Scientists are developing a more effective diagnostic tool for mesothelioma by combining the blood levels of mesothelin (a marker for mesothelioma) and detecting fractions of a protein called MPF, according to a new study.
Mesothelin is an antigen present on normal mesothelial cells and is overexpressed in several types of tumors. MPF (megakaryocyte potentiating factor) is a mesothelin protein, and was the focus of this study to identify it as a potential biomarker.
Researchers at the Institute of the Ruhr-University Bochum in Germany have developed a cost-effective method to detect part of the MPF. The method, called an MPF ELISA test, is a blood test that can be used in combination with commercially available mesothelin ELISA tests to significantly improve the accuracy of mesothelioma diagnosis compared to using the mesothelin test alone.
The study, “A recombinant polypeptide of the megakaryocyte potentiating factor is a potential biomarker in plasma for the detection of mesothelioma,” was published in the journal Biochemical and Biophysical Research Communications.
“There is still a lack of validated biomarkers for the early detection of mesothelioma. The most promising marker so far is mesothelin, but a single marker is not sufficient to reach adequate sensitivity,” the researchers wrote.
“Consequently, a panel of several biomarkers will be necessary to achieve adequate sensitivity for screening in a high-risk population like former asbestos workers. Many different marker assays in turn will increase the cost of screening. Thus, available assays should be cheap or should have the potential to be developed into an affordable format,” they wrote.
The test group consisted of 41 mesothelioma patients — 33 men and eight women ages 35 t0 85. Thirty-one of the tested patients had epithelioid mesothelioma, six had biphasic mesothelioma, and four had sarcomatoid mesothelioma. These types of mesothelioma are distinguished by analyzing the cell types that become cancerous.
Seventy healthy volunteers who had been exposed to asbestos in the past were used as controls.
The gene for MPF was used to clone and artificially produce a portion of the MPF protein which was then injected into rabbits. Antibodies were produced in the animal model from the reaction to MPF, which could then be used in an MPF ELISA test to detect MFP in the blood samples of patients.
Mesothelioma patients had higher levels of MPF in their blood than the controls, particularly when the MPF ELISA test detected the amino acids 34-288 in the MPF protein.
In combining the two ELISA tests, the team found that it could diagnose mesothelioma with an accuracy of 80 percent. Using the mesothelin test alone showed a lower diagnosis accuracy rate of 77 percent.
Patients with the sarcomatoid subtype were an exception to these results, as they did not show an improvement in diagnosis. Drawing a conclusion, however, was difficult because of the low number of participants (four).
The new test could be used along with other noninvasive and cost-effective blood tests to detect mesothelioma, avoiding complicated procedures.
“In summary, a new MPF ELISA based on [antibodies] raised against a recombinant MPF34-288 polypeptide was established and is able to distinguish between asbestos-exposed controls and mesothelioma patients, but excluding those with a sarcomatoid subtype,” the researchers noted.
“Its diagnostic performance tested so far was comparable with the commercial MESOMARK mesothelin assay. After validation in a prospective study, the MPF34-288 ELISA could be a suitable, cost-effective tool to support a minimal invasive diagnosis of mesothelioma, especially in regions with limited medical care,” they added.