Our earlier work revealed that MPA induces the rapid phosphorylation of Stat3 and ErbB-2 in breast cancer cells and the assembly of a transcriptional complex between Stat3 and ErbB-2 at the Stat3 binding sites (GAS) in human (position −984) and mouse (positons −971 and −874) cyclin D1 promoters[9]. Here, STAT3 is linked to breast cancer.