title: Dysregulation of mitotic machinery genes precedes genome instability during spontaneous pre-malignant transformation of mouse ovarian surface epithelial cells.
abstract: Based in epidemiological evidence, repetitive ovulation has been proposed to play a role in the origin of ovarian cancer by inducing an aberrant wound rupture-repair process of the ovarian surface epithelium (OSE). Accordingly, long term cultures of isolated OSE cells undergo in vitro spontaneous transformation thus developing tumorigenic capacity upon extensive subcultivation. In this work, C57BL/6 mouse OSE (MOSE) cells were cultured up to passage 28 and their RNA and DNA copy number profiles obtained at passages 2, 5, 7, 10, 14, 18, 23, 25 and 28 by means of DNA microarrays. Gene ontology, pathway and network analyses were focused in passages earlier than 20, which is a hallmark of malignancy in this model.
  
  
  
  At passage 14, 101 genes were up-regulated in absence of significant DNA copy number changes. Among these, the top-3 enriched functions (>30 fold, adj p < 0.05) comprised 7 genes coding for centralspindlin, chromosome passenger and minichromosome maintenance protein complexes. The genes Ccnb1 (Cyclin B1), Birc5 (Survivin), Nusap1 and Kif23 were the most recurrent in over a dozen GO terms related to the mitotic process. On the other hand, Pten plus the large non-coding RNAs Malat1 and Neat1 were among the 80 down-regulated genes with mRNA processing, nuclear bodies, ER-stress response and tumor suppression as relevant terms. Interestingly, the earliest discrete segmental aneuploidies arose by passage 18 in chromosomes 7, 10, 11, 13, 15, 17 and 19. By passage 23, when MOSE cells express the malignant phenotype, the dysregulated gene expression repertoire expanded, DNA imbalances enlarged in size and covered additional loci.
  
  
  
  Prior to early aneuploidies, overexpression of genes coding for the mitotic apparatus in passage-14 pre-malignant MOSE cells indicate an increased proliferation rate suggestive of replicative stress. Concomitant down-regulation of nuclear bodies and RNA processing related genes suggests altered control of nuclear RNA maturation, features recently linked to impaired DNA damage response leading to genome instability. These results, combined with cytogenetic analysis by other authors in this model, suggest that transcriptional profile at passage 14 might induce cytokinesis failure by which tetraploid cells approach a near-tetraploid stage containing primary chromosome aberrations that initiate the tumorigenic drive.
authors: Laboratorio de Genómica Aplicada, Programa de Biología Celular y Molecular, ICBM-Facultad de Medicina, Universidad de Chile, Independencia 1027, Santiago, Chile. uurzua@med.uchile.cl.
authors: Ulises
authors: U
authors: Urzúa
authors: Programa de Virología, ICBM-Facultad de Medicina, Universidad de Chile, Independencia 1027, Santiago, Chile.
authors: Sandra
authors: S
authors: Ampuero
authors: Department of Anatomy & Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA.
authors: Katherine F
authors: KF
authors: Roby
authors: Laboratory of Molecular Technology, NCI-SAIC Frederick, Frederick, MD, USA.|Current address: Life Sciences Solutions Group, ThermoFisher Scientific, 5792 Van Allen Way, Carlsbad, CA, 92008, USA.
authors: Garrison A
authors: GA
authors: Owens
authors: Laboratory of Molecular Technology, NCI-SAIC Frederick, Frederick, MD, USA.|Cancer Research Technology Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD, USA.
authors: David J
authors: DJ
authors: Munroe
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D055028:Comparative Genomic Hybridization; D056915:DNA Copy Number Variations; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D053263:Gene Regulatory Networks; D042822:Genomic Instability; D051379:Mice; D008938:Mitosis / Q000235:genetics*; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010053:Ovary / Q000378:metabolism; D010641:Phenotype; D011230:Precancerous Conditions / Q000235:genetics*; D060066:Protein Interaction Maps; D059467:Transcriptome
keywords: Aneuploidy; Cytokinesis; DNA microarrays; Genome; Mouse ovarian surface epithelium; Ovarian cancer model; Preneoplasia; Transcriptome