MUC1/X protein immunization enhances cDNA immunization in generating anti-MUC1 α/β junction antibodies that target malignant cells

Daniel B. Rubinstein, Maya Karmely, Ravit Ziv, Itai Benhar, Orit Leitner, Shoshana Baron, Ben Zion Katz, Daniel H. Wreschner

Research output: Contribution to journalArticlepeer-review

Abstract

MUC1 has generated considerable interest as a tumor marker and potential target for tumor killing. To date, most antibodies against MUC1 recognize epitopes within the highly immunogenic α chain tandem repeat array. A major shortcoming of such antibodies is that the MUC1 α chain is shed into the peripheral circulation, sequesters circulating anti-tandem repeat array antibodies, and limits their ability to even reach targeted MUC1-expressing cells. Antibodies recognizing MUC1 epitopes tethered to the cell surface would likely be more effective. MUC1 α subunit binding the membrane-tethered β subunit provides such an epitope. By use of a novel protocol entailing immunization with cDNA encoding full-length MUC1 (MUC1/TM) followed by boosting with the alternatively spliced MUC1/X isoform from which the tandem repeat array has been deleted, we generated monoclonal antibodies, designated DMC209, which specifically bind the MUC1 α/β junction. DMC209 is exquisitely unique for this site; amino acid mutations, which abrogate MUC1 cleavage, also abrogate DMC209 binding. Additionally, DMC209 specifically binds the MUC1 α/β junction on full-length MUC1/TM expressed by breast and ovarian cancer cell lines and on freshly obtained, unmanipulated MUC1-positive malignant plasma cells of multiple myeloma. DMC209 is likely to have clinical application by targeting MUC1-expressing cells directly and as an immunotoxin conjugate. Moreover, the novel immunization procedure used in generating DMC209 can be used to generate additional anti-MUC1 α/β junction antibodies, which may, analogously to Herceptin, have cytotoxic activity. Lastly, sequential immunization with MUC1/TM cDNA acting as a nonspecific adjuvant followed by protein of interest may prove to be a generalizable method to yield high-titer specific antibodies.

Original languageEnglish
Pages (from-to)11247-11253
Number of pages7
JournalCancer Research
Volume66
Issue number23
DOIs
StatePublished - 1 Dec 2006

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