Breast cancer is associated with methylation and expression of the a disintegrin and metalloproteinase domain 33 (ADAM33) gene affected by endocrine-disrupting chemicals

A disintegrin and metalloproteinase domain 33 (ADAM33) gene is a transmembrane glycoprotein that mediates changes in cell adhesion and plays an important role in cancer progression. Since bisphenol A (BPA) and phthalates are epigenetically toxic, the purpose of this study was to examine whether BPA and phthalate metabolites, including monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-isobutyl phthalate (MIBP), mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), have an epigenetic impact on ADAM33 and the incidence of breast cancer. CpG islands of breast cancer microarray data-sets obtained from the Gene Expression Omnibus (GEO) were used to assess the ADAM33 methylation profile. We designed a case-control study including 44 cases and 22 age-matched controls to detect the methylation status of intron 1 in ADAM33 from peripheral blood mononuclear cells (PBMCs) in blood, using BSP, nested PCR, and bisulfite sequencing, and measured the in vivo gene expression of ADAM33 and the urinary concentrations of endocrine-disrupting chemicals (EDCs), using real-time PCR, high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). Only one dataset, GSE32393, reached significance (P=0.016). ADAM33 expression and methylation frequencies at CpG site 3 in intron 1 were higher in the control group. We found a positive association between intron 1 methylation level and ADAM33 expression as well as urinary concentrations of MEHHP, MECPP, MEOHP and Sigma 4MEHP (the sum of MEHP, MECPP, MEHHP, and MEOHP) in the cases. This study suggests that metabolites of phthalate such as MEHHP, MECPP, MEOHP and Sigma 4MEHP may increase the intron 1 methylation level to elevate ADAM33 gene expression and have a protective effect on reducing the risk of breast cancer.