Dysregulation of mitotic machinery genes precedes genome instability during spontaneous pre-malignant transformation of mouse ovarian surface epithelial cells

Abstract

BackgroundBased 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.ResultsAt 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.ConclusionPrior 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3068-5) contains supplementary material, which is available to authorized users.

Anti-tumour activity of tivozanib, a pan-inhibitor of VEGF receptors, in therapy-resistant ovarian carcinoma cells

“…Exogenous expression of p21, depletion of CCNB1 and shRNA suppression of CDC25C inhibit growth and induce apoptosis63646566. These findings suggest that the cell cycle regulatory network is a promising therapeutic target to halt growth and proliferation of EOC cells6768. In line with this, the results of the present study show that VEGFR blockade by tivozanib retards proliferation of the chemoresistant EOC cells through a G2/M cell cycle arrest via up-regulation of p21 and down-modulation of cyclin B1 and Cdc25C.…”

Membrane Cholesterol Efflux Drives Tumor-Associated Macrophage Reprogramming and Tumor Progression

“…High grade serous ovarian cancer (HGSC) is frequently associated with colonisation of the peritoneal cavity by cancer cells (George et al, 2016). ID8 cells are spontaneously transformed mouse ovarian surface epithelial cells (Urzua et al, 2016), when adoptively transferred by intra-peritoneal (i.p.) injection in syngeneic mice, these cells progressively develop a malignant ascites with tumor nodules throughout the peritoneal cavity (Hagemann et al, 2008), which is characteristic of HGSC.…”

Oxidative stress in female cancers

“…Early culture passages of primary mouse OSE cells experience a subtle pulse of oxidative stress-related gene expression with subsequent mitotic alterations leading to aneuploidies that drive their malignant transformation [ 81 ]. Both OSE cells in ovarian organoids and 2-D cultured MOSE cells show AKT1-mediated DNA damage and increased proliferation upon exposure to hydrogen peroxide [ 82 ].…”

“…In fact, the expression of the epithelial cell marker E-cadherin is high in early ovarian carcinomas and decreases as OC cells progress to advanced stages, thus partially recovering mesenchymal features [ 132 ]. Furthermore, transcriptional profiling data from our laboratory on premalignant mouse OSE cells in culture revealed mitotic anomalies paralleled by overexpression of epithelial genes such as cytokeratins 8 and 18 along with extracellular matrix genes including fibronectin, integrin-beta 1 and the matrix metallopeptidase 2 (MMP-2) [ 81 ]. MMP-2 and MMP-9 are predominantly expressed in pre-neoplastic ovarian lesions than in advanced carcinomas [ 133 ], a finding correlated to loss of epithelial basement membrane in early lesions prior to tumor invasion and metastasis [ 134 ].…”