When cancer cells spread to new parts of the body in a process called metastasis, they often get there by traveling through the bloodstream. To avoid alerting the immune system and possibly triggering their demise, cancer cells coax circulating blood platelets to glom onto their surfaces and mask them from detection. This deceptive arrangement has raised a tantalizing possibility: What if blood platelets could be programmed to recognize and take out those metastasizing cancer cells?
Tara Deans, University of Utah, Salt Lake City, was recently awarded a 2019 NIH Director’s New Innovator Award to do exactly that. It’s an exciting opportunity for a researcher who stumbled onto this innovative strategy quite by accident.
Deans is a bioengineer and expert in designing synthetic gene circuits. These circuits consist of small collections of genetic “parts” that can be assembled and integrated to program cells to behave differently than their natural counterparts . In her initial work, Deans got these specialized gene circuits to prompt blood-forming stem cells to mass-produce platelets in the lab.
But blood platelets are unusual cells. They’re packed with many proteins that help to repair small nicks in blood vessels and stop the bleeding when we’re injured. Blood platelets do so even though they lack a nucleus and DNA to encode and make any of the proteins. Their protein cargo is pre-packaged and comes strictly from the bone marrow cells, called megakaryocytes, that produce them.
Deans realized that engineering platelets might pose a rare opportunity. She could wire the needed circuitry into the blood-forming stem cells and engineer them to make any desired therapeutic proteins, which are then loaded into the blood platelets for their 8- to 10-day lifespan. She started out producing blood platelets that could safely carry functional replacement enzymes in people with certain rare metabolic disorders.
As this research progressed, Deans got some troubling personal news: A friend was diagnosed with a blood cancer. At the time, Deans didn’t know much about the diagnosis. But, in reading about her friend’s cancer, she learned how metastasizing tumor cells interact with platelets.
That’s when Deans had her “aha” moment: maybe the engineered platelets could also be put to work in preventing metastasizing tumor cells from spreading.
Now, with her New Innovator Award, Deans will pursue this novel approach by engineering platelets to carry potentially promising cancer-fighting proteins. In principle, they could be tailored to fight breast, lung, and various other cancer types. Ultimately, she hopes that platelets could be engineered to target and kill circulating cancer cells before they move into other tissues.
There’s plenty of research ahead to work out the details of targeting the circulating cancer cells and then testing them in animal models before this strategy could ever be attempted in people. But Deans is excited about the path forward, and thinks that platelets hold great promise to function as unique drug delivery devices. It has not escaped her notice that this approach could work not only for controlling the spread of cancer cells, but also in treating other medical conditions.
You might recall learning in biology class that the cells constantly replicating and dividing in our bodies all carry the same DNA, inherited in equal parts from each parent. But it’s become increasingly clear in recent years that even seemingly healthy tissues contain neighborhoods of cells bearing their own acquired genetic mutations. The question is: What do all those altered cells mean for our health?
With support from a 2018 NIH Director’s New Innovator Award, Po-Ru Loh, Harvard Medical School, Boston, is on a quest to find out, though without the need for sequencing lots of DNA in his own lab. Loh will instead develop ultrasensitive computational tools to pick up on those often-subtle alterations within the vast troves of genomic data already stored in databases around the world.
How is that possible? The math behind it might be complex, but the underlying idea is surprisingly simple. His algorithms look for spots in the genome where a slight imbalance exists in the quantity of DNA inherited from mom versus dad.
Actually, Loh can’t tell from the data which parent provided any snippet of chromosomal DNA. But looking at DNA sequenced from a mixture of many cells, he can infer which stretches of DNA were most likely inherited together from a single parent.
Any slight skew in those quantities point the way to genomic territory where a tiny portion of chromosomal DNA either went missing or became duplicated in some cells. This common occurrence, especially in older adults, leads to a condition called genetic mosaicism, meaning that, contrary to most biology textbooks, all cells aren’t exactly the same.
By detecting those subtle imbalances in the data, Loh can pinpoint small DNA alterations, even when they occur in 1 in 1,000 cells collected from a person’s bloodstream, saliva, or tissues. That’s the kind of sensitivity that most scientists would not have thought possible.
Loh has already begun putting his new computational approach to work, as reported in Nature last year . In DNA data from blood samples of more than 150,000 participants in the United Kingdom Biobank, his method uncovered well over 8,000 mosaic chromosomal alterations.
The study showed that some of those alterations were associated with an increased risk of developing blood cancers. However, it’s important to note that most people with evidence of mosaicism won’t go on to develop cancer. The researchers also made the unexpected discovery that some individuals carried genetic variants that made them more prone than others to pick up new mutations in their blood cells.
What’s especially exciting is Loh’s computational tools now make it possible to search for signs of mosaicism within all the genetic data that’s ever been generated. Even more importantly, these tools will allow Loh and other researchers to ask and answer important questions about the consequences of mosaicism for a wide range of diseases.