Proteomic Analysis of Acquired Tamoxifen Resistance in MCF-7 Cells Reveals Expression Signatures Associated with Enhanced Migration

Funding Source

U.S. Department of Agriculture , Department of Defense, Louisiana Cancer Research Consortium (LCRC), Office of Naval Research Grant, National Center for Research Resources RCMI program , National Institutes of Health

Grant Number

58-6435-7-019, W81XWH-04-1-0557, N00014-99-1-0763, 5G12RR026260-02, CA125806 (MEB)


Department of Chemistry

Document Type


Publication Date



Introduction: Acquired tamoxifen resistance involves complex signaling events that are not yet fully understood. Successful therapeutic intervention to delay the onset of hormone resistance depends critically on mechanistic elucidation of viable molecular targets associated with hormone resistance. This study was undertaken to investigate the global proteomic alterations in a tamoxifen resistant MCF-7 breast cancer cell line obtained by long term treatment of the wild type MCF-7 cell line with 4-hydroxytamoxifen (4-OH Tam).Methods: We cultured MCF-7 cells with 4-OH Tam over a period of 12 months to obtain the resistant cell line. A gel-free, quantitative proteomic method was used to identify and quantify the proteome of the resistant cell line. Nano-flow high-performance liquid chromatography coupled to high resolution Fourier transform mass spectrometry was used to analyze fractionated peptide mixtures that were isobarically labeled from the resistant and control cell lysates. Real time quantitative PCR and Western blots were used to verify selected proteomic changes. Lentiviral vector transduction was used to generate MCF-7 cells stably expressing S100P. Online pathway analysis was performed to assess proteomic signatures in tamoxifen resistance. Survival analysis was done to evaluate clinical relevance of altered proteomic expressions.Results: Quantitative proteomic analysis revealed a wide breadth of signaling events during transition to acquired tamoxifen resistance. A total of 629 proteins were found significantly changed with 364 up-regulated and 265 down-regulated. Collectively, these changes demonstrated the suppressed state of estrogen receptor (ER) and ER-regulated genes, activated survival signaling and increased migratory capacity of the resistant cell line. The protein S100P was found to play a critical role in conferring tamoxifen resistance and enhanced cell motility.Conclusions: Our data demonstrate that the adaptive changes in the proteome of tamoxifen resistant breast cancer cells are characterized by down-regulated ER signaling, activation of alternative survival pathways, and enhanced cell motility through regulation of the actin cytoskeleton dynamics. Evidence also emerged that S100P mediates acquired tamoxifen resistance and migration capacity.


DOI: 10.1186/bcr3144

PubMed ID: 22417809


This study was supported by a cooperative agreement with the U.S. Department of Agriculture Grant 58-6435-7-019; Department of Defense Grant W81XWH-04-1-0557; the Louisiana Cancer Research Consortium (LCRC); Office of Naval Research Grant N00014-99-1-0763, National Center for Research Resources RCMI program through Grant 5G12RR026260-02, and NIH grant CA125806 (MEB).