Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.
Stem cells screen drugs for kids’ rare tumor. A team at Johns Hopkins University in Baltimore has transformed stem cells into a particularly nasty form of pediatric brain cancer, medulloblastoma. They then used those cells to figure out what drugs might defeat the tumor and found one existing drug, approved for advanced breast cancer, that seemed to be a good candidate.
While about two-thirds of medulloblastoma patients do well with standard therapy, those in a class called “group 3” often do not survive. But the rarity of that condition, meant the researcher could not use what has become a common route to determining effective drugs: comparing the genetic profile of the cancer with the genetic profile of banks of cancer cells that have already have been tested against existing cancer drugs. There are not enough Group 3 samples in the banks to take that route.
So, the Hopkins team used a two-step process for the drug search. They first inserted genes associated with the Group 3 cancers into stem cells and let the cells begin to transform into tumors. After making sure their stem cell tumors genetically looked and behaved like medulloblastoma the researchers compared genetic “signatures” from those cells with the signatures of cells in the large databases of other cancers.
“We wanted to find whether the cells we created matched any of these existing signatures, because if they did, then we would have some idea of what kinds of drugs are more or most likely to kill these cells,” said Eric Raabe in a university release posted by ScienceDaily. “We didn’t have to do the laborious screening to test 100,000 compounds against our own cells.”
Raabe suggested this system might work to create a short cut to finding best therapies for other rare tumors as well.
Combining tricks from two critters. This article does not address stem cells directly, but rather a widely popular gene editing technique many hope to use with stem cell therapies, the system known as CRISPR. But before that can happen, researchers need to figure out how to eliminate or minimize pesky “off-target” gene editing, when the genetic scissor slices the DNA in a spot that was not intended.
CRISPR technology borrows from bacteria. About 40 percent of bacteria immune systems use CRISPR’s genetic elements to recognize foreign genes such as phages, the viruses that can kill or tag along in bacteria. Scientists generally pair CRISPR’s ability to recognize specific gene segments, with great specificity, with the nuclease, or genetic scissor, called CAS9. But that scissor is not quite as precise. So, a team at Kobe University in Japan borrowed an immune system trick from a second critter, a sea lamprey, sometimes incorrectly called an eel. The result was a much more precise gene editing tool.
The lamprey gene editing tool they borrowed is based on an enzyme called a deaminase. The lamprey uses the enzyme to create breaks in the genes for its immune system’s antibodies in order to have a more diverse immune system able to recognize more outside pathogens. That deaminase tool turns out to go a long way toward making CRISPR precise enough to be considered for use in a therapy.
The Japanese work published in the journal Science, marks the second time researchers have recently published a way to use a deaminase tool to improve CRISPR. The prior work came from the lab of Harvard’s George Church, who is quoted extensively in an article about the latest study in The Scientist. Be warned, Church likes detail and this is a pretty technical article unless you are a science nerd like us at The Stem Cellar.
Animals with bits of human get green light. A flurry of stories came out a few months ago when a reporter realized that while the National Institutes of Health (NIH) had a moratorium on creating chimeras—animal embryos that are partly human—CIRM was still funding the work. Now, NIH has announced plans to lift that moratorium with several safeguards in place to make sure certain projects that raise ethical issues don’t get approved. We are glad to have company in funding this potentially life-saving research.
Researchers working in the area have two main goals. They want to create better models of human disease, and they want to grow human organs in animals such as pigs to alleviate the current shortage of donor organs and help the thousands of patients who die each year waiting for a donor.
NPR aired a story that did a good job describing the safeguards and the types of projects that would not be allowed. It quoted Carrie Wolinetz, the NIH associate director for science policy:
“At the end of the day, we want to make sure this research progresses because it’s very important to our understanding of disease. It’s important to our mission to improve human health. But we also want to make sure there’s an extra set of eyes on these projects because they do have this ethical set of concerns associated with them.”
Forbes posted a story online that took great liberty with comparisons to science fiction, but had fun with it and in the end valued the potential for the work. And the public does have a chance to weigh in on the ethical issues as NIH has published a call for comments in the Federal Register.