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Type-I IGF receptor and acquired tamoxifen resistance in estrogen responsive human breast cancer cells

Lookup NU author(s): Dr Felicity May, Professor Bruce Westley


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Tamoxifen inhibited the oestrogen-stimulated proliferation of MCF-7 cells but had little effect on the oestrogen-stimulated proliferation of two tamoxifen-resistant variants (RL-3 and AL-1). The lack of oestrogen antagonist activity in the resistant cells was largely a result of an increased oestrogen agonist activity of tamoxifen on cell proliferation. Proliferation of the tamoxifen-resistant cells was also stimulated by 4-hydroxytamoxifen but not by ICI 164,384, a structurally distinct pure anti-oestrogen. Tamoxifen does not have increased oestrogen agonist activity for the induction of a series of oestrogen-regulated RNAs, and this suggests that the increased agonist activity may be restricted to key components involved in the proliferative response. Tamoxifen-stimulated cell proliferation was dependent on insulin-like growth factor I(IGF-1) in the resistant cells, suggesting that tamoxifen stimulates cell proliferation by sensitising cells to the proliferative effects of IGF-l. This may involve induction of the type-I IGF receptor.

Publication metadata

Author(s): Wiseman LR, Johnson MD, Wakeling AE, Lykkesfeldt AE, May FEB, Westley BR

Publication type: Article

Publication status: Published

Journal: European Journal of Cancer

Year: 1993

Volume: 29A

Issue: 16

Pages: 2256-2264

Print publication date: 01/01/1993

ISSN (print): 0959-8049

ISSN (electronic): 1879-0852


DOI: 10.1016/0959-8049(93)90218-5


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