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

ZARATE, L; PONTILLO, CAROLINA; ALEJANDRO ESPAÑOL; MIRET NOELIA; CHIAPPINI FLORENCIA; COCCA CLAUDIA; ALVAREZ L; KLEIMAN, D; MARÍA E. SALES; RANDI, ANDREA

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

Hexachlorobenzene(HCB) is a widespread organochlorine fungicide detected in maternal milk andlipid foods. Chlorpyrifos (CPF) is an organophosphate pesticide currently usedin agriculture. Breast cancer is by far the most frequently diagnosed cancer inwomen. We demonstrated that HCB and CPF induce cell proliferation and they actas endocrine disruptor in rat mammary gland. Vascular endothelial growth factor(VEGF) and cyclooxygenase-2 (COX-2) promote tumor growth, angiogenesis andmetastasis. Nitric oxide (NO) and abnormal expression of nitric oxide synthases(NOS1, NOS2, NOS3) are implicated in tumor progression. Our aim was to examinethe action of HCB and CPF exposure on angiogenesis in mammary carcinogenesis in vivo and in vitro. In a mouse breast cancer xenograft model with MCF-7 cells(+Estrogen Receptor alpha), HCB (3 mg/kg body weight, bw) and CPF (0.1 mg/kgbw) stimulate angiogenic switch (number of vessels/mm2) and increaseVEGF 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 (p<0.05), while at 0.005and 5 µM at 24 h (p<0.001). CPF (0.05 µM) enhances COX-2 and VEGF levels at6 h (p<0.05), while at 50 µM at 24 h (p<0.001). Our studies in NOSevaluation show that HCB (0.005 µM) at 3 h increases NOS2/NOS3 and at 24 h enhancesNOS1 expression (p<0.001) by WB, while at 5 µM decreases NOS expression(p<0.05). CPF (0.05 µM) increases NOS levels at 6 h (p<0.05), while at 50µM enhances at 24 h (p<0.05). MCF-7 exposure to each pesticide increases theproduction of NO at lower doses, however reduces it at higher doses (HCB, CPFp<0.05). Besides, we found that pretreatment of MCF-7 with an inhibitor ofNOS (L-NMMA) prevents the increase in VEGF and COX-2 expression by HCB (0.005µM) or CPF (0.05 µM), suggesting that pesticides enhance angiogenic factorsthrough NO-dependent pathway. Our results demonstrate that both pesticidesincrease angiogenesis and VEGF expression invivo and in vitro. In MCF-7, atlow doses (proliferation), the pesticides enhance VEGF, COX-2 and NOSexpression, and NO production. At high doses (apoptosis and cell cycle arrest),increase VEGF and COX-2 levels, but differential effects on NOS expression wereobserved, and decrease NO content. In conclusion, our findings suggest that HCBand CPF may be a risk factor for human breast cancer progression.