Watch out! Pesticide exposure contributes to tumor angiogenesis in our breasts

ZARATE L; PONTILLO C; ESPAÑOL A; MIRET N; CHIAPPINI F; COCCA C; ALVAREZ L; KLEIMAN D; SALES ME; RANDI A

Congreso; 54th Congress of the European Societies of Toxicology EUROTOX 2018; 2018

Hexachlorobenzene (HCB) is a fungicide detected in maternal milk, and Chlorpyrifos (CPF) is a pesticide currently used in agriculture. Breast cancer is by far the most frequently diagnosed cancer in women. HCB and CPF act as endocrine disruptor in rat mammary gland. Vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2) promote tumor growth and angiogenesis. Nitric oxide (NO) and abnormal expression of nitric oxide synthases (NOS1, NOS2, NOS3) are implicated in tumor progression. Our aim was to examine the action of HCB and CPF on angiogenesis in mammary carcinogenesis in vivo and in vitro. In a breast cancer xenograft model with MCF-7 cells, HCB (3 mg/kg bw) and CPF (0.1 mg/kg bw) stimulate angiogenic switch (number of vessels/mm2) and increase VEGF expression (p < 0.05) by Western Blot (WB) in mice skin. In MCF-7, HCB (0.005 μM) increases COX-2 and VEGF levels at 3 h, while at 0.005-5 μM at 24 h (p < 0.01). CPF (0.05 μM) enhances COX-2 and VEGF expression at 6 h, while at 50 μM at 24 h (p < 0.05). In addition, HCB (0.005 μM) at 3 h increases NOS2/NOS3 and at 24 h enhances NOS1, while at 5 μM decreases NOS expression (WB, p < 0.05). CPF (0.05 μM) increases NOS levels at 6 h, while at 50 μM enhances at 24 h (p < 0.05). The pesticides increase the production of NO at lower doses, however reduces it at higher doses (HCB, CPF, p < 0.05). Besides, the pretreatment of MCF-7 with an inhibitor of NOS prevents the increased expression of VEGF and COX-2 by HCB or CPF, suggesting that pesticides enhance angiogenic factors through NO-dependent pathway. Our results demonstrate that both pesticides increase angiogenesis and VEGF expression in vivo and in vitro. In MCF-7, at low doses, the pesticides enhance VEGF, COX-2 and NOS expression, and NO production. At high doses, increase VEGF and COX-2 levels, but differential effects on NOS expression were observed. In conclusion, our findings suggest that HCB and CPF may be a risk factor for human breast cancer progression.