Choosing the right cell-based screen from the plethora of options available can quickly become a complicated decision process. Here, we review two of the major options: cell panel and functional genomic screening. Cell panel screening provides drug response data across panels of genomically diverse cell lines from different tissue types. These screens can provide evidence of drug resistance and sensitivity; aid selection of efficacious drugs for treatment of a specific disease; stratify patients for clinical trials; repurpose drugs with clinically acceptable profiles and provide data to inform mechanism of action (MoA) studies. Functional Genomic Screening (FGS), where RNAi or CRISPR is used to modify gene expression, can also address many similar questions to cell panel screens, but from a genetic point of view. In addition, FGS can be used to find and validate novel drug targets, identify the genetic basis of drug resistance or sensitivity, and identify genetic dependencies (often referred to as synthetic lethality).
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.
When I have read articles just like this one early on in my career, I would laugh and categorize it with blogs regarding Bigfoot and the Loch Ness Monster. However, much has changed in the past 10 years. New technologies have been developed and milestones have been reached that should have Cancer a little worried. These 3 steps might be viewed to some as obvious, but I argue that it’s how the researchers have utilized the technology wisely that has made the difference. I have identified some papers that have carved a successful path to Cancer's possible demise.
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 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.