MRC1 and neoplasm: The following key differences were observed: 1/ RPM tumors exhibited MMR deficiency, a high tumor mutational burden (TMB), and an elevated load of candidate neoantigens compared to RP lesions, suggesting enhanced immunogenicity; 2/ The time from tumor manifestation to death was substantially shortened for animals with MMR-defective tumors, indicating increased aggressiveness; and 3/ The overall survival of RPM animals was significantly improved when exposed to ICI.