Dr. James Stevenson, M.D.
Biomarkers, Blood Tests and Diagnosing Mesothelioma
Biomarkers are measurable substances in the body that can suggest that a patient has a certain disease or condition like malignant mesothelioma. Cancer cells use nutrients faster than normal cells, which can lead to an excessive amount of byproducts in the blood.
Normal mesothelial cells produce a glycoprotein (sugar + protein molecule) called mesothelin. Malignant mesothelioma cells produce mesothelin as well, but in much higher quantities, in part due to faster growth rates. Various blood tests can show these byproducts and may be able to show that a patient has mesothelioma before tumors are recognized, prompting imaging scans or a biopsy.
Types of Mesothelioma Blood Tests and Biomarkers
Though blood tests cannot diagnose mesothelioma on their own, biomarkers continue to emerge that help show a patient may have mesothelioma or have been exposed to asbestos, putting them at high risk for developing the cancer.
MESOMARK is a blood test that works by testing for high levels of soluble mesothelin-related peptides (SMRPs), which are fragments or variants of mesothelin found in blood serum and pleural fluid. SMRPs are produced in much higher quantities by mesothelioma cancer cells, especially in the case of pleural mesothelioma. SMRP levels also tend to be higher in individuals with stage 3 or stage 4 mesothelioma, and as a result, the MESOMARK assay is more accurate in detecting those later stages of the disease. Overall, the sensitivity of the test ranges widely, from about 19 – 68%, making it insufficient to diagnose mesothelioma on its own.
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HMGB1 (High Mobility Group Box Protein 1) is a newer biomarker that has shown much promise in the early detection of mesothelioma. One study found that it was able to distinguish between mesothelioma patients, those exposed to asbestos but without mesothelioma and those with no history of asbestos exposure. HMGB1 has been used as a biomarker for other types of cancer including non-small cell lung cancer. It needs to be researched further for mesothelioma, but can act as a tool for identifying risk factors for developing the disease.
N-ERC/mesothelin is a fragment of the glycoprotein mesothelin and has shown a 95% sensitivity rate in research studies, which is extremely high, but not enough to allow for a diagnosis on its own. While this particular biomarker assay is promising, additional testing is required before it could be used widely for an accurate mesothelioma diagnosis. However, it can be used to determine what treatment options are working, as well as if mesothelioma has recurred after treatment.
Osteopontin is another glycoprotein that is found at higher levels when patients have certain cancers. In 2005, Dr. Harvey Pass and a team of colleagues showed a correlation between the biomarker and mesothelioma. Although osteopontin levels may be a good indicator of whether a person is ill, it is poor at diagnosing mesothelioma specifically because increased levels may be due to other conditions like kidney stones, ischemic stroke and various inflammatory/autoimmune diseases. Many studies reference the Human Osteopontin ELISA Kit as one way to measure the protein’s presence.
Another glycoprotein produced by mesothelioma cells is fibulin-3. Like osteopontin, fibulin-3 has a high sensitivity level of 97%, but cannot be used on its own to diagnose mesothelioma. Studies have shown that a fibulin-3 test can be useful in helping doctors track cancer progression, as well as the effectiveness of treatment efforts.
The Slow Off-Rate Modified Aptamer (SOMAmer) proteomic test is a type of blood test that measures for over 1,000 proteins, including many mesothelioma biomarkers. The library of proteins that this test measures is frequently expanding to find potential new biomarkers for the disease, and there is currently a panel of 13 mesothelioma biomarkers that can be detected. Case studies have shown that this test is accurate in around 90% of mesothelioma cases.
Human MPF Elisa KIT
The Human Megakaryocyte Potentiation Factory (MPF) Elisa Kit measures for the presence of megakaryocyte potentiation factor, which is a protein in the mesothelin gene. Case studies have shown that elevated MPF levels emerged in over 90% of late-stage mesothelioma patients and was not present in those without the disease. Physicians have also used the MPF blood test to monitor cancer progression throughout treatment, noting a drop in MPF levels when large amounts of cancer were removed during surgery. This test has also been used to help diagnose ovarian cancer and pancreatic cancer.
8OHdG is a biomarker that notes cellular damage, which occurs during cell mutation as cancer develops. Elevated 8OHdG levels have been linked to asbestosis and can also show that a patient has been exposed to asbestos, the only known cause of malignant mesothelioma. The main drawback of this biomarker is that it cannot definitively differentiate between those with mesothelioma and those without.
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Other Biomarkers & Blood Tests
New biomarkers and blood tests are constantly emerging that could aid in the early detection of mesothelioma, mesothelioma symptoms and asbestos exposure risk, including those listed below.
- CA-125: The CA-125 blood test measures for cancer antigen 125. Elevated levels have been able to aid in the diagnosis of peritoneal mesothelioma.
- IL-6: Interleukin-6 (IL-6) is a protein produced by immune cells. IL-6 levels will increase during an immune response, which has been linked to malignant mesothelioma and related symptoms.
- EGFR: The epidermal growth factor receptor (EGFR) is a protein that has proven to be activated in patients with a history of asbestos exposure, a key risk factor in the development of mesothelioma.
- ER-β: Estrogen receptor-β (ER-β) is typically found in the pleural tissues, but is seen in elevated levels in patients with a poor prognosis. While ER-β can’t differentiate between those with or without mesothelioma, it can aid in determining prognosis.
- PDGF: The platelet-derived growth factor (PDGF) in mesothelioma patients has been overexpressed in several studies, suggesting a correlation between PDGF and malignant pleural mesothelioma.
- VEGF-B: Vascular endothelial growth factor-beta (VEGF-B) is a protein produced by the VEGF-B gene that controls the growth of new blood vessels. Elevated levels have been linked to malignant pleural effusions, potentially aiding in the diagnosis of pleural mesothelioma.
Diagnosis After Blood Tests
Biomarker tests can help distinguish between patients who have mesothelioma and those who are cancer-free, while also helping identify potential risk factors of the disease like asbestos exposure. Though a biopsy is the only way to definitively diagnose malignant mesothelioma, blood tests can suggest the presence of mesothelioma cancer, encouraging imaging tests like x-rays and CT scans to identify potential tumors and biopsies to aid in early detection. For mesothelioma patients, early detection is the best way to improve prognosis.