Down-regulation of epidermal growth factor receptor induced by estrogens and phytoestrogens promotes the differentiation of U2OS human osteosarcoma cells

• Published in: Journal of cellular physiology Vol. 220; no. 1; pp. 35 - 44
• Main Authors: Salvatori, Luisa, Caporuscio, Francesca, Coroniti, Giuseppe, Starace, Giuseppe, Frati, Luigi, Russo, Matteo Antonio, Petrangeli, Elisa
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-07-2009
• Subjects: Apoptosis - drug effects; Biomarkers - metabolism; Cell Cycle - drug effects; Cell Differentiation - drug effects; Cell Differentiation - genetics; Cell Line, Tumor; Cell Proliferation - drug effects; Cell Shape - drug effects; Down-Regulation; Estradiol - metabolism; Estrogen Receptor alpha - drug effects; Estrogen Receptor alpha - metabolism; Estrogen Receptor beta - drug effects; Estrogen Receptor beta - metabolism; Genistein - pharmacology; Humans; Isoflavones - pharmacology; Osteoblasts - drug effects; Osteoblasts - metabolism; Osteoblasts - pathology; Osteosarcoma - genetics; Osteosarcoma - metabolism; Osteosarcoma - pathology; Phytoestrogens - pharmacology; Receptor, Epidermal Growth Factor - drug effects; Receptor, Epidermal Growth Factor - genetics; Receptor, Epidermal Growth Factor - metabolism; RNA, Messenger - metabolism; Selective Estrogen Receptor Modulators - pharmacology; Tamoxifen - analogs & derivatives; Tamoxifen - pharmacology; Time Factors
• ISSN: 0021-9541; 1097-4652
• DOI: 10.1002/jcp.21724

In previous studies on HeLa cells we demonstrated estrogen‐responsiveness of the epidermal growth factor receptor (EGFR) gene, as 17β‐estradiol (E2) and selective estrogen receptor modulators (SERMs) genistein (G), daidzein (D), and 4‐hydroxytamoxifen (4OH‐T) modulated its transcription in a ligand‐ and estrogen receptor (ER) isoform‐specific way. This study describes further investigations into the role of ERs in mediating the effects induced by E2 and SERMs on EGFR expression, and the relationship between the actions of ERs and EGFR in U2OS osteosarcoma cells stably expressing ERα or ERβ. Cell number and DNA content determination revealed that E2, G, and D inhibited proliferation and cell cycle progression and promoted apoptosis in both cell lines. In parallel, changes in cell morphology typical of osteoblast maturation were observed via optical microscopy. Consistently, quantitative PCR and Western blot analysis showed an up‐regulation of markers of osteoblast differentiation and bone repair, and a decrease in EGFR expression. The transfection of specific antisense (AS) oligonucleotides strengthened our hypothesis that EGFR reduction caused changes in the proliferation/differentiation pattern comparable to those induced by ER ligands. The link between the ER and EGFR pathways was confirmed by treatment with 4OH‐T, which decreased the EGFR level and produced differentiation effects via ERα, but induced both EGFR expression and proliferation effects via ERβ. In conclusion, we show that also in U2OS cells, E2 and SERMs are able to modulate the expression of the EGFR gene and can affect events strictly controlled by its signaling pathway, such as the maturation of osteoblasts. J. Cell. Physiol. 220: 35–44, 2009. © 2009 Wiley‐Liss, Inc.