Enhanced sensitivity to rapamycin following long-term oestrogen deprivation in MCF-7, T-47-D and ZR-75-1 human breast cancer cells.
Human breast cancer cells (MCF-7, T-47-D and ZR-75-1) can adapt to circumvent any reduced growth rate during long-term oestrogen deprivation, and this provides three model systems to investigate mechanisms of endocrine resistance in breast cancer. In this paper we report consistent differences in the effects of three growth inhibitors following long-term oestrogen deprivation in all three cell models. Long-term oestrogen deprivation of MCF-7, T-47-D and ZR-75-1 cells resulted in reduced growth inhibition by PD98059 (2-10 μg/ml), implying a loss of dependence on mitogen-activated protein kinase pathways for growth. The growth inhibitor LY294002 (2-10 μM) inhibited growth of both oestrogen-maintained and oestrogen-deprived cells with similar dose-responses, implying continued similar dependence on phosphoinositide 3-kinase (PI3K) pathways with no alteration after adaptation to oestrogen independent growth. However, by contrast, long-term oestrogen deprivation resulted in an increased sensitivity to growth inhibition by rapamycin, which was not reduced by readdition of oestradiol. The enhanced inhibition of long-term oestrogen-deprived MCF-7-ED, T-47-D-ED and ZR-75-1-ED cell growth by combining rapamycin with LY294002 at concentrations where each alone had little effect, offers preclinical support to the development of therapeutic combinations of rapamycin analogues with other PI3K inhibitors in endocrine-resistant breast cancer.
Biomedical Sciences Section, School of Biological Sciences, University of Reading, Hopkins Building, Whiteknights, Reading RG6 6UB, UK.
Swagat
S
Ray
Michael J
MJ
Fry
Philippa D
PD
Darbre
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002452:Cell Count; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002867:Chromones / Q000494:pharmacology; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004967:Estrogens / Q000172:deficiency*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002867:Chromones; D003470:Culture Media; D004967:Estrogens; D005419:Flavonoids; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D020123:Sirolimus; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one