Conceptual illustration of the use of CRISPR-Cas9 gene editing to treat lung cancer. Researchers are trialling CRISPR-Cas9-modified cells for the treatment of lung cancer. To treat lung cancer the CRISPR-Cas9 protein (white) uses a guide RNA (ribonucleic acid, grey) sequence to cut DNA (deoxyribonucleic acid, green) at a complementary site in T-cell white blood cells harvested from the patient. The modified cells are injected back into the patient where it is hoped they will target and destroy tumour cells.