first reported that agonist anti-CD137 monoclonal antibodies can eradicate transplanted mouse tumors through enhanced CD8+ T-cell antitumor immunity over two decades ago (61), extensive studies have been conducted to evaluate the antitumor activity, toxicity, and mechanisms of anti-CD137 agonists and their combinations with other agents using syngeneic mouse tumor models, which greatly facilitated our understanding of CD137-targeted immunotherapies (55). This evidence concerns the gene CD8A and neoplasm.