Developing New Immunotherapy Approaches for Colorectal Cancer

Immunotherapy represents a groundbreaking approach for treating colorectal cancer (CRC), harnessing the body's own immune system to target tumour cells more precisely than conventional chemotherapy. Immune checkpoint inhibitors, such as antibodies against PD-1, PD-L1, or CTLA-4, have shown remarkable efficacy in certain patients, leading to durable responses and improved survival. However, the majority of CRC cases have limited benefit from a single agent checkpoint blockade. There is a growing need to identify biomarkers that will improve the selection of patients who will best respond to therapy, as well as new targets to sensitise cancers to an immune checkpoint blockade. Unfortunately, the search for reliable biomarkers has been limited by our incomplete understanding of how immunotherapies modify the already complex immune response to cancer. Revolutionary techniques, such as genome-wide CRISPR/Cas9 screening combined with the appropriate validation systems such as in vivo mouse models and/or 3D organoid co-culture systems, are being used to address this knowledge gap. This review will focus on the use of immunotherapies in CRC, discuss why most CRC patients do not respond, and highlight in vitro, in vivo, and novel techniques for discovery of new targets for combination treatment.