Barcode for cancer cell
The new method allows you to track individual tumor cells
Anton Bugaichuk, Naked Science
Stanford University has developed a method that can significantly accelerate research into the nature of cancer and drug development (Rogers et al., Mapping the in vivo fitness landscape of lung adenocarcinoma tumor suppression in mice – VM).
Geneticist Monte Winslow, the head of the work, explains (in a press release Stanford scientists combine CRISPR and DNA barcoding to track cancer growth – VM):
"Human cancer has more than one mutation, there are combinations of them. The question is, how do different mutated genes interact or not interact with each other?"
Figure: Monte Winslow – VM.
Just a few years ago, such a study was impossible or required many years of work. It would be necessary to multiply several lines of genetically modified mice, each with its own pair of inactivated tumor suppressor genes. It would take hundreds or thousands of rodents to explore all possible combinations. Winslow and his colleagues coped in a few months, and less than two dozen mice participated in the experiments.
The researchers used the CRISPR-Cas9 mechanism, a powerful gene editing tool that can easily replace, modify or delete genetic sequences inside an organism.
CRISPR (Clustered regularly interspaced short palindromic repeats) are short palindromic repeats of groups of genes, with the help of which information about contact with viruses is stored, which makes it possible for a rapid immune response when encountering the same viruses repeatedly. In neighboring loci, Cas genes are located, which, with the help of enzymes, cut DNA molecules. This natural mechanism can be used to extract DNA fragments and replace them with others predetermined by RNA.
In order to investigate the combinatorial effects of various mutations, scientists needed an accurate way to label and track the growth of various tumors. It was decided to attach short unique DNA sequences to individual tumor cells in the lungs of mice. Figuratively speaking, each type of tumor cell received its own "barcode".
As a result, there was no need to separate tumors in order to examine their cells independently of healthy and cells of other neoplasms. It is enough to take a cancerous lung whole, chop it up, and then use DNA sequencing with counting the number of cells with the same "barcode". Quantitative data make it possible not only to determine the size of each type of tumor more accurately than with conventional methods, but also to obtain data for multiple tumors that have grown into each other. And even taking into account individual cells that can move around the body, they will still be in the total mass for sequencing.
Many different tumors can be grown in the same mouse, and the growth of each one will be determined separately and with high accuracy. This is important for the study of oncological diseases, in which several types of cancer cells may be present at the same time.
In addition, scientists have found that the work of many genes that affect tumor growth depends on the presence of other genes – this is a very important topic for future research.
The developed combination of using the CRISPR-Cas9 system and genetic "barcodes" is also useful when testing drugs: you can test the drug on thousands of tumor variations simultaneously to see which of them react and which ignore treatment.
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