To investigate immunoediting in human tumors, Borden et al. analyzed primary, treatment-naive cSCC tumors, which frequently arise in immunosuppressed patients following solid organ transplant, suggesting immune involvement. Compared to tumors from immunodeficient patients or just poorly infiltrated tumors, tumors from immunocompetent patients with high infiltration showed lower overall and clonal mutation burdens, and a lower frequency of variant alleles with high predicted neoantigen:MHC-I binding affinity. Further, neoantigens that shared features with validated immunogenic neoantigens were decreased in clonal versus subclonal cancer cells.
Contributed by Lauren Hitchings
ABSTRACT: T cell targeting of cancer cells alters the tumor antigen landscape in preclinical models. Here, we examined the impact of immunoediting on the antigenic landscape of primary, treatment-naive human tumors. Cutaneous squamous cell carcinoma tumors from immunocompetent and immunosuppressed patients revealed consistent tumor mutational signatures; however, high-immune-infiltrate tumors from immunocompetent patients had lower overall mutational burdens and lower clonal mutational burdens compared with low-infiltrate tumors from immunocompetent patients and tumors from immunosuppressed patients. The lower clonal mutational burden in high-immune-infiltrate tumors from immunocompetent patients persisted after accounting for tumor purity and growth rate. Predicted neoantigen: major histocompatibility complex (MHC) class I binding affinity decreased with increasing variant allele frequency, demonstrating restriction of mutations encoding MHC-binding neoantigens. Neoantigens with features shared with validated immunogenic neoantigens were decreased in clonal relative to subclonal cancer cell populations in high-immune-infiltrate tumors from immunocompetent patients. Thus, the immune system restricts cancer cells expressing immunogenic antigens from clonal populations in primary, treatment-naive human tumors.
