2D Gel Immunoblot Test Detects Mesothelioma Biomarkers in the Blood Years Prior to Appearance of Symptoms

It is usually caused by exposure to asbestos. The most common anatomical site for the development of mesothelioma is the pleura (the outer lining of the lungs and internal chest wall), but it can also arise in the peritoneum (the lining of the abdominal cavity), the pericardium (the sac that surrounds the heart), or the tunica vaginalis (a sac that surrounds the testis). The three-year survival rate for patients with this disease is only 8%, as most patients are diagnosed with late stage disease with limited therapeutic options.

Investigators at the biomedical company MorNuCo Inc. (West Lafayette, IN, USA) used their proprietary ONCOblot cancer detection test to determine the serum presence of mesothelioma-specific protein transcript variants of ecto-nicotinamide adenine dinucleotide oxidase disulfide-thiol exchanger 2 (ENOX2), a recently identified marker of malignancy. ENOX proteins are expressed on the cell surface of malignancies and are detectable in the serum of patients with cancer.

In the ONCOblot procedure, ENOX2 proteins are separated from the bulk of the albumin and other serum proteins by two-dimensional separation with separation in the first dimension by isoelectric focusing and separation in the second dimension by sodium dodecyl polyacrylamide gel electrophoresis. After transfer of proteins from gels to a nitrocellulose membrane, the detection step utilizes a proprietary recombinant pan-ENOX2 antibody that cross-reacts with all known ENOX2 isoforms of human origin. Presence of any ENOX2 proteins is recognized as dark spots on a light background. The test results reveal a pattern of ENOX2 proteins in a patient's sera. This serves not only as a molecular indicator of cancer presence but precisely identifies the tissue of origin of the cancer.

In the current study, sequential serum samples collected from asbestos-exposed individuals prior to the development of frank mesothelioma were assayed for ENOX2 presence by two-dimensional gel immunoblot analysis to determine how long in advance of clinical symptoms mesothelioma-specific ENOX2 transcript variants could be detected.

Results revealed that two mesothelioma-specific ENOX2 protein transcript variants were detected in the serum of asbestos-exposed individuals four to 10 years prior to clinical diagnosis of malignant mesothelioma (average 6.2 years). Either one or both ENOX2 protein transcript variants indicative of malignant mesothelioma were absent in 14 of 15 subjects diagnosed with benign pleural plaques either with or without accompanying asbestosis.

"The completion of this trial is an exciting new chapter for our work," said Nick Miner, vice president of business development at MorNuCo Inc. "Although asbestos-induced mesothelioma is a very specific example of early detection, we are currently pursuing larger-scale clinical trials to investigate the utility of the ENOX2 protein marker to predict the onset of cancers of other tissues of origin as well."

The ONCOblot study was published in the January 22, 2016, online edition of the journal Clinical Proteomics.

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