Article

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

ABSTRACT

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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    • "The method used for IHC analysis was previously described [6] [7] [8] [9]. For GATA6 and lamin A staining, rabbit anti-lamin A and rabbit anti-GATA6 were used conferring to the protocol previously described [6] [7] [8] [9]. GATA6 and lamin A staining were observed with 40X dry objective lens on Nikon Eclipse TE 300 microscope linked to a Roper Scientific Photometrics 12-bit range Camera. "
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    ABSTRACT: BACKGROUND: Cervical cancer is a deadly disease for women worldwide and could be prevented if early molecular screening was performed ahead of cytology. In most neoplastic lesions the expression of nuclear proteins GATA6 and/or lamin A/C is deficient. OBJECTIVE: To analyze GATA6 and lamin A/C in archived cervical epithelial tissues and in cells derived from cervical uterine smears (CUS). METHODS: Immunofluorescence was used to analyze GATA6 and lamin A/C in epithelial cell lines. Immunohistochemistry was used to analyze GATA6 and lamin A/C expression in normal and neoplastic archived cervical tissues. Immunoblotting was used to analyze GATA6 and lamin A/C in cells of CUS obtained freshly from 40 selected women (age 20-45 years) who were attending routine gynecological checkup in Hospital Mènontin (Cotonou, BENIN). Colposcopy was used to visualize the vaginal tract and the uterine-cervix junction. This study is approved by our Institutional Research Ethic Committee and by the Ministry of Health in BENIN. RESULTS: Our data shows that the expression of GATA6 and lamin A/C is altered prior to cervical neoplastic lesions. The nuclear biomarkers GATA6 and lamin A/C are absent in 13% of CUS samples. Colposcopic examination performed after two years on 15 women lacking GATA6 and/or lamin A/C shows that 20% of them have developed cervical neoplastic lesions. CONCLUSION: These preliminary results suggest that the deficiency of GATA6 and lamin A/C in CUS could be used as biomarkers to contribute to the identification of women at risk of developing cervical lesions. However further studies are required for cancer prevention.
    Full-text · Article · Oct 2015
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    • "The method used for IHC analysis was previously described [6] [7] [8] [9]. For GATA6 and lamin A staining, rabbit anti-lamin A and rabbit anti-GATA6 were used conferring to the protocol previously described [6] [7] [8] [9]. GATA6 and lamin A staining were observed with 40X dry objective lens on Nikon Eclipse TE 300 microscope linked to a Roper Scientific Photometrics 12-bit range Camera. "

    Full-text · Article · Oct 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.
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