Feasibility of large-scale screening using N-ERC/mesothelin levels in the blood for the early diagnosis of malignant mesothelioma

Serum Levels of N- and C-ERC/Mesothelin and Clinicopathological Factors in Mesothelioma Patients and Those without Mesothelioma

Objectives

ERC/mesothelin is a glycosylphosphatidylinositol (GPI)-anchor protein expressed in mesothelioma. A precursor protein is cleaved by proteases and an N-terminal fragment (N-ERC) is extracellularly secreted. A remaining C-terminal fragment (C-ERC) is tethered on cellular membranes by the GPI-anchor, but C-ERC is also released after cleavage by proteases. We and other groups reported that serum N-/C-ERC levels are associated with stages of mesothelioma and suggested the possibility of their usefulness as diagnostic markers. However, the N-ERC level is also influenced by renal functions that are not directly associated with conditions of mesothelioma. It is not known whether other clinical factors influence serum N-/C-ERC values. Furthermore, their relationship to the amount of ERC/Mesothelin in mesothelioma is not yet validated. The objective of this study is to clarify the relationship of serum N-/C-ERC levels and the status of mesothelioma and several clinical factors.

Materials and Methods

We analyzed relations of serum N-/C-ERC levels and ages, gender and other clinical factors in 522 patients without mesothelioma and examined their relation to the amount of ERC/Mesothelin in mesothelioma tissues in 13 mesothelioma cases.

Results

Serum N-ERC levels were influenced by renal functions. On the contrary, those of C-ERC were not influenced by any clinical factors examined in this study and were significantly correlated with the amount of ERC/Mesothelin in mesothelioma.

Conclusion

Although both markers are good indicators of treatment-responses in individual patients with mesothelioma, only C-ERC reflected the amount of ERC/Mesothelin in mesothelioma among multiple patients, possibly because N-ERC was influenced by renal functions.

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.

Mesothelin as a biomarker for ovarian carcinoma: a meta-analysis

The objective of this work was to estimate the accuracy of mesothelin as a biomarker for ovarian cancer. A quantitative systematic review was performed. A comprehensive search of the Medline, LILACS, SCOPUS, Embase, Cochrane Central Register of Controlled Trials, Biomed Central, and ISI Web of Science databases was conducted from January 1990 to June 2015. For inclusion in this systematic review, the papers must have measured mesothelin levels in at least two histological diagnoses; ovarian cancer (borderline or ovarian tumor) vs. benign or normal ovarian tissue. For each study, 2 x 2 contingency tables were constructed. We calculated the sensitivity, specificity and diagnostic odds ratio. The verification bias was performed according to QUADAS-2. Statistical analysis was performed with the software Stata 11, Meta-DiSc(r) and RevMan 5.2. Twelve studies were analyzed, which included 1,561 women. The pooled sensitivity was 0.62 (CI 95% 0.58 - 0.66) and specificity was 0.94 (CI 95% 0.92 - 0.95). The DOR was 38.92 (CI 95% 17.82 - 84.99). Our systematic review shows that mesothelin cannot serve alone as a biomarker for the detection of ovarian cancer.

Newly established ELISA for N-ERC/mesothelin improves diagnostic accuracy in patients with suspected pleural mesothelioma

Pleural mesothelioma is an aggressive tumor, commonly caused by exposure to asbestos. The prognosis of mesothelioma remains disappointing despite multimodal treatment. We reported previously that N-ERC/mesothelin could be a useful biomarker for the early diagnosis of pleural mesothelioma and developed an enzyme-linked immunosorbent assay (ELISA) system for its detection. However, the reproducibility of our previous 7–16 ELISA system has been revealed to be unsatisfactory. To measure N-ERC/mesothelin more precisely, we developed a new 7–20 ELISA system. The subjects of this study were patients who were referred to our department with suspected pleural mesothelioma. The current study demonstrated that the newly established 7–20 ELISA system improved the sensitivity and specificity for diagnosing pleural mesothelioma compared with the previous system. Moreover, the 7–20 ELISA system showed better reproducibility and displayed the tendency of both higher sensitivity and higher specificity in plasma than in serum. Particularly for the epithelioid type, the area under the curve (AUC) and the diagnostic accuracy of N-ERC/mesothelin were excellent; the AUC was 0.91, the sensitivity was 0.95, and the specificity was 0.76 in plasma. In conclusion, assessment of N-ERC/mesothelin with our newly established 7–20 ELISA system is clinically useful for the precise diagnosis of pleural mesothelioma.

Retrospective analysis of large-scale research screening of construction workers for the early diagnosis of mesothelioma

The early diagnosis of mesothelioma, an aggressive malignant tumor, is considered to be important for prognosis. X-ray is commonly used for the assessment of a mass in a population exhibiting a risk factor. However, there are currently no available studies indicating that such an assessment may be used to achieve early diagnosis and improve the patient's outcome. We previously reported that N-ERC/mesothelin may be a useful blood tumor marker for mesothelioma. In order to investigate whether this tumor marker is useful for early diagnosis in a mass examination, in 2007 we initiated a 5-year large-scale screening of construction workers with a risk of asbestos exposure in Japan. Blood samples were collected annually and N-ERC/mesothelin levels were determined. Based on the results of those findings, along with medical history and related data, we screened the participants to identify a high-risk population. As a result, 62 subjects were identified among ~40,000 participants as the high-risk population. Two of these 62 participants subsequently developed mesothelioma, although the remaining participants have not yet developed mesothelioma. In conclusion, N-ERC/mesothelin may be useful as a blood tumor marker in the early diagnosis of mesothelioma in a mass examination. A future prospective study to confirm the findings of this research screening is currently under planning.

The utility of serum N-ERC/mesothelin as a biomarker of ovarian carcinoma

Ovarian carcinoma has been difficult to diagnose at an early stage. Recently, it has been recognized that the measurement of blood N-ERC/mesothelin levels aids early detection in and postoperative therapeutic monitoring of patients with mesothelioma, who have been exposed to asbestos. ERC/mesothelin has also been reported to be expressed in ovarian carcinoma. We determined serum N-ERC/mesothelin levels in patients with ovarian carcinoma using an enzyme-linked immunosorbent assay (ELISA). In addition, we immunohistochemically evaluated surgically resected specimens for C-ERC/mesothelin expression. As a result, of the 32 patients with ovarian tumors (18 carcinoma, 2 borderline tumors), one patient with serous adenocarcinoma showed increased N-ERC/ mesothelin levels. Immunohistochemically, of the 20 ovarian tumor (carcinoma and borderline tumor) specimens evaluated for serum N-ERC/mesothelin, 9 (45.0%) were positive for C-ERC/mesothelin. The C-ERC/mesothelin-positive specimens were found to be serous and clear cell adenocarcinomas. If serum N-ERC/mesothelin, which is considered useful for early detection in and therapeutic monitoring of patients with mesothelioma, may also be used for ovarian carcinoma monitoring, it may be a valuable serum tumor marker for the early detection of ovarian carcinoma.