The standard laboratory test to diagnose multiple myeloma dates back to the Eisenhower administration. Research at Mayo Clinic spearheaded by David Murray, M.D., Ph.D. (PATH ’10), and fueled by his experience as an industrial chemist has led to a new assay to screen and diagnose the disease.
Despite gargantuan leaps in medicine in the last 60 years, serum protein electrophoresis has remained the standard for finding a monoclonal antibody — often the first step in diagnosing multiple myeloma. This test, which is performed by hand, involves putting the patient’s serum on a gel, applying an electrical current to it, separating out the proteins, and looking for overexpressed immunoglobulins by immunoelectrophoresis or immunofixation. The process takes hours per patient sample, and the test isn’t particularly sensitive. The test may be negative when disease is still present in the patient as evidenced by bone marrow biopsy or other findings.
“Physicians have known for quite a while that the standard test wasn’t sensitive enough to detect the disease in all cases,” says Angela Dispenzieri, M.D. (I ’94, HEMO ’98), Division of Hematology and the Serene M. and Frances C. Durling Professor. “Bone marrow biopsy is more sensitive, but it’s expensive, invasive and isn’t pleasant for the patient.”
Dr. Murray joined the Mayo Clinic staff in the Division of Clinical Biochemistry and Immunology in 2010 after completing a residency in pathology at Mayo Clinic School of Graduate Medical Education. Prior to medical school, he earned a Ph.D. in polymer chemistry and was an industrial chemist at Eastman Kodak for 10 years. He worked in material science, developing new plastics and materials for packaging and paint.
As a resident, he rotated through the Mayo Clinic Protein Immunology Laboratory and saw a knowledge gap and opportunity.
“I walked into the lab and thought, ‘They’re still running gel electrophoresis in this day and age?’” says Dr. Murray. “That’s an ancient technique. I spent a lot of time in a high-tech chemistry lab and know that mass spectrometry is much better. Most physicians don’t have that industry experience. I recognized a knowledge gap and saw that my talents could be used to develop a better test to help physicians and patients."
“I also saw unbelievable opportunity. Dr. Robert Kyle (I ’59, Division of Hematology’s Myeloma, Amyloid and Dysproteinemia Group) has a legendary database of serum samples of multiple myeloma patients dating back to 1960. For a researcher, that’s pure gold. It means we have access to unlimited samples to validate any new test on.”
Dr. Murray got to work on developing a new test with David Barnidge, Ph.D., a mass spectrometris working in laboratory medicine at the time. They experimented with mass spectrometry, an analytical technique used to determine the molecular mass of specific molecules in a sample. The colleagues found that MALDI-TOF (matrix-assisted laser desorption/ ionization time of flight) mass spectrometry, which uses a rapid fire laser to ionize proteins into the gas phase, allowed them to rapidly analyze immunoglobulins.
After six years their team had developed a mass spectrometry testing method that was adaptable to the lab and was more sensitive than the standard gel technology used to diagnose multiple myeloma. Mass spectrometry identifies and quantifies monoclonal antibodies secreted in the patients’ serum. For two years the team performed clinical and analytical validation on 2,000 samples from Dr. Kyle’s database.
“We could never have done this at another institution without access to that serum database,” says Dr. Murray. “In the 1990s Dr. Kyle screened 77 percent of the Olmsted County population for MGUS (monoclonal gammopathy of undetermined significance), a condition in which a monoclonal or abnormal protein is present in the blood. MGUS causes no problems but can progress to multiple myeloma or related disorders. A group of those people who tested negative were diagnosed with MGUS more than a decade later. Dr. Kyle had preserved their negative-testing serum samples. Using our new testing method, we detected MGUS in the 1990s samples of half of that group. Had the more sensitive test existed then, those individuals could have been diagnosed much earlier.”
The new test was introduced by Mayo Clinic Laboratories in July 2018. Mayo Clinic now uses the monoclonal gammopathy screening on all patients with or suspected to have a plasma cell disorder.
Mayo Clinic licensed the test technology to The Binding Site, a company that provides specialty diagnostic products to clinicians and laboratory professionals worldwide, to assist with obtaining Food and Drug Administration approval. Dr. Barnidge became laboratory director for The Binding Site, and the company built a research laboratory in Rochester to focus on this project.
Dr. Murray has been in high demand since the hematology community learned of this significant development at Mayo Clinic. At least once a week he’s invited to speak to groups about what his team has discovered about immunoglobulins.
“Long before multiple myeloma can be detected by conventional methods, mass spectrometry allows us to see the unique origins of the disease and possibly the disease mechanism,” says Dr. Murray. “New methods allow you to see things with new eyes. And new eyes were definitely needed to modernize the way we detect and diagnose this disease.”
Dr. Murray says Dr. Kyle, widely considered to be “the godfather of multiple myeloma,” is one of his biggest supporters. “Dr. Kyle said this is the greatest advance since the death of U-tube — U-tube electrophoresis, the predecessor to gel electrophoresis.
“If I’d done this work anywhere else, I’d have published a paper and no one would have paid attention to it. It’s gotten so much traction because Mayo Clinic is universally regarded as the home of multiple myeloma. The attitude in the myeloma community was, ‘If you guys can’t do it, no one can. We’ll wait for you to do it.’ The collaborative environment at Mayo allowed me to work closely with Dr. Kyle. It was a team effort from everyone in the lab and in the Myeloma, Amyloid and Dysproteinemia Group. Shared credit goes to John Mills, Ph.D. (CLCH ’15, CMG ’17, Division of Clinical Biochemistry and Immunology), a former fellow who defined and is co-inventor of the MALDI-TOF assay; Surendra Dasari, Ph.D. (HSR ’12, Department of Health Sciences Research), who did the bioinformatics work and designed a software interface for the assay; and development technologist Mindy Kohlhagen, who spent countless hours optimizing and validating the assay. I couldn’t have done this work without them.”
Dr. Murray is working closely with Dr. Dispenzieri and her colleague S. Vincent Rajkumar, M.D. (HEMO ’99), Division of Hematology and the Edward W. and Betty Knight Scripps Professor of Medicine in Honor of Edward C. Rosenow, III. Both serve on the International Myeloma Working Group, which develops guidelines for the diagnosis of multiple myeloma. The trio presented the new assay to the group in Stockholm, Sweden, in June 2018 for consideration in future guidelines.
The new test’s big debut was at the American Society of Hematology annual meeting in San Diego in December. Dr. Murray says the Mayo Clinic Laboratories booth had a steady stream of inquisitive clinicians and laboratorians interested in the role of the new test in detecting minimal residual disease and the possibility of eliminating gels from their labs.
“We’re letting the world know the test is available,” says Dr. Murray. “I’ve done grand rounds at other major cancer institutions, and there’s great excitement about it. Ultimately, the test needs to be offered by other institutions, not just Mayo Clinic Laboratories. A test can’t be the standard if you’re the only ones who offer it. We’re collaborating with The Binding Site to commercialize the assay. In the meantime, the test is available to Mayo Clinic patients and clients of Mayo Clinic Laboratories.”
An unintended consequence of Dr. Murray’s work was the discovery that some patients have glycosylation on light chain immunoglobulins, which was shown to be a risk for AL amyloidosis, a rare bone marrow disorder in which plasma cells produce an abnormal antibody protein. AL amyloidosis may be undetectable by standard gel electrophoresis.
“A Mayo physician was trying to figure out if a symptomatic patient had AL amyloidosis,” says Dr. Murray. “Our new test indicated the patient had the indicative light chains, but the patient’s tissue biopsy didn’t show amyloid. Because the light chains indicated the patient was at high risk for the disease, I urged the physician to keep looking. A subsequent biopsy showed amyloid, and the diagnosis was established.
“AL amyloidosis is a terrible disease that can go years without diagnosis. This patient was able to be treated much sooner due to the definitive diagnosis. Without the new test for multiple myeloma, the diagnosis probably wouldn’t have been made until much later. It feels good to know I’m helping people.”
Dr. Murray and his team continue their work, looking for additional risk factors for AL amyloidosis and the light chain immunoglobulin that causes renal failure in multiple myeloma patients.
“Today multiple myeloma generally isn’t considered curable,” says Dr. Murray. “We’re getting glimpses into the mechanisms that cause the disease. And we’re strengthening the ability to know when the disease is still active. This advance could change how the disease is treated. For example, if we can tell more definitively when there’s still evidence of disease, we might keep treating it until there’s no evidence of disease.
“I’m humbled to have lent my chemistry skills honed in industry to this major milestone in the diagnosis and treatment of myeloma. My work stands on the shoulders of Dr. Kyle and everyone else who has worked in the group at Mayo that established Rochester, Minnesota, as the home of multiple myeloma research.”