Malignant transformation of human colon epithelial cells by benzo[c]phenanthrene dihydrodiolepoxides as well as 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine.

Abstract

Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HCAs) ingested with food have repeatedly been suggested to be involved in the malignant transformation of colon epithelial cells. In order to test this hypothesis, HCEC cells (SV40 large T antigen-immortalized human colon epithelial cells) were incubated with a racemic mixture of benzo[c]phenanthrene dihydrodiol epoxides (B[c]PhDE), extremely potent carcinogenic PAH metabolites in vivo, or with 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP), the N-hydroxylated metabolite of the most abundant HCA in cooked meat. First, it was shown that HCEC cells express sulfotransferase 1A1, which is needed to metabolize N-OH-PhIP to the corresponding N-sulfonyloxy derivative, the direct precursor molecule of genotoxic nitrenium ions. Thereafter, exponentially growing HCEC cells were exposed five times to 0.1 microg (0.37 nmol) B[c]PhDE/ml for 30 min or 0.72 microg (3 nmol) N-OH-PhIP/ml for 24 h. Chemically treated HCEC cells showed an enhanced saturation density and grew faster than the corresponding solvent-treated cell cultures. After five treatment cycles, HCEC(B[c]PhDE) as well as HCEC(N-OH-PhIP) cells lost cell-cell contact inhibition and started piling up and forming foci in the culture flasks. Furthermore, HCEC(B[c]PhDE) and HCEC(N-OH-PhIP) cells were injected i.m. into SCID mice. Within 6 weeks after injection, eight animals out of eight injected with HCEC(B[c]PhDE) or HCEC(N-OH-PhIP) cells developed tumors at the site of injection, thus demonstrating the high tumorigenic potential of the HCEC(B[c]PhDE) and HCEC(N-OH-PhIP) cell cultures. Taken together, we show for the first time that the abovementioned active PAH metabolites as well as N-OH-PhIP are indeed able to malignantly transform human colon epithelial cells in vitro.

• Authors: Uta Herbst, Judith Iris Fuchs, Wera Teubner, Pablo Steinberg
• Journal: Toxicology and applied pharmacology (Toxicol Appl Pharmacol) Vol. 212 Issue 2 Pg. 136-45 (Apr 15 2006) ISSN: 0041-008X [Print] United States
• PMID: 16137733 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Carcinogens
• Epoxy Compounds
• Imidazoles
• Phenanthrenes
• Pyridines
• 2-hydroxyamino-1-methyl-6-phenylimidazo(4,5-b)pyridine
• Dimethyl Sulfoxide

Topics

• Animals
• Blotting, Western
• Carcinogens (toxicity)
• Cell Proliferation (drug effects)
• Cell Transformation, Neoplastic (drug effects)
• Colon (cytology, drug effects, ultrastructure)
• Dimethyl Sulfoxide (pharmacology)
• Epithelial Cells (drug effects, physiology, ultrastructure)
• Epoxy Compounds (toxicity)
• Humans
• Imidazoles (toxicity)
• Immunohistochemistry
• Mice
• Mice, SCID
• Phenanthrenes (toxicity)
• Pyridines (toxicity)