In vitro sensitivity of granulo-monocytic progenitors as a new toxicological cell system and endpoint in the ACuteTox Project.

The ACuteTox Project (part of the EU 6th Framework Programme) was started up in January 2005. The aim of this project is to develop a simple and robust in vitro strategy for prediction of human acute systemic toxicity, which could replace animal tests used for regulatory purposes. Our group is responsible for the characterization of the effect of the reference chemicals on the hematopoietic tissue. CFU-GM assay based on the culture of human mononuclear cord blood cells has been used to characterize the effects of the selected compounds on the myeloid progenitors. Previous results have shown the relevance of the CFU-GM assay for the prediction of human acute neutropenia after treatment of antitumoral compounds, and this assay has been recently approved by the ECVAM's Scientific Advisory Committee. Among the compounds included in the study there were pharmaceuticals, environmental pollutants and industrial chemicals. Eleven out of 55 chemicals did not show any cytotoxic effect at the maximum concentration tested. The correlation coefficients of CFU-GM IC50, IC70 and IC90 values with human LC50 values (50% lethal concentration calculated from time-related sublethal and lethal human blood concentrations) were 0.4965, 0.5106 and 0.5142 respectively. Although this correlation is not improve respect to classical in vitro basal cytotoxicity tests such as 3T3 Neutral Red Uptake, chemicals which deviate substantially in the correlation with these assays (colchicine, digoxin, 5-Fluorouracil and thallium sulfate) fitted very well in the linear regression analysis of the CFU-GM progenitors. The results shown in the present study indicate that the sensitivity of CFU-GM progenitors correlates better than the sensitivity of HL-60 cells with human LC50 values and could help to refine the predictability for human acute systemic toxicity when a given chemical may affect to the hematopoietic myeloid system.