SELECTIVE EXPRESSION OF CARCINOEMBRYONIC ANTIGEN PROMOTER IN CANCER CELL-LINES - TARGETING STRATEGY FOR GENE-THERAPY IN COLORECTAL-CANCER

PURPOSE: This study was designed to characterize the mechanisms regula ting the expression of the human carcinoembryonic antigen promoter (pC EA), in terms of tissue-specific targeting for gene therapy. The promo ter was subcloned to a luciferase reporter gene (pCEA/Luc) in our labo ratory and compared with a virally controlled luciferase vector (pSV40 /Luc). METHODS: Four human cancer cell lines (HeLa, SW480, Caco2, and SW1116) were transfected with either pCEA/Luc or pSV40/Luc. Cells were treated with interferon-gamma and assayed at 72 hours after treatment . Carcinoembryonic antigen level was measured by enzyme immunoassay. L uciferase expression was measured at 48 hours and one week after trans fection by luminometry. RESULTS: Luciferase activity after transfectio n with pCEA/Luc was higher in CEA-positive cells than in CEA-negative cells (P < 0.0001). pCEA/Luc demonstrated higher activity than pSV40/L uc in CEA-positive cells (P < 0.0001), but not in CEA-negative cells. In Caco2 cells, which before confluence are CEA-negative, luciferase e xpression increased on reaching confluence (P < 0.0001). Well to moder ately differentiated cells responded to the interferon-gamma treatment , but the increase in CEA secretion did not correspond to an increase in pCEA/Luc expression. CONCLUSIONS: The expression of pCEA correlates well with the CEA production by the specific cell line offering a pot ential tissue-specific targeting strategy for colon cancer gene therap y. Furthermore, the tissue-specific CEA. promoter has a higher and mor e persistent activity in CEA-positive human cancer cells than a viral promoter. The lack of response to interferon-gamma treatment suggests a different mechanism of action for interferon-gamma other than direct ly interacting with the promoter.