Metastasis is responsible for the majority of cancer-related deaths, but it is difficult to detect. Now, a group of researchers has developed a CRISPR-based method that helped monitor tumor spread patterns.
Researchers from the Massachusetts Institute of Technology (MIT), University of California, Berkeley and University of California, San Francisco used a CRISPR gene editing tool to map a detailed family tree that revealed the dynamics behind the development and progression of cancer metastasis. .
While monitoring the cancer cells, the scientists found genes that added to or suppressed the cells’ metastatic potential, as well as the “hubs” of metastasis that they believe could be targeted by new cancer treatments. The results were published in Science.
“With this method, you can ask questions such as, ‘How often does this tumor metastasize? Where did the metastases come from? Where are they going? ‘ ”Dr. Jonathan Weissman, MIT biology, Ph.D., co-author of the study, said in a statement. “Being able to trace the history of the tumor in vivo reveals differences in the biology of the tumor that were invisible.”
Existing cancer-line tracking devices are limited by their sensitivity to malignancies and their inability to detect information about the movement of cell subconscious. So Weissman and colleagues turned to CRISPR-Cas9 technology.
In their study, the researchers used a mouse model of human KRAS-mutant lung cancer. They engineered the cancer cells with the gene encoding the Cas9 protein. As the cells were divided into the mice, Cas9 made cuts at target DNA sites, leaving a repair sequence called an “indel,” which allowed the researchers to locate the cells using computer models.
Surprisingly, the tumor cells took different pathways after transplantation, even though they all came from the same cell line. The original cells seemed to develop different metastatic features as the cell line progressed through many generations, the researchers counted. So they went on to look for differently expressed genes among the cells for notification to metastasis.
One gene called KRT17, which encodes for Keratin 17 protein, evolved because its expression was strongly associated with reduced metastatic potential. “When we dropped Keratin 17 or put too much pressure on it, we showed that this gene actually controls tumor invasion,” Weissman said.
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The researchers developed phylogenetic trees (see picture above), which showed the transmission pathways and direction of metastasizing cells in the body. Using these maps, they found that many cells were metastasized primarily through the mediastinal lymph material, suggesting that site was a nexus for metastatic proliferation in the mouse model.
Identification of these metastasis hubs may be helpful in treatment. “If you focus cancer treatments on those areas, you could then slow down or prevent metastasis in the first place,” Weissman said.
Finding ways to prevent cancer metastasis is a popular pastime in oncology research. Recent examples include a discovery by Fred Hutchinson Cancer Research Center researchers of signal room in accumulated breast cancer cells, in which the EPGN gene plays a critical role in the formation of distant metastases. A team at the Sanford Burnham Prebys Medical Discovery Institute identified a protein called PPP1R1B as a major driver in the spread of pancreatic cancer.
The new CRISPR-based line detection method could inform many other aspects of cell cancer biology, the MIT-led researchers said, including “the timing or sequence of genetic mutations at a time malignant transformation, adaptation to different tumor microenvironments, or origin and mechanism by which tumor cells react with therapeutic agents, ”they wrote in the study. Moving forward, the team hopes to one day use this information to predict cancer cell behavior.