Resistance of the stable—towards more precise prediction of response to immune checkpoint blockade in microsatellite-unstable cancer patients

The introduction of immune checkpoint blockade into the clinical practice has marked a milestone for treating patients with advanced microsatellite-unstable (MSI) cancer (1,2). MSI tumors are evolving with a deficiency of the DNA mismatch repair (MMR) system and therefore accumulate numerous somatic mutations during every cell division, resulting in a very high mutational load in the manifest tumors (3,4).