Examining the relationship between KRAS mutation and immunotherapy resistance in colorectal cancer

Bowel cancer is the fourth most common cancer and the second most common cause of cancer death in the UK. The number of cases of bowel cancer diagnosed has increased by 6% over the last decade and most cases are diagnosed at a late stage. Further advancements in treatments strategies are therefore of utmost importance.

Immunotherapy is rapidly becoming a powerful tool for the treatment of human cancer. Immunotherapy refers to a broad range of drugs that are able to stimulate patients' immune response to target their cancer. Not all bowel cancers are alike however and in order to be successful it will be vital to determine which patients are most likely to respond. Differences are due to the type of mutations that patients have...

In a large number of cases of bowel cancer there is a mutation in the important protein KRAS. This mutation is thought to allow the cancer to hide from the immune system.

In this proposal, we will examine how KRAS mutation within bowel cancer cells prevents the success of immunotherapy drugs. Next we will aim to find drug treatments that will overcome this resistance allowing the development of combinations of immunotherapy drugs that will successfully treat these resistant cancers.

Aim: To examine the role of KRAS mutation in driving resistance to immunotherapy in colorectal cancer (CRC) and identify successful immunotherapy combinations for the treatment of CRC.

Objectives:
1. Characterise the immune infiltrate associated with KRAS mutation in syngeneic organoid and autochthonous mouse models, and human CRC.
2. Explore the factors regulating the variations in immune infiltrate between these mouse models of CRC.
3. Modulate the immune infiltrate in the above organoid models by novel combinations of immunotherapeutics (focussing on CXCR2 inhibition with cytokine inhibitors/checkpoint inhibitors) and determine the effects on organoid tumour growth and survival.
4. Take the best combination into autochthonous mouse models of CRC

Methodology:
To achieve this we will utilise a human TMA to characterise the immune infiltrate in human CRC in relation to RAS mutational status. We will further explore this relationship and factors controlling the immune composition with experiments in murine models of CRC of appropriate genetic backgrounds. Immune infiltrates will be characterised in all models via FACs, immunofluorescence, immunohistochemistry, RNAscope in situ hybridisation, and cytokine array analysis. Following these analyses, we will use guided combinations of immunotherapy agents in the same mouse models.

Scientific and medical opportunities:
Immunotherapy is rapidly becoming a powerful tool for the treatment of human cancer. One central unanswered question is which patients are most likely to respond. KRAS mutation is strongly immunosuppressive in human CRC. Our preliminary data suggest that Kras mutant syngeneic murine organoid transplantation models exhibit a similar immunosuppressive phenotype. Therefore we will examine the role mutant Kras plays in the resistance of CRC to immunotherapy agents, which in turn will reveal novel immunotherapy combinations vitally able to target previously resistant patients.

As the fourth most common cancer and the second most common cause of cancer death in the UK, and with approximately 27% of colorectal cancer (CRC) patients being under 64 years of age and part of the working population, CRC represents a disease with significant emotional and economic ramifications. The primary aim of this project is to develop targeted multimodal immunotherapy approaches which will have the potential to offer new treatment strategies for patients with colorectal cancer and in so doing provide treatments capable of significantly reducing the morbidity and mortality of this disease and contributing to increased productive life expectancy. Vitally with CRC being the third most common cancer worldwide the benefits of this research will impact far beyond the UK, enhancing quality of life, health and creative output globally.

These mechanisms of immune modulation will not be limited to this single cancer type. Therefore results obtained will contribute significantly to the wider and growing field of cancer immunology and immunotherapy. As such these results will ultimately have the potential, although indirectly, to benefit much larger and more diverse groups of patients than just those with CRC.

The success of a growing number of pharmaceutical compounds within the field of cancer immunotherapy will rely on accurately characterising the contexts in which specific compounds or combinations of compounds may be successful. The results of the proposed research will significantly contribute to the characterisation of these complex pathways and their links to potential biomarkers, including mutational status, thereby aiding healthcare professionals, regulators, and policy makers in accurately targeting these compounds to specific patient subsets and granting approval for their use due to proven clinical success and economic viability.

This research will have additional beneficiaries in the numerous private sector pharmaceutical companies that are developing the variety of compounds, including biologicals and small molecule inhibitors that are central to the immunotherapy armory. These include the PD-1 and CXCR2 inhibitors mentioned within this proposal.

Significant impact will also be felt by a wide range of academic beneficiaries outlined in the Academic Beneficiaries section of this proposal.

One important and significant aspect of the current proposal would be the immediate availability of the compounds used, a number of which are already available and in clinical use. This availability, along with the close ties with academic clinicians within the CRUK Beatson Institute and Glasgow as a whole, means that significant and translationally important findings will be easily and rapidly shared and if appropriate have the potential to benefit patients in a comparatively short time scale.

Successful research outputs from this project will also benefit CRUK by addressing a wide variety of the charities core aims. These include; contributing to an increased understanding of cancer, contributing to the personalisation of cancer treatment, contributing to the development of new treatments, and potentially due the wider potential of the results of this study contributing to the treatment of cancers of unmet need such as lung, pancreatic, and oesophageal cancers.

Finally, completing a PhD within this collaborative and multidisciplinary environment (including human pathologists) will allow me to grow as a research capable veterinary pathologist capable of dealing not only with laboratory animals generically but also with an increasing number of GEM models of human disease. Ultimately these skills will enable me to develop as a researcher capable of independently leading translational research whilst also continuing to significantly contribute, through expert consultancy and collaboration, to the research of others. Individuals with this set of skills are limited not only within the UK but worldwide.