Discovery proteomics, a rapidly evolving approach to proteomics led by advancements in mass spectrometry and analytical technologies, has emerged as a powerful tool in biomedicine. Scientists can now map proteins in order to achieve more targeted and effective diagnostics and treatments for diseases.

“The use of molecular analysis techniques like mass spectrometric and antibody-based platforms will be a key part of protein-level biology and translation over the coming decade,” said Neil Kelleher, PhD, professor of Hematology and Oncology and of Biochemistry and Molecular Genetics and the director of Northwestern’s Chemistry of Life Processes Institute.

Today, a new generation of blood tests combines the power of epidemiology with this emerging technology to identify protein biomarkers circulating in the blood that can determine a patient’s risk for conditions like lung disease, heart failure, and prostate cancer.

Feinberg physician-scientists like Sadiya Khan, ’09 MD, ’14 MSc, ’10 ’12 GME, the Magerstadt Professor of Cardiovascular Epidemiology and associate professor in the Department of Preventive Medicine, understand the value of this information and are working to leverage new insights to assess health risks for patients.

An expert in predicting the risk of heart disease and failure, Khan has previously shown that CT scans can predict a risk for a heart attack, markers from blood tests can predict risk for heart failure, and that obesity before pregnancy predicts future heart health. She even helped update a model used by the American Heart Association to predict a person’s risk of heart attack, heart failure, and stroke for up to 30 years. Now, thanks to discovery proteomics, she has another tool in her risk prediction toolkit: a blood test. In a study published in Cell Reports Medicine, she and her co-authors identified proteins circulating in a patient’s blood that are linked to a higher risk of heart failure.

“What if you could tell your risk of disease with a single drop of blood? A test like this could have immediate impact on identifying patients at higher risk for heart disease,” Khan said. “While we have many risk tools already at our disposal for heart disease prevention, if a new blood test could better tell us who was at higher risk of heart disease, then we could intervene and change their trajectory to prevent the disease rather than wait until they develop heart failure to treat them.”

One of several novel blood tests created or validated by investigators in the Feinberg School of Medicine within the past year, this test, and others like it, not only measure risk for a variety of conditions but can also offer a snapshot of overall health.

This new frontier of medicine energizes physicians not only because of its ease of use — a simple blood draw versus expensive imaging or biopsies — but also because newly identified proteins could provide a potential target for future therapies.

IDENTIFYING BIOMARKERS LINKED TO DISEASE

To create the tests, Khan and Ravi Kalhan, MD, ’06 MS, the Louis A. Simpson Professor of Pulmonary Medicine and associate dean of Faculty Affairs, examined thousands of blood samples from population studies.

One of those studies, the Coronary Artery Risk Development in Young Adults (CARDIA) study, the largest ongoing longitudinal study of cardiovascular disease, was launched at Northwestern and three other medical centers in 1985 and involves more than 5,000 people who have undergone examinations and testing every five years.

Investigators identify patients within these population studies with certain conditions, such as lung disease or heart failure, and then compare the protein levels in their blood against patients who do not have those conditions. Because these ongoing studies include blood samples that patients have given over decades, investigators can also see how protein levels change over time.

“We have had significant advances in how we can measure biomarkers in the blood,” Khan said. “So now we can go back to these stored blood samples and test them with technology that wasn’t available at the time.”

The final list of proteins that are correlated with these conditions are then compiled into a risk score and tested further among other population study groups.

“It’s like a cholesterol test,” said Kalhan, a co-author of the study. “When you go to your doctor and get your cholesterol measured, it predicts your risk of future cardiovascular disease. And if your levels are high, you can intervene with treatments. Now we have a way to use these epidemiology studies to find new biomarker proteins and create those kinds of risk prediction tests for other conditions.”

A ‘CHOLESTEROL TEST’ FOR LUNG HEALTH

For Kalhan, a pulmonologist and professor of Preventive Medicine in the Division of Epidemiology, having something like a “cholesterol test” for lung health has been a longtime dream.

“Most people are diagnosed with lung disease because they go to their doctor with respiratory symptoms or land in a hospital with bronchitis,” he said. “Let’s say they are 60 years old. Perhaps when they were 45, their lung function would have been normal. I’ve been frustrated that we don’t have something like a cholesterol test that we can give patients when they are younger that can predict future lung health.”

With Khan, Kalhan developed a blood test that identifies who is most at risk for severe respiratory illness, including chronic obstructive pulmonary disease (COPD).

Using blood samples from the CARDIA study, he and Khan and their teams identified 32 protein expression levels in patients who had lung function decline. They tested these levels against two other large patient cohorts to ensure they were predictive.

Once validated, those proteins were compiled to create a risk score. The research team found that adults with higher risk scores had a 17 percent increased risk of requiring hospital care for respiratory illness. Those adults also had an 84 percent increased risk of developing COPD and an 81 percent increased risk of dying from a respiratory disease. The results were published in the American Journal of Respiratory and Critical Care Medicine.

“This is the moment we have been waiting for,” Kalhan said. “Prior to this test, we did not have a way to predict who was at risk for these bad outcomes, which was very frustrating in clinical practice. But once we test these findings and validate them further, we could potentially one day target high-risk patients with therapies and counsel them on lifestyle changes.”

DIVING DEEPER FOR OVERALL HEALTH INSIGHTS

These biomarker blood tests could also provide a snapshot of hard-to-measure health attributes, like fitness, for which current tests are bulky, time-consuming, and costly. In a study published in Nature Medicine, Kalhan and Khan also developed a biomarker test to measure cardiorespiratory fitness. This time, they found proteins related to inflammation, neuronal survival and growth, and oxidative stress. They again compiled these proteins into a scoring system, which they tested by analyzing the circulating proteins of more than 600 people before and after a 20-week exercise program.

“We know being fit is good for you, but how do we measure fitness?” Kalhan said. “Now we can use a blood test to measure it without having to do an exercise study or a treadmill test.”

REDUCING UNNECESSARY PROSTATE CANCER BIOPSIES

As novel blood tests like these are developed, it’s important to validate them across multiple groups to ensure they are effective in different populations.

Adam B. Murphy, MD, MBA, ’14 MSCI, ’10 GME, the Distinguished Professor of Population Health Research in Urology, made this his goal when he launched a study to determine if a novel blood test could better detect prostate cancer in Black men.

The Stockholm3 test — a next-generation blood test developed at Karolinska Institutet in Sweden —combines protein biomarkers with genetic markers and clinical data to detect prostate cancer at an early stage. Although prostate cancer risk can already be estimated by the prostate-specific antigen (PSA) blood test, PSA is not specific to cancer and may lead to overdiagnosis.

“Tests like Stockholm3 can better weed out people who are not likely to have prostate cancer,” said Murphy, who is also an associate professor of Preventive Medicine in the Division of Cancer Epidemiology and Prevention and assistant director of Community Outreach and Engagement for the Robert H. Lurie Comprehensive Cancer Center of Northwestern University and served as principal investigator of the U.S. clinical validation for the new test. “It could also ultimately reduce unnecessary biopsies for low-grade prostate cancer, which is unlikely to be lethal.”

But prostate cancer risk varies widely among different groups, and Black men are much more likely to get prostate cancer and have higher mortality rates than white men. Hispanic, Asian, and Native American men have much lower rates of the disease.

The U.S. Stockholm3 study enrolled more than 2,100 patients from 17 clinical sites. In a study published in the Journal of Clinical Oncology, Murphy and other investigators found that the test reduced the number of benign and low-grade prostate cancer biopsies by 45 percent overall. Notably, it reduced them to between 42 percent and 52 percent across racial and ethnic subgroups.

“I think there will be a time in the future when we can do a liquid biopsy using blood or urine,” Murphy said. “Combinations of these tools with clinical data and maybe even genetic risk factors could replace a biopsy one day. It’s going to continue to be exciting to see these biomarkers help us to individualize care. Patients are not going to just be getting a one-size-fits-all treatment system.”

A TARGET FOR FUTURE THERAPIES

While these tests could have real impact in providing a risk assessment for patients, the ultimate goal is to use these biomarkers as targets for treatment. Such therapies already exist — the drug tafamidis, for example, targets the protein malformation that occurs in amyloid heart failure.

“If we can find out that this marker or this protein is really the cause of a specific type of disease, maybe we can change that marker by targeting it with a new drug,” Khan said. “And that’s where this research will get really interesting.”

Photos by Gr8y Productions.