Lymphodepleting preconditioning impairs host antitumor immunity induced by adoptive T cell therapy in mouse models

Adoptive T cell therapy (ACT) is effective against hematologic cancers, but the mechanisms underlying durable responses in solid tumors remain unclear. We show that adoptively transferred CD8⁺ T cells that eradicate established murine tumors promote expansion of host CD8⁺ T cells exhibiting tumor-reactive and tissue-resident phenotypes that contribute to tumor elimination. Mechanistically, tumor necrosis factor (TNF) from transferred cells induces dendritic cell (DC)-dependent expansion of host CD8⁺ T cells, conferring protection against ACT-resistant tumor cells lacking the targeted antigen. Lymphodepleting preconditioning promotes expansion of transferred cells and primary tumor eradication but impairs host antitumor immunity and abrogates protection against ACT-resistant tumors. In human tumors, increased TNF/DC/CD8⁺ T cell profiles correlate with favorable ACT responses and improved survival. These findings reveal a TNF-dependent interplay between transferred and host CD8⁺ T cells underlying durable antitumor immunity that is impaired by lymphodepleting preconditioning in mouse models, suggesting an underappreciated mechanism of ACT resistance.