Identification of interleukin-8 as estrogen receptor-regulated factor involved in breast cancer invasion and angiogenesis by protein arrays

With the goal of identifying key factors involved in human breast cancer progression, we applied human cytokine antibody arrays we have developed to screen cytokine expression levels in human breast cancer cell lines and identified interleukin (IL)-8 as a key factor involved in breast cancer invasion and angiogenesis. Elevated expression of IL-8 in breast cancer cells was associated with breast cancer invasiveness and angiogenesis. Neutralization of antibody against IL-8 specifically blocked IL-8-mediated tumor cell invasion and angiogenesis. Furthermore, IL-8 levels in human breast cancer cells were closely related to estrogen receptor (ER) status. ER positive cells expressed low levels of IL-8 whereas ER negative cells expressed high levels of IL-8. Expression of exogenous ERα substantially inhibited IL-8 expression. Our findings raise intriguing questions regarding the role of IL-8 in the development and progression of human breast cancer in association with ER status.