Role of c-Myb during prolactin-induced signal transducer and activator of transcription 5a signaling in breast cancer cells.
Implicated in the pathogenesis of breast cancer, prolactin (PRL) mediates its function in part through the prolactin receptor (PRLr)-associated Janus kinase 2 (Jak2)/signal transducer and activator of transcription 5 (Stat5) signaling complex. To delineate the mechanisms of Stat5a regulation in breast cancer, transcription factor-transcription factor (TF-TF) array analysis was employed to identify associated transcriptional regulators. These analyses revealed a PRL-inducible association of Stat5a with the transcription factor and protooncogene c-Myb. Confirmatory co-immunoprecipitation studies using lysates from both T47D and MCF7 breast cancer cells revealed a PRL-inducible association between these transcription factors. Ectopic expression of c-Myb enhanced the PRL-induced expression from both composite and synthetic Stat5a-responsive luciferase reporters. Chromatin immunoprecipitation assays also revealed a PRL-inducible association between c-Myb and endogenous Stat5a-responsive CISH promoter, which was associated with an enhanced expression of CISH gene product at the RNA and protein levels. Small interfering RNA-mediated c-Myb knockdown impaired the PRL-induced mRNA expression of five Stat5-responsive genes. DNA binding-defective mutants of c-Myb, incapable of activating expression from a c-Myb-responsive reporter, maintained their ability to enhance a Stat5a-responsive reporter. At a cellular level, ectopic expression of c-Myb resulted in an increase in T47D proliferation. Taken together, these results indicate that c-Myb potentiates Stat5a-driven gene expression, possibly functioning as a Stat5a coactivator, in human breast cancer.
Fang
Feng
F
Department of Pathology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, USA.
Rycyzyn
Michael A
MA
Clevenger
Charles V
CV
D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D047369:Chromatin Immunoprecipitation; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D047468:Immunoprecipitation; D011388:Prolactin / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
D011388:Prolactin; D020598:Proto-Oncogene Proteins c-myb; D034741:RNA, Small Interfering; D050799:STAT5 Transcription Factor; D050826:Suppressor of Cytokine Signaling Proteins; D025521:Tumor Suppressor Proteins; C494092:STAT5A protein, human