The abundantly expressed carcinoembryonic antigen (CEA) on several cancer types is an attractive target for anti body-directed therapy. However, CEA is also present in some normal tissues. Here, we produced a dual functioning protein, designated as CAtin that exhibits both specific binding and killing functions, by fusing a tumor-specific apoptosis-inducing molecular Apoptin to C-terminus of an anti-CEA single-chain disulfide-stabilized Fv antibody (scdsFv). The CAtin proteins were expressed in Escherichia coli (E coli), refolded and purified on an immobilized Ni2+ affinity chromatography column. SIDS-PAGE and Western blotting revealed that the recombinant protein was well-expressed and the yield was approximately 250 mg/L. We demonstrated by flow cytometry and immunofluorescence assays that CAtin could bind specifically to human colon carcinoma cells (LoVo), but almost not to human uterine cervix (Hela). The results suggest that CAtin is active and specific toward CEA-positive cells and may potentially be used in CEA-targeted cancer therapy. (C) 2009 Elsevier Inc. All rights reserved