Estrogen Receptor α, a Molecular Switch Converting Transforming Growth Factor-α-mediated Proliferation into Differentiation in Neuroblastoma Cells

Abstract

Transforming growth factor-␣ (TGF-␣) is known to promote both proliferation and differentiation of neural cell progenitors. Using the human neuroblastoma cell line SK-N-BE that is induced to proliferate by TGF-␣, we demonstrated that the expression of a single transcription factor, the estrogen receptor-␣ (ER␣), can reroute the TGF-␣ mitogenic signaling toward a path leading to differentiation. With selected mutations in ER␣ and signal transducer and activator of transcription 3 (Stat3), we demonstrated that the blockade of TGF-␣ mitotic potential was not dependent on ER␣ DNA binding activity but required a transcriptionally active Stat3. In neuroblastoma cells, 17␤-estradiol treatment induced a transient increase in the transcription of estrogen-responsive element-containing promoters including those regulating TGF-␣ and prothymosin ␣ synthesis. Based on the data presented, we hypothesized that in the presence of prothymosin ␣, ER␣ activates its direct target genes and increases cell proliferation, whereas in the presence of high levels of TGF-␣, ER␣ preferentially interacts with Stat3 and causes cell differentiation. Our results reveal a novel form of "end-product" regulation of an intracellular receptor that occurs through recruitment of membrane receptors and their signaling effector system. Cross-coupling between membrane and intracellular receptors has been described by several laboratories. This study proves the relevance of these interactions in cellular responses to growth factors.

Regulation of the Notch target gene Hes-1 by TGFα induced Ras/MAPK signaling in human neuroblastoma cells

“…In order to clarify the regulation of Hes-1 during mitogenic stimulation of neuroblastoma cells, we treated SK-N-BE(2)c cells with the EGFR ligand TGFa. In line with data published by other groups [27], we found a growth-promoting effect of TGFa, detected already at 24 h and maintained after 48 h in culture ( Figs. 1a and b).…”

“…In this report, we have analyzed the link between mitogen-activated protein kinase (MAPK) signaling and Hes-1 regulation by stimulating neuroblastoma cells with the transforming growth factor a (TGFa), which in previous studies have shown to be a mitogen of neuroblastoma cells [27]. We show that Hes-1 expression is directly correlated to the MAPK activity and that this induction is not mediated by increased signaling activity of the Notch receptors.…”

Effects of Estrogens and Endocrine-Disrupting Chemicals on Cell Differentiation–Survival–Proliferation in Brain: Contributions of Neuronal Cell Lines

“…E2 might still modulate via ERα the activity of other transcription factors including the AP-1 (Webb et al 1995) or Stat (Signal Transducer and Activator of Transcription) proteins (Bjornstrom and Sjoberg 2002). Ciana et al (2003) noted that ERα and Stat3 are functionally interact and are able to prevent TGFα-induced proliferation in the neuroblastoma cell line SK-N-BE. This protein/protein interaction subtracts ER from the binding to the ERE-containing promoters, shifting the cell program toward differentiation .…”

Cell cycle dependent oscillatory expression of estrogen receptor-α links Pol II elongation to neoplastic transformation

“…Cells (50 × 10 6 ) were incubated for 5 min in a lysis buffer (10 mM Tris·HCl, pH 7.4, 3 mM MgCl 2 , 0.5% Nonidet P-40, and 10 mM NaCl) and nuclei were pelleted by microfuge centrifugation. Nuclear run-on assays were performed as described (39). Four-h prehybridization and 24-h hybridization were carried on in Church and Gilbert's solution at 72°C; 2 × 10 6 cpm/mL were used in the hybridization reaction.…”