在黑色素瘤中,肿瘤细胞对免疫抑制的诱导和炎性抗肿瘤反应都可以诱导反调节机制的上调,如吲哚胺2,3-双加氧酶(IDO),肿瘤微环境中的程序性死亡配体1(PD-L1)和CTLA-4+调节性T细胞(Tregs)。尽管这些免疫抑制介质是免疫治疗的目标,缺乏研究它们在外周血中的表达。因此,我们,对I-IV期黑色素瘤患者的PBMC进行流式细胞术。在浆细胞样树突状细胞(pDC)和单核细胞髓源性抑制细胞(mMDSC)中检测到IDO表达,在疾病晚期阶段增加(p=0.027)。色氨酸分解证实了IDO的功能活性,并与PD-L1+细胞毒性T细胞增加有关(p=0.009),相对淋巴细胞减少(p=0.036),和更高的mDC/pDC比(p=0.002)。高水平的循环PD-L1+细胞毒性T细胞与通过Tregs(p=0.005)和MDSC水平(p=0.033)增加的CTLA-4表达相关。这说明黑素瘤中的反调节免疫机制应被视为一个相互关联的信号传导网络。此外,Tregs中PD-L1+T细胞和CTLA-4表达增加均为阴性预后,表明它们在体内的相关性。值得注意的是,循环CTLA-4,IDO,pDC水平根据前哨淋巴结的浸润而改变,前哨淋巴结中IDO的表达与更多IDO+PBMC相关。我们得出结论,IDO的表达,黑色素瘤患者外周血中的PD-L1和CTLA-4密切相关,与晚期疾病和阴性结果相关,独立于疾病阶段。因此,靶向这些标志物中的几种的组合治疗可能发挥协同反应。
In melanoma, both the induction of immunosuppression by tumor cells and the inflammatory antitumor response can induce an upregulation of counter-regulatory mechanisms such as indoleamine 2,3-dioxygenase (IDO), programmed death-ligand 1 (PD-L1) and CTLA-4+ regulatory T-cells (Tregs) in the tumor microenvironment. Even though these immunosuppressive mediators are targets for immunotherapy, research investigating their expression in the peripheral blood is lacking. We therefore, performed flow cytometry on PBMCs of stage I-IV melanoma patients. IDO expression was detected in plasmacytoid dendritic cells (pDC) and monocytic myeloid-derived suppressor cells (mMDSC), and increased in advanced disease stage (p = 0.027). Tryptophan breakdown confirmed the functional activity of IDO and was linked with increased PD-L1+ cytotoxic T-cells (p = 0.009), relative lymphopenia (p = 0.036), and a higher mDC/pDC ratio (p = 0.002). High levels of circulating PD-L1+ cytotoxic T-cells were associated with increased CTLA-4 expression by Tregs (p = 0.005) and MDSC levels (p = 0.033). This illustrates that counter-regulatory immune mechanisms in melanoma should be considered as one interrelated signaling network. Moreover, both increased PD-L1+ T-cells and CTLA-4 expression in Tregs conferred a negative prognosis, indicating their in vivo relevance. Remarkably, circulating CTLA-4, IDO, and pDC levels were altered according to prior invasion of the sentinel lymph node and IDO expression in the sentinel was associated with more IDO+ PBMCs. We conclude that the expression of IDO, PD-L1, and CTLA-4 in the peripheral blood of melanoma patients is strongly interconnected, associated with advanced disease and negative outcome, independent of disease stage. Combination treatments targeting several of these markers are therefore likely to exert a synergistic response.