DNA arrays within REACH.

Reliable, fast, low cost toxic risk assessment of chemicals, not resorting to animal experimentation.

Our body is made of a large number (millions of billion) cells.  When exposed to a chemical, a cell will respond in mobilizing  a number of dedicated genes located in its nucleus. A DNA array  is a rather novel tool, enabling to simultaneously monitor the  mobilization of a large number of genes. To simplify, the array  somehow allows the observer to take place in the control room  of the cell its nucleus-, and watch there the level of expression  of the genes, which appear colour-coded by some biochemical trick  (red for genes boosted by the chemical, green for genes repressed).  We built DNA arrays bearing a large number of human genes mobilized  by the cell in response to a variety of toxic insults - acute  toxicity, neuro-, geno (cancer)-, immuno-toxicities, reproductive  and developmental toxicities, endocrine disruptors, etc. Human  cells in culture are exposed for selected times to various concentrations  of the chemical to be tested. Each experiment is duplicated for  improved accuracy. Following extraction and processing of the  product of gene expression (transcripts), and exposure to the  array, the level of expression of the genes is automatically  recorded.

Since the experiment deals with human cells and human genes,  the toxicity assessment using DNA arrays is valid for humans.  It is fast, as a typical experiment takes 1-3 days. The  throughput can be adjusted according to the demand, as dedicated,  fully robotized set-ups can test tens to thousands of chemicals  simultaneously on various human cell types. Once the set-up  has been installed, the experiment is highly cost-effective  (of the order of 1/1000th that of conventional toxicity testing).  No animal experimentation is needed.

Every year, close to one million citizens in EU countries  die of cancer. Since less then 10% of all cancers are linked  to hereditary defects, it follows that over 90% are due to the  environment (including life-style, diet etc). Based on cancer  mortality data collected over the past 80 years, which show a  5-fold increase between 1960 and 1980, when large quantities  of man-made chemicals were introduced in our environment, we  find that 3 out of 4 cancer deaths are linked to carcinogenic  chemicals in our environment (pesticides, food additives etc.).  Reliable assessment of carcinogenicity of chemicals is therefore  of highest priority for consumer safety and disease prevention:  DNA arrays provide the solution, the public opinion must insist  that the REACH project adopts this modern method, and bans the  outdated toxicology testing in animal models.

Prof. Claude Reiss

Molecular toxicologist and President of Antidote-Europe