title: Gene therapy of metastatic colon carcinoma: regression of multiple hepatic metastases by adenoviral expression of bacterial cytosine deaminase.
abstract: Colon carcinoma accounts for 20% of deaths due to malignancies in the Western world. Once metastases occur, therapeutic options are limited, with an approximate 5-year survival of only 5%. To investigate the potential of new gene therapeutic approaches, a hepatic micrometastasis model of colon carcinoma in BALB/c mice was established. Inoculation of syngeneic MCA26 colon carcinoma cells into the spleens of 18- to 20-week-old mice resulted in the formation of multiple hepatic metastases. Selective transduction of developing hepatic metastases was demonstrated using a beta-galactosidase-expressing recombinant adenovirus. Cytosine deaminase (CD) can metabolize 5-fluorocytosine into the chemotherapeutic reagent 5-fluorouracil (5FU). The antitumoral potential of this suicide gene therapy approach was explored by systemic application of a recombinant replication-deficient adenovirus encoding for the bacterial CD gene under the control of the cytomegalovirus promoter (Ad.CMV-CD). Injection into the tail vein of tumor-bearing mice resulted in delayed tumor growth with significant reduction in hepatic metastases. The potential of this experimental approach for possible future clinical applications was evaluated by investigating adenoviral transduction efficiency, 5FU sensitivity, and 5-fluorocytosine-dependent Ad.CMV-CD toxicity in a variety of human colon cancer cell lines. Although the murine cell lines MCA26 and CC36 were highly sensitive to 5FU, the human colon cancer cell lines showed a 1-100 times higher resistance to 5FU. Specific Ad.CMV-CD toxicity correlates with 5FU toxicity. Transduction efficiency in human colon carcinoma cell lines was shown to be 10-1700 times higher compared with murine cell lines, thus compensating for 5FU resistance. In conclusion, suicide gene therapy using CD may be promising as an adjuvant treatment regimen for hepatic micrometastases of human colon carcinoma.
authors.affiliation: Department of Medicine, University Hospital Eppendorf, Hamburg, Germany. block@uke.uni-hamburg.de
authors.forename: A
authors.initials: A
authors.lastname: Block
authors.forename: C T
authors.initials: CT
authors.lastname: Freund
authors.forename: S H
authors.initials: SH
authors.lastname: Chen
authors.forename: K P
authors.initials: KP
authors.lastname: Nguyen
authors.forename: M
authors.initials: M
authors.lastname: Finegold
authors.forename: E
authors.initials: E
authors.lastname: Windler
authors.forename: S L
authors.initials: SL
authors.lastname: Woo
mesh_terms: D000256:Adenoviridae / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000633:toxicity; D003110:Colonic Neoplasms / Q000201:enzymology / Q000628:therapy* / Q000821:virology; D043525:Cytosine Deaminase; D004305:Dose-Response Relationship, Drug; D005260:Female; D005472:Fluorouracil / Q000494:pharmacology; D015316:Genetic Therapy; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology / Q000556:secondary* / Q000628:therapy* / Q000821:virology; D051379:Mice; D008807:Mice, Inbred BALB C; D009700:Nucleoside Deaminases / Q000096:biosynthesis / Q000235:genetics* / Q000633:toxicity; D012074:Remission Induction
chemical_list: D001426:Bacterial Proteins; D009700:Nucleoside Deaminases; D043525:Cytosine Deaminase; D005472:Fluorouracil