title: Antibody targeting of cell-bound MUC1 SEA domain kills tumor cells.
abstract: The cell-surface glycoprotein MUC1 is a particularly appealing target for antibody targeting, being selectively overexpressed in many types of cancers and a high proportion of cancer stem-like cells. However the occurrence of MUC1 cleavage, which leads to the release of the extracellular α subunit into the circulation where it can sequester many anti-MUC1 antibodies, renders the target problematic to some degree. To address this issue, we generated a set of unique MUC1 monoclonal antibodies that target a region termed the SEA domain that remains tethered to the cell surface after MUC1 cleavage. In breast cancer cell populations, these antibodies bound the cancer cells with high picomolar affinity. Starting with a partially humanized antibody, DMB5F3, we created a recombinant chimeric antibody that bound a panel of MUC1+ cancer cells with higher affinities relative to cetuximab (anti-EGFR1) or tratuzumab (anti-erbB2) control antibodies. DMB5F3 internalization from the cell surface occurred in an efficient temperature-dependent manner. Linkage to toxin rendered these DMB5F3 antibodies to be cytotoxic against MUC1+ cancer cells at low picomolar concentrations. Our findings show that high-affinity antibodies to cell-bound MUC1 SEA domain exert specific cytotoxicity against cancer cells, and they point to the SEA domain as a potential immunogen to generate MUC1 vaccines.
authors.affiliation: Department of Cell Research and Immunology, Tel Aviv University, Ramat Aviv, Israel.
authors.forename: Edward
authors.initials: E
authors.lastname: Pichinuk
authors.forename: Itai
authors.initials: I
authors.lastname: Benhar
authors.forename: Oded
authors.initials: O
authors.lastname: Jacobi
authors.forename: Michael
authors.initials: M
authors.lastname: Chalik
authors.forename: Lotem
authors.initials: L
authors.lastname: Weiss
authors.forename: Ravit
authors.initials: R
authors.lastname: Ziv
authors.forename: Carolyn
authors.initials: C
authors.lastname: Sympson
authors.forename: Amolkumar
authors.initials: A
authors.lastname: Karwa
authors.forename: Nechama I
authors.initials: NI
authors.lastname: Smorodinsky
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Rubinstein
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Wreschner
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D018396:Mucin-1 / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018396:Mucin-1