The Chemopreventive Agent α-Difluoromethylornithine Blocks Ki-ras-Dependent Tumor Formation and Specific Gene Expression in Caco-2 Cells

Natalia A. Ignatenko, Hui Zhang, George S. Watts, Bethany A. Skovan, David E. Stringer, Eugene W. Gerner

Research output: Contribution to journalArticle

39 Scopus citations


Mutation of the Kirsten-ras (Ki-ras) proto-oncogene occurs frequently in colorectal cancers. α-Difluoromethylornithine (DFMO), an irreversible inhibitor of the polyamine biosynthetic enzyme, ornithine decarboxylase (ODC), inhibits Ki-ras transformation and colon tumorigenesis in carcinogen-treated animal models by mechanisms yet to be elucidated. Caco-2 cells transfected with an activated Ki-ras, but not parental cells, formed tumors in severe combined immunodeficient (SCID) mice. DFMO treatment (2% in drinking water) prevented tumor growth. Gene expression profiling was performed to identify Ki-ras- and DFMO-dependent patterns of gene expression. Microarray results were validated with real-time or semi-quantitative RT-PCR and/or Western blot analysis. Genes upregulated in Caco-2 cells expressing an activated Ki-ras encoded cytoskeletal-, transport-, protease-, and gap junction -associated proteins. These genes are important for normal development and maintenance of colonic epithelial tissue. Caco-2 cells transfected with an activated Ki-ras displayed increased expression of the integrin alpha 1 (INGA1) and enhanced cell migration on laminin. These parameters were unaffected by DFMO, but Ki-ras-dependent migration was inhibited by INGA1 antibodies. Other Ki-ras-dependent, but DFMO-independent, genes included transglutaminase (TGase) and kallikrein 6 (KLK6). Ki-ras-transfected cells also expressed increased levels of connexin43 (Cx43) (RNA and protein), tight junction protein, and endothelin 1. DFMO reversed these increases. The results indicated that the Ki-ras oncogene caused changes in experimental cell migration and cell-cell communication genes and that some of these changes could be reversed by DFMO.

Original languageEnglish (US)
Pages (from-to)221-233
Number of pages13
JournalMolecular Carcinogenesis
Issue number4
StatePublished - Apr 1 2004



  • Caco-2 cells
  • Cx43
  • DFMO
  • Ki-ras

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research

Cite this