The effects of tributyltin oxide and deoxynivalenol on the transcriptome of the mouse thymoma cell line EL-4

The main goal of this study was to assess the potential of the mouse thymoma EL-4 cell line in screening for chemical induced immunotoxicity. Therefore, EL-4 cells were exposed to two well-known immunotoxicants, organotin compound tributyltin oxide (TBTO, 0.5 and 1 mu M for 3 or 6 h) and the mycotoxin deoxynivalenol (DON, 0.25, 0.5 and 1 mu M for 3, 6 or 11 h). Previous studies in human Jurkat T cells and mouse thymus in vivo showed that the primary mode of action of TBTO is induction of endoplasmic reticulum (ER) stress, T cell activation and apoptosis. DON induces ribotoxic stress and, similarly to TBTO, induces ER stress, T cell activation and apoptosis. In the present study, the effects of TBTO and DON on EL-4 mRNA expression were assessed by whole genome microarray analysis. The microarray data were then compared to those obtained with mouse thymuses in vivo, mouse thymocytes in vitro, and CTLL-2 cells and human Jurkat cells in vitro exposed to TBTO or DON. Analysis at the level of gene sets revealed that part of the previously detected modes of action of TBTO and DON were not observed in the EL-4 cell line. In EL-4 cells, TBTO induced genes involved in calcium signalling and ER stress but did not induce genes involved in T cell activation and apoptosis. DON induced RNA related processes and ribosome biogenesis. Furthermore, DON downregulated ER stress, T cell activation and apoptosis which is opposite to the mechanism of DON observed in the mouse thymus in vivo and in Jurkat T cells in vitro. Apparently, EL-4 cells lack factors that are necessary to link ribotoxic stress to ER stress. In addition, of the lack of T cell activation response of EL-4 cells to TBTO is likely due to the fact that these cells are in a constitutively activated state already. Based on the results obtained for TBTO and DON, it can be concluded that the EL-4 cell line has limited value for immunotoxicogenomics based screening.