DNA editing outside the cell with CRISPR could improve cancer diagnosis

'Cell-free' CRISPR has been developed by scientists at the Christine Care Health System's Gene Editing Institute in Delaware, US, allowing them to extract cellular DNA and make multiple, significant edits to the genetic code.

Researchers used the enzyme Cpf1 in the technique instead of the more common Cas9. After DNA was removed from the cell in the form of plasmids (small circular sections of DNA), Cpf1 was used to cut the DNA. 

Brett Sansbury, first author of the study published in the newly-established CRISPR Journal, noted that Cas9 produced 'blunt ends' to the DNA, but Cpf1 produced 'sticky ends', which could be easily joined to other strands of DNA. She speculated that this could account for the new system's ability to easily insert large genes. 

The approach could have immediate application in diagnostics and personalised medicine, the authors say. For example, it could be used to replicate the exact mutations found in a patient's tumour, to see how it might react to various treatments.

'With this new advance, we should be able to work with laboratory cultures and accomplish gene edits in less than a day, significantly reducing the time required for diagnostics compared to other CRISPR tools, and with much greater precision,' said Dr Eric Kmiec, another study author and director of the Gene Editing Institute. 'This is particularly important for diagnostics linked to cancer where time is critical.'

The new CRISPR-Cpf1 approach could be used commercially as part of a lab-on-a-chip tool, the researchers hope. It could eventually be used as a therapeutic tool to allow replacement of whole genes in a cell, rather than editing one or two specific mutations in a faulty gene. For diseases with a complex genetic element, such as Alzheimer's and heart disease, involving multiple mutations, the goal is 'not really gene editing, but gene replacement', said Dr Kmiec. 

However, a fully developed therapy based on this research is still a long way off. In the nearer future, the team believes their discovery will shed light on the mechanism of CRISPR itself.

'When you're working with CRISPR inside a cell, you're kind of working in a black box where you can't really observe the gears of the machinery that are doing these amazing things, ' said Dr Kmiec. 'You can see the results, the edits to the genes, but not necessarily how you got there, which is important for ensuring that CRISPR can be safely used to treat patients.'