单核细胞来源的免疫耐受性IL-35+PD-L1+朗格汉斯细胞对黑素瘤早期抑制性微环境形成的促进作用及相关机制研究

It has been reported that different langerhans cell (LC) subsets play different roles in the early development and metastasis of melanoma. However, the phenotype and function of LC subset which exerts an immunotolerigenic effect on melanoma still remain unknown. Our previous findings demonstrated that epidermal resident rLC displayed a mature phenotype, while monocyte-derived LC (moLC) could transform to tolerigenic IL-35+PD-L1+tol-moLC which showed an immature phenotype after TGF-β treatment. As reported in previous investigations, IL-35-STAT1/3 signaling pathway could activate Breg and induce its autosecretion of IL-35. Meanwhile, STAT3 could combine with the promoter of PD-L1 gene and promote its transcription. Based on these results we speculated that IL-35+PD-L1+tol-moLC might enhance the autosecretion of IL-35 and increase the expression of PD-L1 through IL-35 positive feedback loop and the activation of IL-35-STAT3-PD-L1 signaling pathway. This could further induce the activation and proliferation of Treg as well as the suppression of CD8+CTL function, which leads to the development of melanoma suppressive microenvironment. We will further verify this hypothesis with the application of Langerin-DTR transgenic mouse model, LC subset knockout mouse model with monoclonal antibodies and clinical specimens to reach the aim of prevention of metastasis and improvement of therapeutic efficacy in the early phase of melanoma .

文献报道不同亚群朗格汉斯细胞(LC)在黑素瘤早期进展转移中具有不同作用，而其中可诱导黑素瘤免疫耐受的LC亚群表型和功能仍不明确。我们前期研究表明黑素瘤表皮定居rLC具成熟表型，而单核细胞来源的moLC经TGF-β诱导可转化为表型不成熟的免疫耐受性IL-35+PD-L1+tol-moLC。基于IL-35-STAT1/3通路可活化并促进Breg自分泌IL-35，且STAT3可与PD-L1启动子结合促进其转录的报道，我们推测IL-35+PD-L1+tol-moLC可通过IL-35正反馈环路和IL-35-STAT3-PD-L1信号通路促进IL-35自分泌和PD-L1表达，进而诱导Treg活化增殖并抑制CD8+CTL的功能，促进黑素瘤早期抑制性微环境形成。本研究拟通过Langerin-DTR转基因鼠、LC亚群抗体敲除鼠模型及临床标本验证上述假说，从而为预防黑素瘤早期转移和提高免疫治疗疗效提供新思路。

文献报道不同亚群朗格汉斯细胞(LC)在黑素瘤早期进展转移中具有不同作用，而其中可诱.导黑素瘤免疫耐受的LC亚群表型和功能仍不明确。我们发现，在肿瘤进展过程中，黑素瘤患者的肿瘤组织和肿瘤引流淋巴结中常驻LC（rLC）的数量减少，而单核细胞来源的LC (moLC)的数量增加。此外，与抗PD-1治疗有效的黑色素瘤患者相比，抗PD-1治疗耐药的黑素瘤患者肿瘤组织局部moLC数量更多。同时，通过利用muLangerin-DTR转基因小鼠模型和moLC条件性敲除小鼠模型，我们证明了清除rLC后黑色素瘤生长加速，而moLC耗竭可抑制黑素瘤进展。机制上，我们发现TGF-β和PGE2可诱导moLC的耐受表型和功能，特别是PGE2-AhR-COX2轴可促进moLC自分泌PGE2并上调其PD-L1的表达，进一步增强其对CD8+CTL的免疫抑制作用。我们的研究揭示了LC亚群在黑色素瘤进展中的功能异质性，从而进一步加深了我们对LC生物学的理解，也为黑素瘤早期抑制性免疫微环境的形成及免疫耐受机制提供新的理论基础。