MUC1 isoform specific monoclonal antibody 6E6/2 detects preferential expression of the novel MUC1/Y protein in breast and ovarian cancer.
The products of the MUC1 gene are known to be highly expressed in human breast cancer cells. The best characterized MUC1 protein is a polymorphic, type 1 transmembrane molecule containing a large extracellular domain composed primarily of a variable number of 20 amino acid tandem repeats. We have recently identified a novel protein product of the MUC1 gene, the MUC1/Y protein, that is also a transmembrane protein but is devoid of the tandem repeat array and its immediate flanking sequences. To analyze its expression in tumor cells we generated monoclonal antibodies directed against the MUC1/Y extracellular domain (anti-MUC1/Yex MAbs). Epitope mapping identified the MAb, 6E6, which recognized the MUC1/Y isoform with exquisite specificity- the repeat-array-containing MUC1 isoform could not compete out this immunoreactivity. A 30mer peptide which is unique for MUC1/Y and corresponds to the "join" region generated by the MUC1/Y specific splice, abrogated all 6E6 MAb immunoreactivity towards MUC1/Y. Immunoprecipitation of the MUC1/Y protein with 6E6 MAbs revealed that, in contrast with the proteolytic cleavage of the tandem-repeat-array-containing MUC1 isoform, MUC1/Y is not cleaved. Flow cytometry analyses using the 6E6 MAbs demonstrated that the MUC1/Y isoform is expressed on the cell surface of both MCF-7 breast cancer cells and malignant epithelial cells present in effusions obtained from breast and ovarian cancer patients. Our results unequivocally establish that the MUC1/Y protein is expressed on the surface of breast cancer cells and cells of other epithelial malignancies. The anti-MUC1/Y MAbs described here can target MUC1/Y expressing tumor cells in vivo and are likely to be important reagents both for epithelial tumor diagnosis and immunotherapy.
Hartman
M
M
Department of Cell Research and Immunology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel.
Baruch
A
A
Ron
I
I
Aderet
Y
Y
Yoeli
M
M
Sagi-Assif
O
O
Greenstein
S
S
Stadler
Y
Y
Weiss
M
M
Harness
E
E
Yaakubovits
M
M
Keydar
I
I
Smorodinsky
N I
NI
Wreschner
D H
DH
D016475:3T3 Cells; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001201:Ascites / Q000276:immunology / Q000473:pathology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism; D000939:Epitopes / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D018396:Mucin-1 / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism*; D016066:Pleural Effusion, Malignant / Q000276:immunology / Q000473:pathology; D020033:Protein Isoforms / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017433:Protein Structure, Secondary; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000276:immunology; D014162:Transfection; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D018076:DNA, Complementary; D000939:Epitopes; D018396:Mucin-1; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011993:Recombinant Fusion Proteins