Department of Dermatology, Xijing Hospital, Fourth Military Medical University, 710032 Xi'an, China.
Cancer Immunol Immunother. 2011 Aug;60(8):1109-18. doi: 10.1007/s00262-011-1025-3. Epub 2011 May 6.
The forkhead transcription factor Foxp3 is the only definitive marker of CD4(+)CD25(+) regulatory T cells (Tregs) and has been identified as a key regulator in the development and function of Tregs. Foxp3 expression has been reported in a variety of solid tumors, including melanoma. In this study, we validated Foxp3 expression in both tumor-infiltrating Tregs and melanoma cells by performing immunohistochemical analysis of human melanoma tissue sections. Further, we assessed Foxp3 expression in melanoma cell lines by performing flow cytometry, confocal microscopic analysis, reverse transcription-polymerase chain reaction (RT-PCR), and Western blotting. Inhibition of Foxp3 expression in melanoma cells using small interfering RNA (siRNA) resulted in downregulation of B7-H1 and transforming growth factor (TGF)-β expression; in contrast, Foxp3 overexpression resulted in the upregulation of the expression of these proteins. Coculture of Foxp3-expressing melanoma cells with naive CD4(+)CD25(-) T cells resulted in strong inhibition of T-cell proliferation. This antiproliferative effect was partially abrogated by specific inhibition of Foxp3 expression and was effectively enhanced by overexpression of Foxp3. We observed an attenuated antiproliferative effect even when melanoma cells and T cells in the coculture were separated using Transwell inserts. These findings indicated that melanoma cells could have Foxp3-dependent Treg-like suppressive effects on T cells and suggested that the mimicking of Treg function by melanoma cells may represent a possible mechanism of tumor resistance to immune destruction in the melanoma tumor microenvironment.
叉头框转录因子 Foxp3 是 CD4(+)CD25(+)调节性 T 细胞（Tregs）的唯一明确标志物，被认为是 Tregs 发育和功能的关键调节因子。Foxp3 表达已在多种实体瘤中得到报道，包括黑色素瘤。在这项研究中，我们通过对人类黑色素瘤组织切片进行免疫组织化学分析，验证了肿瘤浸润性 Tregs 和黑色素瘤细胞中 Foxp3 的表达。此外，我们通过流式细胞术、共聚焦显微镜分析、逆转录-聚合酶链反应（RT-PCR）和 Western blot 分析评估了黑色素瘤细胞系中 Foxp3 的表达。使用小干扰 RNA（siRNA）抑制黑色素瘤细胞中的 Foxp3 表达导致 B7-H1 和转化生长因子（TGF）-β表达下调；相反，Foxp3 过表达导致这些蛋白的表达上调。Foxp3 表达的黑色素瘤细胞与幼稚 CD4(+)CD25(-)T 细胞共培养导致 T 细胞增殖强烈抑制。通过特异性抑制 Foxp3 表达部分阻断了这种增殖抑制作用，而过表达 Foxp3 则有效增强了这种作用。我们观察到，即使在共培养中使用 Transwell 插入物将黑色素瘤细胞和 T 细胞分离，也会减弱这种抗增殖作用。这些发现表明黑色素瘤细胞可能对 T 细胞具有 Foxp3 依赖性 Treg 样抑制作用，并表明黑色素瘤细胞模拟 Treg 功能可能代表黑色素瘤肿瘤微环境中肿瘤对免疫破坏的抵抗的一种可能机制。
