A Microsatellite in the Coding Sequence of HLA-A/B is a Mutation Hotspot in Colon Cancer with Microsatellite Instability

During the last 5 years, the treatment of colorectal carcinomas (CRCs) with microsatellite instability (MSI) has been revolutionized by the introduction of immune-checkpoint inhibitors (ICIs).1 This novel class of antitumor drugs includes anti-programmed cell death 1 (PD1) and anti-programmed cell death 1 ligand 1 (PD-L1) monoclonal antibodies and functions by releasing T cells from inhibitory signals, thus unleashing powerful immune responses.2 In malignancies characterized by high numbers of somatic mutations, such as CRCs with MSI, widespread activation of endogenous T cells can result in profound antitumor activity, but also cause severe autoimmune toxicities.