RT Journal Article SR Electronic T1 Novel insights into paclitaxel’s role on tumor-associated macrophages in enhancing PD-1 blockade in breast cancer treatment JF Journal for ImmunoTherapy of Cancer JO J Immunother Cancer FD BMJ Publishing Group Ltd SP e008864 DO 10.1136/jitc-2024-008864 VO 12 IS 7 A1 Choi, Yoonjeong A1 Kim, Seong A A1 Jung, Hanul A1 Kim, Eunhae A1 Kim, Yoon Kyoung A1 Kim, Seohyun A1 Kim, Jaehyun A1 Lee, Yeji A1 Jo, Min Kyoung A1 Woo, Jiwan A1 Cho, Yakdol A1 Lee, Dongjoo A1 Choi, Hongyoon A1 Jeong, Cherlhyun A1 Nam, Gi-Hoon A1 Kwon, Minsu A1 Kim, In-San YR 2024 UL http://jitc.bmj.com/content/12/7/e008864.abstract AB Background Triple-negative breast cancer (TNBC) poses unique challenges due to its complex nature and the need for more effective treatments. Recent studies showed encouraging outcomes from combining paclitaxel (PTX) with programmed cell death protein-1 (PD-1) blockade in treating TNBC, although the exact mechanisms behind the improved results are unclear.Methods We employed an integrated approach, analyzing spatial transcriptomics and single-cell RNA sequencing data from TNBC patients to understand why the combination of PTX and PD-1 blockade showed better response in TNBC patients. We focused on toll-like receptor 4 (TLR4), a receptor of PTX, and its role in modulating the cross-presentation signaling pathways in tumor-associated macrophages (TAMs) within the tumor microenvironment. Leveraging insights obtained from patient-derived data, we conducted in vitro experiments using immunosuppressive bone marrow-derived macrophages (iBMDMs) to validate if PTX could augment the cross-presentation and phagocytosis activities. Subsequently, we extended our study to an in vivo murine model of TNBC to ascertain the effects of PTX on the cross-presentation capabilities of TAMs and its downstream impact on CD8+ T cell-mediated immune responses.Results Data analysis from TNBC patients revealed that the activation of TLR4 and cross-presentation signaling pathways are crucial for the antitumor efficacy of PTX. In vitro studies showed that PTX treatment enhances the cross-presentation ability of iBMDMs. In vivo experiments demonstrated that PTX activates TLR4-dependent cross-presentation in TAMs, improving CD8+ T cell-mediated antitumor responses. The efficacy of PTX in promoting antitumor immunity was elicited when combined with PD-1 blockade, suggesting a complementary interaction.Conclusions This study reveals how PTX boosts the effectiveness of PD-1 inhibitors in treating TNBC. We found that PTX activates TLR4 signaling in TAMs. This activation enhances their ability to present antigens, thereby boosting CD8+ T cell antitumor responses. These findings not only shed light on PTX’s immunomodulatory role in TNBC but also underscore the potential of targeting TAMs’ antigen presentation capabilities in immunotherapy approaches.All data relevant to the study are included in the article or uploaded as online supplemental information. All data are available in the main text or online supplemental materials. Publicly available datasets can be accessed with the accession numbers GSE176078 and GSE169246. The code used for processing and analysis is available on request.