HES-1 inhibits 17beta-estradiol and heregulin-beta1-mediated upregulation of E2F-1.
We have previously shown that expression of the transcription factor HES-1 is required for the growth-inhibitory effect of all-trans retinoic acid on MCF-7 cells. In this study, we have used T47D cells with tetracyclin-regulated expression of wild-type or a dominant-negative form of HES-1. Expression of HES-1 in T47D cells inhibited G1/S-phase transition and activation of Cdk2 elicited by estrogen. Estrogen treatment of T47D cells caused increased expression of E2F-1, and this expression was inhibited by cotreatment with all-trans retinoic acid. We show that the effect is mediated through HES-1, which directly downregulates E2F-1 expression through a CACGAG-site within the E2F-1 promoter. Furthermore, proliferation caused by heregulin-beta1 treatment of T47D cells was inhibited by all-trans retinoic acid and this effect was mediated by HES-1. Interestingly, heregulin-beta1-mediated upregulation of E2F-1 expression was directly inhibited by HES-1 through the same CACGAG-site as seen with estrogen-stimulated induction. In addition, we found that two important downstream target genes of estrogen and heregulin-beta1 that are regulated through E2F-1, cyclin E and NPAT, were both regulated in a similar fashion by all-trans retinoic acid, and these effects were antagonized by dominant-negative HES-1. These findings establish that HES-1 inhibits both estrogen- and heregulin-beta1-stimulated growth of breast cancer cells, and further suggest that growth inhibition induced in these cells by all-trans retinoic acid occurs via HES-1-mediated downregulation of E2F-1 expression.
Center for Biotechnology, Department of BioSciences, Karolinska Institutet, Novum, S-141 57 Huddinge Sweden.
Johan
J
Hartman
Patrick
P
Müller
James S
JS
Foster
Jay
J
Wimalasena
Jan-Ake
JA
Gustafsson
Anders
A
Ström
D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000502:physiology*; D045744:Cell Line, Tumor; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000502:physiology*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D024202:Electrophoretic Mobility Shift Assay; D004958:Estradiol / Q000502:physiology*; D005434:Flow Cytometry; D018398:Homeodomain Proteins / Q000502:physiology*; D006801:Humans; D020890:Neuregulin-1 / Q000502:physiology*; D016133:Polymerase Chain Reaction; D000072056:Transcription Factor HES-1; D014157:Transcription Factors / Q000502:physiology*; D015854:Up-Regulation / Q000502:physiology*
D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004958:Estradiol; D018398:Homeodomain Proteins; D020890:Neuregulin-1; D000072056:Transcription Factor HES-1; D014157:Transcription Factors; C493753:E2F1 protein, human; C078493:HES1 protein, human; C087230:heregulin beta1