Autocrine regulation of cell proliferation by estrogen receptor-alpha in estrogen receptor-alpha-positive breast cancer cell lines

Abstract

BackgroundEstrogen receptor-α (ERα) is essential for mammary gland development and is a major oncogene in breast cancer. Since ERα is not colocalized with the cell proliferation marker Ki-67 in the normal mammary glands and the majority of primary breast tumors, it is generally believed that paracrine regulation is involved in ERα mediated cell proliferation. In the paracrine model, ERα-positive cells don't proliferate but will release some paracrine growth factors to stimulate the neighboring cells to proliferate. In a subpopulation of cancer cells in some primary breast tumors, however, ERα does colocalize with the cell proliferation marker Ki-67, suggesting an autocrine regulation by ERα in some primary breast tumors.MethodsColocalization of ERα with Ki-67 in ERα-positive breast cancer cell lines (MCF-7, T47D, and ZR75-1) was evaluated by immunofluorescent staining. Cell cycle phase dependent expression of ERα was determined by co-immunofluorescent staining of ERα and the major cyclins (D, E, A, B), and by flow cytometry analysis of ERαhigh cells. To further confirm the autocrine action of ERα, MCF-7 cells were growth arrested by ICI182780 treatment, followed by treatment with EGFR inhibitor, before estrogen stimulation and analyses for colocalization of Ki-67 and ERα and cell cycle progression.ResultsColocalization of ERα with Ki-67 was present in all three ERα-positive breast cancer cell lines. Unlike that in the normal mammary glands and the majority of primary breast tumors, ERα is highly expressed throughout the cell cycle in MCF-7 cells. Without E2 stimulation, MCF-7 cells released from ICI182780 treatment remain at G1 phase. E2 stimulation of ICI182780 treated cells, however, promotes the expression and colocalization of ERα and Ki-67 as well as the cell cycle progressing through the S and G2/M phases. Inhibition of EGFR signaling does not inhibit the autocrine action of ERα.ConclusionOur data indicate that ERα can mediate estrogen-induced cell proliferation in an autocrine mode in ERα-positive breast cancer cell lines. All of the three ERα-positive cell lines used in our study showed colocalization of ERα and Ki-67, indicating that these cell lines might be originated from primary tumor cells with autocrine regulation.

High glucose and insulin differentially modulates proliferation in MCF-7 and MDA-MB-231 cells

“…Estrogen and ERs promote proliferation and survival of breast cancer cells (Tan et al 2009). Moreover, oxidative stress is also reported to influence the regulation of ER (Tamir et al 2002) and induces its phosphorylation at serine 118 and 167 (Weitsman et al 2009).…”

Potent genistein derivatives as inhibitors of estrogen receptor alpha-positive breast cancer

“…4-Hydroxybenzyl 2,4,6-trihydroxyphenylketone (1). Phloroglucinol (1.158 g, 9.1 mmol) and 4-hydroxyphenylacetonitrile (1.34 g, 10.0 mmol) in diethyl ether (10 mL) were cooled in an ice bath and saturated with dry HCl gas for 12 h. The precipitate after the addition of diethyl ether was collected and washed further with diethyl ether.…”

“…The organic layer separated was purified by column chromatography using 60-120 SiO 2 mesh with EtOAc:Hexane (1:9) as eluent to yield the oily product 10 (0.46 g, 70.7%). 1 H NMR (400 MHz, CDCl 3 ) δ was removed and the reaction mixture was diluted with ethyl acetate and water, and the separated organic layer was concentrated and purified by column chromatography using a 60-120 SiO 2 mesh with EtOAc:Hexane (3:7) as eluent to yield 0.26 g (72%) of compound 7 in solid form. 1 Hydroxy-3-(4-hydroxy-phenyl) -7-[2-(4-phenyl-[1,2,3] triazol-1-yl)-ethoxy]-chromen-4-one (8).…”

“…1 H NMR (400 MHz, CDCl 3 ) δ was removed and the reaction mixture was diluted with ethyl acetate and water, and the separated organic layer was concentrated and purified by column chromatography using a 60-120 SiO 2 mesh with EtOAc:Hexane (3:7) as eluent to yield 0.26 g (72%) of compound 7 in solid form. 1 Hydroxy-3-(4-hydroxy-phenyl) -7-[2-(4-phenyl-[1,2,3] triazol-1-yl)-ethoxy]-chromen-4-one (8). Azide 7 (0.25 g, 0.73 mmol) in DMSO-H 2 O (1:1, v/v, 6 mL) was added to alkyne (0.96 mL, 0.88 mmol) at room temperature followed by addition of three drops of 1 M CuSO 4 , and also catalytic addition of sodium ascorbate and the reaction was stirred for 20 h. The reaction mixture was diluted with water and ethyl acetate, and the separated organic layer was concentrated and purified by column chromatography using 60-120 SiO 2 mesh with EtOAc:Hexane (4:6) as eluent to yield 0.2 g (62.5%) of compound 8 as solid.…”

“…ERα is essential for mammary gland development and plays a central role in breast cancer development, but ERα can mediate estrogen-induced cell proliferation in an autocrine mode in ERα positive breast cancer cell lines. 1 Although estrogen acts to stimulate the growth of estrogendependent tumors in vivo, reports also suggest that estrogen and estrogen agonists can act as preventive agents to inhibit growth of carcinogen induced mammary tumors in laboratory animals. 2,3 The biological actions of estrogens are mediated by interacting with two specific estrogen receptors, ERα and ERβ, which belong to the nuclear receptor superfamily of ligandregulated transcription factors.…”