Rapid modelling of cooperating genetic events in cancer through somatic genome editing

The CRISPR/Cas system has been used in mice for genome editing to introduce genetic alterations found in human lung tumours, and these genome modifications resulted in mouse lung tumours showing different histopathologies depending on the genes altered; the CRISPR/Cas system offers improved and faster ways to create animal models of human diseases such as cancer. The bacterial CRISPR/Cas9 system allows rapid and precise genome editing of somatic cells and is proving a useful tool for the generation of mouse models of human disease. Two groups reporting in this issue of Nature have now used the technique to introduce genetic alterations found in human lung tumours into the lungs of mice. Danilo Maddalo et al. introduce the Eml4–Alk rearrangement into mouse lung and find that the resulting EML4–ALK fusion protein drives the development of lung tumours with histopathology similar to that seen in human lung cancers carrying this alteration. Moreover, they show that an inhibitor of the ALK kinase leads to tumour regression. Francisco Sànchez-Rivera et al. show that loss-of-function of several known tumour suppressor genes cooperates with other genetic alterations in promoting the development of lung cancer. Different combinations of genetic alterations cause lung tumours with distinct molecular and histopathological features. These studies demonstrate the power of the CRISPR/Cas9 system to probe the function of putative oncogenes and tumour suppressor genes in mouse models more rapidly than previous approaches. Cancer is a multistep process that involves mutations and other alterations in oncogenes and tumour suppressor genes1. Genome sequencing studies have identified a large collection of genetic alterations that occur in human cancers2,3,4. However, the determination of which mutations are causally related to tumorigenesis remains a major challenge. Here we describe a novel CRISPR/Cas9-based approach for rapid functional investigation of candidate genes in well-established autochthonous mouse models of cancer. Using a KrasG12D-driven lung cancer model5, we performed functional characterization of a panel of tumour suppressor genes with known loss-of-function alterations in human lung cancer. Cre-dependent somatic activation of oncogenic KrasG12D combined with CRISPR/Cas9-mediated genome editing of tumour suppressor genes resulted in lung adenocarcinomas with distinct histopathological and molecular features. This rapid somatic genome engineering approach enables functional characterization of putative cancer genes in the lung and other tissues using autochthonous mouse models. We anticipate that this approach can be used to systematically dissect the complex catalogue of mutations identified in cancer genome sequencing studies.