In vitro effects of phthalate mixtures on colorectal adenocarcinoma cell lines

Among endocrine-disrupting chemicals, phthalates are an important concern because of their wide­spread exposure in humans and environmental contamination. Even though the use of some phthalates has been restricted for toys, some plastics, and food contact materials, exposure to the mixture of these contaminants at very low concentrations in various matrices are still being reported. In the current research, the effects of the mixture of some phthalates were studied. Di-n-butyl phthalate (DBP), n-butyl benzyl phthalate (BBP), di-2-ethylhexyl phthalate (DEHP), diisononyl phthalate (DiNP), di-n-octyl phthalate (DNOP), and diisodecyl phthalate (DiDP) were tested on two colorectal adenocarcinoma cell lines; DLD-1 and HT29 were studied as described before. Cells were treated with increasing log concentrations (0.33 ppt to 33.33 ppb) of the phthalate mixture; cell viability/proliferation was measured by MTT and staining with neutral red and crystal violet; lactate dehydrogenase (LDH) activity was mea­sured following 24-h exposure. Cell viability/proliferation increased from phthalate treatment at concentrations less than 33.33 ppt. The phthalate mixture induced increases in HT29 proliferation of 10.94% at 33.33 ppt and 60.87% at 3.33 ppt, whereas this proliferation relation at lower concentrations was not found for DLD1 cells. The present study demonstrates preliminary information regarding the low dose induction of proliferation of the cancer cells by phthalate mixtures. Because non-monotonic dose responses are still being debated, further studies are required to re-evaluate the reference doses defined by governments for phthalates.