ARTICLE ABSTRACT
Neoadjuvant immunotherapy, given before surgical resection, is a promising approach to develop systemic antitumor immunity for the treatment of high-risk resectable disease. Here, using syngeneic and orthotopic mouse models of triple-negative breast cancer, we have tested the hypothesis that generation of tumor-specific T-cell responses by induction and activation of tumor-residing Batf3-dependent conventional type 1 dendritic cells (cDC1) before resection improves control of distant metastatic disease and survival. Mice bearing highly metastatic orthotopic tumors were treated with a combinatorial in situ immunomodulation (ISIM) regimen comprised of intratumoral administration of Flt3L, local radiotherapy, and in situ TLR3/CD40 stimulations, followed by surgical resection. Neoadjuvant ISIM (neo-ISIM) generated tumor-specific CD8+ T cells that infiltrated into distant nonirradiated metastatic sites, which delayed the progression of lung metastases and improved survival after the resection of primary tumors. The efficacy of neo-ISIM was dependent on de novo adaptive T-cell immunity elicited by Batf3-dependent dendritic cells and was enhanced by increasing dose and fractionation of radiotherapy, and early surgical resection after the completion of neo-ISIM. Importantly, neo-ISIM synergized with programmed cell death protein-1 ligand-1 (PD-L1) blockade to improve control of distant metastases and prolong survival, while removal of tumor-draining lymph nodes abrogated the antimetastatic efficacy of neo-ISIM. Our findings illustrate the therapeutic potential of neoadjuvant multimodal intralesional therapy for the treatment of resectable tumors with high risk of relapse.
Neoadjuvant induction and activation of cDC1s in primary tumors enhances systemic antitumor immunity, suppresses metastatic progression, improves survival, and synergizes with anti–PD-L1 therapy.
