Effects of chlorpyrifos on growth of estrogen-dependent human breast cancer cell line

C VENTURA; M NUÑEZ; V GAIDO; D MARTIEL LAMAS; A RANDI; A VENTURINO; E RIVERA; C COCCA

Paris

Congreso; 47th Congress of the European Societies of Toxicology (EUROTOX); 2011

EUROTOX

It has been reported that environmental chemicals are involved in breast cancer risk. Chlorpyrifos (CPF) is an organophosphorus insecticide, commonly applied for pest control in fruit producing regions of our country. It was also described as endocrine disruptor affecting estrogen responses. Our objective was to evaluate the effect of CPF on estrogen dependent MCF-7 breast cancer cells. CPF was tested in vitro at 0.05; 0.5; 5 and 50 Micromolar. Citotoxicity was studied by MTT assay and proliferation by clonogenic assay and bromodeoxyuridine (BrdU) incorporation. Cell cycle progression was studied by flow cytometry. Western blots were performed for estrogen receptor alpha (ER) phosphorylation and Proliferating Cell Nuclear Antigen (PCNA) and p27 expression. Reactive oxygen species (ROS) were determined using DCF fluorescent staining and flow cytometry. Results obtained show that CPF at 50 MicroMolar induced a non-significant decrease in cell viability and a diminished clonogenic proliferation (41%; p lower than 0.01). This effect was associated with an increase in ROS content (32%; p lower than 0.001) and a cell increment in phase sub-G0 (23%; p lower than 0.001). Conversely, CPF at 0.05 Micromolar induced an increase in BrdU incorporation (38%; p lower than 0.05) and it was related to a decrease in p27 expression. PCNA (30%; p lower than 0.05) and ER phosphorylation (36%; p lower than 0.01) levels were increased. We conclude that high doses of xenobiotics inhibit cell proliferation and our results were not unexpected at those concentrations. However, low levels of CPF significantly induced proliferation in MCF-7 cells and it seems to be related to estrogen dependence of the cells.