Identifying and Validating Actionable Biomarkers in MPN
Research Spotlight on Rebekka Schneider, MD, Director, Department of Cell and Tumor Biology, Aachen University, Germany, and Erasmus MC Cancer Institute, The Netherlands.
In MPNs, your blood forming stem cell acquires a mutation, and this leads to more proliferation. In the beginning, you have too many blood cells. Then, in the course of the disease, these cells somehow activate cells that are not blood forming and lead to fibrosis or scarring of the bone marrow.
A pathologist by training, Dr. Rebekka Schneider explains the value of her work in this way. “Once you have fibrosis, your bone marrow can’t make blood cells anymore. It’s full of the scar tissue, which you can see under the microscope. “So you can see the scar tissue, but you can’t say in a patient, this patient is at risk to develop fibrosis. You can only say the scar tissue is there, or it’s not there. What we really want to understand is what happens earlier.”
The question she and her international team is working on is this: “Can we detect something that would allow us to diagnose a patient before the scar tissue is actually there . . . to prevent the scarring from happening . . . to help identify patients at risk?” They have identified certain genes or markers that have the potential to do this. And they are now examining these specific markers, and their relationship with each other, in larger patient cohorts.
Specifically, the focus of the MPNRF-funded project is on two potential biomarkers of MPN progression, SLAMF7 and CXCL4 in blood and bone marrow cells.
As Dr. Schneider works in Germany on CXCL4, her research partner, Ann Mullally, MD, of Brigham and Women’s Hospital, is examining SLAMF7 in monocytes in bone marrow cells in her Boston lab.
“It’s still a rather rare disease,” says Dr. Schneider. “It is a huge benefit that Ann Mullally and I are working together, each doing work on different samples,” from some 500 to 2000 patients. What makes the breadth of their work possible is that tissue can be studied that has already been collected, for example archived in pathology departments.
“We don’t need to have fresh tissue,” she explains, “and we ask colleagues to validate the staining and our findings in their cohorts.” This is important because they want to have something that’s very robust in the application of their findings, “so that it does not only work in our labs, but it works in labs basically around the word in the end.”
Back to her explanation of the fibrosis biomarkers they are looking at: “A biomarker could be a gene expression; it can be a protein or also a soluble factor in the blood. What you usually apply in pathology is immunohistochemistry, so you look for the protein. And that’s exactly what we are validating, is if the protein expression also correlates to the gene expression.” They are testing SLAMF7 and CXCL4 both in the bone marrow and different blood assays, through immunohistochemistry, flow cytometry and ELISA (Enzyme-Linked Immunoassay), a commonly used test to detect antibodies, antigens, proteins and glycoproteins in blood.
“We would love to identify a diagnostic marker in the blood. Then in a patient, you can take blood and see how this marker behaves. If it goes up (and at the point when it is up) then you could start a treatment with a goal that fibrosis never really occurs. And the marker goes down again,” says Dr. Schneider. “You would not necessarily need to have a bone marrow biopsy.” For researchers, practitioners, and of course patients, this would be a win/win.
“Today, we diagnose fibrosis when it’s already present. We want to understand how fibrosis starts and what the earliest forms are,” she adds. Then the goal would be to stop the beginning of fibrosis, or to prevent it from progressing when in its early stages.
In a similar line of experiments, Dr. Schneider is excited to share an update on work which stems from her previous MPNRF 2017 Challenge award.
“Using single-cell RNA sequencing, we identified the fibrosis-driving cells in bone marrow fibrosis,” she explains. “These fibrosis-driving cells show disease-specific up-regulation of the so called alarmins S100A8/S100A9, which are not expressed in these cells under normal conditions. Importantly, the S100A8/S100A9 grade increases with advancing disease and progressing fibrosis in the blood and in the bone marrow, indicating that the alarmins are the first biomarker to reliably predict the individual transition from the myeloproliferation phase to the life-threatening MF phase.”
Optimally, a biomarker for disease prediction also serves as a marker for therapy decision making, therapy response, and ultimately as a therapeutic target. The oral, anti-cancer, small molecule compound Tasquinimod inhibits binding of the alarmins to the TLR4 and RAGE receptors, important in the inflammatory response.
“We just received funding to perform a proof-of-concept clinical trial on Tasquinimod in heavily pre-treated patients with MPN and fibrosis (as a second line therapy),” adds Dr. Schneider. “We are working on the trial protocol at the moment and it is the goal to start recruitment of patients by the end of the year.” The trial will be conducted in The Netherlands and in Aachen, with Dr. Martina Crysandt (Aachen) and Dr. te Boekhoerst (Rotterdam) as clinical principal investigators.