The present invention provides recombinant antigen-binding regions and antibodies and functional fragments containing such antigen-binding regions that are specific for the membrane-anchored, 29 kDa polypeptide named C4.4a , which is over expressed in tumors. C4.4a has a high abundance in metastases of several cancer types. The antibodies, accordingly, can be used to treat these and other disorders and conditions. Antibodies of the invention also can be used in the diagnostics field, as well as for further investigating the role of C4.4a in the progression of disorders associated with cancer. The invention also provides nucleic acid sequences encoding the foregoing antibodies, vectors containing the same, pharmaceutical compositions and kits with instructions for use.
