Two studies released this week looked at the tumor-suppressing gene p53 and found that it doesn’t play nicely with CRISPR-Cas9. P53 is responsible for scrambling emergency services when DNA is damaged, which CRISPR-Cas9 does when cutting into DNA strands and adding some new DNA. The emergency response is a take-no-prisoners approach which either ‘fixes’ the DNA, rendering the gene therapy useless, or kills the cell. Astute readers may notice this also makes the therapy useless. That could answer why gene editing can be inefficient, and that’s also where the cancer risk comes in. The only cells that survive this process have faulty p53 genes, thus compromising the cells’ ability to fight future tumors. This was only observed with the DNA insertion process, so don’t sound the death knell for CRISPR just yet.