Pre-Existing Immunity Shapes Cancer Immunotherapy Efficacy

Immunotherapy has revolutionized the management of patients with cancer. Immune checkpoint inhibition (ICI) is a promising treatment option that targets the molecular mechanisms that cancer cells exploit to prevent immune-mediated elimination. ICI therapy can cause exceptional long-term tumor remissions, in some cases, even after treatment discontinuation. Despite its success, many patients acquire resistance or fail to respond due to immune escape mechanisms mediated by the tumor and its microenvironment. Pre-existing immunity status of individuals seems to play a fundamental role in immunotherapy response and eventually tumor progression, as it orchestrates tumor-immune interactions. Different immune cell subsets, both in the tumor microenvironment and the peripheral blood, are established mediators that contribute to immune escape in various tumor types. Based on these findings, the elucidation of the mechanisms implicated in the regulation of these immune cells has become a priority for investigators focused on improving the efficacy of ICI. This will be essential for identifying responders as well as for developing novel therapeutic modalities to improve clinical outcomes. Herein, we summarize preclinical and clinical evidence proposing a predictive role of pre-existing immunity for clinical responses to immunotherapies.