Barren R J, Holmes E H, Boynton A L, Misrock S L, Murphy G P
Cancer Research Division, Northwest Hospital, Seattle, Washington, USA.
Prostate. 1997 Jan 1;30(1):65-8. doi: 10.1002/(sici)1097-0045(19970101)30:1<65::aid-pros10>3.0.co;2-n.
Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein defined by the monoclonal antibody 7E11.C5. The 7E11.C5 antibody forms the basis of an in vivo diagnostic imaging agent (ProstaScint, Cyt-356) for identification of metastatic prostate cancer. The epitope on PSMA recognized by 7E11.C5 has been determined to be the first 6 amino acids from the N-terminal, expressed on the cytoplasmic side of the plasma membrane. Thus, the basis for 7E11.C5 specificity in imaging studies remains unclear.
Fluorescence-activated cell sorter (FACS) analysis of fixed and viable cultured cells was used to determine the staining intensity with FITC-labeled antibodies.
The results indicate that FITC-labeled 7E11.C5 antibody is taken up and specifically labels viable LNCaP cells in vitro. Labeling intensity of viable cells after 2 hr of antibody incubation was similar to that of fixed cells. No labeling of cells that do not express PSMA was observed, nor was labeling observed with LNCaP cells treated with an isotype-matched irrelevant antibody.
Uptake and labeling of PSMA by FITC-labeled 7E11.C5 in viable cells in vitro strongly suggest that this is a major basis for effectiveness of the 7E11.C5 antibody during in vivo imaging applications with 111In-labeled antibody (ProstaScint, Cyt-356).
前列腺特异性膜抗原（PSMA）是一种由单克隆抗体7E11.C5定义的跨膜糖蛋白。7E11.C5抗体构成了一种用于识别转移性前列腺癌的体内诊断成像剂（ProstaScint，Cyt-356）的基础。已确定7E11.C5识别的PSMA上的表位是来自N端的前6个氨基酸，在质膜的细胞质侧表达。因此，7E11.C5在成像研究中的特异性基础仍不清楚。
使用荧光激活细胞分选仪（FACS）对固定和活的培养细胞进行分析，以确定用异硫氰酸荧光素（FITC）标记的抗体的染色强度。
结果表明，FITC标记的7E11.C5抗体在体外被摄取并特异性标记活的LNCaP细胞。抗体孵育2小时后活细胞的标记强度与固定细胞相似。未观察到不表达PSMA的细胞的标记，用同型匹配的无关抗体处理的LNCaP细胞也未观察到标记。
FITC标记的7E11.C5在体外活细胞中对PSMA的摄取和标记强烈表明，这是7E11.C5抗体在使用111In标记抗体（ProstaScint，Cyt-356）进行体内成像应用时有效性的主要基础。
