Correale Pierpaolo, Del Vecchio Maria Teresa, Di Genova Giuseppa, Savellini Gianni Gori, La Placa Marco, Terrosi Chiara, Vestri Marzio, Urso Renato, Lemonnier Francois, Aquino Angelo, Bonmassar Enzo, Giorgi Giorgio, Francini Guido, Cusi Maria Grazia
Siena University School of Medicine, Viale Bracci 1, 53100 Siena, Italy.
J Natl Cancer Inst. 2005 Oct 5;97(19):1437-45. doi: 10.1093/jnci/dji188.
Thymidylate synthase (TS), a key enzyme in DNA synthesis, is often overexpressed in cancer cells. Some chemotherapeutic agents, such as 5-fluorouracil (5-FU), act by inhibiting TS expression. We evaluated whether a novel 28-amino acid multiepitope peptide, TS/PP, that contains the sequences of three TS-derived epitopes with binding motifs for HLA-A(*)02.01 could induce a TS-directed cytotoxic T-lymphocyte (CTL) response with antitumor activity.
TS/PP peptide immunologic activity in CTL lines derived from human leukocyte antigen (HLA)-A()02.01+ peripheral blood mononuclear cells (PBMCs) was tested in the presence of interleukin-2 and autologous TS/PP peptide-loaded dendritic cells. Immunologic and antitumor activities of TS/PP and its toxicity were also evaluated in vivo in HLA-A()02.01 transgenic (HHD) mice that were vaccinated with TS/PP, control, or TS-peptide cocktail and treated with or without 5-FU chemotherapy. The mice were also inoculated subcutaneously with TS-expressing EL-4/HHD lymphoma cells to assess immune response against these tumor cells.
TS/PP-specific CTL lines showed a TS-multiepitopic specificity and were able to kill TS+/HLA-A(*)02.01+ breast and colon carcinoma cells. The killing ability against target cells previously exposed to sublethal doses of 5-FU was statistically significantly greater than against untreated target cells (43.5% versus 26.5% at 25/1 effector to target ratio [Difference {diff} = 17.0]; 95% confidence interval [CI] = 12.6 to 20.4) for MDA-MB-231 breast carcinoma cells and 73.5 versus 48.5 (diff = 25.0; 95% CI = 16.2 to 33.8) for the SW-1463 colon carcinoma cells. HHD mice vaccinated with TS/PP manifested a TS-peptide-specific CTL response with no sign of autoimmunity or toxicity. Furthermore, treatment of these mice with 5-FU delayed or prevented the occurrence of tumors formed by inoculation with autologous (TS+)EL-4/HHD lymphoma cells.
The multiepitopic TS/PP vaccine induces a tumor-specific immune response in mice and is especially potent when used in combination with 5-FU-based chemotherapy.
胸苷酸合成酶（TS）是DNA合成中的关键酶，在癌细胞中常过度表达。一些化疗药物，如5-氟尿嘧啶（5-FU），通过抑制TS表达发挥作用。我们评估了一种新型的28个氨基酸的多表位肽TS/PP，其包含三个TS衍生表位的序列以及与HLA-A（*）02.01的结合基序，是否能诱导具有抗肿瘤活性的针对TS的细胞毒性T淋巴细胞（CTL）反应。
在白细胞介素-2和自体负载TS/PP肽的树突状细胞存在的情况下，测试TS/PP肽在源自人类白细胞抗原（HLA）-A（）02.01+外周血单个核细胞（PBMC）的CTL系中的免疫活性。还在HLA-A（）02.01转基因（HHD）小鼠体内评估了TS/PP的免疫和抗肿瘤活性及其毒性，这些小鼠接种了TS/PP、对照或TS肽混合物，并接受或不接受5-FU化疗。小鼠还皮下接种表达TS的EL-4/HHD淋巴瘤细胞，以评估针对这些肿瘤细胞的免疫反应。
TS/PP特异性CTL系表现出TS多表位特异性，能够杀伤TS+/HLA-A（*）02.01+乳腺癌和结肠癌细胞。对于MDA-MB-231乳腺癌细胞，在效应细胞与靶细胞比例为25/1时，对先前暴露于亚致死剂量5-FU的靶细胞的杀伤能力在统计学上显著高于未处理的靶细胞（分别为43.5%对26.5%[差异{diff}=17.0]；95%置信区间[CI]=12.6至20.4）；对于SW-1463结肠癌细胞，该比例为73.5%对48.5%（diff=25.0；95%CI=16.2至33.8）。接种TS/PP的HHD小鼠表现出TS肽特异性CTL反应，无自身免疫或毒性迹象。此外，用5-FU治疗这些小鼠可延迟或预防接种自体（TS+）EL-4/HHD淋巴瘤细胞形成的肿瘤的发生。
多表位TS/PP疫苗在小鼠中诱导肿瘤特异性免疫反应，与基于5-FU的化疗联合使用时尤其有效。
