Department of Medical Oncology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, The Netherlands.
Clin Cancer Res. 2011 Feb 15;17(4):841-8. doi: 10.1158/1078-0432.CCR-10-2227. Epub 2010 Dec 21.
Regulatory T cells (Tregs) are thought to inhibit antitumor immune responses, and their depletion could therefore have a synergistic effect with therapeutic cancer vaccines. We investigated the impact of three medications on blood Treg frequency in vaccinated cancer patients.
To date, the most specific marker for human Tregs is demethylation in the DNA that encodes the transcription factor FOXP3. Thus, we used a FOXP3 methylation-specific quantitative PCR assay (MS-qPCR) to measure Treg frequencies in the peripheral blood mononuclear cells (PBMCs) of melanoma patients. The patients participated in three clinical trials that combined tumor vaccines with potential Treg-depleting agents: low-dose cyclophosphamide, anti-CD25 monoclonal antibody daclizumab, and the IL-2/diphtheria toxin fusion protein denileukin diftitox.
In the nine control patients, blood Treg frequencies varied over time; there was a 46% reduction in one patient. In treated patients, a more than 2-fold decrease in Tregs was observed in one out of 11 patients receiving cyclophosphamide and in four out of 13 receiving daclizumab, but there was no such Treg decrease in any of the six patients who received denileukin diftitox. As a positive control, a more than 2-fold increase in blood Tregs was detected in four out of nine patients who were treated with interleukin-2.
We used a MS-qPCR method that detects Tregs but not other activated T lymphocytes; however, none of the Treg-depleting strategies that we tested led, in the majority of patients, to a conservative 50% reduction in blood Tregs.
调节性 T 细胞（Tregs）被认为能抑制抗肿瘤免疫反应，因此其耗竭可能与治疗性癌症疫苗具有协同作用。我们研究了三种药物对接种癌症疫苗患者血液 Treg 频率的影响。
迄今为止，用于鉴定人类 Tregs 的最特异标志物是编码转录因子 FOXP3 的 DNA 去甲基化。因此，我们使用 FOXP3 甲基化特异性定量 PCR 检测（MS-qPCR）来检测黑素瘤患者外周血单个核细胞（PBMC）中的 Treg 频率。这些患者参与了三项临床试验，这些试验将肿瘤疫苗与潜在的 Treg 耗竭剂联合应用：低剂量环磷酰胺、抗 CD25 单克隆抗体达利珠单抗和 IL-2/白喉毒素融合蛋白 denileukin diftitox。
在 9 名对照患者中，血液 Treg 频率随时间变化；1 名患者降低了 46%。在治疗患者中，11 名接受环磷酰胺治疗的患者中有 1 名，13 名接受达利珠单抗治疗的患者中有 4 名患者的 Tregs 减少了两倍以上，但在接受 denileukin diftitox 的 6 名患者中没有出现这种 Treg 减少。作为阳性对照，在接受白细胞介素 2 治疗的 9 名患者中有 4 名患者血液 Tregs 增加了两倍以上。
我们使用了一种 MS-qPCR 方法，该方法可检测 Tregs 而不能检测其他激活的 T 淋巴细胞；然而，我们测试的所有 Treg 耗竭策略都没有导致大多数患者血液 Tregs 保守减少 50%。
