B2M and neoplasm: In this work, we describe powerful anti-tumor responses resulting from mIL12 mRNA treatment of MHC class I-deficient, syngeneic allograft models, YUMMER 1.7 B2M knockout melanoma (Yummer B2M KO) and MC38 B2M knockout colorectal carcinoma (MC38 B2M KO), both of which were engineered by CRISPR knockout of the beta-2 microglobulin gene (B2M KO).