The chemopreventive agent alpha-difluoromethylornithine blocks Ki-ras-dependent tumor formation and specific gene expression in Caco-2 cells.

Abstract

Mutation of the Kirsten-ras (Ki-ras) proto-oncogene occurs frequently in colorectal cancers. alpha-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.

• Authors: Natalia A Ignatenko, Hui Zhang, George S Watts, Bethany A Skovan, David E Stringer, Eugene W Gerner
• Journal: Molecular carcinogenesis (Mol Carcinog) Vol. 39 Issue 4 Pg. 221-33 (Apr 2004) ISSN: 0899-1987 [Print] United States
• PMID: 15057874 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
• Copyright: Copyright 2004 Wiley-Liss, Inc.

Chemical References

• Antineoplastic Agents
• Laminin
• MAS1 protein, human
• Neoplasm Proteins
• Ornithine Decarboxylase Inhibitors
• Proto-Oncogene Mas
• Ornithine Decarboxylase
• Eflornithine

Topics

• Animals
• Antineoplastic Agents (therapeutic use)
• Caco-2 Cells
• Cell Communication
• Cell Movement
• Colonic Neoplasms (genetics, metabolism, prevention & control)
• Eflornithine (therapeutic use)
• Gene Expression Profiling
• Gene Expression Regulation (drug effects)
• Genes, ras (drug effects)
• Humans
• Laminin (metabolism)
• Mice
• Mice, SCID
• Neoplasm Proteins (genetics, metabolism)
• Oligonucleotide Array Sequence Analysis
• Ornithine Decarboxylase (metabolism)
• Ornithine Decarboxylase Inhibitors
• Proto-Oncogene Mas
• Transfection