Background: The expansion of intratumoral stem-like CD8⁺ T (Tstem) cells provides a potential approach to improving the therapeutic efficacy of immune checkpoint blockade (ICB). Thus, here we demonstrate a strategy to facilitate Tstem cell expansion by combining an alarmin high-mobility group nucleosome binding domain 1 (HMGN1) peptide with programmed death-ligand 1 (PD-L1) blockade. Methods: The antitumor effects of HMGN1, anti-PD-L1 antibody, and their combined treatment were monitored in the B16F10, LLC, Colon26, or the EO771 tumor-bearing mice. The comprehensive immunologic analyses, such as high-dimensional flow cytometry, transcriptome analysis, and single-cell RNA sequencing, were used to investigate the cellular and molecular mechanisms of antitumor immune responses after treatments. Results: The HMGN1 peptide synergizes with PD-L1 blockade in augmenting the number of mature DCs enriched in immunoregulatory molecules (mregDCs) in tumors, and enhancing their MHC class I antigen-presenting program, which is correlated with the expansion of intratumoral Tstem cells, specifically promoting the Tstem cells but restricting terminally exhausted CD8⁺ T (Tex) cells, owing to the regulatory molecules expressed on mregDCs. Conclusion: Our results indicate that HMGN1 peptide serves as an immunoadjuvant to promote effective anti-PD-L1 immunotherapy and implicate that mregDCs play a role beyond facilitating Tstem cell expansion.

中文翻译：

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将Alarmin HMGN1肽与PD-L1阻断剂结合使用可促进干细胞样CD8 + T细胞扩增并产生强大的抗肿瘤作用

背景：肿瘤内干细胞样CD8 ⁺ T（Tstem）细胞的扩增为提高免疫检查点封锁（ICB）的治疗效果提供了一种潜在途径。因此，在这里，我们展示了通过将alallin高迁移率基团核小体结合结构域1（HMGN1）肽与程序性死亡配体1（PD-L1）阻断相结合来促进Tstem细胞扩增的策略。方法：在B16F10，LLC，Colon26或EO771荷瘤小鼠中监测了HMGN1，抗PD-L1抗体及其组合治疗的抗肿瘤作用。全面的免疫学分析，例如高维流式细胞术，转录组分析和单细胞RNA测序，用于研究治疗后抗肿瘤免疫反应的细胞和分子机制。结果：HMGN1肽与PD-L1阻断剂协同作用，增加了肿瘤中富含免疫调节分子（mregDCs）的成熟DC的数量，并增强了其MHC I类抗原呈递程序，这与肿瘤内Tstem细胞的扩增有关，专门促进Tstem细胞但限制最终耗尽的CD8 ⁺T（Tex）细胞，由于在mregDCs上表达的调控分子。结论：我们的结果表明，HMGN1肽可作为免疫佐剂，以促进有效的抗PD-L1免疫疗法，并暗示mregDCs的作用不只是促进Tstem细胞的扩增。