title: Increased STAT1 signaling in endocrine-resistant breast cancer.
abstract: Proteomic profiling of the estrogen/tamoxifen-sensitive MCF-7 cell line and its partially sensitive (MCF-7/LCC1) and fully resistant (MCF-7/LCC9) variants was performed to identify modifiers of endocrine sensitivity in breast cancer. Analysis of the expression of 120 paired phosphorylated and non-phosphorylated epitopes in key oncogenic and tumor suppressor pathways revealed that STAT1 and several phosphorylated epitopes (phospho-STAT1(Tyr701) and phospho-STAT3(Ser727)) were differentially expressed between endocrine resistant and parental controls, confirmed by qRT-PCR and western blotting. The STAT1 inhibitor EGCG was a more effective inhibitor of the endocrine resistant MCF-7/LCC1 and MCF-7/LCC9 lines than parental MCF-7 cells, while STAT3 inhibitors Stattic and WP1066 were equally effective in endocrine-resistant and parental lines. The effects of the STAT inhibitors were additive, rather than synergistic, when tested in combination with tamoxifen in vitro. Expression of STAT1 and STAT3 were measured by quantitative immunofluorescence in invasive breast cancers and matched lymph nodes. When lymph node expression was compared to its paired primary breast cancer expression, there was greater expression of cytoplasmic STAT1 (∼3.1 fold), phospho-STAT3(Ser727) (∼1.8 fold), and STAT5 (∼1.5 fold) and nuclear phospho-STAT3(Ser727) (∼1.5 fold) in the nodes. Expression levels of STAT1 and STAT3 transcript were analysed in 550 breast cancers from publicly available gene expression datasets (GSE2990, GSE12093, GSE6532). When treatment with tamoxifen was considered, STAT1 gene expression was nearly predictive of distant metastasis-free survival (DMFS, log-rank p = 0.067), while STAT3 gene expression was predictive of DMFS (log-rank p<0.0001). Analysis of STAT1 and STAT3 protein expression in a series of 546 breast cancers also indicated that high expression of STAT3 protein was associated with improved survival (DMFS, p = 0.006). These results suggest that STAT signaling is important in endocrine resistance, and that STAT inhibitors may represent potential therapies in breast cancer, even in the resistant setting.
authors.affiliation: Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, Scotland, United Kingdom.
authors.forename: Rui
authors.initials: R
authors.lastname: Huang
authors.affiliation: Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, Scotland, United Kingdom.
authors.forename: Dana
authors.initials: D
authors.lastname: Faratian
authors.affiliation: Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, Scotland, United Kingdom.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Sims
authors.affiliation: Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, Scotland, United Kingdom.
authors.forename: Danielle
authors.initials: D
authors.lastname: Wilson
authors.affiliation: Department of Pathology, Western General Hospital, Edinburgh, Scotland, United Kingdom.
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Thomas
authors.affiliation: Pathology, Medical and Biological Sciences Building, University of St Andrews, North Haugh, St. Andrews, Fife, Scotland, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Harrison
authors.affiliation: Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, Scotland, United Kingdom.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Langdon
mesh_terms: D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D003499:Cyclic S-Oxides / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D016133:Polymerase Chain Reaction; D011725:Pyridines / Q000494:pharmacology; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D003499:Cyclic S-Oxides; D004967:Estrogens; D011725:Pyridines; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D020032:Tyrphostins; C519885:WP1066; C517409:stattic; D013629:Tamoxifen; D002392:Catechin; C045651:epigallocatechin gallate
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