|Title||Phosphorylated and sumoylation-deficient progesterone receptors drive proliferative gene signatures during breast cancer progression.|
|Publication Type||Journal Article|
|Year of Publication||2012|
|Authors||Knutson, TP, Daniel, AR, Fan, D, Silverstein, KAt, Covington, KR, Fuqua, SAw, Lange, CA|
|Journal||Breast Cancer Res|
|Keywords||Apoptosis, Breast Neoplasms, Cell Line, Tumor, Cell Proliferation, Cell Survival, Cyclic AMP Response Element-Binding Protein, Cyclin-Dependent Kinase 2, Disease Progression, DNA-Binding Proteins, Female, Gene Expression Profiling, Humans, MCF-7 Cells, Mitogen-Activated Protein Kinases, Neoplasm Proteins, Phosphorylation, Promoter Regions, Genetic, Receptor, ErbB-2, Receptors, Progesterone, Signal Transduction, Small Ubiquitin-Related Modifier Proteins, Sumoylation, Transcriptional Activation, Transcriptome|
INTRODUCTION: Progesterone receptors (PR) are emerging as important breast cancer drivers. Phosphorylation events common to breast cancer cells impact PR transcriptional activity, in part by direct phosphorylation. PR-B but not PR-A isoforms are phosphorylated on Ser294 by mitogen activated protein kinase (MAPK) and cyclin dependent kinase 2 (CDK2). Phospho-Ser294 PRs are resistant to ligand-dependent Lys388 SUMOylation (that is, a repressive modification). Antagonism of PR small ubiquitin-like modifier (SUMO)ylation by mitogenic protein kinases suggests a mechanism for derepression (that is, transcriptional activation) of target genes. As a broad range of PR protein expression is observed clinically, a PR gene signature would provide a valuable marker of PR contribution to early breast cancer progression.
METHODS: Global gene expression patterns were measured in T47D and MCF-7 breast cancer cells expressing either wild-type (SUMOylation-capable) or K388R (SUMOylation-deficient) PRs and subjected to pathway analysis. Gene sets were validated by RT-qPCR. Recruitment of coregulators and histone methylation levels were determined by chromatin immunoprecipitation. Changes in cell proliferation and survival were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and western blotting. Finally, human breast tumor cohort datasets were probed to identify PR-associated gene signatures; metagene analysis was employed to define survival rates in patients whose tumors express a PR gene signature.
RESULTS: 'SUMO-sensitive' PR target genes primarily include genes required for proliferative and pro-survival signaling. DeSUMOylated K388R receptors are preferentially recruited to enhancer regions of derepressed genes (that is, MSX2, RGS2, MAP1A, and PDK4) with the steroid receptor coactivator, CREB-(cAMP-response element-binding protein)-binding protein (CBP), and mixed lineage leukemia 2 (MLL2), a histone methyltransferase mediator of nucleosome remodeling. PR SUMOylation blocks these events, suggesting that SUMO modification of PR prevents interactions with mediators of early chromatin remodeling at 'closed' enhancer regions. SUMO-deficient (phospho-Ser294) PR gene signatures are significantly associated with human epidermal growth factor 2 (ERBB2)-positive luminal breast tumors and predictive of early metastasis and shortened survival. Treatment with antiprogestin or MEK inhibitor abrogated expression of SUMO-sensitive PR target-genes and inhibited proliferation in BT-474 (estrogen receptor (ER)+/PR+/ERBB2+) breast cancer cells.
CONCLUSIONS: We conclude that reversible PR SUMOylation/deSUMOylation profoundly alters target gene selection in breast cancer cells. Phosphorylation-induced PR deSUMOylation favors a permissive chromatin environment via recruitment of CBP and MLL2. Patients whose ER+/PR+ tumors are driven by hyperactive (that is, derepressed) phospho-PRs may benefit from endocrine (antiestrogen) therapies that contain an antiprogestin.
|Alternate Journal||Breast Cancer Res.|
|PubMed Central ID||PMC3446358|
|Grant List||R01 CA123763 / CA / NCI NIH HHS / United States |
R01 DK53825 / DK / NIDDK NIH HHS / United States
R21CA116790 / CA / NCI NIH HHS / United States