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Linda J. Sealy, Ph.D.

Associate Professor of Cancer Biology, Cell and Developmental Biology, Molecular Physiology and Biophysics
Researcher

Contact Information:

Vanderbilt University Medical Center
752 Preston Building
Nashville, TN 37232-0615
615-322-3224

Research Description

It is the ability to metastasize that ultimately makes breast cancer a fatal disease. Metastatic cells are often characterized as having undergone an epithelial to mesenchymal transition (EMT). EMT is a common feature of both embryonic development and invasive tumors where epithelial cells dedifferentiate to a more fibroblast-like state and regain the ability to invade, migrate, and/or proliferate in an uncontrolled fashion. Mayny studies have sought to define the genes and signaling pathways that underlie the conversion to EMT and metastasis in breast cancer. Much less emphasis has been placed on identifying the transcription factors that ultimately control this process.

We have recently developed a new model for EMT in human breast cancer involving the transcription factor CCAAT/Enhancer Binding Protein (C/EBP)beta. C/EBPbeta is critical for growth and differentiation of the mammary gland. Increased mammary epithelial cell proliferation, migration, and branching during puberty or early pregnancy and differentiation at late pregnancy are severely impaired in C/EBPbeta null mice which fail to lactate. 3 isoforms of C/EBPbeta can be produced in cells via alternative translation initiation at 3 in-frame methionines. C/EBPbeta-1 and beta-2 are transactivators, and differ by only 23 N-terminal amino acids present in beta-1 but not beta-2. C/EBPbeta-3, lacks the N-terminal half of C/EBPbeta including the transactivation domain, and therefore represses transcription. C/EBPbeta-1 is the only isoform present in normal tissue from reduction mammoplasty. However, 70% of invasive surgical primary breast tumor samples have acquired a high level of C/EBPbeta-2 expression, and C/EBPbeta-2 is the only transactivator isoform expressed in breast cancer cell lines.

Although it was first assumed that C/EBPbeta-1 and ¿2 would be functionally redundant transactivators because of their extensive similarity, their different expression patterns suggest otherwise. In fact, MCF10A normal human mammary epithelial cells overexpressing C/EBPbeta-2, but not C/EBPbeta-1, undergo EMT and acquire an invasive phenotype. MCF10A C/EBPbeta-2 cells are anchorage-independent, form foci in soft agar, show loss of junctional E cadherin localization, exhibit cytoskeletal reorganization with actin stress fibers typical of motile fibroblasts, express vimentin, and are invasive in vitro.

From these and other studies we propose that C/EBPbeta-1 and -2 govern different phases of mammary gland development. C/EBPbeta-1 may be required for terminal differentiation during late pregnancy and lactation (likely activating milk protein genes), whereas ductal epithelial outgrowth and invasion through the stromal fat pad during puberty is the dominion of C/EBPbeta-2. Abberant C/EBPbeta-2 expression during cancer progression may activate a genetic program of motility and invasion in breast tumor cells.

Currently, we are extending our studies into animal models. We are evaluating if expression of C/EBPbeta-2 in breast cancer cell lines that are not invasive (MCF7, BT20) will cause the cells to undergo EMT and metastasize once implanted as xenografts in the mammary gland. We have also generated mice carrying an MMTV-driven C/EBPbeta -2 transgene; virgin females exhibit precocious, hyperplastic mammary gland development whereas multiparous females develop tumors. We will continue to study these animals to determine if females show accelerated development of metastatic carcinoma when crossed with other mouse models of breast cancer. Understanding the transcription factors responsible for metastatic capability, of which C/EBPbeta-2 is an enticing candidate, will accelerate the design of molecularly-targeted therapies capable of slowing or halting the often fatal spread of breast cancer to secondary sites.

Publications
  • Tripathi MK, Misra S, Khedkar SV, Hamilton N, Irvin-Wilson C, Sharan C, Sealy L, Chaudhuri G. Regulation of BRCA2 gene expression by the SLUG repressor protein in human breast cells. J. Biol. Chem [print-electronic]. 2005 Apr 4/29/2005; 280(17): 17163-71. PMID: 15734731, PMCID: PMC3092429, PII: M501375200, DOI: 10.1074/jbc.M501375200, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/15734731.
  • Bundy L, Wells S, Sealy L. C/EBPbeta-2 confers EGF-independent growth and disrupts the normal acinar architecture of human mammary epithelial cells. Mol. Cancer. 2005; 4: 43. PMID: 16371159, PMCID: PMC1360092, PII: 1476-4598-4-43, DOI: 10.1186/1476-4598-4-43, ISSN: 1476-4598.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/16371159.
  • Eaton EM, Sealy L. Modification of CCAAT/enhancer-binding protein-beta by the small ubiquitin-like modifier (SUMO) family members, SUMO-2 and SUMO-3. J. Biol. Chem [print-electronic]. 2003 Aug 8/29/2003; 278(35): 33416-21. PMID: 12810706, PII: M305680200, DOI: 10.1074/jbc.M305680200, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/12810706.
  • Qiao L, Han SI, Fang Y, Park JS, Gupta S, Gilfor D, Amorino G, Valerie K, Sealy L, Engelhardt JF, Grant S, Hylemon PB, Dent P. Bile acid regulation of C/EBPbeta, CREB, and c-Jun function, via the extracellular signal-regulated kinase and c-Jun NH2-terminal kinase pathways, modulates the apoptotic response of hepatocytes. Mol. Cell. Biol. 2003 May; 23(9): 3052-66. PMID: 12697808, PMCID: PMC153195, ISSN: 0270-7306.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/12697808.
  • Bundy LM, Sealy L. CCAAT/enhancer binding protein beta (C/EBPbeta)-2 transforms normal mammary epithelial cells and induces epithelial to mesenchymal transition in culture. Oncogene. 2003 Feb 2/13/2003; 22(6): 869-83. PMID: 12584567, PII: 1206216, DOI: 10.1038/sj.onc.1206216, ISSN: 0950-9232.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/12584567.
  • Ireton RC, Davis MA, van Hengel J, Mariner DJ, Barnes K, Thoreson MA, Anastasiadis PZ, Matrisian L, Bundy LM, Sealy L, Gilbert B, van Roy F, Reynolds AB. A novel role for p120 catenin in E-cadherin function. J. Cell Biol [print-electronic]. 2002 Nov 11/11/2002; 159(3): 465-76. PMID: 12427869, PMCID: PMC2173073, PII: jcb.200205115, DOI: 10.1083/jcb.200205115, ISSN: 0021-9525.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/12427869.
  • Duong DT, Waltner-Law ME, Sears R, Sealy L, Granner DK. Insulin inhibits hepatocellular glucose production by utilizing liver-enriched transcriptional inhibitory protein to disrupt the association of CREB-binding protein and RNA polymerase II with the phosphoenolpyruvate carboxykinase gene promoter. J. Biol. Chem [print-electronic]. 2002 Aug 8/30/2002; 277(35): 32234-42. PMID: 12070172, PII: M204873200, DOI: 10.1074/jbc.M204873200, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/12070172.
  • Hanlon M, Sturgill TW, Sealy L. ERK2- and p90(Rsk2)-dependent pathways regulate the CCAAT/enhancer-binding protein-beta interaction with serum response factor. J. Biol. Chem [print-electronic]. 2001 Oct 10/19/2001; 276(42): 38449-56. PMID: 11500490, PII: M102165200, DOI: 10.1074/jbc.M102165200, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/11500490.
  • Eaton EM, Hanlon M, Bundy L, Sealy L. Characterization of C/EBPbeta isoforms in normal versus neoplastic mammary epithelial cells. J. Cell. Physiol. 2001 Oct; 189(1): 91-105. PMID: 11573208, PII: 10.1002/jcp.1139, DOI: 10.1002/jcp.1139, ISSN: 0021-9541.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/11573208.
  • Mobley CM, Sealy L. The Rous sarcoma virus long terminal repeat promoter is regulated by TFII-I. J. Virol. 2000 Jul; 74(14): 6511-9. PMID: 10864664, PMCID: PMC112160, ISSN: 0022-538X.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/10864664.
  • Hanlon M, Bundy LM, Sealy L. C/EBP beta and Elk-1 synergistically transactivate the c-fos serum response element. BMC Cell Biol [print-electronic]. 2000; 1: 2. PMID: 11151091, PMCID: PMC29063, DOI: 10.1186/1471-2121-1-2, ISSN: 1471-2121.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/11151091.
  • Liao J, Piwien-Pilipuk G, Ross SE, Hodge CL, Sealy L, MacDougald OA, Schwartz J. CCAAT/enhancer-binding protein beta (C/EBPbeta) and C/EBPdelta contribute to growth hormone-regulated transcription of c-fos. J. Biol. Chem. 1999 Oct 10/29/1999; 274(44): 31597-604. PMID: 10531366, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/10531366.
  • Hanlon M, Sealy L. Ras regulates the association of serum response factor and CCAAT/enhancer-binding protein beta. J. Biol. Chem. 1999 May 5/14/1999; 274(20): 14224-8. PMID: 10318842, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/10318842.
  • Mobley CM, Sealy L. Role of the transcription start site core region and transcription factor YY1 in Rous sarcoma virus long terminal repeat promoter activity. J. Virol. 1998 Aug; 72(8): 6592-601. PMID: 9658104, PMCID: PMC109838, ISSN: 0022-538X.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/9658104.
  • Sealy L, Malone D, Pawlak M. Regulation of the cfos serum response element by C/EBPbeta. Mol. Cell. Biol. 1997 Mar; 17(3): 1744-55. PMID: 9032301, PMCID: PMC231899, ISSN: 0270-7306.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/9032301.
  • Sealy L, Mota F, Rayment N, Tatnell P, Kay J, Chain B. Regulation of cathepsin E expression during human B cell differentiation in vitro. Eur. J. Immunol. 1996 Aug; 26(8): 1838-43. PMID: 8765029, DOI: 10.1002/eji.1830260826, ISSN: 0014-2980.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/8765029.
  • Hann SR, Dixit M, Sears RC, Sealy L. The alternatively initiated c-Myc proteins differentially regulate transcription through a noncanonical DNA-binding site. Genes Dev. 1994 Oct 10/15/1994; 8(20): 2441-52. PMID: 7958908, ISSN: 0890-9369.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/7958908.
  • Sears RC, Sealy L. Multiple forms of C/EBP beta bind the EFII enhancer sequence in the Rous sarcoma virus long terminal repeat. Mol. Cell. Biol. 1994 Jul; 14(7): 4855-71. PMID: 8007984, PMCID: PMC358858, ISSN: 0270-7306.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/8007984.
  • Briggs RC, Briggs JA, Ozer J, Sealy L, Dworkin LL, Kingsmore SF, Seldin MF, Kaur GP, Athwal RS, Dessypris EN. The human myeloid cell nuclear differentiation antigen gene is one of at least two related interferon-inducible genes located on chromosome 1q that are expressed specifically in hematopoietic cells. Blood. 1994 Apr 4/15/1994; 83(8): 2153-62. PMID: 7512843, ISSN: 0006-4971.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/7512843.
  • Svaren J, Klebanow E, Sealy L, Chalkley R. Analysis of the competition between nucleosome formation and transcription factor binding. J. Biol. Chem. 1994 Mar 3/25/1994; 269(12): 9335-44. PMID: 8132673, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/8132673.
  • Ozer J, Chalkley R, Sealy L. Characterization of rat pseudogenes for enhancer factor I subunit A: ripping provides clues to the evolution of the EFIA/dbpB/YB-1 multigene family. Gene. 1993 Nov 11/15/1993; 133(2): 187-95. PMID: 8224907, ISSN: 0378-1119.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/8224907.
  • Ozer J, Chalkley R, Sealy L. Isolation of the CCAAT transcription factor subunit EFIA cDNA and a potentially functional EFIA processed pseudogene from Bos taurus: insights into the evolution of the EFIA/dbpB/YB-1 gene family. Gene. 1993 Feb 2/28/1993; 124(2): 223-30. PMID: 8444345, ISSN: 0378-1119.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/8444345.
  • Sears RC, Sealy L. Characterization of nuclear proteins that bind the EFII enhancer sequence in the Rous sarcoma virus long terminal repeat. J. Virol. 1992 Nov; 66(11): 6338-52. PMID: 1328670, PMCID: PMC240126, ISSN: 0022-538X.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/1328670.
  • Boulden AM, Sealy LJ. Maximal serum stimulation of the c-fos serum response element requires both the serum response factor and a novel binding factor, SRE-binding protein. Mol. Cell. Biol. 1992 Oct; 12(10): 4769-83. PMID: 1328862, PMCID: PMC360404, ISSN: 0270-7306.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/1328862.
  • Faber M, Sealy L. Rous sarcoma virus enhancer factor I is a ubiquitous CCAAT transcription factor highly related to CBF and NF-Y. J. Biol. Chem. 1990 Dec 12/25/1990; 265(36): 22243-54. PMID: 2176209, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/2176209.
  • Ozer J, Faber M, Chalkley R, Sealy L. Isolation and characterization of a cDNA clone for the CCAAT transcription factor EFIA reveals a novel structural motif. J. Biol. Chem. 1990 Dec 12/25/1990; 265(36): 22143-52. PMID: 1967130, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/1967130.
  • Greuel BT, Sealy L, Majors JE. Transcriptional activity of the Rous sarcoma virus long terminal repeat correlates with binding of a factor to an upstream CCAAT box in vitro. Virology. 1990 Jul; 177(1): 33-43. PMID: 2162108, ISSN: 0042-6822.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/2162108.
  • Boulden A, Sealy L. Identification of a third protein factor which binds to the Rous sarcoma virus LTR enhancer: possible homology with the serum response factor. Virology. 1990 Jan; 174(1): 204-16. PMID: 2152992, ISSN: 0042-6822.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/2152992.
  • Sealy L, Burgess RR, Cotten M, Chalkley R. Purification of Xenopus egg nucleoplasmin and its use in chromatin assembly in vitro. Meth. Enzymol. 1989; 170: 612-30. PMID: 2549340, PII: 0076-6879(89)70068-9, ISSN: 0076-6879.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/2549340.
  • Sealy, L., Cotten, M., Burgess, R., and Chalkley, R. Wassarman, P. and Kornberg, R. (Eds.). Preparation of Nucleoplasmin and Reconstitution of Nucleosomes. In Methods in Enzymology: Nucleosomes. Academic Press, Inc. 1989; 612-29.
  • Sealy, L. and Chalkley, R. At Least Two Nuclear Proteins Bind Specifically to the Rous Sarcoma Virus Long Terminal Repeat Enhancer. Mol. Cell. Biol. 1987; 7: 787-98.
  • Sealy L, Cotten M, Chalkley R. Novobiocin inhibits passive chromatin assembly in vitro. EMBO J. 1986 Dec 12/1/1986; 5(12): 3305-11. PMID: 3028779, PMCID: PMC1167327, ISSN: 0261-4189.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/3028779.
  • Cotten M, Sealy L, Chalkley R. Massive phosphorylation distinguishes Xenopus laevis nucleoplasmin isolated from oocytes or unfertilized eggs. Biochemistry. 1986 Sep 9/9/1986; 25(18): 5063-9. PMID: 3768332, ISSN: 0006-2960.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/3768332.
  • Sealy L, Cotten M, Chalkley R. Xenopus nucleoplasmin: egg vs. oocyte. Biochemistry. 1986 May 5/20/1986; 25(10): 3064-72. PMID: 3521726, ISSN: 0006-2960.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/3521726.
  • Cotten M, Bresnahan D, Thompson S, Sealy L, Chalkley R. Novobiocin precipitates histones at concentrations normally used to inhibit eukaryotic type II topoisomerase. Nucleic Acids Res. 1986 May 5/12/1986; 14(9): 3671-86. PMID: 3714493, PMCID: PMC339807, ISSN: 0305-1048.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/3714493.
  • Sealy L, Moscovici G, Moscovici C, Bishop JM. Site-specific mutagenesis of avian erythroblastosis virus: v-erb-A is not required for transformation of fibroblasts. Virology. 1983 Oct 10/15/1983; 130(1): 179-94. PMID: 6314644, ISSN: 0042-6822.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/6314644.
  • Sealy L, Privalsky ML, Moscovici G, Moscovici C, Bishop JM. Site-specific mutagenesis of avian erythroblastosis virus: erb-B is required for oncogenicity. Virology. 1983 Oct 10/15/1983; 130(1): 155-78. PMID: 6195816, ISSN: 0042-6822.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/6195816.
  • Privalsky ML, Sealy L, Bishop JM, McGrath JP, Levinson AD. The product of the avian erythroblastosis virus erbB locus is a glycoprotein. Cell. 1983 Apr; 32(4): 1257-67. PMID: 6301688, PII: 0092-8674(83)90307-0, ISSN: 0092-8674.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/6301688.
  • Covault J, Sealy L, Schnell R, Shires A, Chalkley R. Histone hypoacetylation following release of HTC cells from butyrate. J. Biol. Chem. 1982 May 5/25/1982; 257(10): 5809-15. PMID: 6950936, ISSN: 0021-9258.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/6950936.
  • Sealy L, Hartley J, Donelson J, Chalkley R, Hutchison N, Hamkalo B. Characterization of a highly repetitive sequence DNA family in rat. J. Mol. Biol. 1981 Jan 1/15/1981; 145(2): 291-318. PMID: 6167723, PII: 0022-2836(81)90207-2, ISSN: 0022-2836.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/6167723.
  • Sealy L, Chalkley R. Modification of histones immediately following synthesis. Arch. Biochem. Biophys. 1979 Oct 10/1/1979; 197(1): 78-82. PMID: 543725, PII: 0003-9861(79)90221-2, ISSN: 0003-9861.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/543725.
  • Rubenstein P, Sealy L, Marshall S, Chalkley R. Cellular protein synthesis and inhibition of cell division are independent of butyrate-induced histone hyperacetylation. Nature. 1979 Aug 8/23/1979; 280(5724): 692-3. PMID: 471049, ISSN: 0028-0836.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/471049.
  • Moore M, Jackson V, Sealy L, Chalkley R. Comparative studies on highly metabolically active histone acetylation. Biochim. Biophys. Acta. 1979 Jan 1/26/1979; 561(1): 248-60. PMID: 105758, ISSN: 0006-3002.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/105758.
  • Rubenstein, P., Sealy, L., Marshall, S. and Chalkley, R. Cellular Protein Synthesis and Inhibition of Cell Division Appear to be Independent of Butyrate- Induced Histone Hyperacetylation. Nature. 1979; 280: 692-3.
  • Nelson DA, Perry M, Sealy L, Chalkley R. DNAse I preferentially digests chromatin containing hyperacetylated histones. Biochem. Biophys. Res. Commun. 1978 Jun 6/29/1978; 82(4): 1346-53. PMID: 697799, PII: 0006-291X(78)90337-6, ISSN: 0006-291X.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/697799.
  • Sealy L, Chalkley R. DNA associated with hyperacetylated histone is preferentially digested by DNase I. Nucleic Acids Res. 1978 Jun; 5(6): 1863-76. PMID: 673837, PMCID: PMC342130, ISSN: 0305-1048.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/673837.
  • Sealy L, Chalkley R. The effect of sodium butyrate on histone modification. Cell. 1978 May; 14(1): 115-21. PMID: 667928, PII: 0092-8674(78)90306-9, ISSN: 0092-8674.
    Available from: http://www.ncbi.nlm.nih.gov/pubmed/667928.