Trp53 Mutation-Mediated mTORC1 Inhibition and Inflammation Suppression Confer Resistance to Checkpoint Immunotherapy

p53 is a critical tumor suppressor gene that inhibits cancer development by regulating cell cycle arrest, apoptosis, DNA repair, and metabolism. However, recent studies examining TP53 mutations in cancer immunotherapy have yielded inconsistent results, likely due to differences in tumor mutational burden (TMB) and the context-dependent roles of specific p53 mutants. In this study, we assessed the function of G242V and S258I Trp53 mutations in MC38 cells in the context of immunotherapy by generating Trp53 deletion and observed significantly enhanced responses to anti-PD-1 therapy. We next characterized how the Trp53 deletion in MC38 tumor cells alters the immune response. To this end, we performed single-cell RNA and paired single-cell TCR sequencing (scRNAseq and scTCRseq) of anti-PD-1 treated Trp53CON and Trp53KO MC38 tumors on day 11 after tumor cells inoculation. CRISPR-Cas9 was used to knockout p53 in the MC38 tumor cell line. WT and KO MC38 cells were inoculated into C57BL/6J mice and treated with anti-PD-1 immune checkpoint blockade therapy.