Induced gene transcription: implications for biomarkers.

Numerous xenobiotics regulate cellular functions by altering transcription of target genes. Use of sensitive and specific biomarkers based on gene transcript levels may help clarify the shape of the dose-response curve in the low-dose region associated with human exposures to environmental concentrations of chemicals. We have quantified gene transcription induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in both animal models and humans with the use of Northern analysis and PCR-based methods. In addition, we describe a rapid and sensitive in vitro assay that we have used to screen chemicals and biological samples for their ability to alter gene transcription. Whereas some of the endpoints in our studies such as cytochrome P-450 1A1 are predictive indicators of exposure and dose, other gene responses such as growth factors are more complex and represent a critical event, progression, or adaptation to a pathological alteration. In conclusion, measurement of toxicant-induced gene transcription will contribute to the usefulness of biomarkers in addressing issues of human health and environmentally induced disease.