N-Butyl Benzyl Phthalate Promotes Breast Cancer Progression by Inducing Expression of Lymphoid Enhancer Factor 1

Tsung-Hua Hsieh,Chia-Yi Hsu,Chih-Hsing Hung,Chee-Yin Chai,Edward Hsi,Jau-Nan Lee,Jau-Ling Suen,Eing-Mei Tsai,Cheng-Fang Tsai,Shao-Chun Wang,Po-Lin Kuo,Jun Li

doi:10.1371/journal.pone.0042750

Abstract

Environmental hormones play important roles in regulating the expression of genes involved in cell proliferation, drug resistance, and breast cancer risk; however, their precise role in human breast cancer cells during cancer progression remains unclear. To elucidate the effect of the most widely used industrial phthalate, n-butyl benzyl phthalate (BBP), on cancer progression, we evaluated the results of BBP treatment using a whole human genome cDNA microarray and MetaCore software and selected candidate genes whose expression was changed by more than ten-fold by BBP compared with controls to analyze the signaling pathways in human breast cancer initiating cells (R2d). A total of 473 genes were upregulated, and 468 were downregulated. Most of these genes are involved in proliferation, epithelial-mesenchymal transition, and angiogenesis signaling. BBP induced the viability, invasion and migration, and tube formation in vitro, and Matrigel plug angiogenesis in vivo of R2d and MCF-7. Furthermore, the viability and invasion and migration of these cell lines following BBP treatment was reduced by transfection with a small interfering RNA targeting the mRNA for lymphoid enhancer-binding factor 1; notably, the altered expression of this gene consistently differentiated tumors expressing genes involved in proliferation, epithelial-mesenchymal transition, and angiogenesis. These findings contribute to our understanding of the molecular impact of the environmental hormone BBP and suggest possible strategies for preventing and treating human breast cancer.

Highlights

Phthalates, a group of environmental hormones, disrupt endocrine function and affect human health by mimicking the function or inhibiting the action of steroid receptors
The viability and invasion and migration of these cell lines following butyl benzyl phthalate (BBP) treatment was reduced by transfection with a small interfering RNA targeting the mRNA for lymphoid enhancer-binding factor 1; notably, the altered expression of this gene consistently differentiated tumors expressing genes involved in proliferation, epithelial-mesenchymal transition, and angiogenesis
R2d cells were stimulated with different concentrations of BBP (10 nM, 100 nM, 1 mM, and 10 mM) for 24 h, and the wavelength was measured with an ELISA reader

Summary

Introduction

Phthalates, a group of environmental hormones, disrupt endocrine function and affect human health by mimicking the function or inhibiting the action of steroid receptors. They are present in cosmetics, medical products, and toys and can be absorbed through the skin [1] or ingested if food comes into contact with plastic film wrappers [2]. Several studies have revealed that 10 mM BBP increases the proliferation ability and induces mitosis in the ER-positive breast cancer cell lines MCF-7 and ZR-75 [7,8]. The investigation examined whether there is a relationship between BBP and tamoxifen chemotherapy, finding that BBP promotes resistance to tamoxifen by inhibiting tamoxifen-induced apoptosis in breast cancer cells [10]. Whether BBP exposure affects the breast cancer initiating cell system is largely unknown

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Conclusion