Earlier this fall, the NIH Recombinant DNA Advisory Committee approved the first human trials of the genome-editing technology CRISPR/Cas9 for creating genetically-altered immune cells to attack certain types of cancer. In late October, scientists in China began the first human trials using this technique.
The team at the West China Hospital in Chengdu extracted immune cells from a patient with aggressive lung cancer and then edited them using CRISPR/Cas9 before injecting them back into the patient. The technique knocks out a gene that typically serves as a check on the cell’s ability to launch an immune response and prevents it from attacking healthy cells. The modified cells were then multiplied and re-introduced into the patient’s bloodstream. The team hopes these cells will wipe out the cancer. The trial plans to treat 10 patients, and its main purpose is to test safety. The team will release more details as the trial progresses, as researchers around the world will likely be watching closely to learn more about CRISPR’s potential to treat cancer.
CRISPR stands for Clustered Regularly-Interspaced Short Palindromic Repeats. CRISPRs are part of the bacterial immune system, and they defend against invading viruses. They consist of repeating sequences of genetic code interrupted by “spacer” sequences – remnants of genetic code from past invaders. The system helps the cell detect and destroy invaders when they return. Cas9 is one of the enzymes produced by the CRISPR system that binds to the DNA and snips it, shutting the targeted gene off. Scientists believe that if we can go into the genetic mutations that cause disease and change these mutations to the normal sequence, the technology could potentially cure disease. Other gene-editing techniques exist, but they are slow, imprecise, and very difficult.
A team in the US is also planning a human trial in early 2017 to target myeloma, sarcoma, and melanoma. In Beijing, a team is planning to launch trials targeting bladder, prostate, and renal-cell cancers in the spring. Many are comparing the race to figure out how to use CRISPR-editing techniques to treat cancer to the race to land a team on the moon.
Analysis: Potential applications for CRISPR range from curing different diseases to growing organs that could be used in transplants to possibly preventing genetic diseases in embryos. While not in the stage of human trials yet, US researchers also had a recent breakthrough using CRISPR to cure blindness in rats. The study, published in the journal Nature, shows that rats engineered to have a genetic form of blindness called retinitis pigmentosa could be treated using CRISPR gene therapy.
While many in the scientific community are citing CRISPR/Cas9 as one of the biggest breakthroughs in modern medicine, many researchers are proceeding with caution. One concern is that CRISPR could snip other genes and potentially create new cancer genes or trigger existing ones. The pioneering teams will likely be carefully measuring the growth rate of the engineered cells and testing for genomic abnormalities. Another concern is that the technique could activate the body’s immune response. For these reasons, leaders in the field are cautioning that the scientific community must proceed carefully to ensure the benefits outweigh the risks from potential misuse and unforeseen consequences.
David Cyranoski, “CRISPR gene-editing tested in a person for the first time,” Nature, November 15, 2016
Keiichiro Suzuki et al, “In vivo genome editing via CRISPR/Cas9 mediated homology-independent targeted integration, Nature, November 16, 2016
Broad Institute, “What is CRISPR?” 2016
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