.03 and HR = 1.69; 95 % CI 1.17-2.42 in univariate and multivariate analyses respectively. Our results suggest that mesothelin is a prognostic breast tumor marker whose expression is highly enriched in triple negative breast cancer (TNBC) tumors. As there is no existing targeted therapy for TNBC, mesothelin may be a promising drug target for TNBC. Future work is needed to evaluate the efficacy of mesothelin directed targeted therapy in the treatment of breast cancer.

Expression and diagnostic values of calretinin and CK5/6 in cholangiocarcinoma

BACKGROUND

Mesothelin, a mesothelial marker, has been found expressed in and as a potential treatment target of cholangioacarcinoma (CC). It is possible that CC may be derived from the cells sharing mesothelial markers. However, the expression of other mesothelial markers in CC is largely unknown.

METHODS

Thirty CC cases (10 extrahepatic and 20 intrahepatic) were retrieved from our institutional archive. The immunohistochemical study of Calretinin (DC8), WT1 (6F-H2), Lymphatic Endothelial Marker (D2-40), CK5/6 (D5/16 B4) and CK19 (b170) was done on formalin fixed paraffin embedded sections for 2-3 blocks of each case. We compared the expression levels between CC and normal bile duct (NBD) on the same block.

RESULTS

All of the CC and NBD are positive for CK19 (23/23) and negative for WT1 (0/23) and D2-40 (0/23), except one CC positive for D2-40(1/30, 3.3%) and one NBD positive for WT1 (1/23, 4.3%). Calretinin immunoreactivity was detected in 52.2% (12/23) of CC, but none in NBD (0/23). CK5/6 was also detectable in 73.3% (22/30) of CC and all NBD (30/30). Increased expression of calretinin and reduced expression of CK5/6 were more likely associated with CC than NBD (P < 0.001 and P = 0.002, respectively). The sequential staining pattern of positive calretinin and negative CK5/6 in calretinin negative cases has a sensitivity of 69.57% and a specificity of 100% for differentiating CC from NBD. CK5/6 expression was also more likely associated with well-differentiated CC (7/7 versus 12/20 in moderately differentiated, and 9/10 in poorly differentiated, P = 0.019) and extrahepatic CC (10/10 versus 12/20 in intrahepatic, P = 0.029), but there was no association between the calretinin expression and the CC grade or location.

CONCLUSION

Calretinin and CK5/6 immunohistochemical stains may be useful for diagnosing a CC. Their immunohistochemical results should be interpreted with caution in the cases with differential diagnoses of mesothelioma and CC. A full mesothelioma panel, including WT1 and/or D2-40, is recommended to better define a mesothelial lineage. The biology of calretinin and CK5/6 expression in CC is unclear, but might shed light on identifying therapeutic targets for CC.

Trick to treat: tricking the thymus to treat cancer

In this issue of Blood, Schmitt et al address the biology and safety of T cells engineered to express T-cell receptor (TCR) variants endowed with enhanced affinity for tumor-associated antigens.