Ets-1 activates parathyroid hormone-related protein gene expression in tumorigenic breast epithelial cells.
Parathyroid hormone-related protein (PTHrP) is produced by many tumors not associated with humoral hypercalcemia, including breast cancers. In this study, we used three human immortalized mammary epithelial cell lines that differ in tumorigenicity and PTHrP expression. Using RT-PCR we investigated 5' and 3' alternative splicing of PTHrP transcripts and promoter usage in the lines. Increased levels of P3-derived transcripts and the 1-139 mRNA isoform were observed in the most tumorigenic cell line. Transient transfection experiments identified elements close to P3 promoter that appeared to account for a portion of differential PTHrP expression among the three cell lines. Using site-directed mutagenesis, a previously described Ets-1/Sp1 binding site upstream of P3 was determined to be crucial for full activity of this promoter. RT-PCR and western blot evaluation of Ets family member expression found that Ese-1 was present in all three lines, but that appreciable levels of Ets-1 protein were present exclusively in the most tumorigenic line. Cotransfection of Ets-1 expression vectors activated PTHrP reporter constructs in the most tumorigenic line but not in the other cell lines. These findings suggest a potential mechanism by which PTHrP transcription may be regulated as a consequence of events that promote tumorigenic behavior in breast epithelial cells.
Cataisson
Christophe
C
INSERM U349, Centre Viggo Petersen Hôpital Lariboisière, 6 rue Guy Patin 75010, Paris, France.
Gordon
Johnthan
J
Roussière
Mickael
M
Abdalkhani
Arman
A
Lindemann
Ralph
R
Dittmer
Jürgen
J
Foley
John
J
Bouizar
Zhor
Z
D017398:Alternative Splicing; D001943:Breast Neoplasms / Q000209:etiology* / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D042361:Mammary Glands, Human / Q000473:pathology*; D044162:Parathyroid Hormone-Related Protein / Q000235:genetics*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000032:analysis; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000502:physiology*; D050783:Proto-Oncogene Proteins c-ets; D012333:RNA, Messenger / Q000032:analysis; D014157:Transcription Factors / Q000032:analysis / Q000502:physiology*
C494041:ETS1 protein, human; D044162:Parathyroid Hormone-Related Protein; D020033:Protein Isoforms; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D012333:RNA, Messenger; D014157:Transcription Factors