Inhibition of estrogen receptor alpha expression and function in MCF-7 cells by kaempferol.
Estrogens are mitogenic for estrogen receptor (ER)-positive breast cancer cells. Current treatment of ER-positive breast tumors is directed towards interruption of estrogen activity. We report that treatment of ER-positive breast cancer cells with kaempferol resulted in a time- and dose-dependent decrease in cell number. The concentration required to produce 50% growth inhibition at 48 h was approximately 35.0 and 70.0 microM for ER-positive and ER-negative breast cancer cells, respectively. For MCF-7 cells, a reduction in the ER-alpha mRNA equivalent to 50, 12, 10% of controls was observed 24 h after treatment with 17.5, 35.0, and 70.0 microM of kaempferol, respectively. Concomitantly, these treatments led to a 58, 80, and 85% decrease in ER-alpha protein. The inhibitory effect of kaempferol on ER-alpha levels was seen as early as 6 h post-treatment. Kaempferol treatment also led in a dose-dependent decrease in the expression of progesterone receptor (PgR), cyclin D1, and insulin receptor substrate 1 (IRS-1). Immunocytochemical study revealed that ER-alpha protein in kaempferol-treated MCF-7 cells formed an aggregation in the nuclei. Kaempferol also induced degradation of ER-alpha by a different pathway than that were observed for the antiestrogen ICI 182,780 and estradiol. Estradiol-induced MCF-7 cell proliferation and expression of the estrogen-responsive-element-reporter gene activity were abolished in cells co-treated with kaempferol. These findings suggest that modulation of ER-alpha expression and function by kaempferol may be, in part, responsible for its anti-proliferative effects seen in in vitro.
Hung
Huynh
H
Laboratory of Molecular Endocrinology, Division of Cellular and Molecular Research, National Cancer Centre of Singapore, Singapore. cmrhth@nccs.com.sg
D015152:Blotting, Northern; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects*; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000096:biosynthesis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D005260:Female; D000077267:Fulvestrant; D006801:Humans; D007150:Immunohistochemistry; D055504:Insulin Receptor Substrate Proteins; D044949:Kaempferols / Q000494:pharmacology*; D010750:Phosphoproteins / Q000096:biosynthesis / Q000187:drug effects; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000187:drug effects*; D011980:Receptors, Progesterone / Q000096:biosynthesis / Q000187:drug effects; D013997:Time Factors; D014162:Transfection
D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D044949:Kaempferols; D010750:Phosphoproteins; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D019938:Cyclin D1; D000077267:Fulvestrant; D004958:Estradiol; C006552:kaempferol