Tsang Kwong-Yok, Palena Claudia, Gulley James, Arlen Philip, Schlom Jeffrey
Laboratory of Tumor Immunology and Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892, USA.
Clin Cancer Res. 2004 Mar 15;10(6):2139-49. doi: 10.1158/1078-0432.ccr-1011-03.
MUC-1/DF-3 remains an attractive target for vaccine therapy. It is overexpressed in the majority of human carcinomas and multiple myeloma. Clinical trials using MUC-1-based vaccines have demonstrated safety, clinical responses, and the induction of T-cell responses directed against MUC-1. Previous studies in experimental models and in clinical trials have demonstrated that altering the amino acid sequence of a "self" epitope can lead to the generation of an enhancer agonist epitope capable of eliciting stronger T-cell responses than the native epitope can.
We describe here the identification of six novel class I HLA-A2 epitopes of MUC-1 that reside outside of the variable number of tandem repeat region. Each is shown to have the ability to activate human T cells as measured by IFN-gamma production. One epitope (ATWGQDVTSV, at amino acid position 92-101 and designated P-92), which demonstrated the highest level of binding to HLA-A2 and which induced the highest level of IFN-gamma in human T cells, was further studied for the generation of potential enhancer agonist epitopes. Of four potential agonists identified, one epitope (ALWGQDVTSV, designated P-93L) was identified as an enhancer agonist. Compared with the native P-92 peptide, the P-93L agonist (a). bound HLA-A2 at lower peptide concentrations, (b). demonstrated a higher avidity for HLA-A2 in dissociation assays, (c). when used with antigen-presenting cells, induced the production of more IFN-gamma by T cells than with the use of the native peptide, and (d). was capable of more efficiently generating MUC-1-specific human T-cell lines from normal volunteers and pancreatic cancer patients. Most importantly, the T-cell lines generated using the agonist epitope were more efficient than those generated with the native epitope in the lysis of targets pulsed with the native epitope and in the lysis of HLA-A2 human tumor cells expressing MUC-1.
In addition to the identification of novel MUC-1 epitopes outside the variable number of tandem repeat region, the studies reported here describe the first agonist epitope of MUC-1. The employment of this agonist epitope in peptide-, protein-, and vector-based vaccines may well aid in the development of effective vaccines for a range of human cancers.
MUC-1/DF-3仍然是疫苗治疗的一个有吸引力的靶点。它在大多数人类癌症和多发性骨髓瘤中过表达。使用基于MUC-1的疫苗的临床试验已证明其安全性、临床反应以及针对MUC-1的T细胞反应的诱导。先前在实验模型和临床试验中的研究表明，改变“自身”表位的氨基酸序列可导致产生一种增强激动剂表位，该表位能够引发比天然表位更强的T细胞反应。
我们在此描述了在MUC-1可变串联重复区域之外鉴定出的六个新的I类HLA-A2表位。通过干扰素-γ产生检测，每个表位都显示出激活人类T细胞的能力。对一个表位（ATWGQDVTSV，位于氨基酸位置92-101，命名为P-92）进行了进一步研究，该表位与HLA-A2的结合水平最高，并且在人类T细胞中诱导的干扰素-γ水平最高，以产生潜在的增强激动剂表位。在鉴定出的四个潜在激动剂中，一个表位（ALWGQDVTSV，命名为P-93L）被鉴定为增强激动剂。与天然P-92肽相比，P-93L激动剂（a）在较低肽浓度下与HLA-A2结合，（b）在解离试验中对HLA-A2表现出更高的亲和力，（c）与抗原呈递细胞一起使用时，比使用天然肽诱导T细胞产生更多的干扰素-γ，并且（d）能够更有效地从正常志愿者和胰腺癌患者中产生MUC-1特异性人类T细胞系。最重要的是，使用激动剂表位产生的T细胞系在裂解用天然表位脉冲的靶细胞以及裂解表达MUC-1的HLA-A2人类肿瘤细胞方面比使用天然表位产生的T细胞系更有效。
除了在可变串联重复区域之外鉴定出新的MUC-1表位外，本文报道的研究还描述了MUC-1的首个激动剂表位。在基于肽、蛋白质和载体的疫苗中使用这种激动剂表位可能有助于开发针对一系列人类癌症的有效疫苗。
