A Chinese group of scientists has become the first to inject a person with edited genes using the revolutionary and still controversial CRISPR-Cas9 technique.

Key points: CRISPR-Cas9 can trim away unwanted parts of the genome

CRISPR-Cas9 can trim away unwanted parts of the genome A protein that slows down the cell's immune response was trimmed out of the DNA

A protein that slows down the cell's immune response was trimmed out of the DNA The edited DNA was cultivated and injected back into the patient

A patient with aggressive lung cancer received the modified cells as part of a clinical trial at the West China Hospital in Chengdu.

A team led by oncologist Lu You at Chengdu's Sichuan University removed immune cells from the patient's blood and disabled a gene in them using the CRISPR technique.

The technique combines a DNA-cutting enzyme with a molecular guide that can be programmed to tell the enzyme exactly where to cut.

It works as a type of molecular scissors that can selectively trim away unwanted parts of the genome and replace it with new stretches of DNA.

The disabled gene codes for the protein PD-1, which slows down the cell's immune response.

Cancers take advantage of this protein and its function to generate.

The team then cultured the edited cells, increasing their number, and injected them back into the patient.

The hope is that, without PD-1, the edited cells will attack and defeat the cancer.

The patient is set to get a second injection, but further treatment details are covered by doctor-patient confidentiality.

The trial will treat a total of 10 people who will receive between two to four injections.

Participants will be monitored for six months to determine whether the injections are causing serious adverse effects.

They will also be observed beyond that time to see if they seem to be benefitting from the treatment.

A group at Peking University in Beijing hopes to start three clinical trials using CRISPR against bladder, prostate and renal-cell cancers in March 2017, but those trials do not yet have approval or funding.

Ethical clearance for controversial technique

Dr Lu's trial received ethical approval for the project from a hospital review board in July and the clinical trial has excited clinicians.

Although there have already been other forms of gene editing to treat disease in people, Dr Lu's CRISPR trial breaks new ground by modifying three different sites in the genome at once.

CRISPR has quickly become the preferred method of gene editing in research labs because of its ease of use compared with older techniques.

But the ability to tinker with genes can be considered controversial, and there are certain ethical considerations for using technologies such as CRISPR.

The rapid uptake in biotech research has some scientists concerned that we're racing ahead with experiments before knowing the full implications of the technology.