IRS1 and breast carcinoma: In contrast to this inhibition, Chen et al. [127] demonstrated that lower concentrations (1 mM) of genistein increased the proliferation of MCF-7 human breast cancer cells by increasing the protein and mRNA content of the IGF-1 receptor (IGF-IR) and insulin receptor substrate-1 (IRS-1), enhancing tyrosine phosphorylation of IGF-IR and IRS-1.