Abstract: The human cancer antigen 125 (CA125) is over-expressed in epithelial
ovarian cancer cells and it plays a role in the pathogenesis of ovarian cancer.
This protein presents a repeat region containing up to sixty tandem repeat
units. The anti-CA125 monoclonal antibodies have been previously classified
into three groups: two major families, the OC125-like antibodies and M11-like
antibodies, and a third group, the OV197-like antibodies. A model in which a
single repeat unit contains all the epitopes for these antibodies has been also
proposed, even if their exact position is still undetermined. In the present
work, the affinities of the monoclonal antibodies, representative of the three
families, have been investigated for different CA125-recombinant repeats
through Western blot analysis. Different patterns of antibody recognition for
the recombinant repeats show that CA125 epitopes are not uniformly distributed
in the tandem repeat region of the protein. The minimal region for the
recognition of these antibodies has been also individuated in the SEA domain
through the subcloning of deleted sequences of the highly recognized repeat-25
(R-25), their expression as recombinant fragments in E. coli and Western blot
analysis. Obtained data have been further confirmed by ELISA using the entire
R-25 as coating antigen.
