THE CAT-TOX (L) ASSAY - A SENSITIVE AND SPECIFIC MEASURE OF STRESS-INDUCED TRANSCRIPTION IN TRANSFORMED HUMAN LIVER-CELLS

Identifying and measuring the molecular mechanisms of toxicity is an i mportant goal in hazard assessment. We have developed an assay in tran sformed human liver cells to simultaneously measure the transcriptiona l responses of 14 stress promoter- or response element-chloramphenicol acetyl transferase (CAT) fusion constructs that are stably integrated into the HepG2 cell line. This assay can measure a wide spectrum of s tresses, both toxic and nontoxic, such as protein and protein biosynth esis perturbations, DNA damage, heavy metals, and planar aromatic hydr ocarbons. We found that each promoter or response element can be induc ed by one or more of four chemicals that were tested in the assay. The se results have been interpreted in light of the current models of act ion for each compound. The responses of this assay system can distingu ish among compounds that are closely related in their structure and ha ve been shown previously to elicit similar biological activities in si mple assay systems. We have designated this technique the CAT-Tox (L)i ver assay. It measures a broad range of cellular stresses and toxicant s at levels that were comparable to or below those of established meth ods. The induction profiles generated using the CAT-Tox (L) assay can help to elucidate the molecular mechanisms by which chemicals exert th eir actions on human cells. These profiles can be indicative of both t oxic and nontoxic processes that are occurring in the cell. We propose that this cellular stress assay can serve as a screen for a variety o f substances at the molecular level. (C) 1995 Society of Toxicology