Arisato et al. found that the LLC-2B2 subclone of LLC was universally rejected in ICB-treated WT mice and was also rejected in 36% of ICB-treated Batf3-/- mice. In Batf3-/- mice, rejection was dependent on CD8+ T cells primed by alternative XCR1- APCs, which upregulated costimulatory CD80, CD86, and CD40 in response to soluble factors secreted by LLC-2B2 cells. However, when mice that had cleared LLC-2B2 tumors were rechallenged, all WT mice rejected tumors, while most Batf3-/- mice did not, suggesting that cDC1s were important in establishing protective immune memory. Intratumoral injection of Flt3L-DCs restored protection from rechallenge.
Arisato et al. found that the LLC-2B2 subclone of LLC was universally rejected in ICB-treated WT mice and was also rejected in 36% of ICB-treated Batf3-/- mice. In Batf3-/- mice, rejection was dependent on CD8+ T cells primed by alternative XCR1- APCs, which upregulated costimulatory CD80, CD86, and CD40 in response to soluble factors secreted by LLC-2B2 cells. However, when mice that had cleared LLC-2B2 tumors were rechallenged, all WT mice rejected tumors, while most Batf3-/- mice did not, suggesting that cDC1s were important in establishing protective immune memory. Intratumoral injection of Flt3L-DCs restored protection from rechallenge.
Contributed by Lauren Hitchings
ABSTRACT: Immune checkpoint blockade (ICB) provides durable therapeutic responses across multiple cancer types. Although crosstalk between T cells and conventional type 1 dendritic cells (cDC1s) is essential, the contribution of other antigen-presenting cells (APCs) to ICB-induced tumor rejection remains unclear. To address this, we show that while the majority of wild type (WT) mice rejected an immunogenic clone of Lewis lung carcinoma (LLC) following ICB, 35.7% of Batf3–/– mice, which lack the cDC1 subset, also rejected this LLC clone. ICB induced the upregulation of costimulatory markers on XCR1– APCs in the tumors and lymph nodes of Batf3–/– mice, similar to responses observed in wild-type mice. Mechanistically, conditioned culture media from LLC, but not from ICB-resistant B16F10 melanoma cells, stimulated bone marrow-derived cDC1s and cDC2s, as evidenced by the upregulation of CD40 and CD80 expression. RNA sequencing revealed that antitumor immunity-related genes were upregulated in LLC cells compared with B16F10 cells. To determine the role of cDC1-independent long-term immune memory, we rechallenged ICB-induced tumor-free mice with LLC tumors. We found that, without supplementation of cDC1s during primary rejection, Batf3–/– mice failed to spontaneously reject the rechallenged tumors. These findings demonstrate that ICB can elicit primary antitumor T cell responses against immunogenic tumors in the absence of cDC1s, whereas cDC1s are essential for the establishment of ICB-induced long-term memory. Our study underscores the importance of clinical strategies targeting both cDC1-dependent and cDC1-independent pathways to enhance the durable efficacy of ICB.
Author Info:
1. Department of Medical Oncology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan 2. Department of Respiratory Medicine, Faculty of Medici
ne, Hokkaido University, Sapporo, Japan 3. Department of Medical Oncology, Shinshu Cancer Center, Shinshu University Hospital, Matsumoto, Japan 4. Division of Molecular Psychoimmunology, Institute for Genetic Medicine, Hokkaido University, Sapporo, Japan 5. Department of Medical Oncology, Hokkaido University Hospital, Sapporo, Japan 6. Division of Clinical Cancer Genomics, Hokkaido University Hospital, Sapporo, Japan 7. Quantum immunology Team, Institute for Quantum Life science, National Institute for Quantum and Radiological Science and Technology (QST), Chiba, Japan 8. Division of Molecular Neuroimmunology, Department of Homeostatic Regulation, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Aichi, Japan 9. Institute for Vaccine Research and Development, Hokkaido University, Sapporo 001-0021, Japan
