AREG and breast cancer: AREG was first discovered and purified from the conditioned medium of MCF-7 human breast cancer cells treated with phorbol 12-myristate 13-acetate, revealing a unique bifunctional growth-modulating glycoprotein that exhibited the distinctive ability to both stimulate the proliferation of normal fibroblasts and keratinocytes while simultaneously inhibiting the growth of certain aggressive cancer cell lines, thus earning its name from this amphipathic regulatory function [17].