Hypoxia activates the cyclin D1 promoter via the Jak2/STAT5b pathway in breast cancer cells.
Hypoxia, a common consequence of solid tumor growth in breast cancer or other cancers, serves to propagate a cascade of molecular pathways which include angiogenesis, glycolysis, and various cell-cycle control proteins. As we have shown previously, hypoxia activates STAT5 (signal transducer and activator of transcription 5) and increases its binding activity to the GAS element in mammary epithelial cells. In this study we attempted to elucidate the mechanism by which cyclin D1 is regulated by the STAT5 protein under hypoxic conditions. Our data demonstrate that hypoxia (2% O(2)) or desferrioxamine (DFO) induces tyrosine and serine phosphorylation of STAT5 in human breast cancer cells (MCF-7) and mammary epithelial cells (HC11). Imunoprecipitation and subsequent Western analysis showed that Jak2 leads to the tyrosine phosphorylation and activation of STAT5a or STAT5b under hypoxic conditions. Using a transfected COS-7 cell model system, we demonstrate that the activity of a cyclin D1 promoter-luciferase construct increased under hypoxic conditions or DFO treatment. The activity of the STAT5b/cyclin D1 promoter increased significantly by 12 h of hypoxia, whereas the activity of the STAT5a/cyclin D1 promoter was unaffected under hypoxic conditions. These increases in promoter activity are predominantly mediated by the Jak2/STAT5b signaling pathway. We have shown by EMSA that hypoxia induces STAT5 to bind to the cyclin D1 promoter (GAS-1) in MCF-7 and HC11 cells. These data suggest that STAT5b may mediate the transcriptional activation of cyclin D1 after hypoxic stimulation.
Joung
Youn Hee
YH
Department of Pathology, College of Medicine and Bio-Food and Drug Research Center, College of Biomedical and Health Science, Konkuk University, Chungju 380-701, Korea.
Lim
Eun Joung
EJ
Lee
Moon Young
MY
Park
Jong-Hwan
JH
Ye
Sang-Kyu
SK
Park
Eui U
EU
Kim
Sang Yoon
SY
Zhang
Zheng
Z
Lee
Kwang Jeon
KJ
Park
Dong Ki
DK
Park
Taekyu
T
Moon
Won Kook
WK
Yang
Young Mok
YM
D000693:Anaerobiosis / Q000235:genetics; D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D019556:COS Cells; D015687:Cell Hypoxia / Q000235:genetics; D002522:Chlorocebus aethiops; D019938:Cyclin D1 / Q000235:genetics*; D003676:Deferoxamine / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053614:Janus Kinase 2; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
D011518:Proto-Oncogene Proteins; D019938:Cyclin D1; D014443:Tyrosine; D012694:Serine; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D003676:Deferoxamine