Philippa D Darbre1. 1. School of Biological Sciences, University of Reading, Hopkins Building, Whiteknights, Reading RG6 6UB, U.K. p.d.darbre@reading.ac.uk.
Abstract
BACKGROUND: Efficacy of endocrine therapy is compromised when human breast cancer cells circumvent imposed growth inhibition. The model of long-term oestrogen-deprived MCF-7 human breast cancer cells has suggested the mechanism results from hypersensitivity to low levels of residual oestrogen. MATERIALS AND METHODS: MCF-7 cells were maintained for up to 30 weeks in phenol-red-free medium and charcoal-stripped serum with 10(-8) M 17β-oestradiol and 10 μg/ml insulin (stock 1), 10(-8) M 17β-oestradiol (stock 2), 10 μg/ml insulin (stock 3) or no addition (stock 4). RESULTS: Loss of growth response to oestrogen was observed only in stock 4 cells. Long-term maintenance with insulin in the absence of oestradiol (stock 3) resulted in raised oestrogen receptor-alpha (ERα) levels (measured by western immunoblotting) and development of hypersensitivity (assayed by oestrogen-responsive reporter gene induction and dose response to oestradiol for proliferation under serum-free conditions), but with no loss of growth response to oestrogen. CONCLUSION: Hypersensitivity can develop without any growth adaptation and therefore is not a prerequisite for loss of growth response in MCF-7 cells.
BACKGROUND: Efficacy of endocrine therapy is compromised when humanbreast cancer cells circumvent imposed growth inhibition. The model of long-term oestrogen-deprived MCF-7 humanbreast cancer cells has suggested the mechanism results from hypersensitivity to low levels of residual oestrogen. MATERIALS AND METHODS: MCF-7 cells were maintained for up to 30 weeks in phenol-red-free medium and charcoal-stripped serum with 10(-8) M 17β-oestradiol and 10 μg/ml insulin (stock 1), 10(-8) M 17β-oestradiol (stock 2), 10 μg/ml insulin (stock 3) or no addition (stock 4). RESULTS: Loss of growth response to oestrogen was observed only in stock 4 cells. Long-term maintenance with insulin in the absence of oestradiol (stock 3) resulted in raised oestrogen receptor-alpha (ERα) levels (measured by western immunoblotting) and development of hypersensitivity (assayed by oestrogen-responsive reporter gene induction and dose response to oestradiol for proliferation under serum-free conditions), but with no loss of growth response to oestrogen. CONCLUSION:Hypersensitivity can develop without any growth adaptation and therefore is not a prerequisite for loss of growth response in MCF-7 cells.
Entities:
Keywords:
Hypersensitivity; MCF-7 cells; breast cancer; insulin; oestrogen deprivation