Cancer drug discovery targeting the interaction of RAS oncogenic proteins with phosphoinositide 3-kinase

Lead Research Organisation: The Francis Crick Institute
Department Name: Research

Abstract

It is estimated by Cancer Research UK that there are 17 million people developing cancer worldwide each year - which sadly causes 9.6 million death annually, making cancer one of the deadliest diseases of our time. Cancer remains a very challenging disease to cure despite the significant research effort that has been made through several decades. This is because cancer is a complex disease that is caused by multiple genetic mutations that occur in important cellular proteins - named oncogenic proteins. Oncogenic proteins are proteins that once mutated become hyperactive and causes several types of cancer. They contribute in the signaling and activation of several cellular pathways that are involved in cellular growth and proliferation. One of the major oncogenic protein families that causes almost 20% of human cancer is the RAS family of proteins. RAS proteins oscillate between two states, ON and OFF. The ON state of RAS interacts with several downstream enzymes to control cellular growth and proliferation. Oncogenic mutations in RAS lock it into the ON state, which causes constant and uncontrolled cellular growth and several types of cancers. Since the discovery of RAS protein in the 1980s, many efforts have been made to find inhibitors against oncogenic RAS. However, RAS proteins are challenging drug targets, despite the development of inhibitors that target one specific RAS mutation, G12C, which only represents 14% of total RAS oncogenic mutations. Therefore, applying new strategies that targets oncogenic-RAS mutants is an urgent requirement.
Previous work in the Downward laboratory at the Francis Crick Institute (Crick) has established that blocking the interaction of RAS proteins with a particular downstream target enzyme named p110a inhibits tumour growth driven by RAS oncogenes in mice. Importantly blocking the KRAS/p110a interaction had no toxic effects in normal adult mice. These studies strongly support the idea that the complex of RAS with p110a protein may be an important drug target for future cancer therapies. Although these results are very encouraging, the nature of the weak RAS/p110a interaction makes it difficult to use available screening assays to discovery novel inhibitory chemicals which might be developed into drugs for treating cancers. We therefore initiated a collaboration with the pharmaceutical company AstraZeneca to develop a suitable screening assay for the RAS/p110a interaction. This was successfully achieved, resulting in a joint publication between the Crick and AstraZeneca in 2020.
This secondment will strengthen our already successful collaboration with AstraZeneca and enable us to take the project to the next stage. I will apply the newly developed assay system to carry out high throughput screening of libraries of millions of chemical compounds to identify inhibitors that blocks RAS/p110a interaction. By combining expertise from two world class organisations - from academia, the Crick and from the pharmaceutical industry, AstraZeneca - we will maximise the chances of success for the project. Finding inhibitors that blocks the RAS/p110a interaction could lead the way to developing future treatments for all cancers driven by oncogenic RAS mutations, or around 20% of all human cancers.

Technical Summary

The RAS family of proteins are activated by mutation in some 20% of human cancers. Constitutively activated mutant RAS proteins stimulate downstream proliferative signalling pathways through effector enzymes such as PI3K and RAF kinases, thereby contributing to the genesis of several types of cancer. RAS proteins remain challenging drug targets, despite the development of inhibitors that target one specific RAS mutation, G12C in KRAS, which represents 14% of total RAS oncogenic mutations. Previous work in the Downward laboratory at the Crick has established that blocking the interaction of RAS proteins with the effector enzyme p110a, a member of the PI3K lipid kinase family, inhibits tumour growth driven by RAS oncogenes in mice with minimal toxicity.
In collaboration with AstraZeneca, we have previously developed a cell free assay to measure the interaction of KRAS with p110a (NanoBiT Biochemical Assay - NBBA). This has been optimised for high throughput screening. In this proposal, we wish to second Dr Mohamed Ismail from the Crick to AstraZeneca for two years. During this time he will 1) use the NBBA for high throughput screening of AstraZeneca compound libraries for inhibitors of KRAS/p110a interaction. 2) We will counter screen these hits against RAS interaction with other isoforms of PI3K, such as p110g and p110d. 3) Promising compounds will be followed up by secondary screening for direct interaction with purified RAS or p110a, using nano-format Differential Scanning Fluorimetry. 4) Hits of interest will initially be mapped onto the p110a or RAS protein crystal structure computationally and confirmed by site directed mutagenesis. Further structural follow up may involve co-crystallization of compounds with RAS/p110a. Any promising compounds will be checked for effects on RAS and PI3K signaling in cell lines. Subsequent medicinal chemistry to improve the chemical characteristics of compounds of interest may be initiated at the end of the granting period.

Publications

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