ATLA::Alternatives to Laboratory Animals

Volume 23, Number 4

The reducing agent dithiothreitol (DDT) increases expression of c-myc and c-fos proto-oncogenes in human cells.

ATLA 23, 497-503, July/August 1995

Jan Skouv1,2, Ilona Kryspin-Sørensen3, Henrik Frandsen3, Eva Selzer Rasmussen3 and Jes Forchhammer1

1Department of Molecular Oncology, Division of Cancer Biology, The Danish Cancer Society, Strandboulevarden 49, 7.1, DK-2100 Copenhagen, Denmark; 2Present address: Department of Molecular Cell Biology, State Serum Institute, Artillerivej 5, DK-2300 Copenhagen, Denmark; 3Institute of Toxicology, National Food Agency of Denmark, Mørkhøj Bygade 19, DK-2860 Søborg, Denmark

SUMMARY

The objective of the present study was to assess the possible tumour promoting activity of the food mutagen 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP), by studying its influence on the expression of three genes considered to be of relevance in the tumour promotion step. The genes were two proto-oncogenes, c-fos and c-myc, and the tumour suppressor gene, p53. We observed that the expression of the c-fos and c-myc genes was reduced when human bladder epithelial cells were treated with a standard solution of N-OH-PhlP and dithiothreitol (DTT), previously shown to be genotoxic. However, when cells were treated with DTT alone, the expression of c-fos and c-myc was also transiently induced. We therefore conclude that DTT, and not N-OH-PhIP, induced oncogene expression. Induction of both c-fos and c-myc expression by a reducing agent, DTT, which is frequently used in in vitro toxicology studies, is a novel observation that suggests the need for a cautious interpretation of such studies.

Keywords: oncogene expression, tumour promotion, in vitro testing, phorbol ester, redox regulation