Johns Hopkins biologist Kenneth Witwer was recently selected to lead a two-year grant of over $940,000 from the National Institutes of Health’s (NIH) National Cancer Institute. The team aims to develop new technology using extracellular vesicles to help diagnose, track and treat disease.
Extracellular vesicles are created when tiny pockets of the cell pinch off from its surface. Extracellular vesicles originate from many different types of cells and are often absorbed by nearby cells, making them potentially useful for packaging treatments for diseased cells.
Witwer discusses the promise of extracellular vesicles and the importance of collaborative research.
How did you get into this field?
I’ve been working with extracellular vesicles for my entire career. Since I began my training, I’ve worked on retroviruses such as HIV. As I transitioned into a faculty position, I became interested in how we could use various biomolecules to detect diseases, predict how diseases would progress and monitor how treatment affects diseases. The experience that I had working with HIV and other retroviruses lent itself very well to moving into the extracellular vesicle field because the origins of these particles are very similar to each other.
The retrovirus enters into infected cells, replicates and then exits through the cell membrane, taking a piece of the membrane with it. As a result, the retrovirus is really just a type of extracellular vesicle. Extracellular vesicles also break away from the cell membrane and carry with them something from the cytoplasm, or inside of the cell, such as RNA, a sister molecule of DNA.
How can extracellular vesicles be useful for disease diagnosis and monitoring?
Extracellular vesicles can contain biomarkers that may give us a window into what’s happening inside the organs of the body. The biomarkers they carry could indicate that a cancer has returned or that a tissue is diseased.
One example of a biomarker inside extracellular vesicles that scientists are working to understand is RNA. RNA is one molecular step beyond DNA, and it tells us what proteins the DNA is instructing the cell to produce. RNA would seem to be the worst possible choice for a biomarker because many RNAs are so easily degraded. But if RNA is protected from degradation, it could be a good biomarker because it’s easy to detect and very abundant.
How do researchers find these biomarkers?
We often find biomarkers in the blood, but they exist in other body fluids and solid tissues too. Many existing laboratory tests use biomarkers such as cholesterol, glucose and iron. Interest in using RNA as a biomarker began about a decade ago with the finding that RNA can be protected inside extracellular vesicles and other types of carriers such as lipoproteins and protein complexes. The question now is: How do we go from just looking at all the RNA in the blood to associating RNA with specific tissues affected by different conditions?
For example, a clinician might be trying to find out if someone has Alzheimer’s disease. If a routine, clinical test using an easily accessible sample, such as blood, can determine if a vesicle has come from a neuron by identifying proteins from the neuron that are on the vesicle surface, or the RNA inside it, that might be important for an Alzheimer’s test and help to inform the advice a clinician gives to a patient.
It’s really about understanding the body’s “address system,” which shows where a particle came from and where it is supposed to go. If I am studying an extracellular vesicle from a particular diseased tissue, but I can’t interpret the return address, or where it came from, I can’t determine where the vesicle originated and intervene with therapies that target the tissue. That is a major goal of this program: How can we use existing or new technologies to understand more about that address system.
When did the NIH become interested in this field?
About six years ago, the NIH announced a program called the Extracellular RNA Communication Consortium, which included more than 20 teams of researchers from the U.S., many of which were multi-institutional, and several collaborators from abroad. Twice a year, all the investigators would meet with the NIH and external advisers to share data, samples and ideas. It’s a really collaborative way of doing science. I was an external adviser for that round of the consortium and was very impressed with how the collaborations developed.
How successful was the first consortium?
As little as five years ago, some scientists were very skeptical of this field of research, and now there is more acceptance of it. The increased visibility of the field is a great outcome of the consortium, and it is gaining momentum as additional scientists get involved.
One of the tangible success factors is that more than 500 scientific publications were a result of the consortium, and some spurred commercial products and assays. We now have several approved cancer biomarker tests that are based on extracellular vesicles or circulating RNA. The consortium also collected a tremendous amount of data about extracellular RNA that is now publicly available.
What can you accomplish with this grant that you wouldn’t otherwise be able to do?
I am very excited about this opportunity, because it gives us a chance to connect with a very diverse team of researchers in the U.S. and elsewhere. The ability to meet with other scientists working in this field twice a year to exchange ideas is tremendously valuable, as is the level of input from the NIH. The NIH’s involvement is a way to supercharge the research and collaboration process and even recalibrate when we need to go in a different direction.