Elsässer-Beile Ursula, Wolf Philipp, Gierschner Dorothee, Bühler Patrick, Schultze-Seemann Wolfgang, Wetterauer Ulrich
Department of Urology, Experimental Urology, University of Freiburg, Freiburg, Germany.
Prostate. 2006 Sep 15;66(13):1359-70. doi: 10.1002/pros.20367.
Prostate-specific membrane antigen (PSMA) is an excellent candidate for targeting prostate cancer by virtue of its restricted expression on prostatic epithelial cells and its upregulation on prostatic carcinoma cells. PSMA is expressed on the cell surface displaying a specific three-dimensional structure. Therefore, only antibodies with a high cell binding activity will have an important impact on antibody-based imaging and therapy.
Monoclonal antibodies (mAbs) and single chain antibody fragments (scFvs) were prepared from spleen cells of mice that had been immunized either with purified PSMA or a cell lysate of prostate cancer LNCaP cells containing native PSMA. mAbs and scFvs were screened for reactivity with purified PSMA and binding to PSMA-expressing LNCaP cells.
From mice immunized with purified PSMA, we obtained three mAbs (K7, K12, D20) and four scFvs (G0, G1, G2, G4), which were highly reactive with the isolated antigen, but showed weak or no reaction with viable LNCaP cells. From mice immunized with unpurified LNCaP lysate, we obtained three mAbs (3/E7, 3/F11, 3/A12), and one scFv (A5), which were reactive with purified PSMA, also showing a strong and specific binding to viable LNCaP cells and PSMA-transfected cells.
Our results suggest that only the mAbs and scFvs, that were elicited with unpurified LNCaP lysate and not with purified PSMA will be useful agents for diagnostic imaging and therapeutic applications of prostate cancer.
前列腺特异性膜抗原（PSMA）因其在前列腺上皮细胞上的限制性表达以及在前列腺癌细胞上的上调，是靶向前列腺癌的极佳候选物。PSMA在细胞表面表达，呈现特定的三维结构。因此，只有具有高细胞结合活性的抗体才会对基于抗体的成像和治疗产生重要影响。
从用纯化的PSMA或含有天然PSMA的前列腺癌LNCaP细胞裂解物免疫的小鼠脾细胞中制备单克隆抗体（mAb）和单链抗体片段（scFv）。筛选mAb和scFv与纯化的PSMA的反应性以及与表达PSMA的LNCaP细胞的结合。
在用纯化的PSMA免疫的小鼠中，我们获得了三种mAb（K7、K12、D20）和四种scFv（G0、G1、G2、G4），它们与分离的抗原高度反应，但与活的LNCaP细胞反应较弱或无反应。在用未纯化的LNCaP裂解物免疫的小鼠中，我们获得了三种mAb（3/E7、3/F11、3/A12）和一种scFv（A5），它们与纯化的PSMA反应，也显示出与活的LNCaP细胞和PSMA转染细胞的强特异性结合。
我们的结果表明，只有用未纯化的LNCaP裂解物而非纯化的PSMA诱导产生的mAb和scFv才是前列腺癌诊断成像和治疗应用的有用试剂。
