Development Of An Immortalized Human Cell Line To Study The Effects Of Environmental Exposure To Carcinogens
Description
In order to provide an improved in vitro model with which to investigate human diseases, such as cancer that may be promoted by toxicant exposure, we have characterized a newly developed cell line derived from the renal proximal tubule epithelial cells (RPTEC) of a healthy human male donor. The RPTEC/TERT1 cell line has been immortalized using the human telomerase reverse transcriptase (hTERT) catalytic subunit and does not exhibit chromosomal abnormalities (Evercyte Laboratories). We have conducted single-compound and binary mixture experiments with the common environmental carcinogens, cadmium (Cd) and benzo[a]pyrene (B[a]P). Cells exhibited cytotoxicity to concentrations of B[a]P and Cd as low as 1 nM and 3 μM, respectively. We examined a panel of eight genes relevant to the toxic responses of these two agents. RPTEC/TERT1 cells exhibit compound-specific gene expression responses to concentrations as low as 1 nM B[a]P and 1 μM Cd. A significant increase in the expression of genes coding for B[a]P metabolizing enzymes (CYP1A1, CYP1B1) occurred in a dose- and time-dependent manner. Activity of these enzymes was verified using the EROD activity assay. Gene expression changes after co-exposure were consistent with changes in gene expression seen after single-compound exposures. We detected BPDE-DNA adducts after exposure to B[a]P which confirms that the RPTEC/TERT1 cell line responds to B[a]P consistently with what is known regarding these cells in a normal, healthy kidney. Under co-exposure, adducts detected were significantly decreased in some groups. A significant increase in the expression of NRF2 antioxidant pathway genes after co-exposure was observed. Additionally, total glutathione levels were significantly increased in cells exposed to Cd alone and co-exposure groups. These results suggest that Cd may antagonize the formation of BPDE-DNA adducts in RPTEC/TERT1 cells under these conditions. Future studies will test mutagenesis under conditions of co-exposure to Cd and B[a]P. Our studies are the first to provide information regarding toxicological responses in this novel cell line that model those of the target tissue. We conclude that these cells can provide a useful tool for future toxicological studies. These studies will help scientists better understand the initiating events that may promote carcinogenesis in normal, healthy human cells.