Horiguchi Yutaka, Nukaya Ikuei, Okazawa Kazuhide, Kawashima Ichiro, Fikes John, Sette Allesandro, Tachibana Masaaki, Takesako Kazutoh, Murai Masaru
Department of Urology, School of Medicine, Keio University, Tokyo 160-8582, Japan.
Clin Cancer Res. 2002 Dec;8(12):3885-92.
Prostate-specific membrane antigen (PSMA), which is a transmembrane glycoprotein predominantly expressed in prostate cancer, is an attractive target for tumor-specific immunotherapy. To identify human leukocyte antigen (HLA)-A24-restricted epitope peptides from PSMA for further application of the dendritic cell (DC)-based immunotherapy targeting prostate cancer, we have screened several PSMA-encoded HLA-A24-binding peptides for their capabilities to elicit specific antitumor CTL response in vitro.
The amino acid sequence of PSMA was screened for peptides consisting of 9 or 10 amino acids, which possess the known HLA-A24-binding motif. Nine candidate peptides were screened for binding to HLA-A24 molecules. Then, each of these nine peptides was studied to determine whether CTL responses could be induced by primary in vitro immunization of CD8(+) T cells using peptide-pulsed autologous DCs derived from peripheral blood mononuclear cells of HLA-A24(+) healthy donor as antigen-presenting cells. The antigen specificity of the CTL lines was confirmed using several tumor cell lines as target cells, which were genetically modified to express both HLA-A24 and PSMA.
Two peptides, LYSDPADYF and NYARTEDFF, were demonstrated to elicit CTL lines that lyse peptide-pulsed, HLA-A24(+) B-lymphoblastoid cells. Each of the CTL lines recognized their specific PSMA-expressing target cells in a HLA-A24-restricted manner. The capability to release IFN-gamma by the CTL lines was specifically inhibited by anti-MHC class I and anti-CD8 monoclonal antibodies but not by anti-MHC class II and anti-CD4 monoclonal antibodies.
Two novel HLA-A24-restricted PSMA-derived epitopes were identified in this study. These epitopes can be used to further evaluate the clinical utility of DC-based immunotherapeutic strategies for treatment of hormone-refractory prostate cancers.
前列腺特异性膜抗原（PSMA）是一种主要在前列腺癌中表达的跨膜糖蛋白，是肿瘤特异性免疫治疗的一个有吸引力的靶点。为了从PSMA中鉴定出人白细胞抗原（HLA）-A24限制性表位肽，以便进一步应用基于树突状细胞（DC）的前列腺癌免疫治疗，我们筛选了几种PSMA编码的HLA-A24结合肽，以评估它们在体外引发特异性抗肿瘤CTL反应的能力。
筛选PSMA的氨基酸序列，寻找由9个或10个氨基酸组成且具有已知HLA-A24结合基序的肽。筛选9种候选肽与HLA-A24分子的结合情况。然后，研究这9种肽中的每一种，以确定使用从HLA-A24(+)健康供体的外周血单个核细胞中获得的肽脉冲自体DC作为抗原呈递细胞，对CD8(+)T细胞进行体外初次免疫是否能诱导CTL反应。使用几种经过基因改造以同时表达HLA-A24和PSMA的肿瘤细胞系作为靶细胞，确认CTL系的抗原特异性。
两种肽，LYSDPADYF和NYARTEDFF，被证明能引发裂解肽脉冲的、HLA-A24(+)B淋巴母细胞的CTL系。每个CTL系以HLA-A24限制性方式识别其特异性表达PSMA的靶细胞。CTL系释放IFN-γ的能力被抗MHC I类和抗CD8单克隆抗体特异性抑制，但不被抗MHC II类和抗CD4单克隆抗体抑制。
本研究鉴定出两种新的HLA-A24限制性PSMA衍生表位。这些表位可用于进一步评估基于DC的免疫治疗策略治疗激素难治性前列腺癌的临床效用。
