1. General Discussion
A cell culture of human liver cancer cells can be used to detect the presence of toxic or carcinogenic organic compounds in environmental samples. A sample of water, soil, aquatic sediment, or tissue is extracted with a solvent to remove semivolatile organic compounds, and a small amount of the extract is placed in the medium of a culture well that contains cells attached to the bottom of the well. After exposure, the cells are rinsed and lysed, the cell fragments are removed via centrifugation, and the extract is tested for luminescence. The cells produce a luminescent enzyme called luciferase if the extract contained dioxin-like compounds because a reporter gene from the firefly has been inserted into the human chromosome at the CYPIAI gene, which is induced by dioxin and other planar compounds. The amount of light produced, which is quantified by a luminometer, is a function of the concentrations and induction potency of the organic compounds in the extract. Of the relevant toxins, dioxin [2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD)] has the strongest affinity for the Ah-receptor (AhR), and therefore is detected at the lowest concentrations.