KRAS is one of the most frequently mutated genes in cancer, but targeting KRAS with potent small molecules has proved to be difficult. Moreover, although inhibitors of BRAF and MEK, which are downstream targets of KRAS, have been developed, they have transient benefits only in patients with melanoma who have mutated BRAF. Therefore, an effective therapy for KRAS-driven tumours remains a pressing unmet medical need.
The discovery of the CRISPR‐Cas system in bacteria has initiated an impressive array of innovations that have enabled the use of the RNA‐guided Cas9 nuclease in functional genomic screens. At Horizon, we have embraced these developments, as they provide new opportunities for drug target identification and validation. The case studies presented in this below highlight how we use this technology to successfully conduct genome wide and focused sgRNA library screens and to verify whether specific genes are required for the survival and/or proliferation of cancer cell lines.
The emergence of RAS mutations is a key mechanism of acquired resistance to MAPK-pathway targeted agents in a number of cancers. The preclinical evaluation of targeted agents traditionally relies on panels of genetically unrelated cell lines grown as 2D monocultures. The heterogeneous nature of these panels makes identifying genotype-specific responses a challenge. In addition, 2D assays do not accurately mimic the tumour microenvironment and so add to the difficulty in interpreting which cellular responses to targeted agents will have relevance in vivo.
Ras mutations are amongst the most commonly occurring mutations in human cancer, present in approximately 49% of colorectal and 20% of lung cancers. Of these, mutations in K-Ras G12 and G13 are the most common. Understanding the role of mutant K-Ras in modulating drug response is critical to the successful development of novel therapeutics, and has been hampered by the lack of suitable in vitro tools.