title: Kinome-wide functional screen identifies role of PLK1 in hormone-independent, ER-positive breast cancer.
abstract: Estrogen receptor (ER) α-positive breast cancers initially respond to antiestrogens but eventually become estrogen independent and recur. ER(+) breast cancer cells resistant to long-term estrogen deprivation (LTED) exhibit hormone-independent ER transcriptional activity and growth. A kinome-wide siRNA screen using a library targeting 720 kinases identified Polo-like kinase 1 (PLK1) as one of the top genes whose downregulation resulted in inhibition of estrogen-independent ER transcriptional activity and growth of LTED cells. High PLK1 mRNA and protein correlated with a high Ki-67 score in primary ER(+) breast cancers after treatment with the aromatase inhibitor letrozole. RNAi-mediated knockdown of PLK1 inhibited ER expression, estrogen-independent growth, and ER transcription in MCF7 and HCC1428 LTED cells. Pharmacologic inhibition of PLK1 with volasertib, a small-molecule ATP-competitive PLK1 inhibitor, decreased LTED cell growth, ER transcriptional activity, and ER expression. Volasertib in combination with the ER antagonist, fulvestrant, decreased MCF7 xenograft growth in ovariectomized mice more potently than each drug alone. JUNB, a component of the AP-1 complex, was expressed 16-fold higher in MCF7/LTED compared with parental MCF7 cells. Furthermore, JUNB and BCL2L1 (which encodes antiapoptotic BCL-xL) mRNA levels were markedly reduced upon volasertib treatment in MCF7/LTED cells, while they were increased in parental MCF7 cells. Finally, JUNB knockdown decreased ER expression and transcriptional activity in MCF7/LTED cells, suggesting that PLK1 drives ER expression and estrogen-independent growth via JUNB. These data support a critical role of PLK1 in acquired hormone-independent growth of ER(+) human breast cancer and is therefore a promising target in tumors that have escaped estrogen deprivation therapy.
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Neil E
authors.initials: NE
authors.lastname: Bhola
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Valerie M
authors.initials: VM
authors.lastname: Jansen
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Bafna
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee. Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Giltnane
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee. Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Balko
authors.affiliation: Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Mónica V
authors.initials: MV
authors.lastname: Estrada
authors.affiliation: Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee. Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Meszoely
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee. Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Mayer
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee. Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Vandana
authors.initials: V
authors.lastname: Abramson
authors.affiliation: Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Fei
authors.initials: F
authors.lastname: Ye
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee. Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Melinda
authors.initials: M
authors.lastname: Sanders
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Teresa C
authors.initials: TC
authors.lastname: Dugger
authors.affiliation: Department of Medical Oncology, Broad Institute of MIT at Harvard, Cambridge, Massachusetts.
authors.forename: Eliezer V
authors.initials: EV
authors.lastname: Allen
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee. Breast Cancer Research Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee. Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, Tennessee. carlos.arteaga@vanderbilt.edu.
authors.forename: Carlos L
authors.initials: CL
authors.lastname: Arteaga
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004357:Drug Synergism; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D005260:Female; D000077267:Fulvestrant; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D008819:Mice, Nude; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011621:Pteridines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D011897:Random Allocation; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic; D023041:Xenograft Model Antitumor Assays; D051020:bcl-X Protein / Q000096:biosynthesis / Q000235:genetics; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D004958:Estradiol; D047628:Estrogen Receptor alpha; D000077267:Fulvestrant; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D011621:Pteridines; D034741:RNA, Small Interfering; D014157:Transcription Factors; D051020:bcl-X Protein; D000097869:Polo-Like Kinase 1; C494811:BCL2L1 protein, human; C541363:BI 6727; C506487:ESR1 protein, human; C581727:JunB protein, human