Xing P X, Tjandra J J, Reynolds K, McLaughlin P J, Purcell D F, McKenzie I F
Department of Pathology, University of Melbourne, Parkville, Victoria, Australia.
J Immunol. 1989 May 15;142(10):3503-9.
The nucleotide sequence of partial cDNA clones coding for the core protein of a human polymorphic epithelial mucin has recently been obtained, this mucin consists of a highly conserved 60 bp tandem repeat and the amino acids commonly found are PDTRPAPGSTAPPAHGVTSA. We synthesized three peptides, 1) P1.24 containing the 20 amino acids and four amino acids (PDTR) of the adjoining repeat; 2) P1.15 consisting of the first fifteen (PDTRPAPGSTAPPAH) and P1.09 the second nine amino acids (GVTSAPDTR) of peptide P1.24. The reactivities of the synthetic peptides with mAb known to react with breast cancer (BC1, BC2, BC3, HMFG-1, 3E1.2, and RCC-1) were studied. The synthetic peptide, P1.24, corresponding to the antigenic sequence predicted from the tandem repeat reacted with antibodies BC1, BC2, and BC3 (known to react with human milk mucin and mucin expressed in breast cancer) and the antibody HMFG-1 which was used to select the cDNA clones. In addition, the epitopes recognized by BC1, BC2, and BC3 appear to be in the same region of the molecule represented by their reactions with the nine amino acids in peptide P1.09 (GVTSAPDTR). By contrast, other antibodies such as 3E1.2 which reacts only weakly with components of human milk, and RCC-1 that detects a low Mr component (95 kDa) in breast cancer, had no specific reaction with the synthetic peptides, indicating that their epitopes are distinct from those of BC1, BC2, BC3, and HMFG-1. Inasmuch as the antibodies HMFG-1, BC1, BC2, and BC3 react with the fully processed milk mucin, it is likely that some of the peptide is exposed, even in the fully glycosylated molecule. Identification of the different epitopes could lead to the development of "second generation" mAb with enhanced specificity for breast carcinoma using the appropriate synthetic peptides as immunogens.
最近已获得编码人多形上皮粘蛋白核心蛋白的部分cDNA克隆的核苷酸序列，这种粘蛋白由一个高度保守的60bp串联重复序列组成，常见的氨基酸序列为PDTRPAPGSTAPPAHGVTSA。我们合成了三种肽：1）P1.24，包含20个氨基酸以及相邻重复序列的四个氨基酸（PDTR）；2）P1.15，由肽P1.24的前十五个氨基酸（PDTRPAPGSTAPPAH）组成；3）P1.09，由肽P1.24的后九个氨基酸（GVTSAPDTR）组成。研究了这些合成肽与已知可与乳腺癌反应的单克隆抗体（BC1、BC2、BC3、HMFG-1、3E1.2和RCC-1）的反应性。与串联重复序列预测的抗原序列相对应的合成肽P1.24与抗体BC1、BC2和BC3（已知可与人乳粘蛋白和乳腺癌中表达的粘蛋白反应）以及用于筛选cDNA克隆的抗体HMFG-1发生反应。此外，BC1、BC2和BC3识别的表位似乎在分子的同一区域，这可通过它们与肽P1.09中的九个氨基酸（GVTSAPDTR）的反应来体现。相比之下，其他抗体，如仅与人乳成分弱反应的3E1.2，以及检测乳腺癌中低分子量成分（95kDa）的RCC-1，与合成肽没有特异性反应，这表明它们的表位与BC1、BC2、BC3和HMFG-1的表位不同。由于抗体HMFG-1、BC1、BC2和BC3可与完全加工的乳粘蛋白反应，即使在完全糖基化的分子中，某些肽段也可能暴露在外。鉴定不同的表位可能会促使开发“第二代”单克隆抗体，这些抗体以适当的合成肽作为免疫原，对乳腺癌具有更高的特异性。
