Neoantigens Are Critical Targets in Naturally and Therapeutically Induced Immune Responses to Cancer

: T cells are critical effector immune cells, and mutation-derived neoantigens are critical tumor-specific antigens in natural immune responses to cancer(cancer immunosurveillance). However, the underlying mechanisms are poorly understood, particularly in the human clinical setting, such as how many tumor antigens are related to cancer elimination and whether immunodominance of antigens exist in humans. Furthermore, it is unclear whether specific T cells recognizing neoantigens can control cancer for a long time in an equilibrium state. Cancer immunotherapy including immune checkpoint inhibitors (ICIs)such as PD-1 and CTLA-4 blockades has attracted much attention for cancer treatment, but they remain effective only in a minority of patients. However, the efficacy of ICIs, which is characterized by long term durable responses has suggested that host immunity, if re-activated, can eliminate cancer cells or maintain cancer for a long time(therapeutically induced cancer immune elimination or equilibrium). Recent reports show that the loss of neoantigens has occurred at the DNA and RNA level as results of both naturally and therapeutically induced tumor-specific immune responses, leading to tumor immune escape(re-escape). Here we focus on the role of neoantigens in naturally and therapeutically induced immunoediting revealed by cancer immunogenomics approaches utilizing clinical samples to develop effective neoantigen-based cancer immunotherapies.