Correale P, Walmsley K, Nieroda C, Zaremba S, Zhu M, Schlom J, Tsang K Y
Laboratory of Tumor Immunology and Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-1750, USA.
J Natl Cancer Inst. 1997 Feb 19;89(4):293-300. doi: 10.1093/jnci/89.4.293.
Protein antigens are presented to cytotoxic T lymphocytes as small peptides (approximately 9-10 amino acids long) bound to class I molecules of the major histocompatibility complex. The identification of tumor-associated antigens and specific peptide epitopes (i.e., antigenic determinants) may be useful in the development of anticancer vaccines. The generation of a cytotoxic T-cell response to one peptide epitope (amino acids 146-154) of human prostate-specific antigen (PSA) has been reported.
Our aim was to identify novel PSA peptides capable of eliciting specific cytotoxic T-cell responses.
Candidate peptides were identified on the basis of the following criteria: 1) they contained consensus amino acid motifs for binding to HLA-A2, which is the most common type of class I molecule; 2) they lacked strong homology with PSA-related kallikrein proteins; and 3) they were capable of stabilizing HLA-A2 class I molecules on the surface of human T2 (transport deletion mutant) cells, which are defective in antigen presentation. T-cell lines capable of killing (i.e., lysing) T2 target cells that had been pulsed with specific PSA peptides were generated from three different males (two disease-free individuals and one patient with prostate cancer) by incubating peripheral blood mononuclear cells with the peptides and interleukin 2. Specific cell lysis was monitored by the release of radioactivity from target cells that had been labeled with [111In]oxyquinoline.
Two novel PSA peptides capable of eliciting cytotoxic T-cell responses were identified; these peptides were designated PSA-1 (amino acids 41-150) and PSA-3 (amino acids 154-163). Four different cytotoxic T-cell lines were generated in response to these peptides-three against PSA-3 and one against PSA-1. Specific lysis of peptide-pulsed T2 cells by the T-cell lines was blocked by the addition of a monoclonal antibody directed against class I molecules. The T-cell lines were also capable of lysing PSA-positive, HLA-A2-positive LNCaP cells (human prostate carcinoma cells). The specificity of LNCaP cell lysis was shown by the following: 1) the inability of added human K562 (chronic myelogenous leukemia) cells to inhibit it, 2) the ability of added anti-HLA-A2 antibodies to block it, and 3) the inability of the T-cell lines to induce substantial lysis of PSA-negative, HLA-A2-positive human cancer cells.
Our studies form a rational basis for the use of PSA peptides or recombinant vectors encoding PSA in the development of anticancer vaccine immunotherapy protocols for patients with prostate cancer.
蛋白质抗原以与主要组织相容性复合体I类分子结合的小肽（约9 - 10个氨基酸长）形式呈递给细胞毒性T淋巴细胞。肿瘤相关抗原和特定肽表位（即抗原决定簇）的鉴定可能有助于抗癌疫苗的研发。据报道，已产生针对人前列腺特异性抗原（PSA）的一个肽表位（氨基酸146 - 154）的细胞毒性T细胞应答。
我们的目的是鉴定能够引发特异性细胞毒性T细胞应答的新型PSA肽。
根据以下标准鉴定候选肽：1）它们含有与HLA - A2结合的共有氨基酸基序，HLA - A2是最常见的I类分子类型；2）它们与PSA相关激肽释放酶蛋白缺乏高度同源性；3）它们能够稳定人T2（转运缺失突变体）细胞表面的HLA - A2 I类分子，T2细胞在抗原呈递方面存在缺陷。通过将外周血单核细胞与肽和白细胞介素2孵育，从三名不同男性（两名无病个体和一名前列腺癌患者）中产生能够杀死（即裂解）用特定PSA肽脉冲处理的T2靶细胞的T细胞系。通过从用[111In]氧喹啉标记的靶细胞中释放放射性来监测特异性细胞裂解。
鉴定出两种能够引发细胞毒性T细胞应答的新型PSA肽；这些肽被命名为PSA - 1（氨基酸41 - 150）和PSA - 3（氨基酸154 - 163）。针对这些肽产生了四种不同的细胞毒性T细胞系——三种针对PSA - 3，一种针对PSA - 1。通过添加针对I类分子的单克隆抗体可阻断T细胞系对肽脉冲处理的T2细胞的特异性裂解。T细胞系也能够裂解PSA阳性、HLA - A2阳性的LNCaP细胞（人前列腺癌细胞）。LNCaP细胞裂解的特异性通过以下几点得以证明：1）添加的人K562（慢性粒细胞白血病）细胞无法抑制它；2）添加的抗HLA - A2抗体能够阻断它；3）T细胞系无法诱导PSA阴性、HLA - A2阳性的人癌细胞大量裂解。
我们的研究为在前列腺癌患者的抗癌疫苗免疫治疗方案研发中使用PSA肽或编码PSA的重组载体奠定了合理基础。
