A new therapy targeting genomic rearrangements, such as fused genes that promote tumor development, significantly improved survival in mice with aggressive forms of prostate and liver cancer. The study, “Targeting genomic rearrangements in tumor cells through Cas9-mediated insertion of a suicide gene,” was published in the journal Nature Biotechnology. “This is the first time that gene editing has been used to specifically target cancer fusion genes. It is really exciting because it lays the groundwork for what could become a totally new approach to treating cancer,” the study's lead author, Dr. Jian-Hua Luo, said in a press release. The pathology professor directs the High Throughput Genome Center at the University of Pittsburgh School of Medicine. Fusion genes occur when two genes, which normally are separated, fuse to create an abnormal gene with altered functions. Fusion genes are often associated with cancer, but targeting them to develop a cancer treatment has been difficult. In a previous study, Luo and his team identified a set of fusion genes that promote recurrent and aggressive prostate cancer. The MAN2A1-FER gene, which promotes cancer progression and invasiveness, is also present in other cancers, including those of the liver, lungs and ovaries. Using CRISPR-Cas9 genome editing technology, researchers targeted DNA sequences in a fused gene that was in prostate and liver cancer cells. They used viruses to deliver the genome editing tools to the cells. The editing process involved replacing the fused DNA with a gene that could trigger the death of the cancer cell. They edited only cancer cells for death, leaving healthy cells unharmed. That targeting would be crucial to doctors being able to use editing to treat cancer patients.