Prolactin-inducible Stat5a-mediated and Stat5b-mediated gene profiles

Stat5a and Stat5b proteins are highly homologous with greater than 90% amino acid identity and share binding to the palindromic Stat5 consensus sequence, TTCNNNGAA, but individual roles of each transcription factor in breast cancer have not been thoroughly evaluated. To determine the degree of similarity between transcripts modulated by Stat5a and Stat5b proteins in human breast cancer, we utilized genome-wide transcript profiling to identify genes regulated specifically by Stat5a or Stat5b in response to prolactin. Stat5a or Stat5b was transiently overexpressed using adenoviral gene delivery in MCF7 breast cancer cells followed 16 hr serum starvation and a brief 4 hr exposure to 10nM human prolactin to identify immediate-early transcripts modulated by each transcription factor. Basal activation of Stat5a or Stat5b was not present in cells not stimulated with prolactin. mRNA from each condition was harvested and validated using the Agilent bioanalyzer. cDNA was generated and genome-wide transcript profiling was performed in triplicate using the Affymetrix HuGene 1.0 ST array.