Currently, cancer immunotherapies, especially immune checkpoint blockade and ACT, represent a new paradigm in tumor management.[38, 39] Despite considerable advances, they provide only limited clinical benefits to the majority of CRC patients.[40] A major hurdle for satisfactory immunotherapies is that the tumor immunoenvironment lacks sufficient cytotoxic T‐cell tumor infiltration.[41, 42, 43] This study showed that mutant KRAS caused poor persistence of tumor‐infiltrating cytotoxic T‐cells, which was in accord with poor immunotherapy efficacy. Here, KRAS is linked to cancer.