Nuclear envelope structural defects cause chromosomal numerical instability and aneuploidy in ovarian cancer

Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
BMC Medicine (Impact Factor: 7.25). 03/2011; 9(1):28. DOI: 10.1186/1741-7015-9-28
Source: PubMed


Despite our substantial understanding of molecular mechanisms and gene mutations involved in cancer, the technical approaches for diagnosis and prognosis of cancer are limited. In routine clinical diagnosis of cancer, the procedure is very basic: nuclear morphology is used as a common assessment of the degree of malignancy, and hence acts as a prognostic and predictive indicator of the disease. Furthermore, though the atypical nuclear morphology of cancer cells is believed to be a consequence of oncogenic signaling, the molecular basis remains unclear. Another common characteristic of human cancer is aneuploidy, but the causes and its role in carcinogenesis are not well established.
We investigated the expression of the nuclear envelope proteins lamin A/C in ovarian cancer by immunohistochemistry and studied the consequence of lamin A/C suppression using siRNA in primary human ovarian surface epithelial cells in culture. We used immunofluorescence microscopy to analyze nuclear morphology, flow cytometry to analyze cellular DNA content, and fluorescence in situ hybridization to examine cell ploidy of the lamin A/C-suppressed cells.
We found that nuclear lamina proteins lamin A/C are often absent (47%) in ovarian cancer cells and tissues. Even in lamin A/C-positive ovarian cancer, the expression is heterogeneous within the population of tumor cells. In most cancer cell lines, a significant fraction of the lamin A/C-negative population was observed to intermix with the lamin A/C-positive cells. Down regulation of lamin A/C in non-cancerous primary ovarian surface epithelial cells led to morphological deformation and development of aneuploidy. The aneuploid cells became growth retarded due to a p53-dependent induction of the cell cycle inhibitor p21.
We conclude that the loss of nuclear envelope structural proteins, such as lamin A/C, may underlie two of the hallmarks of cancer--aberrations in nuclear morphology and aneuploidy.

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Available from: Xiang-Xi Xu, Oct 08, 2015
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    • "These activities strongly link the nuclear lamina, including LAP2 proteins, to chromosomal stability in healthy cells. Recently it was shown that NE structural defects due to silencing of lamin A/C proteins caused chromosomal numerical instability and aneuploidy in ovarian cancer [17]. "
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    ABSTRACT: Polyploidy has been recognized for many years as an important hallmark of cancer cells. Polyploid cells can arise through cell fusion, endoreplication and abortive cell cycle. The inner nuclear membrane protein LAP2beta plays key roles in nuclear envelope breakdown and reassembly during mitosis, initiation of replication and transcriptional repression. Here we studied the function of LAP2beta in the maintenance of cell ploidy state, a role which has not yet been assigned to this protein. By knocking down the expression of LAP2beta, using both viral and non-viral RNAi approaches in osteosarcoma derived U2OS cells, we detected enlarged nuclear size, nearly doubling of DNA content and chromosomal duplications, as analyzed by fluorescent in situ hybridization and spectral karyotyping methodologies. Spectral karyotyping analyses revealed that near-hexaploid karyotypes of LAP2beta knocked down cells consisted of not only seven duplicated chromosomal markers, as could be anticipated by genome duplication mechanism, but also of four single chromosomal markers. Furthermore, spectral karyotyping analysis revealed that both of two near-triploid U2OS sub-clones contained the seven markers that were duplicated in LAP2beta knocked down cells, whereas the four single chromosomal markers were detected only in one of them. Gene expression profiling of LAP2beta knocked down cells revealed that up to a third of the genes exhibiting significant changes in their expression are involved in cancer progression. Our results suggest that nuclear fusion mechanism underlies the polyploidization induction upon LAP2beta reduced expression. Our study implies on a novel role of LAP2beta in the maintenance of cell ploidy status. LAP2beta depleted U2OS cells can serve as a model to investigate polyploidy and aneuploidy formation by nuclear fusion mechanism and its involvement in cancerogenesis.
    Molecular Cytogenetics 01/2014; 7(1):9. DOI:10.1186/1755-8166-7-9 · 2.14 Impact Factor
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    • ". (B) les cellules HOSE transfectées par des iARN ayant pour cible l'ARNm de lamine A (HOSE/LAsup), ne possèdent plus de lamine A mais sont polyploïdes (avec 3 à 8 copies de chromosome X), associées à un noyau déformé, parfois multinucléé de grande taille. La méthode de FISH utilisée dans cette figure a été préalablement décrite (Capo-chichi 2011). "
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    ABSTRACT: The lamins are nuclear envelope proteins and main constituent of nuclear lamina surrounding the internal membrane of nuclear envelope. The lamina is the scaffold for nuclear envelope architecture and a framework composed of intermediate filament proteins such as type A and B lamins. Type A lamins (lamin A/C) are encoded by LMNA gene and are at the center of several biological functions essential for cells. Several studies have shown that mutations in LMNA gene are responsible for laminophathies associated with abnormalities in skeletal muscle, in heart, in adipose tissue, bone tissue and neuronal tissue. Lamin A and lamin C are synthesized from the differential splicing of the same messenger RNA but they have different type of maturations. The mutations in LMNA gene affect more often the maturation of lamin A and most of the physiological pathologies are linked to the absence of functional lamin A. Lamin A is a biomarker of differentiated cells and its synthesis is stimulated by vitamin A in embryonic stem cells. The suppressions of lamin A in vivo by endogen épigénétique modifications or in vitro by the interference RNA (iRNA) techniques or enzymatic degradations, reveal the central role of lamin A in the regulation of genes involved in cell division, DNA replication, DNA repair, gene transcription, chromatin organization, cell metabolism, sensitivity to insulin, cell motility, cell signaling, and cell immunity. Epithelial cell that had lost the capacity to express functional lamin A are frequently transformed in cancerous cells while adipose cells that had lost functional lamin A also lack the capacity to metabolize lipids and become resistant to insulin. In this review we emphasize the molecular mechanism involved in cancer genesis, in insulin-resistance and diabetes when the expression of lamin A is altered or lost as well as methods to restore lamins A/C expression.
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    ABSTRACT: Neoplastic cells are often characterized by specific morphological abnormalities of the nuclear envelope (NE), which have been used for cancer diagnosis for more than a century. The NE is a double phospholipid bilayer that encapsulates the nuclear genome, regulates all nuclear trafficking of RNAs and proteins and prevents the passive diffusion of macromolecules between the nucleoplasm and the cytoplasm. Whether there is a consequence to the proper functioning of the cell and loss of structural integrity of the nucleus remains unclear. Using live cell imaging, we characterize a phenomenon wherein nuclei of several proliferating human cancer cell lines become temporarily ruptured during interphase. Strikingly, NE rupturing was associated with the mislocalization of nucleoplasmic and cytoplasmic proteins and, in the most extreme cases, the entrapment of cytoplasmic organelles in the nuclear interior. In addition, we observed the formation of micronuclei-like structures during interphase and the movement of chromatin out of the nuclear space. The frequency of these NE rupturing events was higher in cells in which the nuclear lamina, a network of intermediate filaments providing mechanical support to the NE, was not properly formed. Our data uncover the existence of a NE instability that has the potential to change the genomic landscape of cancer cells.
    Nucleus (Austin, Texas) 01/2012; 3(1):88-100. · 3.03 Impact Factor
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