嵌合抗原受体（CAR）修饰的T细胞（CAR-T）在固体肿瘤中受到恶劣的肿瘤微环境（TME）的限制。联合疗法可能是克服此障碍的有希望方法。最近的研究显示，鞘脂1磷酸受体（S1PR）3在调节免疫环境方面具有巨大潜力。然而，S1PR3在T细胞免疫疗法中的功能意义和分子机制尚未完全理解。在这里，我们研究了EpCAM特异性CAR T细胞疗法与S1PR3药物阻断的固体肿瘤联合治疗。我们应用了RNA测序、流式细胞术、ELISA、细胞/分子免疫技术和固体癌症的小鼠模型。我们的研究提供了证据表明，S1PR3的高表达与抗PD-1免疫疗法的耐药性和T细胞衰竭增加呈正相关。此外，S1PR3的药物抑制改善了抗PD-1疗法的疗效。接下来，我们探讨了S1PR3拮抗剂与小鼠EpCAM靶向CAR-T细胞在体外和体内的可能联合应用，在乳腺癌和结肠癌的免疫能力正常的小鼠模型中进行了实验。结果表明，在体外和体内，S1PR3拮抗剂显著增强了小鼠EpCAM CAR-T细胞的疗效。在机制上，S1PR3拮抗剂在体外改善了CAR-T细胞的激活，调节了中央记忆表型，并减少了CAR-T细胞的衰竭。通过促进巨噬细胞的活化和促炎性表型极化，靶向S1PR3可重塑TME，通过招募促炎性巨噬细胞，改善CAR-T细胞浸润并增加CD8+T细胞的招募。该研究证明，靶向S1PR3能够通过抑制T细胞衰竭和重塑TME招募促炎性巨噬细胞，增加CAR-T细胞疗法的抗肿瘤活性。这些发现为结合S1PR3抑制剂与CAR-T细胞治疗固体肿瘤提供了进一步的理据。© 作者（或其雇主）2023。根据CC BY-NC许可进行复用。不允许商业复用。由BMJ出版。

Chimeric antigen receptor (CAR)-modified T cells (CAR-T) are limited in solid tumors due to the hostile tumor microenvironment (TME). Combination therapy could be a promising approach to overcome this obstacle. Recent studies have shown that sphingosine 1-phosphate receptor (S1PR)3 has tremendous potential in regulating the immune environment. However, the functional significance of S1PR3 in T-cell-based immunotherapies and the molecular mechanisms have not been fully understood.Here, we studied the combination of EpCAM-specific CAR T-cell therapy with pharmacological blockade of S1PR3 against solid tumor. We have applied RNA sequencing, flow cytometry, ELISA, cellular/molecular immunological technology, and mouse models of solid cancers.Our study provided evidence that S1PR3 high expression is positively associated with resistance to programmed cell death protein-1 (PD-1)-based immunotherapy and increased T-cell exhaustion. In addition, pharmacological inhibition of S1PR3 improves the efficacy of anti-PD-1 therapy. Next, we explored the possible combination of S1PR3 antagonist with murine EpCAM-targeted CAR-T cells in immunocompetent mouse models of breast cancer and colon cancer. The results indicated that the S1PR3 antagonist could significantly enhance the efficacy of murine EpCAM CAR-T cells in vitro and in vivo. Mechanistically, the S1PR3 antagonist improved CAR-T cell activation, regulated the central memory phenotype, and reduced CAR-T cell exhaustion in vitro. Targeting S1PR3 was shown to remodel the TME through the recruitment of proinflammatory macrophages by promoting macrophage activation and proinflammatory phenotype polarization, resulting in improved CAR-T cell infiltration and amplified recruitment of CD8+T cells.This work demonstrated targeting S1PR3 could increase the antitumor activities of CAR-T cell therapy at least partially by inhibiting T-cell exhaustion and remodeling the TME through the recruitment of proinflammatory macrophages. These findings provided additional rationale for combining S1PR3 inhibitor with CAR-T cells for the treatment of solid tumor.© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.